Acetic Acid → 5-Iodopyrazolo[1,5-a]pyridine-3-carboxylic acid

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Reaction Conditions

Reaction Steps

A 22 L round bottom flask was charged with ethyl 5-iodopyrazolo[1,5-a]pyridine-3-carboxylate (I-41) (376 g, 1.19 mol), KOH (133.5 g), EtOH (3856 mL) and water (290 mL). The mixture was heated to 55° C. and stirred at 55° C. for 3 hours. A sample was taken for analysis and HPLC showed no (I-41) remaining. Water (2.5 L) was added to obtain a dark solution with some insoluble solids which were removed by filtration. To the filtrate was added acetic acid (150 g, 2.5 mol) until pH˜6 followed by water (4 L). The mixture was stirred at 15 to 20° C. over 30 minutes to form a slurry that was filtered and rinsed with EtOH/H2O (1:2 v/v) to yield 5-iodopyrazolo[1,5-a]pyridine-3-carboxylic acid (I-42) as a red solid. 1H NMR (500 MHz, DMSO-d6) δ 12.62 (b, 1 H), 8.65 (d, 1 H), 8.44 (d, 1 H), 8.37 (s, 1 H), 7.37 (dd, 1 H).

Provenance & Evidence