1: 91 percent / acetic anhydride / 1.5 h / Heating 2: 91 percent / K2CO3 / methanol / 0.5 h / 25 °C 3: 61 percent / triphenylphosphine, diethyl azodicarboxylate / benzene / 20 h / Heating View Scheme

in acetic anhydride 1.5 h; Heating;