Alcohol Ligands Research Articles

Silver(i) Perfluoroalcoholates: Synthesis, Structure, and their Use as Transfer Reagents.

Herein we report a general access to silver(i) perfluoroalcoholates, their structure in the solid state and in solution, and their use as transfer reagents. The silver(i) perfluoroalcoholates are prepared by the reaction of AgF with the corresponding perfluorinated carbonyl compounds in acetonitrile and are stable for a prolonged time at -18 °C. X-ray analysis of single crystals of perfluoroalcoholate species showed that two Ag(i) centers are bridged by the alcoholate ligands. In acetonitrile solution, Ag[OCF3] forms different structures as indicated by IR spectroscopy. Furthermore, the silver(i) perfluoroalcoholates can be used as easy-to-handle transfer reagents for the synthesis of Cu[OCF3], Cu[OC2F5], [PPh4][Au(CF3)3(OCF3)], and fluorinated alkyl ethers.

Synthesis and Application of a New Class of Planar and Centrally Chiral Ferrocenyl Amino Alcohol Ligands

AbstractA family of ferrocenyl amino alcohols (14 examples) has been prepared from the corresponding planar chiral ketones and evaluated as a new class of chiral ligands for asymmetric ethyl‐ and phenylzinc additions to aldehydes. The highly enantioselective synthesis of these ligands is facile, scalable, robust and relies on the use of cheaply available starting materials. Asymmetric ethyl additions proceeded smoothly at ambient temperature, with reaction times as short as 1 hour furnishing the desired products in up to 90 % yield and 99 % ee. The corresponding phenyl additions afforded products in up to 81 % yield and 88 % ee. The observed stereochemical outcome for the addition of diethylzinc was rationalized and the key proposed transition state was supported by an analysis of the X‐ray structures of a series of amino alcohol ligands.

Designing External Pores of Aluminum Oxo Polyhedrons for Efficient Iodine Capture.

Although metal-organic polyhedra (MOPs) expansion has been studied to date, it is still a rare occurrence for their porous intermolecular assembly for iodine capture. The major limitation is the lack of programmable and controllable methods for effectively constructing and utilizing the exterior cavities. Herein, the goal of programmable porous intermolecular assembly is realized in the first family of aluminum oxo polyhedrons (AlOPs) using ligands with directional H-bonding donor/acceptor pairs and auxiliary alcohols as structural regulation sites. The approach has the advantage of avoiding the use of expensive edge-directed ditopic and face-directed tritopic ligands in the general synthesis strategy of MOPs. Combining theoretical calculations and experiments, the intrinsic relationship is revealed between alcohol ligands and the growth mechanism of AlOPs. The maximum I2 uptake based on the mass gain during sorption corresponds to 2.35gg-1, representing the highest reported I2 sorption by an MOP. In addition, it can be easily regenerated and maintained the iodine sorption capacity, revealing its further potential application. This method of constructing stable and programmable porous materials will provide a new way to solve problems such as radionuclide capture.

Martin Silicates as Partners in Photoredox/Ni Dual Catalysis for the Installation of CH3, CH2D, CD2H, CD3and13CH3Groups onto (Hetero)Arenes

Martin Silicates as Partners in Photoredox/Ni Dual Catalysis for the Installation of CH₃, CH₂D, CD₂H, CD₃and¹³CH₃Groups onto (Hetero)Arenes

DNA interaction studies of a cobalt(III) complex containing β–amino alcohol ligand by spectroscopic and molecular docking methods

In the present research, the feasibility of a Cobalt(III) complex containing β–amino alcohol ligands for affinity with the target calf thymus DNA is demonstrated. In the title complex, [Co(C11H15N2O2)2]Cl, the Co(III) atom is six-coordinated with four N atoms and two O atoms from (2-[(E)-({2-[(2-Hydroxyethyl) amino]ethyl}imino)methyl]phenol) ligand (L). To investigate the molecular interaction between the synthesized complex and DNA, some multi-spectroscopic approaches associated with molecular docking were employed in the physiological buffer (pH 7.4). The results indicated that the Co(III) complex proved to be a minor groove binder with a preference for the A-T region, which was substantiated by displacement studies with Hoechst33258 and Methylene blue (MB) as minor groove binder and intercalator. In addition, the results of the molecular docking study revealed that the Co(III) complex approached the gap between the DNA minor grooves near the spot where the Hoechst was. Furthermore, the results of the cytotoxicity and apoptosis tests for the MCF-7 cell line were also indicative of the positive effects of the complex on controlling the growth and viability of breast cancer. Communicated by Ramaswamy H. Sarma

Regional segregation of chiral alcohol on polyoxotitanate cluster

The conformational analysis of peripheral ligands on the polyoxotitanate has drawn much less attention than its application in photocatalysis. In this study, a series of polyoxotitanate clusters with the same Ti6 kernels but different alcohol ligands have been synthesized and characterized. A systematic configurational analysis has revealed that when steric demanding enantiomeric alcohol ligands are confined within a narrow space as on the hexanuclear Ti6 clusters, they can achieve regional separation on different sides of the clusters.

Recoverable PEG-supported amino alcohol ligand for copper-catalyzed Enantio- and syn-selective henry reaction with nitroethanol: Sustainable and straightforward access to chiral syn-2-nitro-1,3-Diols

A poly(ethylene glycol) (PEG) supported amino alcohol has been developed as a chiral ligand to promote the copper-catalyzed asymmetric nitrolaldol reaction (Henry Reaction) with nitroethanol. The catalyst provides direct access to various syn-2-nitro-1,3-diols with high yields and stereoselectivities. The solubility of PEG moiety allows facile purification and recycling of the catalyst. The utility of the catalyst was further demonstrated by the gram-scale preparations of the key intermediates for florfenicol and reboxetine.

Enantioselective synthesis of α-aminoboronates by NiH-catalysed asymmetric hydroamidation of alkenyl boronates.

Chiral α-aminoboronic acids and their derivatives are generally useful as bioactive compounds and some have been approved as therapeutic agents. Here we report a NiH-catalysed asymmetric hydroamidation process that with a simple amino alcohol ligand can easily produce a wide range of highly enantioenriched α-aminoboronates from alkenyl boronates and dioxazolones under mild conditions. The reaction is proposed to proceed by an enantioselective hydrometallation followed by an inner-sphere nitrenoid transfer and C–N bond forming sequence. The synthetic utility of this transformation was demonstrated by the efficient synthesis of a current pharmaceutical agent, Vaborbactam.

Acetone Factor in the Design of Cu4-, Cu6-, and Cu9-Based Cage Coppersilsesquioxanes: Synthesis, Structural Features, and Catalytic Functionalization of Alkanes

The present study describes a new feature in the self-assembly of cagelike copperphenylsilsesquioxanes: the strong influence of acetone solvates on cage structure formation. By this simple approach, a series of novel tetra-, hexa-, or nonacoppersilsesquioxanes were isolated and characterized. In addition, several new complexes of Cu4 or Cu6 nuclearity bearing additional nitrogen-based ligands (ethylenediamine, 2,2'-bipyridine, phenanthroline, bathophenanthroline, or neocuproine) were produced. Single-crystal X-ray diffraction studies established molecular architectures of all of the synthesized products. Several coppersilsesquioxanes represent a novel feature of cagelike metallasilsesquioxane (CLMS) in terms of molecular topology. A Cu4-silsesquioxane complex with ethylenediamine (En) ligands was isolated via the unprecedented self-assembly of a partly condensed framework of silsesquioxane ligands, followed by the formation of a sandwich-like cage. Two prismatic Cu6 complexes represent the different conformers─regular and elliptical hexagonal prisms, "cylinders", determined by the different orientations of the coordinated acetone ligands ("shape-switch effect"). A heterometallic Cu4Na4-sandwich-like derivative represents the first example of a metallasilsesquioxane complex with diacetone alcohol ligands formed in situ due to acetone condensation reaction. As a selected example, the compound [(Ph6Si6O11)2Cu4En2]·(acetone)2 was explored in homogeneous oxidation catalysis. It catalyzes the oxidation of alkanes to alkyl hydroperoxides with hydrogen peroxide and the oxidation of alcohols to ketones with tert-butyl hydroperoxide. Radical species take part in the oxidation of alkanes. Besides, [(Ph6Si6O11)2Cu4En2]·(acetone)2 catalyzes the mild oxidative functionalization of gaseous alkanes (ethane, propane, n-butane, and i-butane). Two different model reactions were investigated: (1) the oxidation of gaseous alkanes with hydrogen peroxide to give a mixture of oxygenates (alcohols, ketones, or aldehydes) and (2) the carboxylation of Cn gaseous alkanes with carbon monoxide, water, and potassium peroxodisulfate to give Cn+1 carboxylic acids (main products), along with the corresponding Cn oxygenates. For these reactions, the effects of acid promoter, reaction time, and substrate scope were explored. As expected for free-radical-type reactions, the alkane reactivity follows the trend C2H6 < C3H8 < n-C4H10 < i-C4H10. The highest total product yields were observed in the carboxylation of i-butane (up to 61% based on i-C4H10). The product yields and catalyst turnover numbers (TONs) are remarkable, given an inertness of gaseous alkanes and very mild reaction conditions applied (low pressures, 50-60 °C temperatures).

New dinuclear cyanido complexes with amine alcohol ligand: synthesis, characterization and biotechnological application potential

New dinuclear cyanido complexes with amine alcohol ligand: synthesis, characterization and biotechnological application potential

Kinetic Resolution of dl-Hydrobenzoins Catalyzed by Copper(II) Complexes of C 2-Symmetric Thiophene-Derived Ligands

AbstractC 2-Symmetrical chiral amino alcohol ligands with a central thiophene moiety were shown to be effective in combination with CuCl2 for the asymmetric acylation of dl-hydrobenzoins. In contrast to previously developed chiral ligands, readily available acetyl chloride and acetic anhydride can be used as reagents, in addition to benzoyl chloride, giving rise to the corresponding monoacylated products in up to 99% ee (S = 532).

A relay catalysis strategy for enantioselective nickel-catalyzed migratory hydroarylation forming chiral α-aryl alkylboronates

A relay catalysis strategy for enantioselective nickel-catalyzed migratory hydroarylation forming chiral α-aryl alkylboronates

Evaluation of biological activities of cobalt(II) and copper(II) complexes synthesized from methylcarboxylate and amino alcohol ligand mixtures: spectroscopic, structural and docking studies

Two cobalt(II) and copper(II) complexes, [Co2(PDCA)(µ-PDCA)(H2O)5]·2H2O (1); H2PDCA: pyridine-2,6-dicarboxylic acid and [Cu(DEA)(PDCA)] (2); DEA: diethanolamine, were prepared from a mixed ligand amine/PDCA methyl ester mixture and identified by elemental analysis, FT-IR spectroscopy and single-crystal X-ray diffraction. X-ray structure analysis of 1 revealed a binuclear octahedrally coordinated cobalt(II) complex formed by bridging a PDCA2− between metal centers. In the mononuclear complex 2, the copper atom has an octahedral geometry with CuN2O4 environment formed by one DEA and one PDCA2– ligands in mer form. The ability of the H2PDCA and DEA ligands along with complexes 1 and 2 to interact with ten selected biomacromolecules (BRAF kinase, CatB, DNA gyrase, HDAC7, rHA, RNR, TrxR, TS, Top II and B-DNA) were investigated by docking studies. The results showed that the studied compounds can bind to DNA and proteins.

Effect of Polyvinyl Alcohol Ligands on Supported Gold Nano-Catalysts: Morphological and Kinetics Studies.

The effect of polyvinyl alcohol (PVA) stabilizers and gold nanoparticles supported on active carbon (AuNPs/AC) was investigated in this article. Polymers with different molecular weights and hydrolysis degrees have been synthesized and used, like the stabilizing agent of Au nano-catalysts obtained by the sol-immobilization method. The reduction of 4-nitrophenol with NaBH4 has been used as a model reaction to investigate the catalytic activity of synthesized Au/AC catalysts. In addition, we report several characterization techniques such as ultraviolet-visible spectroscopy (UV-Vis), dynamic light scattering (DLS), X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) in order to correlate the properties of the polymer with the metal nanoparticle size and the catalytic activity. A volcano plot was observed linking the catalytic performance with hydrolysis degree and the maximum of the curve was identified at a value of 60%. The Au:PVA-60 weight ratio was changed in order to explain how the amount of the polymer can influence catalytic properties. The effect of nitroaromatic ring substituents on the catalytic mechanism was examined by the Hammett theory. Moreover, the reusability of the catalyst was investigated, with little to no decrease in activity observed over five catalytic cycles. Morphological and kinetic studies reported in this paper reveal the effect of the PVA polymeric stabilizer properties on the size and catalytic activity of supported gold nanoparticles.

Intramolecular hydroamination of trisubstituted aminoallenes catalyzed by titanium complexes of diaryl substituted tridentate imine-diols

Our laboratory has developed catalysts based on earth abundant titanium for asymmetric reactions including intramolecular hydroamination. Previously, we showed that titanium complexes of imine diol ligands showed improved enantioselectivity relative to complexes with bidentate amino alcohol ligands. As the catalyst with the highest selectivity had di-tert-butyl substitution, we sought to increase the steric protection by preparing three new ligands with diaryl substitution. These ligands were readily prepared in two steps: first, synthesis of diaryl substituted salicylaldehydes by a Suzuki coupling and second, a Schiff base condensation with a chiral amino alcohol. After characterizing the ligands, in situ hydroamination/cyclization with 6-methyl-hepta-4,5-dienylamine was carried out at temperatures ranging from 105 °C to 135 °C to give exclusively 2-(2-methyl-propenyl)-pyrrolidine with enantioselectivity up to 22 %ee. Unexpected dimerization of the catalyst resulted in reduced activity, so the reaction required a catalyst loading of 10–20%.

Catalytic Asymmetric Addition of Diorganozinc Reagents to Pyrazole-4,5-Diones and Indoline-2,3-Diones.

The catalytic enantioselective diorganozinc additions to cyclic diketones including pyrazolin-4,5-diones and isatins have been developed. In the presence of morpholine-containing chiral amino alcohol ligand, the corresponding chiral cyclic tertiary alcohols were produced in good to excellent yields (up to 97 %) and enantioselectivities (up to 95 % ee). The notable feature of this protocol includes its mild reaction conditions, Lewis acid additives free and broad functional group tolerance.

Stereocontrolled radical polymerization of acrylamides by ligand-accelerated catalysis

The role of alcohol in the Yb(OTf)3- and Y(OTf)3-catalyzed stereoselective radical polymerization of acrylamides is clarified. The coordination of an alcohol to the metal triflate generates a new complex, which increases both the polymerization rate and stereocontrol compared to those achieved by the metal triflate without an alcohol in the polymerization of N,N-diethylacrylamide. While the lanthanide triflate-catalyzed stereoselective polymerization of acrylamides in MeOH has already been well established synthetically, this is the first example that proves the formation of an alcohol-coordinated catalyst as the active catalyst. Job’s plot suggests that the stoichiometry between Yb(OTf)3 and MeOH in the complex is 1:2. The polymerization rate decreases slightly when MeOD is used instead of MeOH, with a secondary isotope effect of 1.14, strongly suggesting the importance of hydroxyl groups for increasing the reactivity. In contrast, no apparent secondary isotope effect is observed to affect the stereoselectivity. The chirality of the alcohol ligand does not affect the stereoselectivity, illustrating that the stereochemistry is most likely controlled by the penultimate effect, which has already been proposed. Furthermore, the conditions are highly compatible with those for organotellurium-mediated radical polymerization, and the dual control of molecular weight and tacticity is successfully achieved. The role of alcohol in the Yb(OTf)3- and Y(OTf)3-catalyzed stereoselective radical polymerization of acrylamides is clarified. The coordination of two equivalents of alcohol to the metal triflate generates a complex, which increases both the polymerization rate and stereocontrol compared to those without an alcohol. The importance of hydroxyl groups of the alcohol is suggested by the observed secondary isotope effect for the rate enhancement. The conditions are highly compatible with those for organotellurium-mediated radical polymerization, and the dual control of molecular weight and tacticity is successfully achieved.

Studies towards Pyridine‐Based N,N,O‐Gold(III) Complexes: Synthesis, Characterization and Application

Gold(III) coordination of new chiral polydentate (N,)N,O‐pyridine based ligands is reported. Successful coordination afforded novel chiral N,N,O‐tridentate Au(III) complexes with the 2‐pyridyl‐6‐[(1S,2S,5R)‐neomenthol‐1‐yl]pyridine ligand (1H, 13C, 15N NMR, HRMS, IR, XRD). The chiral 2‐aryl‐6‐alkylpyridine alcohol ligands were prepared from 2,6‐dibromopyridine by initial stereoselective addition to (–)‐menthone and (+)‐camphor, respectively, and subsequent Suzuki cross‐coupling with a series arylboronic acids. Testing of catalytic activity in propargyl cyclopropanation demonstrated that the new N,N,O‐ligated gold(III) complex was highly catalytic active and outperformed AuCl3.

The effect of functionalization on solubility and plasmonic features of gold nanoparticles

Effect of functionalization on stability, solubility, and plasmonic features of gold nanoparticle with the general formula of Au18(SR)14 in water solvent has been studied in this work. Thiol functional groups including 1,1-mercapto-ethyl alcohol, s-cysteamine, thioglycolic acid, and beta-mercaptoethanol have been used. Electronic band-gap, excitation energies, dipole moment, and hardness for all gold nanoparticles in water solvent were investigated using the quantum mechanical approach. Intermolecular forces, radial distribution function (RDF), mean square displacement (MSD), and solvation free energy were calculated by using simulation methods. Electronic band-gap, and excitation energy analysis show that surface modification of gold nanoparticles can change their electronic and plasmonic properties. The analysis of dipole moments indicates that ligands affect the nanoparticle’s solubility. An increase of hardness and therefore chemical stability can be observed for functionalized nanoparticles compared to the bare structure. Intermolecular energies analyses suggest that structure with 1,1-mercapto ethyl alcohol ligand has the strongest interaction with the solvent. The analysis of RDF diagrams also indicates that the molecule with 1,1-mercapto ethyl alcohol ligand has the sharpest pick. The slope of the linear part of MSD diagrams that is the criterion of solute’s lateral diffusion is the highest value for nanoparticle with 1,1-mercapto ethyl alcohol ligand. Furthermore, functionalization also affects solvation free energy contributions. According to obtained data of quantum mechanical calculations and molecular dynamics simulations, it may be concluded that particle with 1,1-mercapto ethyl alcohol is the best ligand for increasing solubility, stability, and plasmonic functions of Au18(SR)14 structures among the examined ones.

Syntheses, structures and magnetic properties of novel tetrameric Ln2Mn2 and ring-like Ln4Mn4 clusters

Two series of heterometallic Ln–Mn clusters Ln2Mn2 and Ln4Mn4 were successfully synthesized in the presence of alcohol ligands, and the magnetic coupling interaction between metal ions were characterized by theoretical calculations.