Bromoethylsulfonium Salt—A More Effective Annulation Agent for the Synthesis of 6- and 7-Membered 1,4-Heterocyclic Compounds

Reaction of bromoethylsulfonium salt with 1,2-/1,3-aminoalcohols gave six- and seven-membered rings in good-to-excellent yields. The reactions proceed through generation of a vinyl sulfonium salt followed by annulation to give 1,4-heterocyclic compounds such as morpholines and benzoxazepines in a simple procedure. The method accommodates a range of nitrogen substituents and the amino alcohol can be substituted by amino thiols and diamines to give thiomorpholines, piperazines and benzodiazepines.