Benzofuran Unit Research Articles

A New Phenothiazine-Based Fluorescent Sensor for Detection of Cyanide.

A new fluorescent sensor for the detection of CN- was developed based on the conjugation of phenothiazine fluorophore and benzofuran unit. By the nucleophilic attacking of CN- to the fluoroacetylamino group in the sensor, the additional reaction of CN- and carbonyl group induced the ICT (intramolecular charge transfer) effect in the molecule and caused the fluorescence quenching sensor. The titration experiments show that the sensor has good sensitivity, selectivity and quick response for CN-. In addition, the fluorescent detection of CN- in the living cell and zebrafish experiments demonstrated the value of the sensor in tracing the CN- in biological systems.

One-pot synthesis of fused-rings heterocyclic systems based on symmetrically benzofuran annulated 1,8-naphthalimides

A useful and straightforward synthetic approach to afford heteroarenes by symmetrical annulation of two benzofuran units to 1,8-naphthalene anhydrides, through a regioselective one-pot Sn–Ar/C–H activation tandem reaction is introduced herein. Two synthetic pathways are compared, highlighting that the utilization of diester derivatives improves: (i) the compatibility with the key ring expansion step, (ii) the solubility of the intermediate thus facilitating its purification, and (iii) the versatility of the final imidization. The electrochemical and spectral properties of this new class of compounds are investigated.

One-pot Syntheses of Benzo- and Benzofuran-fused Iridaoxabenzenes via CH Bond Activations of Alkyl-bridged Diphenol Derivatives.

One-pot syntheses of new π-extended metallaaromatic compounds have been developed by utilizing Ir-mediated CH bond activation of ethylene- or ethylidene-bridged diphenol derivatives. Depending on the bridging alkyl groups, two types of iridaoxabenzenes, both of which are doubly fused with benzo and benzofuran units, have been obtained. Studies on their structures and electronic characters indicate that both complexes have an aromatic character on the iridaoxacycles, and their π-conjugated systems are fully delocalized over the whole molecular skeletons. These novel metallaaromatic complexes exhibited some reactivities which are distinct from those reported for the non-fused metallaaromatic compounds.

Fluorosolvatochromic Behavior of 2,3‐Naphthalimides Expanded by Double Fusion with Benzothiophene and Benzofuran Units

AbstractAs new polycyclic aromatic hydrocarbons (PAHs) containing an imide group, we designed and synthesized 2,3‐naphthalimide fused with benzothiophene 1 or benzofuran 2. 1 and 2 have a push‐pull structure attributed to the imide group and the electron‐donating heterocyclic moieties, indicated that 1 and 2 play as a fluorosolvatochromic dye. 1 and 2 were synthesized in 3‐steps. The absorption and fluorescence spectra were measured in twelve different solvents. The absorption spectra of 1 and 2 showed a slight solvent dependence. On the other hand, a strong solvent dependence was observed in the fluorescence spectra of 1 and 2, that is, fluorosolvatochromism. The plots of the emission maximum versus the solvent polarity parameter ET(30) for 1 and 2 exhibited a good linear correlation. Multiple linear regression analysis using Catalán scale suggested that the fluorescence behavior of 1 and 2 is influenced by the acidity and dipolarity of the solvents. The changes in the dipole moment between the ground and excited states estimated by the Lippert‐Mataga equation were 7.6 D for 1 and 7.2 D for 2.

Synthesis of Benzofuran-Embedded Selena- and Telluraporphyrins.

The benzofuran-embedded selena- and telluraporphyrins are resulted by replacing the pyrrole ring that is across the selenophene/tellurophene ring in meso-tetraaryl 21-selenaporphyrin and 21-telluraporphyrin respectively by a benzofuran unit. Three examples of benzofuran-embedded selenaporphyrins and one example of benzofuran-embedded telluraporphyrin were synthesized by adopting a simple 3 + 2 synthetic protocol involving the condensation of benzofuran based tripyrrane with appropriate 2,5-bis(hydroxymethylaryl) selenophene/telluorophene to afford pure benzofuran-embedded selenaporphyrins and telluraporphyrin in 3-6% yields. The macrocycles were thoroughly characterized and studied by various spectroscopic and computational techniques. The spectral and computational studies certified their nonaromatic nature unlike aromatic meso-tetraaryl 21-selena/21-telluraporphyrins, which proves that replacement of pyrrole with a benzofuran ring results in complete alteration of electronic properties. The DFT studies revealed that the benzofuran moiety hinders π-electron delocalization in the macrocycle due to its inflexibility, and the macrocycles adopt highly deformed saddle-shaped structures. The absorption spectra of benzofuran-embedded selena- and telluraporphyrins showed one strong band at ∼350-380 nm and one broad band at ∼650-695 nm that extended up to ∼900 nm. However, the protonated derivatives of macrocycles absorb strongly in the NIR region with a band trailing up to 1200 nm. The electrochemical studies revealed that the macrocycles are electron deficient, and theoretical studies resembled the experimental observations.

Effective synthesis of regular ladder-type oligo(p-phenol)s via intramolecular SNAr O-arylation reaction

A series of novel ladder-type O-heteroarenes containing benzofuran units were effectively synthesized from the precursors via intramolecular SNAr reaction between F and OH groups in the backbone. The key intramolecular SNAr reaction was catalyst-free and highly efficient, moreover, the accurate annulation of fluorine atom ensured the regularity of the structure. We could smoothly obtain the ladder-type oligomer with seven oxygen bridges. The successes of the ladder-type oligomers also demonstrated the feasibility for preparing other regular oligomers and polymers with oxygen bridges.

New piperazine-based bis(thieno[2,3-b]pyridine) and bis(pyrazolo[3,4-b]pyridine) hybrids linked to benzofuran units: Synthesis and in vitro screening of potential acetylcholinesterase inhibitors

Two series of piperazine-based bis(thieno[2,3-b]pyridines) and bis(pyrazolo[3,4-b]pyridines) were prepared, in good yields, utilizing the appropriate bis(pyridinethione). The first series was obtained by reacting the previous synthon with different α-halogenated reagents, whereas the second series was produced by reacting the synthon with various hydrazonyl chlorides, and then cyclizing the resulting bis(hydrazonothioates). At 50 and 100 µM concentrations, the two series were screened as potential acetylcholinesterase inhibitors. The reference donepezil had inhibition percentages of 90.7 and 93.5 at the tested concentrations. Generally, bis(thieno[2,3-b]pyridine) series was found to be more effective than the other series of bis(pyrazolo[3,4-b]pyridine). Bis(thieno[2,3-b]pyridine-2-carbonitrile) inhibited acetylcholinesterase the best, with inhibition percentages of 55.2 and 88.4 at 50 and 100 µM concentrations, respectively. Furthermore, when tested at a concentration of 25 µg/mL, the prior hybrid demonstrated the best DPPH antioxidant activity, with an inhibition percentage of 81.5 when compared to the reference ascorbic acid (inhibition percentage of 88.7).

Regioselective synthesis and theoretical calculations of Bis(pyrido[2′,3′:3,4]pyrazolo[1,5-a]pyrimidines) linked to benzofuran units via piperazine spacer: A DFT, MM2, and MMFF94 study

• A novel bis(3-amino-1 H -pyrazolo[3,4- b ]pyridine) is prepared in a good yield. • A regioselective synthesis of new series of piperazine-linked bis(pyrimidines) hybrids is performed. • The new structures were elucidated by elemental and spectral analyses. • DFT and Fukui indices calculations are used to provide additional evidence for the proposed structures. • MM2, and MMFF94 minimization are used to investigate the plausible formation mechanism of the bis(pyrimidines) . Bis(enaminone), linked to benzofuran units via piperazine spacer, was prepared and used as a key intermediate in this study. It reacted for 8 h at reflux with two equivalents of 2-cyanothioacetamide in dioxane in the presence of TEA to give the corresponding bis(pyridine-2(1 H )-thione) derivative. The previous compound was reacted with two equivalents of iodomethane in methanolic sodium methoxide solution at reflux for 1 h to yield the corresponding bis(2-methylthiopyridine) derivative. Boiling of the prior compound with hydrazine hydrate in pyridine at reflux for 12 h gave the precursor bis(3-amino-1 H -pyrazolo[3,4- b ]pyridine) derivative in a good yield. Next, a regioselective protocol was conducted for the synthesis of a diverse series of the target bis(pyrido[2′,3′:3,4]pyrazolo[1,5- a ]pyrimidine) derivatives in good to excellent yields. The protocol involved the reaction of bis(3-amino-1 H -pyrazolo[3,4- b ]pyridine) with two equivalents of prop-2-en-1-ones in DMF in the presence of two equivalents of barium hydroxide at reflux for 5–7 h. To gain a better understanding of the regioselectivity observed in these reactions, DFT calculations were performed using B3LYP method and 6-31+G(d,p) basis set. The favored mechanism and the experimental regioselectivity of this reaction were explained by calculations of activation energy, natural atomic charge, Fukui indexes derived from density functional theory, MM2, and MMFF94 calculations. The current study demonstrated that using the previous computational tools, the regioselectivity of the applied reaction protocol could be correctly predicted.

High-efficiency all-small-molecule organic solar cells based on an organic molecule donor with an asymmetric thieno[2,3-f] benzofuran unit

Two p-type small molecules BDTT-TR and TBFT-TR with benzo[1,2-b′:4,5-b′]dithiophene (BDT) and thieno[2,3-f]benzofuran (TBF) as central core units are synthesized and used as donors in all-small-molecule organic solar cells (all-SMOSCs) with a narrow-bandgap small molecule Y6 (2,2′-((2Z,2′Z)-((12,13-bis(2-ethylhexyl)-3,9-diundecyl-12,13-dihydro-[1,2,5]thiadiazolo [3,4-e]thieno[2″,3’′:4’,5′]thieno[2′,3′: 4,5]pyrrolo[3,2-g]thieno[2′,3′:4,5]thieno[3,2-b]indole-2,10-diyl)bis(methanylylidene))bis (5,6- difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile) as the acceptor. In comparison to BDTT-TR with centrosymmetric BDT as the central unit, TBFT-TR with asymmetric TBF as the central unit shows red-shifted absorption, higher charge-carrier mobility and better charge pathway in blend films. The power conversion efficiency (PCE) of the all-SMOSCs based on TBFT-TR:Y6 reaches 14.03% with a higher short-circuit current density of 24.59 mA cm−2 and a higher fill factor of 72.78% compared to the BDTT-TR:Y6 system. The PCE of 14.03% is among the top efficiencies of all-SMOSCs reported in the literature to date.

Alkoxyphenyl or alkylphenyl side-chained Thieno[2,3-f]benzofuran polymer for efficient non-fullerene solar cells

In this work, two novel thieno[2,3-f]benzofuran (TBF) unit, with fluorinated alkoxyphenyl or alkylphenyl side chain, were synthesized and characterized. Based on these TBF donor unit and benzodithiophene-4,8-dione (BDD) acceptor, two novel polymers, PTBFPF-BDD and PTBFP-BDD, were prepared by Stille coupling reaction. The conjugated side chain effects on the thermogravimetric, optical, electrochemical, and photovoltaic properties of these polymers were systematically investigated. Both polymers exhibited desirable power conversion efficiency (PCE) of more than 8% after thermal annealing. PTBFP-BDD:ITIC-based devices achieved higher PCE of 8.50% with an open-circuit voltage (VOC) of 0.88 V, a short-circuit current density (JSC) of 16.01 mA/cm2 and a fill factor (FF) of 59.80%. In addition, the devices based on PTBFPF-BDD:ITIC showed an enhanced VOC of 0.92 V due to down-shifted the highest occupied molecular orbital (HOMO) energy levels. The results indicate that the alkylphenyl/alkoxyphenyl substitution of TBF donor units is promising strategy for improving PCE of PSCs.

Rhodium-Catalyzed Successive C-H Bond Functionalizations To Synthesize Complex Indenols Bearing a Benzofuran Unit.

An efficient rhodium-catalyzed redox-neutral annulations of N-phenoxyacetamides and ynones via successive double C-H bond activations has been developed. A series of novel and complex indenols bearing a benzofuran unit were generated with moderate to excellent regioselecetivities under mild conditions. Adding N-ethylcyclohexanamine (CyNHEt) could restrict the formation of the mono C-H bond activation byproduct, which is not the intermediate of the reaction demonstrated via the mechanistic investigations.

Bis(benzofurano)pyrrole and hybrid thienopyrrole derivatives for organic thin-film transistors

Abstract To develop new element blocks based on thienopyrroles (DTP) units, bis(benzofurano)pyrrole and hybrid thienopyrrole derivatives were synthesized by Buchwald-Hartwing amination methods. Optical absorption, cyclic voltammetry (CV), single-crystal X-ray diffraction analyses and organic thin-film transistor (OTFT) were employed to investigate the structure-activity relationships of the resulting pyrrole derivatives. It was found that the introduction of a benzofuran unit enhances the planarity and conjugation of heteroacenes leading to strong molecular aggregation and denser π-π stacking, resulting in better charge transport properties with the hole mobility of 0.025 cm2V−1s−1 for the OTFTs.

Isolation, Structural Assignment of Isoselagintamarlin A from Selaginella tamariscina and Its Biomimetic Synthesis

Isoselagintamarlin A (1), a selaginellin analogue featured a rare benzofuran unit, was isolated from Selaginella tamariscina. Its complete structural assignment was established through a combination of high-field NMR technique and biomimetic synthesis. Notably, isoselagintamarlin A (1) was successfully synthesized via sequential oxidations and intramolecular cyclization.Graphical

Synergistic effect of side-chain and backbone engineering in thieno[2,3-f]benzofuran-based conjugated polymers for high performance non-fullerene organic solar cells

A series of copolymers containing thieno[2,3-f]benzofuran unit with different alkyl side chains are synthesized. The best photovoltaic performance with power conversion efficiency over 11% have been realized.

Synthesis and Photovoltaic Properties of a Copolymer based on thieno [2, 3-f] benzofuran and thienopyrroledione

A novel donor-acceptor type conjugated polymer PTBFTPD based on two-dimensional (2D) conjugated alkylthienyl substituted thieno[2,3-f]benzofuran (TBF) and thienopyrroledione (TPD) unit, was synthesized and applied as donor material for bulk heterojunction solar cells. The novol polymer possesses a narrow bandgap of 1.83 eV, a deep HOMO energy level (-5.64 eV) and a closer π−π stacking. After conventional devices were fabricated using PTBFTPD as donor blending with PC70BM as acceptor, a power conversion efficiency (PCE) of 4.33% with a high open circuit voltage (Voc) of 1.09 V was obtained. The result indicates the promising potential of thieno [2, 3-f] benzofuran unit for high efficient polymer solar cells with a high voltage.

Total Synthesis of Unsymmetrical Benzils, Scandione and Calophione A

AbstractThe synthesis of the title unsymmetrical benzils, scandione and calophione A, is described. The key processes involve intramolecular cyclization reaction of the carbanion at the benzylic position of the arylbenzyl ether to the adjacent ester group followed by oxidation. The palladium(II)‐catalyzed oxidative cyclization was also used to establish the benzofuran unit of calophione A.

5-Cyclopentyl-2-(4-methylphenyl)-3-methylsulfinyl-1-benzofuran

In the title compound, C21H22O2S, the cyclo­pentyl ring adopts an envelope conformation with the flap atom connected to the benzofuran residue. The benzofuran unit is essentially planar, with a mean deviation from the least-squares plane defined by the nine constituent ring atoms of 0.008 (2) Å. In the crystal, mol­ecules are linked via pairs of C—H⋯π inter­actions, forming inversion dimers. In the ring of the 4-methyl­phenyl group, four C atoms and their attached H atoms are disordered over two sets of sites, with site-ccupancy factors of 0.899 (5) and 0.10.

Photochromic Composite Properties and Application in Optical Memory of a Diarylethene with Benzofuran Unit

A new photochromic diarylethene, 1-[2-methyl-(5-(4- dioxolane)phenyl)-3-thienyl]-2-(2-methyl-3-benzofuran) perfluorocyclopentene (1o), was synthesized and its photochromic and fluorescent properties were investigated.The product has been characterized by elemental analyses, NMR spectrometry, UV/vis spectrophotometry and Fluorescence spectrophotometry. This diarylethene exhibited reversible photochromism and notable fluorescence photoswitches both in solution and in PMMA films, changing from colorless to pink after irradiation with 297 nm UV light.

Synthesis of a Novel Photochromic Diarylethene for Polarization Optical Recording

A novel unsymmetrical photochromic diarylethene compound bearing a benzofuran unit, 1-[2-methyl-5-formyl-3-thienyl]-2-[2-methyl-3-benzofuran-yl]perfluoroyclopentene(1a) have been synthesized, its photochromic, fluorescence and optical strorage properties were investigated. The compound exhibited obviously photochromism both in hexane and in PMMA film. In hexane, the fluorescence intensity of 1a declined along with the photochromism upon irradiation with 297 nm light. The results showed that the cyclization and cycloreversion process of the compound was determined to be the zeroth/first order reaction. This new photochromic system also exhibited remarkable optical storage character.

Synthesis and Optical Property of an Asymmetric Photochromic Diarylethene Derivative Bearing Benzofuran

A new asymmetric photochromic diarylethene bearing a benzofuran unit was synthesized, namely [1-(2-methyl-3-benzofuranyl)-2-(2-methoxyphenyl)]perfluorocyclopentene (1o). Its photochromic and fluorescent properties were investigated, respectively. The compound exhibited reversible photochromism, changing from colorless to red upon irradiation with UV light both in solution and in PMMA film. The diarylethene exhibited relatively strong fluorescence at 410 nm in hexane solution and 462 nm in PMMA amorphous film when excited at 300 and 385 nm, respectively. The fluorescence intensity decreased along with the photochromism both in hexane and PMMA film upon irradiation with 297 nm light.