吡啶酰胺类化合物中酰胺键异构化的变温核磁共振研究(英文)  

Isomerization of the Amide Bond in Piperidin Amides Studied by Variable-temperature NMR Spectroscopy

作　　者：乔瑞瑞[1] 孙静[1] 杨春晖[1] 肖强[1] 崔育新[1] 

机构地区：[1]北京大学药学院天然药物与仿生药物国家重点实验室,北京100083

出　　处：《波谱学杂志》2008年第3期307-314,共8页Chinese Journal of Magnetic Resonance

摘　　要：合成了一系列六氢吡啶酰胺化合物以研究酰胺键的双键性质.采用1H及13CNMR技术确证了不同取代的酰胺化合物中酰胺键的双键性质.进一步采用变温核磁共振技术对2-(3,5-dinitrophenyl)-1-(piperidin-1-yl)ethanone(化合物1)进行了1H及13CNMR研究.结果表明,在20℃(293 K)时,a,b及c,d上的氢和碳原子具有不同的化学位移,且距酰胺键越近,化学位移的差异越大.随着温度的升高,两种异构体的转换速率增加,酰胺双键的性质越来越不明显,导致化学位移的差异逐渐减小,直至融合为一个峰.经计算,在融合温度下两种异构体的相互转换的速率常数是380s-1,能垒约为67kJ·mol-1.A series of amides of piperidin were synthesized and used for studies on the partial double-bond feature of the amide bonds. ^1 H and ^13 C NMR spectra of 2-（3, 5-dinitrophenyt）-l- （piperidin-l-yl） ethanone （compound 1） were acquired at various temperatures. The results showed that the C-N bond of the piperidin amides exhibited partially double-bond character at 20 ~C （293 K） , suggesting that the chemical shifts of a and b, c and d in compound 1 were very different due to the two rotameric states. With increasing temperature, the two peaks of non-equivalent -CH2- groups collapsed into one peak due to the fast rotation of the C-N bond. The rate constant for the dynamic process detected for compound 1 was 380 s 1 , and the free energy of activation for compound 1 at coalescence temperature （343 K） was 67 kJ·mo1^-1.

关 键 词：核磁共振 变温核磁 酰胺键 异构体 

分 类 号：O641[理学—物理化学]