Functional derivatives of thiophene

Abstract

We have found that 4-oxothieno[2,3-d]oxazines (lla-h) can be obtained by the action of thionyl chloride on 2-aroylaminothiophene-3-carboxylic acids (la-h) in the presence of dimethylformamide (DMF), i.e., under the conditions of the synthesis of arenecarboxylic acid chlorides. The reaction evidently proceeds through a step involving the formation of thiophenecarboxylic acid chlorides. We obtained thiophenecarboxylic acids la, c, h for the first time by the method described in [2].