Pathways of photooxidation of 1,2,2,6,6-pentamethyl-4-piperidol by ketones

The photochemical oxidation of 1,2,2,6,6-pentamethyl-4-piperidol by ketones occurs exclusively at the methylamino group and, in the case of photolytically stable ketones, may lead to products of dimerization of the aminoalkyl radicals and recombination of the aminoalkyl and ketyl radicals and to a product of N-demethylation of the starting amino alcohol. When ketones that are unstable with respect to irradiation are used, photooxidation competes to a considerable extent with photodecomposition of such ketones. Spatial proximity of the aryl and α-methyl groups are observed for the products of reductive addition of the ketones on the basis of the PMR spectra.