Synthesis of trans-2,3-dimethoxy-3- (phenylamino)flavanones and related compounds

Abstract

trans-2,3-Dimethoxy-3-(phenylamino)flavanones (2), a new type of flavanone derivatives, are synthesized from flavanones or 2'-hydroxychalcones in two steps, the first one being a condensation with nitrosobenzenes (Ehrlich-Sachs reaction) and the second an oxidation with (diacetoxyiodo)benzene in methanol. Nitrone formation, an important side reaction of the Ehrlich-Sachs reaction, has also been exploited to synthesize 2 simply by use of an excess of nitrosobenzene in aqueous methanol. Syntheses of several analogues of 2 are also reported.Key words: trans-2,3-dimethoxy-3-(phenylamino)flavanones, 2'-hydroxychalcones, nitrosobenzenes, 3-(phenylamino)flavones, (diacetoxyiodo)benzene.