1: 82 percent / tetraethylammonium bromide; CuBr; triethylamine / 100 °C / 167200 Torr 2: 97 percent / polyphosphoric acid / 0.5 h / 80 °C 3: 100 percent / H2SO4 / H2O View Scheme

tetraethylammonium bromide; triethylamine; copper(I) bromide T=100°C; P=167200 Torr;