Organophosphine-Mediated Skeletal Editing Synthesis of Benzo[e][1,3]thiazine-2,4(3 <i>H</i> )-diones via Curtius Rearrangement

An organophosphine-promoted skeletal reorganization of benzo[c][1,2]dithiol-3-ones to forge benzo[e][1,3]thiazine-2,4(3H)-diones is demonstrated herein. This cascade reaction involves S–S bond cleavage followed by formal [4 + 2] cycloaddition of benzo[c][1,2]dithiol-3-ones and isocyanates, which are generated in situ through the Curtius rearrangement of acyl azides or dioxazolones beyond the formation of N-acyl nitrenes. The newly developed S to C–N exchange strategy endows the efficient assembly of diverse benzo[e][1,3]thiazine-2,4-diones under mild conditions, which avoids transition metals and inert gas protection, featuring a simple reaction setup to achieve decent yields while allowing for both late-stage diversification and practical scalability.