Procedure:  50 mL 1-neck flask, stirbar, septum, N₂ inlet

                  Dissolved 0.404 g of ketone I and 0.20 mL of pyrrolidine (II) in 5.0 mL of 1,2-dichloroethane (V).  Stirred at rt.  Added 0.140 mL of glacial acetic acid (IV) followed by 0.695 g of NaBH(OAc)₃.  The reaction mixture was stirred at rt for three days.  TLC showed product spot at Rf 0.42 (2% Et₃N-MeOH, Ninhydrin).  The reaction was quenched with 1.0 M NaOH, stirred for 30 min, and extracted with Et₂O.  The organic layer was dried over MgSO₄, filtered and the solvent was removed by rotary evaporation.  The product was isolated by flash chromatography on silica gel using 2% Et₃N-MeOH as eluant.  The product was a clear, colorless oil. 

 

¹H NMR (CDCl₃, 300 MHz) d 5.03 (br, NH, 1H), 3.17 (m, CH₂, 2H), 2.55 (m, CHs, 5H), 1.75 (m, CH₂s, 4H), 1.44 (s, C(CH₃)₃, 9H), 1.07 (d, J = 6.5 Hz, CH₃, 3H). 

 

notes

 

The use of NaBH(OAc)₃ for reductive aminations is reported to give higher yields and fewer side products than other conventional methods such as NaBH₃CN or catalytic hydrogenation (see Abdel-Magid, A.F.; Carson, K.G.; Harris, B.D.; Maryanoff, C.A.; Shah, R.D.  J. Org. Chem.  1996, 61, 3849).  The reaction can be thought of as proceeding as follows...

 

Other solvents that are reported to work for this reaction are THF and acetonitrile.