Stannous chloride

N-Methyl-4-piperidinone, stannous chloride and allaromatic aldehydes were purchased from Sinopharm Chemical Reagent Co. Ltd (Shanghai, China) and used as obtained without further purification. Compounds (3E,5E)-3–(2-fluorobenzylidene)-1-methyl-5–(3-nitrobenzylidene)piperidin-4-one (83), (3E,5E)-3-(3-aminobenzylidene)-5-(2-fluorobenzylidene)-1-methylpiperidin-4-one (92) were prepared based on a literature¹⁹ . NMR data were collected using a Bruker Avance 400 MHz for ¹H NMR with chemical shifts δ relative to TMS, while ¹³ (link)C NMR data were collected at 100 MHz on a Bruker Avance 400 MHz spectrometer or 150 MHz on a Bruker Avance 600 MHz spectrometer (Bruker Scientific, Billerica, MA). The HREIMS data were obtained on a Finnigan-MAT-95 mass spectrometer (Bruker Scientific, Billerica, MA).

Cyclohexanone, N-methyl-4-piperidinone, 4-piperidone hydrate hydrochloride, tetrabutyl ammonium bromide (TBAB), stannous chloride and all aromatic aldehydes were purchased from Sinopharm Chemical Reagent Co. Ltd (Shanghai, China) and were used as obtained without further purification. Compounds (2E,6E)-2,6-bis(3-aminobenzylidene)Cyclohexanone (2a) and (3E,5E)-3,5-bis(3-aminobenzylidene)-1-methylpiperidin-4-one (2b) were prepared based on a literature^{25 ,26} . ¹H NMR data were collected using a Bruker Avance 400 MHz. Chemical shifts were reported in δ relative to TMS. 13C NMR data were collected at 100 MHz on a Bruker Avance 400 MHz spectrometer, or at 150 MHz on a Bruker Avance 600 MHz spectrometer. Elemental analyses were performed on a Perkin–Elmer Model 240c analyzer. Infrared (IR) spectra were obtained in the 400–4000 cm⁻¹ range using a Perkin-Elmer Frontier Mid-IR FTIR Spectrometer.