Benzaldehyde → 3(R)-(benzylamino)-2,3,4,5-tetrahydro-1H-benzazepin-2-one

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Reaction Steps

A solution of 528 mg (3.0 mmol) of 3(R)-amino-2,3,4,5-tetrahydro-1H-1-benzazepin-2-one (Example 1, Step B) in 45 mL of absolute methanol at room temperature was treated with 4.5 g of powdered 3A molecular sieves followed by dropwise addition of a solution of 954 mg (9.0 mmol, 3 eq.) of benzaldehyde in 15 mL of methanol. The pH of the mixture was adjusted to 7 by addition of trifluoroacetic acid then stirred at room temperature for 2 hours. Sodium cyanoborohydride (18 mL of 1.0M THF solution; 18 mmol, 6 eq.) was added and the mixture stirred at room temperature for 18 hours. The mixture was filtered and the filtrate treated with 3 mL of trifluoroacetic acid with stirring for 3 hours, then all volatiles removed under vacuum and the residue dissolved in 50 mL of ethyl acetate. The ethyl acetate solution was washed with water (3×15 mL), saturated aqueous sodium bicarbonate (2×15 mL) and 15 mL of brine then dried over magnesium sulfate, filtered and solvents removed under vacuum. The residue was purified by chromatography on silica, eluting with ethyl acetate/hexane (70:30), to afford 410 mg (1.54 mmol, 51%) of the product. 1H NMR (200 MHz,CDCl3): 2.05 (m,1H), 2.5-3.0 (m,3H), 3.37 (dd;7,11 Hz;1H), 3.57 (d,12 Hz,1H), 3.90 (d,12 Hz,1H), 7.05 (d,8 Hz,1H), 7.1-7.4 (m,8H), 7.75 (br s,1H). FAB-MS: calculated for C17H18N2O 266; found 267 (M+H,75%).

Provenance & Evidence