Chan-Lam Coupling Research Articles

Developing oxygen vacancy-rich CuMn2O4/carbon dots dual-function nanozymes via Chan-Lam coupling reaction for the colorimetric/fluorescent determination of D-penicillamine

Defect engineering is a promising approach to construct high performance nanozymes due to its ability to regulate their physical and chemical properties. However, how to construct defects to improve the activity of nanozymes remains a challenge. Herein, for the first time, the Chan-Lam coupling reaction is used to construct the oxygen vacancy (OV)-rich CuMn2O4/carbon dots (CDs) (OV-CuMn2O4/CDs) dual-function nanozymes with fluorescent (FL) and oxidase-like properties, via regulating the low-valent metal ions (Cu+ and Mn2+) and Ov contents in the spinel CuMn2O4 and in-situ growth of β-cyclodextrin (β-CD)-derived CDs. Expectedly, relative to CuMn2O4, the OV-CuMn2O4/CDs exhibited 35.8%, 8.5%, and 14.6% rise in the contents of Cu+, Mn2+ and Ov, respectively. Abundant Ov provides more O2 adsorption/activation sites, and the charge transfer between Ov and metal atoms increases the charge density around metal atoms. This produces more low-valent metals (like Cu+ and Mn2+) to promote the electron transfer from metal to O atoms and O-O bond cleavage. Thus, the oxidase-like activity of OV-CuMn2O4/CDs is 4.1 times that of CuMn2O4. Also, the in-situ growth of β-CD-derived carbon dots on CuMn2O4 endows OV-CuMn2O4/CDs selective target recognition. Thus, a sensitive and selective colorimetric and fluorescence dual-mode method was established for determining D-penicillamine (D-PA), with the limit of detection of 0.25 and 0.048 μM, respectively. The method was applied to D-PA determination in real samples. This work demonstrates the Chan-Lam coupling reaction can be used to construct high performance nanozymes for developing dual-mode sensor for the detection of targets.

Zn, Cd and Cu Coordination Polymers for Metronidazole Sensing and for Ullmann and Chan-Lam Coupling Reactions.

Five compounds, [Zn2(bpe)(BPTA)2(H2O)2] ⋅ 2H2O (1); [Zn(bpe)(BPTA)] (2); [Cd(bpe)(BPTA)H2O] (3); [Cd(BPTA) (bpmh)] ⋅ 2H2O (4); and Cu2(BPTA)2(bpmh)3(H2O)2] ⋅ 2H2O (5) were prepared employing 2,5-bis(prop-2-yn-1-yloxy)terephthalic acid (2, 5 BPTA) as the primary ligand and 1,2-di(pyridin-4-yl)ethane (4, 4' bpe) (1-3) and 1,2-bis(pyridin-3-ylmethylene)hydrazine (bpmh) (4-5) as the secondary ligands. Single crystal studies indicated that the compounds 1, 3 and 5 have two-dimensional layer structures and compounds 2 and 4 three-dimensional structures. The luminescence behaviour of the compounds 2 and 3 were explored for the sensing of metronidazole in aqueous medium. The studies indicated that the compounds can detect metronidazole in ppm level both in solution as well as simple paper strips. The Cu compound 5 was found to lose the coordinated water molecule at 100 °C without any structural change. The coordinatively unsaturated Cu-centre were examined towards the Lewis acidic character by carrying out the Ullmann type C-C homocoupling reaction of the aromatic halide compounds. The compounds, 4 and 5, also have the Lewis basic functionality arising out the =N-N=, aza groups. The bifunctional nature of the coordination polymers (CP) was explored towards the Chan-Lam coupling reaction between phenyl boronic acid and aniline derivatives in the ethanol medium. In both the catalytic reactions, good yields and recyclability were observed. The present studies illustrated the rich diversity that the transition metal containing compounds exhibit in extended framework structures.

Magnetic Mesoporous Silica Nanocomposite Supported Ionic Liquid/Cu as a Powerful and Highly Stable Catalyst for Chan-Lam Coupling Reaction

Magnetic Mesoporous Silica Nanocomposite Supported Ionic Liquid/Cu as a Powerful and Highly Stable Catalyst for Chan-Lam Coupling Reaction

Magnetically recoverable CuFe2O4 nanocatalyst: Dual catalytic action in sonogashira and Chan-Lam coupling reactions

Magnetically retrievable CuFe2O4 nanocatalyst has been synthesized for Sonogashira (C-C) and Chan-Lam (C-N) coupling reactions by a facile co-precipitation method. Synthesized nanocatalyst was characterized by powder x-ray diffraction (PXRD), fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM) analysis. The catalytic action of the catalyst was evaluated for both Pd-free C-C coupling and base-free C-N coupling reactions where an excellent product yield up to 96 % and 95 % respectively was obtained. The uniqueness of the catalyst was its effective performance under ambient reaction conditions in green solvents such as EtOH and EtOH:H2O (1:1) with a broad substrate scope. The catalyst can be easily retrieved from the reaction mixture with the aid of an external magnet and reused at least five times without significant loss in catalytic activity. The structural stability of the recovered catalyst was confirmed by XRD, FTIR, SEM and ICP-OES (Inductively coupled plasma - optical emission spectrometry) analysis. Thus, the synthesized catalyst works excellently well for dual applications and establishes the sustainable application of the catalyst.

A combined experimental and computational study of ligand-controlled Chan-Lam coupling of sulfenamides

The unique features of the sulfenamides’ S(II)-N bond lead to interesting stereochemical properties and significant industrial functions. Here we present a chemoselective Chan–Lam coupling of sulfenamides to prepare N-arylated sulfenamides. A tridentate pybox ligand governs the chemoselectivity favoring C–N bond formation, and overrides the competitive C-S bond formation by preventing the S,N-bis-chelation of sulfenamides to copper center. The Cu(II)-derived resting state of catalyst is captured by UV-Vis spectra and EPR technique, and the key intermediate is confirmed by the EPR isotope response using 15N-labeled sulfenamide. A computational mechanistic study reveals that N-arylation is both kinetically and thermodynamically favorable, with deprotonation of the sulfenamide nitrogen atom occurring prior to reductive elimination. The origin of ligand-controlled chemoselectivity is explored, with the interaction between the pybox ligand and the sulfenamide substrate controlling the energy of the S-arylation and the corresponding product distribution, in agreement with the EPR studies and kinetic results.

Syntheses and Structure-Activity Relationship Studies of Antitumor Bicyclic Hexapeptide RA-VII Analogues

A series of antitumor bicyclic hexapeptide RA-VII analogues modified at residue 2, 3, or 6 were prepared by the chemical transformation of the hydroxy, methoxy, or carboxy groups or the aromatic rings of natural peptides RA-II, III, V, VII, and X. Analogues with modified side chains or peptide backbones, which cannot be prepared by the chemical transformation of their natural peptides, and newly isolated peptides from Rubia cordifolia roots were synthesized by using protected cycloisodityrosines prepared by the degradation of bis(thioamide) obtained from RA-VII or the diphenyl ether formation of boronodipeptide under the modified Chan-Lam coupling reaction conditions. Studies of the conformational features of the analogues and the newly isolated peptides and their relationships with cytotoxic activities against the HCT-116, HL-60, KATO-III, KB, L1210, MCF-7, and P-388 cell lines revealed the following: the methoxy group at residue 3 is essential for the potent cytotoxic activity; the methyl group at Ala-2 and Ala-4 but not at D-Ala-1 is required to establish the bioactive conformation; the N-methyl group at Tyr-5 is necessary for the peptides to adopt the active conformation preferentially; and the orientation of Tyr-5 and/or Tyr-6 phenyl rings has a significant effect on the cytotoxic activity.

Recent advances in Chan–Lam coupling reaction

Chan–Lam coupling has evolved as a shining star among C–heteroatom coupling reactions because of its greener open flask chemistry and tremendous possibilities in terms of substrate bank, catalyst varieties, unlocking nature friendly conditions, etc.

First atroposelective Chan-Lam coupling for the synthesis of C-N linked biaryls.

The first atroposelective Chan-Lam coupling for the synthesis of C-N axial enantiomers is reported with good yields and ee. MnO2 additive is crucial for the success of the coupling. The longstanding problem of the lack of enantioselective synthesis to make chiral C-N linked atropisomers is solved.

Copper Complexes with N,N,N-Tridentate Quinolinyl Anilido-Imine Ligands: Synthesis and Their Catalytic Application in Chan-Lam Reactions.

The treatment of 2-(ArNC(H))C6H4-HNC9H6N with n-BuLi and the subsequent addition of CuCl2 afforded the anilido-aldimine Cu(II) complexes 1-5 Cu[{2-[ArN=C(H)]C6H4}N(8-C9H6N)]Cl (Ar = 2,6-iPr2C6H3 (1), 2,4,6-(CH3)3C6H2 (2), 4-OCH3C6H4 (3), 4-BrC6H4 (4), 4-ClC6H4 (5)), respectively. All the copper complexes were fully characterized by IR, EPR and HR-MS spectra. The X-ray diffraction analysis reveals that 2 and 4 are mononuclear complexes, and the Cu atom is sitting in a slightly square-planar geometry. These Cu(II) complexes have exhibited excellent catalytic activity in the Chan-Lam coupling reactions of benzimidazole derivatives with arylboronic acids, achieving the highest yields of up to 96%.

Visible-Light-Responsive Nano CuO/ZnO Photocatalyst for Chan–Lam Coupling Reaction and Aerobic C(sp3)–H Bond Oxidation

AbstractWhen it comes to heterogeneous photocatalysts, semiconductors are the best candidate with a high potential to respond in visible-light regions. In this study, semiconductor p-n heterojunction, nano CuO/ZnO, was synthesized via a simple, sustainable, and low-cost approach. Photocatalytic activity of the synthesized material with a 2.02 eV band gap was investigated in the Chan–Lam coupling reaction and C(sp3)–H bond oxidation of alkyl aromatic compounds under visible-light irradiation in aqueous solution. In the case of the Chan–Lam coupling reaction, various derivatives of aniline and arylboronic acid successfully took part in the reaction, delivering the desired products in 57–89% yields. In addition, nano CuO/ZnO photocatalyst showed high efficiency in the C(sp3)–H bond oxidation of alkyl aromatic compounds under air as a green oxidant. Noticeably, the photocatalyst showed high performance in the large-scale synthesis of desired products and maintained activity after several uses.

Gram Scale Synthesis of Membrane-Active Antibacterial 4-Quinolone Lead Compound.

An improved method for the synthesis of a new quinolone class of antibiotics, which are exceptionally potent against gram-positive bacteria, has been developed and the structure confirmed by single-crystal X-ray analysis. In the course of synthesis, using either Chan-Lam coupling or Buchwald-Hartwig amination, we have shown that the careful choice of protecting group at the C4 position of the quinoline is required for selective amination at the C5 position and subsequent deprotection to avoid the formation of a novel pyrido[4,3,2-de]quinazoline tetracycle.

Sulfur-Arylation of Sulfenamides via Chan-Lam Coupling with Boronic Acids: Access to High Oxidation State Sulfur Pharmacophores.

Sulfur-arylation of sulfenamides is reported. This reaction proceeds via a Chan-Lam-type coupling with commercially abundant boronic acids to give sulfilimines. A broad scope was established with a variety of readily accessible aryl and alkyl sulfenamide and boronic acid inputs. Synthetic utility and functional group compatibility were further demonstrated through the direct late-stage introduction of sulfilimines into approved drugs. Derivatization of the sulfilimine products provided access to medicinally relevant sulfoximines and sulfondiimines.

Redox-neutral Chan–Lam coupling of free sulfilimines

Redox-neutral Chan–Lam coupling of free sulfilimines

Efficient recyclable Cu-catalysts for click reaction and Chan-Lam coupling based on copolymers of N-vinylimidazole with N-vinylcaprolactam

A new catalytic system based on copper supported on poly(N-vinylimidazole-co-N-vinylcaprolactam) was investigated. Various compositions of copolymers were checked to compare their influence on the catalytic activity. Copolymer with 25 mol% of N-vinylimidazole and 75 mol% of N-vinylcaprolactam showed the best catalytic efficiency along with its recycling ability in the click reaction and Chan-Lam coupling.

Synthesis of Sulfilimines Enabled by Copper-Catalyzed S-Arylation of Sulfenamides.

Herein, an unprecedented synthetic route to sulfilimines via a copper-catalyzed Chan-Lam-type coupling of sulfenamides is presented. A key to success in this novel transformation is the chemoselective S-arylation of S(II) sulfenamides to form S(IV) sulfilimines, overriding the competitive, and more thermodynamically favored, C-N bond formation that does not require a change in the sulfur oxidation state. Computations reveal that the selectivity arises from a selective transmetallation event where bidentate sulfenamide coordination through the sulfur and oxygen atoms favors the S-arylation pathway. The mild and environmentally benign catalytic conditions enable broad functional group compatibility, allowing a variety of diaryl or alkyl aryl sulfilimines to be efficiently prepared. The Chan-Lam coupling procedure could also tolerate alkenylboronic acids as coupling partners to afford alkenyl aryl sulfilimines, a class of scaffolds that cannot be directly synthesized via conventional imination strategies. The benzoyl-protecting groups could be conveniently removed from the product, which, in turn, could be readily transformed into several S(IV) and S(VI) derivatives.

Synthesis of a chiral dinuclear Cu(II)-benzothiazolamine complex: evidence of cuprophilic interaction in its structure and exploration of its electrochemical properties and catalytic performance.

The synthesis of a chiral dinuclear [Cu(OAc)2(L1)]2 complex (A) and its analogues Cu(OAc)2(L1)2 (B), Cu(OAc)2(L1)PPh3 (C), CuBr(L1)PPh3 (D), and Cu(OAc)2(L2) (E) is described. The X-ray structure of A reveals a cuprophilic interaction (2.65 Å) and shows that L1 behaves as a monodentate ligand. The stereogenic centre in L1 aligns the NH group to form non-covalent interactions with the paddle-wheel acetate groups at variable distances (2.4-2.5 Å and 2.2-2.7 Å). Thermogravimetric analysis confirmed our hypothesis that two equivalents of L1 (B) or a combination of L1 and PPh3 (C) would disrupt the cuprophilic interaction. All complexes, except D, showed irreversible redox waves by cyclic voltammetry. Complexes C and E have lower oxidative peaks (at 10 V s-1) than complex A between +0.40 and +0.60 V. This highlights the influence of ligand(s) on the redox behaviour of Cu(II) complexes. The significance of this electrochemical behaviour was evident in the Chan-Lam (CL) coupling reaction, where 2.5 mol% of A successfully facilitated the formation of a C-N bond. This study showcased the structure, thermal stability, electrochemical properties and catalytic performance of a chiral dinuclear copper(II)-benzothiazolamine complex.

Metal–organic frameworks with open metal sites act as efficient heterogeneous catalysts for Knoevenagel condensation and the Chan–Lam coupling reaction

Two robust metal–organic Frameworks (MOFs) with distinct and diverse network topologies containing open metal sites are successfully employed as heterogeneous catalysts for the Knoevenagel condensation and the Chan–Lam cross coupling reaction.

Study on Cathodic Behaviors of Electrochemical Chan-Lam Coupling between Pyrazoles and Arylboronic Acids

Study on Cathodic Behaviors of Electrochemical Chan-Lam Coupling between Pyrazoles and Arylboronic Acids

One-Pot Synthesis of N-Aryl Tetrahydroquinolines

Key words tetrahydroquinolines - Chan–Lam coupling - reduction - one-pot protocol

Cu(BF4)2/AC-Catalyzed Synthesis of N-Substituted Anilines, N-Substituted 1,6-Naphthyridin-5(6H)-one, and Isoquinolin-1(2H)-one.

Herein, we report practical Cu(BF4)2/activated carbon-catalyzed amination of various anilines, isoquinolinone, and naphthyridinone with aryl boronic acids. The ultrasonic and rotary evaporation treatment of the mixture of aq. Cu(BF4)2 and activated carbon in methanol afforded a novel Cu(II)-catalyst, which is air-stable and can be effectively applied in the Chan-Lam coupling reaction. The products of N-arylation were isolated in good to excellent yields at low catalytic loading. And Cu(BF4)2/AC also showed good reusability.