Sequential Metal-Free Thermal 1,3-Dipolar Cycloaddition of Unactivated Azomethine Ylides
作者:Verónica Selva、Elisabet Selva、Pedro Merino、Carmen Nájera、José M. Sansano
DOI:10.1021/acs.orglett.8b01292
日期:2018.6.15
The thermal 1,3-dipolar cycloaddition of unactivated azomethine ylides derived from allylamine and aromatic or heteroaromatic aldehydes with maleimides and 1,1- and 1,2-bis(phenylsulfonyl)ethylene affords endo-2,5-trans cycloadducts in moderate to good yields. DFT calculations provide evidence that the diastereoselectivity observed depends on the isomerization between S- and W-ylides according to Curtin-Hammett’s
烯丙基胺和芳族或杂芳族醛与马来酰亚胺,1,1-和1,2-双(苯磺酰基)乙烯的未活化偶氮甲亚胺基的热1,3-偶极环加成反应可中等至良好地得到内--2,5-反式环加合物产量。DFT计算提供了证据,证明根据Curtin-Hammett原理,观察到的非对映选择性取决于S和W烷基之间的异构化。DFT计算还解释了对于2-吡啶基和2-噻吩基衍生物观察到的不同的非对映异构体比率,其中由于异构化障碍和限速步骤(内酯形成障碍)之间的竞争性,不可能进行异构化。该方法应用于三环凝血酶抑制剂的非对映选择性合成。