Carbazolyl nitrenium cations: Generation and reactions

Carbazolyl nitrenium cations were generated during the thermolysis and phot olysis of 1-carbazol-9-yl-2,4,6-triphenylpyridinium (Py+-Cz) tetranuorobora te in 2,2,2-trinuoroethanold- and TFA-mesitylene mixtures. The thermolysis of Py+-Cz in TFA-mesitylene mixture gave 9-mesitylcarbazole in good yield a long with carbazole, non-symmetrical mesitylene dimer, 2,4,6-triphenylpyrid ine, and a small amount of 9-(3,5-dimethylbenzyl)carbazole, whereas the the rmolysis in trifluoroethanol - mesitylene mixture gave 9-mesitylcarbazole a s the main product along with carbazole and 2,4,6-triphenylpyridine. The pr o duct distributions lead to two major conclusions. First, photolysis and t hermolysis of Py+-Cz salt produce nitrenium ions that can be in singlet or triplet state dependant on the reaction conditions. Second, the carbazolyl nitrenium ion exhibits singlet state in the ground state.