Santiago Marcelina, Low Eddy, Chambournier Gilles, Gawley Robert E
Department of Chemistry, University of Miami, Coral Gables, Florida 33124, USA.
J Org Chem. 2003 Oct 31;68(22):8480-4. doi: 10.1021/jo034948y.
The solution conformation of N-methyl-2-(tributylstannyl)piperidines has been determined through the use of vicinal 119Sn-13C coupling constants, revealing a conformational distortion caused by an unexpected stereoelectronic effect in some cases. Specifically, the "equatorial" conformer is distorted into a half-chair, in which the nitrogen lone pair eclipses the C-Sn bond. This distortion, which "costs" approximately 1 kcal/mol, correlates with a conformational dependence of geminal 119Sn-15N couplings and a possible correlation with reactivity in the tin-lithium exchange reaction.
通过使用邻位119Sn-13C偶合常数确定了N-甲基-2-(三丁基锡烷基)哌啶的溶液构象，结果表明在某些情况下存在由意外的立体电子效应引起的构象畸变。具体而言，“赤道”构象异构体扭曲成半椅式，其中氮孤对与C-Sn键重叠。这种畸变“代价”约为1千卡/摩尔，与偕位119Sn-15N偶合的构象依赖性相关，并且可能与锡-锂交换反应中的反应性相关。
