Sonogashira Cross-coupling Research Articles

Triazole-Appended Glycohybrid/CuI-Catalyzed C-C Cross-Coupling of Aryl/Heteroaryl Halides with Alkynyl Sugars.

This report describes a convenient method for the Cu(I)-catalyzed Sonogashira cross-coupling reaction of aryl/heteroaryl halides and alkynyl sugars in the presence of a 1,2,3-triazole-appended glycohybrid as a biocompatible ligand. The Sonogashira cross-coupling products were exclusively formed without the Glaser-Hay homocoupling reaction in the presence of a glycosyl monotriazolyl ligand at 120 °C. However, the Glaser-Hay homocoupling products were obtained at 60-70 °C in the presence of bis-triazolyl-based macrocyclic glycohybrid ligand L8. The glycosyl triazole ligands were synthesized via the CuI/DIPEA-mediated regioselective CuAAC click reaction, and a series of glycohybrids of glucose, mannose, and galactose alkynes including glycosyl rods were developed in good yields. The developed glycohybrids have been well characterized by various spectroscopic techniques, such as nuclear magnetic resonance, high-resolution mass spectrometry, and single-crystal X-ray data of L3. The protocol works well with the heteroaryl and naphthyl halides, and the mechanistic approach leads to CuI/ligand-assisted oxidative coupling. The coupling protocol has notable features, including low catalytic loading, cost-effectiveness, biocompatible nature, and a wide substrate scope.

Purine DNA Constructs Designed to Expand the Genetic Code: Functionalization, Impact of Ionic Forms, and Molecular Recognition of 7-Deazaxanthine-7-Deazapurine-2,6-diamine Base Pairs and Their Purine Counterparts.

Purine DNA represents an alternative pairing system formed by two purines in the base pair with the recognition elements of Watson-Crick DNA. Base functionalization of 7-deaza-2'-deoxyxanthosine with ethynyl and octadiynyl residues led to clickable side chain derivatives with short and long linker arms. As complementary bases, purine-2,6-diamine or 7-deazapurine-2,6-diamine 2'-deoxyribonucleosides were used. 7-Deaza-7-iodo-2'-deoxyxanthosine served as a starting material for Sonogashira cross-coupling and the p-nitrophenylethyl group for base protection. Phosphoramidite building blocks for DNA synthesis were prepared. Oligonucleotides containing single modifications or runs of three purine base pairs embedded in 12-mer Watson-Crick DNA were synthesized and hybridized with complementary strands with purine- or 7-deazapurine-2,6-diamine located opposite to the xanthine derivatives. The stability of base pairs was evaluated in a comparative study on the basis of DNA melting experiments and Tm values. As 7-deazaxanthine and xanthine nucleosides form anionic forms at neutral pH, duplex stability became pK-dependent, and the system with 7-deazapurine displayed a significant higher stability as that containing xanthine. Alkynyl side chains are well accommodated in the purine-purine helix. Click adducts with pyrene showed that short linker arms destabilize duplexes, whereas long linkers increase duplex stability. CD and fluorescence measurements provide further insights into purine-purine base pairing.

Modular Synthesis of Phosphino Hydrazones and Their Use as Ligands in a Palladium-Catalysed Cu-Free Sonogashira Cross-Coupling Reaction.

Invited for this month's cover is the group of Evamarie Hey-Hawkins at Leipzig University. The cover picture shows the three different bonding modes (mono-, bi- and tridentate) of the modular ligand towards palladium(II) or platinum(II), illustrated with Winston who kindly served as the model. The cat has three binding sites (mouth, front paws and hind paws = P, N and pyridine) to bind the metal dichloride fragment. When all three are used in a tridentate bonding mode, one chlorido ligand is cleaved off. Cover design by Dr. Christoph Selg. More information can be found in the Research Article by Evamarie Hey-Hawkins and co-workers.

New Mechanistic Insights into the Copper-Free Heck–Cassar–Sonogashira Cross-Coupling Reaction

New Mechanistic Insights into the Copper-Free Heck–Cassar–Sonogashira Cross-Coupling Reaction

Spin-Labeled Diclofenac: Synthesis and Interaction with Lipid Membranes.

Diclofenac is a non-steroidal anti-inflammatory drug (NSAID) from the group of phenylacetic acid derivatives, which has analgesic, anti-inflammatory and antipyretic properties. The interaction of non-steroidal anti-inflammatory drugs with cell membranes can affect their physicochemical properties, which, in turn, can cause a number of side effects in the use of these drugs. Electron paramagnetic resonance (EPR) spectroscopy could be used to study the interaction of diclofenac with a membrane, if its spin-labeled analogs existed. This paper describes the synthesis of spin-labeled diclofenac (diclofenac-SL), which consists of a simple sequence of transformations such as iodination, esterification, Sonogashira cross-coupling, oxidation and saponification. EPR spectra showed that diclofenac-SL binds to a lipid membrane composed of palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC). 2H electron spin echo spectroscopy (ESEEM) was used to determine the position of the diclofenac-SL relative to the membrane surface. It was established that its average depth of immersion corresponds to the 5th position of the carbon atom in the lipid chain.

Self-aggregation behavior of dimeric chlorophyll-a derivatives linked with ethynylene and m-phenylene moieties.

Chlorophyll(Chl)-a derivatives inserting an ethynylene-m-phenylene group between a zinc chlorin ring and a hydroxymethyl group, in which various substituents were introduced on the benzene spacer, were prepared as model compounds for the light-harvesting antennae (chlorosomes) of photosynthetic green bacteria. These compounds were synthesized from a C3-ethynylated Chl-a derivative via sequential Sonogashira cross-coupling reaction, and the effects of the substituents on the phenylene linker on their self-aggregation behaviors were investigated by electronic absorption, circular dichroism, and infrared absorption spectroscopic measurements. These studies exhibited that some compounds gave the disordered self-assemblies including several species; however, the zinc complex of the dimeric Chl-a derivative primarily allowed a single J-aggregate species in an aqueous Triton X-100 micellar solution. Additional control experiments revealed that its self-assembly was constructed through the hydrogen and coordination bonding involving the hydroxymethyl group on benzene ring, keto-carbonyl group at C13-position, and central zinc atom, and this is consistent with a conventional chlorosomal manner.

Modular Synthesis of Phosphino Hydrazones and Their Use as Ligands in a Palladium-Catalysed Cu-Free Sonogashira Cross-Coupling Reaction.

Phosphino hydrazones represent a versatile class of nitrogen-containing phosphine ligands. Herein, we report a modular synthesis of phosphino hydrazone ligands by hydrazone condensation reaction of three different aryl hydrazines with 3-(diphenylphosphino)propanal (PCHO). Complexation reactions of these phosphino hydrazone ligands with palladium(II) and platinum(II) were investigated and the catalytic activity of the palladium(II) complexes was explored in a Cu-free Sonogashira cross-coupling reaction achieving yields up to 96 %. Additionally it was shown that the catalytically active species is homogeneous.

Catalysis of a Bis-Caffeine Palladium(II) NHC-Pincer Complex

A tridentate bis-NHC Pd complex, based on caffeine, was studied for its catalytic activity. This complex displayed a high catalytic activity in the Suzuki–Miyaura and Mizoroki–Heck cross-coupling reactions of aryl halides. The Sonogashira cross-coupling was also investigated but reveals a fast plateauing of the reaction. Aryl iodides as well as aryl bromides react when equipped with either electron-donating or electron-withdrawing substituents. Aryl chlorides, which contained electron-withdrawing groups, were also reactive under the applied conditions.

Pd/Cu-Catalyzed Synthesis of Internal and Sila-Ynones by Direct Selective Acyl Sonogashira Cross-Coupling of Carboxylic Acids with Terminal Alkynes

The direct acyl Sonogashira cross-coupling of carboxylic acids with terminal alkynes has been achieved through Pd/Cu cooperative catalysis. In this reaction, the readily available carboxylic acids act as the acyl source for the coupling with various terminal alkynes to produce highly valuable ynones in good to high yields. The reaction features high chemoselectivity and functional group tolerance. The reaction offers access to versatile silyl-ynones. The late-stage modification of bioactive molecules and gram-scale experiments highlight the synthetic value of this reaction in organic synthesis. The method enables preparation of ynones directly from carboxylic acids in the absence of C(acyl)–C(sp) decarbonylation.

Excitation Wavelength-Dependent Charge Stabilization in Highly Interacting Phenothiazine Sulfone-Derived Donor–Acceptor Constructs

Prolonging the lifetime of charge-separated states (CSS) is of paramount importance in artificial photosynthetic donor-acceptor (DA) constructs to build the next generation of light-energy-harvesting devices. This becomes especially important when the DA constructs are closely spaced and highly interacting. In the present study, we demonstrate extending the lifetime of the CSS in highly interacting DA constructs by making use of the triplet excited state of the electron donor and with the help of excitation wavelength selectivity. To demonstrate this, π-conjugated phenothiazine sulfone-based push-pull systems, PTS2-PTS6 have been newly designed and synthesized via the Pd-catalyzed Sonogashira cross-coupling followed by [2 + 2] cycloaddition-retroelectrocyclization reactions. Modulation of the spectral and photophysical properties of phenothiazine sulfones (PTZSO2) and terminal phenothiazines (PTZ) was possible by incorporating powerful electron acceptors, 1,1,4,4-tetracyanobutadiene (TCBD) and cyclohexa-2,5-diene-1,4-diylidene-expanded TCBD (exTCBD). The quadrupolar PTS2 displayed solvatochromism, aggregation-induced emission, and mechanochromic behaviors. From the energy calculations, excitation wavelength-dependent charge stabilization was envisioned in PTS2-PTS6, and the subsequent pump-probe spectroscopic studies revealed charge stabilization when the systems were excited at the locally excited peak positions, while such effect was minimal when the samples were excited at wavelengths corresponding to the CT transitions. This work reveals the impact of wavelength selectivity to induce charge separation from the triplet excited state in ultimately prolonging the lifetime of CCS in highly interacting push-pull systems.

Application of Monoferrocenylsumanenes Derived from Sonogashira Cross-Coupling or Click Chemistry Reactions in Highly Sensitive and Selective Cesium Cation Electrochemical Sensors.

This paper reports the synthesis and characterization of novel monoferrocenylsumanenes obtained by means of the Sonogashira cross-coupling or click chemistry reaction as well as their application in cesium cation electrochemical sensors. A new synthetic protocol based on Sonogashira cross-coupling was developed for the synthesis of monoferrocenylsumanene or ethynylsumanene. The click chemistry reaction was introduced to the sumanene chemistry through the synthesis of 1,2,3-triazole containing monoferrocenylsumanene. The designed synthetic methods for the modification of sumanene at the aromatic position proved to be efficient and proceeded under mild conditions. The synthesized sumanene derivatives were characterized by detailed spectroscopic analyses of the synthesized sumanene derivatives. The supramolecular interactions between cesium cations and the synthesized monoferrocenylsumanenes were spectroscopically and electrochemically investigated. Furthermore, the design of the highly selective and sensitive cesium cation fluorescence and electrochemical sensors comprising the synthesized monoferrocenylsumanenes as receptor compounds was analyzed. The tested cesium cation electrochemical sensors showed excellent limit of detection values in the range of 6.0-9.0 nM. In addition, the interactions between the synthesized monoferrocenylsumanenes and cesium cations were highly selective, which was confirmed by emission spectroscopy, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), and cyclic voltammetry.

Sonogashira cross-coupling reaction of aryl fluorosulfates

<p indent="0mm">Aryl fluorosulfates were employed as coupling partners with terminal alkyne or propiolic acid in Sonogashira reaction. The symmetrical diarylalkynes were synthesized <italic>via</italic> decarboxylative cross-coupling of aryl fluorosulfates and propiolic acid in good yields. The unsymmetrical arylalkynes were obtained from aryl fluorosulfates and terminal alkynes or decarboxylative cross-coupling of aryl iodides, aryl fluorosulfates and propiolic acid in one pot with moderate to good yield.

Palladium-Mediated Reductive Heck Cyclization for the Synthesis of Fused Retinoid Derivatives

AbstractLinearly fused retinoid derivatives have been synthesized via a straightforward pathway using a palladium-catalyzed reductive Heck cyclization strategy. The synthesis involved a four-step linear approach utilizing iodination, sulfonylation or benzylation or esterification, palladium-catalyzed Sonogashira cross-coupling and palladium-mediated reductive Heck cyclization.

Synthesis of pyrene-centered D-π-a structured dyes for efficient dye-sensitized solar cells

An asymmetric pyrene derivative was designed as a dye with D-π-A structure. This dye was synthesized by the following steps (acylation reaction, Friedele Crafts acylation reaction, bromination reaction, Hagiharae Sonogashira cross-coupling reaction, and knoevenagel condensation reactions). The structure of the dye was analyzed and identified by FT-IR and 1H-NMR. The dye-sensitized solar cells were prepared with the dye and TiO2 electrode. Futhermore, the I-V curves and IPCE curves of the dye-sensitized solar cells were investigated detailedly. The result showed that the photoelectric conversion efficiency of the dye-sensitized solar cells reached 33.5% of N719 dye cells.

Influence of bridge structure manipulation on the electrochemical performance of π-conjugated molecule-bridged silicon quantum dot nanocomposite anode materials for lithium-ion batteries.

To assess the influence of bridge structure manipulation on the electrochemical performance of π-conjugated molecule-bridged silicon quantum dot (Si QD) nanocomposite (SQNC) anode materials, we prepared two types of SQNCs by Sonogashira cross-coupling and hydrosilylation reactions; one is SQNC-VPEPV, wherein the Si QDs are covalently bonded by vinylene (V)-phenylene (P)-ethynylene (E)-phenylene-vinylene, and the other is SQNC-VPV. By comparing the electrochemical performances of the SQNCs, including that of the previously reported SQNC-VPEPEPV, we found that the SQNC with the highest specific capacity varied depending on the applied current density; SQNC-VPEPV (1420 mA h g-1) > SQNC-VPV (779 mA h g-1) > SQNC-VPEPEPV(465 mA h g-1) at 800 mA g-1, and SQNC-VPV (529 mA h g-1) > SQNC-VPEPEPV (53 mA h g-1) > SQNC-VPEPV (7 mA h g-1) at 2000 mA g-1. To understand this result, we performed EIS and GITT measurements of the SQNCs. In the course of investigating the lithium-ion diffusion coefficient, charge/discharge kinetics, and electrochemical performance of the SQNC anode materials, we found that electronic conductivity is a key parameter for determining the electrochemical performance of the SQNC. Two probable causes for the unique behavior of the electrochemical performances of the SQNCs are anticipated: (i) the SQNC with predominant electronic conductivity is varied depending on the current density applied during the cell operation, and (ii) the degree of surface oxidation of the Si QDs in the SQNCs varies depending on the structures of the surface organic molecules of the Si QDs and the bridging molecules of the SQNCs. Therefore, differences in the amount of oxides (SiO2)/suboxides (SiOx) on the surface of Si QDs lead to significant differences in conductivity and electrochemical performance between the SQNCs.

Solid-Supported Heterogenized Palladium Nanoparticles: Propitious Vehicles for Sonogashira Cross-Coupling Reaction

Abstract

A Convenient, Efficient, and Inexpensive Copper(I) Complex Catalyzed Sonogashira Cross-Coupling of o-Iodoanilines with Terminal Alkynes

AbstractUsing (PPh3)2CuBH4 as catalyst, a convenient, efficient, and inexpensive palladium-free catalytic system has been developed to catalyze Sonogashira cross-coupling of o-iodoanilines with terminal alkynes under an air atmosphere to give a range of 2-ethynylaniline derivatives with up to 99% yield. This protocol is amenable to scale up. Notable features of the approach include good functional group tolerance, air atmosphere, and excellent yields.

Effect of oligothiophene spacer length on photogenerated charge transfer from perylene diimide to boron-doped diamond electrodes

Organic-based photovoltaic devices emerged as a complementary technology to silicon solar cells with specific advantages in terms of cost, ease of deployment, semi-transparency, and performance under low and diffuse light conditions. In this work, thin-film boron-doped diamond (B:NCD) electrodes are employed for their useful optical, electronic, and chemical properties, as well as stability and environmental safety. A set of oligothiophene perylene diimide (nT-PDI) donor-acceptor chromophores is designed and synthesized in order to investigate the influence of the oligothiophene spacer length when the nT-PDI molecule is attached to a B:NCD electrode. The chromophores are anchored to the diamond surface via diazonium grafting followed by Sonogashira cross-coupling. X-ray photoelectron spectroscopy shows that the surface coverage decreases with increasing oligothiophene length. Density functional theory (DFT/TDDFT) calculations reveal the upright nT-PDI orientation and the most efficient photogenerated charge separation and injection to diamond for elongated oligothiophene chains (8T-PDI). Yet, the maximum photovoltage is obtained for an intermediate oligothiophene length (3T-PDI), providing an optimum between decreasing transport efficiency and increasing efficiency of charge separation and reduced recombination with increasing oligothiophene length. Holes transferred from nT-PDI to diamond persist there even after the illumination is switched off. Such features may be beneficial for application in solar cells. • Variable donor-acceptor chromophore/diamond system designed in-silico and fabricated. • Oligothiophene donor length adjusts valence band and charge transport with diamond. • Intermediate oligothiophene length (3 units) yields the maximum photovoltage. • Up to 0.87 electron per molecule transferred to diamond across 44 Å under excitation.

Cu-Ce Bimetallic Metal-Organic Framework-Derived, Oxygen Vacancy-Boosted Visible Light-Active Cu2O-CeO2/C Heterojunction: An Efficient Photocatalyst for the Sonogashira Coupling Reaction.

The development of an economical transition metal-based catalyst for photocatalytic carbon-carbon coupling reactions is aspiring. Herein, a Cu-Ce metal-organic framework (MOF) was synthesized and carbonized to produce bimetallic Cu2O-CeO2/C, which was utilized in the Sonogashira cross-coupling reaction. The defects and oxygen vacancies in the catalyst were characterized by X-ray photoelectron spectroscopy and Raman spectroscopy, while the nature of Cu was characterized by H2-TPR analysis. The defect-induced MOF-derived Cu-Ce heterojunction created more oxygen vacancies (OV) in CeO2, revealing the high photocatalytic activity. The Cu-Ce heterojunction (Cu2O-CeO2/C) formed a Cu(I)-phenylacetylide active complex and exhibited higher catalytic activity for the visible light-induced Sonogashira cross-coupling reaction. 25%Cu2O-CeO2/C offered 93.8% phenylacetylene conversion with a 94.2% Sonogashira product selectivity by using household light-emitting diodes. No discernible activity loss was observed from the recycling of the catalyst. Based on catalytic activity, control reactions, and physicochemical and optoelectronic characterization, the structure-activity relationship was established and a reaction mechanism was proposed. Replacement of the costly Pd metal-based catalyst with a cheap Cu2O-CeO2-based catalyst for the synthesis of commercially important compounds with a sustainable visible light-induced catalytic process will be highly attractive to chemists and industrialists.

Efficient Synthesis of Fluorescent Coumarins and Phosphorous-Containing Coumarin-Type Heterocycles via Palladium Catalyzed Cross-Coupling Reactions.

Quantum-chemical calculations on the spectral properties of some aryl substituted 3-phosphonocoumarins were performed, and the effect of the substituents in the aryl moiety was evaluated. The structures possessing promising fluorescent properties were successfully synthesized via Suzuki and Sonogashira cross-coupling. The synthetic protocol was also applied for the phosphorous chemoisomer of 3-phosphonocoumarin, 1,2-benzoxaphosphorin, and their carboxylate analogues. The optical properties of the arylated and alkynylated products were experimentally determined. The obtained quantum-chemical and experimental results give the possibility for a fine tuning of the optical properties of phosphorous-containing coumarin systems by altering the substituent at its C-6 position.