Benzopyrones. Part 19. Synthesis and some reactions of ethyl 3-bromo-4-oxochromen-2-carboxylate

Abstract

The product of the condensation of o-hydroxyacetophenone and diethyl oxalate, ethyl 2-hydroxy-4-oxochroman-2-carboxylate (13), slowly and partially isomerises in solution to the phenolic ketone (16), but in the presence of mineral acid, it is rapidly dehydrated directly to ethyl 4-oxochromen-2-carboxylate (2; R = Et). Bromination of the oxochroman (13) gave a 72:28 mixture of epimeric 3-bromo-esters. The major isomer (trans-OH, H) was readily dehydrated to give the title compound which contains a reactive bromine atom.