Benzopyrones. Part XI. Some 3-substituted 4-oxochromen-2-carboxylic acid derivatives

Abstract

The homolytic chlorination of ethyl 4-oxochromen-2-carboxylate produces three chlorine-containing esters: the known 3-chloro-derivative (1), 2-chloroethyl 3-chloro-4-oxochromen-2-carboxylate (2), and ethyl cis-2,3-dichloro-4-oxochroman-2-carboxylate (13). Ammonia converted the ester (1) into 3-amino-4-oxochromen-2-carboxamide, but 3-chloro-4-oxochromen-2-carbonitrile under the same conditions gave 2-amino-3-chlorochromone (15). The preparation and some reactions of ethyl 3-bromomethyl-4-oxochromen-2-carboxylate are described. Conflicting reports of the characteristics of ethyl 4-(2-hydroxyphenyl)-2,4-dioxobutanoate have been resolved and the corresponding methyl ester has been synthesized; aminoethylation of the latter yielded the 3-dimethylaminomethylchromone (11).