4-Nitrobenzaldehyde → [(E)-(S)-1-benzyl-4-(4-nitro-phenyl)-2-oxo-but-3-enyl]-carbamic acid tert-butyl ester

Participants

Reaction Steps

{1-[4-(4-Nitro-phenyl)-6-oxo-1,6-dihydro-pyridin-2-yl]-2-phenyl-ethyl}-carbamic acid tert-butyl ester: A suspension of ((S)-3-tert-butoxycarbonylamino-2-oxo-4-phenyl-butyl)-phosphonic acid dimethyl ester (1.114 g, 3 mmol, Resmini, M. et al., Tetrahedron Asymmetry, 2004, 15, 1847.), 4-nitrobenzaldehyde (0.453 g, 3 mmol) and potassium carbonate (0.415 g, 3 mmol) in ethanol (60 mL) was stirred at rt for 5 h. The reaction mixture was diluted with EtOAc, washed with water, brine, and dried over Na2SO4, filtered and concentrated to give 1.276 g of [(E)-(S)-1-benzyl-4-(4-nitro-phenyl)-2-oxo-but-3-enyl]-carbamic acid tert-butyl ester as a yellow solid. This yellow solid was suspended in ethanol (30 mL), then 1-ethoxycarbonylmethyl-pyridinium chloride (0.605 g, 3 mmol) and ammonium acetate (4.63 g, 60 mmol) were added. The reaction mixture was stirred at rt for 10 min, then heated at 80° C. for 5 h to yield a white suspension. The reaction was cooled to rt and the solid was collected by filtration, washed with methanol, and dried in vacuo (50° C.) to give 0.85 g (62%) of 64A as a white solid. LCMS m/z 436.3 (M+H)+. 1HNMR (400 MHz, DMSO-D6) δ: 1.26 (s, 9H), 2.76-2.82 (m, 1H), 3.01-3.06 (m, 1H), 4.68-4.74 (m, 1H), 6.54-6.60 (m, 2H), 7.18-7.29 (m, 5H), 7.40 (d, J=9.2 Hz, 1H), 7.91 (d, J=8.8 Hz, 2H), 8.34 (d, J=8.8 Hz, 2H), 11.96 (s, 1H).

Provenance & Evidence