1: methyl-magnesium chloride With copper(I) bromide; lithium bromide in tetrahydrofuran T=0°C; 0.5 h; 2: methanesulfonic acid 3-(tert-butyl-diphenyl-silanyl)-prop-2-ynyl ester in tetrahydrofuran T=20°C; 2 h; Further stages.;

1.1: MeMgCl / tetrahydrofuran / 0.67 h / 0 °C 1.2: tetrahydrofuran / -78 - 20 °C 2.1: CuBr; LiBr / tetrahydrofuran / 0.5 h / 0 °C 2.2: 96 percent / tetrahydrofuran / 2 h / 20 °C View Scheme

1.1: n-BuLi; p-toluenesulfonic acid monohydrate / tetrahydrofuran; hexane / 0.33 h / -78 - 0 °C 1.2: tetrahydrofuran; hexane / 0 - 20 °C 1.3: 74 percent / p-toluenesulfonic acid / methanol / 3 h 2.1: MeMgCl / tetrahydrofuran / 0.67 h / 0 °C 2.2: tetrahydrofuran / -78 - 20 °C 3.1: CuBr; LiBr / tetrahydrofuran / 0.5 h / 0 °C 3.2: 96 percent / tetrahydrofuran / 2 h / 20 °C View Scheme