1: dimethylsulfoxide / 1.5 h / Ambient temperature 2: KOH, hydrazine monohydrate / ethane-1,2-diol / 3 h / Heating 3: 72 percent / triethylamine / diethyl ether / 1 h / Ambient temperature View Scheme

Multi-step reaction with 2 steps 1: 88 percent / DIBAL-H / tetrahydrofuran; hexane / -40 - 20 °C2: 100 percent / SO3/pyridine; DMSO; triethylamine / CH2Cl2  

 in  dimethyl sulfoxide 1.5 h;  Ambient temperature;  Yield given;