Preparative synthesis of ethyl 5-acyl-4-pyrone-2-carboxylates and 6-aryl-, 6-alkyl-, and 5-acylcomanic acids on their basis

A simple and efficient method for the synthesis of ethyl 5-alkanoyl- and 5-aroyl-4-pyrone-2-carboxylates was developed, which is based on the condensation of 1-R-2-(dimethyl-aminomethylidene)butane-1,3-diones, obtained from 1,3-diketones and dimethylformamide dimethyl acetal, with diethyl oxalate in the presence of NaH in THF. Ethyl 5-acyl-4-pyrone-2-carboxylates were used in the synthesis of 6-R- and 5-RCO-comanic acids.