3,5-Diaminobenzoic acid → 3-amino-5-(N-cyclohexylmethylamino)benzoic Acid

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Reaction Steps

15.2 g. (0.1 mol) of 3,5-diaminobenzoic acid was placed in a 500 ml. round bottom flask to which 200 ml. of methanol was added. To the round bottom flask 11.22 g. (0.1 mol) of cyclohexane carboxyaldehyde was added. The solution was stirred for several minutes. While the solution stirred, 3.77 g. (0.06 mol) sodium cyanoborohydride was added slowly. After 5 hours the solution was filtered and then concentrated to dryness. The reaction mixture was dissolved in 200 ml. of 2M hydrochloric acid. The acid solution was extracted twice with 200 ml. ethyl acetate. The ethyl acetate solutions were combined and back washed with 200 ml. distilled water, and then dried over sodium sulfate. The solution was concentrated to dryness and 4.18 gm. of product was collected. The product was then purified by column chromatography using a solution of tetrahydrofuran/ethanol/water/ammonium hydroxide in the following ratio--10:3:1:0.04 as the eluent. Structural verification was obtained by carbon magnetic resonance, proton magnetic resonance and infra-red analysis.

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