1: 87.2 percent / pyridinium p-toluenesulphonate / methanol / 4 h / 55 °C 2: 76.08 percent / PBr3, pyridine / diethyl ether / 2 h / Heating 3: 47.8 percent / Li2CuCl4 / tetrahydrofuran / 3 h / -10 °C View Scheme

pyridinium p-toluenesulfonate in ethanol T=60°C; 8 h;

silica gel; pyridinium chlorochromate in dichloromethane 0.0333333 h; microwave irradiation;