copper(I) bromide; lithium bromide in tetrahydrofuran soln. of Bu3SnLi is added to soln. of CuBr and LiBr at -78°C, stirring for 1 h, soln. of acetylene is added, stirring for 1 h at same temp., then for 1 h at 0°C; quenching with satd. aq. NH4Cl, extn. (hexane), drying (Na2SO4), condensing under reduced pressure;

titanium tetrachloride in dichloromethane T=-78°C; 2.5 h;