A. 1-(2-Acetyl-4,6-dimethoxyphenyl)-1,2-hydrazinedicarboxylic acid bis(2,2,2-trichloroethyl) ester. A 2-L, round-bottomed flask, equipped with a magnetic stirrer, thermometer, and an ice bath is charged with 3,5-dimethoxyacetophenone (20.00 g, 111.0 mmol) (Note 1) and dichloromethane (CH₂Cl₂, 555 mL) (Note 1). At 0–5°C, under nitrogen, trifluoromethanesulfonic acid (980 μL, 11.1 mmol) (Note 1) is added in one portion. To the resulting yellow solution, bis(2,2,2-trichloroethyl) azodicarboxylate (BTCEAD) (50.70 g, 133.3 mmol) (Note 2) is gradually introduced over 15 min in order to maintain an internal temperature between 0–5°C.

The orange-yellow solution is stirred for 5.5 hr at room temperature until complete reaction has taken place. The reaction mixture is poured into saturated aqueous sodium bicarbonate (NaHCO₃) solution (100 mL) at 0°C. The organic phase is separated and the aqueous phase is reextracted with CH₂Cl₂ (30 mL). The combined organic layers are washed with water (H₂O) (2 × 50 mL), dried over anhydrous sodium sulfate, filtered, concentrated and placed on a vacuum pump to afford a pale yellow foam. Ethyl acetate (85 mL) is added and the crude mixture is heated under reflux until complete dissolution occurs. At reflux hexane (85 mL) is added and the solution is allowed to stand at room temperature. After a period of 15 hr the flask containing a mass of solid is cooled in an ice bath for 1.5 hr. The solid is collected by filtration and washed with a cold ethyl acetate-hexane mixture (1:4) (50 mL). The hydrazide is dried under high vacuum at 45°C for 3 days (Note 3) to provide 52.0 g (84%) of a white solid sufficiently pure for the next step (Note 4). From the mother liquor, an additional 3.8 g (6.0%) of material is recovered by flash chromatography (20% ethyl acetate in hexane) followed by recrystallization from ethyl acetate-hexane (1:1 mixture, 20 mL).

B. 5,7-Dimethoxy-3-methylindazole. A 2-L, round-bottomed flask, equipped with a magnetic stirrer and a thermometer is charged with the hydrazide (54.0 g, 96.3 mmol) and acetic acid (480 mL). To the suspension at 16°C is added zinc dust (35.6 g, 544 mmol) (Note 5) portionwise over 5 min. After a period of 10 min, the cooling bath is removed to allow the internal temperature to reach 35°C. The mixture is stirred for about 3 hr until no hydrazide is detected by TLC (30% ethyl acetate in hexane, R_f = 0.3). The mixture is filtered over Celite and washed carefully with CH₂Cl₂ (15 × 40 mL). After removal of the solvents under reduced pressure, the brown mixture is dissolved in CH₂Cl₂ (800 mL) and saturated aqueous NaHCO₃ solution (600 mL). Additional solid NaHCO₃ is then added until pH 8 is attained. The resulting milky mixture is filtered over Celite, washed carefully with CH₂Cl₂ (10 × 100 mL), and the organic phase separated. The water phase is reextracted with CH₂Cl₂ (2 × 100 mL) and the combined organic layers are dried over sodium sulfate. After evaporation under reduced pressure, the resulting green residue is dissolved in hot CH₂Cl₂ (80 mL) and purified by flash chromatography (200 g of silica gel) (5% CH₂Cl₂/30% ethyl acetate/hexane). The indazole (14.02 g) is obtained as a yellowish solid. Crude product is recrystallized twice from ethyl acetate (100 mL) to provide 9.6 g of pure indazole (52%) as white crystals (Note 6). An additional 2.8 g (15%) of pure material is recovered from the mother liquor after recrystallization.