The effective formation of 1-azabicyclo [3.1. 0] hexane (5) by treatment of 2-(bromomethyl) pyrrolidine hydrobromide (4) with n-BuLi was established, with the reaction occurring by a rational reaction pathway via the open chain transition state 8 based on intermolecular Br··· Li+ coordination (SN2 process). The reaction of 5 with electrophiles 13a—n gave the corresponding pyrrolidines 14a—n and piperidine 6, 15a—g, i—n. The selectivity of the ...