1: 99.5 percent / pyridine / acetonitrile / 1 h / 40 - 50 °C 2: 11 percent / 1,1-dichloromethyl methyl ether, ZnCl2 / 4 h / 80 °C 3: 94 percent / thiourea / methanol / 3 h / 50 °C View Scheme