1: With n-butyllithium in tetrahydrofuran T=-78°C; 1.5 h; 2: With boric acid trimethyl ester in tetrahydrofuran T=-10°C; 2 h; 3: With hydrogenchloride; water in tetrahydrofuran T=-10°C; 0.5 h;

1.1: 70 percent / KOH / ethanol / 1.5 h / 78 °C 2.1: n-butyllithium / tetrahydrofuran; hexane / 1 h / -90 °C 2.2: trimethylborate / tetrahydrofuran; hexane / 0.5 h / -70 °C 2.3: 25 percent / aq. ammonium chloride / tetrahydrofuran; hexane / 1 h / 20 °C View Scheme

4 A molecular sieve in tetrahydrofuran T=20°C; 2 h;