A Green Chemistry Approach to a More Efficient Asymmetric Catalyst: Solvent-Free and Highly Concentrated Alkyl Additions to Ketones
作者:Sang-Jin Jeon、Hongmei Li、Patrick J. Walsh
DOI:10.1021/ja052200m
日期:2005.11.30
diastereoselectivities and high yields. Both the solvent-free asymmetricadditions and asymmetricaddition/diastereoselective epoxidation reactions have been conducted on larger scale (5 g substrate) with 0.5 mol % catalyst loadings. In these procedures, enantioselectivities equal to or better than 92% were obtained with isolated yields of 90%. The solvent-free and highly concentrated conditions are a significant improvement
对开发不仅高效和高度对映选择性而且对环境无害的催化剂体系有很大的需求。在此,我们报告了在高度浓缩和无溶剂条件下将烷基和官能化烷基催化不对称加成到酮上的研究。与使用甲苯和己烷的标准反应条件相比,无溶剂和高浓度条件允许催化剂负载减少 2 到 40 倍。这些新条件是通用的,适用于各种酮和二烷基锌试剂,以提供具有高对映选择性的各种叔醇。使用环状共轭烯酮,我们使用无溶剂加成条件进行了串联不对称加成/非对映选择性环氧化,然后引入 5.5 M 叔丁基过氧化氢 (TBHP) 癸烷溶液以生成环氧醇。这种一锅法允许获得具有三个连续立体中心的合成环氧醇,具有出色的对映选择性和非对映选择性以及高产率。无溶剂不对称加成和不对称加成/非对映选择性环氧化反应都已在更大规模(5 g 底物)上进行,催化剂负载量为 0.5 mol%。在这些程序中,以 90% 的分离产率获得了等于或优于 92% 的对映选择性。与以前基于溶剂的
Highly Active Chiral Phosphoramide−Zn(II) Complexes as Conjugate Acid−Base Catalysts for Enantioselective Organozinc Addition to Ketones
A highly efficient enantioselective organozinc (R2Zn) addition to ketones catalyzed by chiral phosphoramide-Zn(II) complexes (1-10 mol %) has been developed. These complexes serve as conjugate Lewis acid-Lewis base catalysts. Chiral phosphoramides are derived from an inexpensive natural amino acid (i.e., L-valine). From a variety of nonactivated aromatic and aliphatic ketones, the corresponding optically
Catalytic Asymmetric Addition of Alkylzinc and Functionalized Alkylzinc Reagents to Ketones
作者:Sang-Jin Jeon、Hongmei Li、Celina García、Lynne K. LaRochelle、Patrick J. Walsh
DOI:10.1021/jo048683e
日期:2005.1.1
We describe our full report of the catalytic asymmetricaddition of simple and functionalized dialkylzinc reagents to a broad range of saturated ketones and enones. The functionalized organozinc reagents contain esters, silyl ethers, alkyl chlorides, and alkyl bromides. In general, the resulting tertiary alcohol products are isolated with high ee's. With some substrates, yields are low as a result