Metalation Reactions XII. The Alkylation of Pentenynyl‐Lithium Derivatives

Selective monometalation of 1, 4‐enynes was performed with methyl‐lithium in ether. These monolithio compounds were alkylated with alkyl halides at the central 3‐position only to give unconjugated enynes. Dialkylation of the dilithio derivatives occurred also at the same position. However, protonation of these organometallics gave a mixture of products and trimethylsilyl chloride attacked the lithium derivative preponderantly at the 5‐position.