Base-Controlled Sequential C-S Bond Formation by CuSO₄/Al₂O₃ Catalyst

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.