Mechanistic Rationalization of Unusual Kinetics in Pd-Catalyzed C-H Olefination
Mechanistic Rationalization of Unusual Kinetics in Pd-Catalyzed C-H Olefination
复制标题
DOI：
10.1021/ja207634t
复制
发表时间：
2012-03-14
影响因子：
15
通讯作者：
Blackmond, Donna G.
中科院分区：
文献类型：
--
作者：
Baxter, Ryan D.;Sale, David;Blackmond, Donna G.
详细的动力学研究和新的图形操作的反应进展数据在Pd（II）催化的烯烃在单-N-保护的氨基酸配体的存在下，揭示异常的浓度依赖性（零阶o-CF 3-苯乙酸浓度，零阶氧压，和负序烯烃和产物浓度），离开催化剂浓度作为唯一的正驱动力的反应。NMR光谱研究支持这样的建议，即由烯烃底物和产物引起的速率抑制是由从活性循环中除去催化剂的可逆关闭循环储层的形成引起的。NMR研究比较的存在和不存在的配体的催化剂和底物之间的相互作用表明，弱配位的配体Pd防止形成一个非活性的混合乙酸盐物种。对这些特征的更全面的理解可能会导致为这种潜在的强大的C-H官能化反应设计更有效的Pd（II）催化剂。
Detailed kinetic studies and novel graphical manipulations of reaction progress data in Pd(II)-catalyzed olefinations in the presence of mono-N-protected amino acid ligands reveal anomalous concentration dependences (zero order in o-CF3-phenylacetic acid concentration, zero order in oxygen pressure, and negative orders in both olefin and product concentrations), leaving the catalyst concentration as the sole positive driving force in the reaction. NMR spectroscopic studies support the proposal that rate inhibition by the olefinic substrate and product is caused by formation of reversible off-cycle reservoirs that remove catalyst from the active cycle. NMR studies comparing the interaction between the catalyst and substrate in the presence and absence of the ligand suggest that weak coordination of the ligand to Pd prevents formation of an inactive mixed acetate species. A fuller understanding of these features may lead to the design of more efficient Pd(II) catalysts for this potentially powerful C-H functionalization reaction.