Example 1 7-Bromo-2H-indazole Step 1 3-Bromo-2-nitrotoluene (Scheme 1; IC) - Copper (II) bromide (3.52 g, 15.7 mmol) was dissolved in 20 mL of anhydrous acetonitrile, under nitrogen protection, and heated to 65°C. Subsequently, tert-butyl nitrite (2.35 mL, 2.03 g, 19.7 mmol) was added all at once. 3-Methyl-2-nitroaniline (LB; 2.00 g, 13.1 mmol; J. Org. Chem. 1976, 41, 3357) was dissolved in 15 mL of acetonitrile and slowly added dropwise to the above solution, maintaining gentle reflux. After dropwise addition, the reaction was continued under mild reflux conditions for 15 min. After the reaction mixture was cooled to room temperature, it was separated by extraction with 6N hydrochloric acid solution (150 mL) and ether (150 mL). The ether phase was collected, washed with saturated brine and dried over anhydrous magnesium sulfate. The solvent was removed by concentration under reduced pressure to give 2.76 g of crude product. Purification by silica gel column chromatography with 10% acetone/hexane as eluent gave 1.62 g (57% yield) of the target product 1c as a light yellow-green liquid.
