Stannyl-Active Metal Reagents

Although stannyl-active metal reagents are prepared containing Zn -, Cd, and Hg , only those containing Na, Li, and Mg are used to prepare Sn—M bonds. 

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. 

---