Sensitized ring-opening reactions of 3-(1-naphthyl)-2-(1-naphthalenemethyl)oxaziridine

The benzophenone (BP)-sensitized photolysis of the title compound (1) in oxygen-free acetonitrile and benzene gave 1-naphthaldehyde and N-(1-naphthoyl)-1-naphthalenemethylamine as main products along with small amounts of unidentified products. The occurrence of triplet-triplet energy transfer between BP and 1 at the diffusion-limited rate suggests the participation of triplet 1. from which the N-O bond cleavage as well as the N-O and C-N bond fissions in the three-membered ring proceeds to eventually yield the amine and the aldehyde. respectively. Control experiments using 1-naphthalenemethylazide showed the involvement of a triplet nitrene intermediate in appearance of the latter product. On the other hand, the 9,10-dicyanoanthracene (DCA)-sensitized reaction of 1 in nitrogen-purged acetonitrile was found to occur by an electron-transfer mechanism giving the product distribution that is different from that of the BP-sensitized reaction. No occurrence of the reaction in benzene confirms that the dissociated oxaziridine cation radical is a precursor of the products obtained. Significantly, the electron-transfersensitization of 1 in acetonitrile afforded 1-(nitromethyl)naphthalene as one of the products, being consistent with the mechanism in which atomic oxygen derived from the deoxygenation ofthe nitrone cation radical is captured by the nitrene intermediate. However, the deoxygenation reaction was not observed in methanol where only the aldehyde was detected. This interesting result was explained in terms of solvent effects on the stability of the oxaziridine cation radical as well as of the nitrene cation radical that was generated by the ring-opening reaction of the former cation radical.