One-Pot Synthesis of B-Ring Ortho-Hydroxylated Sappanin-Type Homoisoflavonoids.

A reliable method for the synthesis of B-ring hydroxylated homoisoflavonoids and 3-hetarylmethyl chromones has been developed. The method involves an initial oxa-Diels-Alder reaction of ortho-quinone methides generated from aryl/hetaryl-substituted ortho-( N, N-dimethylaminomethyl)phenols with (2 E)-3-( N, N-dimethylamino)-1-(2-hydroxyphenyl)prop-2-en-1-ones and the subsequent cascade of reactions. This synthetic strategy avoids conventional multistep protocols and does not require the protection of hydroxyl groups, thus allowing the facile synthesis of a library of various aromatic and heterocyclic analogues of naturally occurring homoisoflavonoids.