Coupling Of Derivatives Research Articles

Carboranyl Analogues of Mefenamic Acid and Their Biological Evaluation.

Mefenamic acid represents a widely used nonsteroidal anti-inflammatory drug (NSAID) to treat the pain of postoperative surgery and heavy menstrual bleeding. Like other NSAIDs, mefenamic acid inhibits the synthesis of prostaglandins by nonselectively blocking cyclooxygenase (COX) isoforms COX-1 and COX-2. For the improved selectivity of the drug and, therefore, reduced related side effects, the carborane analogues of mefenamic acid were evaluated. The ortho-, meta-, and para-carborane derivatives were synthesized in three steps: halogenation of the respective cluster, followed by a Pd-catalyzed B–N coupling and hydrolysis of the nitrile derivatives under acidic conditions. The COX inhibitory activity and cytotoxicity for different cancer cell lines revealed that the carborane analogues have stronger antitumor potential compared to their parent organic compound.

Near-infrared piezochromism of AIE-active luminophore in hybridized local and charge-transfer excited state—the effect of shortened donor-acceptor distance

A close-bonded D-A-D′ luminophore BOTPA was designed via direct coupling of secondary arylamine derivatives (D, D′) with benzothiadiazole cyanostilbene group (A). Both near-infrared (NIR) aggregation-induced emission (AIE) and hybridized local and charge-transfer (HLCT) effects, which endow it with highly efficient NIR piezochromic performance, are observed owing to its especially short D-A distance and twisted conformation. The luminophore shows bright fluorescence at 740 nm with an absolute photoluminescence quantum yield (PLQY) as large as 13.2%. Remarkable piezochromism with high sensitivity (11.0 nm•Gpa−1) completely in the NIR region (700–840 nm) could be observed from BOTPA crystals, which is rarely found in piezochromic materials (PCMs). The effects of the shortened D-A distance towards the highly efficient NIR piezochromism are confirmed via single-crystal analysis, in-situ FTIR and theoretical calculations. This work provides a new strategy for the development of high-efficiency NIR PCMs which possess strong penetrating capacity.

Chalcogenacalix[4]dithienoselenophene: Synthesis and Properties of Cyclic Thio- and Selenoether of Dithienoselenophene

Abstract Two kinds of thia- and selenacalix[4]dithienoselenophene, a cyclic dithieno[3,2-b:2′,3′-d]selenophene (DTS) oligomers bridged with divalent chalcogen atoms (S or Se), were successfully prepared via a one-pot cyclization protocol. A palladium-catalyzed coupling of dibromo DTS derivative and (Bu3Sn)2Ch (Ch = S or Se) afforded the cyclic compounds in moderate yield. We have also developed a preparation strategy for the starting DTS derivatives in multi-gram quantity. X-ray analysis revealed that these macrocyclic compounds have different conformations depending on the linker atoms. Thiacalix derivatives form an annular geometry consisting of two sets of vertical and horizontal DTS pairs, while selenacalix derivatives forms a highly symmetrical alternate arrangement of DTS units. The latter macrocycle gave a channel framework to form cavity assembled porous material. Cyclic voltammetry and differential pulse voltammetry measurements for these macrocycles indicated lower redox potentials compared to those of dithienothiophene analogues reported before. Both compounds form a 1:2 complex with C60 in the solid state through face-to-face and S⋯π interactions between DTS and C60. Two guest C60 molecules were captured in the identical space formed by a symmetrical 1,3-alternate conformer.

In situ synthesis of reduction-responsive organogelators via oxidative coupling of tritylthio-terminated gallic acid derivatives

Supramolecular organogels are semi-solid materials that have garnered tremendous interest in the past two decades due to their intriguing responsiveness to external stimuli. However, the construction of supramolecular organogels often involves inconvenient dissolution-enhancement steps such as heating and sonication, which exclude the use of heat or sonication sensitive materials and limit their applications. Herein, two tritylthio-terminated gallic acid (GA) derivatives G1 and G2, which differ subtly in the length and structure of the space that links the GA unit and the trityl thiol and are incapable of gelating organic solvents at room temperature, have been developed as pre-low molecular organic gelators (pre-LMOGs) for in situ gelation at room temperature. G1 or G2 underwent oxidative coupling reaction in the presence of iodine (I2) and turned into LMOGs without the need of a second component, leading to effective in situ gelation. Meanwhile, the in situ generated disulfide bonds confer reduction responsiveness to the formed organogels. A variety of characterizations including UV–vis absorption, transform-infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), nuclear magnetic resonance (NMR) study, scanning electron microscopy (SEM), and theoretical calculation were employed to examine the gelation property and probe into the gelation mechanism. The difference in gelation performance of the pre-LMOGs and the in situ generated LMOGs suggests the importance of molecular flexibility in controlling the gelation behaviors. With the data, it is concluded that the gelation is driven by the collaborative contribution of multiple weak interactions, including van der Waals force, hydrogen bonding, and π stacking interaction.

Double shell structured MnFe2O4 @FeO/C derived from MnFe2O4 @ZIF-8 for electromagnetic wave absorption

The composites formed by the coupling of ferrite and Metal-Organic Framework derivatives have attracted wide attention based on the outstanding microwaves absorption properties. In this paper, MnFe2O4 @ZIF-8 was used as the precursor and was carbonized at 700 °C under Ar atmosphere to obtain MnFe2O4 @FeO/C double shell structure. The carbon-coated composite structure is beneficial to enhance the interfacial polarization on the surface of powder particles and enhance the absorbing properties of the material significantly. Among others, the carbon content is controlled by adjusting the content of coated ZIF-8. The double shell nanoparticle shows excellent reflection loss value of − 53.75 dB at 11.6 GHz with a matching thickness of 1.8 mm, and the corresponding effective absorption bandwidth is 4.74 GHz from 10.27 to 13.90 GHz and 16.89–18.0 GHz.

1-Chloroalumole

A representative of the stable alumoles with a chlorine substituent at the aluminum atom was synthesized by the coupling of a cyclobutadiene dianion derivative and aluminum trichloride. The structure of alumole was established by X-ray crystallography, which showed that alumole exists as a monomer. The aluminum atom is tetracoordinated with the fourth coordination site occupied by a thf molecule, which reduces the intrinsically high Lewis acidity of the aluminum center, thus stabilizing the alumole molecule.

Synthesis of Catechol Thioethers through Gallic Acid/Fe2(SO4)3 Catalyzed Aerobic Oxidative Coupling of Thiols and Catechol Derivatives

AbstractA newly developed cooperative catalytic system Galic acid/Fe2(SO4)3 was employed in the syntheses of catechol thioethers through the direct aerobic oxidative coupling of various thiols with catechol derivatives. As the first organocatalytic oxidative method to prepare catechol thioethers except the enzymatical cases, it exhibits good tolerance and selectivity, leading to the good products in up to 95 % yields. It was postulated to undergo the divergent Michael‐type nucleophilic conjugate addition (1,4‐type or 1,6‐type) of the thiols onto the in‐situ generated ortho‐benzoquinones.

Nickel-Mediated Photoreductive Cross Coupling of Carboxylic Acid Derivatives for Ketone Synthesis.

A simple visible light photochemical, nickel‐catalyzed synthesis of ketones from carboxylic acid‐derived precursors is presented. Hantzsch ester (HE) functions as a cheap, green and strong photoreductant to facilitate radical generation and also engages in the Ni‐catalytic cycle to restore the reactive species. With this dual role, HE allows for the coupling of a large variety of radicals (1°,2°, benzylic, α‐oxy & α‐amino) with aroyl and alkanoyl moieties, a new feature in reactions of this type. With both precursors deriving from abundant carboxylic acids, this protocol is a welcome addition to the organic chemistry toolbox. The reaction proceeds under mild conditions without the need for toxic metal reagents or bases and shows a wide scope, including pharmaceuticals and complex molecular architectures.

Synthesis and evaluation of peptide–fentanyl analogue conjugates as dual µ/δ-opioid receptor agonists for the treatment of pain

Novel peptide-fentanyl analogue conjugates were synthesized by the covalent coupling of carfentanyl derivatives to the C-terminus or N-terminus of the conformationally constrained dermorphin tetrapeptide BVD03 via a chemical linker. The carfentanyl-related analogues displayed distinct binding and functional activities at µ/δ opioid receptors (MOR/DOR) and antinociceptive effects when conjugated to the peptide. The most potent compound, SW-LJ-11, displayed mixed MOR/DOR agonist properties in the low nanomolar range and significant analgesic efficacy in vivo in four classic mouse models of pain. Interestingly, SW-LJ-11 did not exhibit any physical dependence or respiratory depression, in contrast to an equipotent analgesic dose of morphine or BVD03, indicating that the use of opioid peptide–fentanyl analogue conjugates as dual MOR/DOR agonists may be a promising strategy for obtaining safer opioids.

Total Synthesis of Lamellarins G, J, L, and Z Using One-Pot Halogen Dance/Negishi Coupling.

A bottom-up synthesis of lamellarins G, J, L, and Z was achieved via one-pot halogen dance/Negishi coupling of a lithiated dibromopyrrole derivative. The easily accessible dibromopyrrole bearing an ester moiety underwent halogen dance smoothly at -78 °C within 10 min. The resultant α-pyrrolyllithium was transmetalated to the corresponding organozinc species, which was then coupled with an aryl iodide in the presence of catalytic palladium to provide the fully substituted pyrrole. Subsequent halogen-lithium exchange was performed to incorporate a boronate group exclusively at the β position proximal to the ester moiety. This synthetic intermediate allowed stepwise diarylation for the total synthesis of lamellarins G, J, L, and Z.

Visible‐Light Mediated Metal‐Free Cross‐Electrophile Coupling of Isatin Derivatives with Electron‐Poor Alkenes

AbstractA transition metal‐free cross‐electrophile coupling of isatins with acceptor‐substituted alkene has been developed. The reaction operates at room temperature utilizing abundant amine as the terminal reductant under visible light irradiation. A large number of γ‐hydroxy esters and γ‐butyrolactones were synthesized in moderate to good yields tolerating a broad range of functional groups.

Synthesis of Triarylmethanes via Palladium-Catalyzed Suzuki-Miyaura Reactions of Diarylmethyl Esters.

The synthesis of triarylmethanes via Pd-catalyzed Suzuki-Miyaura reactions between diarylmethyl 2,3,4,5,6-pentafluorobenzoates and aryl boronic acids is described. The system operates at mild conditions and has a broad substrate scope, including the coupling of diphenylmethanol derivatives that do not contain extended aromatic substituents. This is significant as these substrates, which result in the types of triarylmethane products that are prevalent in pharmaceuticals, have not previously been compatible with systems for diarylmethyl ester coupling. Further, the reaction can be performed stereospecifically to generate stereo-inverted products. On the basis of DFT calculations, it is proposed that the oxidative addition of the diarylmethyl 2,3,4,5,6-pentafluorobenzoate substrate occurs via an SN2 pathway, which results in the inverted products. Mechanistic studies indicate that oxidative addition of the diarylmethyl 2,3,4,5,6-pentafluorobenzoate substrates to (IPr)Pd(0) results in the selective cleavage of the O-C(benzyl) bond in part because of a stabilizing η3-interaction between the benzyl ligand and Pd. This is in contrast to previously described Pd-catalyzed Suzuki-Miyaura reactions involving phenyl esters, which involve selective cleavage of the C(acyl)-O bond, because there is no stabilizing η3-interaction. It is anticipated that this fundamental knowledge will aid the development of new catalytic systems, which use esters as electrophiles in cross-coupling reactions.

One-pot synthesis of 1,2,4-oxadiazoles from chalcogen amino acid derivatives under microwave irradiation

A series of sulfur- and selenium-bearing, amino acid-derived 1,2,4-oxadiazoles were obtained by a simple procedure. The method consists of EDC-promoted coupling of chalcogen amino acid derivatives with arylamidoximes in acetone, followed by solvent removal and microwave irradiation in water medium. Influence of amidoxime substituents, of the chalcogen atom and of the amino acid side chain is discussed. The results showed this to be a fast, easy and effective method to obtain these compounds, with good functional-group tolerance, potentially favouring future applications in organic synthesis.

BF3-etherate promoted facile access to vinyloxyimidazopyridines: a metal-free sustainable approach.

A convenient and metal-free synthesis of vinyloxyimidazopyridine derivatives has been attained via BF3.OEt2 promoted one-pot multicomponent approach. This procedure involves a facile coupling of 2-aminopyridine derivatives with arylglyoxal and alkyne derivatives. BF3.OEt2 complexation has successfully catalyzed the reaction at room temperature. Utilization of transition metal-free catalyst, mild reaction conditions, easy handling and operational simplicity are key features of developed process.

Nickel-Catalyzed Reductive Vinylation of Chloro-hexahydropyrroloindoline Derivatives with Vinyl Triflates.

This work emphasizes facile construction of C-3a vinyl substituted hexahydropyrrolidinoindolines based upon Ni-catalyzed reductive coupling of chloro-hexahydropyrroloindoline derivatives with a wide range of alkyl-decorated vinyl triflates. The remarkable compatibility of sterically hindered branched vinyl groups is highlighted.

Pressurized SOFC System Fuelled by Biogas: Control Approaches and Degradation Impact

Abstract This paper shows control approaches for managing a pressurized solid oxide fuel cell (SOFC) system fuelled by biogas. This is an advanced solution to integrate the high efficiency benefits of a pressurized SOFC with a renewable source. The operative conditions of these analyses are based on the matching with an emulator rig including a T100 machine for tests in cyber-physical mode. So, this paper presents a real-time model including the fuel cell, the off-gas burner (OFB), and the recirculation lines. Although the microturbine components are planned to be evaluated with the hardware devices, the model includes also the T100 expander for machine control reasons. The simulations shown in this paper regard the assessment of an innovative control tool based on the model predictive control (MPC) technology. This controller and an additional tool based on the coupling of MPC and proportional integral derivative (PID) approaches were assessed against the application of PID controllers. The control targets consider both steady-state and dynamic aspects. Moreover, different control solutions are presented to operate the system during fuel cell degradation. The results include the system response to load variations, and SOFC voltage decrease. Considering the simulations including SOFC degradation, the MPC was able to decrease the thermal stress, but it was not able to compensate the degradation. On the other hand, the tool based on the coupling of the MPC and the PID approaches produced the best results in terms of set-point matching, and SOFC thermal stress containment.

Donor–Acceptor Type Conjugated Microporous Polymer as a Metal-Free Photocatalyst for Visible-Light-Driven Aerobic Oxidative Coupling of Amines

Developing cheap, highly efficient, metal-free heterogeneous photocatalysts remain a great challenge in photoredox reactions. Herein, we utilize a typical Suzuki coupling of low-cost triphenylamine derivative and 9,10-dibromoanthracene to synthesis a donor–acceptor type conjugated microporous polymer (denoted as PAA-CMP). As expected, heterogeneous PAA-CMP exhibits excellent photocatalytic performance, good functional group tolerance and satisfying recyclability in metal-free aerobic oxidative coupling of amines to imines driven by visible light, which is due to its absolute energy level positions and good physicochemical stability. More excitingly, PAA-CMP can enable the gram-scale air-oxidized photocatalytic conversion under natural sunlight irradiation, yielding the desired imine product with an isolated yield of 65% for 48 h. The current work provides a great application prospect for CMPs in low-cost and large-scale organic industrial production in the future. The prepared donor-acceptor (D-A) type conjugated microporous polymer (PAA-CMP) as a metal-free and heterogeneous photocatalyst enable the gram-scale air-oxidized photocatalytic conversion of benzylamine into N-benzylidenebenzylamine under natural sunlight irradiation, yielding the desired imine product with an isolated yield of 65%.

Biaryl Construction Based on Nickel-Catalyzed C–O Bond Activation

AbstractNickel-catalyzed carbon–oxygen bond activation is one of the most powerful strategies for the direct construction of various biaryl compounds. Under nickel catalysis, efficiently produced and naturally abundant arenol-based electrophiles can be activated and coupled with different aryl nucleophiles, including nucleophiles containing magnesium, zinc, boron, etc., to produce biaryl structural units. This Account summarizes recent progress on biaryl synthesis via nickel-catalyzed C–O bond activation.1 Introduction2 Coupling of Arenols and Arenol Derivatives with Aryl Magnesium Reagents3 Coupling of Arenols and Arenol Derivatives with Aryl Zinc Reagents4 Coupling of Arenols and Arenol Derivatives with Aryl Boron Reagents5 Others6 Conclusion

Synthesis of Aryl or Heteroaryl C-Nucleosides by Direct Coupling of a Carbohydrate Moiety with a Preformed Aglycon Unit

C-Nucleosides have similar structure compared to native N-nucleosides, while the carbohydrate unit and the base in a C-nucleoside are connected through a carbon-carbon bond. Because they can also be recognized and utilized by enzymes associated with N-nucleosides in cells, C-nucleosides can inhibit enzyme-catalyzed synthesis or degradation of nucleic acids, thereby inhibiting the proliferation of viruses or cancer cells. C-Nucleoside synthesis has drawn much attention since the clinical application of the C-nucleoside drug remdesivir for the treatment of COVID-19. The direct coupling of a carbohydrate moiety with a preformed aglycon unit is an efficient synthetic approach to construct aryl or heteroaryl C-nucleoside. The synthetic methods of aryl or heteroaryl C-nucleosides in recent years are summarized from three main synthetic strategies: coupling of ribose derivatives with organometallic reagents, transition metal-catalyzed coupling of ribose derivatives with organometallic reagents, and acid-catalyzed Friedel-Crafts reaction of ribose derivatives. Each synthetic strategy is categorized in terms of sugar donor precursors, including hemiacetal riboses, ribonolactones, ribofuranosyl halides, glycal, and others. The mechanism of α or β product formation in these reactions are explained in detail as well. © 2021 Chinese Chemical Society & SIOC, CAS.

One-pot three-component coupling access to 1,2-dihydropyrrolo[1,2-a]pyrazine-1-phosphonates: multi-functionalization of a pyrazine unit.

A new pyrrolo[1,2-a]pyrazine chemical space with a poly-substituted pyrazine unit was readily accessed by Sc(OTf)3-catalyzed one-pot three-component coupling of a pyrrole derivative, amine, and trialkylphosphite under environment-friendly conditions. The formation of multiple bonds (two C-N and one C-P) via a domino process consisting of the chemoselective Kabachnik-Fields reaction and intramolecular cyclodehydration allowed for the construction of highly functionalized pyrazines.