PHOTOCHEMISTRY OF 2-(METHOXYCARBONYL)PHENYL AZIDE STUDIED BY MATRIX-ISOLATION SPECTROSCOPY - A NEW SLIPPERY ENERGY SURFACE FOR PHENYLNITRENE

Broad-band irradiation (lambda > 350 nm) of 2-(methoxycarbonyl)phenyl azide (1) in Ar at 10 K monitored by IR and UV-vis spectroscopy resulted in the formation of at least rive major products, all of which were shown to be photointerconvertible under these conditions. The two products showing intact methoxycarbonyl carbonyl stretching absorption bands were assigned as (2-(methoxycarbonyl)phenyl)nitrene (2) and 3-(methoxycarbonyl)-1,2,4,6-azacycloheptatetraene (3), probably formed as a result of ring expansion of 2, while the products showing sharp absorption bands at 2118 and 2088 cm-1 due to ketene functional groups were assigned to the geometrical mixture of carbonyl oximino benzenes 16, presumably formed by formal 1,4-methoxy migration in 2, and the one showing carbonyl absorption at 1857 cm-1 was assigned as N-methoxyazetinone 15, produced as a result of photocyclization of 16. These assignments were unequivocally verified by generating the same reaction mixtures by photodecarbonylation of N-methoxyisatin (23) in an argon matrix at 10 K. That phenylnitrene-pyridylmethylene interconversions were not attained once the 2-methoxycarbonyl group was introduced was also shown.