Formation of Four-Membered Heterocycles through Electrophilic Heteroatom Cyclization

Abstract

This review demonstrates the feasibility of the formation of cyclobutane heterocycles through 4-endo and 4-exo electrophile-induced processes. Cyclizations are usually observed upon treatment of linear substrates with electrophiles such as halogens (chlorine, bromine, iodine), haloreagents {NBS, [bis(collidine)X+]Y−, ...}, and more rarely with seleno reagents and metallic salts. Results show that the formation of β-lactones, oxetanes, and β-lactams can be viewed as a general process useful for synthetic purposes. Formation of azetidines and thietanes appears more limited and has been reported in only a few cases. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)