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 i on was examined with the goal of understanding the chemical behavior o f the intermediate nitrenium ion. Trapping experiments show that the c orresponding nitrenium ion is generated through an excited-state, elec trocyclic ring-opening reaction. Nucleophiles add to the aromatic ring of the nitrenium ion. In the absence of nucleophiles, two new product s are detected, the parent amine and an iminium ion. The latter result s 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 inc reased when triplet sensitization is used as the mode of photolysis. L ikewise, its yield is suppressed when triplet quenchers are employed. These experiments show that the reactions of the arylnitrenium ion dep end on its electronic spin configuration: the triplet favors formation of the parent amine, and the singlet favors rearrangement and nucleop hilic addition.