Fluoride Ion-Promotedα-Ketol Rearrangement during Unmasking of Silyl-Protected Medium-Ring Dihydroxy Ketones
作者:Ryan E. Hartung、David G. Hilmey、Leo A. Paquette
DOI:10.1002/adsc.200404002
日期:2004.6
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
The reaction of g.-halo ketones (alpha-iodocycloalkanones, alpha-bromocycloalkanones, alpha-iodo-beta-alkoxy esters, and alpha-iodoacyclic-ketones) with irradiation under a high-pressure mercury lamp gave the corresponding alpha-hydroxyketones in good yields. For alpha-bromoketones, it was found that alpha-hydroxylation does not occur. However, alpha-bromoketones were convened into a-hydroxyketones in the presence of KI. In the case of alpha,alpha(1)-diiodo ketones, alpha,alpha(1)-dihydroxyketones, which up to now have scarcely been reported, were obtained. This reaction affords a new, clean and convenient synthetic method for alpha-hydroxy- and alpha,alpha(1)-dihydroxyketones. (C) 2005 Elsevier Ltd. All rights reserved.