Synthesis and analgesic activity of benzofuran carboxamide derivatives

Treating 4-methoxy- and 4,7-dimethoxy-6-hydroxybenzofuran-5-carboxylic acid with ethyl chloroformate in dry acetone leads to the formation of the monocarbethoxy derivatives, which on cyclization give the corresponding anhydrides. The latter compounds react with hydrazines to give the hydrazide carboxylate derivatives. On the other hand, when the benzofuran-5-carboxylic acids are treated with ethyl chloroformate in dimethyl formamide, the 5-carbethoxy derivatives are obtained. These react with hydrazine hydrate and amines. Some of the new compounds show analgesic activity