Example 3: Synthesis of 7-(2,4-dichlorophenyl)-2,3-dimethyl-2H-indazole hydrochloride
Step 1: To 30 mL of toluene, 7-bromo-1H-indazole (3; 1.71 g, 8.67 mmol) and dimethyl sulfate (0.90 mL, 9.5 mmol) were added. The reaction mixture was stirred at 110 °C for 4 h and subsequently cooled to room temperature. Upon completion of the reaction, the mixture was carefully washed with 30 mL of saturated aqueous NaHCO3 to neutralize the unreacted dimethyl sulfate. The organic layer was dried over anhydrous MgSO4, filtered (the filter cake was washed with ether) and concentrated under reduced pressure to give an orange colored oil. Purification by column chromatography (eluent: 0-50% EtOAc/hexane) afforded 7-bromo-2-methyl-2H-indazole (6: R = Me; 1.33 g, 73%) as a light tan solid.
