The compound (1.98 g, 5.75 mmol) obtained in Step 2 was dissolved in a mixture of acetonitrile (40 ml) and water (15 ml), to which was added CAN (7.90 g, 14.5 mmol) and the mixture was stirred at room temperature for 40 minutes. The reaction mixture was poured into water and was extracted with ethyl acetate. After the extract was washed with water and dried, the solvent was distilled off. Ether was added to the residue and the resulting precipitate was filtered to yield the title compound (1.82 g, 5.76 mmol, yield 99%).
