Cesium carbonate → 1-[6-Chloro-1-(2-methoxy-ethoxymethyl)-5-nitro-1H-benzoimidazol-2-yl]-1H-pyrazole-4-carboxylic acid ethyl ester

Participants

Reaction Conditions

Reaction Steps

To a solution of 2,6-dichloro-1-(2-methoxy-ethoxymethyl)-5-nitro-1H-benzoimidazole (6.15 g, 19.2 mmol), 1H-pyrazole-4-carboxylic acid ethyl ester (2.96 g, 21.1 mmol) and DMF (40 mL) was added cesium carbonate (12.5 g, 38.4 mmol) in a sealable pressure vessel. The vessel was purged with nitrogen, sealed, and heated at 60° C. for 2 h. The reaction mixture was poured into a 1:1 mixture of brine/water (80 mL), and was extracted with EtOAc (3×125 mL). The combined organic layers were washed with brine (3×125 mL), dried, filtered, and concentrated under reduced pressure. The residue was purified (FCC) (5-45% EtOAc/hexanes) to yield the titled compound (8.09 g, 98%) as a mixture of regioisomers. MS (ESI/CI): mass calcd. for C17H18ClN5O6, 423.1; m/z found, 424.1 [M+H]+. 1H NMR (400 MHz, CDCl3): 8.93 (d, J=0.6 Hz, 1H), 8.28 (s, 1H), 8.22 (d, J=0.6 Hz, 1H), 7.83 (s, 1H), 6.26 (s, 2H), 4.37 (q, J=7.1 Hz, 2H), 3.73-3.67 (m, 2H), 3.49-3.44 (m, 2H), 3.29 (s, 3H), 1.39 (t, J=7.1 Hz, 3H).

Provenance & Evidence