1.1: hydrogenchloride / water / carbon treatment 1.2: 1.5 h / 25 - 30 °C 2.1: triethylamine / methanol / 1.5 h / 10 - 20 °C 3.1: sodium tetrahydroborate; boron trifluoride diethyl etherate / tetrahydrofuran / 4 h / 0 - 50 °C 3.2: 0.17 h / 10 °C 4.1: hydrogenchloride / water; methanol / 0.75 h / 25 - 30 °C View Scheme

1.1: hydrogenchloride / water / carbon treatment 1.2: 1.5 h / 25 - 30 °C 2.1: triethylamine / methanol / 1.5 h / 10 - 20 °C 3.1: sodium tetrahydroborate; boron trifluoride diethyl etherate / tetrahydrofuran / 4 h / 0 - 50 °C 3.2: 0.17 h / 10 °C View Scheme

1: With hydrogenchloride in water Acidic aqueous solution; 2: With sodium hydroxide T=50°C; pH=<= 7; Alkaline aqueous solution;