The mechanism for the rhodium-catalyzed decarbonylation of aldehydes: A combined experimental and theoretical study
The mechanism for the rhodium-catalyzed decarbonylation of aldehydes: A combined experimental and theoretical study
复制标题
DOI：
10.1021/ja710270j
复制
发表时间：
2008-04-16
影响因子：
15
通讯作者：
Madsen, Robert
中科院分区：
文献类型：
--
作者：
Fristrup, Peter;Kreis, Michael;Madsen, Robert
通过实验技术（哈米特研究和动力学同位素效应）研究了铑催化醛脱羰的机制，并通过计算研究（DFT 计算）进行了扩展。对于苯甲醛和苯乙醛衍生物，获得线性哈米特图，正斜率分别为+0.79和+0.43，这表明在选择性确定步骤中负电荷的积累。这些底物的动力学同位素效应相似（苯甲醛和苯乙醛分别为 1.73 和 1.77），表明相似的机制正在发挥作用。催化循环的 DFT (B3LYP) 研究表明，C(O)-H 键中发生快速氧化加成，然后是 CO 的限速挤出和还原消除。基于该机制的理论动力学同位素效应与两种底物的实验值非常一致，但仅当选择 00 的迁移挤出作为速率决定步骤时。
The mechanism for the rhodium-catalyzed decarbonylation of aldehydes was investigated by experimental techniques (Hammett studies and kinetic isotope effects) and extended by a computational study (DFT calculations). For both benzaldehyde and phenyl acetaldehyde derivatives, linear Hammett plots were obtained with positive slopes of +0.79 and +0.43, respectively, which indicate a buildup of negative charge in the selectivity-determining step. The kinetic isotope effects were similar for these substrates (1.73 and 1.77 for benzaldehyde and phenyl acetaldehyde, respectively), indicating that similar mechanisms are operating. A DFT (B3LYP) study of the catalytic cycle indicated a rapid oxidative addition into the C(O)-H bond followed by a rate-limiting extrusion of CO and reductive elimination. The theoretical kinetic isotope effects based on this mechanism were in excellent agreement with the experimental values for both substrates, but only when migratory extrusion of 00 was selected as the rate-determining step.