Development of Diamidophosphite Ligands and Their Application to the Palladium-Catalyzed Vinyl-Substituted Trimethylenemethane Asymmetric [3 + 2] Cycloaddition
作者:Barry M. Trost、Tom M. Lam
DOI:10.1021/ja305717r
日期:2012.7.18
A palladium-catalyzed asymmetric [3 + 2] cycloaddition of a vinyl-substituted trimethylenemethane (TMM) donor with α,β-unsaturated acyl imidazoles is described. A newly designed bisdiamidophosphite ligand derived from (S,S)-trans-1,2-cyclohexanediamine and (2R,4R)-pentanediol has been instrumental for the development of this process. This transformation generates tetrasubstituted cyclopentanes bearing
Direct Visible-Light-Excited Asymmetric Lewis Acid Catalysis of Intermolecular [2+2] Photocycloadditions
作者:Xiaoqiang Huang、Taylor R. Quinn、Klaus Harms、Richard D. Webster、Lilu Zhang、Olaf Wiest、Eric Meggers
DOI:10.1021/jacs.7b04363
日期:2017.7.12
A reaction design is reported in which a substrate-bound chiral Lewisacid complex absorbs visible light and generates an excited state that directly reacts with a cosubstrate in a highly stereocontrolled fashion. Specifically, a chiral rhodium complex catalyzes visible-light-activated intermolecular [2+2] cycloadditions, providing a wide range of cyclobutanes with up to >99% ee and up to >20:1 d.r
报道了一种反应设计,其中底物结合的手性路易斯酸配合物吸收可见光并产生激发态,该激发态以高度立体控制的方式直接与共底物反应。具体来说,手性铑配合物催化可见光激活的分子间 [2+2] 环加成,提供各种环丁烷,其 ee 高达 >99%,dr 高达 >20:1 值得注意的是能够产生邻位全-碳四元立体中心,包括分子间形式的螺中心。
Enantioselective Addition of Remote Alkyl Radicals to Double Bonds by Photocatalytic Proton-Coupled Electron Transfer (PCET) Deconstruction of Unstrained Cycloalkanols
ring opening of unstrained cycloalkanols by a proton-coupled electrontransfer (PCET) process, to 2-acyl imidazoles previously coordinated to a rhodium-based chiral Lewis acid. High yields and enantioselectivites up to 99% are achieved in 1 h. Mechanistic investigations support the formation of the remote alkyl radical by a PCET process, and theoretical studies explain the observed stereochemistry