Photo-Induced Reactions of Oxime O-Ethers Derived from 3-Acyl-1,2-dihydrocinnoline-1,2-dicarboximides

Article abstract of DOI:10.1246/bcsj.69.3533

The irradiation of oxime O-ethers 2, derived from N-substituted 3-acyl-1,2-dihydrocinnoline-1,2-dicarboximides in benzene, afforded rearranged products 3 possessing a [1,3,5]triazino[1,2-a]indole skeleton in good yields. Upon irradiation, 7-methoxy-substituted 1,2-dihydrocinnoline-1,2-dicarboximides 2 gave a novel dimer 5 together with the rearranged triazinoindole derivatives 3 in benzene, while in nucleophiles they gave the nucleophile-incorporated dihydrotriazinoindoles 6. However, the 7-nitro-substituted one was inert under the same conditions. The dimer and dihydrotriazinoindole derivatives were thought to be formed by a nucleophilic attack of the initial photoproduct 3 and nucleophiles to 2, respectively. From these results and the observation of a remarkable solvent-dependency of the fluorescence and UV spectra of 2, it was suggested that these photoreactions should occur through a nitrogen-nitrogen bond cleavage at polar excited states followed by skeletal rearrangements.