A Radical and An Electron Transfer Process Are Compared in Their Regioselectivities Towards A Molecule with Two Different C−I Bonds: Effect of Steric Congestion
作者:Barbara Branchi、Carlo Galli、Patrizia Gentili、Manuela Marinelli、Paolo Mencarelli
DOI:10.1002/1099-0690(200007)2000:14<2663::aid-ejoc2663>3.0.co;2-y
日期:2000.7
bonding interaction of the hindered C−I bond of 2a. This causes a remarkable regioselectivity toward the weaker bond in dehalogenation by stannyl radicals. Conversely, a much lower regioselectivity is found for a process −a photostimulated SRN1 reaction with the enolate ion of a ketone − which requires the conversion of 2a into a radical anion. A calculation of the BDE of the C−I bond for aa ArI•− system
1,4-二碘-2,6-二甲基苯 (2a) 中的空间压缩使甲基侧翼的 C-I 键比不受阻碍的 C-I 键弱得多(一种支撑效应)。计算还证实了 2a 的受阻 CI 键较弱的键合相互作用。这导致了对甲硅烷基自由基脱卤中较弱键的显着区域选择性。相反,发现一个过程的区域选择性要低得多 - 光刺激的 SRN1 反应与酮的烯醇离子 - 这需要将 2a 转化为自由基阴离子。提供了对 ArI•− 系统的 C−I 键的 BDE 计算。最后,由 2a•- 较弱的 C-I 键断裂产生的受阻芳基中间体在还原或取代之间显示出适度但可检测的区分,