NBS-Promoted Synthesis of Thiocyanated Aminomaleimides and Site-Selective Intramolecular Cyclization Access to 1,4-Benzothiazepines via S–CN Bond Cleavage

A transition metal-free concise and efficient protocol for the synthesis of thiocyanated aminomaleimides and benzo[e][1,4]thiazepine derivatives has been developed. The method involves an initial α-C–H thiocyanation of aminomaleimides with KSCN and TEMPO-mediated tandem S–CN bond cleavage/intramolecular cyclization substitution processes, which enables the formation of seven-membered S/N-heterocycles. This synthetic strategy provides a reliable method for the synthesis of biologically interesting benzo[e][1,4]thiazepine derivatives by using KSCN as sulfur sources as well as expands the application of enaminones thiocyanation reactions in heterocycles synthesis.