1: disulfonyl fluoride; 1,8-diazabicyclo[5.4.0]undec-7-ene; triethylamine tris(hydrogen fluoride) / acetonitrile / 5 h / -15 - 90 °C 2: 2,2-dimethoxy-propane; hydrogenchloride; water / tetrahydrofuran / 3 h / 20 °C 3: hydrogenchloride; water / ethanol / 21 h / 20 °C 4: pyridine / 0.5 h / 20 °C / |Cooling with ice View Scheme

1: 1.) acetic acid, water, 2.) copper sulfate, toluene-p-sulfonic acid / 1.) 1,5h, 50 deg C, 2.) 24h 2: 84 percent / pyridine View Scheme