l-Proline promoted cross-coupling of vinyl bromide with thiols catalyzed by CuBr in ionic liquid

A method for the synthesis of vinyl sulfides by the coupling of vinyl bromides with thiols using the copper(I) bromide as catalyst and l-proline as ligand was reported. The best yields were obtained in the ionic liquid [Bmim]BF4 with the retention of stereochemistry. This protocol is palladium-free, tolerates both aromatic and aliphatic thiols, possesses good selectivity between alcohol and thiol, and does not require the use of expensive or air-sensitive additives.