Convenient Synthesis of 3,5-Diaryl-4H-pyran-4-ones

Abstract

In 1978, Ishibe and Yutaka¹ reported the synthesis of 2,6-dimethyl-3,5-bis(para-substituted phenyl)-4H-pyran-4-ones by condensation of para, para-disubstituted dibenzyl ketones with acetic acid in the presence of polyphosphoric acid. Morgan and Ganem² synthesized 2-substituted-4H-pyran-4-ones from the potassium enolate of 4-methoxy-3-buten-2-one and acid chlorides, anhydrides and acylimi-dazoles. Weissenfels et. al.³ discovered that the reaction of dimethylformamide and phosphorous oxychloride with pheny1 benzyl ketone afforded a mixture of the expected vilsmeier adducts, 1 (50%) and 2 (10%). However, the same reaction with diphenylacetone failed to produce the expected aldehyde 3 giving instead 3,5-diphenyl-4H-pyran-4-one

5a, in 35% yield. Ei-kholy, et. a1.^4,5 reported the successful conversion of 3,5-diaryl-4H-pyran-4-one to the corresponding 1-methyl-3,5-diaryl-4(1H)pyridone with

methylamine. Our interest in pyridones of this type⁶ prompted consideration of a simple preparative route to the title compounds.