1: pyridine / 3 h / 20 °C 2: 165 mg / pyridine; 4-(dimethylamino)pyridine / 27 h / 20 °C 3: 99 percent / HF / acetonitrile / 7 h / 20 °C 4: H2CrO4 / acetone / 6 h / 0 - 20 °C 5: aq. NaOH / 10 h / 20 °C 6: 96 percent / bis(2-oxo-3-oxazolidinyl)phosphinic chloride; Et3N / CH2Cl2 / 3 h / 20 °C View Scheme

1: pyridine / 3 h / 20 °C 2: 165 mg / pyridine; 4-(dimethylamino)pyridine / 27 h / 20 °C 3: 99 percent / HF / acetonitrile / 7 h / 20 °C 4: H2CrO4 / acetone / 6 h / 0 - 20 °C 5: aq. NaOH / 10 h / 20 °C View Scheme