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A novel stereoselective reaction cascade leading from $\alpha$-silylated allylic alcohols to aldol-type products


Fässler, Jürg; Enev, Valentin; Bienz, Stefan (1999). A novel stereoselective reaction cascade leading from $\alpha$-silylated allylic alcohols to aldol-type products. Helvetica Chimica Acta, 82(4):561-587.

Abstract

The treatment of a-silylated allylic alcohols with epoxidizing reagents afforded in a highly stereocontrolled fashion a-silylated aldols. The transformation is proposed to proceed either by a reaction cascade involving stereospecific epoxidation of the allylic-alcohol moiety followed by an acid-supported pinacol-type rearrangement, or by a sequence consisting of a p-face-selective electrophilic attack at the allylic silane moiety with hyperconjugative stabilization of the evolving carbocation, followed by rearrangement of the thus obtained pentacoordinated silanium ion (see Scheme 3). Depending on the reaction conditions, the p-face selectivity of the oxidation step is controlled by the stereogenic C-atom or the more remote Si-center of chirality.

Abstract

The treatment of a-silylated allylic alcohols with epoxidizing reagents afforded in a highly stereocontrolled fashion a-silylated aldols. The transformation is proposed to proceed either by a reaction cascade involving stereospecific epoxidation of the allylic-alcohol moiety followed by an acid-supported pinacol-type rearrangement, or by a sequence consisting of a p-face-selective electrophilic attack at the allylic silane moiety with hyperconjugative stabilization of the evolving carbocation, followed by rearrangement of the thus obtained pentacoordinated silanium ion (see Scheme 3). Depending on the reaction conditions, the p-face selectivity of the oxidation step is controlled by the stereogenic C-atom or the more remote Si-center of chirality.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Language:English
Date:1999
Deposited On:25 Aug 2017 13:16
Last Modified:25 Aug 2017 13:16
Publisher:Wiley-Blackwell Publishing, Inc.
ISSN:0018-019X
Publisher DOI:https://doi.org/10.1002/(SICI)1522-2675(19990407)82:4<561::AID-HLCA561>3.0.CO;2-U

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