new class of pyridine catalyst for asymmetric acylation of sec-alcohols having a conformation switch system in which interconversion between self-complexation and uncomplexation is induced by acylation and deacylation steps, respectively. Kinetic resolution of various sec-alcohols is performed by the asymmetric acylation with isobutyric anhydride using 0.05 to 0.5 mol % catalyst 1a with s values of up
我们已经开发了用于具有构象转换系统的仲醇的不对称酰化的新型吡啶催化剂,在该构象转换系统中,分别通过酰化和脱酰步骤引起自复合和非复合之间的相互转化。各种仲醇的动力学拆分通过异丁酸酐的不对称酰化反应使用0.05至0.5 mol%的催化剂1a(s值最高为30)进行。此外,dl-二醇也以相似的方式以良好的选择性拆分。此外,在存在0.5-5 mol%催化剂的情况下,内消旋-1,X-二醇(X = 2-6)不对称脱对称1a。在1 H NMR测量,X射线结构分析以及AM1和DFT计算的基础上,提出了反应机理的工作模型,其中构象转换系统由吡啶环与环之间的分子内阳离子-π相互作用控制。硫羰基将在获得良好的选择性和高催化活性方面起关键作用。
Kinetic resolution of sec-alcohols by a new class of pyridine catalysts having a conformation switch system
作者:Shinji Yamada、Tomoko Misono、Yuko Iwai
DOI:10.1016/j.tetlet.2005.02.019
日期:2005.3
The catalysts having a conformation switch system induced by acylation and deacylation serve as asymmetric acylating catalysts of sec-alcohols. The kinetic resolution of various sec-alcohols resulted in good to excellent selectivities in the presence of 0.5 to 0.05 mol % of catalyst 1a. The conformation switch system plays a key role to attain both good selectivity and high catalytic activity. (c) 2005 Elsevier Ltd. All rights reserved.
Arylboronic Acid-Catalyzed Racemization of Secondary and Tertiary Alcohols
作者:Gregory R. Boyce、Stefania F. Musolino、Jianing Yang、Andrew D. Smith、James E. Taylor
DOI:10.1021/acs.joc.2c01602
日期:2022.10.7
The use of 2-carboxyphenylboronic acid (5 mol %) and oxalic acid (10 mol %) with 2-butanone as a solvent for the racemization of a range of enantiomerically pure secondary and tertiaryalcohols is demonstrated. The process is postulated to proceed via reversible Brønsted acid-catalyzed C–O bond cleavage through an achiral carbocation intermediate.