Aridoss G, Balasubramanian S, Parthiban P, Kabilan S
Department of Chemistry, Annamalai University, Annamalainagar 608002, Tamil Nadu, India.
Spectrochim Acta A Mol Biomol Spectrosc. 2007 Dec 31;68(5):1153-63. doi: 10.1016/j.saa.2007.01.013. Epub 2007 Jan 20.
A series of 2,6-diarylpiperidin-4-ones having electron withdrawing chloroacetyl group at the heterocyclic nitrogen were synthesized. Unambiguous characterizations of the synthesized compounds were achieved by one-dimensional ((1)H NMR and (13)C NMR) and two-dimensional (HOMOCOSY, NOESY and HSQC spectra for compounds 8 and 9 and HOMOCOSY spectrum only for 10) NMR spectroscopic data. The conformational preferences of N-chloroacetyl-2,6-diarylpiperidin-4-ones with and without alkyl substituent at C-3 and C-5 (8-14) have also been discussed using the spectral studies. The spectral data and extracted coupling constant values suggest that the compounds 8, 12 and 14 adopt flattened boat conformation whereas the remaining compounds exist in twist-boat conformations in solution with coplanar orientation of the chloroacetyl moiety present at the heterocyclic nitrogen. The substituent parameters for the chloroacetyl moiety on the heterocyclic ring carbons have also been derived and discussed elaborately on the basis of their steric, electronic and gamma-eclipsing interaction. This substituent at the nitrogen causes a substantial change on the chemical shifts of ring carbons and the associated protons.
合成了一系列在杂环氮上带有吸电子氯乙酰基的2,6 - 二芳基哌啶 - 4 - 酮。通过一维（(1)H NMR和(13)C NMR）和二维（化合物8和9的HOMOCOSY、NOESY和HSQC谱，化合物10仅HOMOCOSY谱）核磁共振光谱数据对合成的化合物进行了明确的表征。还利用光谱研究讨论了在C - 3和C - 5处有或没有烷基取代基的N - 氯乙酰基 - 2,6 - 二芳基哌啶 - 4 - 酮（8 - 14）的构象偏好。光谱数据和提取的耦合常数表明，化合物8、12和14采用扁平船式构象，而其余化合物在溶液中以扭曲船式构象存在，杂环氮上的氯乙酰基部分共面。还推导了杂环环碳上氯乙酰基部分的取代基参数，并基于其空间、电子和γ - 重叠相互作用进行了详细讨论。氮上的这个取代基导致环碳及其相关质子的化学位移发生显著变化。
