STOBBE CONDENSATION INVOLVING DIETHYL DIGLYCOLLATE WITH FURAN 2-ALDEHYDE AND THIOPHENE-2-ALDEHYDE SYNTHESIS OF CYCLOPENTENO-FURAN AND CYCLOPENTENO- THIOPHENE DERIVATIVES

Diethyl diglycollate condenses with furan -2-aldehyde and thiophene-2- aldehyde in pre¬sence of sodium hydride to give predominantly the (Z)-half ester (la, b) together with small amo- unts of the (E)-half ester (2a, b). The structure of the (E)-half esters was based on their cycliza- tion to cyclopenteno-furan and cyclopentenothiophene derivatives (5a, b) respectively, as well as on spectroscopic evidence. The ratio of isomers has been interpreted in terms of the relative ease of formaticn of the S-lactone intermediates. Diethyl diglycollate condenses with furan-2-aldehyde and thiophene -2-aldehyde in presence of sodium hydride to give predominantly the (Z) half ester (la, b) together with small amounts of the (E)-half ester (2a, b). The structure of the (E)-half esters was based on their cycliza- tion to cyclopenteno-furan and cyclopentenothiophene derivatives (5a, b) respectively, as well as on spectroscopic evidence.