Bis[(4-chlorophenyl)methyl](4-chloro-3-butynyl)amine (5) (31.8 mg, 0.090 mmol) was used as a raw material and reacted with rhodium trifluoroacetate dimer (Rh2(tfa)4, 1.18 mg, 0.018 mmol) under argon protection in a mixed solvent of toluene (1.0 mL) and water (0.01 mL) at a heated reflux for 10 hr. After the reaction was completed, the mixture was cooled down. After completion of the reaction, the mixture was cooled to room temperature and filtered through a short diatomaceous earth pad assisted with ethyl acetate. The filtrates were combined and concentrated under reduced pressure to obtain the crude product. The crude product was purified by silica gel column chromatography (eluent: hexane-ethyl acetate mixed solvent) to give N-cyclohexylpyrrolidone (15.5 mg, 82% yield) as a final oil. The structure of the product was confirmed by 1H NMR, 13C NMR and IR: 1H NMR (δ, ppm): 2.01 (quintuple peak, J = 7.7 Hz, 2H), 2.45 (t, J = 7.7 Hz, 2H), 3.26 (t, J = 7.7 Hz, 2H), 4.42 (s, 2H), 7.18 (d, J = 8.4 Hz, 2H), 7.30 ( d, J = 8.4 Hz, 2H); 13C NMR (δ, ppm): 17.78, 30.81, 46.02, 66.60, 128.87 (2C), 129.51 (2C), 133.51, 135.22, 174.97; IR (pure, cm-1): 3060, 3049, 2926, 1682 (C=O) , 1493, 1093, 1016, 802.
