The Favorskii Rearrangement of α-Chloro Ketimines

Article abstract of DOI:10.1021/jo00370a018

The Favorskii rearrangement of α-chloro ketimines has been studied.It was shown that the base-induced rearrangement of α-chloro ketimines afforded imidates or amides via a mechanism involving 1,3-dehydrochlorination and ring-opening of the resulting cyclopropylideneamines.The ring-opening occurred in such a way as to produce the most stable carbanion.The entire mechanism paralleled the well-known cyclopropanone mechanism of the Favorskii rearrangement of the corresponding oxygen analogues, i.e., α-halo ketones.Evidence has been presented that the semibenzilic-type mechanism is not operative in the cases studied.Depending upon the reaction conditions and the substrate, the Favorskii rearrangement was accompanied by various side reactions including nucleophilic substitution, 1,2-dehydrochlorination, rearrangement via intermediate α-alkoxyaziridines, and self-condensation.