Synthesis of tri- and tetramethylene[b]pyrrole derivatives from 2-(1-ethoxy-2-bromoethyl)cycloalkanones
Tri- and tetramethylene[b]pyrrole derivatives were synthesized by treatment of the corresponding 2-(1-ethoxy-2-bromoethyl)cycloalkanones with an aqueous solution of sodium hydroxide and a methanol solution of a primary amine. The transformation proceeds through a step involving 1,3-dehydrobromination and opening of the three-membered ring in the intermediately formed spirocyclic ketones.