Intramolecular Hydrogen Transfer in (2-Aminophenyl)carbene and 2-Tolylnitrene. Matrix Isolation of 6-Methylene-2,4-cyclohexadien-1-imine

Article abstract of DOI:10.1021/jo00125a024

Flash vacuum pyrolysis (FVP) or matrix photolysis of 2-(diazomethyl)phenylamine, 1-azido-2-methylbenzene (2-tolyl azide), o-aminobenzyl alcohol, or 2-indolinone provide entries into the C7H7N hypersurface.The matrix-isolated (argon, 10 K) products have been characterized by IR and UV-vis spectroscopy in combination with high level (MP2/6-31G(d) and HF/6-31G(d,p)) ab-initio calculations.FVP (500-800 deg C) of the first three of these precursors produces high yields of E/Z-mixtures of 6-methylene-2,4-cyclohexadien-1-imine (o-iminoquinone methide), while the bicyclic isomer benzoazetine is not formed under these conditions.FVP of 2-tolyl azide at very high temperatures (>900 deg C) leads to the formation of benzaldimine and benzonitrile.Photolysis of the matrix-isolated precursors allows one to selectively generate the E- and Z-isomer of the iminoquinone methide as well as benzoazetine.In addition, 2-tolylnitrene and 1-aza-3-methyl-1,2,4,6-cycloheptatetraene are produced as intermediates in the photolysis of 2-tolyl azide.The nitrene is thermally stable up to 80 K (in xenon matrix), although the hydrogen migration to give (E)-o-iminoquinone methide is calculated to be exothermic by 42 kcal/mol.Irradiation of 2-(diazomethyl)phenylamine directly yields the quinone methide while (o-aminophenyl)carbene, which is the most reasonable intermediate, is not observed.