Iron Catalysis Research Articles

Iron–Copper Dual Catalysis Enabling C−C and C−X (X=N, B, P, S, Sn) Bond Formation

AbstractThe dual‐catalysis tactics where two types of catalysts are connected in one single reaction operation are highly prized in the novel bond constructions that are difficult or unattainable to be achieved with current mono‐catalysis. In recent years, increased emphasis on sustainable catalytic methods on more economic and eco‐friendly processes has shifted the focus to catalysis with earth‐abundant transition metals, such as iron, copper, and so on. As two of the most inexpensive and environmentally friendly metals on earth, the research and development based on either iron or copper catalysis are flourishing, and iron‐copper dual‐catalyzed reactions appeal more and more attention. In this review, we mainly cover the construction of C−C, C−N, C−B, C−P, C−S and C−Sn bonds enabled by iron‐copper dual‐catalysis published in the literature from 2011.

Advances in the Iron-Catalyzed Direct Functionalizations of ­Heterocycles

AbstractDirect functionalization of heterocycles is an advanced strategy for diversifying privileged and biorelevant heterocycle-containing molecules. Particularly, use of the most abundant transition metal, iron, as a catalyst makes this process highly cost-effective and sustainable. Recently, some progress has been realized towards the direct functionalization of heterocycles under iron catalysis. Herein, we present the developments in the C–H bond functionalizations and related reactions of various heterocycles by abundant iron salts. This Synpacts is categorized into different sections based on heterocycles being functionalized, and each section is discussed based on the type of reaction catalyzed by iron.1 Introduction2 Functionalization of Indoles2.1 Alkylation2.2 Alkenylation2.3 Other Reactions3 Oxindoles and Isatins3.1 C–C Bond Formation3.2 C–Heteroatom Bond Formation4 Pyridines and Furans5 Functionalization of Azoles6 Summary and Outlook

One-Pot Synthesis of Diaryl Sulfonamides using an Iron- and Copper-Catalyzed Aryl C–H Amidation Process

AbstractA one-pot, two-stage synthesis of diaryl sulfonamides using sequential iron and copper catalysis is developed. Regioselective para-iodination of activated arenes by the super Lewis acid, iron triflimide and N-iodosuccinimide (NIS), is followed by a copper(I)-catalyzed N-arylation reaction. The process is found to be applicable for the coupling of a range of anisoles, anilines and acetanilides with primary sulfonamides and is used for the one-pot synthesis of biologically important compounds.

Inactivation of Microcystis aeruginosa by peroxydisulfate activated with single‐atomic iron catalysis: Efficiency and mechanisms

Harmful algal blooms caused by cyanobacteria in drinking water have posed serious threats to destroy aquatic ecosystems, and the toxins they produce are harmful to human and animal health. Herein, the feasibility of removing Microcystis aeruginosa (M. aeruginos) and microcystin-LR (MC-LR) by free radicals produced by simple-atomic iron-doped g-C3N4 (Fe-g-C3N4)-activated peroxydisulfate (PDS) was studied. Pristine g-C3N4 and three kinds of Fe-g-C3N4 with different compositions were successfully synthesized and characterized. When the initial algae density was 2.5 × 106 cells·mL−1, approximately 96.25 % of M. aeruginosa cells were inactivated with 2.0 g·L−1 Fe-g-C3N4 and 4.0 mM PDS under the conditions of pH 7.0, and MC-LR could also be effectively degraded. The activated system can effectively remove M. aeruginosa, and MC-LR was evaluated for its morphological characteristics, cell membrane integrity and microcystin degradation. In addition to the widely recognized reaction species (SO4• − and •OH), singlet oxygen (1O2) was another predominant radical for destroying the cell structure and removing MC-LR. The materials can be well recycled, and a possible removal mechanism was proposed. This work shows that the Fe-g-C3N4-activated PDS system is an environmentally friendly and efficient technology for algae removal and algal toxin reduction.

Hydrodeoxygenation of Acetophenone Derivatives on a an Iron–Ruthenium Bimetallic Catalyst

Key words iron catalysis - ruthenium catalysis - bimetal catalysis - nanoparticles - hydrodeoxygenation - acetophenones

Acceptorless Alcohol Dehydrogenation with an Iron–Cobalt Double-Atom Catalyst

Key words double-atom catalyst - iron catalysis - cobalt catalysis - dehydrogenation - alcohols

Visible Light-Induced Hydrosilylation of Electron-Deficient Alkenes by Iron Catalysis.

Herein, we reported a method for iron-catalyzed, visible-light-induced hydrosilylation reactions of electron-deficient alkenes to produce value-added silicon compounds. Alkenes bearing functional groups with different steric properties were suitable substrates, as were derivatives of structurally complex natural products. Mechanistic studies showed that chlorine radicals generated by iron-catalyzed ligand-to-metal charge transfer in the presence of lithium chloride promoted the formation of silyl radicals.

Cyanomethylation of the Benzene Rings and Pyridine Rings via Direct Oxidative Cross-Dehydrogenative Coupling with Acetonitrile.

A novel and efficient approach for the amine-directed dehydrogenative C(sp2)-C(sp3) coupling of arylamines with acetonitrile was reported by using FeCl2 as the catalyst. Substituted anilines, aminopyridines, naphthylamines, and some nitrogen-containing heterocyclic arylamines react with inactive acetonitrile to form the corresponding arylacetonitriles in moderate to good yields. This protocol features nontoxic iron catalysis, efficient atom economy, nonprefunctionalized starting materials, good regioselectivity, and excellent compatibility of functional groups and aromatic rings, providing a novel, straightforward, and green approach toward arylacetonitriles.

Allylboronic Esters as Acceptors in Radical Addition, Boron 1,2-Migration, and Trapping Cascades.

Radical 1,3-carboheteroarylation and 1,3-hydroalkylation of allylboronic esters comprising a 1,2-boron shift is reported. Allylboronic esters are generally used in synthesis as allylation reagents, where the boronic ester moiety gets lost. In the introduced cascades, alkylboronic esters are obtained with the boron entity remaining in the product. The carboheteroarylation of the allylboronic esters are conducted without a metal catalyst, and the 1,3-hydroalkylation is achieved using iron catalysis. Both reactions work efficiently under mild conditions.

Metal‐Organic‐Framework based Catalytic Micromotor for Enhanced Water Decontamination

AbstractThis work demonstrates the application of a Fe3O4/zeolitic imidazolate framework 67 (ZIF67) micromotor for improved catalytic degradation of organic pollutants. The micromotors were fabricated by simple adsorption of Fe3O4 nanoparticles on the surface of ZIF67 microparticles, which were synthesized by wet chemistry method. Both Fe3O4 and ZIF67 perform asymmetric decomposition of H2O2 to achieve bubble propulsion of the micromotors. The ferromagnetism of Fe3O4 enables easy directional control of the micromotor. The porous structure of ZIF67 benefits the enrichment of pollutant molecules around the micromotors, facilitating the efficient catalytic degradation. With intensified interaction between active sites and pollutant molecules due to self‐propelled motion and synergistic catalysis of iron in Fe3O4 and zinc ions in ZIF67, the micromotors exhibit enhanced degradation activity of methylene blue as compared to the pure Fe3O4 or ZIF67 counterparts without autonomous motion. This research can be extended to developing other metal‐organic frameworks (MOF)‐integrated micromotors for the environmental applications.

An iron-catalyzed multicomponent reaction of cycloketone oxime esters, alkenes, DABCO·(SO2)2 and trimethylsilyl azide

The synthesis of β-azidosulfones starting from alkenes, cycloketone oxime esters, trimethylsilyl azide and a sulfur dioxide surrogate of DABCO·(SO2)2 under iron catalysis is developed.

Markovnikov-selective double hydrosilylation of challenging terminal aryl alkynes under cobalt and iron catalysis.

Geminal bis(silanes) are unique compounds with interesting properties. The most straightforward way to access them is double hydrosilylation of alkynes, which was established only recently. Previous articles about transition metal-catalysed double hydrosilylation show that terminal aryl alkynes are a challenge. We report on cobalt(II) and iron(III) complexes with the easy-to-synthesise N,N,N-tridentate hydrazone ligand being active precatalysts in Markovnikov-selective double hydrosilylation of terminal aryl alkynes. The influence of the hydrazone ligand structure and the potential role of the sodium triethylborohydride activator were studied. Sets of geminal bis(silanes) with two identical or different silyl groups were synthesised, showing the applicability of the reported method.

Photochemical alkynylation of hydrosilanes by iron catalysis.

Alkynylsilanes are one kind of essential synthetic block in organic chemistry. The established synthetic routes retain some drawbacks regarding harsh reaction conditions or expensive/rare metal catalysts. Herein, we report a method for iron-catalyzed, visible-light-induced alkynylation of hydrosilanes to produce value-added silicon compounds. Alkynes bearing functional groups with different steric properties and alkyl/aryl hydrosilanes were both suitable substrates. Mechanistic studies showed that chlorine radicals generated by iron-catalyzed ligand-to-metal charge transfer in the presence of lithium chloride promoted the formation of silyl radicals.

Aerobic Partial Oxidation of Alkanes Using Photodriven Iron Catalysis

Photodriven oxidations of alkanes in trifluoroacetic acid using commercial and synthesized Fe(III) sources as catalyst precursors and dioxygen (O2) as the terminal oxidant are reported. The reactions produce alkyl esters and occur at ambient temperature in the presence of air, and catalytic turnover is observed for the oxidation of methane in a pure O2 atmosphere. Under optimized conditions, approximately 17% conversion of methane to methyl trifluoroacetate at more than 50% selectivity is observed. It is demonstrated that methyl trifluoroacetate is stable under catalytic conditions, and thus overoxidized products are not formed through secondary oxidation of methyl trifluoroacetate.

Iron-catalyzed domino coupling reactions of π-systems.

The development of environmentally benign, inexpensive, and earth-abundant metal catalysts is desirable from both an ecological and economic standpoint. Certainly, in the past couple decades, iron has become a key player in the development of sustainable coupling chemistry and has become an indispensable tool in organic synthesis. Over the last ten years, organic chemistry has witnessed substantial improvements in efficient synthesis because of domino reactions. These protocols are more atom-economic, produce less waste, and demand less time compared to a classical stepwise reaction. Although iron-catalyzed domino reactions require a mindset that differs from the more routine noble-metal, homogenous iron catalysis they bear the chance to enable coupling reactions that rival that of noble-metal-catalysis. This review provides an overview of iron-catalyzed domino coupling reactions of π-systems. The classifications and reactivity paradigms examined should assist readers and provide guidance for the design of novel domino reactions.

Iron-Catalyzed Oxidative Amination of Benzylic C(sp3)-H Bonds with Anilines.

Iron-catalyzed oxidative amination of benzylic C(sp3)-H bonds with anilines bearing electron-withdrawing groups (EWGs) or electron-donating groups (EDGs) is realized based on simple variations of N-substituents on imidazolium cations in novel ionic Fe(III) complexes. The structural modification of the imidazolium cation resulted in regulation of the redox potential and the catalytic performance of the iron metal center. Using DTBP as oxidant, [HItBu][FeBr4] showed the highest catalytic activity for anilines bearing EWGs, while [HIPym][FeBr4] was more efficient for EDG-substituted anilines. This work provides alternative access to benzylamines with the advantages of both a wide substrate scope and iron catalysis.

Iron Catalysis: Design and Applications

The effects of adding hop to lamb patties on their oxidative stability were evaluated. Two experiments were performed. In the first experiment, patties were prepared by adding water (control), hop infusion (2 g infused hop/kg) or a sodium ascorbate solution (0.5 g/kg), then cooked and refrigerated stored for 3 days. In the second one, patties were prepared by adding water (control), hop infusion (2 g infused hop/kg) or a hop powder dispersion (2 g hop/kg), and then stored either raw: 4 °C for 7 days or −18° C for 90 days, or cooked: 4 °C for 3 days. The antioxidant effect of hop was assessed by means of thiobarbituric acid reactive substances, protein carbonyls, colour, and sensorial analysis. Hop showed a significant antioxidant effect, which was stronger for hop powder than for hop infusion. The addition of hop powder caused a slight decrease in the consumer acceptance of patties as compared to control and hop infusion-added patties.

Stereoselective Dehydroxyboration of Allylic Alcohols to Access (E)-Allylboronates by a Combination of C-OH Cleavage and Boron Transfer under Iron Catalysis.

Iron-catalyzed direct SN2' dehydroxyboration of allylic alcohols has been developed to access (E)-stereoselective allylboronates. Allylic alcohols with diverse structures and functional groups, especially derived from natural products, underwent smooth transformation. The six-membered ring transition state formed by allylic alcohols and iron-boron intermediate was indicated to be the key component involved in transfer of the boron group, activation of the C-OH bond, and control of the stereoselectivity.

An in-situ strategy to analyze multi-effect catalysis in iron-copper bimetals catalyzed Fenton-like processes

Iron-copper bimetals for Fenton-like catalysis were developed, due to efficient enhancement of catalytic activity by iron-copper synergy. However, deviation exists in mechanism analysis of multi-effect catalysis. In this study, a new in-situ strategy of shielding Fe(II) and Cu(I) from further reaction by trapping agents was developed, for analysis of iron catalysis alone, copper catalysis alone and synergistic effect in bimetallic catalyst systems. Inhibition efficiency and influence of trapping agents on Fe(II)/Cu(I) catalysis were quantitatively evaluated for reliability confirmation and method correction. The possible application scope was identified as pH of 4–6, and this strategy was available for analysis of five different groups of catalysts. The potential superiority and difference of the proposed strategy compared with current ex-situ strategy were also analyzed. The overestimation (12.1%–35.4%) of copper catalysis and biased analysis (0.1%–12.6%) of iron catalysis by ex-situ strategy can be alleviated, thereby improving accuracy for synergistic effect. In summary, this study proposed a new strategy to improve the understanding of iron-copper bimetallic catalysis, which can provide reference for other polymetallic catalysis analysis development.

Nitrene-Mediated P–N Coupling Under Iron Catalysis

P–N and P=N bonds play important roles in the design and synthesis of functional molecules such as bioactive compounds and organic ligands for catalysis. Existing methods for P–N coupling mostly re...