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Anilines are ubiquitous in bio‐active compounds and their synthesis can be achieved via metal‐catalyzed cross‐coupling reactions involving aryl halides. We describe an unusual, yet simple, CuII‐catalyzed system for the amination of aryl chlorides in pure aqueous ammonia with 2.5 mol % catalyst loading under non‐inert conditions. Different from previous systems, the reaction proceeds even without an additional organic solvent. Copper(II) sulfate in combination with 4,7‐dimethoxy‐1,10‐phenanthroline enabled the amination of several aryl chlorides containing electron‐neutral, ‐donating and ‐withdrawing groups to the corresponding anilines with good to excellent yields. The upscaling potential of the procedure has been shown by the synthesis at 50 mmol scale. The reaction proceeds as one of the rare cases of a CuII‐assisted coupling, in contrast to the typical CuI−CuIII intermediates postulated for most Ullmann‐type coupling reactions. The copper(II) center allows for a nucleophilic substitution pathway, enabled by the deprotonation of coordinated ammonia. [ABSTRACT FROM AUTHOR]

We here report a catalytic strategy to enable the decarboxylative allylic amination of vinyl cyclic carbonates using various aliphatic and nucleophilic amines. The use of a protic medium and chelating diphosphine ligands are the main drivers towards chemoselective allylic amine formation, thereby minimizing undesired ligand‐driven complex speciation and aminolysis of the involved substrate. This improved approach amplifies the repertoire of allylic amine synthons that can be prepared from a variety of substrate combinations. [ABSTRACT FROM AUTHOR]

Nucleophilic phosphine-catalyzed annulations are recognized as practical and powerful tools for synthesizing various cyclic compounds. Phosphine acceptors play a key role in nucleophilic phosphine catalysis. The design and synthesis of new phosphine acceptors that are able to introduce new zwitterionic intermediates with new reactivities into phosphine-catalyzed annulations is highly desirable. We recently applied proton-shift principles in the design of new phosphine acceptors, and we synthesized several new acceptors. With the use of these acceptors, we have developed several novel phosphine-catalyzed annulation reactions. In this account, we present a brief introduction to the design and application of a series of acidic-hydrogen-tethered electron-deficient acceptors for phosphine-catalyzed annulation reactions, categorized according to the type of atom (N–H, O–H, C–H) to which the acidic hydrogen is bound. 1 Introduction 2 Phosphine Acceptors Tethered with an Acidic N–H Group 3 Phosphine Acceptors Tethered with an Acidic O–H Group 4 Phosphine Acceptors Tethered with an Acidic C–H Group 5 Conclusions [ABSTRACT FROM AUTHOR]

The one‐step synthesis of tetra‐substituted benzenes was accomplished via gold‐catalyzed diyne‐ene annulation. Distinguished from prior modification methods, this novel strategy undergoes formal [3+3] cyclization, producing polysubstituted benzenes with exceptional efficiency. The critical factor enabling this transformation was the introduction of amides, which were reported for the first time in gold catalysis as covalent nucleophilic co‐catalysts. This interesting protocol not only offers a new strategy to achieve functional benzenes with high efficiency, but also enlightens potential new reaction pathways within gold‐catalyzed alkyne activation processes. [ABSTRACT FROM AUTHOR]

The high utility of halogenated organic compounds has prompted the development of numerous transformations that install the carbon‐halogen motif. Halogen functionalities, deemed as "functional and functionalizable" molecules due to their capacity to modulate diverse internal properties, constitute a pivotal strategy in drug discovery and development. Traditional routes to these building blocks have commonly involved multiple steps, harsh reaction conditions, and the use of stoichiometric and/or toxic reagents. With the emergence of solid halogen carriers such as N‐halosuccinimides, and halohydantoins as popular sources of halonium ions, the past decade has witnessed enormous growth in the development of new catalytic strategies for halofunctionalization. This review aims to provide a nuanced perspective on nucleophilic activators and their roles in halogen activation. It will highlight critical discoveries in effecting racemic and asymmetric variants of these reactions, driven by the development of new catalysts, activation modes, and improved understanding of chemical reactivity and reaction kinetics. [ABSTRACT FROM AUTHOR]

Detailed quantum‐chemical calculations have been carried out to understand both the origin of the catalysis in the urea‐catalyzed nucleophilic ring‐opening of nitrocyclopropanes and the acceleration induced by the presence of an internal Lewis acid in the catalyst. To this end, the mode of activation of these ureas is quantitatively analyzed in detail by means of the Activation Strain Model of reactivity in combination with the Energy Decomposition Analysis method. It is found that the presence of the Lewis acid in the urea further enhances the interaction between the reactants, by increasing both the electrostatic and orbital attractions, which translates into a reduced activation barrier. This insight is also used to assess the impact of the nature of the Lewis acid on the transformation, facilitating the rational design of more active catalysts. [ABSTRACT FROM AUTHOR]

In light of the small ring strain of five/six-membered cyclic ethers, constructing complex molecules via ring-opening reactions has consistently been a highly challenging topic in organic synthesis. Induced by Lewis acids, the charge redistribution in cyclic ethers forms oxonium ylide intermediates, thereby activating the C–O bond and subsequently facilitating nucleophilic attack for ring opening. In recent years, a variety of novel Lewis acids, encompassing those with new metal centers and frustrated Lewis pairs (FLPs), have been effectively utilized to induce the formation of oxonium ylides, offering a diverse array of methods for the ring opening of five/six-membered cyclic ethers. This review conveys the extensive application advancements of diverse Lewis acid types for cyclic ether ring-opening reactions over the past two decades, originating from the perspective of the classification of Lewis acids. Furthermore, the substrate applicability and chemical transformation efficiency of these Lewis acids in the ring-opening reactions of cyclic ethers have also been discussed herein. [ABSTRACT FROM AUTHOR]

This review deals with the functionalization of double bonds carried out in the presence of a chiral catalyst exploiting the intramolecular attack to haliranium ions by nucleophilic nitrogen of amides or carbamates prepared from achiral aminoalkenes, and the C–N bonds formation leads to highly enantioenriched nonaromatic heterocycles. A range of protocols are reported, emphasizing the synthesis of many natural and biologically active products of pharmacological interest prepared according to this methodology. [ABSTRACT FROM AUTHOR]

This paper shows a novel oxidative functionalization of α-amino ketones to yield the corresponding α-ketoamides and α-acylimidates. The reaction proceeds via oxygen delivery from water/alcohols in conjunction with an electron acceptor and 4-dimethylaminopyridine (DMAP). Mechanistic study indicates that DMAP exhibits a dual function of nucleophilic catalysis and proton abstraction. [ABSTRACT FROM AUTHOR]

Herein, we describe a general hydrodefunctionalization protocol of alcohols and amines through a common isonitrile intermediate. To cleave the relatively inert C−NC bond, we leveraged dual hydrogen atom transfer (HAT) and photoredox catalysis to generate a nucleophilic boryl radical, which readily forms an imidoyl radical intermediate from the isonitrile. Rapid β‐scission then accomplishes defunctionalization. This method has been applied to the hydrodefunctionalization of both amine and alcohol‐containing pharmaceuticals, natural products, and biomolecules. We extended this approach to the reduction of carbonyls and olefins to their saturated counterparts, as well as the hydrodecyanation of alkyl nitriles. Both experimental and computational studies demonstrate a facile β‐scission of the imidoyl radical, and reconcile differences in reactivity between nitriles and isonitriles within our protocol. [ABSTRACT FROM AUTHOR]

C–N bonds play a critical role in pharmaceutical, agrochemical, and materials sciences, necessitating ever-better methods to forge this linkage. Here we report a simple procedure for direct C(sp3)–H azidation using iron or manganese catalysis and a nucleophilic azide source. All reagents are commercially available, the experimental procedure is simple, and we can use the C–H donor substrate as the limiting reagent, a challenge for many C–H azidation methods. Preliminary experiments are consistent with a hydrogen atom transfer (HAT)/radical ligand transfer (RLT) radical cascade mechanism and a wide variety of substrates can be azidated in moderate to high yields. [ABSTRACT FROM AUTHOR]

We disclose how an N,C,N‐bismuthinidene is able to promote an intramolecular conjugate amination that affords cyclic carbamates in 91–97% yields. The reaction proceeds at room temperature in short reaction times, requiring a remarkably low loading of a bismuth(I) complex (0.1 mol%) without the need of an additional Brønsted base. Preliminary mechanistic studies suggest that the reaction takes place through a polar pathway involving the conjugate addition of the nucleophilic bismuthinidene, followed by an intramolecular aza‐Michael reaction. [ABSTRACT FROM AUTHOR]

With chiral amine (DHQD)2PHAL as nucleophilic catalyst, asymmetric synthesis of enantioenriched 3‐allylindoles was achieved from indolone‐2‐imines and MBH carbonates. Compared with our previous chiral phosphine catalysis, the chiral amine had exactly the opposite effect in terms of enantioselectivity. Importantly, we could obtain each enantiomer by adjusting the catalyst system. [ABSTRACT FROM AUTHOR]

The catalytic potential of organo‐onium iodides as nucleophilic catalysts is aptly demonstrated in the synthesis of cyclic carbonates from epoxides and carbon dioxide (CO2), as a representative CO2 utilization reaction. Although organo‐onium iodide nucleophilic catalysts are metal‐free environmentally benign catalysts, harsh reaction conditions are generally required to efficiently promote the coupling reactions of epoxides and CO2. To solve this problem and accomplish efficient CO2 utilization reactions under mild conditions, bifunctional onium iodide nucleophilic catalysts bearing a hydrogen bond donor moiety were developed by our research group. Based on the successful bifunctional design of the onium iodide catalysts, nucleophilic catalysis using a potassium iodide (KI)‐tetraethylene glycol complex was also investigated in coupling reactions of epoxides and CO2 under mild reaction conditions. These effective bifunctional onium and potassium iodide nucleophilic catalysts were applied to the solvent‐free syntheses of 2‐oxazolidinones and cyclic thiocarbonates from epoxides. [ABSTRACT FROM AUTHOR]

Catalysis by trivalent nucleophilic organophosphines has emerged as an essential tool in organic synthesis. Several new organic transformations promoted by phosphines substantiate and complement the existing synthetic chemistry tools. Mere design of the substrate and reagent combinations has introduced new modes of reactivity patterns, which are otherwise difficult to achieve. These design considerations have led to the rapid build-up of complex molecular entities and laid a solid foundation to synthesise bioactive natural products and pharmaceuticals. This article presents an overview of some of the conceptual advances, including our contributions to nucleophilic organophosphine chemistry. The scope, limitations, mechanistic insights, and applications of these metal-free transformations are discussed elaborately. [ABSTRACT FROM AUTHOR]

The development of novel synthetic methodologies to incorporate fluorine/s or fluoroalkyl group/s into the frameworks of organic molecules has become a highly prioritized research area because such modifications can tune their physiochemical and biological properties. In recent years, nucleophilic phosphine catalysis has been extensively explored to achieve this goal, and significant progress has been made. This review summarizes the methodological advancements of cycloaddition, addition and coupling reactions employing fluorinated building blocks as electrophilic and/or nucleophilic reaction partners under phosphine catalysis to construct structurally and synthetically valuable organofluorine compounds, with special emphasis on the synthetic strategies, proposed reaction mechanisms and synthetic utilities. [ABSTRACT FROM AUTHOR]

The development of catalyst‐free ester‐based covalent adaptable networks (CANs) provides a new approach to achieve milder reaction conditions to reprocess thermoset resins. Despite recent advances, however, accelerating network rearrangements requires the introduction of hydroxyl groups into the network. In this study, disulfide bonds are introduced into the CANs to add new kinetically facile pathways to accelerate network rearrangement. Kinetic experiments using small molecule models of the CANs show that the presence of the disulfide bonds can accelerate transesterification. These insights are applied to synthesize new kinds of poly(β‐hydrazide disulfide esters) (PSHEs) using thioctic acyl hydrazine (TAH) as a precursor for ring‐opening polymerization with the hydroxyl‐free multifunctional acrylates. The PSHE CANs have lower relaxation times (505–652 s) than the polymer containing only β‐hydrazide esters (2903 s). The ring‐opening polymerization of TAH improves the crosslinking density, heating resistance deformation temperature, and UV shielding performance of the PSHEs. Thus, this work provides a practical strategy to reduce the reprocessing temperatures of CANs. [ABSTRACT FROM AUTHOR]

Rechargeable magnesium batteries are attractive candidates for energy storage due to their high theoretical specific capacities, free of dendrite formation and natural abundance of magnesium. However, the development of magnesium secondary batteries is severely limited by the lack of high-performance cathode materials and the incompatibility of electrode materials with electrolytes. Herein, we report the application of CuS nanoflower cathode material based on the conversion reaction mechanism for highly reversible magnesium batteries with boosted electrochemical performances by adjusting the compatibility between the cathode and electrolyte. By applying non-nucleophilic electrolytes based on magnesium bis(hexamethyldisilazide) and magnesium chloride dissolved in the mixed solvent of tetrahydrofuran and N-butyl-N-methyl-piperidinium bis((trifluoromethyl)sulfonyl)imide (Mg(HMDS)2-MgCl2/THF-PP14TFSI) or magnesium bis(trifluoromethanesulfonyl)imide, magnesium chloride and aluminium chloride dissolved in dimethoxyethane (Mg(TFSI)2-MgCl2-AlCl3/DME), the magnesium batteries with CuS nanoflower cathode exhibit a high discharge capacity of ∼207 mAh·g−1 at 100 mA·g−1 and a long life span of 1,000 cycles at 500 mA·g−1. This work suggests that the rational regulation of compatibility between electrode and electrolyte plays a very important role in improving the performance of multi-valent ion secondary batteries. [ABSTRACT FROM AUTHOR]

α‐Alkoxy enones are quite useful building blocks in organic chemistry. The existing methods for syntheses of these compounds remain somewhat limited. Over the past years, nucleophilic phosphine catalysis has emerged as a practical and powerful tool for constructing diverse molecules with the advantages of environmental‐friendly, metal‐free, and mild reaction conditions. Meanwhile, alkynone is easy to prepare, can undergo a variety of reactions, and is a commonly used substrate for organic synthesis. α‐Addition of alcohols to alkynones is a direct way to construct α‐alkoxy enones. In this study, it was delightful to find that using PPh3 (10 mmol %) and 1,1,1,3,3,3‐hexafluoroisopropanol (HFIP) (20 mmol %) could redirect from β‐addition to α‐addition. With this approach, a variety of α‐alkoxy enones could be obtained directly with good yields and regioselectivity. Under optimal conditions, the generality of the reaction was investigated. Substrate scope studies showed that the reaction was well tolerated with many alcohols. Mechanistic study is also demonstrated. [ABSTRACT FROM AUTHOR]

The oxyanionic ring‐opening polymerization of propylene oxide (PO) from an exogenous alcohol activated with benign (complexed) metal‐alkali carboxylates is described. The equimolar mixture of potassium acetate (KOAc) and 18‐crown‐6 ether (18C6) is demonstrated to be the complex of choice for preparing poly(propylene oxide) (PPO) in a controlled manner. In the presence of 18C6/KOAc, hydrogen‐bonded alcohols act as soft nucleophiles promoting the PO SN2 process at room temperature and in solvent‐free conditions while drastically limiting the occurrence of parasitic hydrogen abstraction generally observed during the anionic ROP of PO. The resulting PPO displays predictable and unprecedented molar masses (up to 20 kg mol−1) with low dispersities (ĐM < 1.1), rendering the 18C6/KOAc complex the most performing activator for the oxyanionic polymerization of PO reported to date. Preliminary studies on the preparation of block and statistical copolyethers are also reported. [ABSTRACT FROM AUTHOR]

The catalytic hydrodefluorination (HDF) with a bifunctional azairidacycle using HCOOK was examined for cyano- and chloro-substituted fluoroarenes, including penta- and tetrafluorobenzonitriles, tetrafluoroterephthalonitrile, tetrafluorophthalonitrile, 3-chloro-2,4,5,6-tetrafluoropyridine, and 4-cyano-2,3,5,6-tetrafluoropyridine. The reaction was performed in the presence of a controlled amount of HCOOK with a substrate/catalyst ratio (S/C) of 100 in a 1:1 mixture of 1,2-dimethoxyethane (DME) and H2O at an ambient temperature of 30 °C to obtain partially fluorinated compounds with satisfactory regioselectivities. The C–F bond cleavage proceeded favorably at the para position of substituents other than fluorine, which is in consonance with the nucleophilic aromatic substitution mechanism. In the HDF of tetrafluoroterephthalonitrile and 4-cyano-2,3,5,6-tetrafluoropyridine, which do not contain a fluorine atom at the para position of the cyano group, the double defluorination occurred solely at the 2- and 5-positions, as confirmed by X-ray crystallography. The HDF of 3-chloro-2,4,5,6-tetrafluoropyridine gave preference to the C–F bond cleavage over the C–Cl bond cleavage, unlike the dehalogenation pathway via electron-transfer radical anion fragmentation. In addition, new azairidacycles with an electron-donating methoxy substituent on the C–N chelating ligand were synthesized and served as a catalyst precursor (0.2 mol%) for the transfer hydrogenative defluorination of pentafluoropyridine, leading to 2,3,5,6-tetrafluoropyridine with up to a turnover number (TON) of 418. [ABSTRACT FROM AUTHOR]

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Curcumin is a natural polyphenol with various bioactivities, including anti-tumor, antioxidant, and anti-inflammatory. Despite curcumin's therapeutic benefits, limited water solubility and rapid hydrolytic degradation are important challenges in using of curcumin for clinical applications. Therefore, this report aimed to examine the stability and antioxidant activity of curcumin in different environments and to find out the mechanism of action through which curcumin shows its radical scavenging activity. Results of this study not only indicated that degradation of curcumin is water-dependent but also suggested its degradation mechanism is distinct from general acid/base catalysis and nucleophilic attack of water hydroxyl ion (OH−) had apparently negligible role in rapid hydrolytic degradation of curcumin. We confirmed that curcumin is solely responsible for its antioxidant activity in aqueous media and its degradation is a spontaneous autoxidation. More importantly, curcumin exhibited rapid decomposition in the presence of excessive O2 or free radicals induced by oxidizing agents (TBHP and H2O2) due to its protective potential against oxidative stress. The possible attack site of free radicals in curcumin is in the first step of curcumin degradation, where phenoxyl radical is produced. On the other hand, curcumin degradation and scavenging activity reduced when it entered into the hydrophobic cavity of BSA or casein molecule. Surprisingly, in soybean oil, curcumin showed the weak antioxidant activity compared to TBHQ (as a potent synthetic antioxidant for frying oils), implying that curcumin did not have significant antioxidant potential in oily/hydrophobic environments. Overall, our findings confirmed that curcumin in aqueous buffer is quickly degrades while at the same time scavenging of free radicals. The presented results are novel and might be interesting as the analysis of physicochemistry of curcumin has been gaining importance in view of biological significance. [ABSTRACT FROM AUTHOR]

We herein report a method for the kinetic resolution of racemic 4-hydroxy[2.2]paracyclophane by means of a chiral isothiourea-catalyzed acylation with isobutyric anhydride. This protocol allows for a reasonable synthetically useful s-factor of 20 and provides a novel entry to obtain this interesting planar chiral motive in an enantioenriched manner.

The native chemical ligation reaction of peptide thioesters with cysteinyl peptides is a pivotal chemical process in the production of native or modified peptides and proteins, and well beyond in the preparation of various biomolecule analogs and materials. To benefit from this reaction at its fullest and to access all the possible applications, the experimentalist needs to know the factors affecting its rate and how to control it. This concept article presents the fundamental principles underlying the rate of the native chemical ligation and its homogeneous catalysis by nucleophiles. It has been prepared to serve as a quick guide in the search for an appropriate catalyst. [ABSTRACT FROM AUTHOR]

The synthesis of 6-chloro-(dichloro-, trichloro)methyl-3-R-6,7-dihydro-2H-[1.2.4] triazino[2,3-c]quinazolin-2-ones and their modification under the action of nucleophilic and/or basic reagents are described in this article. It was shown that 6-chloro-(dichloro-, trichloro)methyl-3-R-6,7-dihydro-2H-[1,2,4]triazino[2,3-c]quinazolin-2-ones can be prepared by cyclocondensation of 3-(aminophenyl)-6-R-1,2;4-triazine-5(2W)-ones with chloro-(dichloro-)acetaldehyde or chloral hydrate. The reactivity of the synthesized compounds toward nucleophilic base morpholine and non-nucleophilic base diisopropylethylamine (DIPEA) under different conditions was studied. It was shown that the prepared compounds under the action of morpholine and/or DIPEA can be converted into the products of substitution, elimination or elimination followed by isomerization and substitution. Refluxing of 6-(chloromethyl)-3-R-6,7-dihydro-2 H-[1.2.4] triazino[2,3-c]quinazoline-2-ones with equimolar quantity of morpholine and 10% excess of DIPEA in ethylene glycol monoethyl ether (EGEE) yielded the products on N-alkylation. 6-(Morpholinomethyl)-3-R-2 H-[1,2,4]triazino[2,3-c]quinazoline-2-ones were obtained by heating of 6-dichloromethyl-3-R-6,7-dihydro-2H-[1,2,4]triazino[2,3-c]quinazoline-2-ones with five-fold excess of morpholine in EGEE. Reaction of 3-R-6-(trichloromethyl)-6,7-dihydro-2 H-[1,2,4]triazino[2,3-c]quinazolin-2-ones with three-fold excess of DIPEA in EGEE yielded 3-R-2#-[1,2,4]triazino[2,3-c]quinazoline-2-ones. The physicochemical and spectral characteristics of the prepared compounds were determined and discussed. [ABSTRACT FROM AUTHOR]

This Minireview provides insight into the early history of nucleophilic phosphinocatalysis. The concepts of 1,4‐addition of a tertiary phosphine to an α,β‐enone and of equilibrium between the resulting phosphonium zwitterion and phosphonium ylide established a fundamental basis for the development of several classical transformations, including the Rauhut‐Currier, Morita, McClure‐Baizer‐Anderson, and Oda reactions. [ABSTRACT FROM AUTHOR]

Fluoroacetate is a toxic compound whose environmental accumulation may represent an important contamination problem, its elimination is therefore a challenging issue. Fluoroacetate dehalogenase catalyzes its degradation through a two step process initiated by an SN2 reaction in which the aspartate residue performs a nucleophilic attack on the carbon bonded to the fluorine; the second step is hydrolysis that releases the product as glycolate. In this paper, we present a study based on density functional theory calculations of the SN2 initiation reaction modeled through the interaction between the substrate and the propionate anion as the nucleophile. Results are analyzed within the framework of the reaction force and using the reaction electronic flux to identify and characterize the electronic activity that drives the reaction. Our results reveal that the selective protonation of the substrate catalyzes the reaction by decreasing the resistance of the structural and electronic reorganization needed to reach the transition state. Finally, the reaction energy is modulated by the degree of stabilization of the fluoride anion formed after the SN2 reaction. In this way, a site-induced partial protonation acts as a chemical switch in a key process that determines the output of the reaction. [ABSTRACT FROM AUTHOR]

Neutralization of organophosphates is an issue of public health and safety, involving agrochemicals and chemical warfare. A promising approach is the nucleophilic neutralization, scope of this review, which focuses on the molecular nucleophiles: hydroxide, imidazole derivatives, alpha nucleophiles, amines and other nucleophiles. A reactivity mapping is given correlating the pathways and reaction efficiency with structural dependence of the nucleophile (basicity) and the organophosphate (electrophilic centers, P=O/P=S shift, leaving and non‐leaving group). Reactions extremely unfavorable (>20 years) can be reduced to seconds with various nucleophiles, some which are catalytic. Although there is no universal nucleophile, a lack of selectivity in some cases accounts for plenty of versatility in other reactions. The ideal neutralization requires a solid mechanistic understanding, together with balancing factors such as milder conditions, fast process, selectivity and less toxic products. [ABSTRACT FROM AUTHOR]

Asymmetric catalysis holds a prominent position among the important developments in chemistry during the 20th century. This was acknowledged by the 2001 Nobel Prize in chemistry awarded to Knowles, Noyori, and Sharpless for their development of chiral metal catalysts for organic transformations. The key feature of the catalysts was the crucial role of the chiral ligand and the nature of the metal ions, which promoted the catalytic conversions of the substrates via direct coordination. Subsequently the development of asymmetric organic catalysis opened new avenues to the synthesis of enantiopure compounds, avoiding any use of metal ions. Recently, an alternative approach to asymmetric catalysis emerged that relied on the catalytic functions of the ligands themselves boosted by coordination to metal ions. In other words, in these hybrid chiral catalysts the substrates are activated not by the metal ions but by the ligands. The activation and enantioselective control occurred via well-orchestrated and custom-tailored non-covalent interactions of the substrates with the ligand sphere of chiral metal complexes. In these metal-templated catalysts, the metal served either as a template (a purely structural role), or it constituted the exclusive source of chirality (metal-centred chirality due to the spatial arrangement of achiral or chiral bi-/tridentate ligands around an octahedral metal centre), and/or it increased the Brønsted acidity of the ligands. Although the field is still in its infancy, it represents an inspiring combination of both metal and organic catalysis and holds major unexplored potential to push the frontiers of asymmetric catalysis. Here we present an overview of this emerging field discussing the principles, applications and perspectives on the catalytic use of chiral metal complexes that operate as "organocatalysts in disguise". It has been demonstrated that these chiral metal complexes are efficient and provide high stereoselective control in asymmetric hydrogen bonding catalysis, phase-transfer catalysis, Brønsted acid/base catalysis, enamine catalysis, nucleophilic catalysis, and photocatalysis as well as bifunctional catalysis. Also, many of the catalysts have been identified as highly effective catalysts at remarkably low catalyst loadings. These hybrid systems offer many opportunities in the synthesis of chiral compounds and represent promising alternatives to metal-based and organocatalytic asymmetric transformations. [ABSTRACT FROM AUTHOR]

The peroxyoxalate reaction is being widely used for various analytical and bioanalytical applications, and however, few mechanistic studies are performed in aqueous media, important mainly for bioanalytical applications, where low chemiluminescence emission quantum yields are obtained. In this sense, we report here kinetic studies on the peroxyoxalate reaction, using two commercially available and widely utilized esters, bis(2,4‐dinitrophenyl) oxalate (DNPO) and bis(2,4,6‐trichlorophenyl) oxalate (TCPO), in 1,2‐dimethoxyethane:water mixtures. The reaction of the much more reactive DNPO, in anhydrous and aqueous media, occurs by a direct nucleophilic attack of H2O2 to the oxalic ester, not involving nucleophilic catalysis by imidazole. Contrary, in the reaction of the less reactive TCPO with H2O2, imidazole acts mainly as nucleophilic catalyst. For both esters, experimental conditions are established where precise kinetic data and emission quantum yields can be obtained. Interestingly, the quantum yields in 1,2‐dimethoxyethane water mixtures increase up to a water concentration of 0.7 mol L–1 and decrease significantly with higher concentrations. [ABSTRACT FROM AUTHOR]

The behavior of tetraethylammonium salts in nucleophilic opening of the oxirane ring of epichlorohydrin (ECH) in the system ECH–proton donor–Et4N+ X–, where proton donor is benzoic acid or 4-nitrophenol and X = PhCOO or NO3, was studied by the kinetic and spectrophotometric methods. The order of the reaction in tetraethylammonium salt, benzoic acid, and 4-nitrophenol was estimated as first, zero, and less than zero, respectively. The mechanism of nucleophilic opening of the oxirane ring of ECH was elucidated on the basis of monitoring of the accumulation of 4-nitrophenoxide ion in the system ECH–4-nitrophenol–Et4NX upon variation of the initial concentrations of both tetraethylammonium salt and proton donor (4-nitrophenol) itself. The anion X of the initial tetraethylammonium salt was found to be irreversibly consumed as a result of its attack on the oxirane ring with participation of the proton donor, which led to generation of tetraethylammo-nium 4-nitrophenoxide, and the latter catalyzed the subsequent formation of the final product. An increase in the concentration of 4-nitrophenol was accompanied by reduction of both the rate of formation of 4-nitrophenoxide ion and the overall reaction rate, which corresponds to a mechanism involving nucleophilic attack of the anion X on the oxirane ring that is not activated by the proton donor. [ABSTRACT FROM AUTHOR]

In this study, we aimed to enhance the catalytic activity of perovskite catalysts and elucidate their catalytic behavior in the oxidative coupling of methane (OCM), using alkali-added LaAlO3 perovskite catalysts. We prepared LaAlO3-XY (X = Li, Na, K, Y = mol %) catalysts and applied them to the OCM reaction. The results showed that the alkali-added catalysts' activities were promoted compared to the LaAlO3 catalyst. In this reaction, ethane was first synthesized through the dimerization of methyl radicals, which were produced from the reaction of methane and oxygen vacancy in the perovskite catalysts. The high ethylene selectivity of the alkali-added catalysts originated from their abundance of electrophilic lattice oxygen species, facilitating the selective formation of C2 hydrocarbons from ethane. The high COx (carbon monoxide and carbon dioxide) selectivity of the LaAlO3 catalyst originated from its abundance of nucleophilic lattice oxygen species, favoring the selective production of COx from ethane. We concluded that electrophilic lattice oxygen species play a significant role in producing ethylene. We obtained that alkali-adding could be an effective method for improving the catalytic activity of perovskite catalysts in the OCM reaction. [ABSTRACT FROM AUTHOR]

We herein report an unprecedented strategy for the asymmetric α‐chlorination of β‐keto esters with hypervalent iodine‐based Cl‐transfer reagents using simple Cinchona alkaloid catalysts. Our investigations support an α‐chlorination mechanism where the Cinchona species serves as a nucleophilic catalyst by reacting with the chlorinating agent to generate a chiral electrophilic Cl‐transfer reagent in situ. Using at least 20 mol‐% of the alkaloid catalyst allows for good yields and enantioselectivities for a variety of different β‐keto esters under operationally simple conditions. [ABSTRACT FROM AUTHOR]

Nucleophilic phosphine catalysis is a practical and powerful tool for the synthesis of various heterocyclic compounds with the advantages of environmentally friendly, metal-free, and mild reaction conditions. The present report summarizes the construction of four to eight-membered heterocyclic compounds containing nitrogen, oxygen and sulphur atoms through phosphine-catalyzed intramolecular annulations and intermolecular [2+2], [3+2], [4+1], [3+1+1], [5+1], [4+2], [2+2+2], [3+3], [4+3] and [3+2+3] annulations of electron-deficient alkenes, allenes, alkynes and Morita–Baylis–Hillman carbonates. [ABSTRACT FROM AUTHOR]

The study of the reaction systems "R3N – proton‐donor reagent (NuH) – epichlorohydrin" using a complex of various kinetic methods of investigation allowed the reaction pathway and the catalysis mechanism of the oxirane ring opening by proton‐donor reagents in the presence of R3N to be detailed. It was confirmed that the catalytic activity of R3N consists in their quaternization by oxirane under the obligatory condition of its electrophilic assistance with the NuH reagent. The quaternization process of tertiary amines was studied using 1H NMR and UV spectroscopy, quantum chemical modeling, and correlation analysis. It was shown that the transition states of the quaternization stage are dissociative, and their degree of looseness depends on the electrophilic activation of the oxirane ring. [ABSTRACT FROM AUTHOR]

Chiral aryl allyl ethers are important substructure which can be found in a lot of natural products and bioactive molecules. A series of substituted chiral aryl allyl ethers were successfully synthesized from the newly designed MBH carbonates by releasing a molecule of CO2 under nucleophilic catalysis. The yields are up to 95% and the enantioselectivities are up to 90%. The structure of products was determined by ¹H NMR and 13C NMR. [ABSTRACT FROM AUTHOR]

Over the past two decades, the nucleophilic phosphine catalysis has effected many powerful annulation reactions and emerged as an intriguing platform for the generation of highly functionalized carbo- and heterocycles. In addition to the well-established (3 + 2) annulation, the phosphine-promoted (4 + 1) annulation has received increasing attention and developed rapidly in recent years, which complements the (3 + 2) annulation and also provides an alternative approach to structurally diverse five-membered carbo- and heterocycles. This minireview summarizes the recent advances in phosphinepromoted (4 + 1) annulation reactions according to the type of substrates used in the annulations. [ABSTRACT FROM AUTHOR]

A convergent, microwave-assisted protocol for the synthesis of disubstituted NH -imidazoles via nucleophilic catalysis is described. The substituted imidazoles are accessed via the intramolecular addition of a variety of amidoxime substrates to activated alkynes followed by a thermally induced rearrangement of the in situ generated O -vinylamid-oxime species. The unprotected imidazoles contain an aryl group at the 2-position as well as an ester moiety at the 4-position. [ABSTRACT FROM AUTHOR]

• Fe(CO) 5 and [Fe(CO) 6 ]2+ were calculated and a new transition state was designed. • Calculation of WGSR mechanism includes the gaseous and aqueous phases. • The higher the temperature, the higher the TOF values at critical conditions. The WGSR with Fe(CO) 5 and [Fe(CO) 6 ]2+ complexes were investigated using DFT in both gaseous and aqueous phases. Thermodynamic analyses indicated that the high dielectric constant of water inhibits the activity of OH− and [Fe(CO) 6 ]2+ ions, leading to a substantial decrease in the energy released during the nucleophilic attack of OH− on Fe(CO) 5 and [Fe(CO) 6 ]2+ in the aqueous phase. In addition, a potential low energy pathway has been discovered by designing new transition states for the final step of Fe(CO) 5 -catalyzed WGSR: 1 → 6 → 2 → 3 → 4 → 5(a) → 5(b) → 6. According to the results of the ESM, [Fe(CO) 6 ]2+ possesses the highest gaseous phase TOF value (1.27 × 10−18 s–1), both Fe(CO) 5 and [Fe(CO) 6 ]2+ have higher TOF values in the gaseous phase compared to the aqueous phase, which increases with rising temperature. Therefore, these results suggest that [Fe(CO) 6 ]2+ serves as the advantageous catalyst involved WGSR in the aqueous phase. [Display omitted] [ABSTRACT FROM AUTHOR]

Background: Biodegradation is a reliable approach for efficiently eliminating persistent pollutants such as chlorpyrifos. Despite many bacteria or fungi isolated from contaminated environment and capable of degrading chlorpyrifos, limited enzymes responsible for its degradation have been identified, let alone the catalytic mechanism of the enzymes. Results: In present study, the gene cpd encoding a chlorpyrifos hydrolase was cloned by analysis of genomic sequence of Paracoccus sp. TRP. Phylogenetic analysis and BLAST indicated that CPD was a novel member of organophosphate hydrolases. The purified CPD enzyme, with conserved catalytic triad (Ser155-Asp251-His281) and motif Gly-Asp-Ser-Ala-Gly, was significantly inhibited by PMSF, a serine modifier. Molecular docking between CPD and chlorpyrifos showed that Ser155 was adjacent to chlorpyrifos, which indicated that Ser155 may be the active amino acid involved in chlorpyrifos degradation. This speculation was confirmed by site-directed mutagenesis of Ser155Ala accounting for the decreased activity of CPD towards chlorpyrifos. According to the key role of Ser155 in chlorpyrifos degradation and molecular docking conformation, the nucleophilic catalytic mechanism for chlorpyrifos degradation by CPD was proposed. Conclusion: The novel enzyme CPD was capable of hydrolyze chlorpyrifos and Ser155 played key role during degradation of chlorpyrifos.

Unprecedented phosphine‐catalyzed [4+1] cycloadditions of allenyl imides have been discovered using various N‐based substrates including methyl ketimines, enamines, and a primary amine. These transformations provide a one‐pot access to cyclopentenoyl enamines and imines, or (chiral) γ‐lactams through two geminal C−C bond or two C−N bond formations, respectively. Several P‐based key intermediates including a 1,4‐(bis)electrophilic α,β‐unsaturated ketenyl phosphonium species have been detected by 31P NMR and HRMS analyses, which shed light on the postulated catalytic cycle. The synthetic utility of this new chemistry has been demonstrated through a gram‐scaling up of the catalytic reaction as well as regioselective hydrogenation and double condensation to form cyclopentanoyl enamines and fused pyrazole building blocks, respectively. [ABSTRACT FROM AUTHOR]

Nucleophilic substitutions (SN) account for the most essential and frequently applied chemical transformations. SN‐reactions allow forging C–C, C–O, C–N and C–Cl bonds, for example, from natural abundant starting materials such as alcohols and carboxylic acids. Products of SN‐reactions are ubiquitous and find inter alia applications as pharmaceuticals, plant protection agents and polymers. However, conventional SN‐type approaches are restricted frequently by the necessity of hazardous reagents and by‐products, a poor waste‐balance and therefore sustainability and high levels of costs, which especially impedes application in large scale synthesis. In order to provide solutions to these limitations, the development of novel catalytic methods for SN‐transformations has evolved into a flourishing and reviving area of research. The current review enables an overview of modern strategies for catalytic nucleophilic substitutions, presents as main topic the state‐of‐the‐art with respect to SN‐methods that are promoted by Lewis bases and points out potential future directions for further innovations. [ABSTRACT FROM AUTHOR]

p‐Sulfonatocalixarene water soluble macrocyclic host receptors are known to form cooperative ternary complexes with complementary organic guest and metal cations. This property may be explored to enhance the interaction of weak nitrogen ligands with metal cations in a confined space showing some resemblance to metal‐containing enzymes. However, the best of our knowledge, catalytic potential of this property remains unexplored. In this work the Ni2+ catalyzed hydrolysis of a picolinate ester (2,4‐dinitrophenyl picolinate, 1) was used as a model reaction to evaluate the effect of sulfonatocalixarene macrocycles in the kinetics of this reaction. The results show that the host molecules promote the reaction through simultaneous complexation of the metal cation and the substrate and, in the case of the larger calixarenes containing more basic phenol groups, substantially higher rate enhancements are observed owing to additional assistance provided by base/nucleophilic catalysis. However, due the ionic nature of these receptors auto‐inhibition of the reaction is observed at higher concentrations due counterion (Na+) binding that competes with the catalytically active Ni2+ ‐complexes. [ABSTRACT FROM AUTHOR]

The hydrolysis reaction of methyltrimethoxysilane MeSi(OMe)3 under neutral conditions and the catalytic role of the fluoride ion in this reaction have been re-examined using DFT theoretical methods in methanol solution. Contrary to the common opinion, formation of pentacoordinate silicon fluoride, either free or complexed with a water molecule, proceeds with a free energy barrier. A hypercoordinate silicon intermediate is in equilibrium with the ion–dipole complex with fluoride, which is usually lower in energy than the pentacoordinate species. A comparison of the hydrolysis pathways of uncomplexed silanes, MeSi(OMe)3−n(OH)n, n = 0–3, and the corresponding ion–dipole complexes with fluoride and pentacoordinate silicon fluorides showed that both complexes hydrolyze more easily than the uncomplexed silanes. The pathway involving ion–dipole complexes is kinetically preferred. The catalytic effect of fluorine in the hydrolysis of these complexes is of a basic nature, i.e., fluoride acts as a base, withdrawing a proton from the attacking water, thus increasing its nucleophilicity. However, since both intermediates are in equilibrium, nucleophilic catalysis may become significant under specific conditions, when the concentration of the pentacoordinate silicon–fluoride complex is higher. [ABSTRACT FROM AUTHOR]

The first small anion‐triggered Steglich rearrangements are reported. Tetrabutylammonium carboxylates‐, cyanide‐ and fluoride promote the O‐ to C‐acyl transfer of a range of O‐acylated oxindoles to form 3,3‐disubstituted oxindole products with new quaternary stereocentres. DFT calculations on the TBAF‐mediated reaction strongly support a nucleophilic catalysis mechanism involving initial attack of fluoride on the O‐acyl group to give an enolate and an acyl fluoride in the rate determining step. [ABSTRACT FROM AUTHOR]

Gold(III) carboxylate species, stabilized by a κ3‐(N^C^C) ligand template, are presented herein. A η1‐AuIII‐C(O)‐OH species has been characterized under cryogenic conditions as a result of the nucleophilic attack of an ammonium hydroxide onto a dinuclear μ‐CO2‐κ3‐(N^C^C)AuIII precursor. Thermal decomposition for these species proceeds by an unusual decarbonylation process, in contrast to typical decarboxylation pathways observed in related metallocarboxylic acids. [ABSTRACT FROM AUTHOR]

Asymmetric allylic amination of Morita–Baylis–Hillman (MBH) adducts with simple aromatic amines is successfully realized by nucleophilic amine catalysis. A range of substituted α-methylene-β-arylamino esters is accessed in moderate to high yields (up to 88%) and with excellent enantioselectivities (up to 97% ee). Inorganic fluorides are found to be able to improve the enantioselectivity of the allylic amination reaction. A pyrrole-2-carboxylate and a cyclic imide are also compatible with this catalytic system. A chiral 2,3-dihydroquinolin-4-one derivative is easily obtained from the allylic amination product. [ABSTRACT FROM AUTHOR]