Condensation of 2-hydroxyacetophenone with benzaldehyde in the presence of 70% perchloric acid in ethylorthoformate gave the corresponding 4-ethoxyflavylium perchlorate, which was treated with aqueous ammonia or methylamine solution to afford 1,6,7,8-substituted 2-(3′,4′-substituted-phenyl)-4-quinolone in fair to good yield.
Fourteen 1-, 6-, 7-, 8-mono-, 7,8-di-, and 6,7,8-trisubstituted 2-(4'-hydroxy- and 4'-hydroxy-3 '-methoxy)phenyl-4-quinolinones were conveniently synthesized by aqueous ammonia treatment of the flavylium salts obtained by the three-components condensation reaction of acetophenones, aldehydes, and ethyl orthoformate on a solid support with excellent purity and in overall yields of 11-59%.