Regioselective Alkylation of the Polyfunctional Nucleophile 1‐(Methylthio)‐3‐triethylsilyloxypentadienyllithium

Abstract γ‐Selective sulfenylation of the triethysilyloxypentadienyllithium 1 gave the versatile alkylthiodene 4 which on successive deprotonation and alkylation furnished with high regioselectivity the γ‐products 6. Fluoride‐promoted silylether cleavage 6 → 7 may be followed by intramolecular [4 + 2]‐addition 7c → 8 and sulfoxide elimination 8 → 9. The conversions 7b → 12 and 7a → 17 demonstrate the feasibility of 5 to serve as an equivalent of the hypothetical β‐deprotonated divinylketone 13 whose two enone units may be unmasked separately.