TBAI-promoted synthesis of thioenamines via C-S bond formation between enaminones and thiosulfonates

A TBAI-mediated protocol for constructing C(sp²)-S bonds at the α-position of enaminones has been developed, utilizing odorless thiosulfonates as the organosulfur source. This transition metal-free and strong oxidant-free protocol efficiently synthesizes multifunctional thioenaminones with high yields (up to 96%) and excellent selectivity under mild reaction conditions. The reaction demonstrates broad substrate scope and excellent functional group compatibility and is readily scalable to gram quantities. Mechanistic investigations suggest a nucleophilic substitution pathway involving iodide-assisted activation of thiosulfonates. This operationally simple and environmentally benign methodology provides efficient access to a wide range of thioenaminones, which are important scaffolds in medicinal and synthetic chemistry.