Preparation of oxazolines and oxazoles<i>via</i>a PhI(OAc)<sub>2</sub>-promoted cyclization of<i>N</i>-propargylamides
作者:Wei Yi、Qing-Yun Liu、Xing-Xiao Fang、Sheng-Chun Lou、Gong-Qing Liu
DOI:10.1039/c8ob01474d
日期:——
A metal-free cyclization of N-propargylamides for the synthesis of various oxazolines and oxazoles via a 5-exo-dig process is presented. Using (diacetoxyiodo)benzene (PIDA) as a reaction promoter and lithium iodide (LiI) as an iodine source, intramolecular iodooxygenation of N-propargylamides proceeded readily, leading to the corresponding (E)-5-iodomethylene-2-oxazolines in good to excellent isolated
Selenium-π-Acid Catalyzed Oxidative Functionalization of Alkynes: Facile Access to Ynones and Multisubstituted Oxazoles
作者:Lihao Liao、Hang Zhang、Xiaodan Zhao
DOI:10.1021/acscatal.8b01595
日期:2018.7.6
Unprecedented selenium-catalyzed propargylic oxidation of alkynes is disclosed. Various propargylphosphonates and 3-alkynoates were efficiently converted to valuable ynones via unusual C–C triple bond migration and deselenenylation at a vinyl carbon. By the strategies of tautomerization of enamine intermediate and SN2 displacement, similar conditions were effective for the oxidative difunctionalization
公开了前所未有的硒催化炔烃的炔丙基氧化。各种炔丙基膦酸酯和3-链烷酸酯通过不寻常的CC三键迁移和乙烯基碳上的硒烯基化反应,有效地转化为有价值的炔酮。通过烯胺中间体的互变异构和S N 2置换的策略,相似的条件对于乙酰胺的氧化双官能化有效,从而提供了具有高区域选择性的多取代恶唑。机理研究揭示了这些详细的过程。
Intramolecular Pd(II)-Catalyzed Cyclization of Propargylamides: Straightforward Synthesis of 5-Oxazolecarbaldehydes
作者:Egle M. Beccalli、Elena Borsini、Gianluigi Broggini、Giovanni Palmisano、Silvia Sottocornola
DOI:10.1021/jo800621n
日期:2008.6.1
Direct synthesis of 2-substituted 5-oxazolecarbaldehydes was performed by intramolecular reaction of propargylamides through treatment with a catalytic amount of Pd(II) salts in the presence of a stoichiometric amount of reoxidant agent. The heterocyclization process was well-tolerated by a wide range of aryl, heteroaryl, and alkyl propargylamides. This protocol constitutes a valuable synthetic pathway to 5-oxazolecarbaldehydes, alternative to the formylation on oxazole rings, often unsatisfactory in term of regioselectivity and yields.