Oxidative coupling of aromatic substrates with alkynes and alkenes under rhodium catalysis

Cobalt-catalyzed three-component assembly of aromatic oximes with substituted dienes and formaldehyde

A cobalt-catalyzed three-component assembly of substituted aryl oximes with dienes and formaldehyde via C-H bond activation is described. This protocol affords highly regio- and chemoselective substituted homoallylic alcohols with moderate-to-excellent yields. The scope of this protocol has been extensively explored with various substituted aryl ketoximes and aldoximes. Butadiene and internally substituted dienes are also well compatible for this transformation. A plausible reaction mechanism is proposed to account for the present reaction and is supported by deuterium labeling studies.

Rh(iii)-catalyzed building up of used heterocyclic cations: facile access to white-light-emitting materials

The first example of rhodium-catalyzed nondirected C-H activation/annulation reactions for the construction of fused heterocyclic cations is reported herein with excellent regioselectivity. Deuterium-labeling experiments indicated that the C(sp3)-H bond cleavage of the N-methyl group might be the rate-limiting step during the reaction process. This protocol provides an opportunity to rapidly access highly π-conjugated fused heterocyclic cations, which opens up a new avenue for efficient screening of single-molecular white-light-emitting materials, pure red-light-emitting materials, and π-conjugated radical materials. Importantly, novel white-light-emitting materials exhibited distinct anti-Kasha dual-emission and could rapidly be fabricated into robust organic and low-cost white light-emitting diodes.

Synthesis of 1H-Isoindoles via Ruthenium(II)-Catalyzed Cyclization of Benzimidates with Alkenes

A Ru(II)-catalyzed efficient synthesis of 1H-isoindoles via the cyclization of benzimidates with alkenes has been demonstrated. This methodology exhibits high compatibility with various functionalized activated and unactivated olefins containing different sensitive functional groups. This protocol provides an effective method for synthesizing various 1H-isoindole derivatives in decent to excellent yields. Notably, the ortho-alkenylation of benzimidates with unactivated alkenes was achieved. A potential reaction mechanism has been suggested that involves C-H activation, 1,2 insertion, and β-hydride elimination subsequent to aza-Michael addition.

Cobalt-Catalyzed Enantio- and Regioselective C(sp3 )-H Alkenylation of Thioamides

An enantioselective cobalt-catalyzed C(sp3 )-H alkenylation of thioamides with but-2-ynoate ester coupling partners employing thioamide directing groups is presented. The method is operationally simple and requires only mild reaction conditions, while providing alkenylated products as single regioisomers in excellent yields (up to 85 %) and high enantiomeric excess [up to 91 : 9 enantiomeric ratio (er), or up to >99 : 1 er after a single recrystallization]. Diverse downstream derivatizations of the products are demonstrated, delivering a range of enantioenriched constructs. Extensive computational studies using density functional theory provide insight into the detailed reaction mechanism, origin of enantiocontrol, and the unusual regioselectivity of the alkenylation reaction.

Rhodium-catalyzed annulation of hydrazines with vinylene carbonate to synthesize unsubstituted 1-aminoindole derivatives

Herein, we describe rhodium-catalysed C-H bond activation for [3 + 2] annulation using hydrazide and vinylene carbonate, providing an efficient method for synthesising unsubstituted 1-aminoindole compounds. Characterised by high yields, mild reaction conditions, and no need for external oxidants, this transformation demonstrates excellent regioselectivity and a wide tolerance for various functional groups.

Synthesis of Spiroisoindolinones via Ru(II)-Catalyzed Spiroannulation of N-Acyl Ketimines with Aryl Isocyanates/Isothiocyanates through Aromatic C-H Bond Activation

Herein, we disclose the first report on Ru(II)-catalyzed amidation/thioamidation of 3-hydroxy-3-arylisoindolinones with isocyanates/isothiocyanates, respectively. The reaction furnishes spiroisoindolinones via sequential C-H functionalization of ortho C-H bond followed by intramolecular cyclization in moderate to high yields (up to 94%). Moreover, the developed strategy is highly atom-economical and site-selective and shows diverse substrate generality. Also, synthesized spiroisoindolinones undergo several chemical transformations.

Catalytic, asymmetric carbon-nitrogen bond formation using metal nitrenoids: from metal-ligand complexes via metalloporphyrins to enzymes

The introduction of nitrogen atoms into small molecules is of fundamental importance and it is vital that ever more efficient and selective methods for achieving this are developed. With this aim, the potential of nitrene chemistry has long been appreciated but its application has been constrained by the extreme reactivity of these labile species. This liability however can be attenuated by complexation with a transition metal and the resulting metal nitrenoids have unique and highly versatile reactivity which includes the amination of certain types of aliphatic C-H bonds as well as reactions with alkenes to afford aziridines. At least one new chiral centre is typically formed in these processes and the development of catalysts to exert control over enantioselectivity in nitrenoid-mediated amination has become a growing area of research, particularly over the past two decades. Compared with some synthetic methods, metal nitrenoid chemistry is notable in that chemists can draw from a diverse array of metals and catalysts , ranging from metal-ligand complexes, bearing a variety of ligand types, via bio-inspired metalloporphyrins, all the way through to, very recently, engineered enzymes themselves. In the latter category in particular, rapid progress is being made, the rate of which suggests that this approach may be instrumental in addressing some of the outstanding challenges in the field. This review covers key developments and strategies that have shaped the field, in addition to the latest advances, up until September 2023.

Transition-Metal-Catalyzed Dehydrogenative (3 + 2) Annulation of Aromatic Compounds: Synthesis of Indenes and Indanes via Dual Functionalization of Benzylic and ortho C-H Bonds

Intermolecular (3 + 2) annulation emerges as a potent approach for constructing 5-membered carbocycles through the fusion of two distinct components. This synopsis encapsulates recent strides in the realm of transition-metal-catalyzed dehydrogenative (3 + 2) annulation of aromatic hydrocarbons, achieved through the dual functionalization of benzylic and ortho C-H bonds. Encompassing three pivotal strategies, namely, (i) C-H bond activation, (ii) benzylic oxidation, and (iii) π-coordination activation, this review offers an overview of the field's recent developments.

Pd-Catalyzed Alkyne and Aryne Annulations: Synthesis and Photophysical Properties of π-Extended Coumarins

A Pd-catalyzed alkyne and aryne annulation strategy via C-H activation has been implemented for the synthesis of π-extended coumarins. This synthetic strategy provides a wide range of π-extended coumarins in moderate to good yields with good functional group compatibility. Photophysical properties of the synthesized π-extended coumarins have been evaluated, and some of them show interesting fluorescent properties. Three of the synthesized coumarins have been unambiguously established by a single-crystal XRD study.

Isoxazole as a nitrile synthon: en routes to the ortho-alkenylated isoxazole and benzonitrile with allyl sulfone catalyzed by Ru(II)

A Ru(II) catalyzed regioselective Heck-type C-H olefination of isoxazole with unactivated allyl phenyl sulfone is revealed. The solvent DCM offers dual sp2-sp2 C-H activation via an N-directed strategy, leading to ortho-olefinated isoxazoles with exclusive E-selectivity. On the other hand, in DCE solvent, isoxazole serves as the nitrile synthon and leads to o-olefinated benzonitrile. At a higher temperature (110 °C) in DCE, after the ortho-olefination Ru(II) mediated cleavage of isoxazoles delivered the nitrile functionality.

[RhCp*Cl2]2-Catalyzed Indole Functionalization: Synthesis of Bioinspired Indole-Fused Polycycles

Polycyclic fused indoles are ubiquitous in natural products and pharmaceuticals due to their immense structural diversity and biological inference, making them suitable for charting broader chemical space. Indole-based polycycles continue to be fascinating as well as challenging targets for synthetic fabrication because of their characteristic structural frameworks possessing biologically intriguing compounds of both natural and synthetic origin. As a result, an assortment of new chemical processes and catalytic routes has been established to provide unified access to these skeletons in a very efficient and selective manner. Transition-metal-catalyzed processes, in particular from rhodium(III), are widely used in synthetic endeavors to increase molecular complexity efficiently. In recent years, this has resulted in significant progress in reaching molecular scaffolds with enormous biological activity based on core indole skeletons. Additionally, Rh(III)-catalyzed direct C-H functionalization and benzannulation protocols of indole moieties were one of the most alluring synthetic techniques to generate indole-fused polycyclic molecules efficiently. This review sheds light on recent developments toward synthesizing fused indoles by cascade annulation methods using Rh(III)-[RhCp*Cl2]2-catalyzed pathways, which align with the comprehensive and sophisticated developments in the field of Rh(III)-catalyzed indole functionalization. Here, we looked at a few intriguing cascade-based synthetic designs catalyzed by Rh(III) that produced elaborate frameworks inspired by indole bioactivity. The review also strongly emphasizes mechanistic insights for reaching 1-2, 2-3, and 3-4-fused indole systems, focusing on Rh(III)-catalyzed routes. With an emphasis on synthetic efficiency and product diversity, synthetic methods of chosen polycyclic carbocycles and heterocycles with at least three fused, bridged, or spiro cages are reviewed. The newly created synthesis concepts or toolkits for accessing diazepine, indol-ones, carbazoles, and benzo-indoles, as well as illustrative privileged synthetic techniques, are included in the featured collection.

Tandem C-H Annulation Reaction of Benzaldehydes and Aminobenzoic Acids with Two Equivalents of Alkyne toward Isocoumarin-Conjugated Isoquinolinium Salts: A Family of Organic Luminophores

A novel rhodium-catalyzed tandem C-H annulation of commercially available benzaldehydes and aminobenzoic acids with 2 equiv of alkyne is reported for the construction of isocoumarin-conjugated isoquinolinium salts that demonstrate diverse outstanding photoactivity. Depending on the substituents in the isoquinolinium moiety, they display either highly efficient fluorescence (up to 99% of quantum yield) or strong fluorescence quenching, which is provided by the transfer of the HOMO from the isoquinolinium to the isocoumarin moiety. Importantly, the functional groups in the benzaldehyde coupling partner also strongly affect the reaction selectivity, shifting the pathway to the formation of the photoinactive isocoumarin-substituted indenone imines and indenyl amines. Selective formation of the latter can be achieved by using a reduced amount of the oxidizing additive.

Co(III)-Catalyzed three-component assembling of N-(2-pyrimidyl) indoles with dienes and formaldehyde

A highly regio- and chemoselective three-component assembling of N-pyrimidyl indoles with dienes and formaldehyde in the presence of a Co(III) catalyst was demonstrated. The scope of the reaction was investigated with a variety of indole derivatives to synthesize substituted homoallylic alcohols. Both butadiene and isoprene units were compatible with the reaction. To understand the reaction mechanism, various investigations were carried out, and suggested the plausibility of a reaction mechanism involving C-H bond activation as a key step.

Cascade C-H Activation/Annulation of Sulfoxonium Ylides with Vinyl Cyclopropanes: Access to Cyclopropane-Fused α-Tetralones

Rh-catalyzed weak and traceless directing-group-assisted cascade C-H activation and annulation of sulfoxonium ylides with vinyl cyclopropanes as a coupling partner have been accomplished to furnish functionalized cyclopropane-fused tetralones at moderate temperature. The C-C bond formation, cyclopropanation, functional group tolerance, late-stage diversifications of drug molecules, and scale-up are the important practical features.

Rhodium(III)-Catalyzed Intramolecular Annulation and Aromatization for the Synthesis of Pyrrolo[1,2-a]quinolines

A rhodium(III)-catalyzed protocol for the synthesis of pyrrolo[1,2-a]quinolines through intramolecular annulation of o-alkynyl amino aromatic ketones and subsequent aromatization is reported. This transformation builds the pyrrole and quinoline moieties of the pyrrolo[1,2-a]quinoline in one pot and achieves a flexible introduction of different substituent groups at 4- and 5-positions on products that were difficult to prepare by other means. The reaction proceeds smoothly on a gram scale, and the products are amenable to downstream synthetic manipulations.

Sustainable application of calcium carbide residue as a filler for 3D printing materials

Industrial activity results in ton-scale production of calcium carbide and generation of a significant amount of calcium carbide residue (CCR), which is often disposed of in the environment as waste. CCR is an active chemical, and rain washes away alkali from sludge, changing the pH of soils and water and damaging the environment. In this work, we explored new opportunities for the utilization of CCR in view of the coming industrial uptake of digital design and additive technologies. Amazingly, CCR can be successfully used as a filler for the modification of 3D printed materials towards the introduction of hybrid organic/inorganic frameworks. A series of commercially available plastics (PLA, ABS, Nylon, PETG, SBS) were successfully used as matrices for CCR-based composite production with high CCR contents up to 28%. Tensile analyses showed increases in tensile strength and Young's modulus of 9% and 60%, respectively. Moreover, in comparison with the pure plastics, the CCR-based materials better maintained the digitally designed shape (lower shrinkage). Importantly, CCR-filled materials are 3D printable, making them very promising components in the building sector. Considering the amount of already available CCR stored in the environment, this material is available in large quantities in the near future for hybrid materials, and anticipated opportunities exist in the additive manufacturing sector. The involvement of CCR in practical composite materials is equally important for environmental protection and reuse of already available multiple-ton wastes.

Rh(III)-Catalyzed [4 + 1] Annulation of Sulfoximines with Maleimides: Access to Benzoisothiazole Spiropyrrolidinediones

Rh(III)-catalyzed synthesis of benzoisothiazole spiropyrrolidinediones using sulfoximine as a directing group under a C-H activation and [4 + 1] annulation strategy with maleimides as a coupling partner is reported. The cyclization reaction was compatible with various substituted sulfoximine and maleimides. The deuterium-labeling studies were performed to investigate the mechanism of the reaction.

Triphenylcyclopentadienyl Rhodium Complexes in Catalytic C-H Annulations. Application for Synthesis of Natural Isocoumarins

Efficient protocols for the synthesis of triphenylcyclopentadienyl rhodium halides [(1,2,4-C₅Ph₃H₂)RhX₂]₂ (1a,b: X = Cl, I) starting from 1,2,4-triphenylcyclopentadiene or the cyclooctadiene derivative (1,2,4-C₅Ph₃H₂)Rh(cod) (2) were developed. Iodide abstraction from 1b with thallium or silver salts allowed us to prepare rhodocenium [(1,2,4-C₅Ph₃H₂)RhCp]PF₆ (3PF₆) and mesitylene complex [(1,2,4-C₅Ph₃H₂)Rh(mesitylene)](SbF₆)₂ (4(SbF₆)₂). Halides 1a,b (at 0.5 mol % loading) showed high catalytic activity in the construction of C-C, C-O, and C-N bonds via the C(sp²)-H activation approach. Their efficiency was demonstrated in the synthesis of more than 40 examples of polycyclic organic compounds (such as isocoumarins and naphthalenes, as well as isoquinolinium and dibenzo[a,f]quinolizinium salts). The protocols developed tolerate a wide range of functional groups. In particular, they were successfully used for the atom- and step-economical synthesis of hydroxy-substituted isocoumarins, including the natural product oospalactone 7fe. The 6- or 8-hydroxy-substituted isocoumarins showed moderate antiproliferative activity against several human cell lines in vitro.

Electrochemical rhodium catalysed alkyne annulation with pyrazoles through anodic oxidation - a metal oxidant/additive free methodology

Pyrazole and its derivatives are important azole heteroarenes prevalent in pharmaceutical compounds and have been used as ligands for protein binding, making them valuable targets for synthetic applications. Herein we disclose an electrochemical intermolecular C-H/N-H oxidative annulation of 2-phenylpyrazoles with alkynes using a rhodium(III) redox regime without any external metal oxidants in a water compatible solvent system. Both symmetrical and unsymmetrical alkynes were shown to be compatible with the optimized conditions.

Ru(II)-Catalyzed C-H Alkenylation of Benzimidates with Unactivated Olefins: A Route to ortho-Alkenylated Benzonitriles

A Ru(II)-catalyzed C-H alkenylation of benzimidates with unactivated alkenes providing ortho-alkenylated benzonitriles in good to excellent yields in a highly regio- and stereoselective manner is described. In the reaction, an imidate group converted into a nitrile under the reaction conditions. The alkenylation reaction was compatible with various substituted benzimidates as well as functionalized unactivated olefins, including ibuprofen-, neproxen-, coumarin-, and cholesterol-substituted alkenes. A feasible reaction mechanism was proposed to account for the present alkenylation reaction.

Manganese-catalyzed hydroarylation of multiple bonds

Transition metal-catalyzed C-H activation has become a promising strategy in organic synthesis due to its improved atom-, step- and resource economy. Considering the Earth's abundance, economic benefits, and low toxicity, 3d metal catalysts for C-H activation have received a significant focus. In particular, organometallic manganese-catalyzed C-H activation has proven to be versatile and suitable for a wide range of transformations such as C-H addition to π-components, arylation, alkylation, alkynylation, amination, and many more. Among them, manganese-catalyzed C-H addition to C-C and C-heteroatom multiple bonds exhibited unique and promising reactivity to construct a wide range of complex organic molecules. In this review, we highlight the developments in the field of manganese-catalyzed hydroarylation of multiple bonds via C-H activation with a range of applications until August 2022.

Ligand-assisted olefin-switched divergent oxidative Heck cascade with molecular oxygen enabled by self-assembled imines

Divergent oxidative Heck reaction has proven to be reliable for the rapid construction of molecular complexity, while olefins switched the outcome that remained underexplored.

Versatile Reactivity of Half-Sandwich Rhodium(III) Iminophosphonamide Complexes

Novel 18e̅ and 16e̅ pentamethylcyclopentadienyl rhodium(III) complexes [(η⁵-C₅Me₅)RhX(NPN)] (1a,b, X = Cl; 2a-c, X = PF₆, BAr₄^F) with chelating zwitterionic iminophosphonamide (NPN) ligands (Ph₂P(NR)(NR'); a, R = R' = p-Tol; b, R = p-Tol, R' = Me; c, R = R' = Me) were synthesized and characterized by single-crystal X-ray diffraction. In the 16e̅ complexes 2, the rhodium (Rh) atom is efficiently stabilized by π-donation of unshared N electrons, thus hampering coordination of the external ligands and rendering the 18e̅ complexes labile. Due to low coordination enthalpy, the cationic 18e̅ monocarbonyl and pyridine adducts 2a·L are stable only at low temperatures. At room temperature, 2·CO adducts readily give stable carbonyl-carbamoyl complexes [(η⁵-C₅Me₅)Rh(CO){(CO(NR')Ph₂P(NR)}]⁺ (4) formed as a result of CO insertion into the Rh-N bond, thus showing high nucleophilicity of the N atoms in 18e̅ complexes. High basicity of the Na⁺NPN^- precursors caused side deprotonation of the η⁵-C₅Me₅ ligand during the synthesis of 1 that yields unstable fulvene Rh(I) complexes [(η⁴-C₅Me₄CH₂)Rh{Ph₂P(NR)(NR')₂}] (3a,b). Complex 3a undergoes a facile reaction with isoprene to yield an unusual [(η⁵:η¹-C₅Me₄(CH₂)C(Me)═CHCH₂)Rh(NPN)] complex─the first example of intermolecular 1,4-metallacycloaddition of diene to the Rh-fulvene complex.

Rh(III)-Catalyzed Enone Carbonyl/Ketone-Directed Aerobic C-H Olefination of Aromatics with Unactivated Olefins

A Rh(III)-catalyzed weak enone carbonyl/ketone-assisted aerobic oxidative C-H olefination of aromatics with unactivated alkenes has been developed. This protocol involves cross-dehydrogenative Heck-type olefination reaction of various substituted biologically relevant chalcones and aromatic ketones such as acetophenones and chromones with various functionalized unactivated olefins in moderate to good yields. Further, ortho-alkylation of chalcones with norbornene is also demonstrated. A possible reaction mechanism involving weak chelation-assisted C-H activation/insertion/β-hydride elimination was proposed and supported by the deuterium labeling studies.

Synthesis of Furans via Rhodium(III)-Catalyzed Cyclization of Acrylic Acids with α-Diazocarbonyl Compounds

An efficient protocol for the synthesis of furans through Rh(III)-catalyzed vinyl C-H activation from acrylic acids and α-diazocarbonyl compounds has been developed. The reaction features broad functional group tolerance and affords a series of furans in moderate to good yields. Moreover, no additives such as copper or silver salts are required. Some control experiments are performed to give insight into the mechanism of this cascade transformation and the decarbonylation process is involved in the formation of the furan product.

Cp*RhIII-Catalyzed Cascade Annulation of Arylimidates with Pyridotriazoles toward Isoquinolin-3-ol Derivatives

A Cp*Rh^III-catalyzed efficient synthesis of isoquinolin-3-ol derivatives bearing a pyridinyl ring using imidate as a directing group under C-H activation strategy with pyridotriazoles as carbene reagents is reported. In this reaction, cascade C-H activation, regioselective cyclization, and elimination occur in one pot. The present methodology featured a good range of functional group tolerance and furnished the target products in moderate-to-excellent yields.

C-H bond activation and sequential addition to two different coupling partners: a versatile approach to molecular complexity

Sequential multicomponent C-H bond addition is a powerful approach for the rapid, modular generation of molecular complexity in a single reaction. In this approach, C-H bonds are typically added across π-bonds or π-bond isosteres, followed by subsequent coupling to another type of functionality, thereby forming two σ-bonds in a single reaction sequence. Many sequential C-H bond addition reactions have been developed to date, including additions across both conjugated and isolated π-systems followed by coupling with reactants such as carbonyl compounds, cyanating reagents, aminating reagents, halogenating reagents, oxygenating reagents, and alkylating reagents. These atom-economical reactions transform ubiquitous C-H bonds under mild conditions to more complex structures with a high level of regiochemical and stereochemical control. Surprising connectivities and diverse mechanisms have been elucidated in the development of these reactions. Given the large number of possible combinations of coupling partners, there are enormous opportunities for the discovery of new sequential C-H bond addition reactions.

Direct Synthesis of Biphenyl-2-carbonitriles by Rh(III)-Catalyzed C-H Hiyama Cross-Coupling in Water

This method represents an efficient rhodium(III)-catalyzed o-C-H arylation of readily available benzimidate derivatives with diverse arylsilanes in water as a sustainable solvent, enabling the straightforward synthesis of potentially useful biphenyl-2-carbonitrile derivatives. This silicon-based protocol employs benzimidates as both an efficacious directing group and the source of a nitrile group.

Designing Artificial Metalloenzymes by Tuning of the Environment beyond the Primary Coordination Sphere

Metalloenzymes catalyze a variety of reactions using a limited number of natural amino acids and metallocofactors. Therefore, the environment beyond the primary coordination sphere must play an important role in both conferring and tuning their phenomenal catalytic properties, enabling active sites with otherwise similar primary coordination environments to perform a diverse array of biological functions. However, since the interactions beyond the primary coordination sphere are numerous and weak, it has been difficult to pinpoint structural features responsible for the tuning of activities of native enzymes. Designing artificial metalloenzymes (ArMs) offers an excellent basis to elucidate the roles of these interactions and to further develop practical biological catalysts. In this review, we highlight how the secondary coordination spheres of ArMs influence metal binding and catalysis, with particular focus on the use of native protein scaffolds as templates for the design of ArMs by either rational design aided by computational modeling, directed evolution, or a combination of both approaches. In describing successes in designing heme, nonheme Fe, and Cu metalloenzymes, heteronuclear metalloenzymes containing heme, and those ArMs containing other metal centers (including those with non-native metal ions and metallocofactors), we have summarized insights gained on how careful controls of the interactions in the secondary coordination sphere, including hydrophobic and hydrogen bonding interactions, allow the generation and tuning of these respective systems to approach, rival, and, in a few cases, exceed those of native enzymes. We have also provided an outlook on the remaining challenges in the field and future directions that will allow for a deeper understanding of the secondary coordination sphere a deeper understanding of the secondary coordintion sphere to be gained, and in turn to guide the design of a broader and more efficient variety of ArMs.

Insights into the Activation Mode of α-Carbonyl Sulfoxonium Ylides in Rhodium-Catalyzed C-H Activation: A Theoretical Study

A computational study has been performed to investigate the mechanism of RhIII -catalyzed C-H bond activation using sulfoxonium ylides as a carbene precursor. The stepwise and concerted activation modes for sulfoxonium ylides were investigated. Detailed theoretical results showed that the favored stepwise pathway involves C-H bond activation, carbonization, carbene insertion, and protonation. The free energy profiles for dialkylation of 2-phenylpyridine were also calculated to account for the low yield of this reaction. Furthermore, the substituent effect was elucidated by comparing the energy barriers for the protonation of meta- and para-substituted sulfoxonium ylides calculated by density functional theory.

Artificial Metalloproteins: At the Interface between Biology and Chemistry

Artificial metalloproteins (ArMs) have recently gained significant interest due to their potential to address issues in a broad scope of applications, including biocatalysis, biotechnology, protein assembly, and model chemistry. ArMs are assembled by the incorporation of a non-native metallocofactor into a protein scaffold. This can be achieved by a number of methods that apply tools of chemical biology, computational de novo design, and synthetic chemistry. In this Perspective, we highlight select systems in the hope of demonstrating the breadth of ArM design strategies and applications and emphasize how these systems address problems that are otherwise difficult to do so with strictly biochemical or synthetic approaches.

Rhodaelectro-Catalyzed peri-Selective Direct Alkenylations with Weak O-Coordination Enabled by the Hydrogen Evolution Reaction (HER)

Direct C-H functionalizations by electrocatalysis is dominated by strongly coordinating N(sp2 )-directing groups. In sharp contrast, direct electrocatalytic transformations of weakly-coordinating phenols remain underdeveloped. Herein, electrooxidative peri C-H alkenylations of challenging 1-naphthols were achieved by versatile rhodium(III) catalysis via user-friendly constant current electrolysis. The rhodaelectrocatalysis employed readily-available alkenes and a protic reaction medium and features ample scope, good functional group tolerance and high site- and stereoselectivity. The strategy was successfully applied to high-value, nitrogen-containing heterocycles, thereby providing direct access to uncommon heterocyclic motifs based on the dihydropyranoquinoline skeleton.