Highly Regioselective Synthesis of Tetrahydro-2<i>H</i>-1,3-thiazin-2-ones via Rhodium-Catalyzed Carbonylation of <i>N</i>-Alkylisothiazolidines

The [Rh(COD)Cl]2- and KI-catalyzed carbonylation of functionalized N-alkylisothiazolidines in toluene gives the corresponding tetrahydro-2H-1,3-thiazin-2-ones in good yield. The carbonylation reaction occurred site-selectively at the S−N bond of the isothiazolidine ring. The reaction is believed to proceed via oxidative addition, followed by CO insertion and reductive elimination to form the tetrahydro-2H-1,3-thiazin-2-one derivatives.