Construction of Si‐Stereogenic Silanols by Palladium‐Catalyzed Enantioselective C−H Alkenylation
摘要:
The construction of silicon‐stereogenic silanols via Pd‐catalyzed intermolecular C−H alkenylation with the assistance of a commercially available L‐pyroglutamic acid has been realized for the first time. Employing oxime ether as the directing group, silicon‐stereogenic silanol derivatives could be readily prepared with excellent enantioselectivities, featuring a broad substrate scope and good functional group tolerance. Moreover, parallel kinetic resolution with unsymmetric substrates further highlighted the generality of this protocol. Mechanistic studies indicate that L‐pyroglutamic acid could stabilize the Pd catalyst and provide excellent chiral induction. Preliminary computational studies unveil the origin of the enantioselectivity in the C−H bond activation step.
涉及 1,n-金属迁移的催化反应代表了一种通过激活 CH 键从简单前体合成复杂分子的有效方法。通过利用这一吸引人的特征,我们设计了一种钯催化合成 5H-二苯并 [b,f] silepins 的新成员,这是一类尚未开发但可能有用的硅桥接 π 共轭化合物。The reaction sequence is composed of 1,n-palladium migrations and unusual anti-carbopalladation of alkynes, which was realized by the proper choice of ligand for palladium. 进行了一系列氘标记实验以了解反应机理,以提出合理的催化循环。新获得的 5H-二苯并[b,f] silepins 表现出可调的光学和电子特性,
Rhodium-Catalyzed Asymmetric Synthesis of Silicon-Stereogenic Dibenzooxasilines via Enantioselective Transmetalation
作者:Ryo Shintani、Eleanor E. Maciver、Fumiko Tamakuni、Tamio Hayashi
DOI:10.1021/ja3076555
日期:2012.10.17
A rhodium-catalyzed asymmetric synthesis of silicon-stereogenic dibenzooxasilines has been developed. High enantioselectivities have been achieved by employing (S,S)-Me-Duphos as the ligand through "enantioselective transmetalation".