Palladium catalysed oligomerization of 1-alkynes

The oligomerization of 1-pentyne using palladium acetyl acetonate catalyst with various solvents and ligands was investigated. An equimolar mixture of HOAc and Et N proved to be a superior solvent. The major product observed in most cases was the dimer, 6-methylene-nona-yne, although both cis and trans-dect-ene-6-yne were observed in most cases. Trimers were formed when phosphines were replaced with bldentate amines or phosphite ligands. A one to one mixture of PPh and (CH ) P gave the highest yield of oligomers with 6-methylene-nona-4-yne as the major product. No aromatics were formed with any of the reaction systems studied. The general mechanism proposed, by Meriwether and elaborated by Maitlis is in agreement with these results