Base-promoted thioannulation of o-alkynyl oxime ethers with sodium sulfide for the general synthesis of isothiocoumarins

Abstract

A general and efficient strategy for the one-pot synthesis of isothiocoumarin-1-ones has been developed via the base-promoted 6-endo-dig thioannulation of o-alkynyl oxime ethers using the cheap and readily available Na₂S as the sulfur source. Mechanistic studies disclosed that the reaction proceeded through two C–S bond formations, N–O bond cleavage and the final hydrolysis of imines.