Enantioselective Addition of Boronates to Acyl Imines Catalyzed by Chiral Biphenols
作者:Joshua A. Bishop、Sha Lou、Scott E. Schaus
DOI:10.1002/anie.200901023
日期:2009.6.2
On the big screen: A chiralbiphenol catalyst screening protocol was developed for the rapid identification of enantioselective nucleophilic boronate reactions with acylimines (see scheme). The approach successfully identified a unique catalyst for the reaction of aryl, vinyl, and alkynyl boronates. Mechanistic studies demonstrate boronate ligand exchange with the catalyst is necessary for activation
invertive B-alkyl Suzuki-Miyaura coupling has been achieved. The coupling of enantioenriched α-(acylamino)benzylboronic esters with aryl bromides and chlorides took place efficiently in toluene at 80 °C in the presence of Pd(dba)(2) (5 mol %), XPhos (10 mol %), K(2)CO(3) (3 equiv), and H(2)O (2 equiv). The reaction proceeded with inversion of configuration to give diarylmethanamine derivatives in high
Inversion or Retention? Effects of Acidic Additives on the Stereochemical Course in Enantiospecific Suzuki–Miyaura Coupling of α-(Acetylamino)benzylboronic Esters
The stereochemicalcourse of the stereospecific Suzuki-Miyaura coupling of enantioenriched α-(acetylamino)benzylboronic esters with aryl bromides can be switched by the choice of acidic additives in the presence of a Pd/XPhos catalyst system. Highly enantiospecific, invertive C-C bond formation takes place with the use of phenol as an additive. In contrast, high enantiospecificity for retention of
在 Pd/XPhos 催化剂体系的存在下,可以通过选择酸性添加剂来切换对映体富集的 α-(乙酰氨基)苄基硼酸酯与芳基溴的立体定向 Suzuki-Miyaura 偶联的立体化学过程。使用苯酚作为添加剂可形成高度对映体的、倒置 CC 键。相比之下,在 Zr(Oi-Pr)(4)·i-PrOH 作为添加剂存在的情况下,实现了构型保留的高对映特异性。