Intramolecular alkoxycarbonylation of tungsten-propargyl compounds proceeds with excellent diastereoselectivities to form η 3 -δ-and --lactones but for γ-lactones. With OSi(t-Bu)Me 2 substituted for an R-hydroxy group , η 3 -γ-lactones are stereoselectively formed with syn stereoselection . An optically active tungsten η 3 -γ-lactone is prepared from D-(+)-xylose to illustrate the stereochemical effect of OSi(t-Bu)Me 2 . All these η 3 -γ-, -δ-, and --lactones are converted to allyl anions that react in situ with aldehydes and ketones to produce various β-(hydroxylalkyl)-R-methylene-γ-lactones with good diastereoselectivity. This reaction is also applied to the synthesis of chiral R-methylene butyrolactones. Organic carbonyls add to the π-allyl groups of η 3 -γ-and -δ-lactones opposite the tungsten fragment, whereas additions occur from the metal side for η 3 --lactones. The stereochemical courses of these reactions are discussed in detail. These two tungsten-promoted reactions efficiently effect stereoselective transformation of chloroalkynols to complex R-methylene-γ-lactones, which are useful materials for syntheses of trisubstituted 1,3-, 1,4-, and 1-5-diols.

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