Ugi Reaction; N-allyl-N-(2-(cyclohexylamino)-2-oxo-1-phenylethyl)-3-nitropropanamide
Chemicals UsedBenzaldehyde (Acros Organics)Allylamine (Merck)Cyclohexyl isocyanide (Merck)3-Nitropropionic acid (Sigma)MeOHProcedureA solution of benzaldehyde (1.70 mmol, 0.172 mL), allylamine (1.70 mmol, 0.128mL), cyclohexyl isocyanide (1.70 mmol, 0.211 mL) and 3-nitropropionicacid (1.70 mmol, 0.202 g) in 10 mL MeOH was stirred at room temperature undernitrogen atmosphere. After 28 h, the solution was concentrated under reducedpressure to leave a pale yellow solid. The residue was washed with cold Et2O (3x 20 mL) to give pure title compound as a white solid (475 mg, 75% yield, mp190-192 °C, Rf= 0.44 (ethyl acetate-hexane; 1 : 1). 1H and 13C NMR spectrashowed title compound is a mixture of two rotamers in an approximately 1:4.5ratio.
1-cyclohexenyl isocyanide (47 mg, 50.2 µL,0.44 mmol) was added to a solution ofpropionic acid (33 mg, 32.9 µL,0.44 mmol), aniline (41 mg, 40.1 µL, 0.44 mmol), 4- phenylethylpiperidone (90 mg, 0.44 mmol) in MeOH (2.2 mL) at room temperature and the solutionwas heated at 55 C and stirred for 24 h. The solvent was removed underreduced pressure, and the residue was dissolved in EtOAc (5 mL). The organic solution was washed with sat aq NaHCO3 (2 2.5 mL) and brine (2.5 mL) and dried (MgSO4), and the solvent was removed under reduced pressure. The crude product was purified either via HPLC/MS preparative with gradient starting from 10% MeOH / 90% H2O / 0.1% ammonia reaching 100% MeOH / 0.1%ammonia. The product was obtained in 82% yield (165 mg). Reference: Tetrahedron Letters Volume 51, Issue 22, 2 June 2010, Pages 2983-2985
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