An organoantimony complex with intramolecular N → Sb coordination as effective and recyclable catalyst for the allylation of aldehydes with tetraallyltin

Tetrahedron Letters 58 (2017) 2592–2595

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An organoantimony complex with intramolecular N ? Sb coordination as effective and recyclable catalyst for the allylation of aldehydes with tetraallyltin Nianyuan Tan a,⇑, Tong Nie a,b, Chak-Tong Au a,⇑, Donghui Lan a, Shuisheng Wu a, Bing Yi a,b,⇑ a b

College of Chemistry and Chemical Engineering, Hunan Institute of Engineering, Xiangtan 411104, PR China Key Laboratory of Environmentally Friendly Chemistry and Applications, Ministry of Education, School of Chemistry, Xiangtan University, Xiangtan 411105, PR China

a r t i c l e

i n f o

Article history: Received 7 March 2017 Revised 17 May 2017 Accepted 19 May 2017 Available online 19 May 2017 Keywords: Organoantimony Intramolecular coordination Allylation reaction Aldehyde Catalyst recycling

a b s t r a c t An air-stable hypervalent organoantimony (III) triflate complex (PhN(CH2C6H4)2SbOSO2CF3) having intramolecular N ? Sb coordination was synthesized and characterized by techniques such as 1H NMR, 13 C NMR, TG-DSC, X-ray diffraction and elemental analysis. The complex shows relatively strong Lewis acidity (0.8 < Ho  3.3). It exhibits excellent catalytic performance towards the allylation of aldehydes with tetraallyltin at room temperature, and shows good thermal stability and recyclability. The catalytic system enables convenient and efficient synthesis of homoallylic alcohols. Ó 2017 Elsevier Ltd. All rights reserved.

The interest in the chemistry of hypervalent organoantimony compounds with intramolecular E ? Sb (E = N, O, S) coordinations has increased in recent years because of their fascinating chemistry, structure and applications in organic synthesis.1,2 Most of the compounds that contain bidentate or tridentate aryl ligands with one or two ortho-pendant coordinating groups such as 2-(Me2NCH2)C6H4,3,4 2,6-(Me2NCH2)C6H3,5 2,6-(ROCH2)C6H3 (R = Me, t-Bu),6,7 E(CH2C6H4)2 (E = RN, O, S)8,9 and C6H4CH2ECH2C10H6 (E = O, S),10 the so-called C,E or E,C,E and C,E,C-chelating ligands (E = N, O, S) are commonly used to stabilize organoantimony compounds. The applications of these compounds are mainly for organic and biological reactions.1,2 For example, Kakusawa et al. reported the use of organoantimony compounds with intramolecular N ? Sb coordination as efficient agents for cross-coupling, arylation and addition reactions.11–13 Also, organoantimony oxide with intramolecular N ? Sb interaction was synthesized and found to be reversible reagent efficient for CO2 chemical fixation.14 Recently, Chen et al. synthesized, characterized and screened a number of hypervalent organoantimony compounds for anti-proliferative purpose.15 However, the use of the compounds with intramolecular E ? Sb (E = N, O, S) ⇑ Corresponding authors at: College of Chemistry and Chemical Engineering, Hunan Institute of Engineering, Xiangtan 411104, PR China (B. Yi). E-mail addresses: [email protected] (N. Tan), [email protected] (C.-T. Au), [email protected] (B. Yi). http://dx.doi.org/10.1016/j.tetlet.2017.05.069 0040-4039/Ó 2017 Elsevier Ltd. All rights reserved.

coordinations as Lewis acid catalysts in organic synthesis is rare.1,2 In 2010, Yin and coworkers reported the synthesis of an air-stable organoantimony compound bearing intramolecular N ? Sb coordination that can efficiently catalyze the direct diastereoselective Mannich reaction in water, giving anti/syn molar ratio 95/5.16 In the present communication, we report the synthesis and characterization of an analogous air-stable organoantimony triflate complex, and illustrate its use as catalyst for the allylation of aldehydes with tetraallyltin. As shown in Scheme 1, the reaction of PhN(CH2C6H4)2SbCl with one equiv of silver triflate in THF gives organoantimony complex 1.17 The results of NMR and elemental analysis of complex 1 are consistent with its formula. Complex 1 is resistant to moisture and oxygen. It remained intact in air as dry colorless crystals or white powder in a test of six months. In addition, it is highly soluble in methanol and in common polar organic solvents. The crystal structure of complex 1 was confirmed by X-ray analysis in a way similar to that of Ref. 17. An ORTEP representation of the structure, as well as selected bonds and angles are shown in Fig. 1. One can see that the coordination polyhedron around the central antimony atom can be best described as a strongly distorted pseudo-trigonal bipyramid (hypervalent 10-Sb-4 species18), where both the C(1) and C(14) atoms exist at the equatorial positions along with a lone electron pair of antimony, while the N(1) and O(1) atoms are located at the apical positions. The Sb–C(1) and Sb–C(14) distances are 2.1372(17) and 2.1515(17) Å, respec-

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100 THF dark, RT, 4 h

Cl

DSC

N

6 Sb OSO 2CF 3 1

Scheme 1. Synthesis of organoantimony complex 1.

80 4 252 oC 2

DSC / (mv/mg)

+ AgOSO 2CF 3

TG / (%)

N Sb

8

TG

60 0

232 oC 40 200

400

-2 800

600

Temperature / oC Fig. 2. TG-DSC curves of complex 1.

method is 0.8 < Ho  3.3,20,21 much stronger than that (4.8 < Ho  6.8) of the precursor PhN(CH2C6H4)2SbCl, indicating that the incorporation of the strongly electron-withdrawing triflate group to organoantimony compounds can enhance acidity. In addition, the acidity of complex 1 is stronger than that of organoantimony compound C6H11N(CH2C6H4)2Sb(OSO2CF3).16 In view of the acidic property of compound 1, we used it as a Lewis acid catalyst for aldehyde allylation with tetraallyltin, which is one of the most useful methods for the formation of carbon-carbon bonds.22–25 Initial studies were performed using the reaction of benzaldehyde and tetraallyltin at room temperature as model. We examined the effects of solvent and catalyst amount on the yield of the product. As shown in Table 1, high yields (87–96%) are observed when MeOH, EtOH, CH3CN, THF and CH2Cl2 are used as solvent (Table 1, entries 1–5), while much lower yields (20–27%) are detected when Et2O and hexane are used (Table 1, Entries 6, 7). When the catalyst amount is increased from 1 mol% to 4 mol%, the yield increases from 65% to 96%, and then only slightly to 97% when the amount is further increased to 5 mol% (Table 1, entries 1, 8–11). Therefore, we adopted MeOH as solvent and a catalyst amount of 4 mol% for the rest of the investigation. Fig. 1. An ORTEP view showing 50% probability ellipsoids of [PhN(CH2C6H4)2SbOSO2CF3] 1. Selected bonds (Å) and angles (°): Sb–C(1), 2.1372(17); Sb–C(14), 2.1515(17); Sb–N(1), 2.3266(14); Sb–O(1), 2.3364(13); N(1)–C(7), 1.494(2); N(1)–C (8), 1.511(2); C(1)–Sb–C(14), 97.28(6); C(1)–Sb–O(1), 83.96(6); C(14)–Sb–O(1), 87.14(6); C(1)–Sb–N(1), 77.11(6); C(14)–Sb–N(1), 78.94(6); C(7)–N(1)–C(8), 109.59 (13); N(1)–Sb–O(1), 154.74(5).

Table 1 Allylation of PhCHO with tetraallyltin catalyzed by catalyst 1 in various solvents.a

O Ph

tively. The C(1)–Sb–C(14) angle is 97.28(6)° while the N(1)–Sb–O (1) angle is 154.74(5)° (rather than 180°). The Sb(1)–N(1) distance (2.3266(14) Å) is much shorter than the sum of the van der Waals radii of nitrogen and antimony atoms (3.74 Å),19 indicating the existence of strong coordination between N and Sb atoms, and slightly longer than that (2.311(4) Å) in organoantimony compound C6H11N(CH2C6H4)2Sb(OSO2CF3),16 suggesting that the N ? Sb coordination of the latter is slightly stronger than that of the former, as a result the stronger electron-donating ability of the cyclohexyl group in the latter compared with that of phenyl group in the former. The thermal stability of compound 1 was investigated by TGDSC analysis under N2 atmosphere (Fig. 2). The thermogravimetric curves of compound 1 show a weight loss of exothermic nature at 252 °C, plausibly due to the thermal cleavage of organic entities, implying compound 1 is thermally stable roughly up to 250 °C. The acidity of complex 1 as measured by the Hammett indicator

a b c d e f

H

+

1/4

Sn 4

OH

1, 4 mol% solvent, RT

Ph

Entry

Solvent

Time (h)

Yield (%)b

1 2 3 4 5 6 7 8c 9d 10e 11f

MeOH EtOH CH3CN THF CH2Cl2 Et2O Hexane MeOH MeOH MeOH MeOH

1 1 1 1 2 3 6 1 1 1 1

96 90 92 89 87 28 20 65 79 86 97

PhCHO 1 mmol, tetraallyltin 0.3 mmol, Catalyst 0.04 mmol, RT, 2 mL solvent. Isolated yield. 1 mol% catalyst. 2 mol% catalyst. 3 mol% catalyst. 5 mol% catalyst.

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Table 2 Allylation of various aldehydes with tetraallyltin catalyzed by catalyst 1 in MeOH.a

H

+

Sn

1/4

OH

1, 4 mol%

80

R 5a-5o

MeOH, RT

4

Entry

Aldehyde

Product

Time(h)

Yield(%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

PhCHO 4-CH3C6H4CHO 2-CH3C6H4CHO 4-CH3OC6H4CHO 2,4,6-(CH3)3C6H2CHO 4-CF3C6H4CHO 4-NO2C6H4CHO 3-NO2C6H4CHO 2-NO2C6H4CHO 4-ClC6H4CHO 2-ClC6H4CHO 4-BrC6H4CHO PhCH2CH2CHO n-C7H15CHO Furan-2-carbaldehyde

5a 5b 5c 5d 5e 5f 5g 5h 5i 5j 5k 5l 5m 5n 5o

1 1 1 1 3 1 1 1 1 1 1 1 1 1 1

96 93 92 90 78 95 93 97 92 90 92 94 93 90 89

b

a RCHO 1 mmol, tetraallyltin 0.3 mmol, Cat. 0.04 mmol, RT, 2 mL MeOH, all products were characterized by 1H NMR. b Isolated yield.

To explore the application scope of compound 1 as Lewis acid catalyst for allylation of aldehydes with tetraallyltin, various aromatic aldehydes with electron-donating and electron-withdrawing groups as well as aliphatic aldehydes were adopted. One can see that the use of ortho- or para-substituted benzaldehydes with electron-donating or electron-withdrawing groups results in excellent yields of the corresponding homoallylic alcohols (Table 2, entries 1–4, 6–12), except in the case of 2,4,6-trimethylbenzaldehyde only moderate yield is observed even after prolonged reaction time (Table 2, entry 5), possibly due to steric hindrance of the 2,6-substituted groups. In addition, the use of aliphatic aldehydes and furan-2-carbaldehyde (a heteroaromatic aldehyde) afford good yield of the corresponding homoallylic alcohols (Table 2, entries 13–15). We examined the use of compound 1 as Lewis acid catalyst for the allylation of acetophenone and N-(4-nitrobenzylidene)-4methylbenzenesulfonamide (4-NO2PhC = NTs) under the same reaction conditions (data not shown). In the case of acetophenone, only trace amount of product was observed while in the case of 4NO2PhC = NTs, no product was observed after 6 h. It is apparent that compound 1 is not Lewis acidic enough to catalyze the reactions. In Table 3, the catalytic performance of compound 1 was compared with that of organoantimony compound

Table 3 Allylation of PhCHO with tetraallyltin catalyzed by catalyst 1–4 in MeOH.a

O Ph

a b

H

+

1/4

OH

Sn Cat., 4 mol% 4

Ph

MeOH, RT

Entry

Catalysts

Time (h)

Yield (%)b

1 2 3 4

PhN(CH2C6H4)2Sb(OSO2CF3) (1) C6H11N(CH2C6H4)2Sb(OSO2CF3) (2) PhN(CH2C6H4)2SbCl (3) C6H11N(CH2C6H4)2SbCl (4)

1 1 1 1

96 90 56 52

PhCHO 1 mmol, tetraallyltin 0.3 mmol, Cat. 0.04 mmol, RT, 2 mL MeOH. Isolated yield.

Yield (%)

O R

Product Recovered catalyst

100

60

40

20

0 1

2

3

4

5

Recycle Number Fig. 3. Allylation of benzaldehyde with tetraallyltin over recovered catalyst 1.

C6H11N(CH2C6H4)2Sb(OSO2CF3) (2), as well as those of their precursor PhN(CH2C6H4)2SbCl (3) and C6H11N(CH2C6H4)2SbCl (4). The isolated yield of homoallyl alcohol is 90% when compound 2 is used as catalyst, slightly lower than the product yield (96%) when compound 1 is used (Table 3, entries 1, 2). In addition, the use of compound 3 or 4 gives lower yield of the corresponding homoallylic alcohol after 1 h (Table 3, entries 3, 4). The results indicate that compound 1 is superior to the other three in catalytic activity in accordance with their strength of Lewis acidity. To examine reusability, compound 1 was subject to cycles of benzaldehyde allylation with tetraallyltin. In a test of 5 cycles, the change of product yield is minimal (isolated yield slightly declined from 96% to 93%), indicating that the catalyst is stable and reusable (Fig. 3). In conclusion, we have synthesized and characterized an airstable organoantimony compound bearing intramolecular N ? Sb coordination. The compound shows high catalytic activity, stability and reusability for the allylation of aromatic and aliphatic aldehydes with tetraallyltin in methanol at room temperature. Acknowledgments The work was financially supported by the Key Project of Hunan Province Education Department (No. 15A041), and the Open Fund Project of Hunan Province Education Department (No. 15K030). A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.tetlet.2017.05. 069. References 1. Ratß CI, Silvestru C, Breunig HJ. Coord Chem Rev. 2013;257:818–879. 2. Tan NY, Yin SF, Qiu RH, Zhou YB, Au CT. Curr Org Chem. 2012;16:2462–2481. 3. Opris LM, Preda AM, Varga RA, Breunig HJ, Silvestru C. Eur J Inorg Chem. 2009;1187–1193. 4. Copolovici D, Bojan VR, Rat CI, Silvestru A, Breunig HJ, Silvestru C. Dalton Trans. 2010;39:6410–6418. 5. Svoboda T, Jambor R, Ru˚zˇicˇka A, et al. Organometallics. 2012;31:1725–1729. 6. Machucˇa L, Dostál L, Jambor R, et al. J Organomet Chem. 2007;692:3969–3975. 7. Chovancová M, Jambor R, Ru˚zˇicˇka A, Jirásko R, Císarˇová I, Dostál L. Organometallics. 2009;28:1934–1941. 8. Kakusawa N, Tobiyasu Y, Yasuike S, Yamaguchi K, Seki H, Kurita J. Tetrahedron Lett. 2003;44:8589–8592. 9. Kakusawa N, Kurita J. Heterocycles. 2006;68:1335–1348. 10. Tan NY, Chen Y, Yin SF, Qiu RH, Zhou YB, Au CT. Dalton Trans. 2013;42:9476–9481.

N. Tan et al. / Tetrahedron Letters 58 (2017) 2592–2595 11. Kakusawa N, Tobiyasu Y, Yasuike S, Yamaguchi K, Seki H, Kurita J. J Organomet Chem. 2006;691:2953–2968. 12. Kakusawa N, Yasuike S, Kurita J. Heterocycles. 2009;77:1269–1283. 13. Kakusawa N, Yasuike S, Kurita J. Heterocycles. 2010;80:163–168. 14. Dostál L, Jambor R, Ru˚zˇicˇka A, et al. Organometallics. 2009;28:2633–2636. 15. Chen Y, Yu K, Tan NY, et al. Eur J Med Chem. 2014;79:391–398. 16. Xia J, Qiu RH, Yin SF, et al. Organomet Chem. 2010;695:1487–1492. 17. Synthetic procedure for compound 1: PhN(CH2C6H4)2SbCl (0.428 g, 1.0 mmol) was dissolved in 100 mL THF, then a solution of AgOSO2CF3 (0.257 g, 1.0 mmol) in 20 mL THF was added. After the mixture was stirred in the dark at room temperature for 4 h, it was subject to filtration. The filtrate mixed with 10 mL of hexane was refrigerated for 48 h, giving colorless crystals (0.521 g, 96%). Mp: 231–232 °C; 1H NMR (400 MHz, [d6]acetone): d = 7.92 (d, J = 7.2 Hz, 2H; ArH), 7.65 (d, J = 8.0 Hz, 2H; ArH), 7.52–7.43 (m, 8H; ArH), 7.36 (t, J = 7.2, 1H; ArH), 5.16 (d, J = 15.2 Hz, 2H; CH2), 4.92 ppm (d, J = 15.2 Hz, 2H; CH2); 13C NMR (100 MHz, [d6]acetone): d = 148.10 (ArC), 145.49 (ArC), 143.11 (ArC), 134.98 (ArC), 130.86 (ArC), 130.83 (ArC), 130.25 (ArC), 128.33 (ArC), 126.72 (ArC), 121.95 (ArC), 65.02 ppm (CH2); 19F NMR (376 MHz, [d6]acetone): d = 78.58

18. 19. 20. 21. 22. 23. 24. 25.

2595

(CF3); elemental analysis calcd (%) for C21H17F3NO3SSb: C, 46.52; H, 3.16; N, 2.58; Found: C, 46.48; H, 3.19; N, 2.55%. Crystallographic data for 1. PhN (C6H4CH2)2SbOSO2CF3, colorless block, formula weight 542.17, Triclinic, P-1, a = 9.61940(10), b = 9.72810(10), c = 11.3235(2), V = 1029.98(2), Z = 2, Dcalc = 1.748 g cm 3, l (Mo Ka) = 1.490 [mm 1]. F(0 0 0) = 536, reflections collected = 11770, unique = 4715, R(int) = 0.0127, full-matrix least-squares on F2, parameters = 271. Final indices R1 = 0.0161, wR2 = 0.0437 for 4615 reflections with I > 2r(I), goodness-of-fit on F2 = 1.174, largest difference in peak and hole (0.429 and 0.499 e Å 3). CCDC 1535931. Akiba KY. In: Akiba KY, ed. Chemistry of Hypervalent Compounds. Weinheim: Wiley-VCH; 1999:1–8. Batsanov SS. Inorg Mater. 2001;37:871–885. Benesi HA. J Am Chem Soc. 1956;78:5490–5494. Benesi HA. J Phys Chem. 1957;61:970–973. Qiu RH, Zhang GP, Zhu YY, et al. Chem Eur J. 2009;15:6488–6494. Zhang XW, Qiu RH, Tan NY, et al. Tetrahedron Lett. 2010;51:153–156. Galletti P, Moretti F, Samorì C, Tagliavini E. ChemSusChem. 2009;2:1045–1050. Jin YZ, Yasuda N, Furuno H, Inanaga J. Tetrahedron Lett. 2003;44:8765–8768.