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General model of assignment of the relative stereochemistry in the Nicholas reaction products resulting from chiral dicobalthexacarbonyl-1-alkoxy-propargylium cations

✍ Scribed by Angel M. Montaña; Montserrat Cano

Publisher: John Wiley and Sons
Year: 2002
Tongue: English
Weight: 217 KB
Volume: 40
Category: Article
ISSN: 0749-1581
DOI: 10.1002/mrc.1012

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✦ Synopsis

Abstract

The Nicholas reaction of chiral 1‐alkoxy‐dicobalthexacarbonyl‐propargylium cations with linear and/or cyclic silyl enol ethers resulted in the formation of two pairs of diastereoisomers (syn‐1, syn‐2 and anti‐1, anti‐2), depending on the relative stereochemistry of the two new stereocenters formed in the reaction products. Here, we present a model to establish the relative stereochemistry of those stereocenters on the basis of a correlation of their ^1^H and ^13^C NMR spectra, together with their conformational analysis and a study of the stereoelectronic interactions conditioning the chemical shifts and coupling constants. The importance of this method is based on its applicability to the assignment of the relative stereochemistry of non‐separable components of a diastereomeric mixture or, when diastereomers are non‐crystallizable oily products, not suitable for X‐ray diffraction analysis. Copyright © 2002 John Wiley & Sons, Ltd.

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