1: 74 percent / K2CO3 / H2O / 1.) room temperature, 1 h, 2.) reflux, 30 min 2: 76 percent / potassium tert-butoxide / dimethylformamide / 5 h / 100 °C 3: 73 percent / 48 percent HBr (aq.), acetic anhydride / 120 h / Heating 4: 92 percent / P2S5 / pyridine / 48 h / Heating 5: 70 percent / methanolic sodium methoxide / 24 h / 60 °C 6: 52 percent / 1M potassium tert-butoxide / dimethylformamide / 0.5 h / Ambient temperature View Scheme