Stannyl sulfonates

Methylenation of sulfones.1 This reagent reacts rapidly with the anion (LDA) of even moderately hindered sulfones to form (3-stannyl sulfones, which undergo desulfonylstannylation on treatment with Bu4NF to form alkenes. 

Fluoride also has a high affinity for tin and the analogous P-stannyl sulfone elimination is an efficient and fast reaction. The requisite P-stannyl sulfones are prepared by alkylation of the sulfone anions as in the silicon case however, the iodoalkylstannanes react faster [relative rate order MesSiCH (1),... 

Sulfonation of the aromatic ring of l, 2, 2 -trifluorostyrene below 0 C does not give satisfactory yields with chlorosulfonic acid or a sulfur trioxide-dioxane complex Tar forms on heating In contrast, under similar conditions ipso substitution IS facile at the position of a trialkylsilyl or -stannyl group Thus, 4-trimethyl-silyl-T 2, 2 D-trifluorostyrene affords the corresponding trimethylsilyl sulfonate [20] (equation 9)... 

Direct C-l deprotonation-lithiation occurs on treatment of the O-benzyl-ated or -silylated glycals with strong bases such as tert-butyllithium at low temperatures, and the vinyllithiums (such as 120) can subsequently be stannylated with tributylstannyl chloride.135 Otherwise, compound 121 can be produced from S-phenyl tetra-C-benzyl-l-thio-/f-D-glucopyranoside via sulfone 122 by treatment with tributylstannane and a radical initiator.132... 

The synthesis of electron-deficient diene 285 was achieved by the Stille coupling of P-trifluoromethanesulfonyl-a,P-unsaturated sulfone (284) with a 3-stannyl-a,P-unsaturated ester (283) (Scheme 74).148 Similarly, the preparation of a diverse range of enantiomerically pure 1- and 2-sulfinyl dienes has been achieved via Stille coupling of halovinyl sulfoxides and vinyl stannanes.149,150 Enantiomerically pure 1- and 2-sulfinyl dienes have been used extensively in asymmetric Diels-Alder reactions.111... 

Wnuk, S.F., and Robins, M.J., Stannyl radical-mediated cleavage of Jt-deficient heterocyclic sulfones. Synthesis of a-fluoro esters and first homonucleoside a-fluoromethylene phosphonate, J. Am. Chem. Soc., 118, 2519, 1996. 

Ueno has devised a general synthetic method for the preparation of allyltin from allyl sulfones via an Sh2 process [131]. The key steps for these transformations which consist of addition of stannyl radical to appropriate allyl sulfone and the -elimination of sulfonyl radical are depicted in Scheme 17 (see Scheme 11 for detailed propagation steps). Since both steps are reversible, the equilibrium can be driven to the left or right depending on the experimental conditions [132]. However, the extension of this methodology to the synthesis of homoal-lylic alcohols or to 2-substituted-1,3-butadiene have been achieved starting from the appropriate sulfone (Scheme 17) [133]. This approach has also been applied to the preparation of 2-functionalized allyl tris(trimethylsilyl)silanes (cf. equation (38)) [83]. 

Vinyl sulfones can be converted into vinyl stannanes by an analogous Sh2 reaction of allyl sulfones (Scheme 19). Again, the displacement of sulfonyl radical by stannyl radical is a reversible reaction which can be driven in either direction... 

The synthesis of tributylstannylglycals by treating glycals with /-butyllithium then tributyltin chloride is successful when the 0-3 is unsubstituted otherwise furans are formed. However, Scheme 1 shows how glycal phenyl sulfones with 0-3 substituents can be converted to the C-stannyl analogues, useful for preparing 1-C-arylglycais. ... 

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