A one-pot metal-free protocol for the synthesis of chalcogenated furans from 1,4-enediones and thiols

Transition-metal-free synthesis of chalcogenated furans through the sequential thiol-Michael/Paal-Knorr reaction of 1,4-enediones in the presence of a catalytic amount of p-toluenesulfonic acid has been developed. The present one-pot strategy involves the thiol Michael addition to 1,4-enediones in an anti-Markovnikov fashion with the formation of a new C-S bond, followed by intramolecular dehydrative annulation in the presence of cat. TsOH delivering fully substituted furans in good to excellent yields (50-99%). The reaction is compatible with a wide range of substrates and also capable of multi-gram scale synthesis of chalcogenated furans.