Preparation of aryl azides of aryl boronic acids and one-pot synthesis of 1,4-diaryl-1,2,3-triazoles by a magnetic cysteine functionalized GO–CuI/II nanocomposite

A mixed Cu^I/Cu^IIcatalyst based on magnetic cysteine functionalized graphene oxide (Cu^I/II@Cys-MGO) was prepared and used for the azidonation reaction of aryl boronic acids and one-pot synthesis of 1,4-diaryl −1,2,3-triazoles. Aryl azides were obtained in good yields and short reaction times via cross-coupling of aryl boronic acids with sodium azide in the presence of Cu^II catalytic species in this catalytic system. The azide-alkyne cycloaddition reaction was catalyzed by CuI catalytic species in Cu^I/^II@Cys-MGO nanocomposite.     

Orthogonal multiple click reactions in synthetic polymer chemistry

This review highlights the concept of multiple click reaction strategy which is utilized for design and synthesis of well‐defined complex macromolecular structures as well as multifunctionalization of well‐defined polymers. This review examines the click combinations mainly from double to quadruple and additionally from the most frequently used to the least. The present review may also be regarded as an update for recent reviews dealing with specifically double and triple click reaction combinations in synthetic polymer chemistry. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3147–3165     

Alkyne–azide cycloaddition catalyzed by a dinuclear copper(I) complex

A novel dinuclear copper complex Cu^I₂(pip)₂ was used as a catalyst for alkyne–azide cycloaddition (CuAAC) reaction. High yields (95–99%) were obtained for various substrates at a low loading of 0.2 mol %. The unique structure, high stability of the dinuclear structure in solution, and easy preparation make this complex not only a high-efficiency catalyst but also a model for understanding the mechanism of the CuAAC reaction.     

Click Chemistry Mediated Functionalization of Vertical Nanowires for Biological Applications

Semiconductor nanowires (NWs) are gaining significant importance in various biological applications, such as biosensing and drug delivery. Efficient and controlled immobilization of biomolecules on the NW surface is crucial for many of these applications. Here, we present for the first time the use of the Cu^I‐catalyzed alkyne–azide cycloaddition and its strain‐promoted variant for the covalent functionalization of vertical NWs with peptides and proteins. The potential of the approach was demonstrated in two complementary applications of measuring enzyme activity and protein binding, which is of general interest for biological studies. The attachment of a peptide substrate provided NW arrays for the detection of protease activity. In addition, green fluorescent protein was immobilized in a site‐specific manner and recognized by antibody binding to demonstrate the proof‐of‐concept for the use of covalently modified NWs for diagnostic purposes using minute amounts of material.     

A New Approach for Synthesis of Low‐moisture Glycidyl Azide Polymer

In this work, low‐moisture glycidyl azide polymer (GAP) was successfully prepared using a modified two‐step method. The modified method resembles the structure of the classical two‐step method, which is widely used to prepare the GAP. Firstly, epichlorohydrin (ECH) is polymerized into polyepicholorohydrin (PECH), which is subjected afterward to azidation step using sodium azide (NaN₃). Interestingly, minimizing the water content in the final GAP product, which is a challenging when dealing with GAP as a rocket propellant binder, was effectively achieved by utilizing low boiling point solvents instead of the relatively high boiling point Dimethyl formamide (DMF), monitoring the volatility of ECH and controlling the exothermicity of the reaction. Prepared GAP samples were investigated using Fourier transformer infra‐red (FT‐IR), gel‐permeation chromatography (GPC) and elemental analysis apparatus (CHNS) were used to characterize the product. The moisture % in the final product was examined using the Karl‐Fisher Technique. Results showed the successful preparation of GAP with low water content (<0.01 %), high average molecular weight (> 2000 g · mol^–1), 42.82 % nitrogen, a viscosity of 3484 cP at 20 °C, yield ranges between 95–98 % and a polydispersity index of 1.2. The prepared GAP is promising for replacement of the classical GAPs in the energetic materials applications.     

Microwave-Assisted Azide-Alkyne Cycloaddition in Water Using a Heterogeneous Cu-Catalyst

Several triazoles have been synthesized. They were obtained by a Cu-catalyzed cycloaddition of azides and alkynes. The reaction takes place in aqueous media under microwave irradiation using a copper catalyst based on porous glass. The products have been characterized by infrared, gas chromatography–mass spectrometry, ¹H NMR, and ¹³C NMR in addition to melting = point determination. Furthermore the in situ building of some azides and alkynes and the influence of the used metal species was investigated.     

Surface functionalization of multiwalled carbon nanotubes by the photo‐responsive strategy of π‐π stacking and azide‐grafting

In this communication, we report a new, simple, and eco‐friendly method to develop highly dispersible multiwalled carbon nanotubes (MWCNTs) by π‐π stacking and azide‐grafting. MWCNTs were functionalized via standard physisorption, followed by nitrene addition using azido compounds upon ultraviolet activation. The functionalized MWCNTs show excellent dispersibility without raising distinct damage, which can bear comparison with that of MWCNTs oxidized with mixture acids. This method allows for the improvement of the chemical compatibility of MWCNTs with specific polymers for application in nanotube‐based composites and opens a potential pathway for surface protection.     

Spectroscopy on photografted polyethylene surfaces using a perfluorophenyl azide: Evidence for covalent attachment

The present study was conducted in order to confirm C―H insertion of a perfluorophenyl nitrene, produced by UV‐irradiation of a perfluorophenyl azide, to polyethylene surfaces. It was shown previously that water‐repelling, oil‐repelling, and dirt‐repelling polyethylene surfaces can be created by “grafting to” of perfluoroalkanes using a photoreactive surface modifier based on azide/nitrene chemistry. The abrasion resistance of the new surfaces was enhanced compared with a coating using a simple, long‐chain perfluoroalkane. However, covalent binding of the surface modifier was not unequivocally demonstrated. Here, spectroscopic information is presented suggesting that, indeed, a monomolecular, covalently bound grafted layer is formed from the photodecomposition of a perfluorophenyl azide on polyethylene surfaces. Infrared spectroscopy showed that the peak from the azide moiety disappeared upon UV‐irradiation, and the light dose for completion of the photo decomposition was determined to be approximately 322 mJ/cm². A model compound mimicking the grafted nitrene species was synthesized, having a λ_max of 281 nm in hexane. The photografted and washed layer had a λ_max of 286 nm, indicating a good conformity with the model compound. X‐ray photoelectron spectroscopy of the nitrogen species from the photografted layer showed a peak at 400.0 eV. The model compound had a N 1s binding energy of 399.7 eV, thus being comparable.     

Application of image analysis technique for the determination of thiophanate methyl by thin-layer chromatography

A simple and convenient thin-layer chromatography (TLC) method combined with image analysis technique was developed to determine thiophanate methyl. The detection of pesticide was based on iodine–azide reaction. Digital images of TLC plate chromatograms were analysed using TLSee software, and quantitative analysis was conducted. The linearity (0.3–3.0 µg per spot), sensitivity, accuracy and precision of the system were investigated.     

Photochemistry of 7-azide-1-ethyl-3-carboxylate-6,8-difluoroquinolone: a novel reagent for photoaffinity labeling

A novel reagent for photoaffinity labeling, 7-azido-1-ethyl-3-carboxylate-6,8-difluoroquinolone, was obtained by nucleophilic substitution of 1-ethyl-3-carboxylate-6,7,8-trifluoroquinolone. Photochemical reaction of this azide with diethyl amine gave 7-hydrazino-derivative as the major product. This compound was generated by singlet nitrene N-H insertion. In addition, 7-amino-1-ethyl-3-carboxylate-6,8-difluoroquinolone was also obtained.