2) The residue after removing the solvent was dissolved in 6 N HCl(aq.) (6 mL) The solution was heated to reflux for 16 hours. After the reaction was completed, the reaction mixture was allowed to cool down to 0 o C, KOH was added to adjust the pH=12 solution and saturated the solution with K2CO3. The solid was removed by filtration and washed with Et2O (5 mL). The aqueous filtrate was extracted with Et2O (4 mL × 3). The combined organic phase was dried over anhydrous Na2SO4, filtered, and evaporated under reduced pressure to give the crude bicyclic piperidone 112. The crude product was purified by flash column chromatography on silica gel using MeOH/DCM 2% to give the product as a pale-yellow oil (1.59 g, 65%). The analytical data are consistently agreed with those ones are reported in the literature.