potassium tert-butylate in tetrahydrofuran T=-78°C; 3 h;

Multi-step reaction with 7 steps 1: 1.) n-BuLi, 2.) HMPA / 1.) THF, hexane, -78 deg C, 10 min, 2.) THF, hexane, a) from -78 deg C to RT, 2 h, b) RT, 16 h2: pyridinium p-toluenesulfonate / methanol / 18 h3: 92 percent / CBr4, n-Bu3P / diethyl ether / 0.25 h / 0 °C4: 31 percent / Na2S*9H2O / ethanol; H2O / 25 °C5: 68 percent / m-chloroperbenzoic acid / CH2Cl2 / 0.5 h / -30 °C6: pyridine, SO2Cl2 / CH2Cl2 / 0.67 h / -78 °C7: m-chloroperbenzoic acid / CH2Cl2 / 16 h / Ambient temperature  

Multi-step reaction with 4 steps 1: 31 percent / Na2S*9H2O / ethanol; H2O / 25 °C2: 68 percent / m-chloroperbenzoic acid / CH2Cl2 / 0.5 h / -30 °C3: pyridine, SO2Cl2 / CH2Cl2 / 0.67 h / -78 °C4: m-chloroperbenzoic acid / CH2Cl2 / 16 h / Ambient temperature  

Multi-step reaction with 3 steps 1: 68 percent / m-chloroperbenzoic acid / CH2Cl2 / 0.5 h / -30 °C2: pyridine, SO2Cl2 / CH2Cl2 / 0.67 h / -78 °C3: m-chloroperbenzoic acid / CH2Cl2 / 16 h / Ambient temperature