The effect of the nitrogen non-bonding electron pair on the NMR and X-ray in 1,3-diazaheterocycles

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• 作者：Cesar Garcí ; as-Morales ; Selene H. Martí ; nez-Salas ; Armando Ariza-Castolo ; ^{aariza@cinvestav.mx}
• 关键词：Stereoelectronic effect ; Nonbonding electron pair ; Spin&ndash ; spin coupling constant ; X-ray structure ; Homohyperconjugation
• 刊名：Tetrahedron Letters
• 出版年：2012
• 期刊代码：109_00404039
• 类别：ch
• 出版时间：27 June, 2012
• 卷：53
• 期：26
• 页码：3310-3315
• 文件大小：598 K

摘要

The effect of the nitrogen nonbonding electron pair on the ¹J_C,H values of 1,3-diazaheterocycles was analyzed and compared to 1,5-diazabiciclo[3.2.1]octanes, which have a restricted conformation. The ¹J_C,H values were measured by observing the ¹³C satellites in the ¹H NMR spectra and then determining the ¹H-coupled ¹³C NMR spectra. The ¹J_C,H values are 10 Hz larger when the 伪-hydrogen is synperiplanar rather than antiperiplanar to the nonbonding electron pair on the nitrogen, which serves as experimental evidence of the orbital n_N鈫捪?sup>鈭?/sup>_C,Hap interactions. In addition, the homoanomeric effect from the interactions of the nitrogen lone pair with the antibonding orbital of the equatorial hydrogen, which was in the 尾 position, was discussed (n_N鈫捪?sup>鈭?/sup>_C(尾),Heq).