Acetone → 1-(5-Amino-6-chloro-1H-benzoimidazol-2-yl)-1H-pyrazole-4-carboxylic acid

Participants

Reaction Steps

1-[5-Amino-6-chloro-1-(2-methoxy-ethoxymethyl)-1H-benzoimidazol-2-yl]-1H-pyrazole-4-carboxylic acid ethyl ester. To a solution of 1-[6-chloro-1-(2-methoxy-ethoxymethyl)-5-nitro-1H-benzoimidazol-2-yl]-1H-pyrazole-4-carboxylic acid ethyl ester (Intermediate D from Example 40) (7.88 g, 18.6 mmol), ammonium chloride (14.9 g, 0.279 mol), acetone (75 mL), and water (15 mL) at 0° C. was added portion-wise zinc dust (12.2 g, 0.186 mol). The reaction mixture was removed from the ice bath and after 15 min, the reaction mixture was filtered through Celite®/diatomaceous earth and rinsed with EtOAc. The filtrate was concentrated and the remainder was partitioned between EtOAc (300 mL) and saturated aqueous sodium bicarbonate (55 mL). The aqueous layer was further extracted with EtOAc (2×125 mL). The combined organic layers were washed with brine (2×40 mL), dried, filtered, and concentrated under reduced pressure. The residue was purified (FCC) (5-65% EtOAc/hexanes) to yield the titled compound (6.29 g, 86% yield) as a 1:1 mixture of regioisomers. MS (ESI/CI): mass calcd. for C17H20ClN5O4, 393.1; m/z found, 394.1 [M+H]+. 1H NMR (400 MHz, CDCl3): 8.83 (d, J=0.6 Hz, 1H), 8.78 (d, J=0.6 Hz, 1H), 8.16 (dd, J=1.9, 0.6 Hz, 2H), 7.63 (s, 1H), 7.54 (s, 1H), 7.09 (s, 1H), 6.96 (s, 1H), 6.03 (s, 2H), 6.00 (s, 2H), 4.35 (q, J=7.1 Hz, 4H), 4.18 (s, 2H), 4.07 (s, 2H), 3.66-3.60 (m, 4H), 3.49-3.42 (m, 4H), 3.32 (s, 3H), 3.31 (s, 3H), 1.37 (t, J=7.1 Hz, 6H).

Provenance & Evidence