Aerobic bimetallic catalysis for oxy-alkynylation of allenes

Abstract

Here we report a conceptual protocol to construct 4-alkynyl furan-2(5H)-one derivatives efficiently through Rh(III)/Cu(I) co-catalyzed highly regioselective oxy-alkynylation of 2,3-allenoic acids with terminal alkynes under mild aerobic conditions with atom economy. A wide variety of functional groups including biologically active groups have been tolerated. The synthetic potentials have also been demonstrated and the total syntheses of natural product appenolide A and its (Z)-isomer have been achieved by applying this protocol as the key step efficiently. A mechanism has been proposed based on mechanistic studies.