Tungsten-Promoted Intramolecular Alkoxycarbonylation for Synthesis of Complex Oxygenated Molecules
Resource
Journal of the American Chemical Society 118 (39): 9279-9287
Journal
Journal of the American Chemical Society
Journal Volume
118
Journal Issue
39
Pages
9279-9287
Date Issued
1996
Date
1996
Author(s)
Chen, Chi-Chung
Fan, Jang-Shyang
Shieh, Su-Ju
Lee, Gene-Hsian
Wang, Sue-Lang
Liu, Rai-Shung
Abstract
Intramolecular alkoxycarbonylation of tungsten-propargyl compounds proceeds with excellent diastereoselectivities to form η3-δ- and -ε-lactones but for γ-lactones. With OSi(t-Bu)Me2 substituted for an α-hydroxy group η3-γ-lactones are stereoselectively formed with syn stereoselection. An optically active tungsten η3-γ-lactone is prepared from D-(+)-xylose to illustrate the stereochemical effect of OSi(t-Bu)Me2. All these η3-γ-, -δ-, and -ε-lactones are converted to allyl anions that react in situ with aldehydes and ketones to produce various β-(hydroxylalkyl)-α-methylene-γ-lactones with good diastereoselectivity. This reaction is also applied to the synthesis of chiral α-methylene butyrolactones. Organic carbonyls add to the π-allyl groups of η3-γ- and -δ-lactones opposite the tungsten fragment, whereas additions occur from the metal side for η3-ε-lactones. The stereochemical courses of these reactions are discussed in detail. These two tungsten-promoted reactions efficiently effect stereoselective transformation of chloroalkynols to complex α-methylene-γ-lactones, which are useful materials for syntheses of trisubstituted 1,3-, 1,4-, and 1-5-diols.
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Type
journal article
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