Hydrochloric Acid → 4-chloro-5-phenyl-1H-pyrazolo[3,4-c]pyridazine

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Reaction Conditions

Reaction Steps

Sodium nitrite (4.3 g, 63 mmol) was added to conc. HCl (314 mL) at −15° C. and stirred for 10 min. 1-(1-ethoxyethyl)-4-(phenylethynyl)-1H-pyrazol-5-amine (3 g, 31.4 mmol) was added and the mixture stirred at −10° C. for 10 min and room temperature for 1 d. The reaction mixture was cooled to 0° C. and CH2Cl2 (250 mL) was added. Under vigorous stirring, Na2CO3 (160 g) was added carefully followed by sat. aq. NaHCO3 solution over a period of 2 h until the pH was 7 and there was no more foaming on further addition of base. The layers were separated and the aqueous phase was extracted with CH2Cl2. The combined organic layers were dried (MgSO4), filtered and concentrated in vacuo. The residue was purified by column chromatography (silica gel, iso-hexanes/diethyl ether 1:0 to 0:1) yielding the title compound as a solid (3.43 g).

Provenance & Evidence