An efficient [4+2]-annulation strategy, integrating PPh₃-mediated S–S bond cleavage of benzo[c][1,2]dithiol-3-ones with the Curtius rearrangement of acyl azides, has been developed for the construction of benzo[e][1,3]thiazine-2,4-diones. This protocol features mild reaction conditions, simple operation, excellent yields, feasible scalability, broad functional group tolerance, and practical applicability.