Methylenation studies of hydroxyflavonoids and derivatives of resorcinol: syntheses of biflavonyls of novel types

Abstract

Methylenation of 7-hydroxyflavonoids and carbonyl derivatives of resorcinol in the presence of potassium carbonate and acetone yields bimolecular compounds (II, IV, VI and VIII) linked by a methylenedioxy group in the reactive 7 and 4 positions respectively. Chelated hydroxyls do not enter into this reaction. Methylenation of resacetophenone and 2,4-dihydroxyphenyl benzyl ketone in the presence of ethanolic ethoxide yields nuclear methylenated products having biphenyl-methane structures (XII and XIV); coupling occurs in the 3-position of the ketones. The structure of these bis compounds is discussed in relation to the other known types.