Hydrochloric Acid → 2-(1H-thieno[3,2-c]pyrazol-3-yl)-1H-benzoimidazole

Participants

Reaction Conditions

Reaction Steps

A mixture of [3-(N′-benzhydrylidene-hydrazino)-thiophen-2-yl]-(1-benzyloxymethyl-1H-benzoimidazol-2-yl)-methanone (300 mg, 0.553 mmol, Example 1D), concentrated hydrochloric acid (4 mL), and ethanol (12 mL) is heated at 75° C. for 260 minutes. The reaction is allowed to cool to ambient temperature, diluted with water (40 mL), and basified with 5% aqueous potassium carbonate. The mixture is extracted with ethyl acetate and the combined extracts washed with water and brine successively. The organic layer is dried over potassium carbonate and concentrated under reduced pressure to give a brown solid. The solid is chromatographed on silica. Step gradient elution with 70% ethyl acetate/heptane, 80% ethyl acetate/heptane, and 90% ethyl acetate/heptane provided an orange solid. Trituration with ethyl acetate/heptane gave 2-(1H-thieno[3,2-c]pyrazol-3-yl)-1H-benzoimidazole as a beige powder: TLC Rf 0.28 (silica, 75% ethyl acetate/heptane); LC/MS: (M+H 241.0, RT=2.15 minutes); 1H NMR [(CD3)2SO), 300 MHz]: δ 13.56 (s, 1H), 12.94 (2, 1h), 7.78 (d, 1H, 5.3 Hz), 7.69 (d, 1H, 7.3 Hz), 7.48 (d, 1H, 7.0 Hz), 7.22-7.15 (m, 3H).

Provenance & Evidence