LEWIS ACID CATALYSIS OF PHOTOCHEMICAL-REACTIONS .8. PHOTODIMERIZATION AND CROSS-CYCLOADDITION OF COUMARIN
LEWIS ACID CATALYSIS OF PHOTOCHEMICAL-REACTIONS .8. PHOTODIMERIZATION AND CROSS-CYCLOADDITION OF COUMARIN
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DOI：
10.1021/ja00205a015
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发表时间：
1989-11-08
影响因子：
15
通讯作者：
BARANCYK, SV
中科院分区：
文献类型：
--
作者：
LEWIS, FD;BARANCYK, SV
本文研究了刘易斯酸络合作用对香豆素电子结构和光化学行为的影响。香豆素与BF 3或EtAlCl 2络合后IR和NMR光谱的变化表明刘易斯酸与羰基氧的1：1络合。从香豆素-BF 3复合物的UV光谱和室温荧光的观察的变化归因于，* 单重态相对于荧光，* 单重态的能量增加。二聚化被发现发生通过与基态香豆素的单线态或三线态复合物的反应。单重态反应选择性地产生顺式头-尾二聚体，而三重态反应产生反式头-头二聚体。单重态和三重态配合物也与简单烯烃反应。与异构2-丁烯的单重态复合物的加成在构型保留的情况下发生。与未络合的香豆素络合的增强的反应性归因于其增加的单重态寿命和亲电性。
The effect of Lewis acid complexation upon the electronicstructure and photochemical behavior of coumarin has been investigated. Changes in IR and NMR spectra upon complexation of coumarin with BF3 or EtAlCl2 are indicative of 1: 1 complexation of the Lewis acid with the carbonyl oxygen. Changes in the UV spectrum and the observation of room-temperature fluorescence from the coumarin-BF3 complex are attributed to increased energy of the,* singlet state relative to the fluorescent,* singlet state. Dimerization is found to occur via the reaction of either the singlet or triplet complex with ground-state coumarin. The singlet-state reaction selectively yields the syn head-to-tail dimer while the triplet-state reaction yields the anti head-to-head dimer. The singlet-and triplet-state complexes also react with simple alkenes. Addition of the singlet complex with the isomeric 2-butenes occurs with retention of configuration. The enhanced reactivity of complexed vs uncomplexed coumarin is attributed to its increased singlet-state lifetime and electrophilicity.