lH-Pyrazolo[3,4b]pyridine-3-carboxylic Acid.
KMnO4ZNaOHZH2O
reflux, 2 h
Sodium hydroxide (35 g, 0.88 mol) was dissolved in water (800 mL), then 3- methyl-lH-pyrazolo[3,4b]pyridine (16 g, 0.12 mol) was added to a solution of sodium hydroxide and stirred at room temperature for 10 minutes. The reaction mixture was heated to 80 0C. Under good stirring potassium permanganate solution (68.5 g, 0.433 mol OfKMnO4 in 300 mL water) was slowly added dropwise over a period of 2 h, keeping the oil bath temperature at 100 0C. After completing the addition of potassium permanganate, the reaction mixture was further heated for 1 hr. The progress of the reaction was monitored by TLC. The reaction mixture was cooled to 70-80 0C and the byproduct manganese dioxide was filtered off. The manganese dioxide cake was washed with hot water. The main filtrate and the washings were combined and acidified to pH 2 with concentrated sulfuric acid. The water was then distilled off under reduced pressure using a rotary evaporator. The yellow solid obtained was a mixture of the desired IH- pyrazolo[3,4b]pyridine-3-carboxylic acid, sodium sulfate and potassium sulfate (95 g). This mixture of solids was taken without purification to the next step. A small sample was purified by column chromatography for analytical purposes to afford white crystals mp 175-176 0C.
1H NMR (CDCl3) 8.28 (dd, J = 4.9 and 1.6 Hz, 1 H), 7.82 (dd, J = 7.5 and 1.6 Hz, 1 H), 7.39 (dd J = 7.5 and 4.9 Hz, 1 H).
MS 9FAB) m/z: 147 (M+ + 1)
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सुकून उतना ही देना प्रभू, जितने से
जिंदगी चल जाये।
औकात बस इतनी देना,
कि औरों का भला हो जाये।
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