1-Benzyl-3-ethoxycarbonyl-4-piperidone

To a suspension of NaH (5.38 g, 0.13 mol) in benzene, a solution of Michael adduct 131 (25 g, 0.09 mol) in PhH was added drop-wise and refluxed for 3 hours. The reaction mixture was allowed to cool and quenched with saturated NH4Cl solution, extracted with ethyl acetate, washed with water, brine, dried over anhydrous Na2SO4, filtered and concentrated in vacuo. Column chromatographic separation over silica gel (EtOAc- pet ether) afforded ketoester, as a pale yellow oil (18.15 g).