thionyl chloride in dichloromethane T=25°C; 0.5 h; Yield given;

1: SOCl2 / CH2Cl2 / 0.5 h / 25 °C 2: 1.) sec-butyllithium / 1.) ether, 0 deg C, 4 h; 2.) ether, -78 deg C, 15 min then to r.t. View Scheme

1: SOCl2 / CH2Cl2 / 0.5 h / 25 °C 2: 1.) sec-butyllithium / 1.) ether, 0 deg C, 4 h; 2.) ether, -78 deg C, 15 min then to r.t. 3: 98 percent / diethyl ether / 0.25 h / 0 °C 4: 88 percent / 3M H2SO4 / tetrahydrofuran / 12 h / 25 °C View Scheme