Unexpected sulfonylamino migration in the reactions of carbazole derivatives with fluoroalkanesulfonyl azides

The reactions of fluoroalkanesulfonyl azides with carbazole derivatives have been studied in detail. At room temperature reacted with 1,2,3,4-tetrahydrocarbazole readily to afford ring-contraction spiroindole derivatives together with an unexpected 4a-fluoroalkanesulfonylamino-1,2,3,4-tetra-hydrocarbazoles . However, in the case of 9-methyl-1,2,3,4-tetrahydrocarbazole , unexpected sulfonylamino migration occurred and a similar product 9-methyl-1-fluoroalkanesulfonylamino-2,3,4,9-tetrahydro-1H-carbazoles were obtained as major products in moderate yields. These new products were fully characterized by spectral methods and single X-ray diffraction analyses. Possible mechanisms for these reactions were proposed.