1: 71 percent / acetic acid / 0.5 h / 100 °C 2: 50 percent / H2O / 1) reflux, 2 h, 2) 12 h room temperature 3: 53 percent / tributylphosphine / toluene / 1 h / 125 - 130 °C 4: 25 percent / toluene / 3 h / Heating View Scheme