A reusable enantioselective catalytic system for the Kharasch–Sosnovsky allylic oxidation of alkenes based on a ditopic azabis(oxazoline) ligand

Polytopic Bis(oxazoline)‐Based Ligands for the Development of Recoverable Catalytic Systems Applied to the Cyclopropanation Reaction

“…1 H NMR DOSY [26,27] experiments had been carried out using Cu I and Zn II complexes of iPrDAX and similar DOSY experiments have been successfully applied to the study of the size of molecular aggregates, metal-ligand complexes, and metallosupramolecular architectures in solution. [15] To collect more information on the copper coordination polymers, analyses were conducted using high-resolution mass spectrometry (HRMS). When the Zn/2b ratio was adjusted to 1:1 (the ideal stoichiometry for formation of a coordination polymer), minimized diffusion coefficients were observed indicating the presence of oligomeric species.…”

“…These ligands were applied to the preparation of copper coordination polymers in order to promote a diversity of organic reactions in an enantioselective way, such as cyclopropanation of alkenes with ethyl diazoacetate, [12,13] Henry or nitroaldol reactions, [14] and Kharasch-Sosnovsky allylic oxidation of cycloalkenes with peroxo esters. [15,16] The application of a release-capture strategy allowed selective precipitation of the polymers after reaction completion and product extraction by use of a non-coordinating solvent. The polymer could then be recovered and reused in subsequent reactions with good results.…”

Polytopic bis(oxazoline)-based ligands for recoverable catalytic systems applied to the enantioselective Henry reaction

“…Our research group and others have described the application of the release-and-capture strategy using coordination polymers of bis(oxazoline)-based polytopic ligands to a variety of organic reactions, such as the cyclopropanation reaction between styrene and ethyl diazoacetate, [18][19][20] the allylic oxidation of cycloalkenes with tert-butyl perbenzoate, 21 the α-hydrazination of β-ketoesters, 22 or the nitroaldolic Henry reaction between aldehydes and nitro derivatives. 23,24 Concerning the latter, only two ditopic ligands were tested in our former work.…”

Asymmetric cyclopropanation in ionic liquids promoted by dicopper complexes of ditopic ligands

“…These ligands have been applied to the preparation of copper coordination polymers in order to promote several organic reactions, such as cyclopropanation of alkenes with ethyl diazoacetate, [15][16][17] nitroaldol (Henry) reaction, 18 and allylic oxidation of cycloalkenes with peroxoesters. 19,20 In all cases the catalyst can be recovered following a release-and-capture strategy, since the coordination 3 polymer, which is disassembled in the reaction media, can be precipitated after the reaction end, and then easily separated from reagents and reaction products by decantation. These kinds of ditopic chiral ligands offer a third option to minimise ligand leaching from IL phases, namely the use double metal-ligand complexes as catalysts.…”