The addition of organometallic reagents to carbonyl compounds has become a versatile method for synthesizing tertiary and secondary alcohols via carbon−carbon bond formation. However, due to the lack of good nucleophilicity or the presence of strong basicity of organometallic reagents, the efficientsynthesis of tertiary alcohols from ketones has been particularly difficult and, thus, limited. We recently
向羰基化合物中添加有机金属试剂已成为通过碳-碳键形成合成叔醇和仲醇的通用方法。然而,由于缺乏良好的亲核性或存在有机金属试剂的强碱性,由酮有效地合成叔醇特别困难并且因此受到限制。我们最近使用ZnCl 2,Me 3 SiCH 2开发了格氏试剂(RMgX:R =烷基,芳基; X = Cl,Br,I),对酮进行了高效的催化烷基化和芳基化反应MgCl和LiCl,可有效减少有问题的副反应。原则上,对于加成羰基化合物,RMgBr和RMgI的反应性不如RMgCl。因此,这种新颖的方法与均相催化的ZnCl 2 ·我3 SICH 2 MgCl·LiCl是相当有吸引力的,因为RMgBr和RMGI,其易于制备和/或可商购的,如RMgCl,可以成功地应用。除酮和醛以外,醛亚胺也有效地用于该催化反应,并以高收率获得了相应的仲胺。关于β-甲硅烷基效应和盐效应的机理细节,原位制备[R(Me 3 SiCH 2)2 Zn] -
Development of a Scalable Lanthanide Halide/Quaternary Ammonium Salt System for the Nucleophilic Addition of Grignard Reagents to Carbonyl Groups and Application to the Synthesis of a Remdesivir Intermediate
作者:Andrew C. Stevens、Katrien Brak、W. Stacy Bremner、Angela M. Brown、Andrei Chtchemelinine、Lars Heumann、James A. Kerschen、Witold Subotkowski、Tiago Vieira、Lydia C. Wolfe、Boran Xu、Chia-Yun Yu
DOI:10.1021/acs.oprd.1c00191
日期:2022.3.18
implementation of a scalable additive system, consisting of a lanthanide salt and a solubilizing quaternary ammonium salt, to improve the yield and robustness of the addition of an organomagnesium reagent to a ribonolactone en route to remdesivir. This system was found to be generally applicable in enhancing other challenging organomagnesium additions to enolizable and hindered carbonyl-containing compounds
The addition of Grignardreagents to ketones using sub-stoichiometric amounts of LaCl 3 ·2LiCl was studied. Catalytic amounts of LaCl 3 ·2LiCl (30 mol%) provide, in most cases, yields similar to those obtained using a stoichiometric amount.
Highly efficient alkylations and arylations of ketones with Grignard reagents (RMgBr and RMgI) have been developed using catalytic ZnCl(2), Me(3)SiCH(2)MgCl, and LiCl. Tertiary alcohols were obtained in high yields with high chemoselectivities, while minimizing undesired side products produced by reduction and enolization.