Sulfoximines are significant compounds that are found in pharmaceuticals, bioactive compounds, and agochemicals. Accordingly, the development of novel synthetic methods for sulfoximines and their modifications have become highly attractive. To date, many synthetic methods using these tools have been reported in the literature. These methods have focused mainly on the preparation of linear sulfoximines and their derivatives. However, synthetic approaches for the construction of cyclic sulfoximines have been relatively limited. We developed a novel synthetic method for indolo-1,2-benzothiazines via the Rh-catalyzed cyclization of S-aryl sulfoximines with 3-diazoindolin-2-imines together with the release of molecular nitrogen and p-toluenesulfonamide. The present method involved the N−H/C−H activation of S-aryl sulfoximines. A wide-ranging scope of both S-aryl sulfoximines and 3-diazoindolin-2-imines was demonstrated.