Covalent Grafting of BPin functions on Carbon Nanotubes and Chan–Lam–Evans Post-Functionalization

The chemical functionalization of carbon nanotubes is often a prerequisite prior to their use in various applications. The covalent grafting of 4,4,5,5-tetramethyl-1,3,2-dioxaborolane (BPin) functional groups directly on the surface of multi- and single-walled carbon nanotubes, activated by nucleophilic addition of nBuLi, was carried out. Thermogravimetric analysis (TGA) coupled with mass spectrometry, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ions mass spectrometry (ToF-SIMS) confirmed the efficiency of this methodology and proved the integrity and covalent grafting of the BPin functional groups. These groups were further reacted with various nucleophiles in the presence of a copper(II) source in the conditions of the aerobic Chan–Lam–Evans coupling. The resulting materials were characterized by TGA, XPS and ToF-SIMS. This route is efficient, reliable and among the scarce reactions that enable the direct grafting of heteroatoms at carbonaceous material surfaces.     

Functionalization of silica surface using Chan–Lam coupling

The reaction of base-free Chan–Lam coupling was successfully used for functionalization of surface of mesoporous silica gel. Various aromatic, aliphatic, and heterocyclic compounds were immobilized by a copper-catalyzed reaction of corresponding boronic acids with surface amino groups at mild conditions. Obtained functionalized materials were mesoporous although their surface area decreased after immobilization. The reactivity of some surface functional groups was tested in their characteristic reactions.     

Chan–Lam coupling reactions: synthesis of heterocycles

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Chan–Lam coupling reactions and their applications on the synthesis of a number of differently functionalized heterocycles are reviewed. This report contains 125 references.     

Copper(I) 3-Methylsalicylate Mediates the Chan–Lam N-Arylation of Heterocycles

Copper(I) 3-methylsalicylate (CuMeSal) mediates N-arylation reactions between aryl boronic acids and aromatic heterocycles (Chan–Lam coupling) under moderate reaction conditions (K₂CO₃, methanol, 65 °C, in air, 3–5 h). Both electron-rich and electron-deficient aryl boronic acids and a diverse set of N-heterocycles were allowed to react and gave N-arylation products in reasonable yields, which demonstrate the utility of this catalyst.     

First example of axial selectivity in the nucleophilic addition to (−)-menthone—addition of cyanomethyl lithium

The addition of cyanomethyl lithium to (−)-menthone at −78°C followed by 1.5 h stirring at room temperature and acidic workup produced exclusively the axial addition product, being the first example of preferred axial attack of an organometallic reagent to menthone. In the case of hydrolysis at −78°C after 0.5 h reaction time the equatorial addition product was isolated as the preferably formed isomer. The axial and equatorial cyanomethyl substituted menthol and neomenthol, respectively, were isolated in high yields.     

First example of the coupling of α-diazoketones with thiourea: a novel route for the synthesis of 2-aminothiazoles

α-Diazoketones undergo smooth coupling with thiourea in the presence of 10 mol % of copper(II) triflate to produce the corresponding 2-aminothiazoles in excellent yields with high selectivity. The use of copper(II) triflate makes this method simple, convenient and practical. This method works well with both aryl and alkyl diazoketones to furnish a wide range of 2-aminothiazoles.     

Homolytic displacement at carbon: First example of α-attack in the allenyl and propargyl cobaloximes

The reactions of allenyl and propargyl cobaloximes with organosulphonyl chlorides under anaerobic and photochemical conditions form sulphones by a novel homolytic attack at the α carbon to the metal.     

Fabrication of nitrogen-enriched graphene oxide/Cu NPs as a highly efficient and recyclable heterogeneous nanocatalyst for the Chan–Lam cross-coupling reaction

Herein, we demonstrate the direct polymerization of melamine and cyanuric chloride in the surface of graphene oxide (GO) (N-enriched GO) in order to develop a new nanocatalyst. The supramolecular polymerized GO acts not only as a spacer to prevent the restacking of graphene sheets but also as a nitrogen source to generate active centers for Cu NP attachments. Subsequently, the nitrogen on the surface of the GO sheets coordinates with copper ions to generate copper nanoparticles. The prepared nanocatalyst was characterized by Fourier transform infrared spectroscopy, X-ray powder diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy and thermogravimetric analysis. This catalyst showed high efficiency and good activity in the Chan–Lam cross-coupling reaction of N-heterocycles and aniline derivatives with high yields in short reaction times. In addition, the nanocatalyst was easily recovered and reused for five consecutive runs without any noticeable loss of performance.     

First Discovery of the Earliest Angiospermous Megafossils in the World

The first discovery of the earliest angiospermous megafossils, so far in the world,was made by the authors from the Lower Cretaceous Chengzihe Formation of Jixi Basin, eastern Heilongjiang Province,China.Among the angiospermous fossils there are 5 species belonging to 5 genera (including 4 gen.et sp.nov.) reported in this paper.Their microphyllous leaves with irregular venations show the characteristics of some primitive angiosperms whose age is mostly corresponding to the late Hauterivian-early Barremian, partly proved by the underlying conformably marine beds with the Valanginian-Hauterivian dinoflagellates revealed newly also by the authors.     

First example of the formation of bipolar spiro σ-complexes from 6-bromo-5,7-dinitrobenzo[e]-1,2,3,4-tetrazine 1,3-di-N-oxide

The reactions of 3,5,7-trimethyltropolone and 2-(N-benzylamino)tropone with 6-bromo-5,7-dinitrobenzo[e]-1,2,3,4-tetrazine 1,3-di-N-oxide afforded novel bipolar spiro -complexes. The kinetic and activation parameters of the R,S-enantiotopomerization of a chiral spiro -complex of 2-(N-benzylamino)tropone were determined using dynamic ¹H NMR spectroscopy.     

Cu(OAc)2 promoted Chan–Evans–Lam C–N cross coupling reactions on the N- and N′-nitrogen atoms of sulfonimidamides with aryl boronic acids

We report a highly efficient and mild protocol for Chan–Evans–Lam C–N cross coupling of sulfonimidamides and aryl boronic acids using Cu(OAc)₂ as mediator, triethylamine (TEA) as base and acetonitrile as solvent. The reaction proceeds at room temperature and provides high to excellent yields for a variety of boronic acids, allowing N-arylation of both N-protected (N-amine nitrogen) and N-deprotected (N′-imine nitrogen) sulfonimidamides.     

Intercalation of copper salt to montmorillonite K-10 and its application as a reusable catalyst for Chan–Lam cross-coupling reaction

A simple and efficient catalytic system has been developed by adsorption of copper salt in the interlayers of montmorillonite K-10. The catalytic system impressively exercises the green chemistry perspective leading to effortless recovery and recyclability for the cross-coupling of arylboronic acids and N-nucleophiles. The effect of catalytic activity was studied for electronically diverse arylboronic acids and imidazoles relying on various optimizations under optimum thermal condition. The catalytic system was characterized and the morphology was determined.     

New α-glucosidase inhibiting anthracenone from the barks of Harungana madagascariensis Lam

Two new 10-hydroxy-9(10H)-anthracenone, madagascenone A (1) and B (2), were isolated from the barks of Harungana madagascariensis Lam. The structures of the compounds were determined using 1D- and 2D-NMR and mass spectroscopic techniques. Both of the compounds showed an in vitro α-glucosidase inhibition with IC₅₀ = 69.9 ± 4.21 and 122.3 ± 1.13 μM, respectively, more potent than the standard acarbose (IC₅₀ = 840 ± 1.23 μM).     

First example of the synthesis of N-vinylpyrrole from methoxy- allene and methoxyethyl isothio- cyanate: unprecedented elimination of methanol from a β-substituted methyl ethyl ether

Using as example 3-methoxy-1-(2-methoxyethyl)-2-methylsulfanylpyrrole, obtained in one preparative stage from α-lithiated methoxyallene and 2-methoxyethyl isothiocyanate, a facile cleavage of a C–O bond in the N-(2-methoxyethyl) substituent by the t-BuOK–DMSO system has been discovered, opening access to a new class of N-vinylpyrroles (through β-elimination of methanol).     

First Synthesis of 2α—Thiol Ether Analog of Docetaxel

A 2α-phenylthio ether analog 1c of docetaxel was synthesized for the first time from 10-deacetylbaccatin Ⅲ 3 via double inversion of C-2 configuration. This compound showed very weak cytotoxicity toward several tumor cell lines.     

First example of a silica gel-supported optically active Mn(III)–salen complex as a heterogeneous asymmetric catalyst in the epoxidation of olefins

An optically active Mn(III)–salen complex was supported on silica gel materials: the insoluble systems obtained were employed as catalysts in the asymmetric epoxidation of some aromatic olefins. Enantiomeric excess values up to 58% were obtained.