The SN2 reaction between diastereomerically enriched (R)-pantolactone (S)-α-bromoesters and sodium p-chloroaryloxide affords chiral aryloxy esters. Depending on the solvent used in the reaction, the diastereomeric ratios could be strongly modified or inverted. In DMSO, the epimerization can be prevented and the (R)-aryloxy esters are obtained with good diastereomeric ratios.
Dynamic resolution of α-halo chiral esters for the synthesis of 3-substituted piperazin-2-ones
作者:Jung In Jang、Seock Yong Kang、Kyoung Hee Kang、Yong Sun Park
DOI:10.1016/j.tet.2011.06.055
日期:2011.8
Dynamicresolution of α-halo esters derived from five chiral alcohols has been investigated in nucleophilicsubstitution with ethylenediamine nucleophiles. Stereoselective substitution of α-halo esters and following spontaneous cyclization provide a practical protocol for asymmetricsyntheses of 3-substituted piperazin-2-ones up to 94:6 er.
Dynamic kinetic resolution (DKR) using immobilized amine nucleophiles
作者:Yevgeny Valenrod、Jinnie Myung、Robert N Ben
DOI:10.1016/j.tetlet.2004.02.004
日期:2004.3
The first example of a dynamic kinetic resolution (DKR) using immobilized amine nucleophiles is described. This approach utilizes a nucleophilic amine attached to a solid phase resin via an organic spacer. The optical purities of the N-substituted α-amino ester products are superior to the solution phase DKR with diastereomeric ratios ranging from 11:1 to 18:1 and chemical yields between 66% and 98%