Mechanistic Analysis of Azine <i>N</i>-Oxide Direct Arylation: Evidence for a Critical Role of Acetate in the Pd(OAc)<sub>2</sub> Precatalyst
作者:Ho-Yan Sun、Serge I. Gorelsky、David R. Stuart、Louis-Charles Campeau、Keith Fagnou
DOI:10.1021/jo101821r
日期:2010.12.3
direct arylation of pyridine N-oxides are presented. The order of each reaction component is determined to provide a general mechanistic picture. The C−H bond cleaving step is examined in further detail through computational studies, and the calculated results are in support of an inner-sphere concerted metalation−deprotonation (CMD) pathway. Competition experiments were conducted with N-oxides of varying
提出了有关钯催化吡啶N-氧化物直接芳基化的详细机理研究。确定每个反应组分的顺序以提供一般的机理图。通过计算研究可以更详细地检查C H键的裂解步骤,计算结果支持内球协同的金属化-去质子化(CMD)途径。比赛实验用N-改变电子特性的氧化物,结果表明,当使用电子贫乏的物种时,速率得到了增强,这支持了CMD过渡态。还检查了碱对反应速率的影响,发现进行反应需要羧酸盐碱。由此得出的结论是,Pd(OAc)2在反应机理中起着举足轻重的作用,不仅是前催化剂,而且是CH键断裂步骤所需的乙酸盐碱的来源。