triethylamine in dichloromethane 1 h;

1: 78 percent / fuming HNO3 / 0.5 h / 0 - 10 °C 2: 85 percent / Na2Cr2O7, AcOH, conc. H2SO4 3: oxalyl chloride, DMF / CH2Cl2 / 2.5 h 4: 100 percent / Et3N / CH2Cl2 / 1 h View Scheme

1: 85 percent / Na2Cr2O7, AcOH, conc. H2SO4 2: oxalyl chloride, DMF / CH2Cl2 / 2.5 h 3: 100 percent / Et3N / CH2Cl2 / 1 h View Scheme

1: oxalyl chloride, DMF / CH2Cl2 / 2.5 h 2: 100 percent / Et3N / CH2Cl2 / 1 h View Scheme