C‐N vs. C‐C Bond Photodissociation in N‐(tert‐butyldiphenylmethyl)aniline

Abstract

The direct photolysis of the title aniline compound Ph2(Me3C) C‐NHPh in acetonitrile with 248 nm laser light results in the dissociation of the C‐N bond giving the corresponding (tert‐Bu)diphenylmethyl radical 1a• and the anilino radical PhNH• detectable by ns‐laser flash photolysis (LFP) and ESR spectroscopy. The same radical 1a• is also produced from the corresponding (tert‐Bu)diphenylmethyl chloride Ph2(Me3C)C‐Cl either photolytically in MeCN through C‐Cl bond homolysis or pulse radiolytically in THF; the (tert‐Bu)diphenylmethyl cation is also detected, however, at sorter time scales because of its high reactivity in the solvent MeCN. At higher laser pulse intensities the radical 1a• is reexcited by a second photon leading through electrocyclization to the 4a,4b‐dihydro‐9‐tert‐butylfluorenyl radical (DHBF•) and finally to fluorenyl products. Product analyses of steady state photolyses using GC and GC‐MS gave as principal products (tert‐Bu)diphenylmethane, aniline and various 9‐substituted fluorenyl derivatives, corroborating further the primary C‐N bond cleavage and the formation of the radicals 1a• and PhNH•. Other conceivable dissociation pathways leading to the C‐CMe3 or N‐H bond rupture were not observed.