High stereoselectivity in the Wittig reaction induced by the interaction of charges

Article abstract of DOI:10.1016/0040-4039(96)00780-0

The synthesis of carbacyclin analogues I based on the introduction of an α-chain to a suitable substituted bicyclo[3.3.0]octan-3-one derivative like 5 by a Wittig reaction leads generally to nearly 1:1-mixtures of E/Z-isomers. This lack of selectivity will change dramatically, if an acidic sulfonamide in the bicyclic framework is present. The observed Z-selectivity can be explained by an interaction of charges of the deprotonated sulfonamide and the electrophilic phosphorous atom in the Wittig reagent.