US EPA

7439976 

Journal Article 

STEREOSELECTIVE EPOXIDATION OF ALLYLIC CARBAMATES WITH M-CHLOROPERBENZOIC ACID - THE ROLE OF COOPERATIVE COORDINATION 

Ney, JF; Sasner, JJ; Ikawa, M; Jenmalm, A; Berts, W; Luthman, K; Csoregh, I; Hacksell, U 

1995 

Yes 

Journal of Organic Chemistry
ISSN: 0022-3263
EISSN: 1520-6904 

60 

4 

1026-1032 

English 

10.1021/jo00109a039 

WOS:A1995QJ61900039 

https://pubs.acs.org/doi/abs/10.1021/jo00109a039
Exit
 

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.