Methanol → (2S,3S)-6-Methoxy-1,3,3-trimethyl-5-[(2-phenyl-piperidin-3-ylamino)-methyl]-1,3-dihydro-indol-2-one

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Reaction Steps

To 6-Methoxy-1,3,3-trimethyl-2-oxo-2,3-dihydro-1H-indole-5-carbaldehyde (936 mg, 4.0 mmol) in 50 mL of toluene was added (2S,3S)-2-Phenyl-piperidin-3-ylamine (1.0 g, 4.0 mmol) and 3 mL of methanol. The solution was heated to reflux with azeotropic water removal for 48 h. The solution was then concentrated and the residue was dissolved in CH2Cl2. Sodiumtriacetoxyborohydride (1.0 g, 4.7 mmol) was added and the mixture was stirred overnight. The mixture was then quenched with satd NaHCO3 and the layers were separated. The aqueous portion was extracted with CH2Cl2 (2×20 mL). The combined organic portions were washed successively with brine and water and concentrated. Silica gel chromatography (10:1 EtOAc/MeOH) gave 1.27 g (81%) of the title compound as an orange oil. Treatment of the oil with ethereal HCl gave 1.44 g of the dihydrochloride salt as an off-white solid.

Provenance & Evidence