89822-47-9

Spiro-γ-lactone Synthesis via Reactions with Carbonyl Compounds.
Although lithiated allyltrimethylsilane adds to simple ketones with good regioselectivity (eq 1),its addition to 17-ketosteroids produces a mixture of α and γ adducts. Transmetalation of allyltrimethylsilyllithium with ZnCl2 leads to a reagent (allyltrimethylsilylzinc chloride) which adds with complete regioselectivity. to this type of hindered ketone.

deprotonation of allyltrimethylsilane with n-butyllithium in THF at ?78°C or s-butyllithium in THF/TMEDA, followed by the addition of zinc chloride. The reagent is prepared in situ and used directly.