1: 88 percent / Polyphosphorsaeure 2: 90 percent / Ag2O / dimethylformamide 3: 75 percent / 46percent aq. HBr / 2 h / Heating 4: 1.) 0.1N KOH, 2.) KI, K2CO3 / 1.) ethanol, 60 deg C, 30 min, 2.) DMF View Scheme