- Email: [email protected]
Further studies on sultones derived from carbene cyclization cycloaddition cascades
Tetrahedron 71 (2015) 5925e5931
Contents lists available at ScienceDirect
Tetrahedron journal homepage: www.elsevier.com/locate/tet
Further studies on sultones derived from carbene cyclization cycloaddition cascades €ger a, y, Pauline Chiu b, Tobias Groß a, Therese Herrmann a, Bairu Shi a, Anne Ja Peter Metz a, * a b
€t Dresden, Bergstraße 66, 01069 Dresden, Germany Department of Chemistry, Organic Chemistry I, Technische Universita Department of Chemistry and State Key Laboratory of Synthetic Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong
a r t i c l e i n f o
a b s t r a c t
Article history: Received 17 April 2015 Received in revised form 22 May 2015 Accepted 25 May 2015 Available online 29 May 2015
A sulfonyl-stabilized diazoketone underwent an efficient rhodium-catalyzed cascade reaction with an internal vinylsulfonate unit to give a tricyclic sultone as a single diastereomer. Nucleophilic addition of a vinyl Grignard reagent to the ketone of the resultant arylsulfonyl-substituted cycloadduct was stereocomplementary with respect to vinyl Grignard addition to corresponding ester-substituted substrates. The latter tricyclic compounds were chemoselectively transformed into vinylsultones via b-elimination in good yield. Ó 2015 Elsevier Ltd. All rights reserved.
Keywords: Cycloaddition Diazoketones Domino reactions Sulfur heterocycles Transition metal catalysis
1. Introduction Sultones are synthetically useful heterocycles.1,2 Recently, we described an efficient access to g- and d-sultones embedded in a trior tetracyclic framework by rhodium-catalyzed carbene cyclization cycloaddition cascade (CCCC) reactions,3 e.g. of substrates 1 to afford the heterocycles 2 (Scheme 1).4 Similarly, the polycyclic compounds 3 and 4 were readily available from the corresponding vinylsulfonates. While sultones 2 and 3 can serve as building blocks for highly substituted seven-membered carbocycles, sultone 4 embedding the hydroazulene framework is a potential precursor of pseudoguaianolide sesquiterpene lactones.5 For all substrates studied in this context so far, the diazoketone moiety was stabilized by an adjacent ester group (cf. 1). In order to gain enhanced flexibility regarding the synthetic elaboration of the polycyclic cycloadducts, we were interested in the reactivity of a corresponding non-stabilized diazoketone (1 with H instead of CO2Et). Furthermore, we decided to explore an alternative stabilizing substituent that might be replaced by a hydrogen atom after the CCCC process. Herein we report our investigations along these
* Corresponding author. Tel.: þ49 351 463 37006; fax: þ49 351 463 33162; e-mail address: [email protected] (P. Metz). y Author responsible for X-ray diffraction analyses. http://dx.doi.org/10.1016/j.tet.2015.05.095 0040-4020/Ó 2015 Elsevier Ltd. All rights reserved.
Scheme 1. Sultones 2e4 prepared by rhodium-catalyzed carbene cyclization cycloaddition cascade (CCCC) reactions of vinylsulfonates.
lines as well as toward the structural modification of sultones such as 2. 2. Results and discussion At first, we set out to prepare the vinylsulfonate of the polyfunctional diazoketone 10 (Scheme 2). Similar to the synthesis of 1 (R1¼R2¼H),4 we departed from ethyl glycolate (5) that was transformed into the Weinreb amide 6 via the known triethylsilyl (TES) ether6 of hydroxy ester 5. Homologation of 6 with Normant’s Grignard reagent7 and subsequent oxidation with o-iodoxybenzoic
5926
T. Groß et al. / Tetrahedron 71 (2015) 5925e5931
acid (IBX)8 yielded keto aldehyde 7. Conversion of 7 to 9 proceeded uneventfully by sodium chlorite oxidation9 to give 8 followed by standard generation of the diazoketone function.10 Gratifyingly, subjecting TES ether 9 to acetic acid in THF/water11 led to the sensitive alcohol 10 in high yield, whereas deblocking of the tbutyldimethylsilyl (TBS) analog of 9 prepared from 5 in a corresponding fashion could not be achieved without substantial destruction of the non-stabilized diazoketone unit. Unfortunately, however, all attempts to convert 10 to the corresponding vinylsulfonate met with failure, and only the known chloride 1212 was isolated from treatment of 10 with vinylsulfonyl chloride (11).13
Scheme 3. Preparation of sulfone-stabilized diazoketone 18 and CCCC reaction to give sultone 20. Reagents and conditions: (a) 14, 20 mol % SnCl2, CH2Cl2, 0 C to rt, 69%; (b) TfN3, 9 mol % Bu4NI, 10 mol % Et3N, MeCN, 0 C to rt, 95%; (c) aq HF, MeCN, rt, 84%; (d) 11, Et3N, CH2Cl2, 20 C, 65% 18, 18% 19; (e) 3 mol % Rh2(oct)4, CH2Cl2, rt, 76%.
Scheme 2. Preparation of diazoketone 10 and attempted vinylsulfonate formation. Reagents and conditions: (a) TESCl, imidazole, DMF, rt; (b) HN(OMe)Me∙HCl, i-PrMgCl, THF, 18 C, 67% (2 steps); (c) ClMg(CH2)3OMgCl, THF, 78 C; (d) IBX, ethyl acetate, reflux, 68% (2 steps); (e) NaClO2, NaH2PO4, 2-methylbut-2-ene, t-BuOH, H2O, rt, 75%; (f) i. i-BuOCOCl, Et3N, Et2O, rt, ii. CH2N2, Et2O, 78 Ce0 C, 51%; (g) HOAc, THF, H2O, 0 C, 94%; (h) 11, Et3N, CH2Cl2, 20 C, 10%.
We then turned our attention to the utilization of an electronwithdrawing sulfone as a stabilizing moiety for the diazoketone unit. The p-toluenesulfonyl (SO2Tol) substituted alcohol 17 was chosen as our primary target, since a range of methods for reductive removal of this arylsulfonyl group is available (Scheme 3).14 Tin(II)-catalyzed reaction15 of aldehyde 134 with p-tosyldiazomethane (14)16 furnished the b-ketosulfone 15 in good yield. Diazo transfer of 15 to give 16 was highly efficient using triflyl azide17 in the presence of catalytic amounts of triethylamine and tetrabutylammonium iodide, whereas the use of tosyl azide4 only afforded a 44% yield of 16. In contrast to the behavior of the TBS analog of 9, desilylation of 16 to give alcohol 17 was easily achieved with hydrofluoric acid in acetonitrile. Sulfonylation of 17 with vinylsulfonyl chloride (11) at 20 C was crucial for securing a good yield of the cycloaddition substrate 18. Under these conditions, nucleophilic substitution of 18 to give the chloride 19 is largely suppressed, while 19 is formed as the major product at 0 C. Gratifyingly, the key CCCC reaction of 18 provided sultone 20 as a single diastereomer in 76% yield after 30 min at room temperature when 3 mol % of rhodium(II) octanoate (Rh2(oct)4) was used as the catalyst. With Rh2(OAc)4 (3 mol %, CH2Cl2, rt), 20 was isolated in only 37% yield after 19 h, and treatment of 18 with rhodium(II) trifluoroacetate (3 mol %) or copper(II) acetylacetonate (10 mol %) led to unattractive mixtures. The relative configuration of sultone 20 was determined by 2D NMR experiments and confirmed by Xray diffraction analysis (Fig. 1). With the sultones 20 and 22a,b4 in our hands, we investigated the effect of the different substituents a to the ketone on the diastereoselectivity of a nucleophilic addition to this carbonyl group
Fig. 1. Crystal structure of sultone 20.18,19
(Scheme 4). Reaction of vinylmagnesium bromide with the sulfonyl substituted tricycle 20 yielded solely the allylic alcohol 21 via exo attack of the Grignard reagent. The relative configuration of 21 was unequivocally determined by X-ray diffraction analysis (Fig. 2). In striking contrast, transformation of the ester substituted tricycles 22a,b with a vinyl Grignard reagent afforded only the diastereomers 23a,b, where endo nucleophilic addition took place. Precoordination of the organomagnesium halide to the ester group might account for this complete reversal of diastereoselectivity. The
Scheme 4. Diastereoselective addition of vinyl Grignard reagents to sultones 20 and 22. Reagents and conditions: (a) vinylmagnesium bromide, THF, 0 C, 75%; (b) vinylmagnesium chloride, THF, 0 C, 84% 23a, 87% 23b.
T. Groß et al. / Tetrahedron 71 (2015) 5925e5931
Fig. 2. Crystal structure of sultone 21.18,19
relative configuration of 23a and 23b was unambiguously assigned on the basis of a strong NOE between the two protons depicted in Scheme 4. Some orientating experiments towards cleavage of the oxygen bridge in the tricyclic CCCC adducts by b-elimination were performed with sultones 23a,b (Scheme 5).20 First attempts to induce this process by abstraction of the acidic proton a to the sulfonyl group with lithium diisopropylamide21 only gave low yields of the desired products 24a (30%) and 24b (35%). Likewise, t-butyllithium did not give satisfactory results. However, the use of 2 equiv of methyllithium22 at 78 C allowed a chemoselective opening of the oxygen bridge to give the vinylsultones 24a,b rather efficiently within 15 min already.
Scheme 5. Opening of the oxygen bridge of sultones 23 by b-elimination.
3. Conclusion In summary, the scope of the rhodium-catalyzed carbene cyclization cycloaddition cascade reaction of vinylsulfonates to give polycyclic sultones has been extended to include a sulfonylstabilized diazoketone. The p-toluenesulfonyl substituent of the resultant cycloadduct effected a complete reversal of diastereoselectivity of nucleophilic addition to the ketone as compared to corresponding ester-substituted substrates. The latter tricyclic compounds were chemoselectively transformed into vinylsultones, which now offer further options for synthetic elaboration, e.g. via reductive desulfurization.23
4. Experimental section 4.1. General information All reactions requiring the exclusion of moisture were run under argon using heat-gun-dried flasks. Et2O, THF, and CH2Cl2 were dried with molecular sieves using an MBRAUN MB-SPS-800 device. Flash chromatography was carried out on Merck silica gel 60 (40e63 mm). Thin layer chromatography was carried out on Merck silica gel 60 F254 plates. Melting points were measured with a Wagner & Munz PolyTherm A device. FTIR spectra were recorded with a Nicolet Avatar 360 spectrometer. 1H and 13C NMR spectra were recorded with Bruker instruments: AC-300-P (1H 300 MHz, 13 C 75 MHz), DRX-500-P (1H 500 MHz, 13C 125 MHz), and Avance-
5927
III-600 (1H 600 MHz, 13C 150 MHz). Chemical shifts (d) are quoted in parts per million (ppm) downfield of tetramethylsilane, using residual proton-containing solvent as internal standard (CDCl3 at d¼7.27 ppm and d¼77.0 ppm, respectively). Abbreviations used in the description of resonances are: s (singlet), d (doublet), t (triplet), q (quartet), m (multiplet), br. (broad). Coupling constants (J) are quoted to the nearest 0.1 Hz. The multiplicities of the 13C NMR signals were determined using DEPT spectra. Mass spectra were recorded with an Agilent 5973N detector coupled with an Agilent 6890N GC (GCeMS, 70 eV) and a Bruker Esquire LC (LC/MS, ESI). High-resolution mass spectrometry (HRMS) was carried out with a Finnigan MAT 95 (EI, 70 eV) instrument. Elemental analysis was performed using a Hekatech EA 3000 instrument. X-ray analyses were carried out with a Bruker Kappa CCD diffractometer. 4.2. Weinreb amide 6 Hydroxy ester 5 (1.67 g, 16.0 mmol) was dissolved in dichloromethane (30 mL), and triethylchlorosilane (2.89 g, 19.2 mmol) and imidazole (1.31 g, 19.2 mmol) were added. The solution was stirred at room temperature for 10 h. The precipitate formed was removed by filtration over silica gel (elution with diethyl ether). After evaporation of the solvent, the crude silyl ether6 (3.50 g) was used for the next reaction. To a solution of N,O-dimethylhydroxylamine hydrochloride (5.50 g, 56 mmol) in THF (30 mL) cooled to 18 C was dropwise added a solution of i-propylmagnesium chloride (2M in THF, 48 mL, 96 mmol). After stirring at this temperature for 2.5 h, a solution of the crude silyl ether (3.50 g) in THF (30 mL) was added slowly, and stirring was continued for 4 h. A saturated solution of ammonium chloride (100 mL) was added, the layers were separated, and the aqueous layer was extracted with ethyl acetate. After drying the organic layer over magnesium sulfate, the crude product was purified by flash chromatography (pentane/ethyl acetate, 4:1) to give the Weinreb amide 6 (2.50 g, 67% over two steps) as a colorless oil; Rf 0.40 (pentane/ethyl acetate, 4:1); IR (ATR): nmax 2954, 2911, 2876, 1693, 1460, 1442, 1414, 1390, 1329, 1238, 1155, 1086, 995, 805, 769, 727, 673 cm1; 1H NMR (300 MHz, CDCl3) d 0.66 (q, J¼7.9 Hz, 6H), 0.98 (t, J¼7.9 Hz, 9H), 3.18 (s, 3H), 3.67 (s, 3H), 4.41 (s, 2H); 13C NMR (75 MHz, CDCl3) d 4.4 (CH2), 6.7 (CH3), 32.5 (CH3), 61.4 (CH3), 61.4 (CH2), the carbonyl carbon was not detected due to the quadrupole relaxation of nitrogen; GCeMS (EI): m/z (%)¼205 (15), 204 (100) [MC2H5]þ, 144 (12), 117 (16), 103 (2), 88 (11), 87 (11), 75 (4), 59 (12). Anal. calcd for C10H23NO3Si: C, 51.46; H, 9.93; N, 6.00. Found: C, 51.54; H, 9.86; N, 6.17. 4.3. Keto aldehyde 7 A solution of i-propylmagnesium chloride (2 M, 13 mL, 26 mmol) was diluted with THF (10 mL) and cooled in an ice bath. 3-Chloro-1-propanol (2 mL, 23.9 mmol) dissolved in THF (10 mL) was added over 10 min, and the resultant mixture was stirred for 1 h. The light brown solution decolorized almost completely. In a second flask equipped with a reflux condenser, magnesium turnings (1.00 g, 41.1 mmol) were added to THF (5 mL). After activation with dibromoethane (0.1 mL), the mixture was heated to reflux for 10 min. Then the magnesium alkoxide solution prepared as described above was added, and the mixture was refluxed for 3 h and cooled to room temperature. This solution was added to a solution of Weinreb amide 6 (2.41 g, 10.3 mmol) in THF (20 mL) cooled to 78 C. The mixture was stirred overnight (17 h), while the cooling bath was allowed to warm to room temperature. Then a saturated solution of ammonium chloride was added, the layers were separated, and the aqueous layer was extracted with ethyl acetate. After washing with brine and drying the organic layer over magnesium sulfate, the solvents were evaporated, and the crude keto alcohol (2.92 g) was used for the next step. To a solution of this
5928
T. Groß et al. / Tetrahedron 71 (2015) 5925e5931
crude keto alcohol (2.92 g) in ethyl acetate (50 mL) was added IBX (4.50 g, 16.0 mmol). The resultant mixture was heated to reflux for 8 h. After cooling and filtration over silica gel (elution with diethyl ether), the solvents were removed in vacuo, and the crude product was purified by flash chromatography (dichloromethane/diethyl ether, 9:1) to give the keto aldehyde 7 (1.55 g, 68% over two steps) as a colorless oil; Rf 0.60 (dichloromethane/diethyl ether, 9:1); IR (ATR): nmax 2955, 2911, 2878, 2833, 2725, 1723, 1408, 1357, 1239, 1160, 1101, 1008, 789, 742, 537 cm1; 1H NMR (300 MHz, CDCl3) d 0.64 (q, J¼7.9 Hz, 6H), 0.97 (t, J¼7.9 Hz, 9H), 2.79e2.93 (m, 4H), 4.23 (s, 2H), 9.81 (s, 1H); 13C NMR (75 MHz, CDCl3) d 4.3 (CH2), 6.6 (CH3), 30.7 (CH2), 37.0 (CH2), 68.9 (CH2), 200.4 (CH), 209.3 (C); GCeMS (EI): m/z (%)¼201 (31) [MC2H5]þ, 183 (10), 159 (25), 158 (16), 157 (100), 129 (33), 117 (19), 115 (18), 103 (23), 87 (23), 75 (19), 59 (23), 58 (11), 55 (11), 47 (7). Anal. calcd for C11H22O3Si: C, 57.35; H, 9.63. Found: C, 57.28; H, 9.57. 4.4. Carboxylic acid 8 Aldehyde 7 (1.40 g, 6.10 mmol) was dissolved in t-butanol (20 mL) at room temperature. 2-Methylbut-2-ene (4.20 mL, 48.6 mmol) and then a mixture of sodium chlorite (80%, 4.12 g, 30.8 mmol) and sodium dihydrogen phosphate (5.45 g, 39.5 mmol) in water (35 mL) were added, whereupon the reaction mixture turned yellow. After stirring for 45 min, the resultant colorless solution was extracted with ethyl acetate. The combined organic layers were washed with brine and dried over magnesium sulfate. After filtration, the crude product was concentrated in vacuo and purified by flash chromatography (pentane/ethyl acetate, 2:1) to give carboxylic acid 8 (1.12 g, 75%) as a yellow oil; Rf 0.17 (pentane/ethyl acetate, 2:1); IR (ATR): nmax 3050, 2956, 2913, 2878, 1724, 1711, 1411, 1240, 1159, 1102, 1006, 817, 743 cm1; 1H NMR (300 MHz, CDCl3) d 0.63 (q, J¼7.9 Hz, 6H), 0.96 (t, J¼7.9 Hz, 9H), 2.67 (t, J¼6.0 Hz, 2H), 2.82 (t, J¼6.0 Hz, 2H), 4.20 (s, 2H); 13C NMR (75 MHz, CDCl3) d 4.3 (CH2), 6.6 (CH3), 27.3 (CH2), 32.9 (CH2), 68.8 (CH2), 178.0 (C), 209.3 (C); GCeMS (EI): m/z (%)¼217 (31) [MC2H5]þ, 199 (5), 171 (72), 157 (100), 129 (14), 115 (13), 113 (13), 103 (13), 101 (12), 87 (18), 75 (19), 59 (18), 58 (11), 56 (12), 47 (5), 45 (12). Anal. calcd for C11H22O4Si: C, 53.62; H, 9.00. Found: C, 53.78; H, 9.21. 4.5. Diazoketone 9 To a solution of carboxylic acid 8 (250 mg, 1.02 mmol) in diethyl ether (7.5 mL) was added i-butyl chloroformate (178 mg, 1.30 mmol) and triethylamine (147 mg, 1.45 mmol) at room temperature. After stirring the mixture for 36 h, the precipitate formed was removed by filtration and eluted with some diethyl ether. Diazomethane was synthesized according to a reported procedure24 using DiazaldÒ (2.50 g, 11.5 mmol) dissolved in diethyl ether (20 mL). The reaction vessel was loaded with water (2.0 mL), diethyl ether (4.0 mL), and 2-(2-ethoxyethoxy)ethanol (7.0 mL). The condenser was cooled to78 C, and diazomethane in diethyl ether was collected at 20 C. This solution was covered with argon and dried over potassium hydroxide at 0 C for 1 h and at 78 C for 2 h. Then it was added to the cooled (78 C) mixed anhydride solution prepared from 8 as described above. The resulting mixture was stirred for 24 h, while the cooling bath was allowed to warm to 0 C. Argon was bubbled through the solution for 1 h, and acetic acid was added in order to remove excess diazomethane. After extraction with diethyl ether, washing with brine, drying over magnesium sulfate, and filtration, the solvent was removed in vacuo. The crude product was purified by flash chromatography (pentane/ethyl acetate, 2:1) to afford diazoketone 9 (141 mg, 51%) as a yellow oil; Rf 0.45 (pentane/ethyl acetate, 2:1); IR (ATR): nmax 3090, 2955, 2912, 2877, 2100, 1724, 1642, 1377, 1346, 1319, 1152, 1098, 1062, 1004, 809, 728 cm1; 1H NMR (300 MHz, CDCl3) d 0.63
(q, J¼8.0 Hz, 6H), 0.97 (t, J¼8.0 Hz, 9H), 2.56e2.66 (br s, 2H), 2.87 (t, J¼6.5 Hz, 2H), 4.22 (s, 2H), 5.23e5.86 (br s, 1H); 13C NMR (125 MHz, CDCl3) d 4.2 (CH2), 6.6 (CH3), 32.9 (CH2), 33.5 (CH2), 54.5 (CH), 68.9 (CH2), 193.2 (C), 209.6 (C); GCeMS (EI): m/z (%)¼214 (12), 213 (100) [MN2C2H5]þ, 171 (66), 129 (13), 127 (10), 115 (10), 113 (10), 103 (12), 99 (10), 87 (13), 75 (22), 59 (12), 47 (10). HRMS (EI): m/z calcd for C10H17N2O3Si ([MC2H5]þ) 241.1008; found 241.1009. 4.6. Desilylation of diazoketone 9 To a solution of diazoketone 9 (50.0 mg, 0.18 mmol) in THF (2.5 mL) cooled to 0 C was added water (0.5 mL) and acetic acid (0.5 mL). After stirring for 7 h at 0 C, the mixture was treated with saturated aqueous ammonium chloride solution and extracted with ethyl acetate. The combined organic layers were dried over sodium sulfate, and the solvent was removed in vacuo. The crude product was purified by flash chromatography (ethyl acetate) to afford diazoketone 10 (27.2 mg, 94%) as a yellow oil; Rf 0.22 (ethyl acetate); IR (ATR): nmax 3422, 3372, 3068, 2916, 2864, 2104, 1717, 1633, 1381, 1341, 1142, 1050, 994, 644, 592, 574 cm1; 1H NMR (300 MHz, CDCl3) d 2.73 (br s, 4H), 2.98 (t, J¼4.9 Hz, 1H, OH), 4.33 (d, J¼4.9 Hz, 2H), 5.37 (br s, 1H); 13C NMR (75 MHz, CDCl3) d 32.3 (CH2), 33.7 (CH2), 54.7 (CH), 68.2 (CH2), 192.5 (C), 208.5 (C); GCeMS (EI): m/z (%)¼157 (3) [MþH]þ, 126 (9), 125 (100), 98 (16), 69 (13), 55 (97), 43 (13), 41 (19), 39 (12), 31 (29), 28 (10), 27 (22). HRMS (EI): m/z calcd for C6H9N2O3 ([MþH]þ) 157.0613; found 157.0605. 4.7. Attempted vinylsulfonate formation with alcohol 10 Triethylamine (60 mL, 0.423 mmol) was added to a solution of diazoketone 10 (60.1 mg, 0.38 mmol) in dichloromethane (6 mL) cooled to 20 C. Then a solution of ice-cold vinylsulfonyl chloride (11, 53.5 mg, 0.423 mmol) in dichloromethane (5 mL) was added dropwise. The resultant mixture was stirred for 15 min and then quickly filtered over silica gel (elution with ice-cold dichloromethane). After removal of the solvent in vacuo, the residue was subjected to flash chromatography (dichloromethane/diethyl ether, 2:1) to give chloride 1212 (12.0 mg, 10%) as a yellow oil. A second product, presumably the desired vinylsulfonate, was visible on TLC at Rf 0.44 (dichloromethane/diethyl ether, 2:1). However, this compound decomposed after evaporation of the solvent. 12: Rf 0.63 (dichloromethane/diethyl ether, 2:1); IR (ATR): nmax 3102, 2935, 2101, 1731, 1627, 1378, 1318, 1132, 1066, 771, 549 cm1; 1H NMR (300 MHz, CDCl3) d 2.67e2.73 (m, 2H), 2.92 (t, J¼6.3 Hz, 2H), 4.17 (s, 2H), 5.31 (br s, 1H); 13C NMR (75 MHz, CDCl3) d 33.9 (CH2), 34.1 (CH2), 48.2 (CH2), 54.7 (C), 192.6 (C), 210.5 (C); LC-MS (ESI): m/z 174.9 [MþH]þ, 370.9 [2MþNa]þ. 4.8. Diketo sulfone 15 Tin(II) chloride (24.7 mg, 0.130 mmol) and p-tosyldiazomethane16 (14, 307 mg, 1.56 mmol) were added to a solution of aldehyde 134 (150 mg, 0.650 mmol) in dichloromethane (0.4 mL) cooled to 0 C. The mixture was stirred for 10 min at 0 C and for 5.5 h at room temperature. After filtration over silica gel (elution with ethyl acetate) to remove the tin salt and concentration in vacuo, the crude product was purified by flash chromatography (pentane/diethyl ether, 1:1 to 1:3) to afford diketo sulfone 15 (180 mg, 69%) as a yellow oil; Rf 0.45 (pentane/diethyl ether, 1:3); IR (ATR): nmax 3427, 2997, 2936, 2860, 1713, 1393, 1305, 1292, 1183, 1141, 1084, 1043, 993, 816, 801, 741, 674 cm1; 1H NMR (300 MHz, CDCl3) d 0.08 (s, 6H), 0.92 (s, 9H), 2.45 (s, 3H), 2.77e2.83 (m, 2H), 2.96e3.02 (m, 2H), 4.18 (s, 2H), 4.21 (s, 2H), 7.36 (d, J¼8.2 Hz, 2H), 7.78 (d, J¼8.2 Hz, 2H); 13C NMR (75 MHz, CDCl3) d 5.6 (CH3), 18.2 (C), 21.7 (CH3), 25.7 (CH3), 32.4 (CH2), 37.3 (CH2), 67.3 (CH2), 69.1 (CH2), 128.3 (CH), 130.0 (CH), 135.7 (C), 145.4 (C), 197.1 (C), 209.1 (C);
T. Groß et al. / Tetrahedron 71 (2015) 5925e5931
GCeMS (EI): m/z (%)¼341 (20) [MC4H9]þ, 324 (10), 323 (44), 249 (25), 213 (17), 185 (51), 167 (10), 155 (18), 149 (14), 139 (11), 130 (10.4), 129 (100), 91 (30), 89 (11), 81 (10), 75 (21), 73 (30); LC-MS (ESI): m/z 399.1 [MþH]þ, 416.1 [MþNH4]þ. HRMS (EI): m/z calcd for C15H21O5SSi ([MC4H9]þ) 341.0879; found 341.0891. 4.9. Diazoketone 16 To a solution of diketo sulfone 15 (1.10 g, 2.76 mmol) and tetrabutylammonium iodide (0.09 g, 0.25 mmol) in acetonitrile (10 mL) cooled to 0 C was added trifluoromethanesulfonyl azide (0.5M in hexane, 12 mL, 6 mmol) and triethylamine in acetonitrile (1:10 v/v, 37.5 mL, 0.27 mmol). Conversion was complete after stirring for 2.5 h, while allowing the mixture to warm to room temperature. After filtration over silica gel (elution with diethyl ether) and concentration in vacuo, the crude product was purified by flash chromatography (pentane/diethyl ether, 1:2) to yield diazoketone 16 (1.12 g, 95%) as a yellow oil; Rf 0.73 (pentane/diethyl ether, 1:2); IR (ATR): nmax 3478, 2950, 2929, 2858, 2125, 1722, 1651, 1330, 1186, 1147, 1119, 1083, 1067, 1034, 988, 838, 814, 706, 666, 590, 562 cm1; 1H NMR (300 MHz, CDCl3) d 0.07 (s, 6H), 0.90 (s, 9H), 2.46 (s, 3H), 2.79e2.90 (m, 4H), 4.17 (s, 2H), 7.37 (d, J¼8.3 Hz, 2H), 7.87 (d, J¼8.3 Hz, 2H); 13C NMR (75 MHz, CDCl3) d 5.6 (CH3), 18.2 (C), 21.7 (CH3), 25.7 (CH3), 32.1 (CH2), 32.5 (CH2), 69.1 (CH2), 127.3 (CH), 130.1 (CH), 139.1 (C), 145.4 (C), 187.2 (C), 209.0 (C), the carbon directly attached to the diazo group was not detected due to the quadrupole relaxation of nitrogen; LC-MS (ESI): m/z 425.1 [MþH]þ, 442.1 [MþNH4]þ. Anal. calcd for C19H28N2O5SSi: C, 53.75; H, 6.65; N, 6.60; S, 7.55. Found: C, 53.69; H, 6.37; N, 6.71; S, 7.72. 4.10. Desilylation of diazoketone 16 to give alcohol 17 Diazoketone 16 (33.0 mg, 0.078 mmol) was dissolved in acetonitrile/aqueous hydrofluoric acid (40%) (95:5 v/v, 5.2 mL). After stirring at room temperature for 1 h, the mixture was diluted with water and extracted with dichloromethane. The combined organic layers were dried over magnesium sulfate, filtered, and evaporated. Purification of the residue by flash chromatography (diethyl ether) gave alcohol 17 (20.3 mg, 84%) as a yellow solid; Rf 0.16 (diethyl ether); mp 94e96 C (decomposition); IR (ATR): nmax 3451, 3090, 3049, 2926, 2851, 2110, 2057, 1703, 1672, 1596, 1402, 1329, 1314, 1224, 1175, 1149, 1085, 1011, 818, 676, 652, 586, 545 cm1; 1H NMR (300 MHz, CDCl3) d 2.47 (s, 3H), 2.68 (t, J¼6.1 Hz, 2H), 2.98 (t, J¼6.1 Hz, 2H), 2.80 (br s, 1H, OH), 4.29 (s, 2H), 7.39 (d, J¼8.4 Hz, 2H), 7.86 (d, J¼8.4 Hz, 2H); 13C NMR (75 MHz, CDCl3) d 21.7 (CH3), 31.6 (CH2), 32.8 (CH2), 68.1 (CH2), 127.3 (CH), 130.2 (CH), 139.0 (C), 145.6 (C), 186.9 (C), 207.7 (C), the carbon directly attached to the diazo group was not detected due to the quadrupole relaxation of nitrogen; LC-MS (ESI): m/z 311.0 [MþH]þ, 328.1 [MþNH4]þ. HRMS (EI): m/z calcd for C12H11N2O4S ([MCH2OH]þ) 279.0440; found 279.0433. 4.11. Vinylsulfonate formation with alcohol 17 Ice-cold vinylsulfonyl chloride (11, 76.0 mg, 0.60 mmol) was slowly added to a solution of alcohol 17 (178.0 mg, 0.574 mmol) and triethylamine (84 mL, 0.60 mmol) in dichloromethane (5 mL) cooled to 20 C. The mixture was stirred at 20 C for 20 min and then quickly filtered over silica gel (elution with ice-cold dichloromethane). After evaporation of the solvent in vacuo, the residue was subjected to flash chromatography (dichloromethane/diethyl ether, 2:1) to give vinylsulfonate 18 (149.3 mg, 65%) as a yellow oil and chloride 19 (33.9 mg, 18%) as a yellow solid. 18: Rf 0.67 (dichloromethane/diethyl ether, 2:1); IR (ATR): nmax 3064, 2925, 2114, 1738, 1660, 1595, 1361, 1331, 1170, 1148, 983, 797, 665, 589 cm1; 1H NMR (500 MHz, CDCl3) d 2.48 (s, 3H), 2.78 (m,
5929
2H), 2.95 (m, 2H), 4.69 (s, 2H), 6.17 (d, J¼10.1 Hz, 1H), 6.45 (d, J¼16.7 Hz, 1H), 6.63 (dd, J¼16.7, 10.1 Hz, 1H), 7.40 (d, J¼8.5 Hz, 2H), 7.86 (d, J¼8.5 Hz, 2H); 13C NMR (125 MHz, CDCl3) d 21.7 (CH3), 32.2 (CH2), 32.7 (CH2), 71.8 (CH2), 127.2 (CH), 130.2 (CH), 131.0 (CH2), 132.2 (CH), 139.0 (C), 145.6 (C), 186.7 (C), 201.1 (C), the carbon directly attached to the diazo group was not detected due to the quadrupole relaxation of nitrogen; LC-MS (ESI): m/z 418.1 [MþNH4]þ, 823.0 [2MþNa]þ. HRMS (EI): m/z calcd for C15H16O7S2 ([MN2]þ) 372.0337; found 372.0331. Anal. calcd for C15H16N2O7S2: C, 44.99; H, 4.03; N, 7.00. Found: C, 45.06; H, 3.64; N, 6.62. 19: Rf 0.80 (dichloromethane/diethyl ether, 2:1); mp 79e80 C; IR (ATR): nmax 3054, 2923, 2103, 1729, 1677, 1595, 1403, 1324, 1230, 1176, 1147, 1084, 817, 748, 666, 583 cm1; 1H NMR (300 MHz, CDCl3) d 2.49 (s, 3H), 2.80e3.02 (m, 4H), 4.14 (s, 2H), 7.40 (d, J¼8.3 Hz, 2H), 7.86 (d, J¼8.3 Hz, 2H); 13C NMR (125 MHz, CDCl3) d 21.7 (CH3), 33.1 (CH2), 33.2 (CH2), 48.1 (CH2), 127.2 (CH), 130.2 (CH), 139.0 (C), 145.6 (C), 186.9 (C), 201.0 (C), the carbon directly attached to the diazo group was not detected due to the quadrupole relaxation of nitrogen; LC-MS (ESI): m/z 329.0 [MþH]þ, 346.1 [MþNH4]þ. 4.12. CCCC reaction to afford sultone 20 To a solution of vinylsulfonate 18 (65.0 mg, 0.16 mmol) in dichloromethane (6 mL) was added Rh2(oct)4 (3.7 mg, 4.8 mmol, 3 mol %). The reaction mixture was stirred at room temperature for 30 min. Gas evolution was observed. After removal of the solvent in vacuo, the residue was purified by flash chromatography (dichloromethane/diethyl ether, 2:1) to yield sultone 20 (45.1 mg, 76%) as a white solid; Rf 0.23 (dichloromethane/diethyl ether, 2:1); mp 230e231 C; IR (ATR): nmax 2987, 1734, 1599, 1452, 1357, 1180, 1151, 1050, 949, 792, 685, 663, 570 cm1; 1H NMR (600 MHz, CDCl3) d 2.12 (ddd, J¼13.9, 8.3, 5.6 Hz, 1H), 2.40 (ddd, J¼13.9, 10.1, 5.6 Hz, 1H), 2.48 (s, 3H), 2.55 (ddd, J¼16.8, 8.3, 5.6 Hz, 1H), 2.71 (ddd, J¼16.8, 10.1, 5.6 Hz, 1H), 2.88 (dd, J¼14.3, 9.4 Hz, 1H), 3.07 (dd, J¼14.3, 6.0 Hz, 1H), 3.68 (dd, J¼9.4, 6.0 Hz, 1H), 4.25 (d, J¼10.9 Hz, 1H), 4.52 (d, J¼10.9 Hz, 1H), 7.38 (d, J¼7.9 Hz, 2H), 7.86 (d, J¼7.9 Hz, 2H); 13C NMR (150 MHz, CDCl3) d 21.8 (CH3), 28.9 (CH2), 34.3 (CH2), 35.8 (CH2), 62.1 (CH), 70.1 (CH2), 92.0 (C), 99.7 (C), 129.7 (CH), 130.7 (CH), 131.5 (C), 146.5 (C), 199.1 (C); GCeMS (EI): m/z (%)¼372 (15) [M]þ, 269 (8), 217 (9), 198 (11), 155 (9), 139 (100), 125 (11), 107 (22), 91 (51), 81 (35), 79 (32), 65 (37), 53 (21), 41 (24); LC-MS (ESI): m/z 390.1 [MþNH4]þ, 761.9 [2MþNH4]þ, 767.0 [2MþNa]þ. HRMS (EI): m/z calcd for C15H16O7S2 ([M]þ) 372.0337; found 372.0342. Anal. calcd for C15H16O7S2: C, 48.38; H, 4.33. Found: C, 48.65; H, 4.50. 4.13. Grignard addition to give sultone 21 Vinylmagnesium bromide (0.01M in THF, 310 mL, 0.031 mmol) was added to a solution of sultone 20 (10.2 mg, 0.027 mmol) in THF (1.7 mL) at 0 C. After stirring for 2 h at 0 C, saturated ammonium chloride solution (1 mL) was added, and the mixture was extracted three times with dichloromethane. The combined organic extracts were washed with brine, dried over magnesium sulfate and concentrated in vacuo. The crude product was purified by flash chromatography (dichloromethane/diethyl ether, 2:1) to give sultone 21 (8.2 mg, 75%) as a white solid; Rf 0.52 (dichloromethane/diethyl ether, 2:1); mp 240e241 C; IR (ATR): nmax 3519, 3028, 2922, 2853, 1597, 1454, 1353, 1287, 1154, 1076, 997, 943, 802, 736, 716, 660 cm1; 1H NMR (500 MHz, CDCl3) d 1.76e2.01 (m, 4H), 2.48 (s, 3H), 2.75 (dd, J¼14.8, 3.8 Hz, 1H), 3.26 (dd, J¼14.8, 9.8 Hz, 1H), 3.66 (dd, J¼9.8, 3.8 Hz, 1H), 3.70 (s, 1H, OH), 4.20 (d, J¼11.0 Hz, 1H), 4.52 (d, J¼11.0 Hz, 1H), 5.32 (dd, J¼10.9, 0.8 Hz, 1H), 5.61 (dd, J¼17.2, 0.8 Hz, 1H), 6.63 (dd, J¼17.2, 10.9 Hz, 1H), 7.38 (d, J¼8.2 Hz, 2H), 7.77 (d, J¼8.2 Hz, 2H); 13C NMR (125 MHz, CDCl3) d 21.8 (CH3), 28.1 (CH2), 33.0 (CH2), 36.3 (CH2), 62.5 (CH), 70.6 (CH2), 73.5 (C), 93.6 (C), 101.9 (C), 114.6 (CH2), 129.8 (CH), 130.4 (CH), 131.5 (C), 137.6
5930
T. Groß et al. / Tetrahedron 71 (2015) 5925e5931
(CH), 146.2 (C); LC-MS (ESI): m/z 418.1 [MþNH4]þ, 423.2 [MþNa]þ. HRMS (EI): m/z calcd for C15H16O7S2 ([MþH]þ) 401.0739; found 401.0733. 4.14. Grignard addition to give sultone 23a Vinylmagnesium chloride (1.6M in THF, 282 mL, 0.45 mmol) was added to a solution of sultone 22a4 (118 mg, 0.41 mmol) in THF (15 mL) at 0 C. After stirring for 2 h at 0 C, saturated ammonium chloride solution was added, and the mixture was extracted with dichloromethane. The combined organic extracts were washed with brine, dried over magnesium sulfate and concentrated in vacuo. The crude product was purified by flash chromatography (dichloromethane/diethyl ether, 2:1) to afford sultone 23a (109.4 mg, 84%) as a white solid; Rf 0.20 (dichloromethane/diethyl ether, 2:1); IR (ATR): nmax 3513, 2988, 2964, 1742, 1458, 1371, 1352, 1280, 1267, 1173, 1075, 960, 804, 767 cm1; 1H NMR (500 MHz, CDCl3) d 1.28 (t, J¼7.1 Hz, 3H), 1.70e1.74 (m, 1H), 1.76e1.88 (m, 2H), 2.15e2.21 (m, 1H), 2.66e2.71 (m, 1H), 2.96e3.00 (m, 1H), 3.38 (br s, 1H, OH), 3.68e3.71 (m, 1H), 4.22 (d, J¼10.7 Hz, 1H), 4.20e4.26 (m, 2H), 4.57 (d, J¼10.7 Hz, 1H), 5.26 (dd, J¼10.8, 0.9 Hz, 1H), 5.47 (dd, J¼17.0, 0.9 Hz, 1H), 5.84 (dd, J¼17.0, 10.8 Hz, 1H); 13C NMR (125 MHz, CDCl3) d 14.1 (CH3), 26.2 (CH2), 31.2 (CH2), 34.0 (CH2), 61.5 (CH), 62.3 (CH2), 71.5 (CH2), 72.8 (C), 90.6 (C), 91.6 (C), 117.0 (CH2), 137.1 (CH), 167.8 (C); LC-MS (ESI): m/z 336.0 [MþNH4]þ. Anal. calcd for C13H18O7S: C, 49.05; H, 5.70; S, 10.07. Found: C, 49.14; H, 5.81; S, 9.76. 4.15. Grignard addition to give sultone 23b Vinylmagnesium chloride (1.6M in THF, 518 mL, 0.83 mmol) was added to a solution of sultone 22b4 (256 mg, 0.69 mmol) in THF (25 mL) at 0 C. After stirring for 4 h at 0 C, saturated ammonium chloride solution was added, and the mixture was extracted with dichloromethane. The combined organic extracts were washed with brine, dried over magnesium sulfate and concentrated in vacuo. The crude product was purified by flash chromatography (dichloromethane/diethyl ether/pentane, 1:1:1) to afford sultone 23b (237 mg, 87%) as a white solid; Rf 0.24 (dichloromethane/ diethyl ether/pentane, 1:1:1); IR (ATR): nmax 3520, 3065, 2982, 1740, 1457, 1352, 1279, 1267, 1170, 1089, 1059, 952, 822, 766, 739, 700 cm1; 1H NMR (500 MHz, CDCl3) d 1.05e1.08 (m, 1H), 1.30 (t, J¼7.1 Hz, 3H), 1.65e1.68 (m, 2H), 1.70e1.77 (m, 1H), 2.63 (dd, J¼8.8, 14.9 Hz, 1H), 3.15 (dd, J¼3.5, 14.9 Hz, 1H), 3.88 (dd, J¼3.5, 8.8 Hz, 1H), 4.20e4.30 (m, 2H), 5.24 (d, J¼10.9, 1H), 5.43 (d, J¼17.0 Hz, 1H), 5.71 (s, 1H), 5.81 (dd, J¼17.0, 10.9 Hz, 1H), 7.35e7.55 (m, 5H); 13C NMR (125 MHz, CDCl3) d 14.1 (CH3), 27.6 (CH2), 30.6 (CH2), 32.6 (CH2), 61.3 (CH), 62.3 (CH2), 72.7 (C), 87.3 (CH), 91.1 (C), 94.2 (C), 117.1 (CH2), 126.9 (CH), 129.0 (CH), 129.6 (CH), 133.4 (C), 136.9 (CH), 167.8 (C); LC-MS (ESI): m/z 412.1 [MþNH4]þ. Anal. calcd for C19H22O7S: C, 57.86; H, 5.62; S, 8.13. Found: C, 57.68; H, 5.54; S, 8.00. 4.16. b-Elimination to give sultone 24a Methyllithium (1.6M in diethyl ether, 117 mL, 187 mmol) was added to a solution of sultone 23a (29 mg, 91 mmol) in THF (10 mL) at 78 C. After stirring for 15 min at 78 C, saturated ammonium chloride solution was added, and the mixture was extracted with ethyl acetate. The combined organic extracts were washed with brine, dried over magnesium sulfate and concentrated in vacuo. The crude product was purified by flash chromatography (dichloromethane/diethyl ether, 2:1) to afford sultone 24a (18.3 mg, 63%) as a white solid; Rf 0.20 (dichloromethane/diethyl ether, 2:1); IR (ATR): nmax 3518, 2996, 2958, 1742, 1455, 1370, 1357, 1285, 1266, 1175, 1079, 960, 804, 767 cm1; 1H NMR (500 MHz,
CDCl3) d 1.28 (t, J¼7.2 Hz, 3H), 2.03e2.09 (m, 2H), 2.12e2.17 (m, 1H), 2.68e2.74 (m, 1H), 2.83 (d, J¼16.7, 1H), 2.99 (br s, 1H, OH), 3.11 (dd, J¼16.7, 1.7 Hz, 1H), 3.88 (br s, 1H, OH), 4.17e4.29 (m, 2H), 4.84 (d, J¼14.4 Hz, 1H), 4.89 (d, J¼14.4 Hz, 1H), 5.24 (dd, J¼10.8, 0.9 Hz, 1H), 5.42 (dd, J¼17.0, 0.9 Hz, 1H), 5.94 (dd, J¼17.0, 10.8 Hz, 1H); 13C NMR (125 MHz, CDCl3) d 13.9 (CH3), 21.7 (CH2), 28.4 (CH2), 33.6 (CH2), 63.1 (CH2), 71.8 (CH2), 77.5 (C), 77.9 (C), 115.6 (CH2), 126.7 (C), 138.9 (CH), 145.5 (C), 172.6 (C); LC-MS (ESI): m/z 336.0 [MþNH4]þ. HRMS (EI): m/z calcd for C13H18O7S ([M]þ) 318.0773; found 318.0762. 4.17. b-Elimination to give sultone 24b Methyllithium (1.6M in diethyl ether, 303 mL, 484 mmol) was added to a solution of sultone 23b (93 mg, 236 mmol) in THF (10 mL) at 78 C. After stirring for 15 min at 78 C, saturated ammonium chloride solution was added, and the mixture was extracted with ethyl acetate. The combined organic extracts were washed with brine, dried over magnesium sulfate and concentrated in vacuo. The crude product was purified by flash chromatography (dichloromethane/diethyl ether, 2:1) to afford sultone 24b (74 mg, 80%) as a white solid; Rf 0.25 (dichloromethane/diethyl ether, 2:1); IR (ATR): nmax 3499, 3060, 2924, 2853, 1728, 1457, 1330, 1178, 1124, 1001, 916, 857, 767, 700 cm1; 1H NMR (500 MHz, CDCl3) d 1.34 (t, J¼7.1 Hz, 3H), 1.79e1.86 (m, 3H), 2.63e2.67 (m, 1H), 2.88e2.92 (m, 2H), 3.19e3.23 (m, 1H), 3.71 (br s, 1H, OH), 4.27e4.43 (m, 2H), 5.18 (d, J¼10.9 Hz, 1H), 5.36 (d, J¼17.0 Hz, 1H), 5.82 (s, 1H, 9-H), 5.87 (dd, J¼17.0, J¼10.9 Hz, 1H), 7.40e7.46 (m, 5H); 13C NMR (125 MHz, CDCl3) d 14.1 (CH3), 21.5 (CH2), 28.5 (CH2), 33.3 (CH2), 63.1 (CH2), 77.3 (C), 77.7 (C), 86.4 (CH), 115.5 (CH2), 126.9 (C), 127.9 (CH), 129.1 (CH), 130.2 (CH), 133.6 (C), 139.0 (CH), 148.2 (C), 172.5 (C); LC-MS (ESI): m/z 412.1 [MþNH4]þ. HRMS (EI): m/z calcd for C19H22O7S ([M]þ) 394.1086; found 394.1100. Acknowledgements Financial support of this work by the Deutsche Forschungsgemeinschaft and the DAAD is gratefully acknowledged. Supplementary data Supplementary data (NMR spectra for all new compounds) related to this article can be found at http://dx.doi.org/10.1016/ j.tet.2015.05.095. References and notes 1. Review: Mondal, S. Chem. Rev. 2012, 112, 5339e5355. 2. (a) Mondal, S.; Debnath, S.; Das, B. Tetrahedron 2015, 71, 476e486; (b) Qi, Z.; € ckner, R. Wang, M.; Li, X. Chem. Commun. 2014, 9776e9778; (c) Walleser, P.; Bru Eur. J. Org. Chem. 2014, 3210e3224; (d) Mondal, S.; Debnath, S. Tetrahedron Lett. 2014, 55, 1577e1580; (e) Rad-Moghadam, K.; Roudsari, S. T.; Sheykhan, M. Synlett 2014, 827e830; (f) Gaitzsch, J.; Rogachev, V.; Zahel, M.; Metz, P. Synthesis 2014, 46, 531e536; (g) Ghandi, M.; Taheri, A.; Hasani Bozcheloei, A.; Abbasi, A.; Kia, R. Tetrahedron 2012, 68, 3641e3648; (h) Li, F.; Liu, T.-X.; Wang, G.-W. Org. Lett. 2012, 14, 2176e2179; (i) Li, F.; Jiang, T.; Cai, H.; Wang, G. Chin. J. Chem. 2012, 30, 2041e2046; (j) Ghandi, M.; Hasani Bozcheloei, A.; Nazari, S. H.; Sadeghzadeh, M. J. Org. Chem. 2011, 76, 9975e9982. 3. Reviews: (a) Padwa, A. Tetrahedron 2011, 67, 8057e8072; (b) Padwa, A. Helv. Chim. Acta 2005, 88, 1357e1374; (c) Chiu, P. Pure Appl. Chem. 2005, 77, 1183e1189; (d) Mehta, G.; Muthusamy, S. Tetrahedron 2002, 58, 9477e9504. €ger, A.; 4. Shi, B.; Merten, S.; Wong, D. K. Y.; Chu, J. C. K.; Liu, L. L.; Lam, S. K.; Ja Wong, W.-T.; Chiu, P.; Metz, P. Adv. Synth. Catal. 2009, 351, 3128e3132. 5. Reviews: (a) Merfort, I. Curr. Drug Targets 2011, 12, 1560e1573; (b) Schmidt, T. J. Stud. Nat. Prod. Chem. 2006, 33, 309e392. 6. Angle, S. R.; Choi, I.; Tham, F. S. J. Org. Chem. 2008, 73, 6268e6278. 7. Cahiez, G.; Alexakis, A.; Normant, J. F. Tetrahedron Lett. 1978, 19, 3013e3014. 8. More, J. D.; Finney, N. S. Org. Lett. 2002, 4, 3001e3003. 9. (a) Bal, B. S.; Childers, W. E., Jr.; Pinnick, H. W. Tetrahedron 1981, 37, 2091e2096; (b) Kraus, G. A.; Taschner, M. J. J. Org. Chem. 1980, 45, 1175e1176; (c) Lindgren, B. O.; Nilsson, T. Acta Chem. Scand. 1973, 27, 888e890. 10. Lam, S. K.; Chiu, P. Chem.dEur. J. 2007, 13, 9589e9599.
T. Groß et al. / Tetrahedron 71 (2015) 5925e5931 11. Radosevich, A. T.; Chan, V. S.; Shih, H.-W.; Toste, F. D. Angew. Chem. 2008, 120, 3815e3818 Angew. Chem. Int. Ed. 2008, 47, 3755e3758. 12. Tolochko, L. A.; Sipyagin, A. M.; Kartsev, V. G.; Aliev, Z. G.; Atovmyan, L. O.; Lebedev, A. T. Chem. Heterocycl. Compd. 1988, 24, 370e376. 13. Rondestvedt, C. S., Jr. J. Am. Chem. Soc. 1954, 76, 1926e1929. 14. Reviews: (a) Alonso, D. A.; N ajera, C. Org. React. 2008, 72 367e656; (b) N ajera, C.; Yus, M. Tetrahedron 1999, 55, 10547e10658; (c) Trost, B. M. Bull. Chem. Soc. Jpn. 1988, 61, 107e124. 15. Holmquist, C. R.; Roskamp, E. J. Tetrahedron Lett. 1992, 33, 1131e1134. 16. (a) Plessis, C.; Uguen, D.; De Cian, A.; Fischer, J. Tetrahedron Lett. 2000, 41, 5489e5493; (b) Weatherhead-Kloster, R. A.; Corey, E. J. Org. Lett. 2006, 8, 171e174. 17. (a) Charette, A. B.; Wurz, R. P.; Ollevier, T. J. Org. Chem. 2000, 65, 9252e9254; (b) Wurz, R. P.; Lin, W.; Charette, A. B. Tetrahedron Lett. 2003, 44, 8845e8848.
5931
18. Crystallographic data (excluding structure factors) for the structures in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication nos. CCDC 1042282 (20) and CCDC 1042281 (21). Copies of the data can be obtained, free of charge, on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK, (fax: þ44 (0) 1223 336033 or e-mail: [email protected]). 19. Keller, E. SCHAKAL 99, A Computer Program for the Graphic Representation of Molecular and Crystallographic Models; University of Freiburg: Germany, 1999. 20. Review: Chiu, P.; Lautens, M. Top. Curr. Chem. 1997, 190, 1e85. 21. Lautens, M.; Fillion, E.; Sampat, M. Tetrahedron Lett. 1998, 39, 1501e1504. 22. Ewas, A. M. M.; Dawood, K. M. H.; Spinde, K.; Wang, Y.; J€ ager, A.; Metz, P. Synlett 2009, 1773e1776. 23. Metz, P.; Cramer, E. Tetrahedron Lett. 1993, 34, 6371e6374. 24. Black, T. H. Aldrichimica Acta 1983, 16, 3e10.
Contents lists available at ScienceDirect
Tetrahedron journal homepage: www.elsevier.com/locate/tet
Further studies on sultones derived from carbene cyclization cycloaddition cascades €ger a, y, Pauline Chiu b, Tobias Groß a, Therese Herrmann a, Bairu Shi a, Anne Ja Peter Metz a, * a b
€t Dresden, Bergstraße 66, 01069 Dresden, Germany Department of Chemistry, Organic Chemistry I, Technische Universita Department of Chemistry and State Key Laboratory of Synthetic Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong
a r t i c l e i n f o
a b s t r a c t
Article history: Received 17 April 2015 Received in revised form 22 May 2015 Accepted 25 May 2015 Available online 29 May 2015
A sulfonyl-stabilized diazoketone underwent an efficient rhodium-catalyzed cascade reaction with an internal vinylsulfonate unit to give a tricyclic sultone as a single diastereomer. Nucleophilic addition of a vinyl Grignard reagent to the ketone of the resultant arylsulfonyl-substituted cycloadduct was stereocomplementary with respect to vinyl Grignard addition to corresponding ester-substituted substrates. The latter tricyclic compounds were chemoselectively transformed into vinylsultones via b-elimination in good yield. Ó 2015 Elsevier Ltd. All rights reserved.
Keywords: Cycloaddition Diazoketones Domino reactions Sulfur heterocycles Transition metal catalysis
1. Introduction Sultones are synthetically useful heterocycles.1,2 Recently, we described an efficient access to g- and d-sultones embedded in a trior tetracyclic framework by rhodium-catalyzed carbene cyclization cycloaddition cascade (CCCC) reactions,3 e.g. of substrates 1 to afford the heterocycles 2 (Scheme 1).4 Similarly, the polycyclic compounds 3 and 4 were readily available from the corresponding vinylsulfonates. While sultones 2 and 3 can serve as building blocks for highly substituted seven-membered carbocycles, sultone 4 embedding the hydroazulene framework is a potential precursor of pseudoguaianolide sesquiterpene lactones.5 For all substrates studied in this context so far, the diazoketone moiety was stabilized by an adjacent ester group (cf. 1). In order to gain enhanced flexibility regarding the synthetic elaboration of the polycyclic cycloadducts, we were interested in the reactivity of a corresponding non-stabilized diazoketone (1 with H instead of CO2Et). Furthermore, we decided to explore an alternative stabilizing substituent that might be replaced by a hydrogen atom after the CCCC process. Herein we report our investigations along these
* Corresponding author. Tel.: þ49 351 463 37006; fax: þ49 351 463 33162; e-mail address: [email protected] (P. Metz). y Author responsible for X-ray diffraction analyses. http://dx.doi.org/10.1016/j.tet.2015.05.095 0040-4020/Ó 2015 Elsevier Ltd. All rights reserved.
Scheme 1. Sultones 2e4 prepared by rhodium-catalyzed carbene cyclization cycloaddition cascade (CCCC) reactions of vinylsulfonates.
lines as well as toward the structural modification of sultones such as 2. 2. Results and discussion At first, we set out to prepare the vinylsulfonate of the polyfunctional diazoketone 10 (Scheme 2). Similar to the synthesis of 1 (R1¼R2¼H),4 we departed from ethyl glycolate (5) that was transformed into the Weinreb amide 6 via the known triethylsilyl (TES) ether6 of hydroxy ester 5. Homologation of 6 with Normant’s Grignard reagent7 and subsequent oxidation with o-iodoxybenzoic
5926
T. Groß et al. / Tetrahedron 71 (2015) 5925e5931
acid (IBX)8 yielded keto aldehyde 7. Conversion of 7 to 9 proceeded uneventfully by sodium chlorite oxidation9 to give 8 followed by standard generation of the diazoketone function.10 Gratifyingly, subjecting TES ether 9 to acetic acid in THF/water11 led to the sensitive alcohol 10 in high yield, whereas deblocking of the tbutyldimethylsilyl (TBS) analog of 9 prepared from 5 in a corresponding fashion could not be achieved without substantial destruction of the non-stabilized diazoketone unit. Unfortunately, however, all attempts to convert 10 to the corresponding vinylsulfonate met with failure, and only the known chloride 1212 was isolated from treatment of 10 with vinylsulfonyl chloride (11).13
Scheme 3. Preparation of sulfone-stabilized diazoketone 18 and CCCC reaction to give sultone 20. Reagents and conditions: (a) 14, 20 mol % SnCl2, CH2Cl2, 0 C to rt, 69%; (b) TfN3, 9 mol % Bu4NI, 10 mol % Et3N, MeCN, 0 C to rt, 95%; (c) aq HF, MeCN, rt, 84%; (d) 11, Et3N, CH2Cl2, 20 C, 65% 18, 18% 19; (e) 3 mol % Rh2(oct)4, CH2Cl2, rt, 76%.
Scheme 2. Preparation of diazoketone 10 and attempted vinylsulfonate formation. Reagents and conditions: (a) TESCl, imidazole, DMF, rt; (b) HN(OMe)Me∙HCl, i-PrMgCl, THF, 18 C, 67% (2 steps); (c) ClMg(CH2)3OMgCl, THF, 78 C; (d) IBX, ethyl acetate, reflux, 68% (2 steps); (e) NaClO2, NaH2PO4, 2-methylbut-2-ene, t-BuOH, H2O, rt, 75%; (f) i. i-BuOCOCl, Et3N, Et2O, rt, ii. CH2N2, Et2O, 78 Ce0 C, 51%; (g) HOAc, THF, H2O, 0 C, 94%; (h) 11, Et3N, CH2Cl2, 20 C, 10%.
We then turned our attention to the utilization of an electronwithdrawing sulfone as a stabilizing moiety for the diazoketone unit. The p-toluenesulfonyl (SO2Tol) substituted alcohol 17 was chosen as our primary target, since a range of methods for reductive removal of this arylsulfonyl group is available (Scheme 3).14 Tin(II)-catalyzed reaction15 of aldehyde 134 with p-tosyldiazomethane (14)16 furnished the b-ketosulfone 15 in good yield. Diazo transfer of 15 to give 16 was highly efficient using triflyl azide17 in the presence of catalytic amounts of triethylamine and tetrabutylammonium iodide, whereas the use of tosyl azide4 only afforded a 44% yield of 16. In contrast to the behavior of the TBS analog of 9, desilylation of 16 to give alcohol 17 was easily achieved with hydrofluoric acid in acetonitrile. Sulfonylation of 17 with vinylsulfonyl chloride (11) at 20 C was crucial for securing a good yield of the cycloaddition substrate 18. Under these conditions, nucleophilic substitution of 18 to give the chloride 19 is largely suppressed, while 19 is formed as the major product at 0 C. Gratifyingly, the key CCCC reaction of 18 provided sultone 20 as a single diastereomer in 76% yield after 30 min at room temperature when 3 mol % of rhodium(II) octanoate (Rh2(oct)4) was used as the catalyst. With Rh2(OAc)4 (3 mol %, CH2Cl2, rt), 20 was isolated in only 37% yield after 19 h, and treatment of 18 with rhodium(II) trifluoroacetate (3 mol %) or copper(II) acetylacetonate (10 mol %) led to unattractive mixtures. The relative configuration of sultone 20 was determined by 2D NMR experiments and confirmed by Xray diffraction analysis (Fig. 1). With the sultones 20 and 22a,b4 in our hands, we investigated the effect of the different substituents a to the ketone on the diastereoselectivity of a nucleophilic addition to this carbonyl group
Fig. 1. Crystal structure of sultone 20.18,19
(Scheme 4). Reaction of vinylmagnesium bromide with the sulfonyl substituted tricycle 20 yielded solely the allylic alcohol 21 via exo attack of the Grignard reagent. The relative configuration of 21 was unequivocally determined by X-ray diffraction analysis (Fig. 2). In striking contrast, transformation of the ester substituted tricycles 22a,b with a vinyl Grignard reagent afforded only the diastereomers 23a,b, where endo nucleophilic addition took place. Precoordination of the organomagnesium halide to the ester group might account for this complete reversal of diastereoselectivity. The
Scheme 4. Diastereoselective addition of vinyl Grignard reagents to sultones 20 and 22. Reagents and conditions: (a) vinylmagnesium bromide, THF, 0 C, 75%; (b) vinylmagnesium chloride, THF, 0 C, 84% 23a, 87% 23b.
T. Groß et al. / Tetrahedron 71 (2015) 5925e5931
Fig. 2. Crystal structure of sultone 21.18,19
relative configuration of 23a and 23b was unambiguously assigned on the basis of a strong NOE between the two protons depicted in Scheme 4. Some orientating experiments towards cleavage of the oxygen bridge in the tricyclic CCCC adducts by b-elimination were performed with sultones 23a,b (Scheme 5).20 First attempts to induce this process by abstraction of the acidic proton a to the sulfonyl group with lithium diisopropylamide21 only gave low yields of the desired products 24a (30%) and 24b (35%). Likewise, t-butyllithium did not give satisfactory results. However, the use of 2 equiv of methyllithium22 at 78 C allowed a chemoselective opening of the oxygen bridge to give the vinylsultones 24a,b rather efficiently within 15 min already.
Scheme 5. Opening of the oxygen bridge of sultones 23 by b-elimination.
3. Conclusion In summary, the scope of the rhodium-catalyzed carbene cyclization cycloaddition cascade reaction of vinylsulfonates to give polycyclic sultones has been extended to include a sulfonylstabilized diazoketone. The p-toluenesulfonyl substituent of the resultant cycloadduct effected a complete reversal of diastereoselectivity of nucleophilic addition to the ketone as compared to corresponding ester-substituted substrates. The latter tricyclic compounds were chemoselectively transformed into vinylsultones, which now offer further options for synthetic elaboration, e.g. via reductive desulfurization.23
4. Experimental section 4.1. General information All reactions requiring the exclusion of moisture were run under argon using heat-gun-dried flasks. Et2O, THF, and CH2Cl2 were dried with molecular sieves using an MBRAUN MB-SPS-800 device. Flash chromatography was carried out on Merck silica gel 60 (40e63 mm). Thin layer chromatography was carried out on Merck silica gel 60 F254 plates. Melting points were measured with a Wagner & Munz PolyTherm A device. FTIR spectra were recorded with a Nicolet Avatar 360 spectrometer. 1H and 13C NMR spectra were recorded with Bruker instruments: AC-300-P (1H 300 MHz, 13 C 75 MHz), DRX-500-P (1H 500 MHz, 13C 125 MHz), and Avance-
5927
III-600 (1H 600 MHz, 13C 150 MHz). Chemical shifts (d) are quoted in parts per million (ppm) downfield of tetramethylsilane, using residual proton-containing solvent as internal standard (CDCl3 at d¼7.27 ppm and d¼77.0 ppm, respectively). Abbreviations used in the description of resonances are: s (singlet), d (doublet), t (triplet), q (quartet), m (multiplet), br. (broad). Coupling constants (J) are quoted to the nearest 0.1 Hz. The multiplicities of the 13C NMR signals were determined using DEPT spectra. Mass spectra were recorded with an Agilent 5973N detector coupled with an Agilent 6890N GC (GCeMS, 70 eV) and a Bruker Esquire LC (LC/MS, ESI). High-resolution mass spectrometry (HRMS) was carried out with a Finnigan MAT 95 (EI, 70 eV) instrument. Elemental analysis was performed using a Hekatech EA 3000 instrument. X-ray analyses were carried out with a Bruker Kappa CCD diffractometer. 4.2. Weinreb amide 6 Hydroxy ester 5 (1.67 g, 16.0 mmol) was dissolved in dichloromethane (30 mL), and triethylchlorosilane (2.89 g, 19.2 mmol) and imidazole (1.31 g, 19.2 mmol) were added. The solution was stirred at room temperature for 10 h. The precipitate formed was removed by filtration over silica gel (elution with diethyl ether). After evaporation of the solvent, the crude silyl ether6 (3.50 g) was used for the next reaction. To a solution of N,O-dimethylhydroxylamine hydrochloride (5.50 g, 56 mmol) in THF (30 mL) cooled to 18 C was dropwise added a solution of i-propylmagnesium chloride (2M in THF, 48 mL, 96 mmol). After stirring at this temperature for 2.5 h, a solution of the crude silyl ether (3.50 g) in THF (30 mL) was added slowly, and stirring was continued for 4 h. A saturated solution of ammonium chloride (100 mL) was added, the layers were separated, and the aqueous layer was extracted with ethyl acetate. After drying the organic layer over magnesium sulfate, the crude product was purified by flash chromatography (pentane/ethyl acetate, 4:1) to give the Weinreb amide 6 (2.50 g, 67% over two steps) as a colorless oil; Rf 0.40 (pentane/ethyl acetate, 4:1); IR (ATR): nmax 2954, 2911, 2876, 1693, 1460, 1442, 1414, 1390, 1329, 1238, 1155, 1086, 995, 805, 769, 727, 673 cm1; 1H NMR (300 MHz, CDCl3) d 0.66 (q, J¼7.9 Hz, 6H), 0.98 (t, J¼7.9 Hz, 9H), 3.18 (s, 3H), 3.67 (s, 3H), 4.41 (s, 2H); 13C NMR (75 MHz, CDCl3) d 4.4 (CH2), 6.7 (CH3), 32.5 (CH3), 61.4 (CH3), 61.4 (CH2), the carbonyl carbon was not detected due to the quadrupole relaxation of nitrogen; GCeMS (EI): m/z (%)¼205 (15), 204 (100) [MC2H5]þ, 144 (12), 117 (16), 103 (2), 88 (11), 87 (11), 75 (4), 59 (12). Anal. calcd for C10H23NO3Si: C, 51.46; H, 9.93; N, 6.00. Found: C, 51.54; H, 9.86; N, 6.17. 4.3. Keto aldehyde 7 A solution of i-propylmagnesium chloride (2 M, 13 mL, 26 mmol) was diluted with THF (10 mL) and cooled in an ice bath. 3-Chloro-1-propanol (2 mL, 23.9 mmol) dissolved in THF (10 mL) was added over 10 min, and the resultant mixture was stirred for 1 h. The light brown solution decolorized almost completely. In a second flask equipped with a reflux condenser, magnesium turnings (1.00 g, 41.1 mmol) were added to THF (5 mL). After activation with dibromoethane (0.1 mL), the mixture was heated to reflux for 10 min. Then the magnesium alkoxide solution prepared as described above was added, and the mixture was refluxed for 3 h and cooled to room temperature. This solution was added to a solution of Weinreb amide 6 (2.41 g, 10.3 mmol) in THF (20 mL) cooled to 78 C. The mixture was stirred overnight (17 h), while the cooling bath was allowed to warm to room temperature. Then a saturated solution of ammonium chloride was added, the layers were separated, and the aqueous layer was extracted with ethyl acetate. After washing with brine and drying the organic layer over magnesium sulfate, the solvents were evaporated, and the crude keto alcohol (2.92 g) was used for the next step. To a solution of this
5928
T. Groß et al. / Tetrahedron 71 (2015) 5925e5931
crude keto alcohol (2.92 g) in ethyl acetate (50 mL) was added IBX (4.50 g, 16.0 mmol). The resultant mixture was heated to reflux for 8 h. After cooling and filtration over silica gel (elution with diethyl ether), the solvents were removed in vacuo, and the crude product was purified by flash chromatography (dichloromethane/diethyl ether, 9:1) to give the keto aldehyde 7 (1.55 g, 68% over two steps) as a colorless oil; Rf 0.60 (dichloromethane/diethyl ether, 9:1); IR (ATR): nmax 2955, 2911, 2878, 2833, 2725, 1723, 1408, 1357, 1239, 1160, 1101, 1008, 789, 742, 537 cm1; 1H NMR (300 MHz, CDCl3) d 0.64 (q, J¼7.9 Hz, 6H), 0.97 (t, J¼7.9 Hz, 9H), 2.79e2.93 (m, 4H), 4.23 (s, 2H), 9.81 (s, 1H); 13C NMR (75 MHz, CDCl3) d 4.3 (CH2), 6.6 (CH3), 30.7 (CH2), 37.0 (CH2), 68.9 (CH2), 200.4 (CH), 209.3 (C); GCeMS (EI): m/z (%)¼201 (31) [MC2H5]þ, 183 (10), 159 (25), 158 (16), 157 (100), 129 (33), 117 (19), 115 (18), 103 (23), 87 (23), 75 (19), 59 (23), 58 (11), 55 (11), 47 (7). Anal. calcd for C11H22O3Si: C, 57.35; H, 9.63. Found: C, 57.28; H, 9.57. 4.4. Carboxylic acid 8 Aldehyde 7 (1.40 g, 6.10 mmol) was dissolved in t-butanol (20 mL) at room temperature. 2-Methylbut-2-ene (4.20 mL, 48.6 mmol) and then a mixture of sodium chlorite (80%, 4.12 g, 30.8 mmol) and sodium dihydrogen phosphate (5.45 g, 39.5 mmol) in water (35 mL) were added, whereupon the reaction mixture turned yellow. After stirring for 45 min, the resultant colorless solution was extracted with ethyl acetate. The combined organic layers were washed with brine and dried over magnesium sulfate. After filtration, the crude product was concentrated in vacuo and purified by flash chromatography (pentane/ethyl acetate, 2:1) to give carboxylic acid 8 (1.12 g, 75%) as a yellow oil; Rf 0.17 (pentane/ethyl acetate, 2:1); IR (ATR): nmax 3050, 2956, 2913, 2878, 1724, 1711, 1411, 1240, 1159, 1102, 1006, 817, 743 cm1; 1H NMR (300 MHz, CDCl3) d 0.63 (q, J¼7.9 Hz, 6H), 0.96 (t, J¼7.9 Hz, 9H), 2.67 (t, J¼6.0 Hz, 2H), 2.82 (t, J¼6.0 Hz, 2H), 4.20 (s, 2H); 13C NMR (75 MHz, CDCl3) d 4.3 (CH2), 6.6 (CH3), 27.3 (CH2), 32.9 (CH2), 68.8 (CH2), 178.0 (C), 209.3 (C); GCeMS (EI): m/z (%)¼217 (31) [MC2H5]þ, 199 (5), 171 (72), 157 (100), 129 (14), 115 (13), 113 (13), 103 (13), 101 (12), 87 (18), 75 (19), 59 (18), 58 (11), 56 (12), 47 (5), 45 (12). Anal. calcd for C11H22O4Si: C, 53.62; H, 9.00. Found: C, 53.78; H, 9.21. 4.5. Diazoketone 9 To a solution of carboxylic acid 8 (250 mg, 1.02 mmol) in diethyl ether (7.5 mL) was added i-butyl chloroformate (178 mg, 1.30 mmol) and triethylamine (147 mg, 1.45 mmol) at room temperature. After stirring the mixture for 36 h, the precipitate formed was removed by filtration and eluted with some diethyl ether. Diazomethane was synthesized according to a reported procedure24 using DiazaldÒ (2.50 g, 11.5 mmol) dissolved in diethyl ether (20 mL). The reaction vessel was loaded with water (2.0 mL), diethyl ether (4.0 mL), and 2-(2-ethoxyethoxy)ethanol (7.0 mL). The condenser was cooled to78 C, and diazomethane in diethyl ether was collected at 20 C. This solution was covered with argon and dried over potassium hydroxide at 0 C for 1 h and at 78 C for 2 h. Then it was added to the cooled (78 C) mixed anhydride solution prepared from 8 as described above. The resulting mixture was stirred for 24 h, while the cooling bath was allowed to warm to 0 C. Argon was bubbled through the solution for 1 h, and acetic acid was added in order to remove excess diazomethane. After extraction with diethyl ether, washing with brine, drying over magnesium sulfate, and filtration, the solvent was removed in vacuo. The crude product was purified by flash chromatography (pentane/ethyl acetate, 2:1) to afford diazoketone 9 (141 mg, 51%) as a yellow oil; Rf 0.45 (pentane/ethyl acetate, 2:1); IR (ATR): nmax 3090, 2955, 2912, 2877, 2100, 1724, 1642, 1377, 1346, 1319, 1152, 1098, 1062, 1004, 809, 728 cm1; 1H NMR (300 MHz, CDCl3) d 0.63
(q, J¼8.0 Hz, 6H), 0.97 (t, J¼8.0 Hz, 9H), 2.56e2.66 (br s, 2H), 2.87 (t, J¼6.5 Hz, 2H), 4.22 (s, 2H), 5.23e5.86 (br s, 1H); 13C NMR (125 MHz, CDCl3) d 4.2 (CH2), 6.6 (CH3), 32.9 (CH2), 33.5 (CH2), 54.5 (CH), 68.9 (CH2), 193.2 (C), 209.6 (C); GCeMS (EI): m/z (%)¼214 (12), 213 (100) [MN2C2H5]þ, 171 (66), 129 (13), 127 (10), 115 (10), 113 (10), 103 (12), 99 (10), 87 (13), 75 (22), 59 (12), 47 (10). HRMS (EI): m/z calcd for C10H17N2O3Si ([MC2H5]þ) 241.1008; found 241.1009. 4.6. Desilylation of diazoketone 9 To a solution of diazoketone 9 (50.0 mg, 0.18 mmol) in THF (2.5 mL) cooled to 0 C was added water (0.5 mL) and acetic acid (0.5 mL). After stirring for 7 h at 0 C, the mixture was treated with saturated aqueous ammonium chloride solution and extracted with ethyl acetate. The combined organic layers were dried over sodium sulfate, and the solvent was removed in vacuo. The crude product was purified by flash chromatography (ethyl acetate) to afford diazoketone 10 (27.2 mg, 94%) as a yellow oil; Rf 0.22 (ethyl acetate); IR (ATR): nmax 3422, 3372, 3068, 2916, 2864, 2104, 1717, 1633, 1381, 1341, 1142, 1050, 994, 644, 592, 574 cm1; 1H NMR (300 MHz, CDCl3) d 2.73 (br s, 4H), 2.98 (t, J¼4.9 Hz, 1H, OH), 4.33 (d, J¼4.9 Hz, 2H), 5.37 (br s, 1H); 13C NMR (75 MHz, CDCl3) d 32.3 (CH2), 33.7 (CH2), 54.7 (CH), 68.2 (CH2), 192.5 (C), 208.5 (C); GCeMS (EI): m/z (%)¼157 (3) [MþH]þ, 126 (9), 125 (100), 98 (16), 69 (13), 55 (97), 43 (13), 41 (19), 39 (12), 31 (29), 28 (10), 27 (22). HRMS (EI): m/z calcd for C6H9N2O3 ([MþH]þ) 157.0613; found 157.0605. 4.7. Attempted vinylsulfonate formation with alcohol 10 Triethylamine (60 mL, 0.423 mmol) was added to a solution of diazoketone 10 (60.1 mg, 0.38 mmol) in dichloromethane (6 mL) cooled to 20 C. Then a solution of ice-cold vinylsulfonyl chloride (11, 53.5 mg, 0.423 mmol) in dichloromethane (5 mL) was added dropwise. The resultant mixture was stirred for 15 min and then quickly filtered over silica gel (elution with ice-cold dichloromethane). After removal of the solvent in vacuo, the residue was subjected to flash chromatography (dichloromethane/diethyl ether, 2:1) to give chloride 1212 (12.0 mg, 10%) as a yellow oil. A second product, presumably the desired vinylsulfonate, was visible on TLC at Rf 0.44 (dichloromethane/diethyl ether, 2:1). However, this compound decomposed after evaporation of the solvent. 12: Rf 0.63 (dichloromethane/diethyl ether, 2:1); IR (ATR): nmax 3102, 2935, 2101, 1731, 1627, 1378, 1318, 1132, 1066, 771, 549 cm1; 1H NMR (300 MHz, CDCl3) d 2.67e2.73 (m, 2H), 2.92 (t, J¼6.3 Hz, 2H), 4.17 (s, 2H), 5.31 (br s, 1H); 13C NMR (75 MHz, CDCl3) d 33.9 (CH2), 34.1 (CH2), 48.2 (CH2), 54.7 (C), 192.6 (C), 210.5 (C); LC-MS (ESI): m/z 174.9 [MþH]þ, 370.9 [2MþNa]þ. 4.8. Diketo sulfone 15 Tin(II) chloride (24.7 mg, 0.130 mmol) and p-tosyldiazomethane16 (14, 307 mg, 1.56 mmol) were added to a solution of aldehyde 134 (150 mg, 0.650 mmol) in dichloromethane (0.4 mL) cooled to 0 C. The mixture was stirred for 10 min at 0 C and for 5.5 h at room temperature. After filtration over silica gel (elution with ethyl acetate) to remove the tin salt and concentration in vacuo, the crude product was purified by flash chromatography (pentane/diethyl ether, 1:1 to 1:3) to afford diketo sulfone 15 (180 mg, 69%) as a yellow oil; Rf 0.45 (pentane/diethyl ether, 1:3); IR (ATR): nmax 3427, 2997, 2936, 2860, 1713, 1393, 1305, 1292, 1183, 1141, 1084, 1043, 993, 816, 801, 741, 674 cm1; 1H NMR (300 MHz, CDCl3) d 0.08 (s, 6H), 0.92 (s, 9H), 2.45 (s, 3H), 2.77e2.83 (m, 2H), 2.96e3.02 (m, 2H), 4.18 (s, 2H), 4.21 (s, 2H), 7.36 (d, J¼8.2 Hz, 2H), 7.78 (d, J¼8.2 Hz, 2H); 13C NMR (75 MHz, CDCl3) d 5.6 (CH3), 18.2 (C), 21.7 (CH3), 25.7 (CH3), 32.4 (CH2), 37.3 (CH2), 67.3 (CH2), 69.1 (CH2), 128.3 (CH), 130.0 (CH), 135.7 (C), 145.4 (C), 197.1 (C), 209.1 (C);
T. Groß et al. / Tetrahedron 71 (2015) 5925e5931
GCeMS (EI): m/z (%)¼341 (20) [MC4H9]þ, 324 (10), 323 (44), 249 (25), 213 (17), 185 (51), 167 (10), 155 (18), 149 (14), 139 (11), 130 (10.4), 129 (100), 91 (30), 89 (11), 81 (10), 75 (21), 73 (30); LC-MS (ESI): m/z 399.1 [MþH]þ, 416.1 [MþNH4]þ. HRMS (EI): m/z calcd for C15H21O5SSi ([MC4H9]þ) 341.0879; found 341.0891. 4.9. Diazoketone 16 To a solution of diketo sulfone 15 (1.10 g, 2.76 mmol) and tetrabutylammonium iodide (0.09 g, 0.25 mmol) in acetonitrile (10 mL) cooled to 0 C was added trifluoromethanesulfonyl azide (0.5M in hexane, 12 mL, 6 mmol) and triethylamine in acetonitrile (1:10 v/v, 37.5 mL, 0.27 mmol). Conversion was complete after stirring for 2.5 h, while allowing the mixture to warm to room temperature. After filtration over silica gel (elution with diethyl ether) and concentration in vacuo, the crude product was purified by flash chromatography (pentane/diethyl ether, 1:2) to yield diazoketone 16 (1.12 g, 95%) as a yellow oil; Rf 0.73 (pentane/diethyl ether, 1:2); IR (ATR): nmax 3478, 2950, 2929, 2858, 2125, 1722, 1651, 1330, 1186, 1147, 1119, 1083, 1067, 1034, 988, 838, 814, 706, 666, 590, 562 cm1; 1H NMR (300 MHz, CDCl3) d 0.07 (s, 6H), 0.90 (s, 9H), 2.46 (s, 3H), 2.79e2.90 (m, 4H), 4.17 (s, 2H), 7.37 (d, J¼8.3 Hz, 2H), 7.87 (d, J¼8.3 Hz, 2H); 13C NMR (75 MHz, CDCl3) d 5.6 (CH3), 18.2 (C), 21.7 (CH3), 25.7 (CH3), 32.1 (CH2), 32.5 (CH2), 69.1 (CH2), 127.3 (CH), 130.1 (CH), 139.1 (C), 145.4 (C), 187.2 (C), 209.0 (C), the carbon directly attached to the diazo group was not detected due to the quadrupole relaxation of nitrogen; LC-MS (ESI): m/z 425.1 [MþH]þ, 442.1 [MþNH4]þ. Anal. calcd for C19H28N2O5SSi: C, 53.75; H, 6.65; N, 6.60; S, 7.55. Found: C, 53.69; H, 6.37; N, 6.71; S, 7.72. 4.10. Desilylation of diazoketone 16 to give alcohol 17 Diazoketone 16 (33.0 mg, 0.078 mmol) was dissolved in acetonitrile/aqueous hydrofluoric acid (40%) (95:5 v/v, 5.2 mL). After stirring at room temperature for 1 h, the mixture was diluted with water and extracted with dichloromethane. The combined organic layers were dried over magnesium sulfate, filtered, and evaporated. Purification of the residue by flash chromatography (diethyl ether) gave alcohol 17 (20.3 mg, 84%) as a yellow solid; Rf 0.16 (diethyl ether); mp 94e96 C (decomposition); IR (ATR): nmax 3451, 3090, 3049, 2926, 2851, 2110, 2057, 1703, 1672, 1596, 1402, 1329, 1314, 1224, 1175, 1149, 1085, 1011, 818, 676, 652, 586, 545 cm1; 1H NMR (300 MHz, CDCl3) d 2.47 (s, 3H), 2.68 (t, J¼6.1 Hz, 2H), 2.98 (t, J¼6.1 Hz, 2H), 2.80 (br s, 1H, OH), 4.29 (s, 2H), 7.39 (d, J¼8.4 Hz, 2H), 7.86 (d, J¼8.4 Hz, 2H); 13C NMR (75 MHz, CDCl3) d 21.7 (CH3), 31.6 (CH2), 32.8 (CH2), 68.1 (CH2), 127.3 (CH), 130.2 (CH), 139.0 (C), 145.6 (C), 186.9 (C), 207.7 (C), the carbon directly attached to the diazo group was not detected due to the quadrupole relaxation of nitrogen; LC-MS (ESI): m/z 311.0 [MþH]þ, 328.1 [MþNH4]þ. HRMS (EI): m/z calcd for C12H11N2O4S ([MCH2OH]þ) 279.0440; found 279.0433. 4.11. Vinylsulfonate formation with alcohol 17 Ice-cold vinylsulfonyl chloride (11, 76.0 mg, 0.60 mmol) was slowly added to a solution of alcohol 17 (178.0 mg, 0.574 mmol) and triethylamine (84 mL, 0.60 mmol) in dichloromethane (5 mL) cooled to 20 C. The mixture was stirred at 20 C for 20 min and then quickly filtered over silica gel (elution with ice-cold dichloromethane). After evaporation of the solvent in vacuo, the residue was subjected to flash chromatography (dichloromethane/diethyl ether, 2:1) to give vinylsulfonate 18 (149.3 mg, 65%) as a yellow oil and chloride 19 (33.9 mg, 18%) as a yellow solid. 18: Rf 0.67 (dichloromethane/diethyl ether, 2:1); IR (ATR): nmax 3064, 2925, 2114, 1738, 1660, 1595, 1361, 1331, 1170, 1148, 983, 797, 665, 589 cm1; 1H NMR (500 MHz, CDCl3) d 2.48 (s, 3H), 2.78 (m,
5929
2H), 2.95 (m, 2H), 4.69 (s, 2H), 6.17 (d, J¼10.1 Hz, 1H), 6.45 (d, J¼16.7 Hz, 1H), 6.63 (dd, J¼16.7, 10.1 Hz, 1H), 7.40 (d, J¼8.5 Hz, 2H), 7.86 (d, J¼8.5 Hz, 2H); 13C NMR (125 MHz, CDCl3) d 21.7 (CH3), 32.2 (CH2), 32.7 (CH2), 71.8 (CH2), 127.2 (CH), 130.2 (CH), 131.0 (CH2), 132.2 (CH), 139.0 (C), 145.6 (C), 186.7 (C), 201.1 (C), the carbon directly attached to the diazo group was not detected due to the quadrupole relaxation of nitrogen; LC-MS (ESI): m/z 418.1 [MþNH4]þ, 823.0 [2MþNa]þ. HRMS (EI): m/z calcd for C15H16O7S2 ([MN2]þ) 372.0337; found 372.0331. Anal. calcd for C15H16N2O7S2: C, 44.99; H, 4.03; N, 7.00. Found: C, 45.06; H, 3.64; N, 6.62. 19: Rf 0.80 (dichloromethane/diethyl ether, 2:1); mp 79e80 C; IR (ATR): nmax 3054, 2923, 2103, 1729, 1677, 1595, 1403, 1324, 1230, 1176, 1147, 1084, 817, 748, 666, 583 cm1; 1H NMR (300 MHz, CDCl3) d 2.49 (s, 3H), 2.80e3.02 (m, 4H), 4.14 (s, 2H), 7.40 (d, J¼8.3 Hz, 2H), 7.86 (d, J¼8.3 Hz, 2H); 13C NMR (125 MHz, CDCl3) d 21.7 (CH3), 33.1 (CH2), 33.2 (CH2), 48.1 (CH2), 127.2 (CH), 130.2 (CH), 139.0 (C), 145.6 (C), 186.9 (C), 201.0 (C), the carbon directly attached to the diazo group was not detected due to the quadrupole relaxation of nitrogen; LC-MS (ESI): m/z 329.0 [MþH]þ, 346.1 [MþNH4]þ. 4.12. CCCC reaction to afford sultone 20 To a solution of vinylsulfonate 18 (65.0 mg, 0.16 mmol) in dichloromethane (6 mL) was added Rh2(oct)4 (3.7 mg, 4.8 mmol, 3 mol %). The reaction mixture was stirred at room temperature for 30 min. Gas evolution was observed. After removal of the solvent in vacuo, the residue was purified by flash chromatography (dichloromethane/diethyl ether, 2:1) to yield sultone 20 (45.1 mg, 76%) as a white solid; Rf 0.23 (dichloromethane/diethyl ether, 2:1); mp 230e231 C; IR (ATR): nmax 2987, 1734, 1599, 1452, 1357, 1180, 1151, 1050, 949, 792, 685, 663, 570 cm1; 1H NMR (600 MHz, CDCl3) d 2.12 (ddd, J¼13.9, 8.3, 5.6 Hz, 1H), 2.40 (ddd, J¼13.9, 10.1, 5.6 Hz, 1H), 2.48 (s, 3H), 2.55 (ddd, J¼16.8, 8.3, 5.6 Hz, 1H), 2.71 (ddd, J¼16.8, 10.1, 5.6 Hz, 1H), 2.88 (dd, J¼14.3, 9.4 Hz, 1H), 3.07 (dd, J¼14.3, 6.0 Hz, 1H), 3.68 (dd, J¼9.4, 6.0 Hz, 1H), 4.25 (d, J¼10.9 Hz, 1H), 4.52 (d, J¼10.9 Hz, 1H), 7.38 (d, J¼7.9 Hz, 2H), 7.86 (d, J¼7.9 Hz, 2H); 13C NMR (150 MHz, CDCl3) d 21.8 (CH3), 28.9 (CH2), 34.3 (CH2), 35.8 (CH2), 62.1 (CH), 70.1 (CH2), 92.0 (C), 99.7 (C), 129.7 (CH), 130.7 (CH), 131.5 (C), 146.5 (C), 199.1 (C); GCeMS (EI): m/z (%)¼372 (15) [M]þ, 269 (8), 217 (9), 198 (11), 155 (9), 139 (100), 125 (11), 107 (22), 91 (51), 81 (35), 79 (32), 65 (37), 53 (21), 41 (24); LC-MS (ESI): m/z 390.1 [MþNH4]þ, 761.9 [2MþNH4]þ, 767.0 [2MþNa]þ. HRMS (EI): m/z calcd for C15H16O7S2 ([M]þ) 372.0337; found 372.0342. Anal. calcd for C15H16O7S2: C, 48.38; H, 4.33. Found: C, 48.65; H, 4.50. 4.13. Grignard addition to give sultone 21 Vinylmagnesium bromide (0.01M in THF, 310 mL, 0.031 mmol) was added to a solution of sultone 20 (10.2 mg, 0.027 mmol) in THF (1.7 mL) at 0 C. After stirring for 2 h at 0 C, saturated ammonium chloride solution (1 mL) was added, and the mixture was extracted three times with dichloromethane. The combined organic extracts were washed with brine, dried over magnesium sulfate and concentrated in vacuo. The crude product was purified by flash chromatography (dichloromethane/diethyl ether, 2:1) to give sultone 21 (8.2 mg, 75%) as a white solid; Rf 0.52 (dichloromethane/diethyl ether, 2:1); mp 240e241 C; IR (ATR): nmax 3519, 3028, 2922, 2853, 1597, 1454, 1353, 1287, 1154, 1076, 997, 943, 802, 736, 716, 660 cm1; 1H NMR (500 MHz, CDCl3) d 1.76e2.01 (m, 4H), 2.48 (s, 3H), 2.75 (dd, J¼14.8, 3.8 Hz, 1H), 3.26 (dd, J¼14.8, 9.8 Hz, 1H), 3.66 (dd, J¼9.8, 3.8 Hz, 1H), 3.70 (s, 1H, OH), 4.20 (d, J¼11.0 Hz, 1H), 4.52 (d, J¼11.0 Hz, 1H), 5.32 (dd, J¼10.9, 0.8 Hz, 1H), 5.61 (dd, J¼17.2, 0.8 Hz, 1H), 6.63 (dd, J¼17.2, 10.9 Hz, 1H), 7.38 (d, J¼8.2 Hz, 2H), 7.77 (d, J¼8.2 Hz, 2H); 13C NMR (125 MHz, CDCl3) d 21.8 (CH3), 28.1 (CH2), 33.0 (CH2), 36.3 (CH2), 62.5 (CH), 70.6 (CH2), 73.5 (C), 93.6 (C), 101.9 (C), 114.6 (CH2), 129.8 (CH), 130.4 (CH), 131.5 (C), 137.6
5930
T. Groß et al. / Tetrahedron 71 (2015) 5925e5931
(CH), 146.2 (C); LC-MS (ESI): m/z 418.1 [MþNH4]þ, 423.2 [MþNa]þ. HRMS (EI): m/z calcd for C15H16O7S2 ([MþH]þ) 401.0739; found 401.0733. 4.14. Grignard addition to give sultone 23a Vinylmagnesium chloride (1.6M in THF, 282 mL, 0.45 mmol) was added to a solution of sultone 22a4 (118 mg, 0.41 mmol) in THF (15 mL) at 0 C. After stirring for 2 h at 0 C, saturated ammonium chloride solution was added, and the mixture was extracted with dichloromethane. The combined organic extracts were washed with brine, dried over magnesium sulfate and concentrated in vacuo. The crude product was purified by flash chromatography (dichloromethane/diethyl ether, 2:1) to afford sultone 23a (109.4 mg, 84%) as a white solid; Rf 0.20 (dichloromethane/diethyl ether, 2:1); IR (ATR): nmax 3513, 2988, 2964, 1742, 1458, 1371, 1352, 1280, 1267, 1173, 1075, 960, 804, 767 cm1; 1H NMR (500 MHz, CDCl3) d 1.28 (t, J¼7.1 Hz, 3H), 1.70e1.74 (m, 1H), 1.76e1.88 (m, 2H), 2.15e2.21 (m, 1H), 2.66e2.71 (m, 1H), 2.96e3.00 (m, 1H), 3.38 (br s, 1H, OH), 3.68e3.71 (m, 1H), 4.22 (d, J¼10.7 Hz, 1H), 4.20e4.26 (m, 2H), 4.57 (d, J¼10.7 Hz, 1H), 5.26 (dd, J¼10.8, 0.9 Hz, 1H), 5.47 (dd, J¼17.0, 0.9 Hz, 1H), 5.84 (dd, J¼17.0, 10.8 Hz, 1H); 13C NMR (125 MHz, CDCl3) d 14.1 (CH3), 26.2 (CH2), 31.2 (CH2), 34.0 (CH2), 61.5 (CH), 62.3 (CH2), 71.5 (CH2), 72.8 (C), 90.6 (C), 91.6 (C), 117.0 (CH2), 137.1 (CH), 167.8 (C); LC-MS (ESI): m/z 336.0 [MþNH4]þ. Anal. calcd for C13H18O7S: C, 49.05; H, 5.70; S, 10.07. Found: C, 49.14; H, 5.81; S, 9.76. 4.15. Grignard addition to give sultone 23b Vinylmagnesium chloride (1.6M in THF, 518 mL, 0.83 mmol) was added to a solution of sultone 22b4 (256 mg, 0.69 mmol) in THF (25 mL) at 0 C. After stirring for 4 h at 0 C, saturated ammonium chloride solution was added, and the mixture was extracted with dichloromethane. The combined organic extracts were washed with brine, dried over magnesium sulfate and concentrated in vacuo. The crude product was purified by flash chromatography (dichloromethane/diethyl ether/pentane, 1:1:1) to afford sultone 23b (237 mg, 87%) as a white solid; Rf 0.24 (dichloromethane/ diethyl ether/pentane, 1:1:1); IR (ATR): nmax 3520, 3065, 2982, 1740, 1457, 1352, 1279, 1267, 1170, 1089, 1059, 952, 822, 766, 739, 700 cm1; 1H NMR (500 MHz, CDCl3) d 1.05e1.08 (m, 1H), 1.30 (t, J¼7.1 Hz, 3H), 1.65e1.68 (m, 2H), 1.70e1.77 (m, 1H), 2.63 (dd, J¼8.8, 14.9 Hz, 1H), 3.15 (dd, J¼3.5, 14.9 Hz, 1H), 3.88 (dd, J¼3.5, 8.8 Hz, 1H), 4.20e4.30 (m, 2H), 5.24 (d, J¼10.9, 1H), 5.43 (d, J¼17.0 Hz, 1H), 5.71 (s, 1H), 5.81 (dd, J¼17.0, 10.9 Hz, 1H), 7.35e7.55 (m, 5H); 13C NMR (125 MHz, CDCl3) d 14.1 (CH3), 27.6 (CH2), 30.6 (CH2), 32.6 (CH2), 61.3 (CH), 62.3 (CH2), 72.7 (C), 87.3 (CH), 91.1 (C), 94.2 (C), 117.1 (CH2), 126.9 (CH), 129.0 (CH), 129.6 (CH), 133.4 (C), 136.9 (CH), 167.8 (C); LC-MS (ESI): m/z 412.1 [MþNH4]þ. Anal. calcd for C19H22O7S: C, 57.86; H, 5.62; S, 8.13. Found: C, 57.68; H, 5.54; S, 8.00. 4.16. b-Elimination to give sultone 24a Methyllithium (1.6M in diethyl ether, 117 mL, 187 mmol) was added to a solution of sultone 23a (29 mg, 91 mmol) in THF (10 mL) at 78 C. After stirring for 15 min at 78 C, saturated ammonium chloride solution was added, and the mixture was extracted with ethyl acetate. The combined organic extracts were washed with brine, dried over magnesium sulfate and concentrated in vacuo. The crude product was purified by flash chromatography (dichloromethane/diethyl ether, 2:1) to afford sultone 24a (18.3 mg, 63%) as a white solid; Rf 0.20 (dichloromethane/diethyl ether, 2:1); IR (ATR): nmax 3518, 2996, 2958, 1742, 1455, 1370, 1357, 1285, 1266, 1175, 1079, 960, 804, 767 cm1; 1H NMR (500 MHz,
CDCl3) d 1.28 (t, J¼7.2 Hz, 3H), 2.03e2.09 (m, 2H), 2.12e2.17 (m, 1H), 2.68e2.74 (m, 1H), 2.83 (d, J¼16.7, 1H), 2.99 (br s, 1H, OH), 3.11 (dd, J¼16.7, 1.7 Hz, 1H), 3.88 (br s, 1H, OH), 4.17e4.29 (m, 2H), 4.84 (d, J¼14.4 Hz, 1H), 4.89 (d, J¼14.4 Hz, 1H), 5.24 (dd, J¼10.8, 0.9 Hz, 1H), 5.42 (dd, J¼17.0, 0.9 Hz, 1H), 5.94 (dd, J¼17.0, 10.8 Hz, 1H); 13C NMR (125 MHz, CDCl3) d 13.9 (CH3), 21.7 (CH2), 28.4 (CH2), 33.6 (CH2), 63.1 (CH2), 71.8 (CH2), 77.5 (C), 77.9 (C), 115.6 (CH2), 126.7 (C), 138.9 (CH), 145.5 (C), 172.6 (C); LC-MS (ESI): m/z 336.0 [MþNH4]þ. HRMS (EI): m/z calcd for C13H18O7S ([M]þ) 318.0773; found 318.0762. 4.17. b-Elimination to give sultone 24b Methyllithium (1.6M in diethyl ether, 303 mL, 484 mmol) was added to a solution of sultone 23b (93 mg, 236 mmol) in THF (10 mL) at 78 C. After stirring for 15 min at 78 C, saturated ammonium chloride solution was added, and the mixture was extracted with ethyl acetate. The combined organic extracts were washed with brine, dried over magnesium sulfate and concentrated in vacuo. The crude product was purified by flash chromatography (dichloromethane/diethyl ether, 2:1) to afford sultone 24b (74 mg, 80%) as a white solid; Rf 0.25 (dichloromethane/diethyl ether, 2:1); IR (ATR): nmax 3499, 3060, 2924, 2853, 1728, 1457, 1330, 1178, 1124, 1001, 916, 857, 767, 700 cm1; 1H NMR (500 MHz, CDCl3) d 1.34 (t, J¼7.1 Hz, 3H), 1.79e1.86 (m, 3H), 2.63e2.67 (m, 1H), 2.88e2.92 (m, 2H), 3.19e3.23 (m, 1H), 3.71 (br s, 1H, OH), 4.27e4.43 (m, 2H), 5.18 (d, J¼10.9 Hz, 1H), 5.36 (d, J¼17.0 Hz, 1H), 5.82 (s, 1H, 9-H), 5.87 (dd, J¼17.0, J¼10.9 Hz, 1H), 7.40e7.46 (m, 5H); 13C NMR (125 MHz, CDCl3) d 14.1 (CH3), 21.5 (CH2), 28.5 (CH2), 33.3 (CH2), 63.1 (CH2), 77.3 (C), 77.7 (C), 86.4 (CH), 115.5 (CH2), 126.9 (C), 127.9 (CH), 129.1 (CH), 130.2 (CH), 133.6 (C), 139.0 (CH), 148.2 (C), 172.5 (C); LC-MS (ESI): m/z 412.1 [MþNH4]þ. HRMS (EI): m/z calcd for C19H22O7S ([M]þ) 394.1086; found 394.1100. Acknowledgements Financial support of this work by the Deutsche Forschungsgemeinschaft and the DAAD is gratefully acknowledged. Supplementary data Supplementary data (NMR spectra for all new compounds) related to this article can be found at http://dx.doi.org/10.1016/ j.tet.2015.05.095. References and notes 1. Review: Mondal, S. Chem. Rev. 2012, 112, 5339e5355. 2. (a) Mondal, S.; Debnath, S.; Das, B. Tetrahedron 2015, 71, 476e486; (b) Qi, Z.; € ckner, R. Wang, M.; Li, X. Chem. Commun. 2014, 9776e9778; (c) Walleser, P.; Bru Eur. J. Org. Chem. 2014, 3210e3224; (d) Mondal, S.; Debnath, S. Tetrahedron Lett. 2014, 55, 1577e1580; (e) Rad-Moghadam, K.; Roudsari, S. T.; Sheykhan, M. Synlett 2014, 827e830; (f) Gaitzsch, J.; Rogachev, V.; Zahel, M.; Metz, P. Synthesis 2014, 46, 531e536; (g) Ghandi, M.; Taheri, A.; Hasani Bozcheloei, A.; Abbasi, A.; Kia, R. Tetrahedron 2012, 68, 3641e3648; (h) Li, F.; Liu, T.-X.; Wang, G.-W. Org. Lett. 2012, 14, 2176e2179; (i) Li, F.; Jiang, T.; Cai, H.; Wang, G. Chin. J. Chem. 2012, 30, 2041e2046; (j) Ghandi, M.; Hasani Bozcheloei, A.; Nazari, S. H.; Sadeghzadeh, M. J. Org. Chem. 2011, 76, 9975e9982. 3. Reviews: (a) Padwa, A. Tetrahedron 2011, 67, 8057e8072; (b) Padwa, A. Helv. Chim. Acta 2005, 88, 1357e1374; (c) Chiu, P. Pure Appl. Chem. 2005, 77, 1183e1189; (d) Mehta, G.; Muthusamy, S. Tetrahedron 2002, 58, 9477e9504. €ger, A.; 4. Shi, B.; Merten, S.; Wong, D. K. Y.; Chu, J. C. K.; Liu, L. L.; Lam, S. K.; Ja Wong, W.-T.; Chiu, P.; Metz, P. Adv. Synth. Catal. 2009, 351, 3128e3132. 5. Reviews: (a) Merfort, I. Curr. Drug Targets 2011, 12, 1560e1573; (b) Schmidt, T. J. Stud. Nat. Prod. Chem. 2006, 33, 309e392. 6. Angle, S. R.; Choi, I.; Tham, F. S. J. Org. Chem. 2008, 73, 6268e6278. 7. Cahiez, G.; Alexakis, A.; Normant, J. F. Tetrahedron Lett. 1978, 19, 3013e3014. 8. More, J. D.; Finney, N. S. Org. Lett. 2002, 4, 3001e3003. 9. (a) Bal, B. S.; Childers, W. E., Jr.; Pinnick, H. W. Tetrahedron 1981, 37, 2091e2096; (b) Kraus, G. A.; Taschner, M. J. J. Org. Chem. 1980, 45, 1175e1176; (c) Lindgren, B. O.; Nilsson, T. Acta Chem. Scand. 1973, 27, 888e890. 10. Lam, S. K.; Chiu, P. Chem.dEur. J. 2007, 13, 9589e9599.
T. Groß et al. / Tetrahedron 71 (2015) 5925e5931 11. Radosevich, A. T.; Chan, V. S.; Shih, H.-W.; Toste, F. D. Angew. Chem. 2008, 120, 3815e3818 Angew. Chem. Int. Ed. 2008, 47, 3755e3758. 12. Tolochko, L. A.; Sipyagin, A. M.; Kartsev, V. G.; Aliev, Z. G.; Atovmyan, L. O.; Lebedev, A. T. Chem. Heterocycl. Compd. 1988, 24, 370e376. 13. Rondestvedt, C. S., Jr. J. Am. Chem. Soc. 1954, 76, 1926e1929. 14. Reviews: (a) Alonso, D. A.; N ajera, C. Org. React. 2008, 72 367e656; (b) N ajera, C.; Yus, M. Tetrahedron 1999, 55, 10547e10658; (c) Trost, B. M. Bull. Chem. Soc. Jpn. 1988, 61, 107e124. 15. Holmquist, C. R.; Roskamp, E. J. Tetrahedron Lett. 1992, 33, 1131e1134. 16. (a) Plessis, C.; Uguen, D.; De Cian, A.; Fischer, J. Tetrahedron Lett. 2000, 41, 5489e5493; (b) Weatherhead-Kloster, R. A.; Corey, E. J. Org. Lett. 2006, 8, 171e174. 17. (a) Charette, A. B.; Wurz, R. P.; Ollevier, T. J. Org. Chem. 2000, 65, 9252e9254; (b) Wurz, R. P.; Lin, W.; Charette, A. B. Tetrahedron Lett. 2003, 44, 8845e8848.
5931
18. Crystallographic data (excluding structure factors) for the structures in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication nos. CCDC 1042282 (20) and CCDC 1042281 (21). Copies of the data can be obtained, free of charge, on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK, (fax: þ44 (0) 1223 336033 or e-mail: [email protected]). 19. Keller, E. SCHAKAL 99, A Computer Program for the Graphic Representation of Molecular and Crystallographic Models; University of Freiburg: Germany, 1999. 20. Review: Chiu, P.; Lautens, M. Top. Curr. Chem. 1997, 190, 1e85. 21. Lautens, M.; Fillion, E.; Sampat, M. Tetrahedron Lett. 1998, 39, 1501e1504. 22. Ewas, A. M. M.; Dawood, K. M. H.; Spinde, K.; Wang, Y.; J€ ager, A.; Metz, P. Synlett 2009, 1773e1776. 23. Metz, P.; Cramer, E. Tetrahedron Lett. 1993, 34, 6371e6374. 24. Black, T. H. Aldrichimica Acta 1983, 16, 3e10.