Henry reaction catalyzed by new series of imidazolidine-4-one Cu-complexes

Evaluation of the enantioselectivity of new chiral ligands based on imidazolidin-4-one derivatives

The new chiral ligands I-III based on derivatives of imidazolidin-4-one were synthesised and characterised. The catalytic activity and enantioselectivity of their corresponding copper(II) complexes were studied in asymmetric Henry reactions. It was found that the enantioselectivity of these catalysts is overall very high and depends on the relative configuration of the ligand used; cis-configuration of ligand affords the nitroaldols with major enantiomer S- (up to 97% ee), whereas the application of ligands with trans-configuration led to nitroaldols with major R-enantiomer (up to 96% ee). The "proline-type" ligand IV was also tested in asymmetric aldol reactions. Under the optimised reaction conditions, aldol products with enantioselectivities of up to 91% ee were obtained.

The asymmetric Henry reaction as synthetic tool for the preparation of the drugs linezolid and rivaroxaban

The human drugs – the antibiotic linezolid (1) and the anticoagulant rivaroxaban (2) – belong among modern pharmaceutics, which contain an oxazolidine-2-one moiety bearing a stereogenic center. The chirality of these drugs is a fundamental attribute for their biological activity. Herein, one of the efficient asymmetric syntheses of these drugs was studied in detail. Highly enantioselective catalysts were tested in the key step of the synthetic procedure, i.e., the asymmetric Henry reaction, under different reaction conditions, using several starting aldehydes. The corresponding nitroaldols as chiral intermediates in the syntheses of these drugs were obtained in high yields and enantiomeric excesses of up to 91% ee.

Synthesis and Catalytic Application of Two Mononuclear Complexes Bearing Diethylenetriamine Derivative Ligand

Two mononuclear zero-dimensional Ni(II) and Zn(II) complexes bearing diethylenetriamine derivative ligand, namely [NiL(CH₃COO)₂(H₂O)] (1) and [ZnL(CH₃COO)₂] (2) [L = N, N'-bis(2-hydroxybenzyl)diethylenetriamine], were synthesized under reflux conditions. The molecular composition and structure of the complexes were identified by IR, PXRD, elemental analyses, and single crystal X-ray diffraction. Complex 1 belongs to a monoclinic crystal system with the P2₁/n space group, and Complex 2 belongs to a monoclinic crystal system with the C2/c space group. The Henry reaction of nitromethane with aromatic aldehydes was explored with Complexes 1 and 2 as the catalyst. Results from the catalytic reaction revealed that the complexes displayed excellent catalytic activities under the optimized conditions and that the substrate scope of aromatic aldehydes could be extended to a certain extent. In addition, the possible catalytic mechanism of the Henry reaction was also deduced.

Tricyclic Imidazolidin-4-ones by Witkop Oxidation of Tetrahydro-β-carbolines

1-Substituted and 1,1-disubstituted tetrahydro-β-carbolines undergo sodium periodate oxidative ring expansion in the presence of formaldehyde and other aldehydes to form 5,6-dihydro-7H-1,4-methanobenzo[e][1,4]diazonine-2,7(3H)-diones in 30-81% yield. In most cases, the reaction to form this new 6/8/5-tricyclic ring system proceeds with high diastereoselectivity. These benzannulated medium-ring keto imidazolidin-4-ones expand the menu of tetrahydro-β-carboline oxidation products.

A NbO type Cu(ii) metal-organic framework showing efficient catalytic activity in the Friedländer and Henry reactions

A three-dimensional NbO type porous metal-organic framework 1 containing both tertiary amine groups and paddle wheel dinuclear Cu₂(COO)₄ secondary building units as the active centre was synthesized at room temperature. The activated framework 1' can be used as an efficient heterogeneous catalyst for the synthesis of quinoline derivatives by the Friedländer reaction and for the synthesis of β-nitroalcohols by the Henry (nitroaldol) reaction. This MOF-based heterogeneous catalyst is easily recycled and reused further without losing its structural integrity and catalytic activity.