Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Combined Photoredox and Iron Catalysis for the Cyclotrimerization of Alkynes.

ABSTRACT: Successful combinations of visible-light photocatalysis with metal catalysis have recently enabled the development of hitherto unknown chemical reactions. Dual mechanisms from merging metal-free photocatalysts and earth-abundant metal catalysts are still in their infancy. We report a photo-organo-iron-catalyzed cyclotrimerization of alkynes by photoredox activation of a ligand-free Fe catalyst. The reaction operates under very mild conditions (visible light, 20?°C, 1?h) with 1-2?mol?% loading of the three catalysts (dye, amine, FeCl2 ).

SUBMITTER: Neumeier M

PROVIDER: S-EPMC7496134 | biostudies-literature | 2020 Aug

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Combined Photoredox and Iron Catalysis for the Cyclotrimerization of Alkynes.

Neumeier Michael M Chakraborty Uttam U Schaarschmidt Dieter D de la Pena O'Shea Victor V Perez-Ruiz Raul R Jacobi von Wangelin Axel A

Angewandte Chemie (International ed. in English) 20200527 32

Successful combinations of visible-light photocatalysis with metal catalysis have recently enabled the development of hitherto unknown chemical reactions. Dual mechanisms from merging metal-free photocatalysts and earth-abundant metal catalysts are still in their infancy. We report a photo-organo-iron-catalyzed cyclotrimerization of alkynes by photoredox activation of a ligand-free Fe catalyst. The reaction operates under very mild conditions (visible light, 20 °C, 1 h) with 1-2 mol % loading of ...[more]

PMID: 32190960

Similar Datasets

syn-Selective alkylarylation of terminal alkynes via the combination of photoredox and nickel catalysis.

Project description:Substituted alkenes are pivotal structural motifs found in pharmaceuticals and agrochemicals. Although numerous methods have been developed to construct substituted alkenes, a generally efficient, mild, catalytic platform for the conversion of alkynes to this highly functionalized scaffold via successive C-C bond forming steps remains in high demand. Here we describe an intermolecular, regio- and syn-stereoselective alkylarylation of terminal alkynes with tertiary alkyl oxalates via photoredox-Ni dual catalysis. This catalytic protocol, synergistically combining Ir/Ni-catalyzed alkyne difunctionalization with photoinduced alkene isomerization, affords trisubstituted alkenes with excellent efficiency and syn-stereoselectivity. The mild conditions tolerate many functional groups, allowing for a broad scope with respect to terminal alkynes, aryl bromides, and alkyl oxalates.

| S-EPMC6208420 | biostudies-literature

Regioselective Hydroalkylation and Arylalkylation of Alkynes by Photoredox/Nickel Dual Catalysis: Application and Mechanism.

Project description:Alkynes are an important class of organic molecules due to their utility as versatile building blocks in synthesis. Although efforts have been devoted to the difunctionalization of alkynes, general and practical strategies for the direct hydroalkylation and alkylarylation of terminal alkynes under mild reaction conditions are less explored. Herein, we report a photoredox/nickel dual-catalyzed anti-Markovnikov-type hydroalkylation of terminal alkynes as well as a one-pot arylalkylation of alkynes with alkyl carboxylic acids and aryl bromides via a three-component cross-coupling. The results indicate that the transformations proceed via a new mechanism involving a single-electron transfer with subsequent energy-transfer activation pathways. Moreover, steady-state and time-resolved fluorescence-spectroscopy measurements, density functional theory (DFT) calculations, and wavefunction analysis have been performed to give an insight into the catalytic cycle.

| S-EPMC7154703 | biostudies-literature

Polymer-Supported-Cobalt-Catalyzed Regioselective Cyclotrimerization of Aryl Alkynes.

Project description:A convoluted poly(4-vinylpyridine) cobalt(II) (P4VP-CoCl2) system was developed as a stable and reusable heterogeneous catalyst. The local structure near the Co atom was determined on the basis of experimental data and theoretical calculations. This immobilized cobalt catalyst showed high selectivity and catalytic activity in the [2 + 2 + 2] cyclotrimerization of terminal aryl alkynes. With 0.033 mol % P4VP-CoCl2, the regioselective formation of 1,3,5-triarylbenzene was realized without 1,2,4-triarylbenzene formation. Further, a multigram-scale (11 g) reaction proceeded efficiently. In addition, the polymer-supported catalyst was successfully recovered and used three times. X-ray photoelectron spectroscopy analysis of the recovered catalyst suggested that cobalt was in the +2 oxidation state. The 1,3,5-triarylbenzene derivatives were applied to the synthesis of a molecular beam electron resist and a polycyclic aromatic hydrocarbon.

| S-EPMC8611791 | biostudies-literature

Aminomethylations of electron-deficient compounds-bringing iron photoredox catalysis into play.

Project description:The α-functionalisation of N-containing compounds is an area of broad interest in synthetic chemistry due to their presence in biologically active substances among others. Visible light-induced generation of nucleophilic α-aminoalkyl radicals as reactive intermediates that can be trapped by electron-deficient alkenes presents an attractive and mild approach to achieve said functionalisation. In this work, [Fe(iii)(phtmeimb)2]PF6 (phtmeimb = phenyl(tris(3-methylimidazol-2-ylidene))borate), an N-heterocyclic carbene (NHC) complex based on Earth-abundant iron, was used as photoredox catalyst to efficiently drive the formation of α-aminoalkyl radicals from a range of different α-trimethylsilylamines and their subsequent addition to a number of electron-deficient alkenes under green light irradiation. Mechanistic investigations elucidated the different reaction steps of the complete photocatalytic cycle. In terms of yields and substrate scope, we show that [Fe(iii)(phtmeimb)2]PF6 can compete with noble metal photoredox catalysts, for instance outcompeting archetypal [Ru(bpy)3]Cl2 under comparable reaction conditions, illustrating that iron photocatalysts can efficiently facilitate photoredox reactions of synthetic value.

| S-EPMC11290444 | biostudies-literature

Combined Photoredox and Carbene Catalysis for the Synthesis of γ-Aryloxy Ketones.

Project description:N-heterocyclic carbenes (NHCs) have emerged as catalysts for the construction of C-C bonds in the synthesis of substituted ketones under single-electron processes. Despite these recent reports, there still remains a need to increase the utility and practicality of these reactions by exploring new radical coupling partners. Herein, we report the synthesis of γ-aryloxyketones via combined NHC/photoredox catalysis. In this reaction, an α-aryloxymethyl radical is generated via oxidation of an aryloxymethyl potassium trifluoroborate salt, which is then added into styrene derivatives to provide a stabilized benzylic radical. Subsequent radical-radical coupling reaction with an azolium radical affords the γ-aryloxy ketone products.

| S-EPMC9012476 | biostudies-literature

Combined Photoredox and Carbene Catalysis for the Synthesis of Ketones from Carboxylic Acids.

Project description:As a key element in the construction of complex organic scaffolds, the formation of C-C bonds remains a challenge in the field of synthetic organic chemistry. Recent advancements in single-electron chemistry have enabled new methods for the formation of various C-C bonds. Disclosed herein is the development of a novel single-electron reduction of acyl azoliums for the formation of ketones from carboxylic acids. Facile construction of the acyl azolium in situ followed by a radical-radical coupling was made possible merging N-heterocyclic carbene (NHC) and photoredox catalysis. The utility of this protocol in synthesis was showcased in the late-stage functionalization of a variety of pharmaceutical compounds. Preliminary investigations using chiral NHCs demonstrate that enantioselectivity can be achieved, showcasing the advantages of this protocol over alternative methodologies.

| S-EPMC7250732 | biostudies-literature

Single-molecule photoredox catalysis.

Project description:The chemistry of life is founded on light, so is it appropriate to think of light as a chemical substance? Planck's quantization offers a metric analogous to Avogadro's number to relate the number of particles to an effective reaction of single molecules and photons to form a new compound. A rhodamine dye molecule serves as a dehalogenating photocatalyst in a consecutive photoelectron transfer (conPET) process which adds the energy of two photons, with the first photon inducing radical formation and the second photon triggering PET to the substrate molecule. Rather than probing catalytic heterogeneity and dynamics on the single-molecule level, single-photon synthesis is demonstrated: the light quantum constitutes a reactant for the single substrate molecule in a dye-driven reaction. The approach illustrates that molecular diffusion and excited-state internal conversion are not limiting factors in conPET reaction kinetics because of catalyst-substrate preassociation. The effect could be common to photoredox catalysis, removing the conventional requirement of long excited-state lifetimes.

| S-EPMC6340401 | biostudies-literature

Molecular Rubies in Photoredox Catalysis.

Project description:The molecular ruby [Cr(tpe) 2 ] 3+ and the tris(bipyridine) chromium(III) complex [Cr(dmcbpy) 3 ] 3+ as well as the tris(bipyrazine)ruthenium(II) complex [Ru(bpz) 3 ] 2+ were employed in the visible light-induced radical cation [4+2] cycloaddition (tpe = 1,1,1-tris(pyrid-2-yl)ethane, dmcbpy = 4,4'-dimethoxycarbonyl-2,2'-bipyridine, bpz = 2,2'-bipyrazine), while [Cr(ddpd) 2 ] 3+ serves as a control system (ddpd = N,N'-dimethyl-N,N'-dipyridin-2-ylpyridine-2,6-diamine). Along with an updated mechanistic proposal for the CrIII driven catalytic cycle based on redox chemistry, Stern-Volmer analyses, UV/Vis/NIR spectroscopic and nanosecond laser flash photolysis studies, we demonstrate that the very weakly absorbing photocatalyst [Cr(tpe) 2 ] 3+ outcompetes [Cr(dmcbpy) 3 ] 3+ and even [Ru(bpz) 3 ] 2+ in particular at low catalyst loadings, which appears contradictory at first sight. The high photostability, the reversible redoxchemistry and the very long excited state lifetime account for the exceptional performance and even reusability of [Cr(tpe) 2 ] 3+ in this photoredox catalytic system.

| S-EPMC9021569 | biostudies-literature

Combined Photoredox Catalysis for Value-Added Conversion of Contaminants at Spatially Separated Dual Active Sites.

Project description:As 2 indispensable counterparts in one catalysis system, the independent reduction and oxidation reactions require synergetic regulation for cooperatively promoting redox efficiency. Despite the current success in promoting the catalytic efficiency of half reduction or oxidation reactions, the lack of redox integration leads to low energy efficiency and unsatisfied catalytic performance. Here, we exploit an emerging photoredox catalysis system by combining the reactions of nitrate reduction for ammonia synthesis and formaldehyde oxidation for formic acid production, in which superior photoredox efficiency is achieved on the spatially separated dual active sites of Ba single atoms and Ti3+. High catalytic redox rates are accomplished for respective ammonia synthesis (31.99 ± 0.79 mmol gcat -1 h-1) and formic acid production (54.11 ± 1.12 mmol gcat -1 h-1), reaching a photoredox apparent quantum efficiency of 10.3%. Then, the critical roles of the spatially separated dual active sites are revealed, where Ba single atoms as the oxidation site using h+ and Ti3+ as the reduction site using e- are identified, respectively. The efficient photoredox conversion of contaminants is accomplished with environmental importance and competitive economic value. This study also represents a new opportunity to upgrade the conventional half photocatalysis into the complete paradigm for sustainable solar energy utilization.

| S-EPMC10076036 | biostudies-literature

Photoredox Catalysis Using Heterogenized Iridium Complexes*.

Project description:Heterogenized photoredox catalysts provide a path for sustainable chemical synthesis using highly tunable, reusable constructs. Here, heterogenized iridium complexes as photoredox catalysts were assembled via covalent attachment to metal oxide surfaces (ITO, ZrO2 , Al2 O3 ) in thin film or nanopowder constructs. The goal was to understand which materials provided the most promising constructs for catalysis. To do this, reductive dehalogenation of bromoacetophenone to acetophenone was studied as a test reaction for system optimization. All catalyst constructs produced acetophenone with high conversions and yields with the fastest reactions complete in fifteen minutes using Al2 O3 supports. The nanopowder catalysts resulted in faster and more efficient catalysis, while the thin film catalysts were more robust and easily reused. Importantly, the thin film constructs show promise for future photoelectrochemical and electrochemical photoredox setups. Finally, all catalysts were reusable 2-3 times, performing at least 1000 turnovers (Al2 O3 ), demonstrating that heterogenized catalysts are a sustainable catalyst alternative.

| S-EPMC9292873 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data