Cobalt-promoted synthesis of sulfurated oxindoles via radical annulation of N -arylacrylamides with disulfides.

An efficient radical annulation of N -arylacrylamides with disulfides is developed for the synthesis of sulfurated oxindoles. The reaction occurs in a facile manner using CoBr 2 as both an initiator and a promoter for the first time and (NH 4 ) 2 S 2 O 8 as the oxidant. By controlling the CoBr 2 /(NH 4 ) 2 S 2 O 8 ratio, a wide range of sulfurated and brominated/sulfurated oxindoles are selectively prepared in good to excellent yields. The present protocol is simple and highly atom economical, and can tolerate a broad range of substrates.