Synthesis, spectral characterization, single crystal and conformational study of 1,5-dimethyl-2,4-diphenyl-3-azabicyclo[3.3.1]nonan-9-one derivatives

1,5-Dimethyl-2,4-diphenyl-3-azabicyclo[3.3.1]nonan-9-one 1 and their derivatives 2–8 were obtained by condensation of 2,6-dimethyl cyclohexanone, Ammonium acetate and substituted aromatic aldehydes and characterized by FT-IR, FT-Raman, 1H NMR, 13C NMR, GC–MS, HOMOCOSY, HSQC, NOESY, single crystal X-ray diffraction analysis and theoretical DFT calculation. Compound 1 crystallized in the Triclinic system, space group P-1 with a = 6.8950(5) Ǻ, b = 11.5889(9) Ǻ, c = 11.9172(9) Ǻ, α = 76.277(4)°, β = 78.000(3)°, γ = 72.920(4)°, V = 874.41(12) Ǻ3 and Z = 2. 1,5-Dimethyl-2,4-diphenyl-3-azabicyclo[3.3.1]nonan-9-one 1 and their derivatives 2–8 were exist in boat–chair conformation with equatorial orientation of all the substituents at piperidine ring (two phenyl rings at C-2 and C-4 position, two methyl substituents at C-1 and C-5 position) of compound 1. In the crystal structure of compound 1, the molecules are connected by NH⋯OC intermolecular hydrogen bonds. The existence of boat–chair conformation was confirmed by single crystal X-ray diffraction analysis and theoretical DFT calculation.