Acid‐Catalyzed/Mediated Synthesis of Benzo[ d ][1,3]oxathiin‐4‐Ones and Their Deuterated Analogs

A novel synthetic strategy for benzo[ d ][1,3]oxathiin‐4‐ones has been developed using HI as a critical catalyst. A variety of benzo[ d ][1,3]oxathiin‐4‐ones were isolated in excellent yields via the reaction between thiosalicylic acids and aldehydes or ketones. Furthermore, with HBr as an additive, DABCO·CD 2 Cl 2 was utilized as a deuterated methylene (methylene‐ d 2 ) source, enabling the efficient synthesis of deuterated analogs in good yields and excellent deuterium incorporation. This method features broad substrate scope, good functional group tolerance, and gram‐scale scalability, providing a valuable complementary approach for accessing the important benzo[ d ][1,3]oxathiin‐4‐ones and their deuterated analogs.