An asymmetric, phase-transfer-catalyzed vinylogous conjugate addition–vinylogous cyclization cascade of olefinic azlactones with 4-nitro-5-styrylisoxazoles is reported. In the presence of an l-tert-leucine-derived urea–quaternary ammonium salt as a bifunctional phase-transfer catalyst and KF, two series of valuable optically pure cyclohexenones featuring two and three stereocenters were obtained in
Manrao; Sharma; Dhir, Journal of the Indian Chemical Society, 1982, vol. 59, # 7, p. 901 - 902
作者:Manrao、Sharma、Dhir、Kalsi
DOI:——
日期:——
A Simple and Convenient Synthesis of 4-Ylidene-5(4<i>H</i>)oxazolone Derivatives: Oxazolone Ring Transformation Leading to Other Heterocyclic Structures
作者:Ramadan M. Abdel-Motaleb、Hadeer M. Bakeer、Gammal H. Tamam、Wael A. A. Arafa
DOI:10.1002/jhet.938
日期:2012.9
yield synthetic procedure for the synthesis of 4‐ylidene‐5(4H)‐oxazolones 2a–m from arylidene‐malononitriles under solvent‐free conditions is described. The scope of this reaction was investigated, and it was found that the presence of anhydrous sodium acetate gave the corresponding oxazolones in excellent yields. The newly generated oxazolone derivative 2m underwent ring transformation into pyrroles,
Organocatalytic Asymmetric Hetero-Diels–Alder Reaction of in Situ Generated Dienes: Access to α,β-Unsaturated δ-Lactones Featuring CF<sub>3</sub>-Substituted Quaternary Stereocenter
作者:Harshit Joshi、Ankit Yadav、Arko Das、Vinod K. Singh
DOI:10.1021/acs.joc.9b03076
日期:2020.3.6
Chiral bifunctional urea-catalyzed asymmetric direct hetero-Diels-Alderreaction between alkylidene azlactone-derived dienes and trifluoromethyl aryl ketones is reported for the first time. The direct hetero-Diels-Alderreaction followed by ring opening results in densely functionalized α,β-unsaturated δ-lactones featuring a CF3-substituted quaternary stereocenter in high yields with excellent enantioselectivities