Construction of [1,4]oxazepin-2-ones via catalyst-free intramolecular C-O bond formation from Ugi adducts

A novel cyclization of Ugi adducts through a base-mediated system has been reported. The process entails an oxygen nucleophilic attack on the alkyl halide moiety, subsequently leading to an intramolecular cyclization. These consecutive reactions are straightforward to execute, occur under mild conditions, and do not require a catalyst. This catalyst-free attribute enhances the method's utility and eco-friendliness, rendering it an appealing approach for producing this significant category of heterocyclic compounds.