Evidence for the formation of oxaziridines during the irradiation of oximes

Compared to the photochemistry of ketones, that of oximes has not been studied so extensively and a few papers dealing with the photoexcited state (2) and mode of the photoreaction of oximes, e.g., the syn-anti isomerization (3), the Beckmann type rearrangement leading to carboamides (2c, 4), and the formation of nitriles (5) have been reported. We have discovered a new photoreaction of oximes, the formation of oxaziridines, which was suggested without evidence by de Mayo as an intermediate in the photoreaction of benzaldoxime to benzamide (6). We chose oxime (I) of l,ldimethyl-2-naphthalenone (II) because of its absorption maximum above 300 rnp and of stability of the expected photoproducts. Although there are two geometrical isomers of I, the syn-form (Ia), m.p. 103-4", and anti-form (IS), m.p. 133-5" (7), irradiation induced interconversion between the two isomers. When a solution of the oxime (Ia) was irradiated in a Pyrex vessel using a high pressure mercury lamp (Toshiba H400-P), the absorption maximum of Ia at 307 rnp was replaced by that of a photoproduct (III) at 274 mu. Although the photoproduct (III) seems to be stable when it is in dilute solution (less than 0.01 M) (8), it failed to isolate III upon evaporation of the solvent. Evaporation of the irradiated solution of Ia resulted in decomposition of III, and afforded an unsaturated ketone (II)(yield 54 $), a saturated ketone (IV)(6.4 $), a carboamide (V)(9), m.p. 141-3" (4 $), and recovered oximes (Ia and Ip)(S $) accompanied with nitrogen and hydrazine. On the other hand, when the irradiated solution was hydrogenated immediately in the presence of Pd-C, the saturated ketone (IV)(27 $), the carboamide (V)(5 9) and a saturated alcohol (VI), m-p. 88-g" (39 $), were