Photochemistry of Stable Pyridinyl Radicals. Photolysis of N-Alkyl-4-(carboalkoxy)pyridinyls

Article abstract of DOI:10.1021/jo00318a027

Photoinduced decomposition of N-benzyl-4-carbethoxypyridinyl (1a), N-methyl- (1b) and N-benzyl-4-(carbomethoxy)pyridinyl (1c), and their mixture was studied in degassed acetonitrile.N-benzyl homologues (1a and 1c) were smoothly photolyzed to ethyl (or methyl) isonicotinate by loss of a benzyl group, whereas the N-methyl homologue (1b) was comparatively stable toward UV light; the rate of disappearance of 1c relative to that of 1b was 11:1.A mechanism is postulated, which involves the formation of an alkyl radical by C-N bond homolysis followed by attack on the pyridinyl radical to form dihydropyridines.This is supported by a plot of the yield of ethyl isonicotinate vs. the ratio of initial concentrations <1b>₀/<1a>₀.Pyridinyl radicals 1 possess their absorption maxima at around 300, 395, and 630 nm; those at 300 and 395 nm maxima participate in this reaction.