FORMATION OF TRIPLET BIRADICALS BY [3+2]-PHOTOCYCLOADDITION OF ARENES WITH ALKENES

芳烃与烯烃的[3 2]-光环加成反应形成三重态双自由基

• 批准号: 11640534
• 负责人: KUBO Yasuo
• 金额: $ 1.6万
• 依托单位: SHIMANE UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1999
• 资助国家: 日本
• 起止时间: 1999 至 2000
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11640534/
• 关键词: CYCLOADDITIONS; PHOTOCHEMICAL REACTIONS; TRIPLET BIRADICALS; NON-KEKULE STRUCTURE; ESR; ACID DERIVATIVES; ESTERS; NITRILES

The purpose of this investigation is to clarify the features of the formation of triplet biradicals by [3+2]-photocycloaddition of arenes and alkenes.The results obtained are as follows :1. The [3+2]-photocycloaddition of dimethyl 1, 4-naphthalenedicarboxylate (1) and alkenes was found to occur from the singlet excited state of 1 possibly through a zwitter-ionic intermediate. On the other hand, the photoreactions in the presence of a radical scavenger, such as oxygen and fumaronitrile, radical scavengeradded [3+2]-cycloadducts were obtained in concomitant loss of the formation of the [3+2]-cycloadducts. Control examinations indicated that the [3+2]-adducts were not the precursors of the adducts of the radical scavenger. A mechanism on the formation of the adducts, involving a triplet biradical intermediate occurred from the zwitter-ionic intermediate, was proposed. From the investigations of the photoreactions of various arenes and alkenes, the formation of the triplet biradicals was found to be efficient in the photoreactions of aromatic esters and alkenes, having aromatic substituents, such as styrene, in less polar solvents, such as benzene and carbon tetrachloride, at low temperature.2. The corresponding intramolecular photoreactions revealed that the triplet biradicals were also effectively formed in the intramolecular reactions in less polar solvents at low temperature.3. The quenching rate constants of the fluorescence of 1 by the alkenes were measured and a large rate constant was found to be essential for the effective formation of the triplet biradicals. On the other hand, no effective fluorescence quenching was observed in the quenching by the radical scavengers.4. The molecular orbital calculation revealed that the triplet biradicals, obtained by approaching of the alkene units to the 1, 8-position of the naphthalene ring of 1, were more stable (11-18 kcal/mol) than the corresponding singlet zwitter-ionic intermediates.

这项研究的目的是通过[3+2] - 竞技场和烯烃的photocyclocyctition阐明三胞胎Biradicals形成的特征。获得的结果如下：1。发现[3+2] - 二甲基1、4-萘二甲基二苯甲酸盐（1）和烷烃的载量载量可能是从1个单重击状态发生的，这可能是通过Zwitter-Irom-Irom-Irenic中间体出现的。另一方面，在存在自由基清除剂的情况下，例如氧和富马烯烃，自由基的清除[3+2] - 循环载体，是在同时形成[3+2] -Cycloaducts的形成中获得的。对照检查表明，[3+2] adducts不是自由基清道夫加合物的前体。提出了一种关于加合物形成的机制，涉及来自Zwitter-Ir-Ir-Intim中级的三胞胎中间体。从对各种领域和烷烃的光反应的研究中，发现三胞胎的形成在芳族酯和烯烃的光反应中有效，具有芳族取代基，例如苯乙烯，例如较小的极性阳极，例如苯和碳苯甲苯和碳苯甲酸碳纤维，在低温温度下。相应的分子内光反应表明，在低温下极性溶剂的分子内反应中也有效地形成了三胞胎。3。测量了烯烃的荧光1荧光速率常数，发现大型速率常数对于有效形成三胞胎Biradicals至关重要。另一方面，自由基清除剂在淬火中未观察到有效的荧光猝灭。4。分子轨道计算表明，通过将烯烃单位接近1的1，8位，比相应的单元Zwitter-Irimenic Medimediates更稳定。