Copper-mediated synthesis of coumestans via C(sp sup(2))-H functionalization: Protective group free route to coumestrol and 4′-O-methylcoumestrol

Abstract

A simple and efficient two step synthesis of coumestans is described. The key reaction in the synthesis is the use of easily available Cu(OAc)sub(2) for C-H functionalization of 3-(2-hydroxyphenyl)coumarin to give coumestan ring system via formal oxidative cyclization. This approach provided a short protective group free route to naturally occurring coumestrol and 4′-O-methylcoumestrol.