PHOTOGENERATED ARYLNITRENIUM IONS - PHOTOISOMERIZATION OF THE N-TERT-BUTYL-3-METHYLANTHRANILIUM ION AND SPIN-SELECTIVE REACTIVITY OF THE ISOMERIC ARYLNITRENIUM ION

The photochemical behavior of the N-tert- butyl-3-methylanthranilium ion was examined with the goal of understanding the chemical behavior of the intermediate nitrenium ion. Trapping experiments show that the corresponding nitrenium ion is generated through an excited-state, electrocyclic ring-opening reaction. Nucleophiles add to the aromatic ring of the nitrenium ion. In the absence of nucleophiles, two new products are detected, the parent amine and an iminium ion. The latter results from a [1,2]-sigmatropic shift of a methyl group from the tert-butyl residue to the nitrenium nitrogen. Yields of the parent amine are increased when triplet sensitization is used as the mode of photolysis. Likewise, its yield is suppressed when triplet quenchers are employed. These experiments show that the reactions of the arylnitrenium ion depend on its electronic spin configuration: the triplet favors formation of the parent amine, and the singlet favors rearrangement and nucleophilic addition.