5-Nitro-1-(tetrahydro-2H-pyran-2-yl)-1H-indazole-3-carbaldehyde (100 mg, 0.363 mmol) and o-phenylene diamine (40 mg, 0.369 mmol) were dissolved in dry THF (8 mL), and 2N HCl (1 drop) was added. The solution was heated at a gentle reflux for 30 min and then 1N sodium bisulfite (1 mL) was added. After overnight at reflux, the solution was cooled to room temperature, and diluted with ethyl acetate (40 mL). The mixture was washed with water and brine, dried over Na2SO4, and concentrated. Purification by flash chromatography (20% ethyl acetate/hexane) afforded the title compound as a pale yellow solid in a 50% yield. 1H NMR (400 MHz, CDCl3): δ 9.82 (s, 1H), 9.60 (d, 1H, J=2.4 Hz), 8.30 (dd, 1H, J=2.0 & 9.2 Hz), 7.87 (m, 1H), 7.66 (d, 1H, J=9.2 Hz), 7.47 (m, 1H), 7.28 (m, 2H), 5.77 (dd, 1H, J=2.4 and 8.8 Hz), 4.00 (m, 1H), 3.76 (m, 1H), 2.53 (m, 1H), 2.13 (m, 2H), 1.77 (m, 3H).
