n-butyllithium in tetrahydrofuran; hexane T=-78°C; 0.5 h;

1: 80 percent / n-butyllithium / tetrahydrofuran; hexane / 0.5 h / -78 °C 2: n-buthyllithium / 1.) THF and HMPA, hexane, 0 deg C, 30 min; 2.) HMPA, 25 deg C, 20 h; 3: 95 percent / p-toluenesulphonic acid / methanol; H2O / 3 h / 60 °C View Scheme