hydrogen bromide in sulfolane T=15°C; 3 h;

1: 92 percent / dry hydrogen bromide / tetrahydrothiophene 1,1-dioxide / 3 h / 15 °C 2: dimethylformamide; H2O / 0.33 h / Ambient temperature 3: 93.2 percent / dry hydrogen bromide / tetrahydrothiophene 1,1-dioxide / 2.75 h / 15 °C 4: acetone; H2O / 1 h / Heating 5: 90 percent / conc. sulfuric acid / methanol; H2O / 23 h / Heating 6: 75.1 percent / polyphosphoric acid, water / 1.33 h / 90 °C View Scheme