Nitric Acid → 3-(3-chloro-4-nitro-1H-pyrazol-1-yl)pyridine

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To a 100 mL round bottom flask was charged 3-(3-chloro-1H-pyrazol-1-yl)pyridine (2.0 g, 11 mmol) and concentrated sulfuric acid (4 mL). This suspension was cooled to ˜5° C. and 2:1 (v/v) concentrated nitric acid/sulfuric acid (3 mL, prepared by adding the concentrated sulfuric acid to a stirring and cooling solution of the nitric acid) was added dropwise at a rate such that the internal temperature was maintained <15° C. The reaction was allowed to warm to 20° C. and stirred for 18 hours. A sample of the reaction mixture was carefully diluted into water, basified with 50% sodium hydroxide (NaOH) and extracted with ethyl acetate. Analysis of the organic layer indicated that the reaction was complete. The reaction mixture was carefully added to ice cold water (100 mL) at <20° C. and basified with 50% sodium hydroxide at <20° C. The resulting light yellow suspension was stirred for 2 hours and filtered. The filter cake was rinsed with water (3×20 mL) and dried to afford an off-white solid (2.5 g, quantitative): mp 141-143° C.; 1H NMR (400 MHz, DMSO-d6) δ 9.86 (s, 1H), 9.23-9.06 (m, 1H), 8.75-8.60 (m, 1H), 8.33 (ddd, J=8.4, 2.8, 1.4 Hz, 1H), 7.64 (ddd, J=8.5, 4.7, 0.7 Hz, 1H); 13C NMR (101 MHz, DMSO-d6) δ 149.49, 140.75, 136.02, 134.43, 132.14, 131.76, 127.22, 124.31; EIMS m/z 224 ([M]+).

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