Yield:93587-26-9 89%

Reaction Conditions:

with sulfuric acid;nitric acid in water at 0 - 12; for 2 h;

Steps:

2.A

Step A; A solution of HNO₃ was prepared by mixing 90 % HNO₃ (8 ml) and 65 % HNO₃ (4 ml). The solution was cooled to 0 °C and the title compound from Preparative Example 1 (4 g) added in portions. After the complete addition, cone. H₂SO₄ (13.6 ml) was slowly added as to keep the internal temperature below 12 °C. After the complete addition, the mixture was stirred in the ice bath for 2 h to become a clear, yellow solution. This solution was then poured onto a mixture of 30 g ice and 60 ml H₂O. A precipitate was formed and allowed to stand for 30 min. The precipitate was collected by filtration, washed with H₂O (160 ml) and dried in HV to afford the title compound as a yellow solid (4.78 g, 89 %). ¹H-NMR (DMSOd₆) δ 8.10 (s, IH), 8.52 (d, IH), 12.58 (s, IH), 13.50 (s, IH)

References:

WO2008/63669,2008,A1 Location in patent:Page/Page column 67-68