An Accelerating−Reporting Group for Studies of Radical Heterolysis Reactions and Its Application in an Acid-Catalyzed Fragmentation Reaction of an α,β-Dimethoxy Radical
作者:Martin Newcomb、Neil Miranda
DOI:10.1021/jo0357972
日期:2004.10.1
parameters for reactions of 3b indicated that the rate-limiting step in the reaction was heterolytic cleavage. The 1,2-dimethoxy-1-methyl-2-(2,2-diphenylcyclopropyl)ethyl radical (26) reacted in a general acid-catalyzed heterolysis reaction, and rate constants for protonation of the β-methoxy group by a series of carboxylic acids were determined. The results suggest that acid-catalyzed reactions of β-alkoxy
2,2-二苯基环丙基用于加速含β-离去基团的α-甲氧基自由基的反应,以捕获离去基团的迁移或杂化产物,并为激光闪光光解动力学研究提供有用的发色团。报告小组将反应偏向于杂化裂解,最有可能拦截离子对中的自由基阳离子。1-甲氧基-1-甲基-2-(二乙基膦氧基)-2-(2,2-二苯基环丙基)乙基(3a)在仪器中的动力学拆分速度(k > 2×10 8 s - 1)快于研究的所有溶剂以及2-乙酰氧基类似物(3b)的反应比不包含环丙基的相关自由基的反应快得多(例如,在室温下,CH 3 CN中的k = 1.1×10 6 s - 1)。3b反应的速率常数和Arrhenius参数表明反应中的限速步骤是异源裂解。1,2-二甲氧基-1-甲基-2-(2,2-二苯基环丙基)乙基(26)在一般的酸催化杂解反应中反应,β-甲氧基的质子化速率常数由一系列测定了羧酸。结果表明,β-烷氧基自由基的酸催化反应可用于合成转化。