Chiral Dinuclear Research Articles

Chiral Dinuclear Benzyliminobinaphthoxy‐Palladium Catalyst for Asymmetric Mannich Reaction of Aldimines and Isatin‐Derived Ketimines with Alkylmalononitriles

AbstractA newly developed dinuclear bis(benzylimino)binaphthol (BIB)−Pd complex showed good catalytic activity for the Mannich reaction of aldimines and isatin‐derived ketimines with alkylmalononitriles to give the products in a highly enantioselective manner.magnified image

Structural Investigation into the Threading Intercalation of a Chiral Dinuclear Ruthenium(II) Polypyridyl Complex through a B-DNA Oligonucleotide.

Herein we report the separation of the three stereoisomers of the DNA light-switch compound [{Ru(bpy)2}2(tpphz)]4+ (tpphz = tetrapyrido[3,2-a:2',3'-c:3″,2″-h:2‴,3‴-j]phenazine) by column chromatography and the characterization of each stereoisomer by X-ray crystallography. The interaction of these compounds with a DNA octanucleotide d(GCATATCG).d(CGATATGC) has been studied using NMR techniques. Selective deuteration of the bipyridyl rings was needed to provide sufficient spectral resolution to characterize structures. NMR-derived structures for these complexes show a threading intercalation binding mode with slow and chirality-dependent rates. This represents the first solution structure of an intercalated bis-ruthenium ligand. Intriguingly, we find that the binding site selectivity is dependent on the nature of the stereoisomer employed, with Λ RuII centers showing a better intercalation fit.

Chiral Dinuclear Vanadium Complex-Mediated Oxidative Coupling of Resorcinols.

A method for the highly regio- and enantioselective oxidative coupling of resorcinols has been established by using dibrominated dinuclear vanadium(V) catalyst 1c under air. When resorcinols bearing an aryl substituent were applied as substrates to the coupling, axially chiral biresorcinols were obtained as single regioisomers in high yield with up to 98% ee.

Catalytic Asymmetric Nazarov Cyclization of Heteroaryl Vinyl Ketones through a Crystallographically Defined Chiral Dinuclear Nickel Complex.

A Ni(NTf2)2 and tetradentate bisimino-bisquinoline ligand complex catalyzed the enantioselective Nazarov cyclization of heteroaryl vinyl ketones. An X-ray-quality crystal was obtained from a mixture of the Ni complex and the substrate, which was the dinuclear chiral Ni complex. From information regarding the structure of the complex, the substrate was distorted to form a helical shape, and the carbon atoms involved in bond formation were close to each other. In addition, mechanistic studies revealed that the configuration of the olefin moiety was isomerized before bond formation.

ChemInform Abstract: Enantioselective and Aerobic Oxidative Coupling of 2‐Naphthol Derivatives Using Chiral Dinuclear Vanadium(V) Complex in Water.

Abstract The enantioselective oxidative coupling of 2-naphthols in water was established using dinuclear vanadium(V/IV) catalysis with O2 as the sole co-oxidant. In the vanadium-catalyzed reaction, the corresponding coupling products were obtained in good to excellent yields with up to 94% enantiomeric excess. In water, racemization of the coupling product was suppressed even at high temperature (70 °C).

ChemInform Abstract: Asymmetric Henry Reaction Catalyzed by a Chiral Dinuclear Nickel Complex.

AbstractThe synthesis of the ligand is described as well as the preparation of three derivatives thereof all providing significantly lower yields and enantioselectivities.

Asymmetric Henry Reaction Catalyzed by a Chiral Dinuclear Nickel Complex

Several chiral polyfunctional ligands were conveniently synthesized from l -amino acids and used to prepare the dinuclear complex in situ. A novel bimetallic catalyst containing dinuclear nickel was developed and applied to the asymmetric Henry reaction. With the assistance of N-methylmorpholine, good enantio­selectivities (up to 91% ee) and moderate yields (up to 72%) were obtained for aryl, heteroaryl, and aliphatic aldehydes. The pathway was air tolerant and easily manipulated, and the reagents were readily available.

Syntheses, crystal structures, circular dichroism, and magnetic properties of chiral dinuclear and polymeric nickel(II) compounds

Chiral dinuclear nickel(II) complexes, [Ni(LR,R)(C2O4)Ni(LR,R)](ClO4)2·4CH3CN (3) and [Ni(LS,S)(C2O4)Ni(LS,S)](ClO4)2·4CH3CN (4) and chiral polymeric compounds, [Ni(LR,R)(CrO4)]n·2H2O·CH3CN (5) and [Ni(LS,S)(CrO4)]n·2H2O·CH3CN (6) have been synthesized and characterized (LR,R/S,S=1,8-di((R/S)-α-methylbenzyl)-1,3,6,8,10,13-hexaazacyclotetradecane). These chiral compounds were characterized by X-ray crystallography, circular dichroism, and molecular magnetism. The nickel(II) ions in 3 and 4 have a distorted octahedral geometry by coordination with four nitrogens of a macrocyclic ligand with chiral pendents in a folded conformation and two oxygens of an oxalate ion in the cis positions. The nickel(II) ions in 5 and 6 have a distorted octahedral geometry by coordination with four nitrogens of a macrocyclic ligand in a planar conformation and two oxygens of two chromate ions in the axial positions. Complexes 3 and 4 show strong antiferromagnetic interactions [3: g=2.36, J/kB=−29.9K (−20.8cm−1); 4: g=2.18, J/kB=−25.5K (−17.7cm−1)], while 5 and 6 exhibit weak antiferromagnetic couplings [5: g=2.25, J/kB=−1.20K (−0.83cm−1); 6: g=2.25, J/kB=−0.68K (−0.47cm−1)]. The former complexes occur strong antiferromagnetic interactions via the oxalato bridges within the nickel(II) dimers, the latter compounds are weak antiferromagnetic interactions through the chromate ions within the 1D polymers. The circular dichroism (CD) spectrum of 3 has exhibited two negative peaks at 336 and 533nm, and that of 4 has displayed an enantiomeric pattern. The CD spectrum of 5 has appeared a negative absorption above ca. 550nm, while that of 6 has shown an enantiomeric pattern in the same wavelength region.

ChemInform Abstract: Chiral Dinuclear Phthalazine‐Bridged Bisoxazoline Ligands: Synthesis and Application in Enantioselective Cu‐Catalyzed Conjugate Addition of ZnEt2 to Enones.

AbstractA novel class of ligands, represented by PBO, is developed and successfully applied to the title reaction.

Chiral dinuclear phthalazine bridged bisoxazoline ligands: synthesis and application in enantioselective Cu-catalyzed conjugate addition of ZnEt2 to enones

A new class of chiral dinuclear ligands with phthalazine bridged bisoxazoline scaffold was designed and prepared in convenient synthetic routes. 1H NMR analysis showed that this class of ligands could coordinate with two metal ions, either same or different. These ligands afforded good to excellent yields and enantioselectivities in Cu-catalyzed conjugate addition of ZnEt2 to enones.

ChemInform Abstract: Chiral Dinuclear Vanadium(V) Catalysts for Oxidative Coupling of 2‐Naphthols.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis and Structure of Chiral Dinuclear Copper(II) Complex of Novel Structurally Reinforced Hexaazamacrocyclic Ligand

Abstract A structurally reinforced chiral 18-membered azamacrocycle (2S,8S,11S, 17S)-2,8,11,17-tetraisobutyl-1,4,7,10,13,16 -hexaazatricyclo[14.2.2.27,10]docosane as a new type of ligand was conveniently synthesized by BH3 reduction from the corresponding constrained macrocyclic pseudopeptide cyclo[(2S,3′S)-2-(3′-isobutyl-2′-oxo-piperazine-1′-yl)-4-methyl-pentanoyl-glycyl]2. Its dicopper(II) complexes were prepared and characterized.