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Stereochemical observations on the Wittig reaction of oxido phosphonium ylides with aldehydes

✍ Scribed by Bruce E. Maryanoff; Allen B. Reitz; Barbara A. Duhl-Emswiler

Publisher: Elsevier Science
Year: 1983
Tongue: French
Weight: 292 KB
Volume: 24
Category: Article
ISSN: 0040-4039
DOI: 10.1016/s0040-4039(00)81959-0

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✦ Synopsis

The reaction of aldehydes with oxido ylides shows a dramatic dependence of alkene stereochemistry on the distance between oxygen and phosphorus atoms; ylides with proximal 0 and P atoms favor production of g alkenes. The high r stereoselectivity with r-oxido ylides is not mainly attributable to intramolecular proton-exchange in a Wittig intermediate. The stereochemistry of alkene formation in the Wittig reaction has attracted widespread interest for many years. 192 Although non-stabilized phosphonium ylides generally react with aldehydes to afford largely 1. alkenes,' there are some special exceptions, such as s-oxido3 and r-oxido4 ylides, which exhibit unexpectedly enhanced E stereoselectivity.

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