Kinetic resolution of alpha-acetoxy carboxylic acids with homochiral SuperQuats

Bew, Sean P., Davies, Stephen G. and Fukuzawa, Shin‐Ichi (2000) Kinetic resolution of alpha-acetoxy carboxylic acids with homochiral SuperQuats. Chirality, 12 (5-6). pp. 483-487. ISSN 0899-0042

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Abstract

Preliminary investigations focused on the kinetic resolution of (+)-alpha-acetoxy mandelic carboxylic acid chloride with isopropyl SuperQuat and isopropyl Evans' homochiral auxiliaries. The addition of 2 equiv. of the acid chloride to the lithium salts of the auxiliaries (SuperQuat and Evans') at -100 degrees C in the THF afforded the corresponding N-acyl auxiliaries in high chemical yields (95% and 89%) and d.e.'s of 66% and 40%, respectively. Using the same mandelic acid chloride but incorporating SuperQuat aux iliaries derived from (S)-phenylglycine and (S)-phenylalanine yielded the corresponding N-acyl SuperQuats in 86% and 90% and d.e.'s of 66% and 30%, respectively. Substituting the phenyl group within the cr-acetoxy mandelic acid chloride for a n-butyl, tert-butyl and cyclohexyl group changed the d.e. significantly when kinetically resolved with isopropyl SuperQuat. The yields were all similar, i.e., similar to 90% but the d.e.'s varied considerably, with values of 20%, 50%, and 82%, respectively. Attempted kinetic resolution of alpha-methoxy-phenylacetyl chloride using the lithium salt of isopropyl SuperQuat revealed a diasteroselectivity of 45%, significantly lower than that obtained with the corresponding alpha-acetoxy carboxylic acid chlorides. (C) 2000 Wiley-Liss, Inc.

Item Type: Article
Faculty \ School: Faculty of Science > School of Chemistry
Depositing User: Rachel Smith
Date Deposited: 20 Apr 2011 09:04
Last Modified: 14 May 2020 23:54
URI: https://ueaeprints.uea.ac.uk/id/eprint/29667
DOI: 10.1002/(SICI)1520-636X(2000)12:5/6<483::AID-CHIR33>3.0.CO;2-D

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