Organoaluminium compounds. VII. The reactions of organoaluminium compounds with phenylacetylene

Abstract

The reactions of trimethyl-, triethyl-, tripropyl-, tri-isobutyl-, and triphenylaluminium with phenylacetylene in the presence and absence of benzene or toluene have been studied. In every case phenylethynylaluminium compounds are formed. Dimethyl(phenylethynyl)aluminium and diphenyl(phenylethynyl)aluminium are crystalline solids. The former compound disproportionates partially in ethereal solution. Side reactions competing with the formation of phenylethynylaluminium compounds are also observed. Triethylaluminium and tripropylaluminium add to phenylacetylene to give PhC(AlR₂)=CHR (R = Et, Pr), but these alkenylaluminium compounds metallate further phenylacetylene and are so transformed to alkenes. A similar process occurs in the reaction with triphenylaluminium, but in this case both possible products of cis addition are observed. Tri-isobutylaluminium yields phenylethenyl compounds by reduction of the triple bond in the principal side reaction.