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The carbomethoxy chemical shift as a criterion of stereochemistry in certain aryl cyclopropanecarboxylates

✍ Scribed by G.L. Krueger; F. Kaplan; M. Orchin; W.H. Faul

Publisher
Elsevier Science
Year
1965
Tongue
French
Weight
239 KB
Volume
6
Category
Article
ISSN
0040-4039

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✦ Synopsis

The reactions of styrenes and stilbenes with diazoacetic esters give mixtures of cis-and trans-2-aryl-and 2,j-diarylcyclopropanecarboxy-lates. Analogous mixtures are obtained from 2- (194) and 4-vinylpyridine.

Although in the past stereochemical configuration of these isomers has been established by various methods,(1J2J3J4J5J8) we now wish to report that assignments may be made by analysis of the nuclear magnetic resonance (n.m.r.) chemical shifts of the carbomethoxy protons. The carbomethoxy group gives a sharp intense peak. The chemical shift for a series of compounds of known stereochemistry has been measured; the data are summarized in Table I. On the basis of the relationship between chemical shift and stereochemistry it is possible to assign configurations to other structurally related compounds isolated either as separate stereoisomers or as a mixture of cis-and trans-isomers. -With respect to the aryl and diaryicyclopropnne derivatives of known stereochemistry, the assignment of a resonance peak to the carbcmethoxy group is unambiguous. The partially deuterated carbomethoxy

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