The facile synthesis of benzothiazolylideneacetates and 1,4-benzothiazines through a highly controllable oxidation of benzothiazolylacetates

The synthesis of benzothiazolylideneacetates and 1,4-benzothiazine was found to be highly controllable via simple exchange of corresponding oxidants. It turned out that the treatment of benzothiazolylacetates with m-CPBA gave 1,4-benzothiazines via oxidative ring expansion process, and with DDQ gave benzothiazolylideneacetates via dehydrogenation, in good yield, respectively. The structures of both skeletons were confirmed by their X-ray diffractions. A previously reported method for the synthesis of benzothiazolylideneacetates was thus proved to be incorrect.