Laser Flash Photolysis Evidence for Styryl Radical Cation Cyclization in the SET-Induced Photorearrangement of a <i>p</i>-Methoxy-Substituted 2-Phenylallyl Phosphite
作者:Deepak Shukla、Cuong Lu、Norman P. Schepp、Wesley G. Bentrude、Linda J. Johnston
DOI:10.1021/jo0006775
日期:2000.9.1
second-order rate constants for its reaction with azide, chloride, and bromide ions and with the neutral nucleophile trimethyl phosphite. This study provides the first spectroscopic evidence regarding the proposed mechanism (Schemes 1 and 2) for the SET-induced photorearrangements of dimethyl 2-arylallyl phosphites to the corresponding 2-arylallylphosphonates. Moreover, absolute rate constants for the intramolecular
SET诱导的亚甲基2-(4-甲氧基苯基)烯丙基亚磷酸酯9(UV光,铀玻璃滤光片,9,10-二氰基蒽(DCA),联苯)的光重排产生膦酸酯12,分离产率为83%。在355 nm的含有DCA和联苯的亚磷酸酯9的氧饱和溶液中进行355 nm的激光快速照射,产生联苯自由基阳离子的瞬态UV光谱,该光谱通过亚磷酸酯9的电子转移而被淬灭(k(q)= 8.9 x 10(9)M -1)s(-1)在20摄氏度下)形成4-甲氧基苯乙烯基阳离子10。紫外光谱10的衰减一阶速率常数为8.0 x 10(6)s(-1),大概是中间体10的特征还在于通过测量与叠氮化物,氯化物,溴离子和中性亲核体亚磷酸三甲酯。这项研究提供了有关拟议的机制(方案1和2)的SET引起的第一个光谱学证据(方案1和2),SET诱导了2-芳基烯丙基二甲基亚甲基酯向相应的2-芳基烯丙基膦酸酯的光重排。此外,很少测量到烯烃自由基阳离子的分子内捕获的绝对速