Pauson–Khand reactions of functionalized allenes with different alkynes give cyclopentenones with generally high regio- and stereoselectivities. The allenes react through their external double bonds, giving cyclopentenones with exocyclic double bond at their β positions and predominantly with E stereochemistry. Some intramolecularreactions with allenynes connected through aromatic rings are described
具有不同炔烃的官能化丙二烯的 Pauson-Khand 反应产生具有通常高区域选择性和立体选择性的环戊烯酮。丙二烯通过它们的外部双键反应,得到在其 β 位置具有环外双键的环戊烯酮,主要是 E 立体化学。描述了通过芳环连接的丙炔的一些分子内反应。这些以中等至良好的产率得到相应的杂环。
Transition‐Metal‐Free Stereoselective Borylation of Allenamides
作者:Lorena García、Jana Sendra、Núria Miralles、Efraim Reyes、Jorge J. Carbó、Jose L. Vicario、Elena Fernández
DOI:10.1002/chem.201803004
日期:2018.9.20
Complete stereocontrol on the transition‐metal‐free hydroboration of the distal double bond of allenamides could be achieved when allenamides contained acetyl substituents, which provided exclusively the Z‐isomer. The consecutive Pd‐catalyzed cross‐coupling reaction allowed the straightforward formation of trisubstituted enamides, with total control of the stereoselectivity.
IntermolecularPauson–Khandreactions are still quite limited in scope and yields. There are also few reports using allenes as the olefinic part in this version. We report herein new regio and stereoselective reactions of allenamides with several alkynes. These reactions give functionalized cyclopentenones bearing an exocyclic enamide, which can be useful synthetic intermediates.