Reusable and efficient CoCl₂ ·6H₂O/cationic 2,2’-bipyridyl system-catalyzed S-arylation of aryl halides with thiols in water under air

Abstract

A CoCl₂·6H₂O/cationic 2,2’-bipyridyl system was proven to be an efficient and reusable catalyst for the coupling of aryl halides with thiols in water under aerobic conditions, leading to the formation of thioethers. Aryl iodides and bromides could couple with various thiols giving the corresponding thioethers using only a 3 mol% catalyst loading in the presence of 1 equiv KOH and 1.5 equiv Zn at 100 °C. For aryl chlorides, reaction at 140 °C and prolongation of the reaction time was performed. After reaction, the residual aqueous solution could be reused several times without any additional treatment and regeneration, making this cobalt-catalyzed S-arylation reaction greener.

---

Introduction

The importance of aryl sulfide moieties stems from their usefulness in biological, pharmaceutical, and material science applications.¹ In modern organic synthesis, transition-metal-catalyzed cross-coupling of aryl halides and thiols for the formation of aryl sulfides is one of the most powerful tools.²Catalysts Cu,³Pd,⁴Ni,⁵ and Fe⁶ are widely employed for this coupling reaction. The use of inexpensive Co as a catalyst for C–S coupling, however, is still rare. Recently, Cheng’s group found that CoI₂(dppe) can catalyze aryl–sulfur bond formation in CH₃CN using Zn as the reductant.⁷ This method represents the missing link for the well-documented first-series transition-metal catalyzed S-arylation between Fe and Cu.

The development of environmentally-benign catalytic systems, in particular using water as the reaction medium, has attracted much attention in recent years due to this green solvent being cheap, nontoxic, safe, and environmentally-benign as compared with organic solvents.⁸ Furthermore, the easy separation of the catalyst-containing aqueous solution from the organic products enables reuse of the catalyst. Although several transition-metals, such as Cu⁹ and Fe¹⁰, have been proven to be reusable catalysts for S-arylation using water as the solvent, this cross-coupling reaction catalyzed by cobalt in water under air has yet to be developed, and the design of a greener and reusable cobalt-containing catalyst for S-arylation as an alternative protocol to complement other metal-catalyzed systems is considered of high practical value.

We have recently reported the combination of a water-soluble cationic 2,2’-bipyridyl ligand 1 and FeCl₃^.6H₂O as a reusable catalytic system for the coupling of aryl iodides and thiols.¹⁰ Herein, we report that the replacement of iron by cobalt to associate with 1 was a reusable and efficient catalyst for the C–S bond-forming reaction of aryl halides, not only aryl iodides but also bromides and chlorides, with thiols in water under aerobic conditions by an operationally-simple procedure without the use of any air- or moisture-sensitive reagents (Scheme 1).

Scheme 1 Cobalt-catalyzed S-arylation in water.

Experimental

General

Chemicals were purchased from commercial suppliers and were used without further purification. The cationic 2,2’-bipyridyl ligand was prepared according to the published procedures.¹¹ Melting points were recorded using melting point apparatus and were uncorrected. All ¹H and ¹³C NMR spectra were recorded in CDCl₃ at 25 °C on a Varian 200 or Bruker 400 NMR spectrometer. GC analysis was performed on a SHIMADZU GC-14B equipped with a fused silica capillary column. Elemental analyses were performed and high-resolution mass spectra (HRMS) were recorded at the Instrument Center Service, National Science Council of Taiwan. All known S-arylation products obtained were pure, and their spectra (¹H, and ¹³C NMR) are given in the ESI.†

Typical procedure for the cobalt-catalyzed S-arylation reaction

A 20 mL reaction tube was charged with CoCl₂·6H₂O (0.03 mmol), 1 (0.03 mmol), and H₂O (5 mL). After stirring the solution at room temperature for 10 min, aryl halide (1.2 mmol), thiol (1.0 mmol), KOH (1.0 mmol), and Zn (1.5 mmol) were added. The reaction mixture was stirred at 100 °C under air for 24 h (aryl iodide, see Table 1 and 2) or 48 h (aryl bromide, see Table 3). In the case of aryl chloride, the reaction vessel was sealed under air by a Teflon-coated screw cap and stirred at 140 °C for 72 h (see Table 4). After cooling the reaction mixture to room temperature, the aqueous solution was extracted with hexane or EtOAc, the organic phase was dried over MgSO₄, and the solvent was then removed under vacuum. Column chromatography on silica gel afforded the desired product.

Table 1 Cobalt-catalyzed coupling of iodobenzene 2a and thiophenol 3a under different conditions^a

Entry	[M]/1 (mol%)	Base (mmol)	Zn (mmol)	Yield (%)^b
a Reaction conditions: 2a (1.2 mmol), 3a (1.0 mmol), [M]/1, Zn (1.5 mmol), KOH (1.0 mmol), and H2O (5 mL) at 100 °C for 24 h. b GC yields. Isolated yields are given in parentheses. c Reaction time was 12 h. d 2,2’-Bipyridyl was used as the ligand. e In the absence of ligand 1. f 99.999% purity CoCl2^.6H2O was used.
1	CoCl2^.6H2O (3)	KOH (1)	–	42 (34)
2	CoCl2^.6H2O (3)	KOH (1)	1.0	58 (47)
3	CoCl2^.6H2O (3)	KOH (1)	1.5	99 (94)
4	CoCl2^.6H2O (3)	KOH (2)	1.5	88 (79)
5	CoCl2^.6H2O (2)	KOH (1)	1.5	80 (75)
6	CoCl2^.6H2O (4)	KOH (1)	1.5	99 (93)
7^c	CoCl2^.6H2O (3)	KOH (1)	1.5	69 (60)
8^d	CoCl2^.6H2O (3)	KOH (1)	1.5	49 (43)
9^e	CoCl2^.6H2O (3)	KOH (1)	1.5	33 (27)
10	CoCl2^.6H2O (3)	K2CO3 (1)	1.5	90 (80)
11	CoCl2^.6H2O (3)	Cs2CO3 (1)	1.5	59 (52)
12	CoCl2^.6H2O (3)	Na2CO3 (1)	1.5	15
13	CoCl2^.6H2O (3)	K3PO4 (1)	1.5	55 (45)
14	CoCl2^.6H2O (3)	CsF (1)	1.5	81 (74)
15	CoCl2^.6H2O (3)	KF (1)	1.5	71 (62)
16	Co(NO3)2^.6H2O (3)	KOH (1)	1.5	73 (58)
17^f	CoCl2^.6H2O (3)	KOH (1)	1.5	98 (92)
18	CuO (0.01)	KOH (1)	1.5	10
19	Cu2O (0.01)	KOH (1)	1.5	9
20	PdCl2(NH3)2 (0.01)	KOH (1)	1.5	5
21	CuCl2 (0.01)	KOH (1)	1.5	0
22	CuCl (0.01)	KOH (1)	1.5	0
23	PdCl2 (0.01)	KOH (1)	1.5	0

---

Table 2 CoCl₂·6H₂O/1-catalyzed S-arylation of aryl iodides and thiols in water^a

Entry	Aryl iodide (2	Thiol (3	Yield (%)^b
a Reaction conditions: 2 (1.2 mmol), 3 (1.0 mmol), CoCl2^.6H2O/1 (3 mol%), KOH (1.0 mmol), Zn (1.5 mmol), and H2O (5 mL) at 100 °C for 24 h. b Isolated yields.
1	2a	3b	4b, 72
2	2a	3c	4c, 91
3	2a	3d	4d, 71
4	2b	3a	4e, 99
5	2b	3b	4f, 84
6	2c	3a	4g, 85
7	2c	3b	4h, 84
8	2c	3c	4i, 90
9	2c	3d	4j, 74
10	2d	3a	4k, 99
11	2d	3b	4l, 92
12	2e	3a	4m, 77
13	2e	3b	4n, 71
14	2f	3a	4o, 95
15	2f	3b	4p, 89
16	2g	3a	4q, 83
17	2g	3b	4r, 85
18	2h	3a	4s, 81
19	2i	3a	4t, 72
20	2a	3e	4u, 44
21	2b	3e	4v, 50
22	2a	3f	4w, 33
23	2b	3f	4x, 51
24	2c	3f	4y, 30

---

Table 3 CoCl₂^.6H₂O/1-catalyzed S-arylation of aryl bromides and thiols in water^a

Entry	Aryl bromide (5	Thiol (3	Yield (%)^b
a Reaction conditions: 5 (1.2 mmol), 3 (1.0 mmol), CoCl2^.6H2O/1 (3 mol%), KOH (1.0 mmol), Zn (1.5 mmol), and H2O (5 mL) at 100 °C for 48 h. b Isolated yields.
1	5a	3a	4a, 74
2	5a	3b	4b, 68
3	5a	3c	4c, 86
4	5a	3d	4d, 66
5	5b	3a	4e, 93
6	5b	3b	4f, 82
7	5c	3a	4g, 78
8	5c	3b	4h, 73
9	5c	3c	4i, 72
10	5c	3d	4j, 64
11	5d	3a	4k, 61
12	5d	3b	4l, 61
13	5e	3a	4m, 74
14	5e	3b	4n, 68
15	5f	3a	4o, 86
16	5f	3b	4p, 80
17	5g	3a	4q, 73
18	5g	3b	4r, 71
19	5h	3a	4s, 53
20	5i	3a	4t, 48
21	5a	3e	4u, 27
22	5b	3e	4v, 30
23	5a	3f	4w, 26
24	5b	3f	4x, 45

---

Table 4 CoCl₂^.6H₂O/1-catalyzed S-arylation of aryl chlorides and thiols in water^a

Entry	Aryl chloride (6	Thiol (3	Yield (%)^b
a Reaction conditions: 6 (1.2 mmol), 3 (1.0 mmol), CoCl2^.6H2O/1 (3 mol%), KOH (1.0 mmol), Zn (1.5 mmol), and H2O (5 mL) at 140 °C for 72 h. b Isolated yields.
1	6a	3a	4a, 43
2	6a	3b	4b, 48
3	6a	3c	4c, 50
4	6b	3a	4e, 56
5	6b	3b	4f, 45
6	6c	3a	4g, 32
7	6c	3c	4i, 37
8	6d	3a	4k, 30
9	6d	3b	4l, 33
10	6e	3a	4m, 38
11	6e	3b	4n, 33
12	6f	3a	4o, 42
13	6f	3b	4p, 40

---

1-(4-(Phenethylthio)phenyl)ethanone (4v)

Pale yellow solid. Mp: 48–50 °C. ¹H NMR (CDCl₃, 400 MHz) δ = 2.55 (s, 3H), 2.97 (t, J = 8.0 Hz, 2H), 3.23 (t, J = 8.0 Hz, 2H), 7.20−7.25 (m, 3H), 7.29−7.33 (m, 4H), 7.85 (d, J = 8.8 Hz, 2H); ¹³C NMR (CDCl₃, 100 MHz) δ = 26.3, 33.4, 35.1, 126.5 (2C), 126.6, 128.4 (2C), 128.5 (2C), 128.7 (2C), 133.9, 139.6, 144.1, 197.0. Found: C, 74.86; H, 6.49.; S, 12.19. Calcd. for C₁₆H₁₆OS: C, 74.96; H, 6.29. S, 12.51.

Hexylphenylsulfide (4w)

Pale yellow oil. ¹H NMR (CDCl₃, 400 MHz) δ = 0.88 (t, J = 6.8 Hz, 3H), 1.26−1.33 (m, 4H), 1.38−1.46 (m, 2H), 1.60−1.68 (m, 2H), 2.91 (t, J = 7.2 Hz, 2H), 7.13−7.17 (m, 1H), 7.24−7.33 (m, 4H); ¹³C NMR (CDCl₃, 100 MHz) δ = 14.0, 22.5, 28.5, 29.2, 31.4, 33.7, 125.6, 128.8 (2C), 128.9 (2C), 137.1. Found: C, 74.61; H, 9.48.; S, 16.39. Calcd. for C₁₂H₁₈S: C, 74.16; H, 9.34.; S, 16.50.

1-(4-(Hexylthio)phenyl)ethanone (4x)

Pale yellow solid. Mp 69−71 °C. ¹H NMR (CDCl₃, 400 MHz) δ = 0.91 (t, J = 6.8 Hz, 3H), 1.29−1.36 (m, 4H), 1.43−1.50 (m, 2H), 1.67−1.74 (m, 2H), 2.56 (s, 3H), 2.99 (t, J = 7.6 Hz, 2H), 7.29 (d, J = 8.4 Hz, 2H), 7.85 (d, J = 8.4 Hz, 2H); ¹³C NMR (CDCl₃, 100 MHz): δ 13.7, 22.3, 26.1, 28.3, 28.5, 31.1, 31.7, 126.0 (2C), 128.4 (2C), 133.5, 137.6, 196.6. HRMS calcd for C₁₄H₂₀OS, 236.1236; found, 236.1235.

Typical procedure for the reuse of the catalytic aqueous solution

The reaction was conducted following the procedure described previously under the reaction conditions shown in Table 5. After cooling the reaction mixture to room temperature, the unreacted Zn powder and solidified product 4e were separated from the aqueous phase by centrifugation. The solid portion was washed with EtOAc and dried over MgSO₄. The pure product was isolated by column chromatography. The residual aqueous solution was then charged with 2b or 5b, 3a, KOH, and Zn for the next reaction.

Table 5 Reuse studies of CoCl₂^.6H₂O/1-catalyzed S-arylation in water^a

Entry	Ar–X	ArSH	Yield (%)^b in each cycle
			1st	2nd	3rd	4th	5th	6th	7th
a Reaction conditions: aryl halide (1.2 mmol), thiophenol (1.0 mmol), CoCl2^.6H2O/1 (3 mol%), KOH (1 mmol), Zn (1.5 mmol), and H2O (5 mL) at 100 °C for 24 h (Entry 1) or 48 h (Entry 2). b Isolated yields.
1	2b	3a	99	95	91	88	80	73	60
2	5b	3a	93	88	83	80	73	62	54

---

Results and discussion

In order to optimize the reaction conditions, the coupling of iodobenzene 2a and thiophenol 3a catalyzed by analysis grade CoCl₂·6H₂O combined with 1 was examined; the results are summarized in Table 1. It is known that the employment of 3a as the limiting reagent can diminish the formation of the disulfide by-product.¹² Therefore, the reaction gave the desired product, 4a, in a 42% GC yield when the reaction mixture, 2a (1.2 mmol) and 3a (1.0 mmol), was stirred in water (5 mL) under aerobic conditions in the presence of CoCl₂·6H₂O/1 (3 mol%) and 1.0 mmol KOH at 100 °C for 24 h (Entry 1). In order to improve the yield for the formation of 3a, Zn powder was employed as the reductant,⁷ and we found that 1.5 equiv of Zn and 1 equiv of KOH rendered the best result (Entries 2–4). Decreasing or increasing the catalyst loading did not afford better yields than the use of 3 mol% of catalyst (Entries 5 and 6). Reducing the reaction time to 12 h resulted in only a 69% GC yield (Entry 7). Employment of neutral 2,2’-bipyridyl as the ligand or the absence of 1 delivered 4a in only 49% and 33% yields, respectively (Entries 8 and 9), indicating the importance of 1 in this aqueous catalytic system. Using the various bases screened, low to high yields were obtained (Entries 10–15), and although the use of K₂CO₃ afforded a 90% yield, the employment of KOH as the base in Entry 3 produced optimal results. Co(NO₃)₂·6H₂O was also used as a catalyst to test the reaction; however, only a 73% GC yield was obtained (Entry 16). Buchwald and Bolm recently reported that a FeCl₃-catalyzed cross-coupling reaction may result owing to contamination by copper.¹³ To ensure that the reaction was catalyzed by cobalt, 99.999% purity CoCl₂·6H₂O was associated with 1 as the catalyst and a 98% GC yield of 4a was obtained (Entry 17). We also analyzed the remaining metal impurities in the analysis grade CoCl₂^.6H₂O by ICP-MASS, which showed that this metal salt contained 0.8 ppm of Cu and 0.2 ppm of Pd. Then, we ran several controlled experiments to determine whether the trace amounts of impurities were able to catalyze the S-arylation or not. Therefore, 0.01 mol% of CuO, Cu₂O, and PdCl₂(NH₃)₂ were combined with 1 as the catalytic systems in water for S-arylation under the same conditions as shown in Entry 3, which gave only yields between 5% and 10%, respectively (Entries 18–20). In addition, no desired product was observed when CuCl₂, CuCl, and PdCl₂ were employed as the catalysts (Entries 21–23). These results clearly demonstrate that the S-arylation is indeed catalyzed by cobalt and that trace quantities of impurities do not affect this reaction in an obvious manner.

After the optimal conditions were obtained, differently-substituted aryl iodides coupled with thiols were screened to determine the scope of this protocol. As shown in Table 2, the coupling of 2a with aryl thiols 3 gave the corresponding products, 4b–4d, in high yields (Entries 1–3). The cobalt/1-catalyst system proved suitable for the coupling of both electron-deficient and electron-rich aryl iodides with 3 to afford the corresponding diaryl sulfides in isolated yields between 71% and 99% (Entries 4–17). Furthermore, the results of this reaction were not affected by sterically-demanding ortho-substituted aryl iodides such as 2h and 2i; these underwent a coupling reaction with 3a leading to the formation of the corresponding products in 81% and 72% yields, respectively (Entries 18 and 19). Unfortunately, when alkyl-substituted thiols were employed, only moderate to good yields of thioethers were obtained (Entries 20–24).

With regard to aryl bromides, prolongation of the reaction time to 48 h was required to obtain a satisfactory outcome (Table 3). Hence, bromobenzene 5a could couple with a variety of aryl thiols, 3a–3d, in yields between 66% and 86% (Entries 1–4). For electron-poor aryl bromides, such as 5b, high product yields were obtained (Entries 5 and 6). In the case of electron-rich aryl bromides, isolated yields of over 60% could be obtained (Entries 7–14). 1-Bromonaphthalene 5f and meta-substituted 5g could also couple with 3a and 3b, giving the corresponding thioethers in yields between 71% and 86% (Entries 15–18). The coupling reaction of sterically-hindered 5h and 5i with 3a did occur, although the yields were lower than those of iodide analogs (Entries 19 and 20). As expected, aryl bromides coupled with alkyl-substituted thiols at a much slower rate, affording yields between 26% and 45% (Entries 21–24).

The reactivity of aryl chlorides was also studied. Reactions of a series of aryl chlorides and thiols were evaluated using a sealable tube under air at 140 °C for 72 h (Table 4). The use of chlorobenzene 6a and electron-poor 6b coupled with 3 giving yields between 43% and 56% (Entries 1–5). However, lower product yields were obtained when electron-rich 6c–6e were employed (Entries 6–11). Under identical conditions, coupling of 6f with 3 furnished 4o and 4p in moderate yields (Entries 12 and 13). Although the employment of aryl chlorides did not provide excellent yields of S-arylation products, there have been no previous reports of the use of aryl chlorides for the cross-coupling of C–S bonds in a cobalt-catalyzed reaction.

The reusability of the aqueous catalytic system is very important from the practical and economic viewpoints. In order to clarify whether the aqueous solution after reaction still possessed activity for a further catalytic cycle or not, a successive addition experiment was performed. After completion of the coupling reaction of 2b and 3a (Table 2, Entry 4), a fresh portion of 2b, 3a, KOH, Zn, and water was charged directly to the unseparated reaction mixture and the second cycle was executed under conditions identical to those of the first run; this procedure was repeated until the completion of the fifth cycle. We found that the overall isolated yield of 4e was 480%, corresponding to an average of a 96% yield for each cycle. This result clearly reveals that the aqueous solution after reaction is still active for further S-arylation and its loss of activity is slight.

The reaction outcome of the successive addition experiment prompted us to study the reusability of this CoCl₂·6H₂O/1catalytic system for S-arylation. We chose 2b and 5b as the representative aryl halides to couple with 3a under the conditions shown in Tables 2 and 3 for S-arylation. As shown in Table 5, cross-coupling of 2b and 3a with 3 mol% catalyst loading in the presence of Zn and KOH led to the formation of 4e in a 99% yield in 24 h. After completion of the first cycle and cooling of the reaction mixture to room temperature, unreacted Zn powder and solidified 4e were separated from the aqueous phase by centrifugation. The solid portion was washed with EtOAc, dried over MgSO₄, and purified by column chromatography. The remaining aqueous solution was then recharged with 2b, 3a, Zn, and KOH for a further cycle. It was found that the residual aqueous solution could be reused at least six times with only a slight decrease in activity (Entry 1). In comparison with the results of the successive addition experiment, the slow gradual decrease of product yield in each reuse run may be mainly due to a loss of catalyst concentration upon successive separation of the aqueous solution from the solid in each cycle. In the case of 5b, the reuse runs also proceeded well for each cycle (Entry 2). It is noteworthy that there is no need to separate the catalyst from the reaction medium and reactivate prior to reuse, indicating that the use of this catalytic system may meet the goals of green chemistry.

In comparison with other reported catalyst-reusable first-series transition-metal-catalyzed S-arylation reactions, such as Cu⁹ and Fe¹⁰, using water as the reaction medium, this cobalt-catalyzed reaction can be performed under air with a much lower catalyst loading, although the addition of Zn as a reductant is required. With regard to aryl halides, only aryl iodides are suitable for Fe-catalyzed reaction. Although both aryl iodide and bromide reactions can be catalyzed by a Cu catalyst, in this work not only iodides and bromides but also chlorides were able to react. The present protocol provides a useful alternative utilizing a less expensive transition-metal as a reusable catalyst for S-arylation.

Conclusion

In conclusion, we have developed a reusable and efficient water-soluble CoCl₂·6H₂O/cationic 2,2’-bipyridyl catalytic system for the cross-coupling of aryl halides and thiols. This method employs cationic 2,2’-bipyridyl as the ligand to bring the less expensive CoCl₂·6H₂O into the aqueous phase; therefore, the reaction can be performed in water under air, rendering the experimental and reuse procedures very simple. In addition, the aqueous catalytic system can be separated from the organic products by simple centrifugation and reused at least six times with only a slight decrease in activity, indicating that it may be an alternative protocol to complement other metal-catalyzed systems and has the potential for use in practical applications. Further studies of the use of this catalytic system in other organic reactions are now under investigation by our group.

Acknowledgements

This research was financially supported by the National Science Council of Taiwan (NSC98-2113-M-027-001-MY3). We thank Prof. Chung-Yuan Mou (National Taiwan University) for performing ICP-MASS to determine the amount of impurity in the cobalt salt.

References

1. (a) D. J. Procter, J. Chem. Soc., Perkin Trans. 1, 2001, 335; (b) G. Liu, J. R. Huth, E. T. Olejniczak, R. Mendoza, P. DeVries, S. Leitza, E. B. Reilly, G. F. Okasinski, S. W. Fesik and T. W. Von Geldern, J. Med. Chem., 2001, 44, 1202; (c) J. Hassan, M. Sevignon, C. Gozzi, E. Schulz and M. Lemaire, Chem. Rev., 2002, 102, 1359; (d) S. V. Ley and A. W. Thomas, Angew. Chem., Int. Ed., 2003, 42, 5400; (e) I. P. Beletskaya and A. V. Cheprakov, Coord. Chem. Rev., 2004, 248, 2337; (f) G. De Martino, M. C. Edler, G. La Regina, A. Coluccia, M. C. Barbera, D. Barrow, R. I. Nicholson, G. Chiosis, A. Brancale, E. Hamel, M. Artico and R. Silvestri, J. Med. Chem., 2006, 49, 947; (g) J.-P. Corbet and G. Mignani, Chem. Rev., 2006, 106, 2651; (h) I.-P. Beletskaya and V. P. Ananikov, Eur. J. Org. Chem., 2007, 3431; (i) A. Gangjee, Y. Zeng, T. Talreja, J. J. McGuire, R. L. Kisliuk and S. F. Queener, J. Med. Chem., 2007, 50, 3046.
2. T. Kondo and T. Mitsudo, Chem. Rev., 2000, 100, 3205.
3. (a) P. S. Herradura, K. A. Pendola and R. K. Guy, Org. Lett., 2000, 2, 2019; (b) C. Palomo, M. Oiarbide, R. Lopez and E. Gomez-Bengoa, Tetrahedron Lett., 2000, 41, 1283; (c) C. G. Bates, R. K. Gujadhur and D. Venkataraman, Org. Lett., 2002, 4, 2803; (d) F. Y. Kwong and S. L. Buchwald, Org. Lett., 2002, 4, 3517; (e) C. Savarin, J. Srogl and L. S. Liebeskind, Org. Lett., 2002, 4, 4309; (f) Y.-J. Wu and H. He, Synlett, 2003, 1789; (g) C. G. Bates, P. Saejueng, M. Q. Doherty and D. Venkataraman, Org. Lett., 2004, 6, 5005; (h) W. Deng, Y. Zou, Y.-F. Wang, L. Liu and Q.-X. Guo, Synlett, 2004, 1254; (i) Y.-J. Chen and H.-H. Chen, Org. Lett., 2006, 8, 5609; (j) D. Zhu, L. Xu, F. Wu and B. Wan, Tetrahedron Lett., 2006, 47, 5781; (k) L. Rout, T. K. Sen and T. Punniyamurthy, Angew. Chem., Int. Ed., 2007, 46, 5583; (l) X. Lu and W. Bao, J. Org. Chem., 2007, 72, 3863; (m) H. Zhang, W. Cao and D. Ma, Synth. Commun., 2007, 37, 25; (n) L. Rout, P. Saha, S. Jammi and T. Punniyamurthy, Eur. J. Org. Chem., 2008, 640; (o) H.-J. Xu, X.-Y. Zhao, J. Deng, Y. Fu and Y.-S. Feng, Tetrahedron Lett., 2009, 50, 434; (p) M. T. Herrero, R. SanMartin and E. Domínguez, Tetrahedron, 2009, 65, 1500; (q) S. Bhadra, B. Sreedhar and B. C. Ranu, Adv. Synth. Catal., 2009, 351, 2369; (r) C. Gonzalez-Arellano, R. Luque and D. J. Macquarrie, Chem. Commun., 2009, 1410; (s) C.-K. Chen, Y.-W. Chen, C.-H. Lin, H.-P. Lin and C.-F. Lee, Chem. Commun., 2010, 46, 282; (t) Y.-S. Feng, Y.-Y. Li, L. Tang, W. Wu and H.-J. Xu, Tetrahedron Lett., 2010, 51, 2489; (u) Y.-B. Huang, C.-T. Yang, J. Yi, X.-J. Deng, Y. Fu and L. Liu, J. Org. Chem., 2011, 76, 800; (v) D. J. C. Prasad and G. Sekar, Org. Lett., 2011, 13, 1008; (w) D. J. C. Prasad and G. Sekar, Synthesis, 2010, 79; (x) S. Kovács and Z. Novák, Org. Biomol. Chem., 2011, 9, 711.
4. (a) G. Y. Li, Angew. Chem., Int. Ed., 2001, 40, 1513; (b) U. Schopfer and A. Schlapbach, Tetrahedron, 2001, 57, 3069; (c) M. Murata and S. L. Buchwald, Tetrahedron, 2004, 60, 7397; (d) T. Itoh and T. Mase, Org. Lett., 2004, 6, 4587; (e) C. Mispelaere-Canivet, J.-F. Spindler, S. Perrio and P. Beslin, Tetrahedron, 2005, 61, 5253; (f) M. A. Fernández-Rodríguez, Q. Shen and J. F. Hartwig, J. Am. Chem. Soc., 2006, 128, 2180; (g) J. Y. Lee and H. L. Phil, J. Org. Chem., 2008, 73, 7413; (h) Z. Jiang, J. She and X. Lin, Adv. Synth. Catal., 2009, 351, 2558; (i) C. C. Eichman and J. P. Stambuli, J. Org. Chem., 2009, 74, 4005; (j) C. S. Bryan, J. A. Braunger and M. Lautens, Angew. Chem., Int. Ed., 2009, 48, 7064; (k) C.-F. Fu, Y.-H. Liu, S.-M. Peng and S.-T. Liu, Tetrahedron, 2010, 66, 2119; (l) M. A. Fernández-Rodríguez and J. F. Hartwig, Chem.–Eur. J., 2010, 16, 2355.
5. (a) H. J. Cristau, B. Chabaud, A. Chêne and H. Christol, Synthesis, 1981, 892; (b) K. Takagi, Chem. Lett., 1987, 2221; (c) V. Percec, J.-Y. Bae and D. H. Hill, J. Org. Chem., 1995, 60, 6895; (d) C. Millois and P. Diaz, Org. Lett., 2000, 2, 1705; (e) S. Jammi, P. Barua, L. Rout, P. Saha and T. Punniyamurthy, Tetrahedron Lett., 2008, 49, 1484; (f) J. Zhang, C. M. Medley, J. A. Krause and H. Guan, Organometallics, 2010, 29, 6393.
6. (a) A. Correa, M. Carril and C. Bolm, Angew. Chem., Int. Ed., 2008, 47, 2880; (b) J.-R. Wu, C.-H. Lin and C.-F. Lee, Chem. Commun., 2009, 4450; (c) V. K. Akkilagunta, V. P. Reddy and K. R. Rao, Synlett, 2010, 1260.
7. Y.-C. Wong, T. T. Jayanth and C.-H. Cheng, Org. Lett., 2006, 8, 5613.
8. (a) For reviews see: C. J. Li, Chem. Rev., 1993, 93, p. 2023; (b) G. Papadogianakis and R. A. Sheldon, New. J. Chem., 1996, 20, 175; (c) B. Cornils, J. Mol. Catal. A: Chem., 1999, 143, 1; (d) J. P. Genet and M. Savignac, J. Organomet. Chem., 1999, 576, 305; (e) W. A. Herrmann (Ed.), Synthesis Methods in Organometallic and Inorganic Chemistry, Enke: Stuttgart, 2000; (f) B. Cornils and W. A. Herrmann (ed.), Aqueous-Phase Organometallic Catalysis, Wiley-VCH: Weinhein, Germany, 2004; (g) C.-J. Li and T.-H. Chan, Organic Reactions in Aqueous Media, John Wiley & Sons, New York, 1997; (h) P. A. Grieco (Ed.), Organic Synthesis in Water, Blackie Academic and Professional, London, 1998; (i) N. E. Leadbeater, Chem. Commun., 2005, 2881; (j) C. J. Li, Chem. Rev., 2005, 105, 3095; (k) C. J. Li and L. Chen, Chem. Soc. Rev., 2006, 35, 68; (l) I. T. Horváth and P. T. Anastas, Chem. Rev., 2007, 107, 2167; (m) D. Dallinger and C. O. Kappe, Chem. Rev., 2007, 107, 2563; (n) S. Liu and J. Xiao, J. Mol. Catal. A: Chem., 2007, 270, 1; (o) C.-J. Li and B. M. Trost, Proc. Natl. Acad. Sci. U. S. A., 2008, 105, 13197; (p) I. T. Horváth, Green Chem., 2008, 10, 1024; (q) K. H. Shaughnessy, Chem. Rev., 2009, 109, 643; (r) R. N. Butler and A. G. Coyne, Chem. Rev., 2010, 110, 6302.
9. M. Carril, R. SanMartin, E. Domínguez and I. Tellitu, Chem.–Eur. J., 2007, 13, 5100.
10. W.-Y. Wu, J.-C. Wang and F.-Y. Tsai, Green Chem., 2009, 11, 326.
11. (a) W.-Y. Wu, S.-N. Chen and F.-Y. Tsai, Tetrahedron Lett., 2006, 47, 9267; (b) S.-N. Chen, W.-Y. Wu and F.-Y. Tsai, Tetrahedron, 2008, 64, 8164.
12. (a) H. M. Meshram and R. Kache, Synth. Commun., 1997, 27, 2403; (b) N. Iranpoor and B. Zeynizadeh, Synthesis, 1999, 49.
13. (a) S. L. Buchwald and C. Bolm, Angew. Chem., Int. Ed., 2009, 48, 5586; (b) P.-F. Larsson, A. Correa, M. Carril, P.-O. Norrby and C. Bolm, Angew. Chem., Int. Ed., 2009, 48, 5691.

---

Footnote

† Electronic Supplementary Information (ESI) available: Spectroscopic characterization data of S-arylation products, and copies of ¹H and ¹³C NMR of compound 4v, 4w, and 4x. See DOI: 10.1039/c1ra00406a/

---