A convenient one-pot synthesis of 7-hydroxy-isoflavones from resorcinol with substituted phenylacetic acids

A mild and highly efficient one-pot synthesis of 7-hydroxy-isoflavones is reported. The acylation of resorcinol with various phenyl acetic acids in molten zinc chloride affords an intermediate deoxybenzoin which without isolation is subjected to cyclization with N,N-dimethylformamide in the presence of boron trifluoride diethyl etherate and methanesulfonyl chloride to afford the 7-hydroxy-isoflavone without the formation of any by-product.