PPA T=145 - 155°C; 3 h;

1: 90 percent / bromine / H2O / 4 h / Ambient temperature 2: 70 percent / sodium ethanolate / ethanol / 2 h / Heating 3: 55 percent / polyphosphoric acid / 3 h / 145 - 155 °C View Scheme

1: 70 percent / sodium ethanolate / ethanol / 2 h / Heating 2: 55 percent / polyphosphoric acid / 3 h / 145 - 155 °C View Scheme

1: 94 percent / sodium hydride / tetrahydrofuran / Ambient temperature; overnight 2: 90 percent / bromine / H2O / 4 h / Ambient temperature 3: 70 percent / sodium ethanolate / ethanol / 2 h / Heating 4: 55 percent / polyphosphoric acid / 3 h / 145 - 155 °C View Scheme