Imidazole-based Potential Bi- and Tridentate Nitrogen Ligands: Synthesis, Characterization and Application in Asymmetric Catalysis

Sívek, Roman; Bureš, Filip; Pytela, Oldřich; Kulhánek, Jiří

doi:10.3390/molecules13092326

Cited by 13 publications

(8 citation statements)

References 35 publications

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“…The amino pyridine isomers L 2 , L 3 , and L 4 have conspicuously different effects on the polymerization rate. It is also observed that m-aminopyridine (L 3 ) or p-aminopyridine (L 4 ) is a more effective ligand than N-methylimidazole (L 1 ), which is perhaps the most widely employed aromatic ligand [15,16,17]. When L 4 is used, the fastest polymerization rate of 6.98 × 10 −4 mol/L·s is observed.…”

Section: Resultsmentioning

confidence: 99%

“…When L 4 was used, the lowest DPQ formation was obtained at 2.2%, and similar results were obtained under different experimental conditions. It is reported that the formation of DPQ is affected by various parameters, such as the polymerization temperature, types of solvent, polarity of reaction medium, and basicity of ligands, and its formation significantly increases as both solvent acidity and polymerization temperature increase [8,16,26,27,28]. DPQ production is the lowest with L 4 , which has the fastest reaction rate.…”

Section: Resultsmentioning

confidence: 99%

“…Limiting the amount of DPQ production is critical, since the remaining DPQ in polymers plays a detrimental role that accelerates the decomposition of PPE while processing it at high temperature. For the ligands, aliphatic amines and imidazole and its derivatives are widely used due to their capability to bind with metal catalysts and the frequent occurrence of C–O coupling during PPE synthesis [16,17]. Studies have indicated that the remaining ligands in the polymers may lower the thermal stability of the PPE and change the color, especially when aliphatic amine ligands are used.…”

Section: Introductionmentioning

confidence: 99%

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A Highly Efficient Aromatic Amine Ligand/Copper(I) Chloride Catalyst System for the Synthesis of Poly(2,6-dimethyl-1,4-phenylene ether)

et al. 2018

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Highly active catalyst systems for polymerizing 2,6-dimethylphenol were studied by using aromatic amine ligands and copper(I) chloride. The aromatic amine ligands employed were pyridine, 1-methylimidazole, 2-aminopyridine, 3-aminopyridine, and 4-aminopyridine. A mixture of chloroform and methanol (9:1, v/v) was used as a polymerization solvent. All experiments were performed with oxygen uptake measurement apparatus, while the reaction rate for each aromatic amine ligand-Cu catalyst system and the amount of by-product, 3,3′,5,5′-Tetramethyl-4,4′diphenoquinone (DPQ), were measured to determine the efficiency of the catalyst systems. The 4-aminopyridine/Cu (I) catalyst system was found to be extremely efficient in poly(2,6-dimethyl-1,4-phenylene ether) (PPE) synthesis; it had the fastest reaction rate of 6.98 × 10−4 mol/L·s and the lowest DPQ production. The relatively high basicity of 4-aminopyridne and the less steric hindrance arising from a coordination of Cu and 4-aminopyridine in this catalyst are responsible for the fast polymerization rate. When 2-aminoprydine (an isomer of 4-aminopyridine) was used as a ligand, however, no polymerization occurred probably due to steric hindrance.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Highly Efficient Aromatic Amine Ligand/Copper(I) Chloride Catalyst System for the Synthesis of Poly(2,6-dimethyl-1,4-phenylene ether)

et al. 2018

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“…On the other hand, the pharmacologically relevant imidazole ring in the α,β -unsaturated-2-acyl imidazoles 2 is found in numerous natural products and ligands . It is also used as the precursor of N-heterocyclic carbenes, and the imidazole ring can easily be cleaved and functionalized (ester/amide surrogates) to different carbonyl analogues.…”

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confidence: 99%

Asymmetric α-Functionalization of 2-Alkyl Azaarenes: Synthesis of Tertiary Fluorides Having Vicinal Stereogenic Centers

2021

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An enantioselective approach for synthesizing fluorinated azaarenes containing vicinal quaternary−tertiary stereocenters is summarized. The chiral copper(I)−phosphine complex binds with the azaarenes followed by Michael addition to unsaturated acyl imidazoles, resulting in α-functionalized products with an excellent level of enantioselectivities (up to 99%), diastereoselectivities (>20:1), and yields (up to 97%). Furthermore, post-functionalization of the acyl imidazole part has also been demonstrated.

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“…Such compounds should possess higher coordination abilities towards transition metals, owing to the presence of nitrogen atoms. 4 Hence, in our previous studies, we focused on the synthesis of N-containing α-amino acid- [5][6][7][8][9][10][11] or tartaric acid-derived 12 compounds and their Cu 2+ complexes. The syntheses of target N-alkylated dicarbohydrazides were carried out in two ways.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and coordination ability of tartrate-derived N-alkyl dicarbohydrazides towards Cu2+ ions

Kousalová¹,

Pytela²,

Bureš³

2012

Arkivoc

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Starting from (R,R)-tartaric acid we have synthesized eight N-and N,N-(di-)alkyl dicarbohydrazides 3 and 4, by two general methods, which were able to form two M 2 L and ML complexes. These target compounds were further used as model nitrogen ligands coordinating Cu 2+ ions. Whereas the formation of the first type of complexes is linearly dependent on the increasing electron-donating ability of the appended alkyls, the ML complexes were significantly affected by both electronic and steric effects of the alkyl groups used. These observations were supported by theoretical calculations of both complex types. The target compounds were also employed as chiral nitrogen ligands in the asymmetric version of the Henry reaction. Modest chemical yields and low enantioselectivities were attained for ligand 3a bearing one methyl group on each terminal nitrogen atom. Structure-property relationships were also evaluated to gain useful guidelines for ligand design targeting catalysts for asymmetric reactions.

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Imidazole-based Potential Bi- and Tridentate Nitrogen Ligands: Synthesis, Characterization and Application in Asymmetric Catalysis

Cited by 13 publications

References 35 publications

A Highly Efficient Aromatic Amine Ligand/Copper(I) Chloride Catalyst System for the Synthesis of Poly(2,6-dimethyl-1,4-phenylene ether)

A Highly Efficient Aromatic Amine Ligand/Copper(I) Chloride Catalyst System for the Synthesis of Poly(2,6-dimethyl-1,4-phenylene ether)

Asymmetric α-Functionalization of 2-Alkyl Azaarenes: Synthesis of Tertiary Fluorides Having Vicinal Stereogenic Centers

Synthesis and coordination ability of tartrate-derived N-alkyl dicarbohydrazides towards Cu2+ ions

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