N-METHYL-N-PHENYLNITRENIUM ION FROM PHOTOLYSIS OF N-(METHYLPHENYLAMINO)-2,4,6-TRIMETHYLPYRIDINIUM TETRAFLUOROBORATE

The photochemical reactions of N-(methylphenylamino)-2,4,6-trimethylpy ridinium tetrafluoroborate were studied to find evidence of photodecom position to a nitrenium ion reactive intermediate. Stable products wer e formed that were consistent with a singlet-state methyphenylnitreniu m 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 f rom the N-methyl group of the nitrenium ion is also proposed based on the detection of aniline which would result from hydrolysis of the imi nium ion rearrangement product. The rate constant for this rearrangeme nt is estimated to be 10(8) s(-1). The reduction product, N-methylanil ine, is produced, and is believed to Form, st least in part, from the hydrogen atom abstractions of the triplet nitrenium ion. This is suppo rted by the results of triplet sensitized irradiations. Laser flash ph otolysis studies yielded the transient spectrum of a long-lived interm ediate absorbing st 470 nm, This transient species is believed to be t he cation radical of N methylaniline. (C) 1997 John Wiley & Sons, Ltd.