Reaction of copper(I) acetylides with halogeno-acetylenes

The reaction between the copper(I) derivatives of propyne, ethynylbenzene, 5-ethynyl-2,2′-bithienyl, 3-(tetra-hydropyranyloxy)prop-1-yne, 3,3-diethoxyprop-1-yne, and but-1-yn-3-ol with 3-bromoprop-2-yn-1-ol in pyridine at 35–50° gave a simple synthesis of the corresponding diynols hexa-2,4-diyn-1-ol (III), 5-phenylpenta-2,4-diyn-1-ol (V), 6-(tetrahydropyranyloxy)hexa-2,4-diyn-1-ol, and 6,6-diethoxyhexa-2,4-diyn-1-ol, hepta-2,4-diyn-1,6-diol, and 5-(5-hyoroxypenta-1,3-diynyl)-2,2′-bithienyl, respectively. Oxidation of (III) and (V) with nickel peroxide in benzene followed by deformylation led to the terminal acetylenes penta-1,3-diyne (XIV) and 4-phenylbuta-1,3-diyne, and subsequent coupling of the corresponding copper(I) salt of, e.g., (XIV) with the 3-bromopropynol produced a new homologation sequence for polyacetylenes exemplified by the synthesis of octa-2,4,6-triyn-1-ol.