Abstract 3-Carboalkoxy-2, 3-dihydrothiophenes, available by Birch reduction of thiophene-3- carboxylic acid or more efficiently by deconjugation of 2, 5-dihydrothiophene-3-carboxylic acid by reaction with ethyl chloroformate and triethylamine, undergo cycloaddition reactions with dichloroketene leading to 4-carboxy-7, 7-dichloro-2-thiabicyclo [3.2. 0] heptan-6-ones which are of interest as potential β-lactamase inhibitors.
