hydrogenchloride in ethyl acetate T=60°C; Ring cleavage; 0.25 h;

1,3-dibromo-5,5-dimethyl-hydantoin in dichloromethane T=0 - 5°C; 4 h;

acetic anhydride; sodium nitrite in dichloromethane T=0 - 5°C; 6.8 h;

hydrazine hydrate in ethanol T=30°C;

1.1: SiO2 / 0.08 h / 20 °C / microwave irradiation 1.2: 90 percent / aq. sodium hydroxide / ethanol / 0.17 h / Heating 2.1: 93 percent / silica chloride; wet SiO2; sodium nitrite / CH2Cl2 / 2 h / 0 - 5 °C 3.1: 86 percent / 1,3-dibromo-5,5-dimethylhydantoin / CH2Cl2 / 4 h / 0 - 5 °C View Scheme

1.1: tetra(n-butyl)ammonium hydroxide / methanol 1.2: 45 °C 2.1: sodium nitrite / water / 0.33 h / 0 °C 3.1: acetic anhydride / 5 h / 100 °C View Scheme