研究了在新型DIPSkewphos / 3-AMIQ-Ru II配合物的催化下芳族γ-和δ-酮酯的不对称氢化为旋光羟基酯或二醇。在最佳条件下(8 atm H 2 ,Ru络合物/ t- C 4 H 9 OK = 1:3.5,25°C),用97–99定量获得了γ-和δ-羟基酯(包括γ-内酯)。 % ee。当反应在某些苛刻的条件下(20 atm H 2 ,[ t -C 4 H 9 OK] = 50 m m,40°C)进行时,得到的1,4-二醇和1,5-二醇主要是95 –99% ee。酯基的反应性特别取决于底物的两个羰基部分之间的碳间隔基的长度。不论反应条件如何,β-和β-酮酸酯的反应选择性地提供羟基酯。该催化剂体系用于γ-ϵ-二酮二酯加氢成三羟基酯的对映选择性和区域选择性(对于两个酯基之一)。
Acyl Radicals from α-Keto Acids Using a Carbonyl Photocatalyst: Photoredox-Catalyzed Synthesis of Ketones
作者:Da-Liang Zhu、Qi Wu、David James Young、Hao Wang、Zhi-Gang Ren、Hong-Xi Li
DOI:10.1021/acs.orglett.0c02351
日期:2020.9.4
Acylradicals have been generated from α-keto acids using inexpensive and commercially available 2-chloro-thioxanthen-9-one as the photoredox catalyst under visible light illumination. These reactive species added to olefins or coupled with aryl halides via a bipyridyl-stabilized Ni(II) catalyst, enabling easy access to a diverse range of ketones. This reliable, atom-economical, and eco-friendly protocol
Highlyenantioselectivehydrosilylation of γ-iminoesters with trichlorosilane promoted by a chiral Lewisbase proceeded smoothly to provide various optically active γ-amino esters in good yields (up to 96 %) with excellent enantioselectivities (up to 99 % ee) at –10 °C in Cl2CHCHCl2. The side reactions were successfully reduced by rational modification of the substrate. The absolute configuration