Amine Functionalized Pincer-like Azo-aromatic Complexes of Cobalt and Their Catalytic Activities in the Synthesis of Quinoline via Acceptorless Dehydrogenation of Alcohols

Organometallics, Год журнала: 2023, Номер 42(15), С. 1854 - 1868

Опубликована: Июль 6, 2023

Herein we disclose a series of phosphine-free cobalt(II)-based catalytic systems bearing redox non-innocent amine functionalized azo-aromatic pincer-like ligand for the synthesis quinoline by dehydrogenative oxidation 2-amino benzyl alcohol and subsequent coupling with ketone. All precatalysts were characterized thoroughly using various spectroscopic techniques DFT studies. The protocol was efficient versatile, providing major advances in quinoline. It also found to be applicable gram-scale quinolines as well. Several control experiments, kinetic studies, studies have proposed plausible reaction mechanism where azo-pyridine moiety acts activate α-C–H bond Co(II) → Co(I) reduction leads formation aldehyde. generated aldehyde undergoes base-catalyzed C–C result quinolines. potential controls efficiency precatalysts. Thus, complex 3 most anodic best precatalyst among complexes 1–4.

Язык: Английский

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Noninnocent Azo-Aromatic Cobalt(II)-Catalyzed sp³ C–H Alkylation of Fluorenes with Alcohols

The Journal of Organic Chemistry, Год журнала: 2024, Номер 89(3), С. 1910 - 1926

Опубликована: Янв. 11, 2024

Herein, employing well-defined redox noninnocent cobalt(II) complexes an efficient sp3 C–H alkylation of fluorenes using alcohols as alkylating agents to result in alkylated is reported. The catalytic protocol was versatile with various and benzyl alcohols. It also showed very good functional group tolerance both fluorenes. Moreover, single-step simultaneous di C–C well the C–N reaction observed this protocol. Such selective dialkylation indeed beneficial. Several control experiments, deuterium labeling, 1H NMR kinetic studies have revealed a ligand radical-based borrowing hydrogen mechanism involving azo-aromatic cobalt catalysts for

Язык: Английский

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Zn(II)‐Stabilized Azo‐Anion Radical Catalyzed Sustainable C−C Bond Formation: Regioselective Alkylation of Fluorene, Oxindole, and Indoles

ChemCatChem, Год журнала: 2024, Номер 16(10)

Опубликована: Фев. 7, 2024

Abstract Herein we report a sustainable approach for the alkylation of ketones, 9 H ‐fluorene, oxindole, and indole using alcohols as alkylating agent catalyzed by well‐defined air‐stable zinc catalyst ( 1 ) tridentate redox non‐innocent arylazo ligand, 2‐((4‐chlorophenyl)diazenyl)‐1,10‐phenanthroline L ). 2–3 mol % efficiently produces substituted α‐alkylated 9‐alkylated fluorenes, C3 ‐alkylated oxindoles, indoles in moderate to good isolated yields. In aerial condition, formation bis(indolyl)methane (BIMs) derivatives were observed when subjected primary alcohols. A few drug molecules containing BIMs prepared The exhibited chemoselectivity during functionalization fluorene with oleyl alcohol β‐citronellol. control experiments, including deuterium labeling performed unveil reaction mechanism indicate that one‐electron reduced azo‐anion radical species [ ]‐formed situ, acts active catalyst. All events occur at redox‐active aryl‐azo which reservoir hydrogen electrons throughout catalytic cycle, keeping Zn(II)‐center template.

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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Multi-hydroxyl POSS supported iridium complexes as a recyclable catalyst for selective synthesis of N-/C-substituted indoles and the total synthesis of HIV-1 fusion inhibitor

Journal of Catalysis, Год журнала: 2023, Номер 429, С. 115205 - 115205

Опубликована: Ноя. 24, 2023

Язык: Английский

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Ligand Redox Controlled Amine Dehydrogenation and Imine Hemilability in Singlet Diradical Azo-aromatic Ni(II) Complexes: Characterization of the Electron Transfer Series of Azo-imine Complexes of Ni(II)

Dalton Transactions, Год журнала: 2024, Номер 53(24), С. 10250 - 10260

Опубликована: Янв. 1, 2024

Singlet diradical Ni( ii ) complexes [1] and [2] of azo-amine azo-imine ligands have shown ligand redox-induced amine dehydrogenation imine hemilability, respectively.

Язык: Английский

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A well-defined phosphine free metal-ligand cooperative route for N-alkylation of aromatic amines via activation of renewable alcohols catalyzed by a NNN pincer cobalt(II) complexes

Dalton Transactions, Год журнала: 2025, Номер unknown

Опубликована: Янв. 1, 2025

Two cobalt( ii ) complexes C1 and C2, supported by an NNN pincer, were synthesized, characterized with various techniques. These utilized to study catalytic activity in the N -alkylation of amines via borrowing hydrogen strategy.

Язык: Английский

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An o-Phenylene Bridged Noninnocent Bis-Azopyridyl Ligand and Its Copper Complexes: Synthesis, Characterization of Electron Transfer Events, and Use of the Cu Complexes for Oxidation of Alcohols

Inorganic Chemistry, Год журнала: 2025, Номер unknown

Опубликована: Апрель 14, 2025

In this report, an o-phenylene-bridged tetradented redox-noninnocent bis-azopyridyl ligand [L] and its copper complexes [1] [2] were synthesized characterized. The electron transfer events of [L], as well [2], characterized by single-crystal X-ray structure determination, various spectroscopic studies, DFT calculations. While [[L]Cu(II)Cl2] has unreduced [[L]•-Cu(I)Cl] contains a one-electron-reduced [L]•- , which is antiferromagnetically coupled with the unpaired spin on Cu(II). Reduction one generated complex [2]•-, remained in electronically bistable situation form valence tautomers: [2A]•-, [[L]•-Cu(I)Cl]•- [2B]•-, [[L]2-Cu(II)Cl]•-. Further one-electron reduction [2]•- mixture Cu complexes: [2A]-, [[L]2-Cu(I)]- [2B]-, [[L]3•-Cu(II)]-. Complexes examined for catalytic oxidation alcohols. was more efficient than [1]. protocol highly versatile both primary secondary aromatic aliphatic Mechanistic investigations showed that [[L]•-Cu(I)OCH2Ph]•- (A) active catalyst, subsequently, through ligand-based redox events, acted catalyst over course reaction.

Язык: Английский

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Aerial Oxidation of Alcohols by an Amide and Imidazole Functionalized Bioinspired Cu‐Complex and Its Switching with N‐Oxides

ChemistrySelect, Год журнала: 2025, Номер 10(18)

Опубликована: Май 1, 2025

Abstract In this work, employing an imidazole and amide functionalized pincer like Cu(II) complex as a pre‐catalyst, alcohol oxidation reaction without N‐oxide is explored. This was very active for the of benzyl alcohol. The best catalytic activity observed with 1 mmol alcohol, 4 mol% 20 KO t Bu in toluene at 70 °C 24 h. Both primary well secondary alcohols were successfully oxidized. It found that, protocol more efficient (5–12 h time) than (∼24 h). by can be switched N‐oxides 2,2,6,6‐tetramethylpiperidinyloxy (TEMPOH) 9‐azabicyclo[3.3.1]nonane N ‐Oxyl (ABNOH). mechanism studied UV–vis, EPR X‐ray photoelectron spectral studies. Thus, versatile showed good functional group tolerance substitutions on aromatic alcohols. Aerial oxygen acted sole oxidant cooperation / Cu(I) redox events. exhibited switchable behavior presence N‐oxide. Though Cu‐complex catalyzed explored, such where occurs containing inert ligand cocatalyst scarce.

Язык: Английский

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Electron transfer catalysis mediated by 3d complexes of redox non-innocent ligands possessing an azo function: a perspective

Dalton Transactions, Год журнала: 2023, Номер 52(43), С. 15627 - 15646

Опубликована: Янв. 1, 2023

It was first reported almost two decades ago that ligands with azo functions are capable of accepting electron(s) upon coordination to produce azo-anion radical complexes, thereby exhibiting redox non-innocence. Over the past decades, there have been numerous reports such complexes along their structures and diverse characteristics. The ability a coordinated function accept one or more electron(s), acting as an electron reservoir, is currently employed carry out transfer catalysis since they can undergo transformation at mild potentials due presence energetically accessible energy levels. cooperative involvement non-innocent ligand(s) containing group metal centre adjust modulate Lewis acidity latter through selective ligand-centred events, manipulating capacity bind substrate. We summarized list row transition iron, cobalt, nickel, copper zinc incorporating exploited catalysts effectuate sustainable synthesis wide variety useful chemicals. These include ketazines, pyrimidines, benzothiazole, benzoxazoles, N-acyl hydrazones, quinazoline-4(3)H-ones, C-3 alkylated indoles, N-alkylated anilines heteroamines. reaction pathways, demonstrated by catalytic loops, reveal ligand act sink in initial steps bring about alcohol oxidation thereafter, serve pool final products either via HAT PCET processes.

Язык: Английский

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