Preparation and Electrophilic Substitution of 1‐Trimethylsilylpentadienyllithium

Pentadienyllithium (16) was regioselectively and efficiently transformed to 1‐trimethylsilyl‐2,4‐pentadiene (17) by reaction with chlorotrimethylsilane (Scheme 5). Deprotonation of 17 and subsequent electrophilic attack furnished the regioisomeric products 12 and/or 13 in good yields (Schemes 5 and 6). The utility of the reaction 18→12 for the convergent assembly of the 1‐silyl‐1,3‐butadiene unit with an olefinic dienophile is further illustrated by the smooth intramolecular Diels‐Alder reaction 19→20.