A New Method for Production of Chiral 2-Aryloxypropanoic Acids Using Effective Kinetic Resolution of Racemic 2-Aryloxycarboxylic Acids
作者:Isamu Shiina、Atsushi Tengeiji、Kenya Nakata、Keisuke Ono
DOI:10.3987/com-12-s(n)79
日期:——
We report a novel method for the preparation of 2-aryloxypropanoic acids by kinetic resolution of racemic 2-aryloxypropanoic acids using enantioselective esterification. The usage of pivalic anhydride (Piv(2)O) as an activating agent, bis(alpha-naphthyl)methanol ((alpha-Np)(2)CHOH) as an achiral alcohol, and (+)-benzotetramisole ((+)-BTM) as a chiral acyl-transfer catalyst enables the effective separation of various racemic 2-aryloxypropanoic acids to afford optically active carboxylic acids and the corresponding esters with high enantioselectivities. Furthermore, theoretical calculations of the transition states required to form the chiral esters successfully proved the enantiomer recognition mechanism of the asymmetric esterification.
Access to Optically Enriched α-Aryloxycarboxylic Esters via Carbene-Catalyzed Dynamic Kinetic Resolution and Transesterification
作者:Bin Liu、Runjiang Song、Jun Xu、Pankaj Kumar Majhi、Xing Yang、Song Yang、Zhichao Jin、Yonggui Robin Chi
DOI:10.1021/acs.orglett.0c00748
日期:2020.5.1
Disclosed here is a carbene-catalyzed dynamic kinetic resolution and transesterification reaction for access to this class of molecules with up to 99% yields and 99:1 er values. Addition of a chiral carbene catalyst to the ester substrate leads to twodiastereomeric azolium ester intermediates that can quickly epimerize to each other and thus allows for effective dynamic kinetic resolution to be realized
光学活性α-芳氧基羧酸及其衍生物是重要的功能分子。这里公开了一种卡宾催化的动态动力学拆分和酯交换反应,用于以高达 99% 的产率和 99:1 的 er 值获得这类分子。将手性卡宾催化剂添加到酯底物中会产生两种非对映体唑鎓酯中间体,它们可以快速彼此差向异构化,从而实现有效的动态动力学拆分。我们反应中的光学富集酯产物可以快速转化为手性除草剂和其他生物活性分子。
Chlorination of 2-Phenoxypropanoic Acid with NCP in Aqueous Acetic Acid: Using a Novel Ortho−Para Relationship and the Para/Meta Ratio of Substituent Effects for Mechanism Elucidation
作者:Manuel A. P. Segurado、João Carlos R. Reis、Jaime D. Gomes de Oliveira、Senthamaraikannan Kabilan、Manohar Shanthi
DOI:10.1021/jo0706224
日期:2007.7.1
beyond the aromatic ring. Activation enthalpies and entropies were estimated for substrates bearing the isoselective substituent in either ortho and para positions, being demonstrated that they are much different from the values for the parent substrate. The electrophilic attack on the phenolic oxygen atom by the protonated chlorinating agent is proposed as the rate-determiningstep, this step being followed