P. Chatterjee et al., PREPARATION OF 2,3-DISUBSTITUTED-4,5-DIHYDROTHIOPHENES AND THIOPHENESUSING THE INTRAMOLECULAR NONCLASSICAL WITTIG REACTION OF THIOLCARBOXYLATES, Journal of the Chemical Society. Perkin transactions. I, (17), 1994, pp. 2403-2405
2-Ethoxycarbonylcyclopropyl(triphenyl)phosphonium fluoroborate 1 react
s with alkali-metal thiolates to give 2,3-disubstituted 4,5-dihydrothi
ophenes 3 which can be aromatised to the corresponding thiophenes 5.