1: 75 percent / pyridine / 48 h / -20 °C 2: 90 percent / dibenzo-18-crown-6 / acetonitrile / a) room temp., 1 h; b) reflux, 18 h 3: tetrahydrofuran 4: 68 percent / 1 N HCl / Heating View Scheme

tributylphosphine in dichloromethane T=0°C;

1: pyridine / 5 h / 0 °C 2: 5.805 g / 1.1M ethanolic NaOEt / 1 h / Heating View Scheme

1: 98 percent / nBu3P / CH2Cl2 / 0 °C 2: 83 percent / Me3SiOOSiMe3 / benzene / 18 h / Heating View Scheme