Thionyl Chloride → 4-Chloro-5-chloromethyl-1-ethyl-3-methyl-1H-pyrazolo[3,4-b]pyridine

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Reaction Steps

Into a three necked flask, fitted with a stirrer, reflux condenser and dropping funnel are added 94.6 g. of 4-chloro-1-ethyl-3-methyl-1H-pyrazolo[3,4-b]pyridine-5-methanol (0.42 mol.) (U.S. Pat. No. 3,983,128; Example 2). While stirring 475 ml. of thionyl chloride are added dropwise within 45 minutes and the mixture is then refluxed for one and a half hours. The excess thionyl chloride is removed by a rotary evaporator and the residue is dissolved in benzene. The solvent is again removed and the remaining solid product is triturated with ligroin, filtered and dried at 70°, yield 91 g. of 4-chloro-5-chloromethyl-1-ethyl-3-methyl-1H-pyrazolo[3,4-b]pyridine, which, after recrystallization from hexane, gives 83.5 g. of pure product, m.p. 96°-97°. Evaporation of the ligroin mother liquor and recrystallization of the residue gives a second crop of 5.7 g. (m.p. 95°-96°). Total yield: 89.2 g. (87%).

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