| Research Abstract |
The purpose of this investigation is to clarify the mechanism and applicability of [3+3]-photocycloaddition of arenedicarboxylic acid derivatives and alkylbenzenes. The results obtained are as follows :
1. From the investigations of the photoreactions of naphthalene derivatives, having acid anhydride, imide, diester, and dicyano groups at the 1,2-, 1,3- 1,4-, 2,3-, or, 1, 8-positions of the naphthalene ring, with alkylbenzenes, such as toluene, xylenes, and so on, [3+3]-photocycloaddition was found to be general in the reactions of naphthalene derivatives, having acid anhydride and imide group at the 1,8-positions of the naphthalene ring.
2. No [3+3]-photocycloadditions were observed in the reactions of arenedicarboxylic acid derivatives, having arene structure other that naphthalene, such as benzene, anthracene, or phenanthrene.
3. The quenching rate constants of the fluorescence of 1 , 8-naphthalenedicarboxylic anhydride and 1,8-naphthalenedicarboximide by alkylbenzenes were found to correlate well to the occurrence of the [3+3]-photoaddition.
4. The free energy change AG associated with one-electron transfer from alkylbenzenes to the singlet excited states of arenedicarboxylic acid derivatives were revealed to play an important role to determine the type of the observed photoreactions. A large negative AG value seems to be essential for the occurrence of the reaction.
5. From these results, possible reaction mechanism for the [3+3]-photocycloaddition, involving electron transfer from alkylbenzenes to the singlet excited states of arenedicarboxylic acid derivatives, proton transfer within the formed radical ion pair, electron transfer within the producedradical pair, and final thermal cycloaddition between the resulted anion and cation, was proposed. Applicability of the reaction and solvent effect on the reaction were reasonably explained by the reaction mechanism.
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