Synergistic silver/scandium catalysis for divergent synthesis of skeletally diverse chromene derivatives.

Abstract

The combination of AgTFA and Sc(OTf)3 enables the bimetallic synergistic catalysis of β-alkynyl ketones and o-hydroxybenzyl alcohols, allowing divergent synthesis of three classes of skeletally diverse chromene derivatives with generally good yields and high diastereoselectivity through dehydroxylated bi- and tri-cyclization cascades. The selectivity of these cycloadditions was controlled by adjusting the catalyst loading and reaction temperatures. The mechanisms for forming these compounds were proposed.