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Copper-catalyzed synthesis of aryl and alkyl trifluoromethyl sulfides using CF3SiMe3 and Na2S2O3 as –SCF3 source
Tetrahedron Letters 55 (2014) 4909–4911
Contents lists available at ScienceDirect
Tetrahedron Letters journal homepage: www.elsevier.com/locate/tetlet
Copper-catalyzed synthesis of aryl and alkyl trifluoromethyl sulfides using CF3SiMe3 and Na2S2O3 as –SCF3 source Wei Zhong a,b,⇑, Xiaoming Liu a a b
College of Biological, Chemical Sciences and Engineering, Jiaxing University, Jiaxing 314001, Zhejiang, China State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, Jiangsu, China
a r t i c l e
i n f o
Article history: Received 1 May 2014 Revised 6 July 2014 Accepted 10 July 2014 Available online 15 July 2014 Keywords: Trifluoromethylthiolation Copper catalysis Trifluoromethylthio group One-pot reaction
a b s t r a c t A universal and efficient Cu(I)-catalyzed synthesis of aryl and alkyl trifluoromethyl sulfides has been developed. In this catalytic system, S-aryl or S-alkyl sulfothioate (I or II) proved to be the key intermediate. Substrates bearing groups of I, Br, Cl, OTs, and OMs on the aryl carbon and no matter electronwithdrawing and electron-donating substitutions on the aromatic ring could afford good to excellent yields. Ó 2014 Elsevier Ltd. All rights reserved.
Developing novel synthetic approaches for fluorinated derivatives is of long-standing interest to chemists in a variety of fields.1 As an important member in this family, the trifluoromethylthio group (–SCF3) has attracted increasing attention in the past decades because of the biological potentials of the compounds containing this group2 and its strong electron-withdrawing effect (with large Hansch lipophilicity parameter, pR = 1.44).3 Over the past few decades, two general strategies for introducing the –SCF3 group into organic molecules have been developed, direct and indirect insertions (Scheme 1). In the direct strategy, both metal complexes MSCF3 (M = Cu, Ag, Hg)4 and organic species (R1R2NSCF3,5 ROSCF3,6 [R4N]+[SCF3] ,7 RSO2CF3,8 ROCOSCF3,9 F3CSSCF3,10 F3CSCl11) have been used as –SCF3 sources. The shortcomings of these –SCF3 sources are either expensive or highly toxic and/or instable, which limit their further applications. In the indirect one, the first example was reported by Chen and coworkers using sulfur and FSO2CF2CO2Me as –SCF3 source.12 Very recently, elemental sulfur and CF3SiMe3 were successfully used to introduce the –SCF3 group by Qing’s group,13 While Li and co-workers used sodium trifluoroacetate and elemental sulfur to achieve the trifluoromethylthiolation process.14 The latest way reported by Goossen and co-workers employed arenediazonium salts and sodium thiocyanate to prepare the corresponding aryl trifluoromethyl thioethers.15 But these approaches were applied only to limited starting substrates, such as aryl iodide,12 aryl boronic acids,13a,14 ⇑ Corresponding author. Tel.: +86 573 83640303; fax: +86 573 83643937. E-mail address: [email protected] (W. Zhong). http://dx.doi.org/10.1016/j.tetlet.2014.07.039 0040-4039/Ó 2014 Elsevier Ltd. All rights reserved.
S8 + FSO2CF2 CO 2Me (Ref. 12)
MSCF 3 M = Cu, Ag, Hg
S8 + CF3 SiMe3 (Ref. 13)
(Ref. 4) Direct 'SCF3'
Ar SCF3 Alk SCF3
Indirect
S8 + CF3 CO 2Na (Ref. 14) N 2+
'SCF3 ' NaSCN + R
RnXSCF3 X = C, O, N, S, Cl, I (Ref. 5~11)
BF 4- (Ref. 15)
Na2 S2O 3 + CF3 SiMe 3 (this paper)
Scheme 1. Strategies for the preparation of trifluoromethyl sulfides.
terminal alkynes,13b and arylamine.15 Thus, developing a universal and efficient method to introduce the –SCF3 group into various substrates is highly desirable. Inspired by Reeves’ and Jiang’s recent work, which used Na2S2O3 as sulfurating reagent to construct a C–S bond,16 we attempted to employ the same sulfurating reagent to achieve trifluoromethylthiolation. Herein, we report an efficient Cu(I)-catalyzed synthesis of aryl and alkyl trifluoromethyl sulfides using CF3SiMe3 and Na2S2O3 as the indirect –SCF3 source. We began our investigation by reacting bromobenzene 1a1 with Na2S2O3 and CF3SiMe3 in the presence of different copper salts, bases, and solvents to optimize the reaction conditions. To our delight, when the reaction was conducted with CuCl (0.05 equiv) and 1,10-phenanthroline (Phen; 0.05 equiv) in the presence of K2CO3 as the base in DMSO at 80 °C, 2a was formed in 42% yield (Table 1, entry 1). Our investigation turned out that a base plays a crucial role in the reaction and no product was detected without
4910
W. Zhong, X. Liu / Tetrahedron Letters 55 (2014) 4909–4911
Table 1 Optimization of Cu(I)-catalyzed synthesis of trifluoromethyl sulfides Br
SCF3
[Cu], Phen Na 2S2 O3
CF3SiMe 3 Base, DMSO
1a 1
2a
Entrya
Cat: [Cu]
Base
Yieldc
1 2 3 4 5 6 7 8 9 10 11 12b
CuCl CuCl CuCl CuCl CuCl CuCl2 CuBr CuOAc CuOTf — CuCl CuCl
K2CO3 Na2CO3 KOAc K3PO4 KOH K3PO4 K3PO4 K3PO4 K3PO4 K3PO4 — K3PO4
42% 26% 51% 83% <5% 58% 75% 63% 69% 0 0 81%
a Reaction conditions: 1a1 (0.2 mmol), Na2S2O3 (0.21 mmol), CF3SiMe3 (0.4 mmol), base (0.3 mmol), catalyst/ligand (5 mol %), DMSO (2 mL), 24 h, 80 °C in air. b Standard reaction stirring under inert Ar atmosphere. c Isolated yield.
the presence of a base (Table 1, entry 11). Among the examined bases, K3PO4 shows the best performance, which increases the reaction yield to 83% (Table 1, entries 2–4). When KOH was used, the reaction proceeds hardly (<5%, entry 5). Contrary to the influence of the base, the copper salts possess almost no affection on the reaction (entries 6–9). The use of other solvents and ligands, increasing the amount of loading catalyst, changes in reaction temperature (Supporting information, SI-Tables 1 and 2), or carrying out the standard reaction under inert Ar atmosphere (Table 1, entry 12), led no significant improvement on the yield. The approach exhibits its applicability to various substrates. Under the optimized reaction conditions (Table 1, entry 4), the – SCF3 group was successfully introduced into a wide range of
Ar
CuCl, Phen
X Na 2S2 O3
Alk X
Ar
CF3 SiMe 3
SCF3
Alk SCF3
K3PO4 , DMSO
1
2 SCF3
SCF3
SCF 3
H3 CO 2a X = Br, I, Cl, OTs, OMs 83%, 91%, 74%, 71%, 68%
2b, X = I, 88%
O 2N
NC
Ph
2c, X = I, 92%
SCF3
SCF3
2e, X = I, 63%
2d, X = I, 72%
SCF 3
H 3COC
2f, X = I, 58%
SCF3
2g, X = I, 65%
SCF3
substrates (Scheme 2). Substrates bearing groups of I, Br, Cl, OTs, and OMs on the aryl carbon could afford good yields (2a, Scheme 2). Both the electronic nature and position of a substituent on the aromatic ring affect the reaction. An electron-withdrawing group can lower the reaction yield. But a decent yield was still obtained even when a strong electron-withdrawing group like the –NO2 group was present. As shown in Scheme 2, an ortho-substituent exercises more profound effect on the reaction compared to a meta- and para-substituent. This is certainly due to steric reason. When a t butyl is present at the ortho position, the reaction did not occur (2l, Scheme 2) at all due to the steric hindrance caused by its bulkiness. The universal applications of this approach are further supported by the success in both heterocyclic and aliphatic iodides (2r–2w, Scheme 2). To gain some insight of the reaction mechanism and understand the roles of each component in the transformation, control experiments were performed (Scheme 3, SI-3). Reacting 1a2 with Na2S2O3 in DMSO catalyzed by CuCl and 1,10-phenanthroline (Phen) under air, the intermediate I16b was isolated in 75% yield. Further reaction of this isolated intermediate I with CF3SiMe3 led to the desired product 2a in 88% yield under the optimized reaction conditions. Again, no 2a was detected without the base in the reaction system. Furthermore, when two normal radical-trapping reagents, TEMPO and 1,1-diphenylethene, were employed under standard conditions, desired 2a was afforded in 81% and 85%, respectively. These results suggested that K3PO4 takes its action in the process, in which it may be to cleave off the C–Si bond in CF3SiMe3 but not to form CF3 radical assembling into the final product.17 Finally, iodocyclohexane 1t showed more activity than 1a2, affording excellent yield of II16b in the absence of catalyst. On the basis of our preliminary results and previous related studies,4–15 it is clear that the installation of the –SCF3 group takes place stepwise. In the first step, the intermediate I or II was formed via nucleophilic attack on the cationic carbon of substrate 1 by thiosulfate.16b When the carbocation can be well stabilized, the reaction may not need the catalyst at all, for example, in the case of iodocyclohexane (1t, Scheme 3). In the second step, the conjunction of leaving of the SO23 group and cleavage of the C–Si bond in CF3SiMe3 affords the desired product 2 catalyzed by CuCl/Phen in the presence of K3PO4.17 In summary, we have developed an approach for trifluoromethylthiolation of aryl or alkyl iodide using readily available reagents Na2S2O3 (as sulfur source) and CF3SiMe3 in one-pot reaction under the catalysis of Cu(I)/Phen system. The reaction proceeds in two steps and the S-aryl or S-alkyl sulfothioate (I or II) is the key intermediate. The approach exhibits excellent suitability to a wide range of substrates with decent yield and may have great potential in both pharmaceutical and agrochemical industries.
OCH 3 2h, X = I, 78%
O
Ph 2i, X = I, 68%
SCF 3
SCF3
SCF3
COOCH3
NO2 2j, X = I, 74%
2k, X = I, 55%
SCF3
SCF3
SCF3
SCF3
I Na2 S2O3
tBu 2l, X = I, 0%
I
SCF3
CuCl, Phen
CuCl, Phen
Cl
CONH 2 2n, X = I, 49%
SCF3
Cl 2q, X = I, 53% SCF 3
Ph 2u, X = I, 88%
OCH 3 2o, X = I, 86%
2r, X = I, 79%
I + Na2 S2O3
SCF3
2s, X = I, 65%
SCF3 H 3C(H 2C)9 H 2C 2v, X = I, 81%
DMSO
2p, X = I, 84% SCF3
S
I + CF3 SiMe3
2a, 88% Base, DMSO
SCF3 N
O
Cat, Necessary!
1a2
I + CF3 SiMe3 CN 2m, X = I, 68%
S S ONa
CuCl, Phen,DMSO
1t
2t, X = I, 93%
NC(H 2C)3 H2 C 2w, X = I, 75%
Scheme 2. Scope of the aryl or alkyl substrates.
SCF3
2a, 85%
S
DMSO do not need Cu-Cat
1,1-diphenylethene standard conditions
SO3 Na
CF3SiMe3 , CuCl 2t Phen, Base, DMSO
II TEMPO
1a 1 + Na2 S2O 3 + CF3SiMe 3
2a, 81% standard conditions
Scheme 3. Control experiments.
W. Zhong, X. Liu / Tetrahedron Letters 55 (2014) 4909–4911
Acknowledgments We thank the National Natural Science Foundation of China (21301071 and 21171073), the Natural Science Foundation of Zhejiang Province (LQ13B010002), and the Government of Zhejiang Province (Qianjiang professorship for X.L.) for supporting this work.
5.
Supplementary data Supplementary data (detailed experimental procedures for trifluoromethylthiolation reactions and characterization of the products) associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.tetlet.2014.07.039. References and notes 1. (a) Purser, S.; Moore, P. R.; Swallow, S.; Gouverneur, V. Chem. Soc. Rev. 2008, 37, 320–330; (b) O’Hagan, D. Chem. Soc. Rev. 2008, 37, 308–319; (c) Yamazaki, T.; Taguchi, T.; Ojima, I. Fluorine in Medicinal Chemistry and Chemical Biology; Wiley-Black-well: Chichester, 2009; (d) Cametti, M.; Crousse, B.; Metrangolo, P.; Milani, R.; Resnati, G. Chem. Soc. Rev. 2012, 41, 31–42; (e) Li, Y. Acc. Chem. Res. 2012, 45, 723–733. 2. (a) Leo, A.; Hansch, C.; Elkins, D. Chem. Rev. 1971, 71, 525–616; (b) Leroux, F.; Jeschke, P.; Schlosser, M. Chem. Rev. 2005, 105, 827–856. 3. Hansch, C.; Leo, A.; Taft, R. W. Chem. Rev. 1991, 91, 165–195. 4. (a) Man, E. H.; Coffman, D. D.; Muetterties, E. L. J. Am. Chem. Soc. 1959, 81, 3575–3577; (b) Downse, A. J.; Ebsworth, A. V.; Emeleus, H. J. J. Chem. Soc. 1961, 3187–3192; (c) Harr, J. F. J. Org. Chem. 1967, 32, 2063–2074; (d) Yagupolskii, L. M.; Kondratenko, N. V.; Sambur, V. P. Synthesis 1975, 721–723; (e) Remy, D. C.; Rittle, K. E.; Hunt, C. A.; Freedman, M. B. J. Org. Chem. 1976, 41, 1644–1646; (f) Kondratenko, N. V.; Sambur, V. P.; Yagupolskii, L. M. Synthesis 1985, 667–669; (g) Clark, J. H.; Jones, C. W.; Kybett, A. P.; Mcclinton, M. A. J. Fluorine Chem. 1990, 48, 249–253; (h) Munavalli, S.; Hassner, A.; Rossman, D. I.; Singh, S.; Rohrbaugh, D. K.; Ferguson, C. P. J. Fluorine Chem. 1995, 73, 7–11; (i) Munavalli, S.; Rossman, D. I.; Rohrbaugh, D. K.; Ferguson, C. P.; Durst, H. D. J. Fluorine Chem. 1996, 76, 7–13; (j) Adams, D. J.; Clark, J. H. J. Org. Chem. 2000, 65,
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Contents lists available at ScienceDirect
Tetrahedron Letters journal homepage: www.elsevier.com/locate/tetlet
Copper-catalyzed synthesis of aryl and alkyl trifluoromethyl sulfides using CF3SiMe3 and Na2S2O3 as –SCF3 source Wei Zhong a,b,⇑, Xiaoming Liu a a b
College of Biological, Chemical Sciences and Engineering, Jiaxing University, Jiaxing 314001, Zhejiang, China State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, Jiangsu, China
a r t i c l e
i n f o
Article history: Received 1 May 2014 Revised 6 July 2014 Accepted 10 July 2014 Available online 15 July 2014 Keywords: Trifluoromethylthiolation Copper catalysis Trifluoromethylthio group One-pot reaction
a b s t r a c t A universal and efficient Cu(I)-catalyzed synthesis of aryl and alkyl trifluoromethyl sulfides has been developed. In this catalytic system, S-aryl or S-alkyl sulfothioate (I or II) proved to be the key intermediate. Substrates bearing groups of I, Br, Cl, OTs, and OMs on the aryl carbon and no matter electronwithdrawing and electron-donating substitutions on the aromatic ring could afford good to excellent yields. Ó 2014 Elsevier Ltd. All rights reserved.
Developing novel synthetic approaches for fluorinated derivatives is of long-standing interest to chemists in a variety of fields.1 As an important member in this family, the trifluoromethylthio group (–SCF3) has attracted increasing attention in the past decades because of the biological potentials of the compounds containing this group2 and its strong electron-withdrawing effect (with large Hansch lipophilicity parameter, pR = 1.44).3 Over the past few decades, two general strategies for introducing the –SCF3 group into organic molecules have been developed, direct and indirect insertions (Scheme 1). In the direct strategy, both metal complexes MSCF3 (M = Cu, Ag, Hg)4 and organic species (R1R2NSCF3,5 ROSCF3,6 [R4N]+[SCF3] ,7 RSO2CF3,8 ROCOSCF3,9 F3CSSCF3,10 F3CSCl11) have been used as –SCF3 sources. The shortcomings of these –SCF3 sources are either expensive or highly toxic and/or instable, which limit their further applications. In the indirect one, the first example was reported by Chen and coworkers using sulfur and FSO2CF2CO2Me as –SCF3 source.12 Very recently, elemental sulfur and CF3SiMe3 were successfully used to introduce the –SCF3 group by Qing’s group,13 While Li and co-workers used sodium trifluoroacetate and elemental sulfur to achieve the trifluoromethylthiolation process.14 The latest way reported by Goossen and co-workers employed arenediazonium salts and sodium thiocyanate to prepare the corresponding aryl trifluoromethyl thioethers.15 But these approaches were applied only to limited starting substrates, such as aryl iodide,12 aryl boronic acids,13a,14 ⇑ Corresponding author. Tel.: +86 573 83640303; fax: +86 573 83643937. E-mail address: [email protected] (W. Zhong). http://dx.doi.org/10.1016/j.tetlet.2014.07.039 0040-4039/Ó 2014 Elsevier Ltd. All rights reserved.
S8 + FSO2CF2 CO 2Me (Ref. 12)
MSCF 3 M = Cu, Ag, Hg
S8 + CF3 SiMe3 (Ref. 13)
(Ref. 4) Direct 'SCF3'
Ar SCF3 Alk SCF3
Indirect
S8 + CF3 CO 2Na (Ref. 14) N 2+
'SCF3 ' NaSCN + R
RnXSCF3 X = C, O, N, S, Cl, I (Ref. 5~11)
BF 4- (Ref. 15)
Na2 S2O 3 + CF3 SiMe 3 (this paper)
Scheme 1. Strategies for the preparation of trifluoromethyl sulfides.
terminal alkynes,13b and arylamine.15 Thus, developing a universal and efficient method to introduce the –SCF3 group into various substrates is highly desirable. Inspired by Reeves’ and Jiang’s recent work, which used Na2S2O3 as sulfurating reagent to construct a C–S bond,16 we attempted to employ the same sulfurating reagent to achieve trifluoromethylthiolation. Herein, we report an efficient Cu(I)-catalyzed synthesis of aryl and alkyl trifluoromethyl sulfides using CF3SiMe3 and Na2S2O3 as the indirect –SCF3 source. We began our investigation by reacting bromobenzene 1a1 with Na2S2O3 and CF3SiMe3 in the presence of different copper salts, bases, and solvents to optimize the reaction conditions. To our delight, when the reaction was conducted with CuCl (0.05 equiv) and 1,10-phenanthroline (Phen; 0.05 equiv) in the presence of K2CO3 as the base in DMSO at 80 °C, 2a was formed in 42% yield (Table 1, entry 1). Our investigation turned out that a base plays a crucial role in the reaction and no product was detected without
4910
W. Zhong, X. Liu / Tetrahedron Letters 55 (2014) 4909–4911
Table 1 Optimization of Cu(I)-catalyzed synthesis of trifluoromethyl sulfides Br
SCF3
[Cu], Phen Na 2S2 O3
CF3SiMe 3 Base, DMSO
1a 1
2a
Entrya
Cat: [Cu]
Base
Yieldc
1 2 3 4 5 6 7 8 9 10 11 12b
CuCl CuCl CuCl CuCl CuCl CuCl2 CuBr CuOAc CuOTf — CuCl CuCl
K2CO3 Na2CO3 KOAc K3PO4 KOH K3PO4 K3PO4 K3PO4 K3PO4 K3PO4 — K3PO4
42% 26% 51% 83% <5% 58% 75% 63% 69% 0 0 81%
a Reaction conditions: 1a1 (0.2 mmol), Na2S2O3 (0.21 mmol), CF3SiMe3 (0.4 mmol), base (0.3 mmol), catalyst/ligand (5 mol %), DMSO (2 mL), 24 h, 80 °C in air. b Standard reaction stirring under inert Ar atmosphere. c Isolated yield.
the presence of a base (Table 1, entry 11). Among the examined bases, K3PO4 shows the best performance, which increases the reaction yield to 83% (Table 1, entries 2–4). When KOH was used, the reaction proceeds hardly (<5%, entry 5). Contrary to the influence of the base, the copper salts possess almost no affection on the reaction (entries 6–9). The use of other solvents and ligands, increasing the amount of loading catalyst, changes in reaction temperature (Supporting information, SI-Tables 1 and 2), or carrying out the standard reaction under inert Ar atmosphere (Table 1, entry 12), led no significant improvement on the yield. The approach exhibits its applicability to various substrates. Under the optimized reaction conditions (Table 1, entry 4), the – SCF3 group was successfully introduced into a wide range of
Ar
CuCl, Phen
X Na 2S2 O3
Alk X
Ar
CF3 SiMe 3
SCF3
Alk SCF3
K3PO4 , DMSO
1
2 SCF3
SCF3
SCF 3
H3 CO 2a X = Br, I, Cl, OTs, OMs 83%, 91%, 74%, 71%, 68%
2b, X = I, 88%
O 2N
NC
Ph
2c, X = I, 92%
SCF3
SCF3
2e, X = I, 63%
2d, X = I, 72%
SCF 3
H 3COC
2f, X = I, 58%
SCF3
2g, X = I, 65%
SCF3
substrates (Scheme 2). Substrates bearing groups of I, Br, Cl, OTs, and OMs on the aryl carbon could afford good yields (2a, Scheme 2). Both the electronic nature and position of a substituent on the aromatic ring affect the reaction. An electron-withdrawing group can lower the reaction yield. But a decent yield was still obtained even when a strong electron-withdrawing group like the –NO2 group was present. As shown in Scheme 2, an ortho-substituent exercises more profound effect on the reaction compared to a meta- and para-substituent. This is certainly due to steric reason. When a t butyl is present at the ortho position, the reaction did not occur (2l, Scheme 2) at all due to the steric hindrance caused by its bulkiness. The universal applications of this approach are further supported by the success in both heterocyclic and aliphatic iodides (2r–2w, Scheme 2). To gain some insight of the reaction mechanism and understand the roles of each component in the transformation, control experiments were performed (Scheme 3, SI-3). Reacting 1a2 with Na2S2O3 in DMSO catalyzed by CuCl and 1,10-phenanthroline (Phen) under air, the intermediate I16b was isolated in 75% yield. Further reaction of this isolated intermediate I with CF3SiMe3 led to the desired product 2a in 88% yield under the optimized reaction conditions. Again, no 2a was detected without the base in the reaction system. Furthermore, when two normal radical-trapping reagents, TEMPO and 1,1-diphenylethene, were employed under standard conditions, desired 2a was afforded in 81% and 85%, respectively. These results suggested that K3PO4 takes its action in the process, in which it may be to cleave off the C–Si bond in CF3SiMe3 but not to form CF3 radical assembling into the final product.17 Finally, iodocyclohexane 1t showed more activity than 1a2, affording excellent yield of II16b in the absence of catalyst. On the basis of our preliminary results and previous related studies,4–15 it is clear that the installation of the –SCF3 group takes place stepwise. In the first step, the intermediate I or II was formed via nucleophilic attack on the cationic carbon of substrate 1 by thiosulfate.16b When the carbocation can be well stabilized, the reaction may not need the catalyst at all, for example, in the case of iodocyclohexane (1t, Scheme 3). In the second step, the conjunction of leaving of the SO23 group and cleavage of the C–Si bond in CF3SiMe3 affords the desired product 2 catalyzed by CuCl/Phen in the presence of K3PO4.17 In summary, we have developed an approach for trifluoromethylthiolation of aryl or alkyl iodide using readily available reagents Na2S2O3 (as sulfur source) and CF3SiMe3 in one-pot reaction under the catalysis of Cu(I)/Phen system. The reaction proceeds in two steps and the S-aryl or S-alkyl sulfothioate (I or II) is the key intermediate. The approach exhibits excellent suitability to a wide range of substrates with decent yield and may have great potential in both pharmaceutical and agrochemical industries.
OCH 3 2h, X = I, 78%
O
Ph 2i, X = I, 68%
SCF 3
SCF3
SCF3
COOCH3
NO2 2j, X = I, 74%
2k, X = I, 55%
SCF3
SCF3
SCF3
SCF3
I Na2 S2O3
tBu 2l, X = I, 0%
I
SCF3
CuCl, Phen
CuCl, Phen
Cl
CONH 2 2n, X = I, 49%
SCF3
Cl 2q, X = I, 53% SCF 3
Ph 2u, X = I, 88%
OCH 3 2o, X = I, 86%
2r, X = I, 79%
I + Na2 S2O3
SCF3
2s, X = I, 65%
SCF3 H 3C(H 2C)9 H 2C 2v, X = I, 81%
DMSO
2p, X = I, 84% SCF3
S
I + CF3 SiMe3
2a, 88% Base, DMSO
SCF3 N
O
Cat, Necessary!
1a2
I + CF3 SiMe3 CN 2m, X = I, 68%
S S ONa
CuCl, Phen,DMSO
1t
2t, X = I, 93%
NC(H 2C)3 H2 C 2w, X = I, 75%
Scheme 2. Scope of the aryl or alkyl substrates.
SCF3
2a, 85%
S
DMSO do not need Cu-Cat
1,1-diphenylethene standard conditions
SO3 Na
CF3SiMe3 , CuCl 2t Phen, Base, DMSO
II TEMPO
1a 1 + Na2 S2O 3 + CF3SiMe 3
2a, 81% standard conditions
Scheme 3. Control experiments.
W. Zhong, X. Liu / Tetrahedron Letters 55 (2014) 4909–4911
Acknowledgments We thank the National Natural Science Foundation of China (21301071 and 21171073), the Natural Science Foundation of Zhejiang Province (LQ13B010002), and the Government of Zhejiang Province (Qianjiang professorship for X.L.) for supporting this work.
5.
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