A reusable enantioselective catalytic system for the Kharasch–Sosnovsky allylic oxidation of alkenes based on a ditopic azabis(oxazoline) ligand
摘要:
An easily recoverable and reusable enantioselective catalytic system based on the self-assembly of a coordination polymer through the use of a chiral ditopic ligand, is described for the allylic oxidation of cycloalkenes with tert-butyl perbenzoate. Upon addition of the substrates and a coordinating solvent (acetone or acetonitrile) the coordination polymer disassembles, allowing the catalysis to take place in homogeneous phase. After completion of the reaction, the catalyst reassembles as a coordination polymer upon solvent evaporation and addition of hexane, and is recovered as an insoluble solid. This way, good enantioselectivities and yields are obtained in seven consecutive operation cycles. (C) 2011 Elsevier Ltd. All rights reserved.
Polytopic Oxazoline-Based Chiral Ligands for Cyclopropanation Reactions: A New Strategy to Prepare Highly Recyclable Catalysts
作者:José I. García、Clara I. Herrerías、Beatriz López-Sánchez、José A. Mayoral、Oliver Reiser
DOI:10.1002/adsc.201100213
日期:2011.10
Newpolytopicchiral copper complexes based on azabis(oxazoline) moieties have been synthesized and applied in cyclopropanationreactions of several alkenes. Excellent enantioselectivities have been obtained in all cases and additionally, the catalysts have been recovered in up to 14 cycles without noticeable loss of activity and selectivity. Analysis of the copper complexes by mass spectrometry suggests
Asymmetric cyclopropanation in ionic liquids promoted by dicopper complexes of ditopic ligands
作者:José I. García、Clara I. Herrerías、Beatriz López-Sánchez、José A. Mayoral、Ana C. Miñana
DOI:10.1016/j.tetasy.2014.04.017
日期:2014.5
complexes of ditopic chiral ligands bearing bis(oxazoline) moieties has been explored in the enantioselective cyclopropanationreaction of styrene with ethyl diazoacetate. The recoverability of these catalytic phases has been studied using different ionic liquids and ligands. The origin of the ionic liquid is determinant both for the catalytic results and the reusability of the system.