Phosphorus oxychloride → Ethyl 4-chloro-1-ethyl-6-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylate

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Reaction Conditions

Reaction Steps

A mixture of 5-amino-1-ethylpyrazole (1.614 g, 14.5 mmol) and diethyl 2-(1-ethoxyethylidene)malonate (3.68 g, 16.0 mmol, as described by P. P. T. Sah, J. Amer. Chem. Soc., 1931, 5, 1836) was heated at 150° C. under Dean Stark conditions for 5 hours. Phosphorous oxychloride (25 ml) was carefully added to the mixture and the resulting solution was heated at 130° C. under reflux for 18 hours. The mixture was concentrated in vacuo, then the residual oil was carefully added, with cooling, to water (100 ml). The resulting mixture was extracted with DCM (3×100 ml) and the combined organic extracts were dried over anhydrous sodium sulphate and concentrated in vacuo. The residual oil was purified by Biotage chromatography (silica, 90 g) eluting with ethyl acetate-petrol (1:19). Fractions containing the desired product were combined and concentrated in vacuo to afford Intermediate 58 (1.15 g). LCMS showed MH+=268; TRET=3.18 min.

Provenance & Evidence