1: lithium hydroxide hydrate / ethanol; water / 1 h / |Reflux 2: oxalyl dichloride; N,N-dimethyl-formamide / dichloromethane 3: N,N-dimethyl-formamide; triethylamine / dichloromethane / 0.25 h 4: trifluoroacetic acid / dichloromethane / 1 h / 20 °C View Scheme

sulfuryl dichloride in dichloromethane T=20°C; 18 h; Inert atmosphere;

lithium hydroxide hydrate in ethanol; water 1 h; Reflux;