1: 79 percent / MnO2 / acetone / 6 h 2: 87 percent / tetrahydrofuran; diethyl ether / 0.5 h / -78 °C 3: 86 percent / 6N HCl / H2O / 18 h / 100 °C View Scheme

hydrogenchloride in water T=100°C; 24 h;