在研究α,β-不饱和酰胺与二氮丙啶的叠氮化过程中,我们发现可以通过选择适当取代的二氮丙啶来制备顺式和反式-氮丙啶羧酰胺。尽管3-单取代的重氮丙啶2适用于反式选择性叠氮化,但3,3-二烷基重氮丙啶1的使用导致形成顺式氮丙啶羧酰胺,而与底物的几何结构无关(方案1和表1和表2)。为了阐明独特的非立体特异性并将这些叠氮基化扩展为不对称的,新制备了几种旋光性的二氮丙啶。与光学活性的3-单取代的重氮丙啶3-环己基-1-[(1 R -1)-苯乙基]二氮丙啶16的氮杂叠氮化反应平稳进行,具有高反选择性和出色的对映选择性(最高98%ee;参见表3)。另一方面,用旋光的3,3-二甲基-1-[((1R)-1-苯基乙基]二氮丙啶15 ]实现了高度对映选择性的顺式叠氮(> 99%ee),尽管收率很低(4%)。认为该叠氮化通过烯醇盐中间体逐步进行(方案2)。对立体化学及其溶剂依赖性的仔细检查表明,反应的非对映选择性是动力学控制的:N-锂化的二氮丙啶的1
Rapid access to cinnamamides and piper amides <i>via</i> three component coupling of arylaldehydes, amines, and Meldrum's acid
作者:Santanu Ghosh、Chandan K. Jana
DOI:10.1039/c9gc02937k
日期:——
A practical method for the synthesis of cinnamamides and piper amides via a conceptually novel three component reaction of aldehydes, amines and Meldrum's acid has been reported. The reaction proceeds under operationally simple conditions without the aid of coupling reagents, oxidants, or catalysts, which are essential for the preparation of cinnamamides/piper amides via known methods. The formation
Highly Diastereoselective Aziridination of<i>α,β</i>-Unsaturated Amides Using Diaziridine
作者:Hiroyuki Ishihara、Yoshio N. Ito、Tsutomu Katsuki
DOI:10.1246/cl.2001.984
日期:2001.10
Racemic 3-cyclohexyl-1-methyldiaziridine was found to react with α,β-unsaturated amides in basic conditions, giving N-unprotected trans-aziridines, while 3,3-pentamethylenediaziridine had been reported to afford cis-aziridines in high diastereoselectivity. The trans-selectivity was partially dependent on the stereochemistry of the substrate. The stereochemistries of these reactions were reasonably explained by the conformational analysis of the intermediary enolates.