Electrophile-induced bromocyclization of γ,δ-unsaturated ketimines to intermediate 1-pyrrolinium salts and their selective conversion into novel 5-alkoxymethyl-2-aryl-3-chloropyrroles and 2-aroylpyrroles

Abstract

N-(1-Aryl-2,2-dichloropent-4-enylidene)amines were efficiently transformed into 5-bromomethyl-1-pyrrolinium bromides via electrophile-induced bromocyclization. The latter pyrrolinium salts were converted into novel 5-alkoxymethyl-2-aryl-3-chloropyrroles by reaction with alkoxides in the corresponding alcohol or in THF. This chemistry clearly deviates from the corresponding γ,δ-unsaturated α,α-dialkylaldimines under similar conditions. Furthermore, treatment of 5-bromomethyl-1-pyrrolinium bromides with sodium hydroxide in water afforded a new entry into 2-aroylpyrroles by an unexpected ring transformation of intermediate aziridine derivatives, which could be isolated as well.