Fluoride Ion-Promoted α-Ketol Rearrangement during Unmasking of Silyl-Protected Medium-Ring Dihydroxy Ketones
✍ Scribed by Ryan E. Hartung; David G. Hilmey; Leo A. Paquette
- Publisher
- John Wiley and Sons
- Year
- 2004
- Tongue
- English
- Weight
- 165 KB
- Volume
- 346
- Category
- Article
- ISSN
- 1615-4150
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✦ Synopsis
Abstract
A new strategy for implementing α‐ketol rearrangements under mild conditions is presented. The reactants are mono‐ and disilylated stereoisomers of α,α′‐ and α,β‐dihydroxycycloheptanones and ‐cyclooctanones. Compounds of this class experience ready deprotection upon treatment with tetrabutylammonium fluoride. In certain examples, this process is accompanied by structural isomerization. Since the product diols are stable to the reaction conditions, these chemical changes have been attributed to kinetically controlled events following transient alkoxide generation resulting from cleavage of the OSi bond proximal to the carbonyl group. The experimental findings are evaluated against a backdrop of calculated (MM3) steric energies of the silicon‐free products and their response to equilibration under strongly basic conditions.