A thiazine-S-oxide, Staudinger/aza-Wittig based synthesis of benzodiazepines and benzothiadiazepines

A new approach to the synthesis of imine containing 1,2,5-benzothiadiazepine-1,1-dioxides and 1,4-benzodiazepin-5-ones using iminophosphoranyl thiazine-S-oxides as precursors is reported. Key steps include a Staudinger reaction, an aza-Wittig reaction and the conversion of a thiazine-S-oxide into an amino ketone via a [2,3] sigmatropic rearrangement.