MAGNETIC RESONANCE IN CHEMISTRY Magn. Reson. Chem. 2001; 39: 101–104 Reference Data NMR and IR spectroscopic study of mono-, bi- and tricyclic piperidone systems V. Vijayakumar, 1 M. Sundaravadivelu 1* and S. Perumal 2 1 Department of Chemistry, Gandhigram Rural Institute—Deemed University, Gandhigram-624302, India 2 School of Chemistry, Madurai Kamaraj University, Madurai-625021, India Received 24 May 2000; Revised 3 October 2000; Accepted 5 October 2000 A number of mono-, bi- and tricyclic 4-piperidones were prepared and their NMR and IR spectra measured. The spectroscopic parameters show that the strain associated with these heterocycles decrease in the order tricyclic > bicyclic > monocyclic. It appears that in the case of the bicyclic system, part of the strain is relieved by one of its six-membered rings assuming a boat form and by flattening whereas in the tricyclic system the strain cannot be relieved to a significant extent. Copyright  2001 John Wiley & Sons, Ltd. KEYWORDS: NMR; 1 H NMR; 13 C NMR; IR; x-ray; piperidones; azabicyclo[3.3.1]nonan-9-ones; diazaadamantan-6-ones INTRODUCTION We have been interested in the synthesis and stereochemical studies of heterocycles possessing piperidine ring systems. 1–3 In continuation of these studies, we report here the results of a comparative study on the spectroscopic and structural features of the mono-, bi- and tricyclic piperidones, viz. cis-2,6-diaryl-4- piperidones (series 1), 2,4,6,8-tetraaryl-3,7-diazabicyclo[3.3.1]nonan- 9-ones (series 2) and 4,8,9,10-tetraaryl-1,3-diazaadamantan-6-ones (series 3), respectively. EXPERIMENTAL The mono-, bi- and tricyclic piperidones (series 1–3) were prepared by literature methods. 1–4 All the NMR spectra were measured using Ł Correspondence to: M. Sundaravadivelu, Department of Chemistry, Gandhigram Rural Institute — Deemed University, Gandhigram-624302, India. Bruker 360 and Jeol AMX 400 instruments. The 1 H NMR spectra were measured for approximately 0.03 M solutions in CDCl 3 at either 360 or 400 MHz with TMS as internal reference. Similarly, coupled and decoupled 13 C NMR spectra were measured for approximately 0.05 M solutions in CDCl 3 at 100 MHz with TMS as internal reference. For 13 C NMR spectra, a pulse angle of 37.5 ° (5 μs), an acquisition time of 0.72 s and a repetition time of 3.72 s were used, collecting 32K data points in the quadrature detection mode for a spectral width of 22 700 Hz. The accuracies of the 1 H and 13 C chemical shifts are considered to be 0.02 and 0.05 ppm, respectively. H,H-COSY spectra were obtained using the COSY-45 procedure and one-bond 1 H– 13 C correlations were recorded using the HETCOR pulse sequence over the required frequency ranges. The two-dimensional spectra were acquired with 1024 data points along t 2 and 512 data points along t 1 . These were zero-filled to obtain a two-dimensional matrix of 1024 ð 1024 points. The time increments used were 0.000 112 s with a sweep width of 4464 Hz in double quantum filtered COSY experiment with TPPI as an internal standard. F 1 and F 2 processing were carried out with a sine square weighting function. A pulse angle of 90 ° ⊲13 μs⊳ and an acquisition time of 0.1147 s with a repetition time of 2.5 s were used. The number of transients was 8 and the digital resolution was calculated as 4.359. Nuclear Overhauser enhancements (NOE) were determined by the difference method using the low-intensity presaturation pulses of 5 s before each acquisition pulse. A sequence of eight scans with selected irradiation followed by eight scans with irradiation at a nearby blank position was repeated 12 times. The summed irradiated and blank free-induction decays were subtracted and transformed to give the difference spectra. RESULTS AND DISCUSSION The carbonyl stretching frequency, chemical shifts of hydrogens at the bridgeheads, carbonyl carbons and carbons ˛,˛ 0 to the carbonyl of Table 1. Proton chemical shifts (ppm) of 2,6-diaryl-4-piperidones Compound H-2 H-3 H-5 H-6 NH Aryl protons 1a 3.96 2.45 2.45 3.96 2.05 7.30 1b 3.95 2.50 2.50 3.95 1.95 7.25 1c 3.55 3.75 3.75 3.55 1.05 7.30 1d 3.95 2.60 2.60 3.95 - 7.35 1e 3.35 2.65 2.65 3.35 - 7.25 Series 1 Series 2 Series 3 v CDO v CDO v CDO Compound R R 0 X ⊲cm 1 ⊳ Compound Ar R a X b ⊲cm 1 ⊳ Compound Ar R a ⊲cm 1 ⊳ 1a H H NH 1705 2a C 6 H 5 H NH 1714 3a C 6 H 5 H 1698 1b CH 3 H NH 1703 2b 4-CH 3 C 6 H 4 H NH 1723 3b 4-CH 3 C 6 H 4 H 1701 1c CH 3 CH 3 NH 1704 2c 4-OCH 3 C 6 H 4 H NH 1712 3c 4-OCH 3 C 6 H 4 H 1701 1d H H NCH 3 1705 2d C 6 H 5 CH 3 NH 1711 3d 4-ClC 6 H 4 H 1702 1e CH 3 H NCH 3 1705 2e 3,5-⊲CH 3 ⊳ 2 C 6 H 3 H NH 1710 3e C 6 H 5 H 1698 2f 3,5-⊲CH 3 ⊳ 2 C 6 H 3 H NH 1710 3f 3,5-⊲CH 3 ⊳ 2 C 6 H 3 H 1698 2g 3,5-⊲CH 3 ⊳ 2 C 6 H 3 H NH 1710 2h 4-CH 3 C 6 H 4 H NH 1720 2i 4-CH 3 C 6 H 4 H NCH 3 1718 a R D R 0 in all cases except 2d, where R D Me, R 0 D H. b X D X 0 in all cases expect 2f and 2i, where X D NMe, X 0 D NH. Copyright  2001 John Wiley & Sons, Ltd.