1: n-bromopentane With magnesium; ethylene dibromide in tetrahydrofuran 2: With copper(I) bromide; lithium bromide in tetrahydrofuran T=0°C; 0.333333 h; 3: methanesulfonic acid oct-2-ynyl ester in tetrahydrofuran T=-78 - 20°C;

1.1: triethylamine / CH2Cl2 / 3.5 h / -78 - -10 °C 2.1: magnesium; 1,2-dibromoethane / tetrahydrofuran 2.2: copper(I) bromide; lithium bromide / tetrahydrofuran / 0.33 h / 0 °C 2.3: 2.54 g / tetrahydrofuran / -78 - 20 °C View Scheme