Comparison of yttrium binaphthylamido alkyl and amide complexes for enantioselective intramolecular hydroamination

A chiral trisamido yttrium complex Y[(R)-C₂₀H₁₂(NC₅H₉)₂][NiPr₂][THF]₂·LiCl coordinated by N-cyclopentyl binaphthylamine ligand has been prepared in situ and characterised by NMR spectroscopy. It has been revealed as an efficient catalyst for intramolecular hydroamination of aminoolefins. Comparison with neutral alkyl, ate alkyl or ate tetraamido complexes coordinated by the same ligand indicated that this complex was the most efficient catalyst of the series for its both activity and enantioselectivity values.     

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π-Stacking interactions at the service of [Cu]-bis(oxazoline) recycling

Anthracene- and pyrene-tagged bis(oxazoline) ligands have been prepared and immobilized on charcoal, fullerene, and single-walled carbon nanotubes through π–π interactions. The corresponding copper complexes have been evaluated for their propensity to promote heterogeneous asymmetric Henry and ene reactions. The best results, in terms of activity, selectivity, and stability toward the recycling procedure have been obtained with the pyrene/SWCNT system, as the first example demonstrating the usefulness of such reversible interactions for the asymmetric formation of new C–C bonds.     

Recoverable salen-based macrocyclic chiral complexes; catalysts for enantioselective Henry reactions

Cobalt and chromium complexes have been prepared from chiral calix–salen cyclic ligands. The corresponding tetrahydrosalen reduced forms have been used for copper salt complexation. These new chiral catalysts have been tested for their ability to promote asymmetric Henry reactions between various aldehydes and nitromethane under heterogeneous conditions. The best results were obtained by using tetrahydrosalen-based copper macrocycles, in terms of activity, selectivity, and stability during the recycling process. Ten consecutive runs could indeed be performed with the same catalyst batch to produce the target 1-(2-methoxy-phenyl)-2-nitro-ethanol with highly stable values in terms of yield and enantioselectivity (up to 94% ee).     

High Pressure Fluorescence of 2,5-diphenyl-1,3,4-oxadiazole Crystals

The dependence of the fluorescence of 2,5-diphenyl-1,3,4-oxadiazole (DPO) crystals under compression up to 7 GPa was experimentally studied. The knowledge of the structural behavior at high pressure allows to relate the variation of the fluorescence to the diminution of the inter-molecular distance.