Search

A novel methodology for the synthesis of 2-pyridones bearing a 2-pyridyl group on nitrogen and carbon atoms, starting from 2-bromopyridines, was developed employing a simple Ru(II)–KOPiv–Na2CO3 catalytic system. Unsubstituted 2-bromopyridine was successfully converted to the penta-heteroarylated 2-pyridone product using this method. Preliminary mechanistic studies revealed a possible synthetic pathway leading to the multi-heteroarylated 2-pyridone products, involving consecutive oxygen incorporation, a Buchwald–Hartwig-type reaction, and C–H bond activation. [ABSTRACT FROM AUTHOR]

A ruthenium‐catalyzed reductive amination via asymmetric transfer hydrogenation (ATH) has been used to perform an efficient dynamic kinetic resolution (DKR) of N‐aryl 2‐formyl pyrroles decorated with a phosphine moiety positioned at the ortho' position. The strategy relies on the labilization of the stereogenic axis in the substrate facilitated by a transient Lewis acid‐base interaction (LABI) between the carbonyl carbon and the phosphorus center. The reaction features broad substrate scope of aliphatic amines and N‐aryl pyrrole scaffolds, and proceeds under very mild conditions to afford P,N atropisomers in good to high yields and excellent enantioselectivities (up to 99 % ee) for both diphenyl and dicyclohexylphosphino derivatives. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: An asymmetric isomerization/intramolecular coupling reaction of allylic alcohols to synthesize chiral dihydrocoumarins was successfully accomplished through ruthenium catalysis. This method demonstrates a wide substrate applicability, excellent tolerance for various functional groups, and good enantioselectivities (up to 90% ee). It provides a convenient pathway to produce a diverse range of structurally distinct chiral dihydrocoumarins in good efficiency. [ABSTRACT FROM AUTHOR]

Transition metal‐catalyzed C−H arylation polymerization (CHAP) is an attractive tool for constructing π‐conjugated polymers in a sustainable manner. However, the existing methods primarily rely on palladium catalysis, which usually entails harsh reaction conditions and branching/cross‐linking. Here we report the first example of an ambient‐temperature ruthenium‐catalyzed C−H arylation polymerization induced by visible light irradiation. The present polymerization can produce various meta‐ and para‐linked polymers in excellent yields with high molecular weights. The remarkable feature of our mild reaction platform is represented by high chemoselectivity, leading to polymers that are otherwise inaccessible under conventional reaction conditions at high temperatures. [ABSTRACT FROM AUTHOR]

Ruthenium(II)‐catalyzed synthesis of π‐conjugated fused imidazo[1,5‐a]quinolin‐2‐ium derivatives have been achieved via C−H activation of quinoline‐functionalized NHC (NHC=N‐heterocyclic carbene) and oxidative coupling with internal alkynes. The reaction occurred with high efficiency, broad substrate scope, tolerates a wide range of functional groups and utilized into a gram‐scale. Synthetic applications of the coupled product have been exemplified in the late‐stage derivatization of various highly functionalized scaffolds. Moreover, most of the annulated products exhibit intense fluorescence and have potential applications in optoelectronic devices. Mechanistic studies have provided insights into the spectroscopic characterization of key five‐membered ruthenacycle intermediate and Ru(0) sandwich species. Based on several control experiments, deuterium‐kinetic isotope effect, and thermodynamic activation parameters the mechanistic finding demonstrated that fused imidazo‐[1,5‐a]quinolin‐2‐ium C(2)−H bond cleavage is the rate‐determining step and ruling out the possibility of reductive elimination for controlling the rate of reaction. [ABSTRACT FROM AUTHOR]

Unusual direction of the C–H arylation of 2-(het)aryl[1,2,4]triazolo[1,5-a]pyrimidines with (het)aryl halides under catalysis by ruthenium(II) complexes has been revealed. The reaction involved activation of the C7–H bond rather than the Cα–H bond of the (het)aryl substituent at C2 of the triazolopyrimidine core. The arylation of 2-substituted [1,2,4]triazolo[1,5-a]pyrimidines with (het)aryl bromides afforded a series of 7-(het)aryl derivatives in good yields. [ABSTRACT FROM AUTHOR]

The prospect of developing methods to control the reactivity of metal(oxo) holds appeal for both synthetic and bioinorganic chemistry. In this study, we observed that carboxylic acids enhance reactivity in C−H oxidation by forming hydrogen bonds with the oxo ligand, thereby increasing the basicity and electrophilicity of the oxo intermediate. Additionally, we discovered that H‐dicarboxylate ligands, such as oxalate, malonate, and maleate, significantly improve the catalyst turnover frequency (up to 760/h) in unactivated C(sp3)−H oxidation. Furthermore, the addition of maleic acid was also found to activate Fe and Mn(pdp)‐catalysed C−H oxygenation. Notably, Ru(bpga)(H‐maleate)23‐catalyzed C−H functionalization exhibited a broad functional group tolerance, including bromine, hydroxyl, benzoate, nitro, nitryl, sulfonate, imide, sulfonylamide, and carbamate, yielding up to 98% in a site‐ and chemoselective manner with only 0.1–2.0 mmol% loading. [ABSTRACT FROM AUTHOR]

C−C bond forming reaction of ketone with aldehyde is well‐studied for the synthesis of α, β‐unsaturated ketones, however, the reaction with two different ketones to unsaturated carbonyl compound has not yet been systematically studied. Probably due to the relatively low reactivity of ketones as electrophiles (aldol acceptors), its propensity for retro‐aldol reaction. The reactions often suffer from unsatisfactory chemoselectivity (self‐ vs. crossed aldol products) and regioselectivity (thermodynamic vs. kinetic enolate). In this quest, we report here for the first time selective cross‐coupling reaction of ketones to β‐branched β, γ‐unsaturated ketones by using ruthenium catalysis. Interestingly, single crossed aldol condensation products are formed even in reactions where a mixture of products is possible. Reaction is highly chemoselective, regioselective and produces H2O as the only byproducts making the protocol environmentally benign. Method is compatible with a wide variety of sensitive functional group and applicable for even problematic aliphatic ketones as substrates. Notably, acetone was found as a three‐carbon feedstock for the syntheses of simple β, γ‐unsaturated ketone compounds. The process can further be extended to the gram‐scale reaction and late‐stage functionalization of natural products. With the help of DFT calculations, several control experiments, and deuterium‐labeling experiments, the mechanistic finding demonstrated that initial aldol‐condensation of ketones to a β, β‐disubstituted α, β‐unsaturated ketone, which further isomerizes to a β, γ‐ unsaturated ketone via η3‐allyl ruthenium complex. [ABSTRACT FROM AUTHOR]

A novel methodology for the synthesis of 2-pyridones bearing a 2-pyridyl group on nitrogen and carbon atoms, starting from 2-bromopyridines, was developed employing a simple Ru(II)–KOPiv–Na2CO3 catalytic system. Unsubstituted 2-bromopyridine was successfully converted to the penta-heteroarylated 2-pyridone product using this method. Preliminary mechanistic studies revealed a possible synthetic pathway leading to the multi-heteroarylated 2-pyridone products, involving consecutive oxygen incorporation, a Buchwald–Hartwig-type reaction, and C–H bond activation.

The article discusses the use of benzoxazole and benzothiazole as directing groups for palladium- and ruthenium-catalyzed C-H arylation reactions. The authors explore different reaction conditions and catalysts to achieve selective arylation of these compounds. They also investigate the effects of substituents on the aryl unit and the benzoxazole/benzothiazole moiety. The document provides valuable information for researchers interested in the synthesis and functionalization of heterocyclic compounds. Additionally, the document includes experimental procedures and characterization data for specific compounds synthesized using the methods discussed. [Extracted from the article]

A class of 2‐hydroxypyridine based ligands are explored to achieve enhanced catalytic activity for ortho‐C−H bond activation/arylation reaction over [(η6‐p‐cymene)RuCl2]2 catalyst in water. Extensive studies using a series of substituted 2‐hydroxypyridine based ligands (L1–L6) inferred that 5‐trifluoromethyl‐2‐hydroxypyridine (L6) exhibited favorable effects to enhance the catalytic activity of Ru(II) catalyst for ortho C−H bond arylation of 2‐phenylpyridine by 8 folds compared to those performed without ligands. The (η6‐p‐cymene)Ru – L6 system also exhibited enhanced catalytic activity for ortho C−H bond arylation of 2‐phenylpyridine using a variety of aryl halides. NMR and mass investigations inferred the presence of several ligand coordinated Ru(II) species, suggesting the involvement of these species in C−H bond activation reaction. Further in concurrence with the experimental findings, the density functional theory (DFT) calculations also evidenced the prominent role of 2‐hydroxypyridine based ligands in Ru(II) catalyzed C−H bond arylation of 2‐phenylpyridine with lower energy barrier for the C−H activation step. [ABSTRACT FROM AUTHOR]

Keywords: ruthenium catalysis; mandelic acids; alkynes; annulation; isocoumarins EN ruthenium catalysis mandelic acids alkynes annulation isocoumarins 2005 2010 6 10/09/23 20231024 NES 231024 Graph Isocoumarins are an important class of natural lactones, and their skeletal structure is an important part of many active pharmaceutical ingredients. At present, the major methods for synthesizing isocoumarins include (1) the cyclization reaction of I ortho i -halogen-substituted benzoic acids or their esters or amides with 1,3-diketones or internal alkynes; [10][11][12] and (2) the internal cyclization reaction of I ortho i -alkenyl- or alkynyl-substituted benzoic acids or their esters. The reactions of benzaldehydes B 5 b and benzoic acids B 6 b with B 2a b proceeded when the amount of Cu(OAc) SB 2 sb -H SB 2 sb O was increased to 1.5 equivalents and the reaction time was shortened to ten hours. Ruthenium(II)-Catalyzed C-H Annulation of Mandelic Acids with Internal Alkynes to Construct Isocoumarins. [Extracted from the article]

Selective dehydrogenative silylation is one of the most valuable tools for synthesizing organosilicon compounds. In this study, a regio- and stereoselective ruthenium-catalyzed dehydrogenative intermolecular silylation was firstly developed to access (E)-alkenyl silyl-ether derivatives and silyl-ether heterocycles with good functional group tolerance. Furthermore, two pathways for RuH2(CO)(PPh3)3/NBE-catalyzed dehydrogenative intermolecular silylation of alcohols and alkenes as well as intermolecular silylation of naphthol derivatives were investigated with H2SiEt2 as the hydrosilane reagent. [ABSTRACT FROM AUTHOR]

Keywords: electrochemistry; electrocatalysis; olefin metathesis; ruthenium catalysis EN electrochemistry electrocatalysis olefin metathesis ruthenium catalysis 1477 1481 5 07/11/23 20230725 NES 230725 Graph Olefin metathesis is one of the most valuable reactions in organic chemistry for the formation of C=C bonds, as reflected by its widespread application in synthetic chemistry, [1] materials science, [2] and polymer science. Electrochemistry, electrocatalysis, olefin metathesis, ruthenium catalysis. [Extracted from the article]

Herein, an efficient and expedient method was developed for α‐alkylation of aromatic ketones with secondary alcohols to produce β‐disubstituted ketones using phosphine‐free pincer ruthenium complexes as the catalyst. Single α‐alkylated ketone is produced in high yields even in reactions where a mixture of products is possible. Interestingly, challenging substrates such as unsubstituted and nonhindered acetophenone compounds are effectively alkylated under the reaction conditions. The scope of the reaction can span with a verities of aliphatic, cyclic, and acyclic secondary alcohols. Functionalization of a cholesterol molecule is also possible under the reaction conditions. Substitution on cyclohexyl ring afforded products as a mixture of diastereoisomers, wherein the major isomer is found as 1,4‐cis conformation of the cyclohexyl ring. Origin of the cis stereoselectivity in the alkylation process was explored by DFT calculation study. Mechanistic studies reveal that the dehydrogenation of alcohols follows a proton shuttle‐type of TS, involvement of cross‐aldol condensation and borrowing hydrogen catalysis. Notably, this selective, catalytic C−C bond forming reaction proceeds with low catalyst load, catalytic amount of base under air and produces H2O as the only byproduct, making the process environmentally benign and atom efficient. [ABSTRACT FROM AUTHOR]

A novel Ru(phen)3Cl2‐catalyzed free‐radical chlorotrifluoromethylation reaction of unactivated olefins was investigated. Substituted 8‐aminoquinoline‐derived inert enamides were reacted with the Togni regent to afford a broad range of Cl‐containing trifluoromethyl derivatives in good yields. The reaction proceeded at 90 °C and experimental result shows that the chlorine source of the products originated from LiCl. [ABSTRACT FROM AUTHOR]

Glycosyl anomeric radical addition reactions have been well‐explored and proved efficient for the C‐alkyl glycosides synthesis, but multicomponent Domino transformations for the rapid and controllable construction of structurally diversified C‐alkyl glycosides in a single step are still rare. In contrast, we, herein, report a ruthenium(II)‐catalyzed Domino meta‐C−H ethyl glycosylation, enabling the construction of challenging meta‐C‐alkyl glycosides. Our ruthenium(II) catalysis was reflected by the mild reaction condition, exclusive meta‐site selectivity and high levels of anomeric selectivity. In addition, the ruthenium(II)‐catalyzed Domino meta‐C−H glycosylation allowed for the synthesis of versatile 1,2‐trans‐C‐alkyl glycosides with commercially available vinyl arenes, acrylates and easily accessible glycosyl bromides. [ABSTRACT FROM AUTHOR]

A highly efficient strategy to construct benzo[d][1,3]diazepines via selective C−H bond activation of N‐aryl amidines and coupling with alkynyl cyclobutyl acetates was achieved successfully by RuII‐catalyzed [5+2] cyclization. This protocol features excellent regioselectivity, wide substrate tolerance, mild reaction conditions, which might be potentially applied in the discovery of lead compounds for the developing new drugs. [ABSTRACT FROM AUTHOR]

SNS-based ruthenium pincer catalysts were applied in a Guerbet condensation reaction of primary alcohols to give β-alkylated dimeric alcohols in good yields. The ability of these complexes to convert ethanol into butanol was also investigated. The work was then extended toward the C-alkylation of secondary alcohols with primary alcohols to give α-alkylated ketones. Several control experiments showed the involvement of borrowing hydrogen in the protocol. [ABSTRACT FROM AUTHOR]

A group of thirteen catalysts of type [Ru(Cp/Cp*)(P–P)(MeCN)]PF6 , bearing cooperative or noncooperative bidentate phosphine ligands, were evaluated for the catalytic acceptorless dehydrogenation of indoline. The systematic comparison revealed that the optimal cooperative catalyst structure included a Cp ancillary ligand, and an N , N -disubstituted P , P -disubstituted 1,5-diaza-3,7-diphosphacyclooctane ligand, denoted as (PR2 NR′2). A cooperative complex bearing a PPh2 NPh2 ligand exhibited about a twofold longer lifetime than a noncooperative analogue with (diphenylphosphino)ethane (dppe) as the supporting bisphosphine ligand. The cooperative catalyst effectively dehydrogenated a range of indoline substrates to give substituted indoles. [ABSTRACT FROM AUTHOR]

Abstract A novel Ru(phen)3Cl2‐catalyzed free‐radical chlorotrifluoromethylation reaction of unactivated olefins was investigated. Substituted 8‐aminoquinoline‐derived inert enamides were reacted with the Togni regent to afford a broad range of Cl‐containing trifluoromethyl derivatives in good yields. The reaction proceeded at 90 °C and experimental result shows that the chlorine source of the products originated from LiCl.

The ruthenium(II)‐catalyzed reaction of aniline derivatives with allylamines was carried out, affording 2‐methylindoles via C−H/C−N bond activation. 4,5‐Dimethyl pyrimidin‐2‐yl group attached on the nitrogen atom of anilines is the most effective directing group and N‐allyl‐4‐fluoro‐N‐methylaniline is the optimal allylamine. The cyclization products were obtained in 16% to 96% yields. The method does not require external oxidant. A possible mechanism is proposed. [ABSTRACT FROM AUTHOR]

Easily accessible via a simple esterification of alcohols with formic acid, alkyl formates are used as a novel class of transfer hydroalkylation reagents, CO2 acting as a traceless linker. As a proof‐of‐concept, their reactivity in the transfer hydroalkylation of imines is investigated, using a ruthenium‐based catalyst and LiI as promoter to cleave the C−O σ‐bond of the formate scaffold. Providing tertiary amines, the reaction displays a divergent regioselectivity compared to previously reported transfer hydroalkylation strategies. [ABSTRACT FROM AUTHOR]

Iodide‐bound ruthenium‐JOSIPHOS complexes catalyze the redox‐neutral C−C coupling of primary alcohols with methylallene (1,2‐butadiene) or 1,3‐butadiene to form products of anti‐crotylation with good to excellent levels of diastereo‐ and enantioselectivity. Distinct from other methods, direct crotylation of primary alcohols in the presence of unprotected secondary alcohols is possible, enabling generation of spirastrellolide B (C9–C15) and leucascandrolide A (C9–C15) substructures in significantly fewer steps than previously possible. [ABSTRACT FROM AUTHOR]

Selective dehydrogenative silylation is one of the most valuable tools for synthesizing organosilicon compounds. In this study, a regio- and stereoselective ruthenium-catalyzed dehydrogenative intermolecular silylation was firstly developed to access (E)-alkenyl silyl-ether derivatives and silyl-ether heterocycles with good functional group tolerance. Furthermore, two pathways for RuH2(CO)(PPh3)3/NBE-catalyzed dehydrogenative intermolecular silylation of alcohols and alkenes as well as intermolecular silylation of naphthol derivatives were investigated with H2SiEt2 as the hydrosilane reagent.

A mechanochemical asymmetric transfer hydrogenation (ATH) of diketones in the presence of a ruthenium complex under solvent-free conditions was developed to provide chiral 1,3-diol derivatives. This protocol benefits from rapid reaction kinetics, no use of solvents, and excellent enantioselectivity. In addition, the mechanochemical ATH reaction can easily be performed on a gram scale. [ABSTRACT FROM AUTHOR]

Ruthenium(II)-catalyzed enantioselective C–H functionalization reactions of sulfoximines with sulfoxonium ylides are described. The combination of [RuCl2 (p -cymene)]2 and a pseudo- C 2-symmetric binaphthyl monocarboxylic acid furnished the S -chiral products in 76:24 to 92:8 er. [ABSTRACT FROM AUTHOR]

The prevalence of C‐aryl glycosides in biologically active natural products and approved drugs has long motivated the development of efficient strategies for their selective synthesis. Cross‐couplings have been frequently used, but largely relied on palladium catalyst with prefunctionalized substrates, while ruthenium‐catalyzed C‐aryl glycoside preparation has thus far proven elusive. Herein, we disclose a versatile ruthenium(II)‐catalyzed meta‐C−H glycosylation to access meta‐C‐aryl glycosides from readily available glycosyl halide donors. The robustness of the ruthenium catalysis was reflected by mild reaction conditions, outstanding levels of anomeric selectivity and exclusive meta‐site‐selectivity. [ABSTRACT FROM AUTHOR]

Potassium alkoxide was found to be a highly active catalyst for the nucleophilic trifluoromethylation of carbonyl compounds. The catalytic system was successfully applied to the reactions of both aldehydes and ketones, affording the corresponding trifluoromethylated products in high yields at low catalyst loadings (0.1–0.01 mol%) in several solvents, such as THF, toluene, and CH2 Cl2. In addition, the potassium salt of a Ru(II) complex bearing an (S)-2,2′-bis[bis(3,5-dimethylphenyl)phosphinyl]-1,1′-binaphthalene [(S)-XylBINAP] ligand and two l -threoninate ligands, prepared in situ, catalyzed the enantioselective trifluoromethylation of aromatic aldehydes, although the ee values were not satisfactory (less than 20%). [ABSTRACT FROM AUTHOR]

A ruthenium-catalyzed reductive amination via asymmetric transfer hydrogenation (ATH) has been used to perform an efficient dynamic kinetic resolution (DKR) of N-aryl 2-formyl pyrroles decorated with a phosphine moiety positioned at the ortho' position. The strategy relies on the labilization of the stereogenic axis in the substrate facilitated by a transient Lewis acid-base interaction (LABI) between the carbonyl carbon and the phosphorus center. The reaction features broad substrate scope of aliphatic amines and N-aryl pyrrole scaffolds, and proceeds under very mild conditions to afford P,N atropisomers in good to high yields and excellent enantioselectivities (up to 99 % ee) for both diphenyl and dicyclohexylphosphino derivatives., (© 2024 The Author(s). Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Disclosed here is the first geminal (gem‐) hydroborative cyclization of enynes. Different from known hydroborative cyclizations, this process adds hydrogen and boron to the same position, leading to a new reaction mode. With [Cp*RuCl]4 as catalyst, a range of gem‐hydroborated bicyclic products bearing a cyclopropane unit could be rapidly assembled from simple enyne substrates. Control experiments and density functional theory (DFT) calculations provided important insights into the reaction mechanism. Notably, two major competing pathways may operate with substrate‐dependence. 1,6‐Enynes favor initial oxidative cyclometalation to form a ruthenacyclopentene intermediate prior to engaging hydroborane, while other enynes (e.g. 1,7‐enynes) that lack strong propensity toward cyclization prefer initial alkyne gem‐(H,B)‐addition to form an α‐boryl ruthenium carbene followed by intramolecular olefin cyclopropanation. This process also represents the first ruthenium‐catalyzed enyne hydroborative cyclization. [ABSTRACT FROM AUTHOR]

The development of catalytic tools for the late‐stage modification of amino acids within a peptide framework is a challenging task of capital importance. Herein, we report a Ru‐catalyzed C(sp2)−H hydroxylation of a collection of Tyr‐containing di‐ and tripeptides featuring the use of a carbamate as a removable directing group and PhI(OCOCF3)2 (PIFA) as oxidant. This air‐compatible tagging technique is reliable, scalable and provides access to L‐DOPA (L‐3,4‐dihydroxyphenylalanine) peptidomimetics in a racemization‐free fashion. Density Functional Theory calculations support a Ru(II)/Ru(IV) catalytic cycle. [ABSTRACT FROM AUTHOR]

A selective and high‐rate Ru‐catalyzed cross‐metathesis reaction of alkenes with vinylimidazole is disclosed. Cross‐metathesis is known to operate less efficiently on N‐heterocycles, but through optimization by means of statistical experimental design and multiple regression, optimal reaction conditions were identified that allowed for consistent high‐yields without the need of overly complicated set‐ups or additives. The method was tested on a series of terminal alkene reagents with a variety of different functional groups and it provides the corresponding target molecules in good to high yields. [ABSTRACT FROM AUTHOR]

A triazole-directed direct C–H arylation of arenes with electron-deficient aryl halides or a synthetically useful pyrimidyl chloride was achieved through ruthenium catalysis. Our novel strategy provides operationally simple and environmentally benign access to highly functionalized hetarenes, avoiding the use of strong organometallic bases. Detailed studies revealed a significant effect of the phosphine ligand, thereby permitting the reaction to occur with excellent levels of chemo- and position selectivity. [ABSTRACT FROM AUTHOR]

A total synthesis of resolvin T4 was achieved by connecting three intermediates by Wittig reactions. The enal in the C1–C10 part was constructed through reduction of a propargylic alcohol with Red-Al followed by oxidation. The enal moiety in the C11–C16 part was synthesized by a ring-opening reaction of a silyl epoxide followed by a Peterson elimination. The chiral centers at C7 and C13 were constructed by ruthenium-catalyzed asymmetric transfer hydrogenation. [ABSTRACT FROM AUTHOR]

3-Alkenylindoles are biologically and medicinally very important compounds, and their syntheses have received considerable attention. Herein, we report the synthesis of 3-alkenylindoles via a regioselective alkenylation of indoles, catalysed by a ruthenium nanocatalyst (RuNC). The reaction tolerates several electron-withdrawing and electron-donating groups on the indole moiety. Additionally, a “robustness screen” has also been employed to demonstrate the tolerance of several functional groups relevant to medicinal chemistry. With respect to the Ru nanocatalyst, it has been demonstrated that it is recoverable and recyclable up to four cycles. Also, the catalyst acts through a heterogeneous mechanism, which has been proven by various techniques, such as ICPMS and three-phase tests. The nature of the Ru nanocatalyst surface has also been thoroughly examined by various techniques, and it has been found that the oxides on the surface are responsible for the high catalytic efficiency of the Ru nanocatalyst.

Synthetic transformations of otherwise inert C–H bonds have emerged as a powerful tool for molecular modifications during the last decades, with broad applications towards pharmaceuticals, material sciences, and crop protection. Consistently, a key challenge in C–H activation chemistry is the full control of site-selectivity. In addition to substrate control through steric hindrance or kinetic acidity of C–H bonds, one important approach for the site-selective C–H transformation of arenes is the use of chelation-assistance through directing groups, therefore leading to proximity-induced ortho -C–H metalation. In contrast, more challenging remote C–H activations at the meta - or para -positions continue to be scarce. Within this review, we demonstrate the distinct character of ruthenium catalysis for remote C–H activations until March 2021, highlighting among others late-stage modifications of bio-relevant molecules. Moreover, we discuss important mechanistic insights by experiments and computation, illustrating the key importance of carboxylate-assisted C–H activation with ruthenium(II) complexes. 1 Introduction 2 Stoichiometric Remote C–H Functionalizations 3 meta -C–H Functionalizations 4 para -C–H Functionalizations 5 meta -/ ortho -C–H Difunctionalizations 6 Conclusions [ABSTRACT FROM AUTHOR]

A new phosphine‐free Ruthenium complex bearing hemilabile thiophene‐based ligand is synthesized for the large‐scale catalytic hydrogenation of carbonyl compounds. The methodology is also applicable for the one‐pot synthesis of various benzhydryl active pharmaceutical ingredients (APIs). [ABSTRACT FROM AUTHOR]

A double‐ligands enabled ruthenium catalyzed C(sp2)−H arylation of dialkyl phosphines is described, which provides a straight access to aryl‐substituted dialkyl phosphine ligands. The combination of 1,3‐diketone and amino acid ligands is essential for this transformation. An important six‐membered cycloruthenium intermediate was successfully isolated and characterized by X‐ray diffraction. Mechanistic studies showed that the 1,3‐diketone promoted the process of oxidative addition of cycloruthenium intermediate. Some of modified CyJohnPhos ligands exhibited highly catalytic activity in palladium catalyzed C−N bond formation. [ABSTRACT FROM AUTHOR]

• Regioselective ruthenium-catalyzed arylation of flavones is reported. • Selective combination of Ru, Ni and Pd-catalyzed coupling reactions are employed. • 5-, 5,8-, 5,7-, 5,6- and 5,7,8-aryl substituted flavones were prepared. • Chrysin confers facility to the employed reactions. The first regioselective ruthenium-catalyzed arylation of flavone-derived compounds is reported. Exploring the molecular structure-reactivity different 5-,5,8-, 5,7-, 5,6- and 5,7,8-aryl substituted flavones were prepared through Ru-, Ni- and Pd-catalyzed coupling reactions with aryl boronic species under regio- and chemoselective approach in moderate to excellent yields. The obtained derivatives were thoroughly characterized by spectroscopic techniques, such as 1H NMR, 13C NMR and HRMS data. The convenient availability of starting natural product chrysin confers facility to the employed reactions which products may find application in pharmaceutical and material science areas. [Display omitted] [ABSTRACT FROM AUTHOR]

• Ru-catalyzed high chemoselectivity hydroformylation. • New application of thiazolinyl-based phosphine in carbonylation. • Wide substrates scope including linear, internal and cyclic olefins in hydroformylation. A catalytic system comprised of Ru 3 (CO) 12 , thiazolinyl-based phosphine (L1), and HBF 4 enables the efficient hydroformylation, which the tautomer L1b is more favorable for the occurrence of the reaction as well as the additive HBF 4 is beneficial for the formation of ruthenium hydrogen active species. The formation and stabilization of the critical Ru-complex intermediates were verified by the DFT calculations. The hydroformylation proceeds with high chemical selectivity especially for the linear, internal and cyclic olefins (conversion up to 99 %, selectivity of aldehysdes up to 92 %). [Display omitted] [ABSTRACT FROM AUTHOR]

A commercially available ruthenium (II) PNP type pincer catalyst (Ru-Macho) promotes formation of amides and imines from alcohols and amines via an acceptorless dehydrogenation pathway. The formation of secondary amides, tertiary amides, and secondary ketimines occurs in yields ranging from 35%-95%.

An efficient and straightforward synthesis of aryl‐substituted biarylphosphines via unprotected amino acid‐accelerated ruthenium‐catalyzed P‐directed ortho‐C−H arylation reaction is described. This protocol utilized commercial and inexpensive (hetero)aryl chlorides as efficient arylating reagents under solvent‐free reaction conditions. Notably, diverse aryl bromides were also effective for this transformation. With the protocol, a wide variety of mono‐arylated biarylphosphines were obtained in moderate to high yields and excellent selectivity. Moreover, the aryl‐substituted phosphine exhibited higher catalytic performance than its precursor and other substituted phosphines in palladium‐catalyzed Suzuki coupling. [ABSTRACT FROM AUTHOR]

Amines are a ubiquitous class of compounds found in a variety of functional organic building blocks. Within the past years, hydrogen autotransfer catalysis has evolved as a new concept for the synthesis of amines. A through understanding of the mechanism of these reactions is necessary to design optimal catalysts. We investigate secondary amine formation catalyzed by a NNNN(P)Ru‐complex and provide understanding on the three reaction steps involved. We find that the ligand has to open one coordination site in order to allow the formation of a metal hydride intermediate. In a second step, a condensation reaction, which could also happen uncatalyzed in solution, is significantly enhanced by the presence of the ruthenium complex. The back‐transfer of the hydride to the substrate in a third step regenerates the catalyst. [ABSTRACT FROM AUTHOR]

Enyne metathesis reactions are powerful tools for the preparation of a wide range of synthetic and natural chemical substances with increasing efficiency and environmental sustainability. The driving force of the reaction is the formation of a stable conjugated system, i.e., a diene, which through further functionalization steps can be used for the construction of skeletally complex molecular architectures. These concepts are exploited to design cascade reaction sequences, where multiple rings can be formed in a one-pot fashion by combining metathetic protocols with various chemical transformations. The strong correlation between synthetic organic chemistry and medicinal chemistry prompted us to review the most notable approaches for the synthesis of biologically relevant compounds via enyne metathesis-based one-pot processes. With the aim to provide a modern and practical overview, by taking into consideration the scientific literature on this topic, we have focused the majority of our attention on the research performed in the last decade. This review covers the literature from 2003 to 2020. 1 Introduction 2 Ethylene-Mediated Processes 3 RCEYM/CM and CEYM/RCM Processes 4 Enyne Metathesis/Diels–Alder-Based Processes 5 RCM of Dienynes 6 RCM of Tethered Dienynes 7 Relay Metathesis 8 Ring-Rearrangement Metathesis 9 RCEYM/Transition-Metal-Catalyzed C–C Bond-Forming Processes 10 Conclusions 11 List of Acronyms [ABSTRACT FROM AUTHOR]

Herein, we disclose a ruthenium‐catalyzed regioselective β‐C(sp3)−H bond functionalization on the piperazine core using aldehydes as alkylating agents. The present transformation appears to go through the dehydrogenation of the piperazine to propagate to enamine in situ, followed by nucleophilic addition to the aldehyde and hydrogenation to result in the regioselective β‐C(sp3)−H alkylation. A variety of aromatic, heteroaromatic, aliphatic aldehydes were employed for the C‐3 alkylation of N‐alkyl‐N′‐p‐nitrophenyl substituted piperazines. [ABSTRACT FROM AUTHOR]

Exploration of new materials for oxygen reduction reaction has long been a major area of research in heterogeneous catalysis. As the currently available oxygen reduction catalysts have not achieved the optimal efficiency, search for alternative resources is a continuing effort. Realizing the wide acceptance of ruthenium as a promising catalyst for various catalytic reactions, we have investigated the plausibility of Ru to perform in the bulk as well as nanoparticle forms as an efficient oxygen reduction reaction catalyst. Two nanoclusters with face-centred and hexagonal symmetry were scrutinized for ORR activity along with Ru(111) and Ru(0001) surfaces as periodic counterparts and compared the activity with Pt(111) surface. We report here that Ru cannot be an alternative to the Pt-based catalysts owing to a high overpotential. The catalytic activity of ruthenium catalysts for ORR was investigated with reference to the recent advancements in the development of ruthenium catalysts for various electrochemical reactions. The results reveal that both the surface as well as nanocluster based ruthenium systems do not outperform the Pt(111) catalyst. [ABSTRACT FROM AUTHOR]

A one-step synthesis of enones from olefins is described. The reaction was performed under visible-light irradiation in the presence of molecular oxygen and a photocatalyst. The reaction proceeded with various types of trisubstituted olefins to give enones in good yields with high regioselectivity. In particular, oxygen- and nitrogen-containing functional groups, heteroaromatic rings, and cyclopropanes were tolerated. Mechanistic studies and previous reports indicated that the active oxygen species generated in the reaction system is singlet oxygen. [ABSTRACT FROM AUTHOR]

A ruthenium-catalyzed [5+1] annulation of 1-(2-aminophenyl)pyrroles with α-carbonyl sulfoxonium ylides is reported. This reaction provides a one-step method for synthesizing pyrrolo[1,2- a ]quinoxaline derivatives under ambient conditions. The system proceeds with a short reaction time and a high functional-group tolerance. Notably, this divergent protocol tolerates β-keto sulfoxonium ylides and can be applied to α-ester sulfoxonium ylides. A preliminary study was made of the mechanism of the reaction, and a reaction pathway is proposed. [ABSTRACT FROM AUTHOR]