Highly Diastereo- and Enantioselective Aziridination of ,-Unsaturated Amides with Diaziridine and Mechanistic Consideration on Its Stereochemistry
作者:Hiroyuki Ishihara、Kiyoto Hori、Hiroyasu Sugihara、Yoshio N. Ito、Tsutomu Katsuki
DOI:10.1002/hlca.200290012
日期:2002.12
though the yield was low (4%). This aziridination was considered to proceed stepwise by way of the enolate intermediate (Scheme 2). Careful inspection of the stereochemistry and its solvent-dependence suggested that the diastereoselection of the reaction was kinetically controlled: the 1,4-addition of N-lithiated diaziridine was a crucial step for determination of the stereochemical course of the
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