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Lattice‐oxygen is highly oxidizable, ideal for electrocatalytic C−H oxidation but insufficient alone for C(O)−C bond cleavage due to the non‐removable nature of lattice sites. Here, we present a visible light‐assisted electrochemical method of in situ formulating removable lattice‐oxygen sites in a nickel‐oxyhydroxide (ESE‐NiOOH) electrocatalyst. This catalyst efficiently converts aromatic alcohols and carbonyls with C(O)−C fragments from lignin and plastics into benzoic acids (BAs) with high yields (83–99 %). Without light irradiation, ESE‐NiOOH's intrinsic lattice‐oxygen is non‐removable and inert for C(O)−C bond cleavage. In situ characterizations show light‐induced lattice‐oxygen removal and regeneration via OH− refilling. Theoretical calculations identify the nucleophilic oxygen attack on ketone‐derived carbanion as a rate‐determining step, which can be remarkably facilitated by removable lattice‐oxygen to activate α‐C−H bonds. As a proof‐of‐concept, an "electrochemical funnel" strategy is developed for high‐efficiency upgrading aromatic mixtures with C(O)−C moieties into BA with up to 94 % yield. This in situ removal‐regeneration approach for lattice sites opens an avenue for the tailored design of interfacial electrocatalysts to selectively upcycle waste carbon sources into valuable products. [ABSTRACT FROM AUTHOR]

Azametallacyclopentadienes are an important class of metallacycles as the key intermediates in metal‐promoted or catalyzed carbon‐carbon coupling reaction of nitriles and alkynes. Rare‐earth azametallacyclopentadienes have shown various reactivity toward nitriles, depending on the substituents of nitriles. The reaction of azalutetacyclopentadienes toward 2‐methylbenzonitriles has been investigated in this work, which selectively affords the fused 7‐5‐6‐membered azalutetacycles as products. Computational studies reveal that the reaction of azalutetacyclopentadienes toward 2‐methylbenzonitriles selectively initiates with the remote activation of the benzylic C−H bond by the Lu−N bond, followed by the intramolecular nucleophilic attack from the deprotonated benzylic carbon to form a C−C bond. Subsequently, the high ring strain promoted the generation of the uncoordinated carbanion dissociated from the lutetium center, which then undergoes intramolecular nucleophilic attack toward C=N triple bond to give the final product containing fused 7‐5‐6‐membered azalutetacycle. This work not only achieves highly selective three‐step cascade reaction to form a unique class of rare‐earth metallacycle, but also provides a new idea for the transformation of unsaturated substrates with C−H bonds that can be activated. [ABSTRACT FROM AUTHOR]

Trivalent phosphine catalysis is mostly utilized to activate the carbon‐carbon multiple bonds to form carbanion intermediate species and is highly sensitive to certain variables. Random manual multi‐variables are critical for understanding the batch disabled regeneration of trivalent phosphine chemistry. We need the artificial intelligence‐based system which can change the variable based on previously conducted failed experiment. Herein, we report an auto‐optimized electro‐micro‐flow reactor platform for the in‐situ reduction of stable P(V) oxide to sensitive P(III) and further utilized the method for Corey‐Fuchs reaction. [ABSTRACT FROM AUTHOR]

Although carbanions, which are usually regarded as reactive species and powerful metalation reagents, can be stabilized through choice of the substitution pattern, they have rarely been considered for the design of weakly coordinating anions (WCA). Here, we report on an evaluation of the potential of a series of differently substituted carbanions to serve as WCA by computational methods. This led us to the synthesis of the water‐ and air‐stable allyl anion 1 with triflyl and 3,5‐bis(trifluoromethyl)phenyl (ArF) moieties, which can be isolated in high yields even on a gram‐scale. Single crystal X‐ray crystallography and NMR studies confirmed the weak coordination ability of the anion by showing negligible or only weak interactions with different cations. This property enabled the application of 1 in the stabilization of reactive group 14 and 15 cations. In addition to the crystallization of a phosphenium cation, the first all‐carbon salt with a non‐aromatic carbanion is reported, which revealed to be a convenient reagent for hydride abstraction such as from silanes. Overall, this work demonstrates the so far untapped potential of carbanions as WCA, that are accessible with a variety of different cations for various applications. [ABSTRACT FROM AUTHOR]

Bridgehead alkenes are polycyclic molecules bearing at least one C=C bond that includes a bridgehead carbon atom. For small bicyclic systems, these bonds are highly strained due to geometric constraints placed on the sp2 hybridized carbon atoms. These small, strained molecules have been termed "anti-Bredt" alkenes. β-halo carbanions have served as convenient precursors to bridgehead alkenes in experimental studies. We observed that upon attempted computational geometric optimizations (ωB97X-D/aug-cc-pVDZ) of the precursors, spontaneous elimination of the halide occurs along with formation of the anti-Bredt alkene in many cases. Such computational eliminations were shown to faithfully mimic experimentally obtained results. Computational elimination was not observed for [1.1.1] or [2.1.1] frameworks, in agreement with predictions that these bridgehead alkenes are too strained to be formed. However, computational elimination from the [2.2.1] framework was observed to form 1-norbornene, a compound suggested in experimental work to be a reactive intermediate. Similarly, [3.1.1] frameworks and higher led to eliminations upon computational geometric optimization, in agreement with experimental findings. Natural bond order (NBO) calculations of the starting geometries proved to be excellent predictors as to whether elimination would take place. Those precursor compounds exhibiting delocalization energies in the order of 10 kcal/mol between the lone-pair electrons of the carbon atom and σ*C-Br were generally found to undergo elimination. Thus, computational optimization of β-halo substituted bicyclic precursor anions can be used to predict whether strained anti-Bredt alkenes are likely to be formed, thereby saving valuable time and costs in the experimental lab. [ABSTRACT FROM AUTHOR]

The Brook rearrangement is a valuable synthetic tool that facilitates the controlled construction of complex molecules. Conventionally, it generates carbanion intermediates utilized in subsequent functionalization reactions. In this review, we will explore recent advancements in the Brook rearrangement that extend beyond the traditional functionalization reactions. Specifically, we will highlight its involvement in unusual bond cleavage, annulation reactions, and dearomatization efforts. The novelty of this rearrangement is underscored by showcasing its most recent applications. 1 Introduction 2 Novel Synthetic Pathways Involving the Brook Rearrangement 2.1 C–C and C–X Bond Formation 2.2 C–C and C–X Bond Cleavage 2.3 Stereodefined Substituted Silyl Enol and Allenol Ethers 2.4 Annulation Reactions 2.5 Dearomatization 3 Synthetic Applications 4 Conclusion [ABSTRACT FROM AUTHOR]

The electrophilic alkylation of dianions of fullerene derivatives generated by deprotonation of the corresponding dihydrides is described, using the example of the regioselective synthesis of a trifunctional derivative C70(CF3)8(CH3)H with a near-equatorial location of all addends. The structure of the first synthesized compound is established by means of mass spectrometry and one- and two-dimensional NMR correlation spectroscopy. The reasons for the high regioselectivity of the formation of the single isomer C70(CF3)8(CH3)H are explained using quantum chemical calculations at the level of density functional theory for isomers of anionic intermediates and the product. Electron absorption and fluorescence spectroscopy are used to demonstrate the fundamental effect of the near-equatorial location of addends in the C70(CF3)8(CH3)H compound on its optical and fluorescent properties. [ABSTRACT FROM AUTHOR]

Phenyldiazenyl moiety has been utilized both as a protective and activating group to synthesize C-1-substituted tetrahydroisoquinolines via lithiation–substitution strategy. This reaction sequence involves generation of α-amino carbanions, derived from N -phenyldiazenyl tetrahydroisoquinolines, followed by coupling with various electrophiles, e.g., aldehyde, ketones, alkyl halide, oxiranes, isocyanates, and with in situ generated arynes. Deprotection of the protecting group was carried out under acidic conditions to afford the desired α-substituted products in moderate to good yields. So, triazene as a protecting/directing group and its compatibility with strong bases provide a good synthetic utility for the synthesis of a variety of α-substituted secondary amines via lithiation substitution reaction. [ABSTRACT FROM AUTHOR]

Transposition reactions, i. e. switching the position of functional groups, are a powerful tool for molecular editing. The transposition of a halogen atom attached to an aromatic ring, referred to as the halogen dance reaction, has great potential in the fields of pharmaceuticals, agrochemicals, natural products, and functional materials. However, the substrate scope of this reaction is limited owing to the intrinsic difficulty in facilitating multiple catalytic cycles involving several aryllithium species. In this concept paper, recent advances in halogen dance catalysis that have expanded the substrate scope of this reaction are highlighted. [ABSTRACT FROM AUTHOR]

The mini-review covers the results of the authors on acetylene chemistry achieved within 2022. This unusual format was selected in order to assess the dynamics and effectiveness of the developed approaches in result/time coordinates and the prospects for further research in these areas. The review discusses new reactions of acetylene and its derivatives that generally take place in superbasic media, in which the dual reactivity of the carbon—carbon triple bond (i.e. its ability to exhibit both nucleophilic and electrophilic properties) is most pronounced. The discovered by us reactions are the atom economical (they do not produce side products), energy- and resource-saving (they proceed at room or slightly elevated temperature), do not require transition metal catalysts, and can be implemented using inexpensive available starting compounds. [ABSTRACT FROM AUTHOR]

In biosynthesis multiple kinds of reactive intermediates are generated, transported, and reacted across different parts of organisms, enabling highly sophisticated synthetic reactions. Herein we report a convergent synthetic approach, which utilizes dual intermediates of cationic and carbanionic species in a single step, hinted at by the ideal reaction conditions. By reactions of unsaturated precursors, such as enamines, with a superacid in a flow microreactor, cationic species, such as iminium ions, are generated rapidly and irreversibly, and before decomposition, they are transported to react with rapidly and independently generated carbanions, enabling direct C-C bond formation. Taking advantage of the reactivity of these double reactive intermediates, the reaction take place within a few seconds, enabling synthetic reactions which are not applicable in conventional reactions. Optimizing the transport, mobility and diffusion of reactants and intermediates in a confined space can accelerate reactions. Here the authors study the reaction of highly reactive intermediates such as short-lived cationic and anionic species in a flow reactor. [ABSTRACT FROM AUTHOR]

Electroreductive ring-opening carboxylation of styrene carbonates with CO2 to achieve dicarboxylic acids and/or β-hydroxy acids has been developed via the selective cleavage of the C(sp³)-O bond in cyclic carbonates. The product selectivity is probably determined by the stability and reactivity of the key benzylic radical and carbanion intermediate. [ABSTRACT FROM AUTHOR]

The chemistry of extremely bulky amide ligands is troubled by difficulties in deprotonation of the parent amine. As an alternative route to superbulky amide reagents, the addition of polar reagents to a sila–imine has been investigated. Attempts to synthesize the superbulky amide anion (tBu3Si)2N− by addition of tBuLi to tBu2Si=N(SitBu3) failed and gave tBu3Si(tBu2HSi)NLi and isobutene. Reaction of the sila–imine with KOtBu successfully led to tBu3Si[tBu2(tBuO)Si]NK which crystallized as a separated ion–pair. Reaction with the slightly bulkier KOAd (Ad=1‐adamantyl) led in presence of THF to ether ring–opening. Reaction with tBuOH gave tBu3Si[tBu2(tBuO)Si]NH but this amine cannot be easily deprotonated. Reaction with (BDI*)MgnBu in presence of THF gave (BDI*)Mg+ ⋅ (THF)2 and the non–coordinating anion tBu3Si[tBu2(nBu)Si]N−; BDI*=ß‐diketiminate ligand HC[C(tBu)N−DIPP]2, DIPP=2,6‐diisopropylphenyl. Reaction of Mg(nBu)2 with tBu2Si=N(SitBu3) led to a Mg complex with one amide ligand: tBu3Si[tBu2(nBu)Si]N−. The other superbulky amide anion isomerized by internal deprotonation of a tBu‐substituent to give a primary carbanion that is also coordinated to Mg. Although the amide–to–carbanion isomerization is highly contrathermodynamic, it allows for coordination of both anions to a single Mg center. The new bulky amides are rare cases of halogen–free weakly coordinating anions. [ABSTRACT FROM AUTHOR]

Photocatalytic reactions involving a reductive radical‐polar crossover (RRPCO) generate intermediates with carbanionic reactivity. Many of these proposed intermediates resemble highly reactive organometallic compounds. However, conditions of their formation are generally not tolerated by their isolated organometallic versions and often a different reactivity is observed. Our investigations on their nature and reactivity under commonly used photocatalytic conditions demonstrate that these intermediates are indeed best described as free, superbasic carbanions capable of deprotonating common polar solvents usually assumed to be inert such as acetonitrile, dimethylformamide, and dimethylsulfoxide. Their basicity not only towards solvents but also towards electrophiles, such as aldehydes, ketones, and esters, is comparable to the reactivity of isolated carbanions in the gas‐phase. Previously unsuccessful transformations thought to result from a lack of reactivity are explained by their high reactivity towards the solvent and weakly acidic protons of reaction partners. An intuitive explanation for the mode of action of photocatalytically generated carbanions is provided, which enables methods to verify reaction mechanisms proposed to involve an RRPCO step and to identify the reasons for the limitations of current methods. [ABSTRACT FROM AUTHOR]

An intermolecular addition reaction involving an unconventional combination of a diarylmethyl anion and an electrophile, which is mediated by the [1,2]‐phospha‐Brook rearrangement under Brønsted base catalysis, was developed. Diarylmethyl anions having a benzofuran moiety were generated through the rearrangement with the aid of a catalytic amount of phosphazene base P2‐tBu. The resulting carbanion intermediates were trapped by various electrophiles, such as α,β‐unsaturated ketones, aryl aldehydes, α‐ketoesters, and N‐Boc imines, providing the corresponding diarylalkane derivatives in good yields. [ABSTRACT FROM AUTHOR]

Kinetics of the reactions of colored carbanions (reference nucleophiles) with S‐(trifluoromethyl)dibenzothiophenium ions (Umemoto's reagents) and hypervalent trifluoromethyl‐substituted iodine compounds (Togni's reagents) have been determined photometrically using stopped‐flow techniques. The second‐order rate constants k2(20 °C) for the reactions of Umemoto's sulfonium ions (generation I and II) with the reference nucleophiles in DMSO follow the correlation lg k2(20 °C)=sN(N+E) and can be used to determine the electrophilicity parameters E of these trifluoromethylating reagents. It is shown that the conditions reported for the reactions of Umemoto's generation I reagents with a variety of C‐nucleophiles are in line with the electrophilicity parameter E≈−13 determined for these reagents. Though Togni's hypervalent iodine‐based trifluoromethylation reagents do not follow this linear free energy relationship, the kinetics of their reactions with carbanions indicate that they cover the same reactivity range as Umemoto's generation I and II reagents. [ABSTRACT FROM AUTHOR]

A desilylation process of optically active silyl‐substituted gem‐difluorocyclopropanes with tetrabutylammonium fluoride (TBAF) showed a substantial reduction of enantiopurity of the resultant gem‐difluorocyclopropanes even at ambient temperatures. The electron‐withdrawing aryl substituent at the 3‐position in the 1‐silyl‐2,2‐difluorocyclopropane system accelerated the racemization, indicating a correlation with the stability of the anionic intermediates. The plausible racemization pathway through homolytic cleavage of the distal bond in gem‐difluorocyclopropane is inconsistent with the experimental results because the high energy of >34 kcal/mol is required for generating the open‐shell 2,2‐difluoropropane‐1,3‐diyl skeleton. The DFT studies using the anionic 2,2‐difluoromethyl‐3‐phenylcyclopropanylide intermediate supported the alternative isomerization pathway through the intramolecular migration of hydrogen and the resultant thermodynamically stable 2,2‐difluoromethyl‐1‐phenylcyclopropanylide anion could facilitate the racemization process at the stereocenter. Although the transition state indicated considerable activation energies, the high frequency of imaginary vibration should correlate with a barrier of a very narrow width enabling quantum tunneling under the H‐migration step. The observed isotope effect is compatible with the proposed mechanism through the intramolecular H‐migration. [ABSTRACT FROM AUTHOR]

Carbanion‐based ionic liquids are proposed and utilized as the key components for the construction of five super‐nucleophilic deep eutectic solvents (SNDESs) in the paper. The super‐nucleophilic nature of carbanion‐based ionic liquids (ILs) is found to enable the capture of CO2 with large absorption capacity. However, the absorption is very slow in the IL due to high viscosity. The synergy of carbanion siting and hydrogen bonding is found to enable high and fast absorption of CO2 in [N2222][CH(CN)2]‐ethylimidazole (Eim), and a synergistic absorption mechanism is proposed and validated from spectroscopic analyses and quantum calculations. The enthalpy change of CO2 absorption in [N2222][CH(CN)2]‐Eim is calculated to be −39.6 kJ mol−1 according to the thermodynamic model, and the moderate value implies that both absorption and desorption of CO2 in the DES are favored and well balanced. The carbanion and hydrogen bond mediated by SNDESs provides a novel insight into the efficient CO2 capture. [ABSTRACT FROM AUTHOR]

The wide applications of alpha‐boryl carbanions in selective coupling with organohalides, imines/carbonyls and conjugated unsaturated substrates has become an interesting tool for organic synthesis. Strategically, the inclusion of heteroatoms, such as Si, S, N, F, Cl, Br and I in the alpha position opens a new venue towards multifunctionalities in molecular design. Here, a conceptual and practical view on powerful carbanions, containing α‐silicoboron, α‐thioboron, α‐haloboron and α‐aminoboron is given, as well as a prespective on their efficient application for selective electrophilic trapping. [ABSTRACT FROM AUTHOR]

In this study, a novel preparation method of theaflavin (TF) has been established. Our findings indicated that the formation of TF was significantly enhanced by using an ice bath (2–3°C). Additionally, increasing the ratio of (−)‐epigallocatechin (EGC) under the ice bath could further improve its yield. This approach prevented the appearance of a dark solution within 3 h, effectively protecting TF from oxidation. Our study on the generation mechanism of TF suggested that EGC‐quinone I (EGC‐Q‐I) with two carbanions could potentially serve as one of synthons based on the retrosynthetic analysis of the bicyclo[3.2.1]octane‐type intermediate. Subsequently, quantum mechanical calculations further supported this hypothesis. Practical Application: In this study, we have developed a novel method for the synthesis of theaflavin (TF), demonstrating that the use of ice bath significantly enhanced its yield. Increasing the ratio of (−)‐epigallocatechin (EGC) under the ice bath further improved TF yields and prevented darkening of the solution for at least 3 h, thereby protecting TF from oxidation. Our study suggested that EGC‐quinone I is a potential synthon based on the retrosynthetic analysis of the bicyclo[3.2.1]octane‐type intermediate (BOI). This hypothesis is supported by QM calculations. [ABSTRACT FROM AUTHOR]

A method for the generation of tertiary carbanions via a deaminative radical‐polar crossover is reported using redox active imines from α‐tertiary primary amines. A variety of benzylic amines and amino esters can be used in this approach, with the latter engaging in a novel "aza‐Reformatsky" reaction. Electronic trends correlate the stability of the resulting carbanion with reaction efficiency. The anions can be trapped with different electrophiles including aldehydes, ketones, imines, Michael acceptors, and H2O/D2O. Selective anion formation can be achieved in the presence of another equivalent or more acidic C−H bond in both an inter‐ and intramolecular fashion. Mechanistic studies suggest the intermediacy of a discrete carbanion intermediate. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Metallacyclopentadienes are important metallacycles and regarded as intermediates in many reactions, therefore, new methods to achieve them are anticipated. In this study, a formal [3+2] method, through the reactions of an osmapentalyne with benzyl carbanions, was developed. The reactions underwent a nucleophilic attack of carbanions to the Os≡C bond, followed by C—H activation to form the five‐membered osmacyclopentadiene ring. Most of the reactions were carried out at room temperature, the substituents on the aromatic rings of benzyl carbanions are diverse, and the resulting products contain an Os—H bond, representing a novel type of 10C‐carbolong complexes. This work provides a new convenient route to construct metallacyclopentadienes, which is expected to further promote the development of such a type of substances. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Metallacyclopentadienes are important metallacycles and regarded as intermediates in many reactions, therefore, new methods to achieve them are anticipated. In this study, a formal [3+2] method, through the reactions of an osmapentalyne with benzyl carbanions, was developed. The reactions underwent a nucleophilic attack of carbanions to the Os≡C bond, followed by C—H activation to form the five‐membered osmacyclopentadiene ring. Most of the reactions were carried out at room temperature, the substituents on the aromatic rings of benzyl carbanions are diverse, and the resulting products contain an Os—H bond, representing a novel type of 10C‐carbolong complexes. This work provides a new convenient route to construct metallacyclopentadienes, which is expected to further promote the development of such a type of substances. [ABSTRACT FROM AUTHOR]

We present an in‐depth study of hydride transfer or proton abstraction at natural product guaiazulene to form guaiazulenide salts (8‐H‐GuaH)Li 1 a and (Gua")Na(OEt2) 2. Both carbanions were correctly proposed by Hafner et al. but could never be isolated in isomerically, spectroscopically and analytically pure form so far. Therefore, their use as cyclopentadienyl synthons in organometallic chemistry remained essentially unexplored. Here, we present their synthesis and full characterisation including 2D NMR spectroscopy and two XRD structural analyses. 1 a is isolated in isomerically and chemically pure form via a catalytic variant of olefin hydrolithiation, the addition of LiH to an activated hydrocarbon C=C double bond catalysed by LiAlH4. This atom economic synthesis of a pure organolithium compound from an olefin, LiH or lithium and dihydrogen, respectively, is without precedence. In a follow up report we will demonstrate that these valuable ligand salts can be used as cheap sterically demanding renewable feedstock‐based cyclopentadienyl synthons in the synthesis of homo‐ and heteroleptic late transition metal complexes and catalysts. [ABSTRACT FROM AUTHOR]

A variety of novel naphthimindazol‐N‐oxides and naphththiazol‐N‐oxide have been prepared in a simple two‐step process. The first step involves the reaction of 1‐chloro‐2,4‐dinitronaphthalene with glycine, alanine, glycolic acid, thioglycolic acid, and their methyl esters affording substitution products, the subsequent treatment of which with base furnishes naphthimindazol‐N‐oxide and naphththiazol‐N‐oxide derivatives. Stepwise reaction mechanisms via carbanions, nitrogen anions, and spiro Meisenheimer intermediates are proposed. The action of 10% NaOH in dioxane on the substitution products was measured spectrophotochemically, and the kinetic studies suggested that the N‐naphthyl glycine and N‐naphthyl alanine follow a second‐order rate law while S‐naphthyl thioglycolic acid is accurately first‐order kinetics. [ABSTRACT FROM AUTHOR]

Many computational methods have been applied to interpret and predict changes in reactivity by slight modifications of a given molecular scaffold. We describe a novel and simple method based on approximate density-functional theory of valence electrons that can be applied within a large high-performance computational infrastructure to probe such changes using a statistical sample of molecular configurations, including the solvent. All the used computational tools are fully open-source. Following our previous application, we are able to explain the high acidity of C-H bond at  α  position in nitro compounds when the amide linkage an ammonium group is inserted into the  α  substituent. [ABSTRACT FROM AUTHOR]

[Display omitted] The two-step synthesis of porphyrin derivatives, exhaustively bbb-substituted at the 'Eastern half', starting from meso- tetraarylporphyrin chelates (Cuii, Znii, Niii) upon their reaction with nitric acid, is described. The intermediates obtained (mainly dinitro-derivatives) in the reaction with carbanions bearing a leaving group X at the reactive centre give tetrasubstituted at the bbb-positions products, the ones of vicarious nucleophilic substitution of hydrogen. The products seem to be potential anticancer PDT agents, practically unavailable by other methods. [ABSTRACT FROM AUTHOR]

Transition metal-free carbonyl directed boron-Wittig reaction of α-bis(boryl)carbanions with the corresponding isatins or with the α-keto esters/amides was achieved to access alkenyl oxindoles in good yield and high stereoselectivity. [ABSTRACT FROM AUTHOR]

Direct transition-metal free bond activation and bond formation reaction are central to the development of a sustainable and effective strategy for the synthesis of organic molecules. Facile, aerobic, regiospecific, base-mediated transition metal-free, and direct arylation reactions with inexpensive nitroarenes are need to explore. The use of strong base, promotes the vicarious nucleophilic substitution in nitroarenes. Moreover, functional group modification of synthesized nitroarenes compounds can open myriad applications in pharmaceutical and material industries. In this review, we summarize the recent progress achieved in the transition metal-free, base-mediated methodology has been employed for mono arylation, di-arylation, acylation, and aroylation reactions and we cover the research literature from 2013 to 2022. This review article presents the advantages, limitations, mechanistic rationalization, and future perspectives associated with synthetic methodologies. [ABSTRACT FROM AUTHOR]

Herein, electrochemical reductive carboxylation of para‐quinone methides with CO2 was developed. A variety of value‐added carboxylic acids can be accessed in moderate to excellent yields. Preliminary studies showed that para‐quinone methides were reduced to benzyl carbanion during the reaction. This protocol features high atom economy, operational simplicity, and environmental friendliness, enabling the synthesis of various carboxylic compounds. [ABSTRACT FROM AUTHOR]

Herein, electrochemical reductive carboxylation of para‐quinone methides with CO2 was developed. A variety of value‐added carboxylic acids can be accessed in moderate to excellent yields. Preliminary studies showed that para‐quinone methides were reduced to benzyl carbanion during the reaction. This protocol features high atom economy, operational simplicity, and environmental friendliness, enabling the synthesis of various carboxylic compounds. [ABSTRACT FROM AUTHOR]

The functional group transformation associated with nitrile moiety is considered a diligent research topic in the synthetic community as it is a building block for several organic molecules, including ketones and amides. Many synthetic methodologies have been developed for synthesizing ketones and amides, considering them synthetic analogues with exciting biological properties. However, there are limited research articles to synthesize these important classes of compounds via oxidative decyanation of nitriles and α‐aminonitriles. As several protocols are developed in decyanation, base‐induced oxidative decyanation of nitrile functionality to the oxo group via a carbanion formation is an effective but under‐explored area of research. In this context, we wish to present an outline of studies in oxidative decyanation of secondary nitriles and α‐aminonitriles to afford corresponding ketones and amides since its inception. [ABSTRACT FROM AUTHOR]

The review briefly describes the synthetic potential of acetylenic and allenic carbanion adducts with isothiocyanates and azatriene systems based thereon as precursors to fundamental aza- and thiaheterocycles, namely pyrroles, 2,3-dihydropyridines, pyridines, quinolines, 3H-azepines, 4,5-dihydro-3H-azepines, 2-azabi-cyclo[3.2.0]hept-2-enes, thietanes, thiophenes, thiophen-2(5H)-imines, 1,3-thiazoles, 4,5-dihydro-1,3-thiazoles, and other heterocyclic structures with rare and/or difficultly introducible functional and pharmacophoric substituents. [ABSTRACT FROM AUTHOR]

[Display omitted] Arylacetylenes readily react with aromatic aldazines in superbase medium NaOBut/DMSO (1 vol% EtOH) at room temperature to afford mainly 4-arylmethyl-3,5-diaryl-1 H - pyrazoles in up to 47% yield along with minor amounts of 1-arylmethyl-3,5-diaryl-1 H -pyrazoles and 1,2-diaryl-1,2- bis(3,5-diaryl-1 H -pyrazol-1-yl)ethanes. The reaction is rationalized as proceeding via the diazaallyl anions, the adducts of acetylenic carbanions to a C=N bond, which further undergo the proton transfer processes and intramolecular cyclization to the above pyrazole derivatives. [ABSTRACT FROM AUTHOR]

During the past decade, carbon (C−H) acids depicted as 'Tf2CHR' (Tf=CF3SO2) have attracted considerable attention as a new class of superacidic molecules, which show stronger acidity than sulfuric acid molecules. In recent years, the author has developed a synthetic methodology for such strong acids and has opened the door to chemistry of highly stabilised carbanions [Tf2CR]−, which are the conjugate bases of the carbon acids. These carbanion‐containing salts are stable and easy‐to‐handle species. Our efforts have revealed that the ionic but lipophilic characters of this type of carbanion can be used as a unique 'substituent' for increasing both the water solubility and the lipophilicity of organic compounds. This Personal Account provides an overview of our [Tf2CR]− chemistry, including its synthesis, structure, reactivity, and applications. [ABSTRACT FROM AUTHOR]

In this study, 1′,2′‐dihydroxy‐3,4‐benzotropolone (BTP), the simplest theaflavins (TFs) derivative, is synthesized via the oxidative coupling of pyrogallol (PG) and catechol (CC). We show that low temperature was beneficial to the production of BTP. A possible generation mechanism of the key bicyclo[3.2.1]octane‐type intermediate (BOI) during the formation process of BTP was subsequently proposed. Our analysis based on quantum chemical calculations indicated that three types of tautomers of PG quinones should be present in the reaction solution. Among them, PG quinone tautomer III (PGQT‐III) with two carbanions might be one of the direct substrates for BOI synthesis, which underwent 1,6‐addition reaction to C3‐C4 bond of ortho‐quinone with strong electrophilicity leading to the key intermediate. Furthermore, the presence of PGQT‐III was also supported by the retrosynthetic analysis of BOI. The findings not only shed light on the production mechanism of BTP, but also create new prospects in synthesizing TFs with controllable products. [ABSTRACT FROM AUTHOR]

The racemization of biomolecules in the active site can reduce the biological activity of drugs, and the mechanism involved in this process is still not fully comprehended. The present study investigates the impact of aromaticity on racemization using advanced theoretical techniques based on density functional theory. Calculations were performed at the ωb97xd/6-311++g(d,p) level of theory. A compelling explanation for the observed aromatic stabilization via resonance is put forward, involving a carbanion intermediate. The analysis, employing Hammett's parameters, convincingly supports the presence of a negative charge within the transition state of aromatic compounds. Moreover, the combined utilization of natural bond orbital (NBO) analysis and intrinsic reaction coordinate (IRC) calculations confirms the pronounced stabilization of electron distribution within the carbanion intermediate. To enhance our understanding of the racemization process, a thorough examination of the evolution of NBO charges and Wiberg bond indices (WBIs) at all points along the IRC profile is performed. This approach offers valuable insights into the synchronicity parameters governing the racemization reactions. [ABSTRACT FROM AUTHOR]

In this paper, the anionic hyperconjugation occurring in alkyl and fluorinated carbanions in the gaseous phase is examined at density functional theory (DFT) at the level of theory B3LYP/6‐31++G (d,p) with empirical dispersion‐GD3 theory. First, a contribution of this study is to confirm that the C‐H bond in (CH3)3C‐H (isobutane) is more acidic than the C‐H bonds in CH3CH2‐H (ethane) and (CH3)2CH‐H (propane) based on a comparison of conjugate base stability. Also, the natural population analysis (NPA) and CHELPG methods are well‐performed for calculating charge distribution on carbon atoms, and in contrast, the Mulliken population is better for hydrogen atoms to describe the anionic hyperconjugation in the valence bond (VB) model. The molecular orbital model accounts for the stability order of alkyl and perfluorinated carbanions through the number, strength, and overlap geometry between the lone electron pair on carbon atom and the vicinal σ*C‐H/σ*C‐F orbitals. On the other hand, the utility of VB theory becomes invalid because of the strong inductive effect of the fluorine element and the steric repulsion among CF3 groups in perfluorinated carbanions. Also, the hybridization of the carbon atom holding the lone electron pair can become more s‐character or p‐character dependent on the size of surrounding groups. [ABSTRACT FROM AUTHOR]

In continuation of our research program to develop original synthetic methods using TDAE methodology on nitroheterocyclic substrates, we were able to generate for the first time a stable carbanion in position 2 of the 5-nitroimidazole scaffold. Starting from a 2-chloromethyl-4-phenylsulfonylmethyl-5-nitroimidazole intermediate, prepared by the vicarious nucleophilic substitution of hydrogen (VNS) reaction, we selectively introduced a N-tosylbenzylimine moiety at position 2 without reducing the sulfone at position 4, leading to the formation of N-[1-(2-chlorophenyl)-2-{1-methyl-5-nitro-4-[(phenylsulfonyl)methyl]-1H-imidazol-2-yl}ethyl]-4-methylbenzenesulfonamide in 47% yield. This new synthetic method using TDAE should allow access to new 2-substituted 5-nitroimidazole derivatives with various electrophiles such as carbonyls and other N-tosylbenzylimines. [ABSTRACT FROM AUTHOR]

The direct synthesis of sterically hindered aldehydes is highly challenging. Herein, we report a direct approach to generate such compounds via electroreductive cleavage of the C(sp3)–O bond of activated alcohols. Under the established reaction conditions, benzylic radical intermediates were efficiently generated. A subsequent radical–polar crossover generated carbanions that further reacted with N,N-dimethylformamide to form various aldehydes with tertiary or quaternary benzylic carbon centers. The feasibility of a gram-scale synthesis was also demonstrated. This reaction is also operated in a simple undivided cell, which avoids the use of any transition metal catalysts, toxic gas, and reductants. [ABSTRACT FROM AUTHOR]

The flavoenzyme glycolate oxidase oxidizes glycolic acid to glyoxylate and the latter, more slowly, to oxalate. It is a member of an FMN‐dependent enzyme family that oxidizes l‐2‐hydroxy acids to keto acids. There has been a controversy concerning the chemical mechanism of substrate oxidation by these enzymes. Do they proceed by hydride transfer, as observed for NAD‐dependent enzymes, or by initial formation of a carbanion that transfers the electrons to the flavin? The present work describes a comparison of the reactivity of glycolate, lactate and trifluorolactate with recombinant human glycolate oxidase, by means of rapid‐kinetics experiments in anaerobiosis. We show that trifluorolactate is a substrate for glycolate oxidase, whereas it is known as an inhibitor for NAD‐dependent enzymes, as is trifluoroethanol for NAD‐dependent alcohol dehydrogenases. Unexpectedly, it was observed that, once reduced, a flavin transfers an electron to an oxidized flavin, so that the end species is a flavin semiquinone, whatever the substrate. This phenomenon has not previously been described for a glycolate oxidase. Altogether, considering that another member of this flavoenzyme family (flavocytochrome b2, a lactate dehydrogenase) has also been shown to oxidize trifluorolactate (Lederer F et al. (2016) Biochim Biophys Acta 1864, 1215–21), this work provides another important piece of evidence which is hardly compatible with a hydride transfer mechanism for this flavoenzyme family. [ABSTRACT FROM AUTHOR]

For better understanding the intrinsic reactivity of organozinc reagents, we have examined the protolysis of the isolated zincate ions Et3Zn−, Et2Zn(OH)−, and Et2Zn(OH)2Li− by 2,2,2‐trifluoroethanol in the gas phase. The protonation of the hydroxy groups and the release of water proceed much more efficiently than the protonation of the ethyl groups and the liberation of ethane. Quantum‐chemical computations and statistical‐rate theory calculations fully reproduce the experimental findings and attribute the lower reactivity of the more basic ethyl moiety to higher intrinsic barriers, which override the thermodynamic preference for its protonation. Thus, our minimalistic gas‐phase model provides evidence for the intrinsically low reactivity of organozinc reagents toward proton donors and helps to explain their remarkable kinetic stability against moisture and even protic media. [ABSTRACT FROM AUTHOR]

Visible‐light photocatalytic carboxylation with CO2 is highly important. However, it still remains challenging for reluctant substrates with low reduction potentials. Herein, we report a novel photocatalytic carboxylation of C−N bonds in cyclic amines with CO2 via consecutive photo‐induced electron transfer (ConPET). It is also the first photocatalytic reductive ring‐opening reaction of azetidines, pyrrolidines and piperidines. This strategy is practical to transform a variety of easily available cyclic amines to valuable β‐, γ‐, δ‐ and ϵ‐amino acids in moderate‐to‐excellent yields. Moreover, the method also features mild and transition‐metal‐free conditions, high selectivity, good functional‐group tolerance, facile scalability and product derivations. Mechanistic studies indicate that the ConPET might be the key to generating highly reactive photocatalysts, which enable the reductive activation of cyclic amines to generate carbon radicals and carbanions as the key intermediates. [ABSTRACT FROM AUTHOR]

Anionic polymerizations are of exceptional practical importance, but difficult to analyze due to the high reactivity of the growing polymer chains. Here, we demonstrate that electrospray‐ionization mass spectrometry (ESI‐MS) permits direct observation of the active carbanionic intermediates formed in the anionic ring‐opening polymerization of 1‐cyanocyclopropanecarboxylate in tetrahydrofuran. This includes the identification of a side product, as well as real‐time analysis of the polymerization reaction. From the mass spectra obtained, we can derive not only the mean molar mass and the polydispersity, but also the rate constants for the initiation and the individual propagation steps. The initiation proceeds significantly faster than the propagation steps. Accordingly, the examined reaction corresponds to a living polymerization, as we also confirmed by additional control experiments. Besides giving detailed insight into the reaction system probed here, we also expect the presented methodology to make possible the in‐situ analysis of further anionic polymerizations. [ABSTRACT FROM AUTHOR]

It has been found that the addition of CH2CN− anion to the carbonyl group of acylethynylpyrroles, generated from acetonitrile and t-BuOK, results in the formation of acetylenic alcohols, which undergo unexpectedly easy (room temperature) decomposition to ethynylpyrroles and cyanomethylphenylketones (retro-Favorsky reaction). This finding allows a robust synthesis of ethynylpyrroles in up to 95% yields to be developed. Since acylethynylpyrroles became available, the strategy thus found makes ethynylpyrroles more accessible than earlier. The quantum-chemical calculations (B2PLYP/6-311G**//B3LYP/6-311G**+C-PCM/acetonitrile) confirm the thermodynamic preference of the decomposition of the intermediate acetylenic alcohols to free ethynylpyrroles rather than their potassium derivatives. [ABSTRACT FROM AUTHOR]

Herein, the first stable anions K[SIPrBp] (4 a‐K) and K[IPrBp] (4 b‐K) (SIPrBp=BpC{N(Dipp)CH2}2, IPrBp=BpC{N(Dipp)CH}2; Bp=4‐PhC6H4; Dipp=2,6‐iPr2C6H3) derived from classical N‐heterocyclic carbenes (NHCs) (i.e. SIPr and IPr) have been isolated as violet crystalline solids. 4 a‐K and 4 b‐K are prepared by KC8 reduction of the neutral radicals [SIPrBp] (3 a) and [IPrBp] (3 b), respectively. The radicals 3 a and 3 b as well as [Me‐IPrBp] 3 c (Me‐IPrBp=BpC{N(Dipp)CMe}2) are accessible as crystalline solids on treatment of the respective 1,3‐imidazoli(ni)um bromides (SIPrBp)Br (2 a), (IPrBp)Br (2 b), and (Me−IPrBp)Br (2 c) with KC8. The cyclic voltammograms of 2 a–2 c exhibit two one‐electron reversible redox processes in −0.5 to −2.5 V region that correspond to the radicals 3 a–3 c and the anions (4 a–4 c)−. Computational calculations suggest a closed‐shell singlet ground state for (4 a–4 c)− with the singlet‐triplet energy gap of 17–24 kcal mol−1. [ABSTRACT FROM AUTHOR]

Electrophilic and nucleophilic substitutions of aromatic substrates share common mechanistic pathways. In both scenarios reacting species attack rings at the unsubstituted (C–H) positions, giving cationic Wheland intermediates or anionic Meisenheimer complexes. However, the following step of rearomatization breaks the intrinsic symmetry, due to different leaving group ability of proton and hydride anion, respectively. In effect, electron-deficient arenes are prone to transformations unparalleled in electrophilic chemistry. In our article, we present transformations of anionic σH-adducts, formed between nitroarenes and carbanions of the Corey–Chaykovsky reagents. Depending on structure of the substrates and reaction conditions, the intermediates undergo cyclization to cyclopropanes (norcaradienes) or base-induced elimination to the alkylated products. Mechanistic studies reveal that order of the carbanions controls competition between the processes, due to steric hindrance developing at the β-elimination step. 1 Introduction 2 Cyclopropanation of Nitronaphthalenes 3 Alkylation of Nitropyridines 4 Mechanistic Studies 5 Summary and Outlook [ABSTRACT FROM AUTHOR]

Difluoromethylenefullerenes belonging to structurally flexible bridged fullerene derivatives have a rare distinctive feature, viz., insertion of CF2 group into the C=C bond of the fullerene cage is accompanied by electrocyclic rearrangement with the formation of unusual products termed homofullerenes. This makes the electron-withdrawing properties more pronounced, has a decisive influence on the chemical properties of compounds in the neutral and anionic states, and facilitates cleavage of the C—C bond between the bridgehead carbon atoms. Depending on the local environment of the difluoromethylene group and on the charge state, the distance between the bridgehead carbon atoms in difluoromethylenefullerenes changes from 1.7 Å to 2.3 Å, which is accompanied by transformation of the cyclopropane moiety to the bridging fragment. Methods of synthesis, the molecular and electronic structure, chemical properties, and potential application fields of difluoromethylenefullerenes are considered. [ABSTRACT FROM AUTHOR]

• Least understood lead carbon complex species (Pb–C–) synthesized. • Influence of lead carbanion complexes on photoelectric properties of perovskite solar cells explored. • Carbanion reacts with undercoordinated Pb2+ on perovskite surface. • Solar cell efficiency boosted by the growth of even perovskite films with defects reduction. In this study, we synthesize lead carbanion complex to act as interface passivator for inverted perovskite solar cells. The strong Pb–C− bond between carbanion and lead-rich perovskite surface can stabilize the underlying perovskite to reduce defects and hence enhance photovoltaic performance. The carrier transfer behavior as a function of the lead carbanion complex was measured to optimize device performance by surface passivation. The devices achieved a power conversion efficiency of 25.16 % with a high open-circuit voltage of 1.17 V and a minimal voltage loss of 0.38 V. The perovskite solar cells with carbanion passivation maintained high performance over 600 h and had a lifespan in air exceeding 90 days without encapsulation. Our work introduces a new class of carbanion passivators to simultaneously improve the efficiency and stability of perovskite solar cells. [ABSTRACT FROM AUTHOR]