Triethylamine → 5-Formyl-1-(3-(1-piperidinyl)phenyl)benzimidazole oxime

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Reaction Steps

To a solution of 3a1 (3.83 g, 12.9 mmol) in a mixture of formic acid (45 ml) and water (15 ml) was added Raney Ni (2.14 g, slurry in water). The mixture was refluxed with stirring for 3 hours. After cooling the mixture was filtered through celite and the filtrate was evaporated to dryness. The residue was partitioned between ethyl acetate and aqueous sodium bicarbonate (1M). The organic phase was dried over sodium sulfate and concentrated under reduced pressure. The concentrate was eluted through a short silica gel column with ethyl acetate. Evaporation of the solvent left 5-formyl-1-(3-(1-piperidinyl)phenyl)-benzimidazole (3.86 g, 100%) as an oil. This oil was dissolved in refluxing ethanol (15 ml). Hydroxyl amine hydrochloride (2.64 g, 38.0 mmol) and triethylamine (1.70 ml) was added and reflux was continued for 5 hours. The cooled mixture was rendered basic by addition of triethylamine. Water was added and the pricipitate was filtered off, washed with water and dried to yield 3b1 (2.89 g, 70%). M.p. 213-214° C.

Provenance & Evidence