The general procedure for the synthesis of N-Boc-1,4-diaza-5-cycloheptanone from 4-oxime-1-Boc-piperidine was as follows: to a solution of tetrahydrofuran (THF, 10 mL) containing the ketoxime (0.01 mol) was added T3P (15 mol%, 50% solution in ethyl acetate). The reaction mixture was stirred at reflux for 1-4 h under nitrogen protection. The progress of the reaction was monitored by thin layer chromatography (TLC) and after confirming the completion of the reaction, the solvent was removed under reduced pressure. The residue was diluted with distilled water (20 mL) and subsequently extracted with ethyl acetate (2 x 20 mL). The organic phases were combined and washed sequentially with saturated sodium bicarbonate (NaHCO3) solution (1 × 10 mL) and brine. The organic phase was dried over anhydrous sodium sulfate (Na2SO4) and concentrated under reduced pressure to give a high purity target amide product.
