Department of Chemistry, WestChem, University of Glasgow, Glasgow G12 8QQ, UK.
Chemistry. 2013 Jul 8;19(28):9167-85. doi: 10.1002/chem.201203817. Epub 2013 Jun 6.
Detailed kinetic and computational investigation of the enantio- and diastereoselective allylation of aldehydes 1 with allyltrichlorosilanes 5, employing the pyridine N-oxides METHOX (9) and QUINOX (10) as chiral organocatalysts, indicate that the reaction can proceed through a dissociative (cationic) or associative (neutral) mechanism: METHOX apparently favors a pentacoordinate cationic transition state, while the less sterically demanding QUINOX is likely to operate via a hexacoordinate neutral complex. In both pathways, only one molecule of the catalyst is involved in the rate- and selectivity-determining step, which is supported by both experimental and computational data.
详细的动力学和计算研究表明，使用吡啶 N-氧化物 METHOX（9）和 QUINOX（10）作为手性有机催化剂，醛 1 与烯丙基三氯硅烷 5 的对映选择性和非对映选择性烯丙基化可以通过解离（阳离子）或缔合（中性）机制进行：METHOX 显然有利于五配位阳离子过渡态，而空间位阻较小的 QUINOX 可能通过六配位中性配合物进行反应。在这两种途径中，只有一种催化剂分子参与速率和选择性决定步骤，这得到了实验和计算数据的支持。
