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HERO ID
7439976
Reference Type
Journal Article
Title
STEREOSELECTIVE EPOXIDATION OF ALLYLIC CARBAMATES WITH M-CHLOROPERBENZOIC ACID - THE ROLE OF COOPERATIVE COORDINATION
Author(s)
Ney, JF; Sasner, JJ; Ikawa, M; Jenmalm, A; Berts, W; Luthman, K; Csoregh, I; Hacksell, U
Year
1995
Is Peer Reviewed?
Yes
Journal
Journal of Organic Chemistry
ISSN:
0022-3263
EISSN:
1520-6904
Volume
60
Issue
4
Page Numbers
1026-1032
Language
English
DOI
10.1021/jo00109a039
Web of Science Id
WOS:A1995QJ61900039
URL
https://pubs.acs.org/doi/abs/10.1021/jo00109a039
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Abstract
Stereoselective epoxidations of a series of allylic carbamate methyl esters la-d, homoallylic alcohols le-h, and acetates li-1 have been performed using m-chloroperbenzoic acid (m-CPBA) as epoxidizing agent. Throughout, the formation of the threo epoxides was favored. This selectivity is probably due to a directing effect of the carbamate group which forms a hydrogen bond to the peracid. However, the threo/erythro isomeric ratio is also dependent on steric interactions and on the possibility of cooperative coordination of the peracid to other suitably positioned functionalities such as allylic methyl ester, homoallylic alcohol, and acetate groups. The results of the present study indicate that the methyl ester is a weaker directing group than the carbamate. However, the directing effect of the methyl ester is stronger than that of the homoallylic alcohol and acetate groups. A thermodynamic study of the epoxidation of two epimeric carbamate esters giving considerably different isomeric product ratios (9:1 compared to 2:1) indicates that the order in the transition state structure influences the isomeric ratios. © 1995, American Chemical Society. All rights reserved.
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