Chiral Acylsilanes in Organic Synthesis. Part 3 . Silicon‐directed stereoselective preparation and Ireland ester‐enolate rearrangement of O ‐acyl‐substituted α‐silylated allyl alcohols

Stereocontrolled addition of alk‐1‐enylmetal reagents to the chiral (alkoxymethyl)‐substituted acylsilanes (±)‐ 6 gave rise to α‐silylated allyl alcohols, which were converted to the corresponding acetates or propionates 11–16 ( Scheme 2 ). Deprotonation and silylation with Me 3 SiCl afforded – in an Ireland ester‐enolate‐accelerated Claisen rearrangement – stereoselectively αδ‐silylated γδ‐unsaturated carboxylic acids 18–24 ( Scheme 4 ). The Me 3 Si groups in α‐position to the COOH group of these compounds were removed chemoselectively in presence of the chiral silyl group in δ‐position by treatment with Bu 4 NF · 3 H 2 O or Et 3 N · 3 HF (→ 27–32 ; Scheme 5 ). The reaction sequence allows a novel stereocontrolled access to chiral C‐frameworks possessing a vinylsilane moiety with its full reaction potential.