Enantioselective Synthesis of Alkyl-Branched Alkanes. Synthesis of the Stereoisomers of 7,11-Dimethylheptadecane and 7-Methylheptadecane, Components of the Pheromone of Lambdina Species

The stereoisomers of 7,11-dimethylheptadecane and 7-methylheptadecane have been synthesized. The key step used has been the intramolecular hydride transfer from a secondary γ-benzyloxy group with defined absolute stereochemistry to a cation generated by Lewis acid treatment of the suitable tertiary Co₂(CO)₆-complexed propargylic alcohol. The application of this method provided stereochemically defined α-alkyl-γ-hydroxy-acetylenes that after hydrogenation and further reductive elimination of the hydroxyl group yielded sec-alkyl hydrocarbons.