1: 90 percent / thionyl chloride, pyridine / diethyl ether / 2 h / 0 °C 2: 5percent NaOH / ethanol / 2 h / Heating 3: SOCl2 / 4 h 4: diethyl ether View Scheme

pyridine; thionyl chloride in diethyl ether T=0°C; 2 h;