D. J. C. Prasad et al. / Tetrahedron Letters 50 (2009) 1411–1415
1415
Table 3 (continued)
Entry
Aryl halide/tosylate
Product
Time (h)
24
Yielda (%)
00
17
18
19
Cl
H2NOC
OHC
S
H2NOC
18
5
87b
98b
97b
Cl
S
OHC
O2N
O2N
Cl
O2N
S
20
5
Cl
O2N
S
a
Isolated yield. All the thioethers gave satisfactory spectral data. See Supplementary data for details.
The reaction took place without BINAM–Cu(OTf)2.
b
Perkin Trans. 1 2001, 335–354; (h) Herradura, P. S.; Pendola, K. A.; Guy, R. K.
Org. Lett. 2000, 2, 2019–2022.
out a catalyst. In the case of weakly activated aryl chlorides, nei-
ther the nucleophilic addition elimination mechanism nor the
coupling reaction catalyzed by BINAM–Cu(OTf)2 provides the
product (Table 3, entries 16–17). This result shows that highly
activated aryl halides (aryl halides with very strong electron-
withdrawing groups such as nitro and aldehyde groups) give
C(aryl)–S bond formation through the nucleophilic addition elim-
ination mechanism) without a copper catalyst, whereas other
aryl halides need a copper catalyst for C–S bond formation
through the coupling reaction.
In summary, we have developed an efficient, experimentally
simple and economically attractive copper catalyzed S-arylation
of thiols with aryl iodides. Aryl bromides can also be used for S-
arylation of thiols under the same reaction conditions without
increasing the reaction temperature. Strongly activated aryl chlo-
rides and tosylates provide corresponding thioethers by the nucle-
ophilic addition elimination mechanism without a copper catalyst.
Efforts to expand the utility of our new catalytic system to weakly
activated chlorides/tosylate and other classes of nucleophiles and
detailed mechanistic studies are in progress.
2. (a) Yamamoto, T.; Sekine, Y. Can. J. Chem. 1984, 62, 1544–1547; (b) Hickman, R.
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Acknowledgements
15. Lv, X.; Bao, W. J. Org. Chem. 2007, 72, 3863–3867.
We thank DST (Project No.: SR/S1/OC-06/2008), New Delhi, for
the financial support. D.J.C.P and A.B.N. thank UGC for their
fellowship.
16. Zhang, H.; Cao, W.; Ma, D. Synth. Commun. 2007, 37, 25–35.
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2258; (b) Mannam, S.; Sekar, G. Tetrahedron Lett. 2008, 49, 1083–1086; (c)
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18. (a) Naidu, A. B.; Ragunath, O. R.; Prasad, D. J. C.; Sekar, G. Tetrahedron Lett. 2008,
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Supplementary data
19. Typical representative experimental procedure: Cs2CO3 (325.8 mg, 1 mmol),
Cu(OTf)2 (36.16 mg, 0.1 mmol) and BINAM L3 (28.4 mg, 0.1 mmol) were
taken in a 10 mL reaction tube equipped with a septum. The reaction tube was
evacuated and back-filled with nitrogen. N,N-Dimethylformamide (2.0 mL)
was added to the reaction mixture at room temperature. To the resulting
solution, p-methoxy iodobenzene (117 mg, 0.5 mmol) was added followed by
benzenethiol (60.6 mg, 0.55 mmol), and the reaction mixture was heated for
6 h at 110 °C. After the complete disappearance of p-methoxy iodobenzene
(the progress of the reaction was monitored by TLC), the reaction mixture was
allowed to cool to room temperature. The crude residue was directly purified
by column chromatography on silica gel using ethyl acetate/hexanes as eluents
to give 96% of pure 4-methoxyphenyl phenyl sulfide8 (Table 2, entry 1) as
colourless oil.
Supplementary data associated with this article can be found, in
References and notes
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