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With hydrazine hydrate In dimethyl sulfoxide at 140℃; for 0.5h;
1B-3B (B) Synthesis of 4-chloro-7-methyl-1H-indazole:
In a 3L four-necked flask674g of 6-chloro-2-fluoro-3-methylbenzaldehyde was dissolved in 2L of dimethyl sulfoxide, and 488.4g of hydrazine hydrate was added under mechanical stirring.Heated to 140 for 0.5h,The low-boiling solvent and water were separated, and then the temperature was raised to 140 ° C for 4-5 days. TLC analysis of the raw material reaction is complete, pour the reaction solution into 10L of water, stir, filter, wash, dissolve the filter cake in 10L of ethyl acetate, wash with water, dry over anhydrous sodium sulfate, evaporate the excess solvent, and beat with 500ml petroleum ether. 204.8 g of 4-chloro-7-methyl-1H-indazole solid was obtained by filtration and drying, and the yield was 31.6%.