1: 43 percent / NaOH / H2O / 4 h / Heating 2: 1.) hexamethyldisilazane, trimethylchlorosilane, 2.) conc. HCl / 1.) acetonitrile, reflux, 4 h, 2.) methanol, 10 min 3: oxalyl chloride, DMF / 2 h / 0 °C 4: 4-(dimethylamino)pyridine / a) 0 deg C 30 min, b) RT, 30 min View Scheme

1: 1.) hexamethyldisilazane, trimethylchlorosilane, 2.) conc. HCl / 1.) acetonitrile, reflux, 4 h, 2.) methanol, 10 min 2: oxalyl chloride, DMF / 2 h / 0 °C 3: 4-(dimethylamino)pyridine / a) 0 deg C 30 min, b) RT, 30 min View Scheme

1: oxalyl chloride, DMF / 2 h / 0 °C 2: 4-(dimethylamino)pyridine / a) 0 deg C 30 min, b) RT, 30 min View Scheme

4-(N,N-dimethlyamino)pyridine a) 0 deg C 30 min, b) RT, 30 min; Yield given;