1: 14.43 g / 1-hydroxybenzotriazole; 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride; ethyldiisopropylamine / CH2Cl2 / 1.5 h / 20 °C 2: 25 percent / propan-2-ol / 24 h / Heating 3: HCl / tetrahydrofuran; H2O / 5 h / 50 °C 4: 95 percent / 1-hydroxybenzotriazole; 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride; ethyldiisopropylamine / CH2Cl2 View Scheme

hydrogenchloride in tetrahydrofuran; water T=50°C; 3 h;