By products from the Preparation of Dehydrobenzoylacetic acid-Substituted-2H, SH•pyrano [4, 3-b] pyran-2, S-diones and their synthesis

Substituted-2H, 5H-pyrano (4,3-b) pyran-2, 5-diones (lIa) and (lIb) have been isolated as by products in the preparation of dehydrobenzoylacetic acid (1) from the selfcondesnation of ethyl­benzoylacetate. A facHe method of general applicability for the synthesis of substituted-2H, 5H­pyranopyran-2, 5-diones (lIb-g, V) from "l3-ketoesters and 4-hydroxy-pyran -2-ones (III, IV) using sodium bicarbonate as condensing agent has been described. For spectral comparison a number of substituted-4H, 5H-pyranopyran-4, 5-diones (VI, VII) have also been synthesised.

P F G PRAILL ,M SIDDIQ ,