PHOTOLYSES OF (3-NAPHTHOXYPROPYL)COBALOXIME, (4-NAPHTHYLBUTYL)COBALOXIME, AND (4-NAPHTHYL-4-OXOBUTYL)COBALOXIME

The cobalt-carbon bond of the titled compounds is photochemically cleaved to generate an organoradical and a cobaloxime(II) radical pair. 3-(l- or 2-naphthoxy)propyl, 4-(l- or 2-naphthyl)butyl, and 4-(l- or 2-naphthyl)-4-oxobutyl radicals thus formed undergo three types of reactions: (a) hydrogen abstraction to give a saturated terminal, (b) hydrogen elimination to give a terminal olefin, and (c) substitution on the naphthalene ring. In benzene and radicals follow process b exclusively (the radicals from (3-(2-naphthoxy)propyl)cobaloxime (la), (3-(l-naphthoxy)propyl)cobaloxime (2a), and (4-(l-naphthyl)butyl)cobaloxime (2b)) or preferentially (the radicals from (4-(2-naphthyl)butyl)cobaloxime (lb), (4-(2-naphthyl)-4-oxobutyl)cobaloxime (1c), and (4-(l-naphthyl)-4-oxobutyl)cobaloxime (2c)). In chloroform, process a becomes important to the extent as the sum of the other two processes. In water-acetonitrile (4:1), process c becomes important and even takes precedence of others for the radicals from lb and lc. This feature is accounted for by the folding of the side chain of hydrophobic radicals. Encapsulation of the radicals in β-cyclodextrin stimulates process c except for the case of the radical from 2c. In the case of cobaloxime 2c, a-cyclodextrin does not affect the partition process of the intermediate radical. This feature is accounted for by the shallow inclusion of the radical due to the hydrogen bonding as depicted in Figure Id. © 1990, American Chemical Society. All rights reserved. © 1990, American Chemical Society. All rights reserved.