N-methyl-N-phenylnitrenium ion from photolysis ofN-(methylphenylamino)-2,4,6-trimethylpyridinium tetrafluoroborate

The photochemical reactions of N-(methylphenylamino)-2,4,6-trimethylpyridinium tetrafluoroborate were studied to find evidence of photodecomposition to a nitrenium ion reactive intermediate. Stable products were formed that were consistent with a singlet-state methylphenylnitrenium ion precursor. The methoxy and chloro adducts. N-methyl-p-anisidine and 4- (and 2-)chloro-N-methylaniline, were identified and quantified by high-performance liquid chromatographic analysis. A hydride shift from the N-methyl group of the nitrenium ion is also proposed based on the detection of aniline which would result from hydrolysis of the iminium ion rearrangement product. The rate constant for this rearrangement is estimated to be 108 s−1. The reduction product, N-methylaniline, is produced, and is believed to form, at least in part, from the hydrogen atom abstractions of the triplet nitrenium ion. This is supported by the results of triplet sensitized irradiations. Laser flash photolysis studies yielded the transient spectrum of a long-lived intermediate absorbing at 470 nm. This transient species is believed to be the cation radical of N-methylaniline.