oxalic acid; silica gel in methanol; dichloromethane; water 0.25 h; Ambient temperature;

1: 75 percent / NH3 liq., Li / propan-2-ol; tetrahydrofuran / -45 °C 2: 85 percent / Py*SO3 / dimethylsulfoxide; triethylamine / Ambient temperature 3: 92 percent / oxalic acid, silica gel / CH2Cl2; methanol; H2O / 0.25 h / Ambient temperature View Scheme

1: 85 percent / Py*SO3 / dimethylsulfoxide; triethylamine / Ambient temperature 2: 92 percent / oxalic acid, silica gel / CH2Cl2; methanol; H2O / 0.25 h / Ambient temperature View Scheme

pyridinium hydrobromide perbromide in pyridine Ambient temperature;