Synthesis of 2<i>H</i>-Chromenes via Unexpected [4 + 2] Annulation of Alkynyl Thioethers with <i>o</i>-Hydroxybenzyl Alcohols

Abstract

A novel Brønsted acid-catalyzed reaction of alkynyl thioethers with o-hydroxybenzyl alcohols via an unexpected formal [4 + 2] annulation has been developed. This metal-free protocol leads to the facile and practical synthesis of valuable polysubstituted 2H-chromenes in mostly good to excellent yields under mild reaction conditions and features a wide substrate scope and excellent functional group tolerance.