1: triethoxy (hex-1-ynyl)silane With 18-crown-6 ether; potassium ethanolate in tetrahydrofuran 1 h; 2: 3,3-dimethyl-butan-2-one in tetrahydrofuran T=0°C;

n-butyllithium in tetrahydrofuran T=-78°C;

1.1: magnesium bromide / diethyl ether / 2 h / Heating 1.2: 70.4 mmol / diethyl ether / 12 h / Heating 2.1: KOEt; 18-crown-6 / tetrahydrofuran / 1 h 2.2: 73 percent / tetrahydrofuran / 0 °C View Scheme