Metal catalysis in organic reactions. Part 13. The reaction of 3-en-1-ynes with trialkylalanes: influence of transition-metal complexes

Abstract

The reaction between trialkylalanes and 3-alkyl-, 4-alkyl-, or 3,4-dialkyl-but-3-en-1-ynes (1) leads to products which correspond to metallation, reduction, and carbalumination processes. The extent of such reactions, and the regio- and stereo-selectivity of the carbalumination, are dependent on the enyne used. A mechanism is proposed involving tautomeric equilibria among several α-unsaturated organoaluminum intermediates to explain the formation of the carbalumination products.

In the presence of catalytic amounts of nickel and manganese complexes, 3-en-1-ynes (1), by reacting with triisobutylaluminium, are dimerized selectively in a ‘head-to-tail’ fashion to conjugated tetraenes having different structures in relation to the different nature of the transition-metal complex. The preparative aspect of these induced reactions is discussed, and, in the light of previous reports, some mechanistic considerations are presented.