Features of the reaction of 2,3-dihalopropanoic acids with pyridines and nucleophilic addition to N-vinylpyridinium salts

The example of vinylpyridinium salts to establish for the first time the possibility of nucleophilic addition to the vinyl group in quaternary ammonium salts, which provides evidence against the concept that such reactions involve d orbitals. The nucleophilic addition reaction was accomplished with triphenylphosphine and pyridine. In the latter case, the suggested reaction scheme was confirmed by the observation of the Wittig reaction under the action of carbon dioxide and the Stevens reaggangement involving the double bond of the pyridinium ring and migrating 2-phosphonioethyl group. Procedures for preparing the starting vinylpyridinium salts. Reaction schemes were siggested.