hydrogenchloride; aluminium trichloride in dichloromethane AlCl3 catalyst added to a soln. of BrCN in CH2Cl2 under N2; obtained soln. added dropwise to a soln. of 1-triethylstannylbut-3-ene-1-yne at 0 ° C; after stirring for 30 min mixture poured into ice cold HCl soln.; organic layer washed with water and dried over MgSO4; after removal of solvent residue distilled to yield 1-cyanobut-3-ene-1-yne; IR, H-NMR;