Photochemical Electron-transfer Reactions of Biphenyl-2,2′-dicarboximide and Naphthalene-1,8-dicarboximide with Olefin. Dependence of the Reaction Course on the Structure of the Aromatic Imide

Abstract

Abstract Photoreactions of N-methylbiphenyl-2,2′-dicarboximide and N-ethylnaphthalene-1,8-dicarboximide (2) with 1,1-diphenylethylene (3) in methanol gave methanol-incorporated 1 : 1 : 1-adduct (7) and 2,2-diphenylethyl methyl ether (6), an anti-Markovnikov adduct of methanol to 3. The ratio of the two types of products largely depends on the structure of the aromatic imides. Probably the spin densities of the radical anions of the aromatic imides seem to play an important role to determine the reaction courses after the photochemical electron-transfer process. Similar results were obtained in the photoreaction of N-(2-phenylallyl) aromatic imides; elimination induced by methanol-incorporation vs. anti-Markovnikov addition of methanol. Photoreactions of N-(trans-3-phenylallyl) aromatic imides in methanol gave methanol-incorporated O-cyclized products (20 and 27) and C-cyclized products (21 and 28). A tentative mechanism for the O-cyclization is proposed; i.e., intramolecular electron transfer followed by anti-Markovnikov addition of methanol to the radical cation of the double bond moiety, nucleophilic attack of the aromatic imide radical anion moiety, secondary electron-transfer, and then polar addition of methanol.