Formaldehyde → (+/-)-cis-N1-Benzyl-N2-tert-butoxycarbonyl-N1-methyl-1,2-cyclohexanediamine

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Reaction Steps

(±)-cis-N1-Benzyl-N2-tert-butoxycarbonyl-1,2-cyclohexanediamine (3.24 g) was dissolved in methanol (30 ml), and to the solution an aqueous solution (35%, 0.909 ml) of formaldehyde was added, and the mixture was stirred at room temperature for 10 minutes. Sodium cyanoborohydride (666 mg) was added to this mixture, and the resultant mixture was stirred at room temperature for 6 hours. Thereafter, a saturated aqueous solution of sodium hydrogencarbonate was added, and the solvent was concentrated under reduced pressure. Dichloromethane was added to the residue to separate an organic layer. The organic layer was dried over anhydrous sodium sulfate, and the solvent was distilled off under reduced pressure. The residue was purified by flash column chromatography on silica gel (hexane:ethyl acetate=3:1) to obtain the title compound (1.98 g) as a yellow oil.

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