Ruthenium(ii) complexes with N-heterocyclic carbene–phosphine ligands for the N-alkylation of amines with alcohols

Organic & Biomolecular Chemistry, Год журнала: 2021, Номер 19(15), С. 3451 - 3461

Опубликована: Янв. 1, 2021

A Ru catalyst with the hetero-bidentate NHC-phosphine ligand, which realizes N-alkylation of amines alcohols improved catalytic activity.

Язык: Английский

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Manganese Catalyzed Direct Amidation of Esters with Amines

The Journal of Organic Chemistry, Год журнала: 2021, Номер 86(3), С. 2339 - 2358

Опубликована: Янв. 7, 2021

The transition metal catalyzed amide bond forming reaction of esters with amines has been developed as an advanced approach for overcoming the shortcomings traditional methods. broad scope substrates in amidations remains a challenge. Here, manganese(I)-catalyzed method direct synthesis amides from various number and is reported unprecedented substrate using low catalyst loading. A wide range aromatic, aliphatic, heterocyclic esters, even fatty acid reacted diverse primary aryl amines, alkyl secondary to form amides. It noteworthy that this provides first example amines. acid–base mechanism amidation was elucidated by DFT calculations.

Язык: Английский

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Recent advances on N-heterocyclic carbene transition metal complexes for dehydrogenative catalysis using alcohols

Catalysis Today, Год журнала: 2020, Номер 370, С. 114 - 141

Опубликована: Окт. 20, 2020

Язык: Английский

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A Phosphine-Oxide Cobalt(II) Complex and Its Catalytic Activity Studies toward Alcohol Dehydrogenation Triggered Direct Synthesis of Imines and Quinolines

Inorganic Chemistry, Год журнала: 2024, Номер 63(21), С. 9786 - 9800

Опубликована: Май 13, 2024

Herein, a new pincer-like amino phosphine donor ligand, H2L1, and its phosphine-oxide analog, H2L2, were synthesized. Subsequently, cobalt(II) complexes 1 2 synthesized by the reaction of anhydrous Co(II)Cl2 with ligands H2L1 respectively. The fully characterized various physicochemical spectroscopic characterization techniques. Finally, identity was confirmed single crystal X-ray structure determination. ligand containing complex converted to oxide in air acetonitrile solution. Both investigated as precatalysts for alcohol dehydrogenation-triggered synthesis imines air. more efficient than 1. A wide array alcohols amines successfully reacted mild condition result good excellent yields. Precatalyst also highly varieties quinolines As H2L2 has side arms that can be deprotonated, we base (KOtBu) promoted deprotonation events studies DFT calculations. These have shown mono amine arm attached pyridine is quite feasible, leads dearomatized pyridyl ring 2a. mechanistic investigations catalytic reaction, combination experimental computational studies, suggested complex, 2a acted an active catalyst. proceeded through hydride transfer pathway. activation barrier this step calculated 26.5 kcal/mol, which consistent temperature under aerobic conditions. Although are explored such reactions, ligand-containing still unexplored.

Язык: Английский

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Ru⁰ or Ru^II: A Study on Stabilizing the “Activated” Form of Ru-PNP Complexes with Additional Phosphine Ligands in Alcohol Dehydrogenation and Ester Hydrogenation

Inorganic Chemistry, Год журнала: 2020, Номер 59(7), С. 5099 - 5115

Опубликована: Март 20, 2020

The complex Ru-MACHO has been previously shown to undergo uncontrolled degradation subsequent base-induced dehydrochlorination in the absence of a substrate. In this study, we report that stabilization dehydrochlorinated with phosphines furnishes complexes whose structures depend on employed: while PMe3 led expected octahedral RuII complex, PPh3 provided access trigonal-bipyramidal Ru0 complex. Because both proved be active base-free (de)hydrogenation reactions, thorough quantum-chemical calculations were employed understand reaction mechanism. show lead same mechanistic scenario after phosphine dissociation and, therefore, only differ energetically step. According calculations, typically proposed metal-ligand cooperation mechanism is not most viable pathway. Instead, metal-ligand-assisted pathway preferred. Finally, experiments addition enhances catalyst's performance comparison PR3-free "activated" Ru-MACHO.

Язык: Английский

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Tautomerism vs lone pair metal ligand cooperation in selective Mn-PNN catalyzed hydrogenation of amides

Journal of Catalysis, Год журнала: 2024, Номер 430, С. 115350 - 115350

Опубликована: Фев. 1, 2024

Язык: Английский

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The key role of the latent N–H group in Milstein's catalyst for ester hydrogenation

Chemical Science, Год журнала: 2021, Номер 12(24), С. 8477 - 8492

Опубликована: Янв. 1, 2021

We report a detailed mechanistic study of ester hydrogenation catalyzed by the activated form Milstein’s catalyst. Catalyst activation leads to replacement dialkylamino side group with an NHEt group, which has key role in catalysis.

Язык: Английский

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Mechanism and Origin of Chemoselectivity of Ru-Catalyzed Cross-Coupling of Secondary Alcohols to β-Disubstituted Ketones

The Journal of Organic Chemistry, Год журнала: 2020, Номер 85(19), С. 12444 - 12455

Опубликована: Авг. 31, 2020

Ru-catalyzed cross-coupling of secondary alcohols with only byproducts H2 and H2O provides a green synthetic strategy to prepare β-disubstituted ketones. Density functional theory (DFT) calculations were performed the coupling 1-phenylethanol cyclohexanol as model reaction gain deeper mechanistic insights herein. The details main key steps possible side reactions clarified, obtained results are consistent reported selectivity. Hydrogenation α,β-unsaturated ketones dehydrogenation ruthenium hydride intermediate direct chemoselectivity-determining stages. hydrogenation via 1,4-addition generates more stable intermediates, being favored over that 1,2-addition, thus avoids formation alkene products. conjugation π–π stacking effects phenyl weak electronic effect alkyls explain dominance specific ketone products in stage. is kinetically operative but not exergonic enough stop irreversible dihydrogen release an open system, alcohol absent. Furthermore, water evaporation aldol condensation found be double-edged sword, it can accelerate stage prevent from decrease selectivity therein thermodynamics overall.

Язык: Английский

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The Mechanism of Guerbet Reaction by Metal Ligand Cooperation

Chemistry - A European Journal, Год журнала: 2024, Номер 30(42)

Опубликована: Май 16, 2024

Abstract The Guerbet reaction is important for the synthesis of longer‐chain monoalcohols like isobutanol through catalytic transfer hydrogenation from short‐chain methanol and ethanol. However, mechanism becomes complicated, especially considering variations in different metal‐ligand cooperation (MLC) catalysts used. In order to further understand reaction, DFT studies were performed figure out detailed initiated by unique Mn‐PCP MLC Catalyst. Our results suggest that even with assistance carbanion site PCP ligand, direct substitution less favored than condensation‐reduction mechanism. key step final reduction carbonyl, which 1,4‐reduction unsaturated aldehyde prior 3,4‐reduction or 1,2‐reduction due stronger interaction between catalyst substrate. It found production preferred over n ‐butanol because lower total free energy barrier relative product. Finally, changing electronic effect catalyst, we relation highest span was not monotonous a point optimal exists numerically.

Язык: Английский

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Planar-Locked Ru-PNN Catalysts in 1-Phenylethanol Dehydrogenation

Organometallics, Год журнала: 2020, Номер 39(20), С. 3628 - 3644

Опубликована: Окт. 2, 2020

Ru-PNN pincer catalysts of the general form [{PNN}Ru(H)(Cl)(CO)] can dehydrogenate alcohols through inner- and outer-sphere mechanisms, but determining favored path is challenging. To address this challenge, following planar-locked quinoline-based PNN ligands, which cannot key inner-sphere transition states intermediates, were synthesized: 2-((ditertbutylphosphaneyl)methyl)-N,N-diethylquinolin-8-amine (QNPtBu), 2-((diisopropylphosphaneyl)methyl)-N,N-diethylquinolin-8-amine (QNPiPr), 2-((diphenylphosphaneyl)methyl)-N,N-diethylquinolin-8-amine (QNPPh). In addition to quinoline-derived we also prepared isoquinoline ligand N-((1-((ditert-butylphosphaneyl)methyl)isoquinolin-3-yl)methyl)-N-ethylethanamine (IsoQNP) two known picoline- lutidine-derived ligands 2-((ditert-butylphosphaneyl)methyl)pyridine (PicP) 2-((ditert-butylphosphaneyl)methyl)-6-methylpyridine (LutP). These six coordinated Ru(II) ions prepare new complexes formulation [{L}Ru(H)(Cl)(CO)] analogous Milstein's catalyst precursor (1PyCl). The X-ray structural, NMR, UV–vis, FTIR spectroscopic properties are similar parent complex 1PyCl used in catalytic 1-phenylethanol acceptor-less transfer dehydrogenation. comparative results demonstrate that 1Py outperforms other catalysts. DFT reaction profiles computed for suggest has access a lower-energy path, whereas only proceed high-energy mechanism may even get trapped unreactive alkoxide sinks.

Язык: Английский

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