1: triethylamine / dichloromethane / -15 °C 2: phosphorus pentachloride / tetrahydrofuran / -85 °C 3: perchloric acid; 1,3-dibromo-5,5-dimethyl-hydantoin / water; N,N-dimethyl-formamide / 1 h / 20 °C 4: sodium hydroxide / dichloromethane; methanol / 0 - 5 °C View Scheme

1: perchloric acid; 1,3-dibromo-5,5-dimethyl-hydantoin / water; N,N-dimethyl-formamide / 1 h / 20 °C 2: sodium hydroxide / dichloromethane; methanol / 0 - 5 °C View Scheme

methanolic potassium hydroxide

potassium acetate in isobutyramide T=20°C; 2 h;

1: 69 percent / 4-DMAP, CH3SO2Cl / CH2Cl2 / 4 h / Heating 2: 3.44 g / Et3N, 4-DMAP / CH2Cl2 / 6 h / Ambient temperature 3: 83 percent / conc. HCl / acetic acid / 3 h / Ambient temperature View Scheme

1: 69 percent / 4-DMAP, CH3SO2Cl / CH2Cl2 / 4 h / Heating 2: 83 percent / conc. HCl / acetic acid / 3 h / Ambient temperature View Scheme