Nitric Acid → HCID 53754201, compound

Participants

Reaction Conditions

Reaction Steps

Concentrated nitric acid (5 mL) was added to concentrated sulfonic acid (5 mL) at 0° C., and the solution was cooled thoroughly for an additional 10-15 minutes. Ethyl benzimidazole-2-acetate (Buchi, J.; Zwicky, H.; Aebi, A., Archiv. Der Pharmazie 1960, 293, 758; 1.09 g, 5.34 mmol, 1 equiv.) was added portionwise over several minutes The resulting yellow solution was stirred at 0° C. for 20 minutes then was poured carefully onto cracked ice (100 g). The pH was adjusted to 5 with cold 20% sodium carbonate (50-75 mL) and the mixture was extracted with ethyl acetate (3×50 mL). Drying (sodium sulfate), concentration, and silica gel chromatography (3:2 ethyl acetate/toluene) gave ethyl 5-nitrobenzimidazole-2-acetate (1.23 g, 92%) as a yellow solid. TLC (3:2 ethyl acetate/toluene) Rf 0.44; 1H NMR (400 MHz, CDCl3) δ 8.54 (br s, 1H), 8.21 (dd, J=8.9, 2.1 Hz, 1H), 7.58-7.70 (m, 1H), 4.31 (q, J=7.1 Hz, 2 H), 4.14 (s, 2 H), 1.35 (t, J=7.1 Hz, 3 H); IR (chloroform) 3390, 1727, 1523, 1345, 1309 cm-1 ; MS (ESMS) 250.0 (M+H)+.

Provenance & Evidence