Reaction Pathway for the Formation of 3,3-Diphenyl-1-benzenesulfonamidopropane in the Aluminum Chloride Catalyst Reaction of 1-Benzenesulfonyl-2-(bromomethyl)ethylenimine and Benzene

Article abstract of DOI:10.1021/jo00333a023

The Friedel-Crafts reaction of 1-benzenesulfonyl-2-(bromomethyl)ethylenimine-2-(14)C and benzene yields 3,3-diphenyl-1-benzenesulfonamidopropane-2-(14)C.This finding, coupled with the results of an earlier tracer study, shows that the order of atoms in the three-carbon chain of the starting etylenimine persists unchanged in the product.If so, a previously suggested pathway becomes unacceptable.Of the several test compounds exposed to the action of aluminum chloride and benzene as described in the present work, only 1-benzenesulfonyl-2-benzylethylenimine and 1-benzenesulfonyl-2-phenylazetidine gave 3,3-diphenyl-1-benzenesulfonamidopropane.Since the azetidine compound could be eliminated as an intermediate in the ethylenimine process, this left only the benzyl derivative as an eligible intermediate.These data led to a revised pathway, which accommodates all the facts.An early stage in the mechanism is taken as conversion of the ethylenimine starting material to 1-benzenesulfonyl-2-benzylethylenimine.Under the reaction conditions, the latter compound generates a carbocationoid center on the middle carbon atom of its three-carbon chain.By a 1,2 hydride shift, this carbocation rearranges to the more stable benzylic carbocation, which combines with benzene to form the final product.