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

Multi-step reaction with 5 steps 1: 73 percent / CBr4, n-Bu3P / diethyl ether / 0.25 h / 0 °C2: 53 percent / Na2S*9H2O / ethanol; H2O / 25 °C3: 79 percent / m-chloroperbenzoic acid / CH2Cl2 / 0.5 h / -30 °C4: pyridine, SO2Cl2 / CH2Cl2 / 0.67 h / -78 °C5: m-chloroperbenzoic acid / CH2Cl2 / 16 h / Ambient temperature  

Multi-step reaction with 3 steps 1: 79 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  

Multi-step reaction with 6 steps 1: pyridinium p-toluenesulfonate / methanol / 18 h2: 73 percent / CBr4, n-Bu3P / diethyl ether / 0.25 h / 0 °C3: 53 percent / Na2S*9H2O / ethanol; H2O / 25 °C4: 79 percent / m-chloroperbenzoic acid / CH2Cl2 / 0.5 h / -30 °C5: pyridine, SO2Cl2 / CH2Cl2 / 0.67 h / -78 °C6: m-chloroperbenzoic acid / CH2Cl2 / 16 h / Ambient temperature