On the reactivity of organometallic compounds towards functional substrates : IV. The reaction of aliphatic 1-alkynes with triisobutyl-aluminum: Dependence on the structure of the acetylenic substrate

The reaction between triisobutylaluminum and aliphatic 1-alkynes having alkyl groups of different structure on the 3-carbon atom has been investigated. At room temperature and in the absence of solvents, products which correspond to metallation, reduction and carbalumination processes, are isolated after hydrolysis. The extent of such reactions, and in particular the regiospecificity of the carbalumination is dependent on the experimental conditions adopted and on steric factors associated with the structure of the 1-alkyne used. On the basis of these results and the complete stereospecificity of the reaction when (+)(S-3,4-dimethyl-1-pentyne is used, possible mechanisms are discussed.