1: 88 percent / HCl / tetrahydrofuran / Ambient temperature 2: tetrahydrofuran / 0 °C 3: 1.) DMSO, (ClCO)2, 2.) Et3N / 1.) CH2Cl2, -78 deg C, 2.) 0 deg C View Scheme

pyridinium p-toluenesulfonate; triethylamine; trifluoroacetic anhydride 1.) (CH3)2CO, H2O, reflux and THF, -78 deg C, 2.) DMSO/CH2Cl2, -50 deg C; Yield given. Multistep reaction;