1: HCOOH / 2 h / 50 °C 2: pyridine / 2 h / Ambient temperature 3: 1.) hexamethyldisilazane, (NH4)2SO4, 2.) trimethylsilyl triflate / 1.) reflux, 1,2-dichloroethane, RT, 1.5 h 4: 72 percent / NaOEt / 24 h / Ambient temperature 5: 77 percent / methanol / 4 h / Heating View Scheme

1: HCOOH / 2 h / 50 °C 2: pyridine / 2 h / Ambient temperature 3: 1.) hexamethyldisilazane, (NH4)2SO4, 2.) trimethylsilyl triflate / 1.) reflux, 1,2-dichloroethane, RT, 1.5 h 4: 72 percent / NaOEt / 24 h / Ambient temperature View Scheme

1: HCOOH / 2 h / 50 °C 2: pyridine / 2 h / Ambient temperature 3: 1.) hexamethyldisilazane, (NH4)2SO4, 2.) trimethylsilyl triflate / 1.) reflux, 1,2-dichloroethane, RT, 1.5 h 4: 72 percent / NaOEt / 24 h / Ambient temperature 5: 77 percent / methanol / 4 h / Heating 6: 78 percent / pyridine / 2 h View Scheme