Cyano Functionalities Research Articles

Control of Photoinduced Charge Transfer Through Selective Cyanation of Spirofluorene‐Bridged N‐Heterotriangulenes

AbstractA series of selectively cyanated spirofluorene‐bridged N‐heterotriangulenes (N‐HTAs) with three to nine cyano groups are synthesized via a newly developed synthetic strategy. X‐ray crystallographic analysis of the compounds revealed a tripod‐like molecular shape with the fluorenyl moieties arranged in a perpendicular fashion around the nitrogen‐centered N‐HTA core. The solid state packing is found to be strongly influenced by the dipolar cyano functions. Under electrochemical conditions, the N‐HTA core is prone to undergo a reversible one‐electron oxidation toward the nitrogen‐centered radical cation, which becomes increasingly difficult as the number of the cyano acceptors, and consequently the ionization potential, increases. While a clear bathochromic shift is observed in the steady‐state UV–vis absorption spectra, the fluorescence behavior is complex and strongly dependent on the position and number of the cyano groups. The compound with six cyano functions at the fluorenyl flanks is unique within the series and shows a broad emission maximum at 499 nm and an unusually large Stokes shift of 10 171 cm−1. Time‐resolved absorption and fluorescence measurements, supported by quantum chemical calculations, identified this spectroscopic signature to originate from fast and robust photoinduced intramolecular charge transfer.

Semiconducting Polymers Based on Simple Electron‐Deficient Cyanated trans‐1,3‐Butadienes for Organic Field‐Effect Transistors

AbstractDeveloping high‐performance but low‐cost n‐type polymers remains a significant challenge in the commercialization of organic field‐effect transistors (OFETs). To achieve this objective, it is essential to design the key electron‐deficient units with simple structures and facile preparation processes, which can facilitate the production of low‐cost n‐type polymers. Herein, by sequentially introducing fluorine and cyano functionalities onto trans‐1,3‐butadiene, we developed a series of structurally simple but highly electron‐deficient building blocks, namely 1,4‐dicyano‐butadiene (CNDE), 3‐fluoro‐1,4‐dicyano‐butadiene (CNFDE), and 2,3‐difluoro‐1,4‐dicyano‐butadiene (CNDFDE), featuring a highly coplanar backbone and deep‐positioned lowest unoccupied molecular orbital (LUMO) energy levels (−3.03–4.33 eV), which render them highly attractive for developing n‐type semiconducting polymers. Notably, all these electron‐deficient units can be easily accessed by a two‐step high‐yield synthetic procedure from low‐cost raw materials, thus rendering them highly promising candidates for commercial applications. Upon polymerization with diketopyrrolopyrrole (DPP), three copolymers were developed that demonstrated unipolar n‐type transport characteristics in OFETs with the highest electron mobility of >1 cm2 V−1 s−1. Hence, CNDE, CNFDE, and CNDFDE represent a class of novel, simple, and efficient electron‐deficient units for constructing low‐cost n‐type polymers, thereby providing valuable insight for OFET applications.

Semiconducting Polymers Based on Simple Electron-Deficient Cyanated trans-1, 3-Butadienes for Organic Field-Effect Transistors.

Developing high-performance but low-cost n-type polymers remains a significant challenge in the commercialization of organic field-effect transistors (OFETs). To achieve this objective, it is essential to design the key electron-deficient units with simple molecular structure and facile preparation process, which can directly facilitate the production of low-cost n-type polymers. Herein, by sequentially introducing fluorine and cyano functionalities onto trans-1,3-butadiene π-skeleton, we developed a series of structurally simple but highly electron-deficient building blocks, namely 1,4-dicyano-butadienes (CNDE), 3-fluoro-1,4-dicyano-butadienes (CNFDE), and 2,3-difluoro-1,4-dicyano-butadienes (CNDFDE), featuring highly coplanar backbone and deep-positioned lowest unoccupied molecular orbital (LUMO) energy levels (-3.03-4.33 eV), which render them highly attractive building blocks for developing n-type semiconducting polymers. Notably, all these electron-deficient units can be easily accessed via a two-step high-yield synthetic protocol from low-cost raw materials, thus rendering them highly promising candidates for commercial applications. Upon polymerized with diketopyrrolopyrrole (DPP) units, three copolymers are developed and demonstrated unipolar n-type transport characteristics in OFETs with the highest electron mobility > 1 cm2 V-1 s-1. Hence, CNDE, CNFDE, and CNDFDE represent a class of novel, simple, and efficient electron-deficient units for constructing low-cost n-type polymers, providing valuable insights for the OFET applications.

Synthesis of 2,4‐dihydrochromeno[3,4‐d][1,2,3]triazoles and 5‐(2H‐chromen‐3‐yl)‐1H‐tetrazoles via regioselective 1,3‐dipolar cycloaddition of 2H‐chromene‐3‐carbonitriles with NaN3

AbstractConjugated cyano cyclo‐olefins modified as highly regioselective dipolarophiles in 1,3‐dipolar cycloaddition with NaN3 to synthesize corresponding fused 1,2,3‐triazole and 1H‐tetrazole derivatives. The first example of catalytic 1,3‐dipolar cycloaddition of NaN3 with 2H‐chromene‐3‐carbonitriles and subsequent elimination/cyclization of cyano functionality is designated. In presence of catalytic amount of p‐TSA or AgNO3, 2H‐chromene‐3‐carbonitriles react with NaN3 discretely producing 2,4‐dihydrochromeno[3,4‐d][1,2,3]triazoles or 5‐(2H‐chromen‐3‐yl)‐1H‐tetrazoles respectively, in good to excellent yields (i. e. 51–88 % or 85–97 %) with high regioselectivity and wide substrate scope adequacy.

The Renaissance of Organo Nitriles in Organic Synthesis.

In the arena of functional group-oriented organic synthesis, nitrile or cyano functionality is of immense importance. The presence of nucleophilic N-atom, π-coordinating ability of the triple bond, and electrophilic C-center imparts unique and interesting reactivities. Owing to the ability of the nitrile to transform into various other functional groups or intermediates, the chemistry is very rich and diverse. In particular, the involvement of nitrile in numerous organic reactions such as inter- or intramolecular alkyne insertion, [2+2+2] cycloaddition with alkynes, [3+2] cycloaddition with azides, [4+2] cycloaddition with dienes allow the synthesis of many important carbo- and heterocycles. Furthermore, the nitrile serves as a directing group in many C-H bond functionalization reactions to introduce diverse functionalities and participate as a radical acceptor in radical cascade strategies to obtain a large variety of functional molecules. This review mainly focuses on the reactivity and diverse synthetic application of the nitrile including C-H bond functionalization, alkyne insertion, cycloaddition, and thermal or photochemical cascade strategy. The objective of the current review aims at bringing out the striking collection of various nitrile-triggered organic transformations.

Endowing imidazole derivatives with thermally activated delayed fluorescence and aggregation‐induced emission properties for highly efficient non‐doped organic light‐emitting diodes

AbstractThe development and enrichment of high‐performance organic fluorophores that simultaneously possess thermally activated delayed fluorescence (TADF) and aggregation‐induced emission (AIE) properties is going pursued but remains a great challenge due to severe exciton quenching. Herein, a systematical investigation on imidazole moiety has successfully given rise to a series of highly efficient imidazole‐based TADF‐AIE luminogens for the first time. The attachment of two cyano functionalities on imidazole moiety can significantly increase the electron‐withdrawing ability, so as to realize TADF emissions with small singlet‐triplet energy gaps (ΔEST) values. Meanwhile, the installation of a steric hindrance group at N1 position of imidazole moiety can twist the geometry between imidazole and phenyl bridge, thus transforming imidazole derivative from an aggregation‐caused quenching emitter into an AIE luminogen. Consequently, the non‐doped organic light‐emitting diodes (OLEDs) utilizing these TADF‐AIE luminogens as emitters exhibit outstanding sky‐blue and green emissions, with external quantum efficiency (EQE) as high as 20.0% and low efficiency roll‐off (EQE at 1000 cd m−2, 16.1%). These values represent the state‐of‐the‐art performance for all imidazole‐based OLED devices, which illustrates the significant potential of imidazole derivatives in assembling high‐performance OLEDs.

Tuning mechanical responses of crystalline cadmium(II) coordination polymers through cyano functionality and halide anions

Tuning mechanical responses of crystalline cadmium(II) coordination polymers through cyano functionality and halide anions

Recent Advances in Molecular Design of Organic Thermoelectric Materials

Recent Advances in Molecular Design of Organic Thermoelectric Materials

Catalytic Asymmetric Cyanoalkylation of Electron-Deficient Olefins with Potassium Cyanide and Alkyl Halides.

The stereoselective cyanoalkylation of electron-deficient olefins with potassium cyanide and alkyl halides was developed based on the utilization of modular chiral 1,2,3-triazolium salts featuring a hydrogen bond-donor ability as catalysts. The reaction involving multiple carbon-carbon bond formations proceeds via the enantioselective conjugate addition of a cyanide ion and the consecutive catalyst-controlled diastereoselective alkylation of intermediary chiral triazolium enolates. Control experiments revealed that the use of a properly tuned chiral triazolium ion as a catalyst and the presence of the cyano functionality in the intermediary enolate are of crucial importance for achieving high levels of acyclic absolute and relative stereocontrol.

Crucial role of cyanides for high-potential electrochemical reduction reaction

Despite the potential of organic materials for cathodes in lithium-ion batteries arising from their eco-friendly production processes and structural flexibility, their redox properties are not comprehensively unveiled. In this work, the redox properties and performances for chloranil derivatives with one to four cyano functional group(s) are studied to assess their potential as high-potential organic cathode materials. The well-designed computational protocol is employed to reliably predict the redox behaviors for the organic compounds. This investigation highlights synergistic effects of carbonyls and cyanides on improving the electrochemical properties, exhibiting the remarkably high open-circuit redox potential (4.50 ​V vs. Li/Li+) and theoretical performances (515 ​mA ​h/g and 1517 ​mWh/g) for the chloranil derivative with four cyano functionalities. Furthermore, this study emphasizes that the redox potential of a chloranil derivative strongly relies not only on its structural variation but also on the Li-involved discharging process, electronic properties, and, most importantly, “solvation energy”. A universal correlation of redox potential with electron affinity and solvation energy addresses that chloranils would experience two-stage transition behaviors during the discharging process, implying a critical role of solvation energy in their cathodic deactivation and thus suggesting a smart approach for the systematic design of high-performance organic cathodes. Electrostatic potential maps unambiguously describe the change in the reductive ability of a chloranil derivative during the Li-involved discharging process.

A Narrow‐Bandgap n‐Type Polymer Semiconductor Enabling Efficient All‐Polymer Solar Cells

Currently, n-type acceptors in high-performance all-polymer solar cells (all-PSCs) are dominated by imide-functionalized polymers, which typically show medium bandgap. Herein, a novel narrow-bandgap polymer, poly(5,6-dicyano-2,1,3-benzothiadiazole-alt-indacenodithiophene) (DCNBT-IDT), based on dicyanobenzothiadiazole without an imide group is reported. The strong electron-withdrawing cyano functionality enables DCNBT-IDT with n-type character and, more importantly, alleviates the steric hindrance associated with typical imide groups. Compared to the benchmark poly(naphthalene diimide-alt-bithiophene) (N2200), DCNBT-IDT shows a narrower bandgap (1.43 eV) with a much higher absorption coefficient (6.15 × 104 cm-1 ). Such properties are elusive for polymer acceptors to date, eradicating the drawbacks inherited in N2200 and other high-performance polymer acceptors. When blended with a wide-bandgap polymer donor, the DCNBT-IDT-based all-PSCs achieve a remarkable power conversion efficiency of 8.32% with a small energy loss of 0.53 eV and a photoresponse of up to 870 nm. Such efficiency greatly outperforms those of N2200 (6.13%) and the naphthalene diimide (NDI)-based analog NDI-IDT (2.19%). This work breaks the long-standing bottlenecks limiting materials innovation of n-type polymers, which paves a new avenue for developing polymer acceptors with improved optoelectronic properties and heralds a brighter future of all-PSCs.

Aroyl and acyl cyanides as orthogonal protecting groups or as building blocks for the synthesis of heterocycles.

α-Cyanoketones represent a synthetically attractive scaffold possessing bifunctional reactivity which enabled synthesis of a diversity of products. This involves reaction of nucleophiles with electrophilic carbonyl carbon performing an efficient and regioselective way to acylation reaction, cycloaddition of activated cyano function with dipolarophiles, metal-catalyzed cross-dehydrogenative coupling carbocyanation across C-C multiple bonds as well as hydrocyanation. This review provides the recent developments in the chemistry of α-cyanoketones which will be beneficial for researchers and scientists in such field.

Weak Donor-/Strong Acceptor-Linked Anthracenyl π-Conjugates as Solvato(fluoro)chromophore and AEEgens: Contrast between Nitro and Cyano Functionality.

Steady development on photophysical behaviors for a variety of organic fluorophores inspired us to generate anthracene-based fluorescent molecules with a strong acceptor and a significantly weak donor through a π-spacer. Such molecules are found to have substantial twisted conformational orientations in the solid state and enhanced apolar character because of the attachment of tolyl or mesityl group with an anthracenyl core. Upon exposure to a variety of solvents, strong solvatochromism was noticed for 4-nitro compound (84 nm red shift) in contrast to the cyano analogue (18 nm red shift). Both these probes were highly emissive in apolar solvents while nitro-analogue, in particular, could discriminate the solvents of ET(30) (a measure of microscopic solvent polarity) ranging from 31 to 37. Thus, 4-nitro compounds can be successfully employed to detect and differentiate the apolar solvents. On the contrary, the 2-nitro analogue is almost nonemissive for the same range of solvents perhaps because of favorable excited-state intramolecular proton-transfer process. The fundamental understanding of solvatochromic properties through the formation of twisted intramolecular charge-transfer (TICT) state is experimentally analyzed by synthesizing and studying the π-conjugates linked to only benzene in place of nitro or cyanobenzene, which exhibits no solvatochromism and that helped finding the possible emission, originated from the locally excited state. Moreover, the molecular structures for these compounds are determined by the single-crystal X-ray diffraction studies to examine the change in emission properties with molecular packing and alignment in the aggregated state. The measurement of dihedral angles between the substituents and anthracenyl core was helpful in finding the possible extent of electronic conjugations within the system to decipher both solvatochromism and aggregation enhanced emission (AEE)-behavior. The cyano analogue exhibited prominent AEE-behavior, whereas nitro analogues showed the aggregation-caused quenching effect. The reason behind such dissimilarity in solvatochromism and AEE-behavior between cyano- and nitro-linked anthracenyl π-conjugates are also addressed through experimental outcomes.

Stability of Trithiocarbonate RAFT Agents Containing Both a Cyano and a Carboxylic Acid Functional Group.

The hydrolytic degradation of widely used cyano-containing, acid-bearing trithiocarbonate reversible addition-fragmentation chain-transfer (RAFT) agents has been identified and shown to effect the RAFT polymerization and end-group fidelity of PMMA polymers. The hydrolysis occurred when the RAFT agents were stored under the recommended conditions. Degradation was identified in both commercially available and popular synthetic RAFT agents. 1H and 13C NMR as well as mass spectroscopy show that the cyano functionality hydrolyzes to the amide adduct. Doping of this amide degradation product into RAFT polymerizations of MMA results in increased dispersities and changes in expected end-group fidelities. The ability to identify this degradation product and remove it from the RAFT agent before use will allow better control over polymer properties and postmodification processes commonly used in complex polymer systems, nanomedicines, and bioconjugates.

The Cyanopivaloyl Ester: A Protecting Group in the Assembly of Oligorhamnans

Protecting groups play a vital role in the assembly of oligosaccharides. The pivaloyl (Piv) ester is commonly used to ensure 1,2‐trans‐selective glycosylation reactions. A significant drawback of the Piv ester is its stability, necessitating strong alkaline conditions for its removal. We here present the cyanopivaloyl (CNPiv) group, a modified pivaloyl group having a cyano group appended to the tert‐butyl moiety. The CNPiv group benefits from the profitable features of the Piv group (stability and effective neighboring‐group participation with minimal orthoester formation during glycosylation reactions), but can be removed under mild conditions (reduction of the cyano function followed by mild base treatment). The applicability of the CNPiv group is demonstrated in the assembly of two rhamnose oligosaccharides, a hexarhamnan that represents a fragment of the capsular polysaccharide of Enterococcus faecium and a tetrarhamnan that is part of the polyrhamnose backbone of the Lancefield Group A carbohydrate (GAC).

Myritonines A-C, Alkaloids from Myrioneuron tonkinensis Based on a Novel Hexacyclic Skeleton.

Myritonines A-C (1-3), three new alkaloids bearing an unprecedented heterohexacyclic skeleton, were isolated from Myrioneuron tonkinensis. Their structures were determined by a combination of spectroscopic data and single-crystal X-ray diffraction analysis. Compound 3 represents the first Myrioneuron alkaloid featuring a unique trans-decahydroquinoline motif and was also found to possess a rare cyano functionality. Compounds 1 and 2 showed inhibition against the hepatitis C virus in vitro.

Functionalization of Styrenes by Copper-Catalyzed Borylation/ ortho-Cyanation and Silver-Catalyzed Annulation Processes.

An efficient two-step method for the assembly of indanone derivatives starting from a simple vinyl arene has been developed. The sequence first involves addition of bis(pinacolato)diboron (B2 pin2 ) and N-cyano-N-phenyl-p-methylbenzenesulfonamide (NCTS) to a broad range of styrenes by utilizing IMesCuCl as catalyst. This step simultaneously accomplishes hydroboration of the alkene and ortho cyanation of the benzene unit. The products thus obtained are further functionalized by a AgNO3 /Selectfluor-mediated coupling of the BPin and cyano functionalities to annulate a new five-membered ring. This combined two-step sequence provides a versatile method for the site-selective derivatization of a broad range of vinyl arene substrates.

Functionalization of Styrenes by Copper‐Catalyzed Borylation/ ortho‐Cyanation and Silver‐Catalyzed Annulation Processes

AbstractAn efficient two‐step method for the assembly of indanone derivatives starting from a simple vinyl arene has been developed. The sequence first involves addition of bis(pinacolato)diboron (B2pin2) and N‐cyano‐N‐phenyl‐p‐methylbenzenesulfonamide (NCTS) to a broad range of styrenes by utilizing IMesCuCl as catalyst. This step simultaneously accomplishes hydroboration of the alkene and ortho cyanation of the benzene unit. The products thus obtained are further functionalized by a AgNO3/Selectfluor‐mediated coupling of the BPin and cyano functionalities to annulate a new five‐membered ring. This combined two‐step sequence provides a versatile method for the site‐selective derivatization of a broad range of vinyl arene substrates.

Thermal Reaction of 4-(p-Aminophenyl)-1-sulfonyl-1,2,3-triazoles Furnishing Benzoyl Cyanides through N-Sulfinyl Imine Intermediates

Abstract A thermal reaction of 4-(p-aminophenyl)-1-sulfonyl-1,2,3-triazoles forming benzoyl cyanides is reported. A carbene species thermally generated from the triazole by denitrogenation undergoes intramolecular oxygen migration from sulfur to carbon, giving an N-sulfinyl benzoylimine intermediate. The subsequent Cope-type elimination of the sulfinyl group gives rise to cyano functionality.

ChemInform Abstract: General Method for Functionalized Polyaryl Synthesis via Aryne Intermediates.

A method for base-promoted arylation of arenes and heterocycles by aryl halides and aryl triflates is described. Additionally, in situ electrophilic trapping of ArLi intermediates generated in the reaction of benzyne with deprotonated arenes or heterocycles has been developed, providing rapid and easy access to a wide range of highly functionalized polyaryls. Base-promoted arylation methodology complements transition-metal-catalyzed direct arylation and allows access to structures that are not easily accessible via other direct arylation methods. The reactions are highly functional-group tolerant, with alkene, ether, dimethylamino, trifluoromethyl, ester, cyano, halide, hydroxyl, and silyl functionalities compatible with reaction conditions.