Useful Synthesis of Coumestans

Abstract

Abstract A convenient synthesis of coumestans involving a combination of lithiation and Wittig reactions is described. Compounds 1a and 1b on reaction with n-butyllithium followed by treatment with diethyloxalate provide ketoesters 3a and 3b. Reaction of 3(a-b) with phosphorane generated from salt 4 gives 5(a-b) which on reaction with pyridine hydrochloride yield 7(a-b). DDQ oxidation of 7(a-b) gives coumestans 8(a-b).