Reaction of (E)-O-arylbenzaldoximes with sodium methoxide in methanol. Effect of leaving group upon nitrile-forming transition state
作者:Bong Rae Cho、Jinhee Jung、Eun Kyung Ahn
DOI:10.1021/ja00035a040
日期:1992.4
Reactions of (E)-O-arylbenzaldoximes 1-3 with MeONa-MeOH have been studied kinetically. The reactions proceed via competing E2 and S N Ar reactions, in which the first step is rate-determining. Although the reactions were strongly influenced by the electronic effect of the β- and O-aryl substituents, they were insensitive to the steric effect of the O-aryl group, except that the S N Ar reaction was
已经对 (E)-O-芳基苯甲醛肟 1-3 与 MeONa-MeOH 的反应进行了动力学研究。反应通过竞争的 E2 和 SN Ar 反应进行,其中第一步是速率确定。尽管反应受到β-和O-芳基取代基的电子效应的强烈影响,但它们对O-芳基的空间效应不敏感,除了SN Ar反应被2的CF 3 基团延迟。对于 MeONa-MeOH 促进的 1-3 消除,k H /k D 值增加,Hammett p 值随着离去基团的改善而降低
Reactions of (E)-O-arylbenzaldoximes with secondary amines in acetonitrile. Effect of .beta.-aryl substituents upon the competition between E2 and SNAr reactions
作者:Bong Rae Cho、Jong Tae Je
DOI:10.1021/jo00075a009
日期:1993.11
Reactions of (E)-O-arylbenzaldoximes in which the O-aryl group is 2,4-dinitrophenyl (1a-d) and picryl (2a-d) with secondary amines in acetonitrile have been studied kinetically. The reactions proceeded via competing E2 and S(N)Ar mechanisms. For eliminations from 1a-d promoted by R2NH in MeCN, the transition state was changed toward Elcb-like by a more electron-withdrawing beta-aryl substituent and a stronger base. On the other hand, the transition states for eliminations from 2a-d and for the S(N)Ar reactions of all substrates were relatively insensitive to the variation of either beta-aryl substituent or base strength. The yield of S(N)Ar product increased with base concentration, electron-withdrawing ability of the O-aryl group, and base strength. When the electron-withdrawing ability of the beta-aryl substituent is increased, the yield of S(N)Ar product from 1a-d decreased, although no clear trend was observed for 2a-d. From these results, factors that influence the competition between E2 and S(N)Ar reaction pathways are assessed.