Synthesis of 2-aryl-4-chloropyrroles via ring expansion of 2-aryl-1-chlorocyclopropanecarbaldehydes

An efficient electrophile-induced ring opening of 2-aryl-1-chlorocyclopropanecarbaldehydes is described towards halogenated butanals, which were converted to the corresponding imines. These α,α,γ-trichloroimines proved to be good substrates for a nucleophile-induced ring closure towards 2-pyrrolines as versatile synthons for the synthesis of pyrroles bearing physiologically interesting substitution patterns.