1: 74 percent / pyridine / 1.) 2.5 h, 20 deg C; 2.) 6 h, 60 deg C 2: 53 percent / (CH3)2CuLi / diethyl ether / 5.5 h / -70 °C 3: 100 percent / p-toluenesulfonic acid / methanol / 3 h / 55 °C View Scheme

1: 74 percent / pyridine / 1.) 2.5 h, 20 deg C; 2.) 6 h, 60 deg C 2: 53 percent / (CH3)2CuLi / diethyl ether / 5.5 h / -70 °C 3: 100 percent / p-toluenesulfonic acid / methanol / 3 h / 55 °C 4: 95 percent / AgNO3 (1.2 equiv.) / acetone; H2O / 24 h / 20 °C / exclusion of light View Scheme