Regioselectivity switch based on the stoichiometry: stereoselective synthesis of trisubstituted vinyl epoxides by Cu-catalyzed 3-exo-trig cyclization of α-allenols

Abstract

Typical transition metal-catalyzed oxycyclization of allenols takes place at the terminal allene carbon via a 5-endo path and forms dihydrofurans. A copper-catalyzed protocol brought about a reversed regioselectivity, generating a series of trisubstituted epoxides through a 3-exo-cyclization/sulfonylation cascade. The current stoichiometry control of regioselectivity may open singular opportunities in chemical transformations.