Whereas 2H-benztriazoles are photochemically stable, 1 H-benztriazoles yield biradicals after splitting ofT nitrogen. These biradicals attack aromatic substratessuch as anisole, toluene, fluorobenzene or benzonitrile preferentially in the o-and p-positions with formation of the corresponding o-amino biphenyls (cf. schemes 2-5). With a deficiency of aromatic substrate, attack at the o-

1. Einleitung. -Im Rahmen unserer Untersuchungen uber das photochemische Verhalten von Indazolen [ 11, Anthranilen [2], Benzisoxazolen [3] und 2,l-Benzisothiazolen [4] in saurem Milieu bzw. protischen Losungsmitteln [4] interessierten wir uns auch fur die Photoreaktionen von 1-substituierten Benztriazolen in protischen und aprotischen, aromatischen Losungsmitteln, woruber wir vor langerer Zeit I)

In course of the investigation of photochemical behaviour of 2-isoxazolines, we observed that the irradiation of 3,5-diphenyl-2-isoxazoline ( l ) , in benzene solution, gave 4,5-diphenyl-3-oxazoline (2) and 8-amino-chalcone (3) in 7 and 5% yield, respectively [2].

Indazoles and anthranils on irradiation with a mercury high‐pressure lamp in acidic solution (H2SO4/H2O or H2SO4/CH3OH) yield 2‐amino‐5‐hydroxy(or methoxy)‐benzaldehydes (acetophenones, respectively) as major products and 2‐amino‐3‐hydroxy (or methoxy)‐benzaldehydes (acetophenones, respectively) as minor products. Photolysis of benzisoxazoles in conc. sulfuric acid results in the formation of 2,5‐and 2, 3‐dihydroxybenzaldehydes (acetophenones, respectively). 5‐Methylindazoles form on irradiation in diluted sulfuric acid 2‐amino‐5‐methyl‐benzaldehydes.