Benzopyrones. Part II. 7-hydroxy-4-oxochromen-2-carboxylic acid and some of its derivatives

Abstract

A simplified synthesis of 7-hydroxy-4-oxochromen-2-carboxylic acid (1) from 2,4-dihydroxyacetophenone is described. Bromination of ethyl 7-hydroxy-4-oxochromen-2-carboxylate (3) gave a mixture of 8-bromo-, 6,8-dibromo-, and 3,6,8-tribromo-derivatives; similar treatment of the acid (1) yielded the 8-bromo-acid only. Nitration of the acid (1) or ester (3) gave the 8-nitro- or the 6,8-dinitro-derivative. The n.m.r. and i.r. spectra of these and related chromones are discussed.