Visible‐Light Promoted Catalyst‐Free Imidation of Arenes and Heteroarenes

We described herein a catalyst‐free visible‐light photolytic protocol for the imidation of arenes and heteroarenes. N‐Bromosaccharin was identified as a viable and chemoselective nitrogen radical precursor that undergoes controllable homolytic cleavage under ambient light irradiation. The reaction can be applied to a number of arenes and heteroarenes with good chemo‐ and regioselectivity. Mechanistic studies revealed that radical chain termination by electron transfer‐proton transfer (ET‐PT) is the leading productive pathway for the reaction.     

Birch‐Type Photoreduction of Arenes and Heteroarenes by Sensitized Electron Transfer

The direct reduction of arenes and heteroarenes by visible‐light irradiation remains challenging, as the energy of a single photon is not sufficient for breaking aromatic stabilization. Shown herein is that the energy accumulation of two visible‐light photons allows the dearomatization of arenes and heteroarenes. Mechanistic investigations confirm that the combination of energy‐transfer and electron‐transfer processes generates an arene radical anion, which is subsequently trapped by hydrogen‐atom transfer and finally protonated to form the dearomatized product. The photoreduction converts planar aromatic feedstock compounds into molecular skeletons that are of use in organic synthesis.     

Sodiation of Arenes and Heteroarenes in Continuous Flow

The first sodiations of (hetero)arenes in continuous flow using NaDA (sodium diisopropylamide) in Me₂EtN are reported. This flow procedure enables sodiation of functionalized arenes and heteroarenes that decompose under batch‐sodiation conditions. The resulting sodiated (hetero)arenes react instantly with various electrophiles, such as ketones, aldehydes, isocyanates, alkyl bromides, and disulfides, affording polyfunctionalized (hetero)arenes in high yields. Scale‐up is possible without further optimization.     

Iron‐Catalyzed Aminative Cyclization/Intermolecular Homolytic Aromatic Substitution Using Oxime Esters and Simple Arenes

Intermolecular C?H alkylation of simple arenes in the presence of an iron catalyst has been achieved in a cascade manner with an aminative cyclization triggered by N?O bond cleavage of an alkene‐tethered oxime ester. Various arenes, including electron‐rich and electron‐poor arenes, and heteroarenes can be employed in the reaction system. Regioselectivity and radical trapping experiments support the involvement of alkyl radical species, which undergo a homolytic aromatic substitution (HAS) to afford the arylation products.     

A Remote ‘Imidazole’‐Based Ruthenium(II) Para‐Cymene Pre‐catalyst for the Selective Oxidation Reaction of Alkyl Arenes and Alcohols

Herein we disclosed the use of a remote ‘imidazole’‐based precatalyst [(para‐cymene)Ru^II(L)Cl]⁺, C‐1 where L=2‐(4‐substituted‐phenyl)‐1H‐imidazo[4,5‐f]^[1,10] phenanthroline) for the selective oxidation of a variety of alkyl arenes/heteroarenes and alcohols to their corresponding aldehydes or ketones in presence of tert‐butyl hydroperoxide (TBHP). The remote ‘imidazole’ moiety present in the complex facilitates the activation of oxidant and subsequent generation of active species via the release of para‐cymene from C‐1 , which in‐turn was less effective without the ‘imidazole’ moiety. The mechanistic features of C‐1 promoted oxidation of alkyl arenes were also assessed from spectroscopic, kinetic, and few control experiments. The substrate scope for C‐1 promoted oxidation reaction was assessed based on the selective oxidation of 27‐different alkyl arenes/heteroarenes and 25 different alcohols to their corresponding aldehydes/ketones in moderate to good yields.     

Ladder‐type Heteroarenes: Up to 15 Rings with Five Imide Groups

A series of novel imide‐functionalized ladder‐type heteroarenes with well‐defined structure and controllable conjugation lengths were synthesized and characterized. The synthetic route shows remarkable efficacy for constructing the electron‐deficient ladder backbones. π‐Conjugation extension leads to narrowed band gaps with enhanced electron affinities. The ladder arenes are incorporated into organic thin‐film transistors, and show encouraging electron mobilities of 0.013–0.045 cm² V⁻¹ s⁻¹. The heteroarenes reported here provide a remarkable platform for fundamental physicochemical studies and materials innovation in organic electronics.     

Silver‐Catalyzed Arylation of (Hetero)arenes by Oxidative Decarboxylation of Aromatic Carboxylic Acids

A long‐standing challenge in Minisci reactions is achieving the arylation of heteroarenes by oxidative decarboxylation of aromatic carboxylic acids. To address this challenge, the silver‐catalyzed intermolecular Minisci reaction of aromatic carboxylic acids was developed. With an inexpensive silver salt as a catalyst, this new reaction enables a variety of aromatic carboxylic acids to undergo decarboxylative coupling with electron‐deficient arenes or heteroarenes regardless of the position of the substituents on the aromatic carboxylic acid, thus eliminating the need for ortho‐substituted aromatic carboxylic acids, which were a limitation of previously reported methods.     

Cobalt‐Catalyzed C?H Bond Functionalizations with Aryl and Alkyl Chlorides

Inexpensive cobalt catalysts derived from N‐heterocylic carbenes (NHC) allowed efficient catalytic C? H bond arylations on heteroaryl‐substituted arenes with widely available aryl chlorides, which set the stage for the preparation of sterically hindered tri‐ortho‐substituted biaryls. Likewise, challenging direct alkylations with β‐hydrogen‐containing primary and even secondary alkyl chlorides proceeded on pyridyl‐ and pyrimidyl‐substituted arenes and heteroarenes. The cobalt‐catalyzed C? H bond functionalizations occurred efficiently at ambient reaction temperature with excellent levels of site‐selectivities and ample scope. Mechanistic studies highlighted that electron‐deficient aryl chlorides reacted preferentially, while the arenes kinetic C? H bond acidity was found to largely govern their reactivity.     

Cu‐Mediated Amination of (Hetero)Aryl C−H bonds with NH Azaheterocycles

Direct synthesis of N‐(hetero)arylated heteroarenes has been realized through Cu‐mediated C?N coupling of NH azaheterocycles with aryl C?H bonds under aerobic conditions. This method features a broad scope of both heterocyclic arenes (pyridine, quinoline, pyrazole, imidazole, furan, thiophene, benzofuran, and indole) and NH azaheterocycles (imidazole, pyrazole, indole, azindole, purine, indazole, benzimidazole, pyridone, carbazole), providing a versatile method for the synthesis of pharmaceutically important N‐(hetero)arylated heteroarenes. The versatility of this reaction was further demonstrated through late‐stage modification of marketed drugs and the synthesis of a key intermediate for accessing a class of angiotensin II receptor 1 antagonists.     

Copper‐Catalyzed Electrophilic Amination of Heteroarenes and Arenes by C?H Zincation

Direct amination of heteroarenes and arenes has been achieved in a one‐pot C H zincation/copper‐catalyzed electrophilic amination procedure. This amination method provides an efficient and rapid approach to access a diverse range of heteroaromatic and aromatic amines including those previously inaccessible using C H amination methods. The mild reaction conditions and good functional‐group compatibility demonstrate its great potential for the synthesis of important and complex amines.     

Copper‐Catalyzed Electrophilic Amination of Heteroarenes and Arenes by CH Zincation

Direct amination of heteroarenes and arenes has been achieved in a one‐pot C? H zincation/copper‐catalyzed electrophilic amination procedure. This amination method provides an efficient and rapid approach to access a diverse range of heteroaromatic and aromatic amines including those previously inaccessible using C? H amination methods. The mild reaction conditions and good functional‐group compatibility demonstrate its great potential for the synthesis of important and complex amines.     

Highly efficient gold(III)-catalyzed intermolecular hydroarylation of unactivated alkenes with arenes under mild conditions

A simple and efficient method for functionalization of electron-rich arenes and heteroarenes with unactivated alkenes by Au(III)-catalyzed intermolecular hydroarylation under mild reaction conditions was developed. This method features a short reaction time (5 h) under mild conditions and has a broad substrate scope, including electron-rich arenes and heteroarenes, terminal and internal substituted aryl alkenes, and unactivated aliphatic alkenes.     

Photoarylation of Iodocarboranes with Unactivated (Hetero)Arenes: Facile Synthesis of 1,2‐[(Hetero)Aryl]n‐o‐Carboranes (n=1,2) and o‐Carborane‐Fused Cyclics

Photoarylation of iodocarboranes with unactivated arenes/heteroarenes at room temperature has been achieved, for the first time, thus leading to the facile synthesis of a large variety of cage carbon mono(hetero)arylated and di(hetero)arylated o‐carboranes. This work represents a clean, efficient, transition‐metal‐free, and cheap synthesis of functionalized carboranes, which has significant advantages over the known methods.     

Functionalization of Organic Molecules by Transition‐Metal‐Catalyzed C(sp3)?H Activation

Transition‐metal‐catalyzed C? H activation has recently emerged as a powerful tool for the functionalization of organic molecules. While many efforts have focused on the functionalization of arenes and heteroarenes by this strategy in the past two decades, much less research has been devoted to the activation of non‐acidic C? H bonds of alkyl groups. This Minireview highlights recent work in this area, with a particular emphasis on synthetically useful methods.     

Expedient Iron‐Catalyzed C−H Allylation/Alkylation by Triazole Assistance with Ample Scope

Triazole assistance set the stage for a unified strategy for the iron‐catalyzed C?H allylation of arenes, heteroarenes, and alkenes with ample scope. The versatile catalyst also proved competent for site‐selective methylation, benzylation, and alkylation with challenging primary and secondary halides. Triazole‐assisted C?H activation proceeded chemo‐, site‐, and diastereo‐selectively, and the modular TAM directing group was readily removed in a traceless fashion under exceedingly mild reaction conditions.     

Direct C-H arylation of (hetero)arenes with aryl iodides via rhodium catalysis

A new method for the catalytic C-H arylation of heteroarenes and arenes that manifests high activity paired with reasonably broad scope was developed. Under the catalytic influence of RhCl(CO){P[OCH(CF3)2]3}2 and Ag2CO3, the direct C-H arylation of heteroarenes/arenes with aryl/heteroaryl iodides took place to afford a range of biaryls in good to excellent yields with high regioselectivity. Thiophenes, furans, pyrroles, indoles, and alkoxybenzenes are applicable in this arylation protocol.     

Accessing Difluoromethylated and Trifluoromethylated cis‐Cycloalkanes and Saturated Heterocycles: Preferential Hydrogen Addition to the Substitution Sites for Dearomatization

Reported here is a straightforward process in which a cyclic (alkyl)(amino)carbene/Rh catalyst system facilitates the preferential addition of hydrogen to the substitution sites of difluoromethylated and trifluoromethylated arenes and heteroarenes, leading to dearomative reduction. This strategy enables the diastereoselective synthesis of cis‐difluoromethylated and cis‐trifluoromethylated cycloalkanes and saturated heterocycles, and even allows formation of all‐cis multi‐trifluoromethylated cyclic products with a defined equatorial orientation of the di‐ and trifluoromethyl groups. Deuterium‐labeling studies indicate that hydrogen preferentially attacks the substitution sites of planar arenes, resulting in dearomatization, possibly with heterogeneous Rh as the reactive species, followed by either reversible or irreversible hydrogen addition to the nonsubstitution sites.     

Acylation of (Hetero)Arenes through CH Activation with Aroyl Surrogates

In this Minireview, the major achievements in the acylation of arenes and heteroarenes by C?H activation with aroyl groups are summarized and discussed. As the products are carbonyl‐containing compounds that are typical products from carbonylation chemistry, the possible inspirations for these reactions are also discussed, as are mechanistic issues and possible problems for carbonylative diaryl ketone synthesis by C?H activation.     

Merging Photocatalysis with Electrochemistry: The Dawn of a new Alliance in Organic Synthesis

The merging of a homogeneous photocatalytic system with an electrochemical cell, having exchanged electrons as the only common point, has been recently demonstrated. This combination opens unexplored pathways in synthesis and allowed net‐oxidative photocatalytic processes to be realized in the absence of a chemical oxidant, including: 1) the C?H alkylation of heteroarenes and 2) the coupling of azoles with arenes in the presence of an electrogenerated photocatalyst.     

Lewis Acid–Mediated Domino Reaction of 3-Bromomethylthiophenes with Arenes/Heteroarenes

Lewis acid–mediated domino reaction of 3-bromomethylthiophenes with various types of arenes and heteroarenes is reported.