1,3-dipolar cycloadditions of 3,4,5,6-tetrahydropyridine 1-oxide to α,β-unsaturated lactones: stereochemical assignment and conformational analysis of the products
作者:Pau Cid、Pedro de March、Marta Figueredo、Josep Font、Sergio Milán、Ángeles Soria、Albert Virgili
DOI:10.1016/s0040-4020(01)90237-6
日期:1993.4
obtained heterocyclic compounds, an accurate conformational analysis has been performed. Important differences in their conformational behavior in solution have been found as a function of the lactone ring size and the presence or absence of a carbonyl group. This study points out the existence of an attractive interaction between the nitrogen lone electron pair and a carbonyl group at a fitting distance
我们已经调查硝酮的1,3-偶极环加成1至七,六,五元α,β不饱和内酯类(2,3,和4-6)和2,5-二氢呋喃,18。在所有这些反应中,exo加合物可以作为主要或独家产品获得。为了阐明所获得的杂环化合物的立体化学,已经进行了准确的构象分析。已经发现它们在溶液中的构象行为的重要差异是内酯环大小和羰基存在与否的函数。本研究指出的氮孤电子对和羰基之间的吸引相互作用的存在在嵌合距离,其诱导对于偏好顺式型的融合Ë在furanonic外型加成物(10,12,13,15,和16)。在所有的其它情况下,该距离过长(7,8,9,11,14)或无羰基存在的分子(在20),该反式invertomers占优势。