N,N-Dimethylaniline → Ethyl 7-chloro-6-(2-ethoxy-2-oxoethyl)-5-methylpyrazolo[1,5-a]pyrimidine-2-carboxylate

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Reaction Conditions

Reaction Steps

A mixture of ethyl 6-(2-ethoxy-2-oxoethyl)-7-hydroxy-5-methylpyrazolo[1,5-a]pyrimidine-2-carboxylate (25 g, 81 mmol), and N,N-dimethylaniline (20.6 mL, 163 mmol) in POCl3 (100 mL) was heated at 120° C. for 3 h. Then the reaction was cooled to rt and concentrated in vacuo to half the volume. It was poured into a large quantity of ice water and stirred for 20 min. Precipitates formed and were collected by filtration. This solid was dissolved in ethyl acetate (1 L) and washed with water. The aqueous phase was back-extracted with ethyl acetate and the combined organic layers were washed with brine (200 mL), dried (Na2SO4), filtered and concentrated in vacuo. The crude was then triturated with EtOAc/hexane to afford ethyl 7-chloro-6-(2-ethoxy-2-oxoethyl)-5-methylpyrazolo[1,5-a]pyrimidine-2-carboxylate (22 g, 67.5 mmol, 83% yield) as light yellow solid. 1H NMR (500 MHz, CDCl3) δ 7.21 (s, 1H), 4.52 (q, J=7.2 Hz, 2H), 4.24 (q, J=7.2 Hz, 2H), 3.94 (s, 2H), 2.66 (s, 3H), 1.48 (t, J=7.0 Hz, 3H), 1.30 (t, J=7.2 Hz, 3H). LCMS (M+1)=326.2.

Provenance & Evidence