Parallel kinetic resolutions using active esters

Coulbeck, Eliot

Abstract

Obtaining enantiomerically pure compounds is of major importance in modern organic chemistry; the resolution of racemic compounds is a very useful and practical method of achieving this. Parallel kinetic resolutions are an interesting variation on the more classical resolution methods; this method has been recently introduced to the scientific community by Vedejs and there are currently very few examples of successful parallel kinetic resolutions in the literature.The aim of the project, outlined in this report, was to investigate the use of parallel kinetic resolution methodology to resolve racemic carboxylic acids and secondary alcohols. This aim was achieved and in total four distinct parallel kinetic resolution methods were developed; one for the resolution of carboxylic acids, one for the resolution of secondary alcohols, and two that can be used to resolve either carboxylic acids or secondary alcohols. The development process is described for each of these distinct resolutions and their relative scope and limitations are discussed. This report also details the possible reasons for the levels of selectivity found in these reactions, and discusses what effect the reaction conditions have on the level ofstereocontrol. Similarities between all four of the resolutions are described, and the possibility of a generic stereoselective pathway is discussed.This report however is not limited only to findings directly related to parallel kinetic resolutions; it also encompasses all findings from the above mentioned studies.  As such, it also describes an unusual observation; the fact that the sign of optical rotation for the common resolving agent 4-isopropyl oxazolidinone is solvent dependant. The discovery and further exploration of a method for synthesising a range of optical pure secondary alcohols from the commercial available (S)-enantiomer of 1- (2-bromo-phenyl)-ethanol is also described. An interesting method for the determination of enantiomeric excess of carboxylic acids is also discussed.

Citation

Coulbeck, E. Parallel kinetic resolutions using active esters. (Thesis). University of Hull. https://hull-repository.worktribe.com/output/4209265

• Thesis Type: Thesis
• Deposit Date: Aug 15, 2011
• Publicly Available Date: Feb 22, 2023
• Keywords: Physical sciences; Chemistry
• Public URL: https://hull-repository.worktribe.com/output/4209265
• Additional Information: Department of Physical Sciences, The University of Hull
• Award Date: Aug 1, 2009