1: conc. H2SO4 / 3 h / 80 °C 2: 85 percent / acetone / 72 h / 20 °C 3: 63 percent / aq. HCl / 336 h / 5 °C 4: aq. HCl / 0.17 h / Heating View Scheme

in toluene T=20°C; Ring cleavage; elimination, addition; 7 h;