Direct Arylation Research Articles

Electrochromic conjugated polymers: The relationship of gradient band gap and electrochromic performance

In the pursuit of high-performance electrochromic materials, in this paper, six donor-acceptor type with different gradient band gaps electrochromic conjugated polymers, named PBTz-T, PBTz-TT, PBTz-DT, PTBTO8-T, PTBTO8-TT, and PTBTO8-DT, were synthesized via direct (hetero) arylation polymerization, employing two benzothiadiazole derivatives with varying electron-accepting capabilities and three thiophene derivatives with different electron-donating capacities. The structures, optical, electrochemical, and electrochromic properties of the six polymers were investigated. As the number of fused thiophene increases, enhancing the electron-donating ability, a growth trend of electrochemical stability is observed for all polymers. Meanwhile, enhance electron-accepting capabilities of acceptors (from benzotriazole to benzothiadiazole) significantly lower the electronic band gap and improve electrochemical stability. PBTz-DT boasts a bleaching time of 0.3 s, outperforming most reported electrochromic polymers. PBTz-T, at 530 nm, exhibits exceptionally high coloration efficiency, reaching 916 cm2 C⁻1, and demonstrates higher electron utilization and lower energy consumption, making it an excellent candidate for high-performance electrochromic devices. This work compared studies the relationship of gradient band gaps of electrochromic conjugated polymers and their electrochemical and electrochromic performance, offers new insights into enhancing the electrochemical stability and synthesizing high coloration efficiency electrochromic materials.

Arylation of Secondary Phosphines with Diaryliodonium Salts under Metal‐Free and Non‐Photochemical Conditions

A new, efficient, as well as metal‐ and irradiation‐free approach for the direct arylation of secondary phosphines has been developed. The reaction employs diaryliodonium salts as electrophilic aryl‐transfer reagents, effecting the P–Ar bond‐formation in a single step, under mild conditions, using t‐BuOK as a base and DMSO as a solvent, at room temperature. The protocol furnishes expedient access to diverse unsymmetrical triarylphosphines and, upon a one‐pot oxidation, the corresponding triarylphosphine oxides. Experimental and computational studies support the inner sphere aryl‐transfer mechanism through a reductive coupling at the hypervalent iodine center. The calculations also point to a key role played by potassium ions, providing extra stabilization to the P–C bond‐forming transition state by binding the reactants via cation‐π interactions.

Comprehensive Review on the Synthesis of [1,2,3]Triazolo[1,5-a]Quinolines.

This report outlines the evolution and recent progress about the different protocols to synthesize the N-heterocycles fused hybrids, specifically [1,2,3]triazolo[1,5-a]quinoline. This review encompasses a broad range of approaches, describing several reactions for obtaining this since, such as dehydrogenative cyclization, oxidative N-N coupling, Dieckmann condensation, intramolecular Heck, (3+2)-cycloaddition, Ullman-type coupling and direct intramolecular arylation reactions. We divided this review in three section based in the starting materials to synthesize the target [1,2,3]triazolo[1,5-a]quinolines. Starting materials containing quinoline or triazole units previously formed, as well as starting materials which both quinoline and triazole units are formed in situ. Different methods of obtaining are described, such as metal-free or catalyzed conditions, azide-free, using conventional heating or alternative energy sources, such as electrochemical and photochemical methods. Mechanistic insights underlying the reported reactions were also described in this comprehensive review.

Visible Light-Induced Radical Cascade Functionalization of Quinoxalin-2(1H)-ones: Three-Component 1,2-Di(hetero)arylation Approach with Styrenes and Thianthrenium Salts.

The additive-free visible light-induced three-component 1,2-di(hetero)arylation of styrenes was developed using quinoxalin-2(1H)-ones and thianthrenium salts. The purple visible light excitable quinoxalin-2(1H)-ones were utilized for the single-electron transfer to aryl thianthrenium salts, where the generated aryl radical species underwent the addition cascade to styrenes and quinoxalin-2(1H)-ones. The direct aryl radical addition to quinoxalin-2(1H)-ones also led to the formation of a side product, C3-aryl quinoxalin-2(1H)-ones, capable of a photoredox process to help the formation of 1,2-di(hetero)arylation products.

Palladium-Catalyzed Cyclization and Direct Arylation of 1-[2-(2,2-Dibromoethenyl)phenyl]-1H-pyrrole with Allenes.

A novel and efficient palladium-catalyzed highly regioselective reaction of 1-[2-(2,2-dibromoethenyl)phenyl]-1H-pyrrole with allenes was realized to synthesize pyrrolo[1,2-a]quinolones. The tandem process involves intermolecular cyclization and intramolecular direct arylation, leading to the formation three new C-C bonds and two new rings. Notably, this transformation exhibits broad substrate scope and high functional group tolerance.

Easy Direct Functionalization of 2D MoS2 Applied in Covalent Hybrids with PANI as Dual Blend Supercapacitive Materials

AbstractThe pressing demand for more sustainable energy provision and the ongoing transition toward renewable resources underline the critical need for effective energy storage solutions. To address this challenge, scientists persistently explore new compounds and hybrids and, in such a dynamic research field, 2D materials, particularly transition metal di‐chalcogenides (TMDCs), show great potential for electrochemical energy storage uses. Simultaneously, also conductive polymers (CPs) are interesting and versatile supercapacitor materials, especially polyaniline (PANI), which is extensively studied for this purpose. In this work, a powerful method to combine TMDCs and PANI into covalently grafted hybrids starting from aniline functionalized few‐layers 1T‐MoS2, attained by a facile direct arylation with iodoaniline, is presented. The hybrids provide circa 70 F g−1 specific capacitance in a pseudo device setup, coupled with a robust capacitance retention of well over 80% for up to 5000 cycles. These findings demonstrate the potential of similar covalent composites to work as active components for novel, innovative energy storage technologies. At the same time, the successful synthesis marks the efficacy of direct covalent grafting of conductive polymer on the surface of 2D TMDCs for stable functional materials.

Palladium‐N‐heterocyclic Carbene Complexes: Synthesis, Characterization and Catalytic Application of C−H Activation for Carboxaldehyde Derivatives

AbstractA series of palladium‐N‐heterocyclic carbene complexes (2 a‐e) were synthesized from corresponding N‐heterocyclic carbene precursors (1 a‐e) in good yields. The structural analysis of all novel compounds was done by spectroscopic methods and elemental analysis was also performed to evaluate the purity of the complexes. Further confirmations of complexes 2 a‐d were provided by X‐ray crystallography technique. Under optimized reaction conditions, the catalytic activity of the palladium‐N‐heterocyclic carbene complexes was reviewed by direct arylation of furan‐2‐carboxaldehyde and 1‐methylpyrrole‐2‐carboxaldehyde with varied aryl halides. This arylation showed productive and selective reaction at the C5‐position of heteroaryl derivatives.

Dual‐Catalytic Structural Isomerisation as a Route to α‐Arylated Ketones

AbstractIsomerisation reactions provide streamlined routes to organic compounds which are otherwise hard to directly synthesise. The most common forms are positional, geometrical or stereochemical isomerisations which involve the relocation of a double bond or a change in relative location of groups in space. In contrast, far fewer examples of structural (or constitutional) isomerisation exist where the connectivity between atoms is altered. The development of platforms capable of such rearrangement poses a unique set of challenges because chemical bonds must be selectively cleaved, and new ones formed without overall addition or removal of atoms. Here, we show that a dual catalytic system can enable the structural isomerisation of readily available allylic alcohols into more challenging‐to‐synthesise α‐arylated ketones via a H‐atom transfer initiated semi‐pinacol rearrangement. Key to our strategy is the combination of a cobalt catalyst and photocatalyst under reductive, protic conditions which allows intermediates to propagate catalytic turnover. By providing an unusual disconnection to structural motifs which are difficult to access through direct arylation, we anticipate inspiring other advanced catalytic isomerisation strategies that will further retrosynthetic logic for complex molecule synthesis.

Dual-Catalytic Structural Isomerisation as a Route to α-Arylated Ketones.

Isomerisation reactions provide streamlined routes to organic compounds which are otherwise hard to directly synthesise. The most common forms are positional, geometrical or stereochemical isomerisations which involve the relocation of a double bond or a change in relative location of groups in space. In contrast, far fewer examples of structural (or constitutional) isomerisation exist where the connectivity between atoms is altered. The development of platforms capable of such rearrangement poses a unique set of challenges because chemical bonds must be selectively cleaved, and new ones formed without overall addition or removal of atoms. Here, we show that a dual catalytic system can enable the structural isomerisation of readily available allylic alcohols into more challenging-to-synthesise α-arylated ketones via a H-atom transfer initiated semi-pinacol rearrangement. Key to our strategy is the combination of a cobalt catalyst and photocatalyst under reductive, protic conditions which allows intermediates to propagate catalytic turnover. By providing an unusual disconnection to structural motifs which are difficult to access through direct arylation, we anticipate inspiring other advanced catalytic isomerisation strategies that will further retrosynthetic logic for complex molecule synthesis.

Asymmetric Synthesis of Axially Chiral N, N‐1,2‐Pentatomic Heterobiaryl Diamines by an Organocatalytic Arylation Reaction

The utilization of axially chiral biaryl diamines has been widely acknowledged as highly advantageous structures for the advancement of chiral catalysts and ligands. This highlights their extensive range of applications in asymmetric catalysis and synthesis. Herein, we devised a direct arylation reactions of 5‐aminopyrazoles with azonaphthalenes, utilizing chiral phosphoric acid as the catalyst. This method delivers structurally novel atroposelective N, N‐1,2‐azole heteroaryl diamines with high yields (up to >98%) and good to excellent enantiomeric ratios while exhibiting a wide range of substrate compatibility.

Dimension-matching crystallized linear conjugated polymer/graphitic carbon nitride heterojunctions for boosting visible/near-infrared light photocatalytic hydrogen production

Linear conjugated polymer photocatalysts remain suffer from insufficient near-infrared light absorption and poor photogenerated-carriers separation efficiency caused by twisted backbone, limiting their further application for photocatalytic water splitting to produce hydrogen energy. Herein, we first synthesized crystallized 2D poly(thiophene-co-nitrothiophene) (PN) with narrow band gap through direct (hetero) arylation polymerization (DHAP) method, then constructed dimension-matching PN/graphitic carbon nitride (CN) heterojunctions (PN/CN) with 2D/2D structure for visible/near-infrared light photocatalytic hydrogen production. The resulting 2D/2D heterojunctions exhibit excellent visible/near-infrared light absorption and photocatalytic activates. The ratio-optimized 15PN/CN shows boosting hydrogen production activity up to 11.73 mmol/hg−1 under visible/near-infrared light (λ > 420 nm) irradiation, which is ∼ 30-time and ∼ 46.9-time improvement than that of PN and CN separately. Notably, the apparent quantum yield (AQY) of 15PN/CN is calculated to be 2.35 % at 700 nm and 0.62 % at 800 nm. It is proved that the π − π interaction of dimension-matching heterojunctions between PN and CN facilitates electrons transfer from LUMO of PN to LUMO of CN. This study provides another new train of thought for reasonably developing dimension-matching polymer heterojunctions by manipulating crystallinity and band structure of linear conjugated polymers for efficient visible/near-infrared light photocatalytic hydrogen production.

Synthesis of Accessible Triphenylamine End‐Capped Oligothiophene Emitters for Solution Processed and Printed OLEDs

AbstractDisplays have become ubiquitous in our modern and highly interconnected lives. Complex vacuum processed multi‐stacks are widely integrated into high tech, high value products such as smart phones, while solution processed large area single‐layer OLEDs appear more adequate for basic applications focusing on recyclability such as packaging, road signage, advertising, and single‐use health care products. In this context, we report herein the design, synthesis, and characterization of an accessible series of oligothiophenes end‐capped triphenylamines that were preprepared by atom‐economical direct (hetero)arylation reactions and successfully used as emitter in solution processed devices, from lab scale to large area printed and flexible demonstrator.

Construction of diverse adaptive camouflage nets based on soluble yellow-to-green switching electrochromic materials

The potential application of electrochromic (EC) materials and devices as adaptive camouflage in diverse environments requires further investigation. In this study, we aimed to enhance the camouflage effect of electrochromic devices (ECDs) by developing innovative EC camouflage nets. Three soluble EC materials (FTP, FEP and FBP) were synthesized by incorporating phenothiazine and ProDOT with different donors through direct(hetero) arylation polymerization. Due to the fine-tuning of the energy gap, the three materials exhibit yellow, yellowish-brown and reddish-brown colors in their neutral states, respectively. Particularly, FTP and FEP can switch between different yellow-to-green with superior EC performance. Furthermore, FTP-PEDOT and FEP-PEDOT ECDs were constructed. Notably, the FEP-PEDOT ECD demonstrated enhanced EC performance, characterized by a more noticeable yellow-to-green switch, faster switching times and improved cycle stability. To meet the adaptability for multi-environmental camouflage and wearable applications, we created diverse camouflage patterns using the mask-spray technique and developed three types (“stripe”/ “cross stripe”/ “block”) camouflage net ECDs. This study offers a comprehensive approach for developing adaptive camouflage nets tailored to diverse real combat settings.

Chromophore Optimization in Organometallic Au(III) Cys Arylation of Peptides and Proteins for 266 nm Photoactivation.

Cysteine is the most reactive naturally occurring amino acid due to the presence of a free thiol, presenting a tantalizing handle for covalent modification of peptides/proteins. Although many mass spectrometry experiments could benefit from site-specific modification of Cys, the utility of direct arylation has not been thoroughly explored. Recently, Spokoyny and co-workers reported a Au(III) organometallic reagent that robustly arylates Cys and tolerates a wide variety of solvents and conditions. Given the chromophoric nature of aryl groups and the known susceptibility of carbon-sulfur bonds to photodissociation, we set out to identify an aryl group that could efficiently cleave Cys carbon-sulfur bonds at 266 nm. A streamlined workflow was developed to facilitate rapid examination of a large number of aryls with minimal sample using a simple test peptide, RAAACGVLK. We were able to identify several aryl groups that yield abundant homolytic photodissociation of the adjacent Cys carbon-sulfur bonds with short activation times (<10 ms). In addition, we characterized the radical products created by photodissociation by subjecting the product ions to further collisional activation. Finally, we tested Cys arylation with human hemoglobin, identified reaction conditions that facilitate efficient modification of intact proteins, and evaluated the photochemistry and activation of these large radical ions.

Direct Arylation Polycondensation‐Derived Polythiophene Achieves Over 16% Efficiency in Binary Organic Solar Cells via Tuning Aggregation and Miscibility

AbstractPolythiophenes are the most appealing donor materials in organic solar cells (OSCs) due to their simple chemical structures. However, the top‐performance polythiophenes are typically synthesized via Stille polycondensation, which is problematic due to significant toxicity and poor atom economy. By contrast, direct arylation polycondensation (DArP) is an eco‐friendly, and atom‐efficient alternative for synthesizing conjugated polymers, while the best efficiency for DArP‐derived polythiophenes is below 12%. This study reports a series of polythiophene‐based donors synthesized via DArP. Among these, PT4F‐Th reaches a power conversion efficiency (PCE) of 16.4%, which not only matches the current record for polythiophene‐based donor materials, but also marks the highest PCE achieved by DArP‐derived donors to date. The superior performance of PT4F‐Th is largely attributed to its optimal temperature‐dependent aggregation behavior and moderate miscibility with acceptors, along with the highest crystallinity among the candidates, resulting in the most favorable blend film morphology. This study underscores the significant potential of DArP‐derived polythiophenes in developing high‐performance and eco‐friendly OSCs.

Pd(0)/TPPMS‐Catalyzed Tsuji–Trost Type Cross‐Coupling of Allylic Alcohols with Organoboron Compounds in Water

AbstractWe demonstrated that the combination of a Pd(0) catalyst and a water‐soluble TPPMS ligand has high activity for the direct arylation of readily available allylic alcohols in the Tsuji–Trost type cross‐coupling. Various organoboron reagents can be applied, enabling rapid access to the corresponding arylated products with a wide range of functional group tolerance. Kinetic studies revealed a first‐order rate dependence for the allylic alcohol, boronic acid, CsF and Pd(0)/TPPMS concentrations. A Hammett study found a slightly positive ρ value of 0.79, suggesting that a partial negative charge is generated on the aromatic ring of the aryl boronate in the rate‐determining transmetalation step. Based on several control experiments, we concluded that the transmetalation employing CsF would proceed via the oxo‐palladium mechanism.

Highly Transmissive, Processable, Highly Conducting and Stable Polythiophene Derivatives via Direct (Hetero)arylation Polymerization.

The development of modern optoelectronic devices increases the need for lightweight and flexible transparent conductors. It is thus essential to develop new eco-friendly materials that can be easily processed for the fabrication of such devices. For this purpose, the synthesis of self-doped, highly conducting, transmissive, and water-processable polythiophene derivatives was performed via the direct heteroarylation polymerization method and a protection/deprotection strategy. Stable conductivities up to 1000 S cm-1 have been obtained. Champion materials (P1 and P7) were scaled and processed via the roll-to-roll compatible slot-die coating method to demonstrate their large area applicability. The best coated films exhibited optical transmittance greater than 79% at 550 nm with sheet resistances of 116 Ω □-1. These values are comparable to indium-tin oxide on plastic and thus present a viable alternative to metal oxide-based electrodes.

Basicity‐Controlled Reactivity of meta‐OTf‐Substituted Diaryliodonium Salts for Direct Arylation or Diels‐Alder Cycloaddition of Pyrrole Derivatives

AbstractIn this study, we explored the reactivity of meta‐trifluoromethanesulfonate (OTf) substituted diaryliodonium salts under alkaline conditions. Two distinct pathways with direct arylation of pyrrole derivatives and Diels‐Alder cycloaddition via aryne intermediates, have been found upon the relative alkalinity strength of potassium carbonates or hydroxides. This approach offers a straightforward and efficient route to synthesize heterocyclic aromatics under mild reaction conditions with tolerance of various functional groups.

Toward rapid and efficient protocols: Synthesis of benzotriazole-based π-conjugated polymers via direct arylation polycondensation under aerobic conditions

π-Conjugated polymers (CPs) are widely used in the field of high-performance plastic electronics. However, the development of sustainable and efficient methods for synthesizing donor-acceptor (D–A)-type CPs remains challenging for their industrialization. In this study, we introduce a simple and rapid direct arylation polycondensation (DArP) technique for preparing various D–A benzotriazole-based π-CPs with high molecular weights under aerobic conditions in two hours. Additionally, the method demonstrates not only excellent yields but also copolymers with nearly defect-free structures. Via a minor modification involving the use of twenty or more equivalents of the base K2CO3 and refluxing the solvent, high molecular weight copolymers can be achieved in a short reaction time under oxygen and moisture conditions. Therefore, this finding presents a direct synthetic protocol that utilizes commercially available and air-stable catalyst precursors to produce high-quality π-CPs suitable for optoelectronic applications.

Palladium supported on alumina as a highly active heterogeneous catalyst for direct arylation of 6-substituted imidazo[2,1-b]thiadiazole via C[sbnd]H bond activation reaction

Fast, atom-economical, phosphine-free, and eco-friendly microwave-irradiated reactions permitting the “green synthesis” of 5,6-disubstituted imidazo[2,1-b]thiadiazole derivatives using heterogeneous palladium catalyst in triethylammonium 2-(1,1-dioxido-3-oxobenzo[d]isothiazol-2(3H)-yl)acetate ([Et3NH][Sac-CH3CO2]) ionic liquid via CH bond activation reaction of 6-substituted imidazo[2,1-b]thiadiazole derivatives, are reported. This method provides a straightforward route to a wide variety of substituted imidazo[2,1-b]thiadiazoles and has the advantages of reusability of the heterogeneous catalyst, simple methodology, high yields, and easy work-up.