Mechanistic Dichotomy in the Asymmetric Allylation of Aldehydes with Allyltrichlorosilanes Catalyzed by Chiral Pyridine <i>N</i>
-Oxides
作者:Andrei V. Malkov、Sigitas Stončius、Mark Bell、Fabiomassimo Castelluzzo、Pedro Ramírez-López、Lada Biedermannová、Vratislav Langer、Lubomír Rulíšek、Pavel Kočovský
DOI:10.1002/chem.201203817
日期:2013.7.8
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
使用吡啶N-氧化物METHOX(9)和QUINOX(10)作为手性有机催化剂,对醛1与烯丙基三氯硅烷5进行对映和非对映选择性烯丙基化的详细动力学和计算研究表明,该反应可以通过离解性(阳离子)进行或缔合(中性)机理:METHOX显然偏爱五配位阳离子过渡态,而对空间要求不高的QUINOX则可能通过六配位中性配合物起作用。在这两种途径中,速率和选择性确定步骤都只涉及催化剂的一个分子,实验和计算数据都支持这一点。