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DOI: 10.1055/s-0029-1218485
Base-Controlled Sequential C-S Bond Formation by CuSO4/Al2O3 Catalyst
Contributor(s):Yasuhiro Uozumi, Yoichi M. A. Yamada, Hidetoshi OhtaIndian Association for the Cultivation of Science, Kolkata and Indian Institute of Chemical Technology, Hyderabad, India
Recyclable Heterogeneous Supported Copper-Catalyzed Coupling of Thiols with Aryl Halides: Base-Controlled Differential Arylthiolation of Bromoiodobenzenes
Adv. Synth. Catal. 2009, 351: 2369-2378
Publication History
Publication Date:
21 December 2009 (online)
Key words
alumina support - copper - cross-coupling - thiols

Significance
An alumina-supported copper sulfate (CuSO4/Al2O3) enabled the base-controlled chemoselective C-S cross-coupling of aryl iodides 1 and bromides 4 with thiols 2. Thus, the reaction of 1 with 2 proceeded chemoselectively in the presence of CuSO4/Al2O3 and K2CO3 to give the corresponding products 3. On the other hand, bromides 4 were coupled with 2 by using Cs2CO3 as a base. This protocol was successfully applied to the sequential C-S cross-coupling of bromoiodobenzenes with different thiols, providing the corresponding unsymmetrical bis-thioethers.
Comment
The CuSO4/Al2O3 support was recovered by centrifugation and was reused seven times with slight loss of its catalytic activity. The leaching of Cu was checked by ICP-MS analysis after the 8th run to be 2.71%. CuSO4/Al2O3 catalyst was also effective for the C-O and C-N coupling of aryl halides. Thus, the C-O coupling with phenols proceeded in the presence of Cs2CO3 in DMF at 110 ˚C. The C-N coupling with amines occurred in the presence of K2CO3 in H2O at 100 ˚C.
