Pavel S. Postnikov

Unusually Stable, Versatile, and Pure Arenediazonium Tosylates: Their Preparation, Structures, and Synthetic Applicability

A new, simple, and effective method for the diazotization of a wide range of arylamines has been developed by using a polymer-supported diazotization agent in the presence of p-toluenesulfonic acid. Various pure arenediazonium tosylates with unusual stabilities can be easily prepared by this method. As a result, these salts are useful and versatile substrates for subsequent transformations, such as halogenation and Heck-type reactions. The unusual stabilities of arenediazonium tosylates are also preliminarily discussed with their X-ray structures.

Preparation and X-ray Structural Study of Dibenziodolium Derivatives

New experimental procedures for the preparation of dibenziodolium salts by oxidative cyclization of 2-iodobiphenyl in the presence of appropriate strong acids are described. Particularly useful is a convenient one-pot synthesis of dibenziodolium hydrogen sulfate from 2-iodobiphenyl using Oxone as an inexpensive and environmentally safe oxidant. Dibenziodolium hydrogen sulfate, bis(triflyl)imidate, or triflate can be readily converted to various other dibenziodolium derivatives (chloride, bromide, thiocyanate, azide, cyanide, phenylsulfinate) by anion exchange. Structures of key products have been established by single-crystal X-ray diffraction analysis. Particularly interesting is the X-ray structure of dibenziodolium thiocyanate, which represents the first example of a structurally characterized hypervalent iodine compound with a relatively short iodine-sulfur secondary bond distance.

Matsuda–Heck reaction with arenediazonium tosylates in water

Summary An environmentally friendly Matsuda–Heck reaction with arenediazonium tosylates has been developed for the first time. A range of alkenes was arylated in good to quantitative yields in water. The reaction is significantly accelerated when carried out under microwave heating. The arylation of haloalkylacrylates with diazonium salts has been implemented for the first time.

The convenient preparation of stable aryl-coated zerovalent iron nanoparticles.

Summary A novel approach for the in situ synthesis of zerovalent aryl-coated iron nanoparticles (NPs) based on diazonium salt chemistry is proposed. Surface-modified zerovalent iron NPs (ZVI NPs) were prepared by simple chemical reduction of iron(III) chloride aqueous solution followed by in situ modification using water soluble arenediazonium tosylate. The resulting NPs, with average iron core diameter of 21 nm, were coated with a 10 nm thick organic layer to provide long-term protection in air for the highly reactive zerovalent iron core up to 180 °C. The surface-modified iron NPs possess a high grafting density of the aryl group on the NPs surface of 1.23 mmol/g. FTIR spectroscopy, XRD, HRTEM, TGA/DTA, and elemental analysis were performed in order to characterize the resulting material.

Organic-inorganic hybrid nanoparticles controlled delivery system for anticancer drugs

The use of organic-inorganic hybrid nanocarriers for controlled release of anticancer drugs has been gained a great interest, in particular, to improve the selectivity and efficacy of the drugs. In this study, iron oxide nanoparticles were prepared then surface modified via diazonium chemistry and coated with chitosan, and its derivative chitosan-grafted polylactic acid. The purpose was to increase the stability of the nanoparticles in physiological solution, heighten drug-loading capacity, prolong the release, reduce the initial burst effect and improve in vitro cytotoxicity of the model drug doxorubicin. The materials were characterized by DLS, ζ-potential, SEM, TGA, magnetization curves and release kinetics studies. Results confirmed the spherical shape, the presence of the coat and the advantages of using chitosan, particularly its amphiphilic derivative, as a coating agent, thereby surpassing the qualities of simple iron oxide nanoparticles. The coated nanoparticles exhibited great stability and high encapsulation efficiency for doxorubicin, at over 500μg per mg of carrier. Moreover, the intensity of the initial burst was clearly diminished after coating, hence represents an advantage of using the hybrid system over simple iron oxide nanoparticles. Cytotoxicity studies demonstrate the increase in cytotoxicity of doxorubicin when loaded in nanoparticles, indirectly proving the role played by the carrier and its surface properties in cell uptake.

Preparation, Structure, and Reactivity of Pseudocyclic Benziodoxole Tosylates: New Hypervalent Iodine Oxidants and Electrophiles

New pseudocyclic benziodoxole tosylates were prepared by the treatment of 1-hydroxybenziodoxolones with p-toluenesulfonic acid or via ligand transfer reaction between PhI(OH)OTs (Kosers reagent) and substituted 2-iodobenzoic acids under mild condition. Single crystal X-ray crystallography of these compounds revealed a pseudocyclic structure with a short intramolecular interaction of 2.362 Å between oxygen and iodine in the iodoxole ring. Pseudocyclic benziodoxole tosylates readily react with various organic substrates as electrophiles or oxidants to afford the corresponding iodonium salts or the products of oxidation. Furthermore, these compounds can be used as efficient recyclable hypervalent iodine reagents. The reduced form of a pseudocyclic benziodoxole tosylate, 2-iodobenzoic acid, can be efficiently recovered from the reaction mixture by a simple acid-base liquid-liquid biphasic procedure.

Pseudocyclic Arylbenziodoxaboroles: Efficient Benzyne Precursors Triggered by Water at Room Temperature

New organohypervalent iodine compounds, arylbenziodoxaborole triflates, were prepared from 1-acetoxybenziodoxaboroles and arenes by treatment with trifluoromethanesulfonic acid under mild conditions. Single crystal X-ray crystallography of these compounds revealed a pseudocyclic structure with a short intramolecular interaction of 2.698 to 2.717 Å between oxygen and iodine in the benziodoxaborole ring. These new pseudocyclic aryliodonium salts readily generate aryne intermediates upon treatment with water at room temperature. The generated aryne intermediates react with various substrates to give the corresponding aryne adducts in moderate to good yields. Furthermore, the new benzyne precursors can also work as arylating reagents towards aromatic rings. The aryne intermediates generated from arylbenziodoxaborole triflates selectively react with tert-butyl phenol forming products of ortho arylation in moderate yields.

Synthesis, Characterization, and Antimicrobial Activity of Near-IR Photoactive Functionalized Gold Multibranched Nanoparticles

Abstract Surface‐modified gold multibranched nanoparticles (AuMs) were prepared by simple chemical reduction of gold chloride aqueous solution followed by in situ modification by using water‐soluble arenediazonium tosylates with different functional organic groups. Chemical and morphological structures of the prepared nanoparticles were examined by using transmission electron and scanning electron microscopies. The covalent grafting of organic compounds was confirmed by scanning electron microscopy with energy dispersive X‐ray spectroscopy (SEM‐EDX) and Raman spectroscopy techniques. Covalent functionalization of nanoparticles significantly expands the range of their potential uses under physiological conditions, compared with traditional non‐covalent or thiol‐based approaches. The antibacterial effect of the surface‐modified AuMs was evaluated by using Escherichia coli and Staphylococcus epidermidis bacteria under IR light illumination and without external triggering. Strong plasmon resonance on the AuMs cups leads to significant reduction of the light power needed kill bacteria under the mild conditions of continuous illumination. The effect of the surface‐modified AuMs on the light‐induced antibacterial activities was founded to be dependent on the grafted organic functional groups.

Halon 1301 synthesis by using fluoroxidants

This paper is devoted to the problems of application of alkali and alkaline-earth metal tetrafluorobromates in organic synthesis. The process of Halon 1301 synthesis, which is one of the best fire-extinguishing agents, is considered.

Regioselective Zn(OAc)2-catalyzed azide–alkyne cycloaddition in water: the green click-chemistry

A new method of azide–alkyne cycloaddition (AAC) in the presence of Zn(OAc)2 as an inexpensive and environmentally friendly catalyst in neat water has been developed. The proposed methodology has been applied for the synthesis of 1,4-disubstituted-1,2,3-triazoles from terminal alkynes and 1,4,5-trisubstituted-1,2,3-triazoles from internal alkynes. It has been found that Zn-catalyzed AAC is extremely sensitive to steric hindrance in acetylenes and a method of regioselective triazole ring formation has been proposed. Particularly important is the isolation and characterization of a relatively stable Zn-containing intermediate, which has been characterized by NMR and HRMS.