Stannyl anions metal carbonyls

Fluoride ion first becomes coordinated with the silicon atom of tin reagent 33. Further coordination with the carbonyl oxygen atom of substrate 34 leads to an especially activated hypervalent silicon species 35.21 from which a stannyl anion is eliminated. I Ialogen-metal exchange between the tin anion and inyhc iodide 36 produces vinylic anion 37, which attacks in an intramolecular way the carbonyl group that has been activated through silicon coordination. Aqueous workup leads to alcohol 38. 

When Me3SiSnBu3 is treated with CsF, the fluoride anion should coordinate to the silyl group and not the stannyl group to produce a hypervalent silicate, and as a result, a stannyl anion would be generated.282 The stannyl anion reacts with vinyl iodide to produce a vinyl anion via a halogen-metal exchange and it reacts with the carbonyl group intramolecularly (Equation (113)). Aryl halides or allyl halides are also used in similar cyclizations.283,284... 

The lithiated oxathiolan dioxide (19) has been used as a carbonyl anion equivalent to give high yields of aldehydes from alkyl halides and acyloins from cyclic ketones.The /8-acyl anion equivalent (20 X = Li), which can be prepared from the stannylated diene (20 X = SnRs) by metal exchange, reacts with a variety of electrophiles (E ) to give dienes (20 X = E) in good to excellent yields.The thiophosphate (21) gives a,/3-unsaturated esters in 48—68% yield... 

Let s begin with the preparation of a 113, the precursor of 107. Known aldehyde 109 was treated with fm -crotyltributylstannane in the presence of a Lewis acid to provide 110. The relative stereochemistry between Cis and Ci9 was chelation controlled. The relative stereochemistry between C17 and C18 resulted from presumed addition of the stannane to the aldehyde via a chair-like transition state with Sn coordinated to the carbonyl oxygen. An interesting procedure was used to convert 110 to the homologous aldehyde, which cyclized to a mixture of anomeric hemiacetals 111. Dehydration of the mixture provided 112. Metallation of 112 using Schlosser s base, followed by stannylation of the resulting vinyl anion, provided 113. ... 

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