Synthesis of 4H-1,4-benzothiazines via lithiation alpha to sulphur of 2-acylaminophenyl alkyl sulphides, sulphoxides, and sulphones
Abstract
4H-1,4-Benzothiazines, their monoxides, and their dioxides are readily prepared via lithiation and intramolecular cyclisation of 2-acylaminophenyl alkyl sulphides, sulphoxides, and sulphones with lithium di-isopropylamide in tetrahydrofuran at –50 °C.