Catalytic Asymmetric Intermolecular Bromoesterification of Unfunctionalized Olefins
作者:Lijun Li、Cunxiang Su、Xiaoqin Liu、Hua Tian、Yian Shi
DOI:10.1021/ol501542r
日期:2014.7.18
An asymmetric intermolecular bromoesterification of unfunctionalized olefins catalyzed by (DHQD)2PHAL is described. Optically active bromoesters can be obtained with up to 92% ee.
Intermolecular haloesterification is an important class of transformations. The resulting products are valuable building blocks. However, it is often necessary to use super-stoichiometric amount of acid in order to compensate the low reactivity. Herein, we report a zwitterion-catalyzed intermolecular bromoesterification using acid and olefin in an equimolar ratio. Mechanistic study revealed that the charge pair in the zwitterion works synergistically in activating both NBS and carboxylic acid.
Surmounting Byproduct Inhibition in an Intermolecular Catalytic Asymmetric Alkene Bromoesterification Reaction as Revealed by Kinetic Profiling
作者:D. Christopher Braddock、Ben M. J. Lancaster、Christopher J. Tighe、Andrew J. P. White
DOI:10.1021/acs.joc.3c00672
日期:2023.7.7
Kinetic profiling has shown that a (DHQD)2PHAL-catalyzed intermolecular asymmetric alkene bromoesterification reaction is inhibited by primary amides, imides, hydantoins, and secondary cyclic amides, which are byproducts of common stoichiometric bromenium ion sources. Two approaches to resolving the inhibition are presented, enabling the (DHQD)2PHAL loading to be dropped from 10 to 1 mol % while maintaining