Alcohol mediated synthesis of 4-oxo-2-aryl-4H-chromene-3-carboxylate derivatives from 4-hydroxycoumarins.

The unusual alcohol mediated formation of 4-oxo-2-aryl-4H-chromene-3-carboxylate (flavone-3-carboxylate) derivatives from 4-hydroxycoumarins and β-nitroalkenes in an alcoholic medium is described. The transformation occurs via the in situ formation of a Michael adduct, followed by the alkoxide ion mediated rearrangement of the intermediate. The effect of the different alcohol and nonalcohol media on the reaction was investigated.