1: 63 percent / DBU / benzene / 1 h / 25 °C 2: 57 percent / BF3 etherate / 72 h / 25 °C 3: 100 percent / DBU / benzene / 3 h / Heating View Scheme

1: aluminum amalgam, NH4Cl / methanol / 2 h / 25 °C 2: BF3 etherate / 72 h / 25 °C 3: 1.) NBS; 2.) DBU / 1.) CCl4, 2h, reflux; 2.) benzene, 3h, reflux View Scheme

1: aluminum amalgam, NH4Cl / methanol / 2 h / 25 °C 2: BF3 etherate, BHT stabilizer / 72 h / 25 °C View Scheme