Browse
Submit Data
Databases
API
Help

Dataset Information

25 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Synthesis and Reactivity of Paramagnetic Nickel Polypyridyl Complexes Relevant to C(sp2 )-C(sp3 )Coupling Reactions.

ABSTRACT: A number of new transition metal catalyzed methods for the formation of C(sp2 )-C(sp3 ) bonds have recently been described. These reactions often utilize bidentate polypyridyl-ligated Ni catalysts, and paramagnetic NiI halide or aryl species are proposed in the catalytic cycles. However, there is little knowledge about complexes of this type. Here, we report the synthesis of paramagnetic bidentate polypyridyl-ligated Ni halide and aryl complexes through elementary reactions proposed in catalytic cycles for C(sp2 )-C(sp3 ) bond formation. We investigate the ability of these complexes to undergo organometallic reactions that are relevant to C(sp2 )-C(sp3 ) coupling through stoichiometric studies and also explore their catalytic activity.

SUBMITTER: Mohadjer Beromi M

PROVIDER: S-EPMC6479119 | biostudies-literature | 2019 Apr

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Synthesis and Reactivity of Paramagnetic Nickel Polypyridyl Complexes Relevant to C(sp2 )-C(sp3 )Coupling Reactions.

Mohadjer Beromi Megan M Brudvig Gary W GW Hazari Nilay N Lant Hannah M C HMC Mercado Brandon Q BQ

Angewandte Chemie (International ed. in English) 20190327 18

A number of new transition metal catalyzed methods for the formation of C(sp2 )-C(sp3 ) bonds have recently been described. These reactions often utilize bidentate polypyridyl-ligated Ni catalysts, and paramagnetic NiI halide or aryl species are proposed in the catalytic cycles. However, there is little knowledge about complexes of this type. Here, we report the synthesis of paramagnetic bidentate polypyridyl-ligated Ni halide and aryl complexes through elementar ...[more]

PMID: 30859704

Similar Datasets

About the selectivity and reactivity of active nickel electrodes in C-C coupling reactions.

Project description:Active anodes which are operating in highly stable protic media such as 1,1,1,3,3,3-hexafluoroisopropanol are rare. Nickel forms, within this unique solvent, a non-sacrificial active anode at constant current conditions, which is superior to the reported powerful molybdenum system. The reactivity for dehydrogenative coupling reactions of this novel active anode increases when the electrolyte is not stirred during electrolysis. Besides the aryl-aryl coupling, a dehydrogenative arylation reaction of benzylic nitriles was found while stirring the mixture providing quick access to synthetically useful building blocks.

| S-EPMC9052091 | biostudies-literature

Electrochemical Nickel-Catalyzed C(sp3)-C(sp3) Cross-Coupling of Alkyl Halides with Alkyl Tosylates.

Project description:Formation of new C(sp3)-C(sp3) bonds is a powerful synthetic tool to increase molecular diversity, which is highly sought after in medicinal chemistry. Traditional generation of carbon nucleophiles and more modern cross-electrophile-coupling methods typically lack sufficient selectivity when cross-coupling of analogous C(sp3)-containing reactants is attempted. Herein, we present a nickel-catalyzed, electrochemically driven method for the coupling of alkyl bromides with alkyl tosylates. Selective cross-coupling transformations were achieved even between C(sp3)-secondary bromides and tosylates. Key to achieve high selectivity was the combination of the tosylates with sodium bromide as the supporting electrolyte, gradually generating small amounts of the more reactive bromide by substitution and ensuring that one of the reaction partners in the nickel-catalyzed electroreductive process is maintained in excess during a large part of the process. The method has been demonstrated for a wide range of substrates (>30 compounds) in moderate to good yields. Further expanding the scope of electroorganic synthesis to C(sp3)-C(sp3) cross-coupling reactions is anticipated to facilitate the switch to green organic synthesis and encourage future innovative electrochemical transformations.

| S-EPMC10416217 | biostudies-literature

Enantioselective C(sp3)-C(sp3) cross-coupling of non-activated alkyl electrophiles via nickel hydride catalysis.

Project description:Cross-coupling of two alkyl fragments is an efficient method to produce organic molecules rich in sp3-hybridized carbon centres, which are attractive candidate compounds in drug discovery. Enantioselective C(sp3)-C(sp3) coupling is challenging, especially of alkyl electrophiles without an activating group (aryl, vinyl, carbonyl). Here, we report a strategy based on nickel hydride addition to internal olefins followed by nickel-catalysed alkyl-alkyl coupling. This strategy enables the enantioselective cross-coupling of non-activated alkyl halides with alkenyl boronates to produce chiral alkyl boronates. Employing readily available and stable olefins as pro-chiral nucleophiles, the coupling proceeds under mild conditions and exhibits broad scope and high functional-group tolerance. Applications for the functionalization of natural products and drug molecules, as well as the synthesis of chiral building blocks and a key intermediate to (S)-(+)-pregabalin, are demonstrated.

| S-EPMC7610379 | biostudies-literature

Persistent organonickel complexes as general platforms for Csp2-Csp3 coupling reactions.

Project description:The importance of constructing Csp2-Csp3 bonds has motivated the development of electrochemical, photochemical and thermal activation methods to reductively couple abundant aryl and alkyl electrophiles. However, these methodologies are limited to couplings of very specific substrate classes and require specialized sets of catalysts and reaction set-ups. Here we show a consolidation of these myriad strategies into a single set of conditions that enable reliable alkyl-aryl couplings, including those that were previously unknown. These reactions rely on the discovery of unusually persistent organonickel complexes that serve as stoichiometric platforms for C(sp2)-C(sp3) coupling. Aryl, heteroaryl or vinyl complexes of Ni can be inexpensively prepared on a multigram scale by mild electroreduction from the corresponding C(sp2) electrophile. Organonickel complexes can be isolated and stored or telescoped directly to reliably diversify drug-like molecules. Finally, the procedure was miniaturized to micromole scales by integrating soluble battery chemistries as redox initiators, enabling a high-throughput exploration of substrate diversity.

| S-EPMC11374490 | biostudies-literature

Benzylic C(sp3)-C(sp2) cross-coupling of indoles enabled by oxidative radical generation and nickel catalysis.

Project description:A mechanistically unique functionalization strategy for a benzylic C(sp3)-H bond has been developed based on the facile oxidation event of indole substrates. This novel pathway was initiated by efficient radical generation at the benzylic position of the substrate, with subsequent transition metal catalysis to complete the overall transformation. Ultimately, an aryl or an acyl group could be effectively delivered from an aryl (pseudo)halide or an acid anhydride coupling partner, respectively. The developed method utilizes mild conditions and exhibits a wide substrate scope for both substituted indoles and C(sp2)-based reaction counterparts. Mechanistic studies have shown that competitive hydrogen atom transfer (HAT) processes, which are frequently encountered in conventional methods, are not involved in the product formation process of the developed strategy.

| S-EPMC8179435 | biostudies-literature

Fluorinated Organic Paramagnetic Building Blocks for Cross-Coupling Reactions.

Project description:New stable polyfluorinated nitroxide radicals for use in cross-coupling reactions, namely, N-tert-butyl-N-oxyamino-2,3,5,6-tetrafluoro-4-iodobenzene and N-tert-butyl-N-oxyamino-2,3,5,6-tetrafluoro-4-ethynylbenzene, were prepared from perfluoroiodobenzene. The reaction of the polyfluoro derivative with tert-butylamine under autoclaving conditions leading to the formation of N-tert-butyl-2,3,5,6-tetrafluoro-4-iodoaniline proved to be the key stage of the whole process. The fluorinated tert-butyl iodophenyl nitroxide was found to form in a solid state via N-O···I halogen bonds, a one-dimensional assembly of the radicals. The acceptor role of the nitroxide group in the halogen bonding changes to a donor role when the nitroxide reacts with Cu(hfac)2. In the last case, zero-dimensional assembly prevails, giving a three-spin complex with axial coordinated nitroxide groups and, as a consequence, causing ferromagnetic intramolecular exchange interactions between Cu(II) and radical spins.

| S-EPMC7699513 | biostudies-literature

A TMEDA-Iron Adduct Reaction Manifold in Iron-Catalyzed C(sp2 )-C(sp3 ) Cross-Coupling Reactions.

Project description:Herein, we expand the current molecular-level understanding of one of the most important and effective additives in iron-catalyzed cross-coupling reactions, N,N,N',N'-tetramethylethylenediamine (TMEDA). Focusing on relevant phenyl and ethyl Grignard reagents and slow nucleophile addition protocols commonly used in effective catalytic systems, TMEDA-iron(II)-aryl intermediates are identified via in situ spectroscopy, X-ray crystallography, and detailed reaction studies to be a part of an iron(II)/(III)/(I) reaction cycle where radical recombination with FePhBr(TMEDA) (2Ph ) results in selective product formation in high yield. These results differ from prior studies with mesityl Grignard reagent, where poor product selectivity and low catalytic performance can be attributed to homoleptic iron-ate species. Overall, this study represents a critical advance in how amine additives such as TMEDA can modulate selectivity and reactivity of organoiron species in cross-coupling.

| S-EPMC8968675 | biostudies-literature

C(sp3)-C(sp3) bond formation via nickel-catalyzed deoxygenative homo-coupling of aldehydes/ketones mediated by hydrazine.

Project description:Aldehydes and ketones are widely found in biomass resources and play important roles in organic synthesis. However, the direct deoxygenative coupling of aldehydes or ketones to construct C(sp3)-C(sp3) bond remains a scientific challenge. Here we report a nickel-catalyzed reductive homo-coupling of moisture- and air-stable hydrazones generated in-situ from naturally abundant aldehydes and ketones to construct challenging C(sp3)-C(sp3) bond. This transformation has great functional group compatibility and can suit a broad substrate scope with innocuous H2O, N2 and H2 as the by-products. Furthermore, the application in several biological molecules and the transformation of PEEK model demonstrate the generality, practicability, and applicability of this novel methodology.

| S-EPMC8211713 | biostudies-literature

Ruthenium PNN(O) Complexes: Cooperative Reactivity and Application as Catalysts for Acceptorless Dehydrogenative Coupling Reactions.

Project description:The novel tridentate PNNOH pincer ligand LH features a reactive 2-hydroxypyridine functionality as well as a bipyridyl-methylphosphine skeleton for meridional coordination. This proton-responsive ligand coordinates in a straightforward manner to RuCl(CO)(H)(PPh3)3 to generate complex 1. The methoxy-protected analogue LMe was also coordinated to Ru(II) for comparison. Both species have been crystallographically characterized. Site-selective deprotonation of the 2-hydroxypyridine functionality to give 1' was achieved using both mild (DBU) and strong bases (KOtBu and KHMDS), with no sign of involvement of the phosphinomethyl side arm that was previously established as the reactive fragment. Complex 1' is catalytically active in the dehydrogenation of formic acid to generate CO-free hydrogen in three consecutive runs as well as for the dehydrogenative coupling of alcohols, giving high conversions to different esters and outperforming structurally related PNN ligands lacking the NOH fragment. DFT calculations suggest more favorable release of H2 through reversible reactivity of the hydroxypyridine functionality relative to the phosphinomethyl side arm.

| S-EPMC5770139 | biostudies-literature

Reactions of Fluoroalkanes with Mg-Mg Bonds: Scope, sp3 C-F/sp2 C-F Coupling and Mechanism.

Project description:sp3 C-F Bonds of fluoroalkanes (7 examples; 1°, 2° and 3°) undergo addition to a low-valent Mg-Mg species generating reactive organomagnesium reagents. Further reactions with a series of electrophiles results in a net C-F to C-B, C-Si, C-Sn or C-C bond transformation (11 examples, diversity). The new reactivity has been exploited in an unprecedented one-pot magnesium-mediated coupling of sp3 C-F and sp2 C-F bonds. Calculations suggest that the sp3 C-F bond activation step occurs by frontside nucleophilic attack of the Mg-Mg reagent on the fluoroalkane.

| S-EPMC6471154 | biostudies-literature