Synthesis of Indoles through Domino Reactions of 2-Fluorotoluenes and Nitriles

Recent advances in electrochemically enabled construction of indoles from non-indole-based substrates

Indole motifs are important heterocycles found in natural products, pharmaceuticals, agricultural chemicals, and materials. Although there are well-established classical name reactions for indole synthesis, these transformations often require harsh reaction conditions, have a limited substrate scope, and exhibit poor regioselectivity. As a result, organic synthesis chemists have been exploring efficient and practical methods, leading to numerous strategies for synthesizing a variety of functionalized indoles. In recent years, electrochemistry has emerged as an environmentally friendly and sustainable synthetic tool, with widespread applications in organic synthesis. This technology allows for elegant synthetic routes to be developed for the construction of indoles under external oxidant-free conditions. This feature article specifically focuses on recent advancements in indole synthesis from non-indole-based substrates, as well as the mechanisms underlying these transformations.

Construction of 2-Substituted-3-aryl Benzofurans and Indoles through an Acid-Catalyzed Cascade Intramolecular Friedel-Crafts Reaction/Rearrangement/Aromatization Process

We present here a new method for the synthesis of 2-substituted-3-aryl benzoheterocycles through a more challenging constrained [1,5]-type Friedel-Crafts reaction/rearrangement and aromatization process. By using the readily available 2-aryoxy-1,3-indandiones and 2-arylamino-1,3-indandiones, a range of 2-substituted-3-aryl benzofurans and indoles were prepared in good to excellent yields (yields up to 86%) under the catalysis of CF3SO3H or Sm(OTf)3. Compared with previous methods for constructing similar structures, this approach offers several advantages, including the use of easily accessible starting materials, mild reaction conditions, high yield, excellent regio- and diastereoselectivity, and a broad substrate scope.

Recent progress in energy-saving electrocatalytic hydrogen production via regulating the anodic oxidation reaction

Hydrogen energy with its advantages of high calorific value, renewable nature, and zero carbon emissions is considered an ideal candidate for clean energy in the future. The electrochemical decomposition of water, powered by renewable and clean energy sources, presents a sustainable and environmentally friendly approach to hydrogen production. However, the traditional electrochemical overall water-splitting reaction (OWSR) is limited by the anodic oxygen evolution reaction (OER) with sluggish kinetics. Although important advances have been made in efficient OER catalysts, the theoretical thermodynamic difficulty predetermines the inevitable large potential (1.23 V vs. RHE for the OER) and high energy consumption for the conventional water electrolysis to obtain H2. Besides, the generation of reactive oxygen species at high oxidation potentials can lead to equipment degradation and increase maintenance costs. Therefore, to address these challenges, thermodynamically favorable anodic oxidation reactions with lower oxidation potentials than the OER are used to couple with the cathodic hydrogen evolution reaction (HER) to construct new coupling hydrogen production systems. Meanwhile, a series of robust catalysts applied in these new coupled systems are exploited to improve the energy conversion efficiency of hydrogen production. Besides, the electrochemical neutralization energy (ENE) of the asymmetric electrolytes with a pH gradient can further promote the decrease in application voltage and energy consumption for hydrogen production. In this review, we aim to provide an overview of the advancements in electrochemical hydrogen production strategies with low energy consumption, including (1) the traditional electrochemical overall water splitting reaction (OWSR, HER-OER); (2) the small molecule sacrificial agent oxidation reaction (SAOR) and (3) the electrochemical oxidation synthesis reaction (EOSR) coupling with the HER (HER-SAOR, HER-EOSR), respectively; (4) regulating the pH gradient of the cathodic and anodic electrolytes. The operating principle, advantages, and the latest progress of these hydrogen production systems are analyzed in detail. In particular, the recent progress in the catalytic materials applied to these coupled systems and the corresponding catalytic mechanism are further discussed. Furthermore, we also provide a perspective on the potential challenges and future directions to foster advancements in electrocatalytic green sustainable hydrogen production.

Dual Basicity and Nucleophilicity of Organosodium Reagents in Benzylic C-H Additions of Toluenes to Diarylethenes and Ketones

Profiting from the dual high basicity and nucleophilicity of organosodium complexes, here we report the stepwise lateral metalation of a wide range of alkyl arenes (MeAr), mediated by hydrocarbon-soluble NaCH2SiMe3 ⋅ PMDETA (PMDETA=N,N,N',N'',N''-pentamethyldiethylenetriamine), followed by nucleophilic addition to diarylethenes of the newly generated NaCH2Ar ⋅ PMDETA complexes. This method grants access to a range of functionalised hydrocarbons in excellent yields and can be upgraded to catalytic regimes when using trans-stilbene, a 10 mol% of the alkyl sodium base and toluene as a solvent. Extending this approach to aromatic ketones leads to the formation of stilbenes under mild reaction conditions, resulting from the deprotonative coupling of toluenes with ketones. Combining spectroscopic studies with the trapping and characterisation of key reaction intermediates, mechanistic insights have been gained, advancing the understanding of coordination effects in organosodium chemistry, and shedding light on their special reactivity profiles.

Base-Promoted (5 + 2) Annulation between 2-(Alkynylaryl)acetonitriles and Arylalkynes for the Synthesis of Benzocycloheptene Derivatives

Herein, we describe a novel approach to the synthesis of benzocycloheptene derivatives via base-promoted (5 + 2) annulation between 2-(alkynylaryl)acetonitriles and arylalkynes. In this chemistry, 2-(alkynylaryl)acetonitriles are employed as a new C5 synthon to construct various benzocycloheptene(s) derivatives by building two C-C bonds in one single step. This method features excellent regioselectivity, the use of readily available starting materials, and good functional group tolerance. The practicality of the strategy was further demonstrated by gram-scale synthesis, late-stage functionalizations, and the post-modification of natural products such as probenecid and tetrahydrofurfuryl alcohol.

Synthesis of Indolines via Base-Mediated C-H Activation and Defluorinative C-N Coupling, with no Need for Transition-Metals

Syntheses of (partially) aromatic nitrogen heterocycles increasingly rely on transition-metal catalyzed C-C- and C-N-cross-coupling reactions. Here we describe a different approach to the synthesis of indolines by a domino C(sp3)-H activation, 1,2-addition, and defluorinative SNAr-cyclization sequence to provide the target 1,2-diarylindolines (1,2-diaryl-2,3-dihydroindoles) from ortho-fluorinated methyl-arenes and N-aryl imines (benzylidene anilines) in a cyclocondensation that is mediated by potassium hexamethyldisilazide (KHMDS) as base exclusively. This transition-metal-free process via C-H and C-F bond activation provides a one-step entry into a wide array of indoline scaffolds (43 examples, up to 96 % yield). This privileged substructure is common in natural products and pharmaceuticals alike, and cannot be accessed by traditional condensation reactions.

One-Pot Synthesis of Indolin-3-ones Mediated by LiN(SiMe3)2/CsF

Indolin-3-ones are essential heterocycles with wide-ranging biological activities and medicinal values, and therefore, efficient approaches to their synthesis remain in demand. Herein, a novel and operationally simple method to generate indolin-3-ones is reported by using a tandem reaction of N-methylbenzylamines and methyl 2-fluorobenzoates mediated by the LiN(SiMe3)2 and CsF system (34 examples, 30-85% yields). The synthesis of C2-quaternary indolin-3-one further demonstrated the potential practicability of these tandem reactions.

Dipolar Microenvironment Engineering Enabled by Electron Beam Irradiation for Boosting Catalytic Performance

Creating a diverse dipolar microenvironment around the active site is of great significance for the targeted induction of intermediate behaviors to achieve complicated chemical transformations. Herein, an efficient and general strategy is reported to construct hypercross-linked polymers (HCPs) equipped with tunable dipolar microenvironments by knitting arene monomers together with dipolar functional groups into porous network skeletons. Benefiting from the electron beam irradiation modification technique, the catalytic sites are anchored in an efficient way in the vicinity of the microenvironment, which effectively facilitates the processing of the reactants delivered to the catalytic sites. By varying the composition of the microenvironment scaffold structure, the contact and interaction behavior with the reaction participants can be tuned, thereby affecting the catalytic activity and selectivity. As a result, the framework catalysts produced in this way exhibit excellent catalytic performance in the synthesis of glycinate esters and indole derivatives. This manipulation is reminiscent of enzymatic catalysis, which adjusts the internal polarity environment and controls the output of products by altering the scaffold structure.

Masters of Mediation: MN(SiMe3)2 in Functionalization of C(sp3)-H Latent Nucleophiles

Organoalkali compounds have undergone a far-reaching transformation being a coupling partner to a mediator in unusual organic conversions which finds its spot in the field of sustainable synthesis. Transition-metal catalysis has always been the priority in C(sp3)-H bond functionalization, however alternatively, in recent times this has been seriously challenged by earth-abundant alkali metals and their complexes arriving at new sustainable organometallic reagents. In this line, the importance of MN(SiMe3)2 (M=Li, Na, K & Cs) reagent revived in C(sp3)-H bond functionalization over recent years in organic synthesis is showcased in this minireview. MN(SiMe3)2 reagent with higher reactivity, enhanced stability, and bespoke cation-π interaction have shown eye-opening mediated processes such as C(sp3)-C(sp3) cross-coupling, radical-radical cross-coupling, aminobenzylation, annulation, aroylation, and other transformations to utilize readily available petrochemical feedstocks. This article also emphasizes the unusual reactivity of MN(SiMe3)2 reagent in unreactive and robust C-X (X=O, N, F, C) bond cleavage reactions that occurred alongside the C(sp3)-H bond functionalization. Overall, this review encourages the community to exploit the untapped potential of MN(SiMe3)2 reagent and also inspires them to take up this subject to even greater heights.

Base-Promoted Synthesis of Isoquinolines through a Tandem Reaction of 2-Methyl-arylaldehydes and Nitriles

A convenient method for preparing 3-aryl isoquinolines via a base-promoted tandem reaction is presented. Simply combining commercially available 2-methyl-arylaldehydes, benzonitriles, NaN(SiMe3)2, and Cs2CO3 enabled the synthesis of a variety of isoquinolines (23 examples, ≤90% yield). Among the syntheses of isoquinolines, the transition metal-free method described here is straightforward, practical, and operationally simple.

Alkaline-Metal-Promoted Divergent Synthesis of 1-Aminoisoquinolines and Isoquinolines

Alkaline-metal-promoted divergent syntheses of 1-aminoisoquinolines and isoquinolines have been reported involving 2-methylaryl aldehydes, nitriles, and LiN(SiMe3)2 as reactants. In addition, the three-component reaction of 2-methylaryl nitriles, aldehydes, and LiN(SiMe3)2 has been developed to furnish 1-aminoisoquinolines. This protocol features readily available starting materials, excellent chemoselectivity, broad substrate scope, and satisfactory yields.

Interfacial Micro-Environment of Electrocatalysis and Its Applications for Organic Electro-Oxidation Reaction

Conventional designing principal of electrocatalyst is focused on the electronic structure tuning, on which effectively promotes the electrocatalysis. However, as a typical kind of electrode-electrolyte interface reaction, the electrocatalysis performance is also closely dependent on the electrocatalyst interfacial micro-environment (IME), including pH, reactant concentration, electric field, surface geometry structure, hydrophilicity/hydrophobicity, etc. Recently, organic electro-oxidation reaction (OEOR), which simultaneously reduces the anodic polarization potential and produces value-added chemicals, has emerged as a competitive alternative to oxygen evolution reaction, and the role IME played in OEOR is receiving great interest. Thus, this article provides a timely review on IME and its applications toward OEOR. In this review, the IME for conventional gas-involving reactions, as a contrast, is first presented, and then the recent progresses of IME toward diverse typical OEOR are summarized; especially, some representative works are thoroughly discussed. Additionally, cutting-edge analytical methods and characterization techniques are introduced to comprehensively understand the role IME played in OEOR. In the last section, perspectives and challenges of IME regulation for OEOR are shared.

Base-promoted tandem synthesis of 2-azaaryl indoline

A novel tandem method to synthesize 2-azaaryl indoline promoted by LiN(SiMe3)2 from 2-azaaryl methyl amine and 2-fluoro benzyl bromides was developed. Mechanistic investigation indicated that this tandem cyclization was initiated by selective benzyl C-SN2 substitution followed by an intramolecular SNAr reaction. Diverse 2-azaaryl indoles could also be obtained via simple functional transformations.

A Tandem Madelung Indole Synthesis Mediated by a LiN(SiMe3)2/CsF System

A tandem Madelung indole synthesis by the reaction of methyl benzoate and N-methyl-o-toluidine has been discovered. The combination of LiN(SiMe3)2 with CsF is the key factor, which secures the high efficiency of such tandem transformations. Simply combining methyl benzoate, N-methyl-o-toluidine LiN(SiMe3)2, and CsF generated a diverse array of N-methyl-2-phenylindoles (31 examples, 50-90% yields). Furthermore, the scalability and the poststructural modifications of this indole synthesis were demonstrated.

LiHMDS-Mediated Deprotonative Coupling of Toluenes with Ketones

We demonstrate that lithium hexamethyldisilazide (LiHMDS) acts as an effective base for deprotonative coupling reactions of toluenes with ketones to afford stilbenes. Various functionalities (halogen, OCF₃ , amide, Me, aryl, alkenyl, alkynyl, SMe, and SPh) are allowed on the toluenes. Notably, this system proved successful with low-reactive toluenes bearing a large pKa value compared to that of the conjugate acid of LiHMDS (hexamethyldisilazane, 25.8, THF), as demonstrated by 4-phenyltoluene (38.57, THF) and toluene itself (∼43, DMSO).

Palladium-Catalyzed Tandem Nucleophilic Addition/C-H Functionalization of Anilines and Bromoalkynes for the Synthesis of 2-Phenylindoles

A novel and efficient palladium-catalyzed annulation of anilines with bromoalkynes for the synthesis of 2-phenylindoles has been described. This approach features excellent regio- and stereoselectivities and good functional group tolerance. Preliminary mechanistic studies indicate that anilines undergo anti-nucleophilic addition to bromoalkynes to generate (Z)-N-(2-bromo-1-phenylvinyl) anilines, followed by sequential C-H functionalization to deliver different substituted 2-phenylindoles. This method provides potential applications for the construction of various biologically active compounds.

Research progress on the structure and biological diversities of 2-phenylindole derivatives in recent 20 years

The privileged structure binds to multiple receptors with high affinity, which is helpful to the development of new bioactive compounds. Indole is classified as a privileged structure, which may be one of the most important structural categories in drug discovery. As a special subset of indole compounds, 2-phenylindole seems to be one of most promising forerunners of drug development. In this paper, 106 articles were referenced to review the structural changes, biological activities and structure-activity relationship of compounds in recent 20 years, and classified them according to their pharmacological activities, from several aspects, including anticancer, antibacterial, anti-inflammatory, analgesic, antiviral, anti-parasite, the biological activities target to central nervous system, et al. It also points out the importance of artificial intelligence (AI) technology in discovery of new 2-phenylindole compounds in a broader prospect. This review will provide some ideas for researchers to develop new indole drugs.

Cesium Amide-Catalyzed Selective Deuteration of Benzylic C-H Bonds with D2 and Application for Tritiation of Pharmaceuticals

Hydrogen isotope exchange (HIE) represents one of the most attractive labeling methods to synthesize deuterium- and tritium-labeled compounds. Catalytic HIE methods that enable site-selective C-H bond activation and exchange labeling with gaseous isotopes D₂ and T₂ are of vital importance, in particular for high-specific-activity tritiation of pharmaceuticals. As part of our interest in exploring s-block metals for catalytic transformations, we found CsN(SiMe₃ )₂ to be an efficient catalyst for selective HIE of benzylic C-H bonds with D₂ gas. The reaction proceeds through a kinetic deprotonative equilibrium that establishes an exchange pathway between C-H bonds and D₂ gas. By virtue of multiple C-H bonds activation and high activity (isotope enrichment up to 99 %), the simple cesium amide catalyst provided a very powerful and practically convenient labeling protocol for synthesis of highly deuterated compounds and high-specific-activity tritiation of pharmaceuticals.

Synthesis of 3-Haloindoles via Cascade Oxidative Cyclization/Halogenation of 2-Alkenylanilines Mediated by PIDA and LiBr/KI

The treatment of 2-alkenylanilines with phenyliodine(III) diacetate (PIDA) and LiBr or KI in HFIP was found to afford the corresponding 3-haloindoles via cascade oxidative cyclization/halogenation encompassing oxidative C-N/C-X (X = Br, I) bond formations. A plausible mechanism involving the in situ formation of the reactive AcO-X (X = Br, I) from the reaction of PIDA and LiBr/KI was postulated.

One-Pot Domino Reaction: Direct Access to Polysubstituted 1,4-Benzothiazine 1,1-Dioxide via Water-Gas Shift Reaction Utilizing DMF/H2O

Benzothiazine 1,1-dioxide (BTDO) is a privileged chemical motif, and its metal-free domino access is in high demand. Current BTDO production methods require costly metal catalysts or harsh reaction conditions. A facile domino approach to BTDO via a water-gas shift reaction (WGSR) employing sodium 2-nitrobenzenesulfinates and α-bromo ketones is presented. This strategy is cost-effective and environmentally beneficial. The optimized reaction conditions demonstrated remarkable chemical tolerance to a wide range of electrically and sterically varied substituents on both coupling partners.

Synthesis of Indoles via Domino Reactions of 2-Methoxytoluene and Nitriles

2-Arylindoles are privileged structures widely present in biologically active molecules. New sustainable synthetic routes toward their synthesis are, therefore, in high demand. Herein, a mixed base-promoted benzylic C-H deprotonation of commercially available ortho-anisoles, addition of the resulting anion to benzonitriles, and S_NAr to displace the methoxy group provide indoles. A diverse array of 2-arylindoles is prepared with good yields (>30 examples, yields up to 99%) without added transition metal catalysts.

α-Iminyl Cation-Involved Indole Construction via Brønsted Acid-Promoted Reaction of Isoxazol-5-ones

Herein, we report a strategically novel method for the efficient construction of indole skeletons using 2-phenylisoxazol-5-ones as the starting material. This reaction proceeds via Brønsted acid-promoted α-iminyl cation generation by N-O bond cleavage and a subsequent intramolecular cyclization to afford 1H-indole-3-carboxylic acid, which further undergoes decarboxylation to yield the final product. Control experiments show that N-O bond cleavage and intramolecular cyclization proceed so fast that the 1H-indole-3-carboxylic acid could be isolated in high yields even after 5-10 min. The substrate scope of this transformation is broad, and the desired products are obtained in moderate to good yields. The transition-metal-free reaction condition, CO₂ as the sole byproduct, and good practicability add to the synthetic potential of this transformation in the pharmaceutical and flavor industries.

In Situ Chalcogen Leaching Manipulates Reactant Interface toward Efficient Amine Electrooxidation

Engineering the reaction interface is necessary for advancing various electrocatalytic processes. However, most designed catalysts tend to be ineffective due to the inevitable structural reconstruction. Here we utilize that operando electrocatalysis variations (i.e., chalcogen leaching) manipulate the reactant interface toward amine electrooxidation. Taking chalcogen-doped Ni(OH)₂ as an example, operando techniques uncover that chalcogens leach from the matrix and then adsorb on the surface of NiOOH as chalcogenates during the electrooxidation process. The charged chalcogenates will induce the local electric field that pushes the polar amines through the inner Helmholtz plane to enrich on the catalyst surface. Meanwhile, the polarization effect of chalcogenates and amines boost amino C-N bond activation for dehydrogenation into nitrile C≡N bonds. Under the promotion effect of surface-adsorbed chalcogenate ions, our catalysts display over 99.5% propionitrile selectivity at the low potential of 1.317 V with an ultrahigh current density. This finding highlights the use of operando changes of catalysts to rationally design efficient catalysts and further clarifies the underlying role of chalcogen atoms in the electrooxidation process.

Synthesis of Tryptamines from Radical Cyclization of 2-Iodoaryl Allenyl Amines and Coupling with 2-Azallyls

An efficient synthesis of tryptamines is developed. Indole structures were constructed using 2-iodoaryl allenyl amines as electron acceptors and radical cyclization precursors. Radical-radical coupling of indolyl methyl radicals and azaallyl radicals led to the tryptamine derivatives. The utility and versatility of this method are showcased by the synthesis of 22 examples of tryptamines in ≤88% yield. In each case, indole formation is accompanied by in situ removal of the Boc protecting group.

2-Arylindoles: Concise Syntheses and a Privileged Scaffold for Fungicide Discovery

Indole is a popular and functional scaffold existing widely in the fields of medicine, pesticides, spices, food and feed additives, dyes, and many others. Among indoles, 2-arylindole represents a particular and interesting subset but has attracted less attention for drug discovery. In this study, we report a general, practical one-pot assembly of a variety of 2-arylindole derivatives. To develop novel fungicide scaffolds, their fungicide activity was also evaluated. The bioassay results showed that many of the synthesized 2-arylindoles exhibited considerable fungicidal activities especially toward Rhizoctonia cerealis, and several demonstrated an inhibition rate of more than 90%. Notably, 4-fluoro-2-phenyl-1H-indole 6e was obtained with a broad spectrum of fungicidal activities, which showed excellent growth inhibition activities against R. cerealis, Rhizoctonia solani, Botrytis cinerea, Magnaporthe oryza, and Sclerotinia sclerotiorum with EC₅₀ values of 2.31, 4.98, 6.78, 10.57, and 17.80 μg/mL, respectively. Preliminary fungicidal mode of action of 6e showed a significant inhibition effect on mycelial growth and spore germination. These results indicated that 2-arylindoles as privileged scaffolds exhibited potential fungicidal activities that deserve further study.

Synthesis of Densely Substituted Pyridine Derivatives from 1-Methyl-1,3-(ar)enynes and Nitriles by a Formal [4+2] Cycloaddition Reaction

An attractive method for assembling densely substituted pyridine derivatives from 1-methyl-1,3-(ar)enynes and nitriles via a formal [4+2] cycloaddition has been established. The well-balanced affinities of two alkali metal salts enable C(sp³)-H bond activation and excellent chemo- and regioselectivities. Experimental studies revealed that nitrile functions only as a partial nitrogen source for pyridine synthesis, and the addition of a metalated imine intermediate to an intramolecular alkyne is the rate-limiting step.

Iron–iodine co-catalysis towards tandem C–N/C–C bond formation: one-pot regioselective synthesis of 2-amino-3-alkylindoles

An efficient intermolecular C2,3-H aminoalkylation of indoles with 9H-xanthenes and azoles via iron–iodine co-catalyzed tandem C–N/C–C bond formation has been developed.

Alkali-Amide Controlled Selective Synthesis of 7-Azaindole and 7-Azaindoline through Domino Reactions of 2-Fluoro-3-methylpyridine and Aldehydes

Azaindoles and azaindolines are important core structures in pharmaceuticals and natural products, which have found wide applications in the field of medicinal chemistrty. In this study, we developed a novel...

Palladium-catalyzed nucleomethylation of alkynes for synthesis of methylated heteroaromatic compounds

Herein, we disclosed a novel and efficient palladium-catalyzed nucleomethylation of alkynes for the simultaneous construction of the heteroaromatic ring and methyl group. The 3-methylindoles, 3-methylbenzofurans and 4-methylisoquinolines were obtained in moderate to excellent yields. Notably, this methodology was employed as a key step for synthesis of a pregnane X receptor antagonist, zindoxifene, bazedoxifene and AFN-1252. The kinetic studies revealed that reductive elimination might be the rate-determining step.

A novel palladium-catalyzed nucleomethylation of alkynes is developed, affording 3-methylindoles, 3-methylbenzofurans and 4-methylisoquinolines in moderate to excellent yields.

Cobalt-catalyzed C(sp3)-H bond functionalization to access indole derivatives

Herein, we develop an efficient method of cobalt-catalyzed C(sp3)-H bond functionalization to synthesize indole derivatives. The highlight of this protocol is accomplished by the sequential C-H activation. This “cobalt/ organic...

Transition-metal-free hydroamination/defluorination/cyclization of perfluoroalkyl alkynes with amidines

An efficient defluorinative cyclization strategy for the construction of perfluoroalkyl-substituted pyrimidines by using perfluoroalkyl alkynes and amidines as substrates was developed.

Arylations with Nitroarenes for One-Pot Syntheses of Triaryl-methanols and Tetraarylmethanes

Triarylmethanols are well-known core structures in natural products and pharmacologically relevant compounds. In general, transition metal-based catalysts or highly reactive organometallics are employed for the synthesis of these compounds. Herein,...

Benzylic Aroylation of Toluenes Mediated by a LiN(SiMe3)2/Cs+ System

Chemoselective deprotonative functionalization of benzylic C-H bonds is challenging, because the arene ring contains multiple aromatic C(sp²)-H bonds, which can be competitively deprotonated and lead to selectivity issues. Recently it was found that bimetallic [MN(SiMe₃)₂ M = Li, Na]/Cs⁺ combinations exhibit excellent benzylic selectivity. Herein, is reported the first deprotonative addition of toluenes to Weinreb amides mediated by LiN(SiMe₃)₂/CsF for the synthesis of a diverse array of 2-arylacetophenones. Surprisingly, simple methyl benzoates also react with toluenes under similar conditions to form 2-arylacetophenones without double addition to give tertiary alcohol products. This finding greatly increases the practicality and impact of this chemistry. Some challenging substrates with respect to benzylic deprotonations, such as fluoro and methoxy substituted toluenes, are selectively transformed to 2-aryl acetophenones. The value of benzylic deprotonation of 3-fluorotoluene is demonstrated by the synthesis of a key intermediate in the preparation of Polmacoxib.

Selective Metalation and Functionalization of Fluorinated Nitriles Using 2,2,6,6-Tetramethylpiperidyl Bases

We have accomplished regioselective deprotometalation of aromatic and heteroaromatic nitriles via (TMP)₂Zn·2MgCl₂·2LiCl and TMPMgCl·LiCl (TMP = 2,2,6,6-tetramethylpiperidyl) with the exploration of new and scarcely investigated metalation positions. Regioselectivity was rationalized by DFT calculations. The quenching of the generated organozinc and organomagnesium intermediates with various electrophiles gave access to 47 highly functionalized nitriles with yields up to 95%. Additionally, we report a difunctionalization strategy and the use of functionalized nitriles as building blocks to construct relevant heterocycles.

One-Pot Synthesis of N-H-Free Pyrroles from Aldehydes and Alkynes

The first base-mediated intermolecular cyclization of arylaldehydes and terminal arylacetylenes for the synthesis of a wide range of pyrroles in a single step has been described. The developed methodology used commercially available starting materials and tolerated a broad range of functional groups affording 2,3,5-triaryl-substituted-1H-pyrroles with good yields (up to 92% yield) under mild conditions. The possible mechanism was also discussed.

Alkali-Metal Mediation: Diversity of Applications in Main-Group Organometallic Chemistry

Organolithium compounds have been at the forefront of synthetic chemistry for over a century, as they mediate the synthesis of myriads of compounds that are utilised worldwide in academic and industrial settings. For that reason, lithium has always been the most important alkali metal in organometallic chemistry. Today, that importance is being seriously challenged by sodium and potassium, as the alkali-metal mediation of organic reactions in general has started branching off in several new directions. Recent examples covering main-group homogeneous catalysis, stoichiometric organic synthesis, low-valent main-group metal chemistry, polymerization, and green chemistry are showcased in this Review. Since alkali-metal compounds are often not the end products of these applications, their roles are rarely given top billing. Thus, this Review has been written to alert the community to this rising unifying phenomenon of "alkali-metal mediation".

Palladium-Catalyzed Direct Arylation of 2-Pyridylmethyl Silanes with Aryl Bromides

The first palladium-catalyzed direct arylation of 2-pyridylmethyl silanes with aryl bromides to generate a diverse array of aryl(2-pyridyl)-methyl silane derivatives has been developed. This protocol facilitates access to various kinds of heterocycle-containing silanes in good to excellent yields (40 examples, 66-97% yield) with good functional group tolerance. The scalability of this transformation is demonstrated.

Transition-Metal-Free Synthesis of N-Arylphenothiazines through an N- and S-Arylation Sequence

An efficient synthetic method of N-arylphenothiazines from o-sulfanylanilines under transition-metal-free conditions is disclosed. An N- and S-arylation sequence of o-sulfanylanilines enabled us to synthesize a wide variety of N-arylphenothiazines. In particular, one-pot synthesis of N-arylphenothiazines was accomplished from easily available modules through preparation of o-sulfanylanilines by thioamination of aryne intermediates and following N- and S-arylation sequence.

Modular Counter-Fischer-Indole Synthesis through Radical-Enolate Coupling

A single-electron transfer mediated modular indole formation reaction from a 2-iodoaniline derivative and a ketone has been developed. This transition-metal-free reaction shows a broad substrate scope and unconventional regioselectivity trends. Moreover, important functional groups for further transformation are tolerated under the reaction conditions. Density functional theory studies reveal that the reaction proceeds by metal coordination, which converts a disfavored 5-endo-trig cyclization to an accessible 7-endo-trig process.

N-Acyl pyrroles: chemoselective pyrrole dance vs. C–H functionalization/aroylation of toluenes

Chemoselectivity is one of the most challenging issues facing the chemical sciences.