En Route to Intermolecular Cross-Dehydrogenative Coupling Reactions

Modifications of terpenoids via inert aliphatic C-H bond heteroarylation with heteroarenes

Here, we describe a method to modify commercially abundant terpenoids via inert aliphatic C-H bond heteroarylation directly with heteroarenes. The reaction is catalyzed by decatungstate anion under near-ultraviolet light irradiation. Furthermore, the inhibition effect of lipopolysaccharide (LPS)-induced nitric oxide (NO) production activity and cell proliferative inhibition in HUVEC and HCC1806 cells of the derivatives were evaluated. The heteroarylation could significantly result in changes in biological activity of terpenoids.

Photocatalytic Oxidative C(sp3)-H/N-H Cross-Dehydrogenative Coupling of Tertiary Anilines with Amides/Imides: Synthesis of N-Mannich Bases

A photocatalytic method for the synthesis of N-Mannich bases has been developed through the C(sp3)-H/N-H cross-dehydrogenative coupling of N,N-dimethylanilines with amides/imides. This process utilizes 2,4,6-triphenylpyrylium tetrafluoroborate (TPT) as the photocatalyst and is conducted at ambient temperature and atmospheric air. Various N,N-dimethylanilines and the aromatic, heteroaromatic and aliphatic (cyclic) amides, as well as imides were successfully employed, yielding moderate to good results. Preliminary mechanistic and isotope-labeling studies indicate that the reaction likely proceeds via a single electron transfer pathway and involves an α-aminoalkyl radical intermediate.

Cobalt catalysed cross-dehydrogenative coupling of indoles: a photoinduced ligand to metal charge transfer process

We demonstrate the participation of cobalt in a photoinduced ligand-to-metal charge transfer process, which leads to the formation of ligand-based radical species and enables both homo and hetero cross-dehydrogenative coupling of indoles with decent yield at room temperature. This photo-induced LMCT process is substantiated by a series of mechanistic investigations.

O2-Mediated Cu-Catalyzed Dehydrogenative Phenothiazination

In contrast to what one can be led to believe upon inspecting some of the recent literature, the dehydrogenative phenothiazination reaction does not require onerous technologies, complicated setups, or advanced catalysts in order to be mild and sustainable. We demonstrate this herein with a most facile, cost-effective, and sustainable Cu(II) catalyzed method, under 1 atm of O2 at room temperature in methanol, providing broad scope and high yields. These new results further set the dehydrogenative phenothiazination reaction among the green and practical coupling concepts of chemistry.

Regio- and Chemo-selective C-H Arylation of 3-Bromothiophene: A Synthesis Shortcut to Versatile π-Conjugated Building Blocks for Optoelectronic Materials

Unlike traditional multi-step synthetic approaches, we developed a single-step synthesis of versatile π-conjugated building blocks bearing post-functionalizable C-H and C-Br bonds. Direct C-H arylation of 3-bromothiophene with various iodo(hetero)aryls was successfully carried out with good regio- and chemo-selectivity. Under optimized reaction conditions, 20 new compounds were facilely prepared in yields up to 91 %. One of the obtained compounds was demonstrated to further extend its conjugation length using a succinct synthetic plan to create two symmetrical oligo(hetero)aryls (MLC01 and MLC02) that were fabricated as effective hole-transporting materials (HTM) for perovskite solar cells (PSC). PSC devices utilizing MLC01 as hole-transport layer displayed promising power conversion efficiencies of up to 17.01 %.

Iron-Catalyzed Cross-Dehydrogenative Coupling

This review highlights significant advances in iron-catalyzed cross-dehydrogenative coupling (CDC), a method pivotal for forming carbon-carbon (C-C) bonds directly from C-H bonds. This technique uses iron-a naturally abundant, inexpensive, and environmentally benign transition metal-as a catalyst to facilitate the coupling of two unfunctionalized C-H bonds. This method stands out for avoiding pre-functionalized substrates, reducing both waste and cost in organic synthesis. The discussion includes a variety of CDC methodologies involving combinations of C(sp3)-H with C(sp3)-H, C(sp3)-H with C(sp2)-H, and C(sp3)-H with C(sp)-H bonds. These methods have been successfully applied in synthesizing complex molecules and pharmaceuticals, highlighting the versatility and efficiency of iron catalysis.

Electrochemical α-C(sp3)-H/N-H Cross-Coupling of Isochromans and Azoles

Isochroman and azole moieties are both present in a wide variety of biologically active molecules. Their efficient combination under mild reaction conditions is beneficial for obtaining small-molecule drug candidates. In this paper, we describe electrochemical α-C(sp3)-H/N-H cross-coupling reactions between isochromans and azoles, yielding products in moderate to excellent yields. This protocol does not require any catalysts or exogenous oxidants and can be performed at room temperature under air. Control experiments and cyclic voltammetry showed that the reaction may proceed through both radical coupling and nucleophilic addition processes.

Synthesis of ω-functionalized ketones from strained cyclic alcohols by ring-opening and cross-recombination between alkyl and N-oxyl radicals

Radical ring-opening oxyimidation of cyclobutanols and cyclopropanols with the formation of ω-functionalized ketones was discovered. The oxidative C-O coupling proceeds via the interception of a primary alkyl radical generated from a cyclic alcohol with a reactive radical generated in situ, which is an electron-deficient N-oxyl radical. The developed conditions allow for the balanced generation rates of carbon- and N-oxyl radicals, which are necessary for their selective cross-recombination. Thus, typical competitive dimerization processes of carbon-centered radicals, their intermolecular cyclization, and N-oxyl radical self-decay are suppressed. The method is applicable to a wide range of cyclobutanols and results in oxyimidated ketones in yields of up to 82%.

Synthesis of N-heterocyclic compounds using N,N-dimethylacetamides as an electrophilic carbon source

In this study, N-heterocyclic compounds were synthesized using nitrogen-containing nucleophilic substrates and electrophilic carbon sources derived from N,N-dimethylacetamide (DMAc). Depending on the nucleophilic groups, N-heterocyclic compounds such as 4-quinazolinones, pyrrole-quinoxalines, and dihydro-benzothiadiazine dioxides were produced. Carbon, adjacent to the nitrogen in DMAc, was activated in the presence of FeCl3·6H2O and di-t-butyl peroxide (DTBP). This procedure was considered an economical synthetic method because it utilized iron catalysts and DMAc as an electrophilic carbon source and a solvent.

Photoinduced HCl-Mediated Cross-Dehydrogenative Coupling of Quinolines with Alcohols and Ethers

Via light irradiation, cross-dehydrogenative coupling of quinolines with alcohols and ethers was achieved under mild conditions. A stoichiometric amount of HCl and room temperature were necessary to promote the reaction. A green Minisci-type cross-dehydrogenative coupling reaction was performed without an oxidant or a transition-metal catalyst.

N-Heterocyclic Carbene Enabled Functionalization of Inert C(Sp3)-H Bonds via Hydrogen Atom Transfer (HAT) Processes

Developing methods to directly transform C(sp3) -H bonds is crucial in synthetic chemistry due to their prevalence in various organic compounds. While conventional protocols have largely relied on transition metal catalysis, recent advancements in organocatalysis, particularly with radical NHC catalysis have sparked interest in the direct functionalization of "inert" C(sp3) -H bonds for cross C-C coupling with carbonyl moieties. This strategy involves selective cleavage of C(sp3) -H bonds to generate key carbon radicals, often achieved via hydrogen atom transfer (HAT) processes. By leveraging the bond dissociation energy (BDE) and polarity effects, HAT enables the rapid functionalization of diverse C(sp3)-H substrates, such as ethers, amines, and alkanes. This mini-review summarizes the progress in carbene organocatalytic functionalization of inert C(sp3)-H bonds enabled by HAT processes, categorizing them into two sections: 1) C-H functionalization involving acyl azolium intermediates; and 2) functionalization of C-H bonds via reductive Breslow intermediates.

Metal free cross-dehydrogenative N-N coupling of primary amides with Lewis basic amines

Hydrazides, N-N containing structural motifs, are important due to their presence in a wide variety of biologically significant compounds. While the homo N-N coupling of two NH moieties to form the hydrazide N-N bond is well developed, the cross-dehydrogenative hetero N-N coupling remains very unevolved. Here we present an efficient intermolecular N-N cross-coupling of a series of primary benzamides with broad range of Lewis basic primary and secondary amines using PhI(OAc)2 as both a terminal oxidant and a cross-coupling mediator, without the need for metal catalysts, high temperatures, and inert atmospheres, and with substantial potential for use in the late-stage functionalization of drugs.

CBr4 as a Mild Oxidant-Enabled Oxidation of a sp3 C-H Bond: A Facile Synthesis of the Persistent Iminium Salts of Tetrahydroisoquinolines

Using CBr4 as a mild oxidant, the direct C-H bond oxidation of N-aryltetrahydroisoquinolines was achieved, giving a series of the corresponding iminium salts in high yields under metal- and photo-free reaction conditions. This reaction is superior in high yields and good functional group tolerance, and the late-stage derivatization showed that these iminium salts can readily be applied to the synthesis of the functionalized THIQs.

Hole-Transporting Materials based on Oligo(hetero)aryls with a Naphthodithiophene Core - Succinct Synthesis by Twofold Direct C-H Olefination

This work demonstrated the first synthetic application of direct C-H olefinations in the step-saving preparation of various hole-transporting materials (HTM) for efficient perovskite solar cells (PSC). Cross-dehydrogenative couplings of naphthodithiophene (NDT) with vinyl arenes under palladium-catalysis facilely generated various new oligo(hetero)aryls with internal alkenes. Reaction conditions were optimized, which gave the product isolated yields of up to 71 % with high (E)-stereoselectivity. These readily accessible NDT core-based small molecules involving olefin as π-spacers displayed immediate power conversion efficiencies of up to 17.2 % without a device oxidation process that is required for the commercially available spiro-OMeTAD and most other existing HTMs while fabricated in corresponding PSC devices.

Direct Formation of C-C, C-N, and C-O Bonds in Dihydroquinazolines via Hypervalent Iodine(III)-Mediated sp3 C-H Functionalization

A hypervalent iodine(III)-mediated cross-dehydrogenative coupling reaction for the direct formation of C-C, C-N, and C-O bonds in dihydroquinazolines has been developed. This one-pot method allows for the synthesis of C4-disubstituted dihydroquinazolines as well as C4-spirolactam, spirolactone, and spiroindene dihydroquinazolines in moderate to high yields.

Photopromoted Free Radical Silylation of 2-Aryl-2H-indazoles with Silanes

Photoinduced silylation of silanes with 2-aryl-2H-indazoles was developed under mild conditions, which could efficiently result in diverse 3-silylated 2H-indazoles with good substrate scopes. A series of scaled-up to gram level and radical capture operations were performed in this system. Meanwhile, a bioactive molecule was tolerated well under typical conditions.

Enaminone-directed ruthenium(II)-catalyzed C-H activation and annulation of arenes with diazonaphthoquinones for polycyclic benzocoumarins

The weakly coordinating enaminone functionality has been leveraged for a C-H bond activation strategy under ruthenium catalysis and employed in the regioselective annulative coupling of arenes with diazonaphthoquinones, offering polycyclic benzocoumarins in very high yields. The enaminone motif plays a dual role and the protocol operates through a Ru(II)/Ru(IV) catalytic pathway which is amenable to the diversification of various pharmacophore-coupled substrates.

Organic photoredox catalyzed C(sp3)-H functionalization of saturated aza-heterocycles via a cross-dehydrogenative coupling reaction

Herein we present a novel protocol to access α-functionalized saturated aza-heterocycles, and a variety of nucleophilic groups, such as indole, naphthol, phenol, pyrrole, furyl, nitromethyl, and cyano, could be easily installed into saturated aza-heterocycles. Furthermore, a range of biologically valuable 3,3'-diindolylmethane derivatives could also be readily accessed under mild photocatalytic conditions.

Non-noble metal-catalyzed cross-dehydrogenation coupling (CDC) involving ether α-C(sp3)-H to construct C-C bonds

Ether derivatives are widespread as essential building blocks in various drugs, natural products, agrochemicals, and materials. Modern economy requires developing green strategies with improved efficiency and reduction of waste. Due to its atom and step-economy, the cross-dehydrogenative coupling (CDC) reaction has become a major strategy for ether functionalization. This review covers C-H/C-H cross-coupling reactions of ether derivatives with various C-H bond substrates via non-noble metal catalysts (Fe, Cu, Co, Mn, Ni, Zn, Y, Sc, In, Ag). We discuss advances achieved in these CDC reactions and hope to attract interest in developing novel methodologies in this field of organic chemistry.

Acceptorless cross-dehydrogenative coupling for C(sp3)-H heteroarylation mediated by a heterogeneous GaN/ketone photocatalyst/photosensitizer system

Alkanes are naturally abundant chemical building blocks that contain plentiful C(sp3)-H bonds. While inert, the activation of C(sp3)-H via hydrogen atom abstraction (HAT) stages an appealing approach to generate alkyl radicals. However, prevailing shortcomings include the excessive use of oxidants and alkanes that impede scope. We herein show the use of gallium nitride (GaN) as a non-toxic, recyclable, heterogeneous photocatalyst to enable alkyl C(sp3)-H in conjunction with the catalytic use of simple photosensitizer, benzophenone, to promote the desired alkyl radical generation. The dual photocatalytic cycle enables cross-dehydrogenative Minisci alkylation under mild and chemical oxidant-free conditions.

Photocatalytic Late-Stage C-H Functionalization

The emergence of modern photocatalysis, characterized by mildness and selectivity, has significantly spurred innovative late-stage C-H functionalization approaches that make use of low energy photons as a controllable energy source. Compared to traditional late-stage functionalization strategies, photocatalysis paves the way toward complementary and/or previously unattainable regio- and chemoselectivities. Merging the compelling benefits of photocatalysis with the late-stage functionalization workflow offers a potentially unmatched arsenal to tackle drug development campaigns and beyond. This Review highlights the photocatalytic late-stage C-H functionalization strategies of small-molecule drugs, agrochemicals, and natural products, classified according to the targeted C-H bond and the newly formed one. Emphasis is devoted to identifying, describing, and comparing the main mechanistic scenarios. The Review draws a critical comparison between established ionic chemistry and photocatalyzed radical-based manifolds. The Review aims to establish the current state-of-the-art and illustrate the key unsolved challenges to be addressed in the future. The authors aim to introduce the general readership to the main approaches toward photocatalytic late-stage C-H functionalization, and specialist practitioners to the critical evaluation of the current methodologies, potential for improvement, and future uncharted directions.

Transition metal-catalyzed double Cvinyl-H bond activation: synthesis of conjugated dienes

Conjugated dienes have occupied a pivotal position in the field of synthetic organic chemistry and medicinal chemistry. They act as important synthons for the synthesis of various biologically important molecules and therefore, gain tremendous attention worldwide. A wide range of synthetic routes to access these versatile molecules have been developed in the past decades. Transition metal-catalyzed cross-dehydrogenative coupling (CDC) has emerged as one of the utmost front-line research areas in current synthetic organic chemistry due to its high atom economy, efficiency, and viability. In this review, an up-to-date summary including scope, limitations, mechanistic studies, stereoselectivities, and synthetic applications of transition metal-catalyzed double C_vinyl-H bond activation for the synthesis of conjugated dienes has been reported since 2013. The literature reports mentioned in this review have been classified into three different categories, i.e. (a) C_vinyl-C_vinyl bond formation via oxidative homo-coupling of terminal alkenes; (b) C_vinyl-C_vinyl bond formation via non-directed oxidative cross-coupling of linear/cyclic alkenes and terminal/internal alkenes, and (c) C_vinyl-C_vinyl bond formation via oxidative cross-coupling of directing group bearing alkenes and terminal/internal alkenes. Overall, this review aims to provide a concise overview of the current status of the considerable development in this field and is expected to stimulate further innovation and research in the future.

MnO2-Mediated Oxidative Cyclization of "Formal" Schiff's Bases: Easy Access to Diverse Naphthofuro-Annulated Triazines

A different type of MnO₂-induced oxidative cyclization of dihydrotriazines has been developed. These dihydrotriazines are considered as a "formal" Schiff's base. This method provided easy access to naphthofuro-fused triazine via the C-C/C-O oxidative coupling reaction. The reaction sequence comprised the nucleophilic addition of 2-naphthol or phenol to 1,2,4-triazine, followed by oxidative cyclization. The scope and limitations of this novel coupling reaction have been investigated. Further application of the synthesized compound has been demonstrated by synthesizing carbazole-substituted benzofuro-fused triazines. The scalability of the reaction was demonstrated at a 40 mmol load. The mechanistic study strongly suggests that this reaction proceeds through the formation of an O-coordinated manganese complex.

Pd-catalyzed Aerobic Cross-Dehydrogenative Coupling of Catechols with 2-Oxindoles and Benzofuranones: Reactivity Difference Between Monomer and Dimer

Persistent radicals, which are generated from 2-oxindole or benzofuranone dimers, are useful tools for designing the radical-based cross-coupling reaction to provide molecules containing a quaternary carbon. The persistent radical is accessible from both the dimer and monomer; however, the reactivity difference between these substrates for the oxidative cross-coupling reaction is not fully understood, most likely because of the mechanistic complexity. Here, we present details of an aerobic cross-dehydrogenative coupling (CDC) reaction using various monomers and catechols. UV-Vis analysis and mechanistic control experiments showed that the monomer is less reactive than the dimer under aerobic conditions. Our Pd(II)-BINAP-μ-hydroxo complex significantly improved the reactivity of the monomers for the aerobic CDC reaction with catechols, yielding results comparable to those of the corresponding dimer. The procedure, which enables the generation of the persistent radical in situ, is particularly useful when employing the monomer that is not readily converted to the corresponding dimer.

Photochemistry Journey to Multielectron and Multiproton Chemical Transformation

The odyssey of photochemistry is accompanied by the journey to manipulate "electrons" and "protons" in time, in space, and in energy. Over the past decades, single-electron (1e^-) photochemical transformations have brought marvelous achievements. However, as each photon absorption typically generates only one exciton pair, it is exponentially challenging to accomplish multielectron and proton photochemical transformations. The multistep differences in thermodynamics and kinetics urgently require us to optimize light harvesting, expedite consecutive electron transfer, manipulate the interaction of catalysts with substrates, and coordinate proton transfer kinetics to furnish selective bond formations. Tandem catalysis enables orchestrating different photochemical events and catalytic transformations from subpicoseconds to seconds, which facilitates multielectron redox chemistries and brings consecutive, value-added reactivities. Joint efforts in molecular and material design, mechanistic understanding, and theoretical modeling will bring multielectron and proton synthetic opportunities for fuels, fertilizers, and chemicals with enhanced versatility, efficiency, selectivity, and scalability, thus taking better advantage of photons (i.e., sunlight) for our sustainable society.

Chemodivergent Synthesis of Indeno[1,2-b]indoles and Isoindolo[2,1-a]indoles via Mn(III)-Mediated or Electrochemical Intramolecular Radical Cross-Dehydrogenative Coupling

Chemodivergent synthesis of indeno[1,2-b]indoles and isoindolo[2,1-a]indoles from the same starting materials involving radical cross-dehydrogenative couplings have been developed. Mn(OAc)₃·2H₂O selectively promoted an intramolecular radical C-H/C-H dehydrogenative coupling reaction to provide indeno[1,2-b]indoles, while an intramolecular radical C-H/N-H dehydrogenative coupling reaction could proceed via electrochemistry to deliver isoindolo[2,1-a]indoles. Plausible mechanisms of the chemodivergent reactions were proposed.

Photocatalytic Aerobic Coupling of Azaarenes and Alkanes via Nontraditional Cl• Generation

Herein, we demonstrate a nonconventional photocatalytic generation of Cl^• from a common chlorinated solvent, dichloroethane, under aerobic conditions and its successful utilization toward the cross-dehydrogenative coupling of alkanes and azaarenes via hydrogen atom transfer with Cl^•. The process is free from chloride salt, toxic oxidant, and UV light. It is applicable to a broad spectrum of substrates. The proposed mechanism involving Cl^• is supported by a series of mechanistic investigations.

Visible-Light-Promoted Cross Dehydrogenative/Decarboxylative Coupling Cascades of Glycine Ester Derivatives and β-Keto Acids

A visible-light-induced dehydrogenative/decarboxylative coupling reaction of arylglycine derivatives and β-keto acids is described. This photocatalyst- and additive-free protocol can be applied in the efficient synthesis of γ-keto glycine derivatives under ambient conditions. Further uses of this methodology and a plausible mechanism are also demonstrated.

O2-Mediated Te(II)-Redox Catalysis for the Cross-Dehydrogenative Coupling of Indoles

Very few elements in the periodic system can catalytically activate O₂, such as in the context of cross-dehydrogenative couplings. The development of O₂-activating catalysts is essential to enable new and sustainable reactivity concepts to emerge, because these catalysts also often feature specific activating interactions with the target substrates. In this context, the unprecedented Te(II)/Te(III) catalyzed dehydrogenative C3-C2 dimerization of indoles is described herein. The fact that O₂ can be directly utilized as a terminal oxidant in this reaction, as well as the absence of any background reactivity without the redox-active Te catalyst, constitute very important milestones for the fields of cross-dehydrogenative couplings and tellurium catalysis.

TEMPO-Promoted Mono- and Bisimidation of Tertiary Anilines: Synthesis of Symmetric and Unsymmetric N-Mannich Bases

A TEMPO-promoted method was developed for the synthesis of symmetric bis-N-Mannich bases via sequential activation of two α,α'-amino C(sp³)-H bonds of N,N-dimethylanilines under mild conditions. This methodology was further extended for monoimidation of α-amino-functionalized methylanilines to give unsymmetric N-Mannich bases in good to high yields. Several control experiments were performed, and the coupling reaction outcomes indicated that the oxoammonium (TEMPO⁺) species is involved in the reaction.

Visible-light-induced cross-coupling of aryl iodides with hydrazones via an EDA-complex

A visible-light-induced, transition-metal and photosensitizer-free cross-coupling of aryl iodides with hydrazones was developed. In this strategy, hydrazones were used as alternatives to organometallic reagents, in the absence of a transition metal or an external photosensitizer, making this cross-coupling mild and green. The protocol was compatible with a variety of functionalities, including methyl, methoxy, trifluoromethyl, halogen, and heteroaromatic rings. Mechanistic investigations showed that the association of the hydrazone anion with aryl halides formed an electron donor–acceptor complex, which when excited with visible light generated an aryl radical via single-electron transfer.

Visible-light-induced catalyst-free cross-coupling of aryl iodides with hydrazones via single-electron-transfer was reported. The mechanistic investigations showed that the association of hydrazone anion with aryl iodides formed an EDA complex.

Hydrogen Atom Transfer Driven Enantioselective Minisci Reaction of Alcohols

Catalytic enantioselective Minisci reactions have recently been developed but all instances so far utilize α-amino radical coupling partners. We report a substantial evolution of the enantioselective Minisci reaction that enables α-hydroxy radicals to be used, providing valuable enantioenriched secondary alcohol products. This is achieved through the direct oxidative coupling of two C-H bonds on simple alcohol and pyridine partners through a hydrogen atom transfer (HAT)-driven approach: a challenging process to achieve due to the numerous side reactions that can occur. Our approach is highly regioselective as well as highly enantioselective. Dicumyl peroxide, upon irradiation with 390 nm light, serves as both HAT reagent and oxidant whilst selectivity is controlled by use of a chiral phosphoric acid catalyst. Computational and experimental evidence provide mechanistic insight as to the origin of selectivity, revealing a stereodetermining deprotonation step distinct from the analogous reaction of amide-containing substrates.

Nickel-Catalyzed Thermal Redox Functionalization of C(sp3 )-H Bonds with Carbon Electrophiles

C(sp³ )-H bond coupling with carbon electrophiles remains rarely explored under thermo-driven hydrogen atom transfer (HAT) conditions due to the challenge of integrating oxidation and reduction in a single operation. We report here a Ni-catalyzed arylation and alkylation of C(sp³ )-H bonds with organohalides to forge C(sp³ )-C bonds by merging economical Zn and tBuOOtBu (DTBP) as the external reductant and oxidant. The mild and easy-to-operate protocol enables facile carbofunctionalization of N-/O-α- and cyclohexane C-H bonds, and preparation of a few intermediates of bioactive compounds and drug derivatives. Preliminary mechanistic studies implied addition of an alkyl radical to a Ni^II salt.

Photocatalytic C(sp3) radical generation via C-H, C-C, and C-X bond cleavage

C(sp³) radicals (R˙) are of broad research interest and synthetic utility. This review collects some of the most recent advancements in photocatalytic R˙ generation and highlights representative examples in this field. Based on the key bond cleavages that generate R˙, these contributions are divided into C–H, C–C, and C–X bond cleavages. A general mechanistic scenario and key R˙-forming steps are presented and discussed in each section.

C(sp³) radicals (R˙) are of broad research interest and synthetic utility.

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

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

Copper-Catalyzed Phosphorylation of N,N-Disubstituted Hydrazines: Synthesis of Multisubstituted Phosphorylhydrazides as Potential Anticancer Agents

An efficient copper-catalyzed aerobic oxidative cross-dehydrogenative coupling reaction for the synthesis of multisubstituted phosphorylhydrazides from N,N-disubstituted hydrazines and hydrogen phosphoryl compounds is accomplished. The reaction proceeds under mild conditions without the addition of any external oxidants and bases. This work reported here represents a direct P(═O)-N-N bond formation with the advantages of being operationally simple, good functional group tolerance, and high atom and step economy. Furthermore, the selected compounds exhibit potential inhibitory activity against tumor cells, which can be used in the field of screening of anticancer agents as new chemical entities.

Photochemical α-Aminonitrile Synthesis Using Zn-Phthalocyanines as Near-Infrared Photocatalysts

While photochemical transformations with sunlight almost exclusively utilize the UV-vis part of the solar spectrum, the majority of the photons emitted by the sun have frequencies in the near-infrared region. Phthalocyanines show high structural similarity to the naturally occurring light-harvesting porphyrins, chlorins, and mainly bacteriochlorins and are also known for being efficient and affordable near-infrared light absorbers as well as triplet sensitizers for the production of singlet oxygen. Although having been neglected for a long time in synthetic organic chemistry due to their low solubility and high tendency toward aggregation, their unique photophysical properties and chemical robustness make phthalocyanines attractive photocatalysts for the application in near-infrared-light-driven synthesis strategies. Herein, we report a cheap, simple, and efficient photocatalytic protocol, which is easily scalable under continuous-flow conditions. Various phthalocyanines were studied as near-infrared photosensitizers in oxidative cyanations of tertiary amines to generate α-aminonitriles, a synthetically versatile compound class.

Solvent- and additive-free oxidative amidation of aldehydes using a recyclable oxoammonium salt

A range of acyl azoles have been prepared from aromatic, heteroaromatic, and aliphatic aldehydes by means of an oxidative amidation reaction. The methodology employs a substoichiometric quantity of an oxoammonium salt as the oxidant. It avoids the need for additives such as a base, is run solvent-free, and the oxoammonium salt is recyclable.