1: 100 percent / i-Bu2AlH / hexane; CH2Cl2 / 0.25 h / -78 °C 2: 1.) NaH / 1.) THF, RT, 2 h, 2.) THF, overnight 3: 100 percent / Bio Rad AG 50W-X8 ion-exchange resin / methanol 4: 100 percent / oxalyl chloride, DMSO / CH2Cl2 / 0.33 h / -78 °C View Scheme