The work was supported by IOCB (Z40550506), and the
Czech Academy of Sciences (M200550907).
Notes and references
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Scheme 4 Cross-coupling reaction of the mercaptoacetylenes.
Table 2 Cross-coupling reaction of the mercaptoacetylenesa
Yield
(%)
Product
3
R0 0
R0
5a
5b
3d
3k
4-tolyl
4-MeOPh
Ph
85
83
2-(Cl)-5-(NO2)-
PhCOOCH2-
n-Bu
2-(Cl)-5-(NO2)
PhCOOCH2-
4-fluorophenyl
4-fluorophenyl
5c
5d
3g
3k
4-dibenzothienyl
3-NO2Ph
69
66
3 (a) K. Sonogashira, Y. Tohda and N. Hagihara, Tetrahedron Lett.,
1975, 16, 4467; (b) E. Negishi and L. Anastasia, Chem. Rev., 2003,
103, 1979; (c) R. Chinchilla and C. Najera, Chem. Rev., 2007, 107,
874.
5e
5f
3n
3n
2,6-diMePh
2-MeOPh
58
76
a
General procedure: Thioacetylene (1.00 mmol), arylboronic acid
(1.30 mmol), Cu(I) 3-methylsalicylate (1.20 mmol) and Pd(PPh3)4
(5 mol%) were stirred in DME (8 mL) under argon at 40–45 1C for 16 h.
4 (a) C. Savarin, J. Srogl and L. S. Liebeskind, Org. Lett., 2001, 3,
91. For
a
haloacetylene version of the chemistry see:
(b) N. Miyaura, K. Yamada and A. Suzuki, Tetrahedron Lett.,
1979, 20, 3437; (c) X. Yang, L. Zhu, Y. Zhou, Z. Li and H. Zhai,
Synthesis, 2008, 11, 1729; (d) C.-M. Yu, J.-H. Kweon, P.-S. Ho,
S.-C. Kang and G. Y. Lee, Synlett, 2005, 2631.
5 S. Oae and T. Okuyama, Organic Sulfur Chemistry: Biochemical
Aspects, CRC Press, Boca Raton, 1992.
6 (a) For Rh catalyzed version see: M. Arisawa, M. Fujimoto,
S. Morinaka and M. Yamaguchi, J. Am. Chem. Soc., 2005, 127,
12226; (b) For stoichiometric Cu(I)OTf and trimethylsilyl acetylene
see: N. Miyachi and M. Shibasaki, J. Org. Chem., 1990, 55,
1975.
7 C. Savarin, J. Srogl and L. S. Liebeskind, Org. Lett., 2002, 4, 4309.
8 W. Shi, Y. Luo, X. Luo, L. Chao, H. Zhang, J. Wang and A. Lei,
J. Am. Chem. Soc., 2008, 130, 14713.
9 R. G. Pearson, J. Am. Chem. Soc., 1963, 85, 3533; R. G. Pearson,
Chemical Hardness, Wiley-VCH, Weinheim, 1997.
10 The general reactivity pattern of the present thioacetylenes in the
cross-coupling reaction is the same as the one published previ-
ously.4a When n-hexyl boronic acid was used as the coupling
partner no desired productwas detected.
11 While it is clearly not the main topic of the paper, the Cu releasing
reaction was experimentally demonstrated. For the details see the
supplementary materials.
Setting aside their excellent synthetic accessibility, there is
an interesting advantage in utilizing the cyclic N-thioamides as
the reaction substrates. The present structural motif reveals a
unique intrinsic reactivity pattern further obviating the
substrate selection; Cu thiolates, the obligatory byproducts
of the cross-coupling reaction,4a can be turned back into the
starting N-thioamide substrates under exceptionally mild
conditions, releasing copper in due course.11
Overall, we have introduced a metal catalyzed oxidative
arylthiation of terminal alkynes. The tentative reaction
mechanism was proposed, which starts with a C–H bond
activation step and involves the intermediate formation of
metal acetylides. The synthetic utility of the resulting mercapto-
acetylenes is illustrated by several cross-coupling reactions and
the concept of the byproduct recycling is demonstrated by way
of a novel oxidative method.
c
This journal is The Royal Society of Chemistry 2010
Chem. Commun., 2010, 46, 6819–6821 6821