PROPERTIES OF REACTIVE INTERMEDIATES GENERATED BY PHOTOCHEMICAL METHOD

研究了顺反光异构化、光重排和通过1，n-双自由基和激基复合物的光环加成反应中活性物种的光化学性质和直接观察，得到以下结果：1）带有一个或两个对乙酰基苯基的1，2-二苯基环丙烷衍生物的光照射引起顺反异构化，得到45：55光稳态，伴随着开环产物的形成，1，3-二苯基丙烯衍生物。纳秒级激光闪光光解表明，光异构化是通过三重态1，3-双自由基进行的，其寿命约为1000 nm。2）顺式和反式1-二苯基亚乙烯基-2，3-二甲基环丙烷在三重态敏化剂存在下或直接光照射下均发生顺反异构化。光稳态的顺反比在直接照射下为50：50，在光稳态下为30：50。3）在光辐射条件下，芘、菲等芳烃与肉桂酸甲酯、肉桂腈等缺电子烯烃反应，分别在芘的4，5-位和9，10-位菲的高产率。长时间照射含有芘和缺电子烯烃的溶液，有效地得到1：2加合物。芳烃与烯烃在适当位置发生分子内光环加成反应，更有选择性地生成（2π+ 2π）光环加成物。

Photochemical properties and direct observations of reactive species in cis-trans photoisomerizations, photorearrangements, and photocycloadditions via 1,n-biradicals and exciplexes were examined and the following results were obtained.1) Photoirradiation of 1,2-diphenylcyclopropane derivatives bearing one or two p-acetylphenyl group(s) caused cis-trans isomerization to give 45 : 55 photostationary state, accompanying with the formation of ring-opening products, 1,3-diphenylpropene derivatives. Nano-second order laser flash photolysis indicated that the photoisomerization proceeds via triplet 1,3-biradicals whose lifetimes are ca. 15 ns, and that the substituent effect at para position are negligible except for heavy atom effect by bromide group.2) Photoirradiation of cis- and trans-1-diphenylvinylidene-2,3-dimethylcyclopropane in direct or in the presense of triplet sensitizer caused cis-trans isomerization. Cis/trans ratios in photostationary states were 50 : 50 in direct irradiation, 30 : 70 in the presense of triplet sensitizer, respectively.3) Aromatic hydrocarbons such as pyrene and phenanthrene reacts with electron-deficient alkenes such as methyl cinnamate and cinnamonitrile under photoirradiation conditions, to give (2π+ 2π) photocycloadducts at 4,5-position of pyrene and 9,10-position of phenanthrene in high yields. Prolonged irradiation of a solution containing pyrene and electron-deficient alkene give 1 : 2 adduct efficiently. Intramolecular photocycloaddition of aromatic hydrocarbons connecting alkene moiety at appropriate position gave (2π+ 2π) photocycloadducts more selectively.