Reductive carbodiazenylation of nonactivated olefins via aryl diazonium salts

[Structure: see text] The reduction of aryl diazonium salts in the presence of nonactivated olefins provides rapid entry to carbodiazenylation products. The regioselective functionalization of double bonds is achieved in a one-pot process starting from aniline derivatives. Carboamination of olefins is possible via a two-step carbodiazenylation-hydrogenation sequence in which one aniline equivalent is recovered.     

The copper-catalyzed cross-coupling reactions of aryl diazonium salts and isocyanides

The copper-catalyzed cross-coupling reaction of aryl diazonium salts and isocyanides has been performed. This is a successful example of preparation of arylcarboxyamides with moderate to good yield under mild conditions.     

Intermolecular radical carboaminohydroxylation of olefins with aryl diazonium salts and TEMPO

Highly reactive aryl radicals can selectively be reacted with a broad variety of activated and nonactivated olefinic substrates in the presence of nitroxyl radicals. Direct recombination of the aryl radical and the nitroxide as well as telomerization of the olefin is successfully suppressed by the reaction conditions.     

Arylations using diazonium tetrafluoroborate and pyridine A convenient source of aryl radicals

Benzenediazonium tetrafluoroborate together with one equivalent of pyridine provides a convenient source of phenyl radicals via the homolysis of N-phenylazopyridinium tetrafluoroborate. Partial rate factors and total rate ratios have been determined for attack of a number of aromatic substrates by phenyl radicals produced in this way and are found to be similar to the values obtained using benzoyl peroxide as the source of phenyl radicals. The ratios of isomers formed in the decompositions in moderate and in large excesses of pyridine differ from one another. The results are discussed.     

Metal-free, visible-light-mediated direct C-H arylation of heteroarenes with aryl diazonium salts

Visible light along with 1 mol % eosin Y catalyzes the direct C-H bond arylation of heteroarenes with aryl diazonium salts by a photoredox process. We have investigated the scope of the reaction for several aryl diazonium salts and heteroarenes. The general and easy procedure provides a transition-metal-free alternative for the formation of aryl-heteroaryl bonds.     

Hydroperoxides and aryl diazonium salts as reagents for the functionalization of non-activated olefins

Hydroperoxides, olefins, and arenediazonium salts selectively combine to give azo compounds via an iron(II)-mediated three-component reaction. Starting with a fragmentation liberating acetic acid, the hydroperoxides act as radical source and the diazonium ions as nitrogen-centered radical scavengers.     

Addition of aryl radicals generated from electrochemical reduction of aryl halides on carbon-carbon double bonds.

Aryl radicals generated by electrochemical reduction of aryl halides in aprotic medium react with styrene and its derivatives to give arylated addition compounds.     

Maleimide-activated aryl diazonium salts for electrode surface functionalization with biological and redox-active molecules

A versatile and simple method is introduced for formation of maleimide-functionalized surfaces using maleimide-activated aryl diazonium salts. We show for the first time electrodeposition of N-(4-diazophenyl)maleimide tetrafluoroborate on gold and carbon electrodes which was characterized via voltammetry, grazing angle FTIR, and ellipsometry. Electrodeposition conditions were used to control film thickness and yielded submonolayer-to-multilayer grafting. The resulting phenylmaleimide surfaces served as effective coupling agents for electrode functionalization with ferrocene and the redox-active protein cytochrome c. The utility of phenylmaleimide diazonium toward formation of a diazonium-activated conjugate, followed by direct electrodeposition of the diazonium-modified DNA onto the electrode surface, was also demonstrated. Effective electron transfer was obtained between immobilized molecules and the electrodes. This novel application of N-phenylmaleimide diazonium may facilitate the development of bioelectronic devices including biofuel cells, biosensors, and DNA and protein microarrays.     

Role of adsorbed surfactant in the reaction of aryl diazonium salts with single-walled carbon nanotubes

Because covalent chemistry can diminish the optical and electronic properties of single-walled carbon nanotubes (SWCNTs), there is significant interest in developing methods of controllably functionalizing the nanotube sidewall. To date, most attempts at obtaining such control have focused on reaction stoichiometry or strength of oxidative treatment. Here, we examine the role of surfactants in the chemical modification of single-walled carbon nanotubes with aryl diazonium salts. The adsorbed surfactant layer is shown to affect the diazonium derivatization of carbon nanotubes in several ways, including electrostatic attraction or repulsion, steric exclusion, and direct chemical modification of the diazonium reactant. Electrostatic effects are most pronounced in the cases of anionic sodium dodecyl sulfate and cationic cetyltrimethylammonium bromide, where differences in surfactant charge can significantly affect the ability of the diazonium ion to access the SWCNT surface. For bile salt surfactants, with the exception of sodium cholate, we find that the surfactant wraps tightly enough such that exclusion effects are dominant. Here, sodium taurocholate exhibits almost no reactivity under the explored reaction conditions, while for sodium deoxycholate and sodium taurodeoxycholate, we show that the greatest extent of reaction is observed among a small population of nanotube species, with diameters between 0.88 and 0.92 nm. The anomalous reaction of nanotubes in this diameter range seems to imply that the surfactant is less effective at coating these species, resulting in a reduced surface coverage on the nanotube. Contrary to the other bile salts studied, sodium cholate enables high selectivity toward metallic species and small band gap semiconductors, which is attributed to surfactant-diazonium coupling to form highly reactive diazoesters. Further, it is found that the rigidity of anionic surfactants can significantly influence the ability of the surfactant layer to stabilize the diazonium ion near the nanotube surface. Such Coulombic and surfactant packing effects offer promise toward employing surfactants to controllably functionalize carbon nanotubes.     

Direct electroreductive preparation of indolines and indoles from diazonium salts

[reaction: see text] Indolines and indoles are prepared for the first time by direct electrochemical reduction of arenediazonium salts.     

Reaction of 3-oxodihydrothionaphthenes with aryl diazonium chlorides and aryl isothiocyanates

The reaction of 3-oxodihydrothionaphthenes with aryl diazonium chlorides gives 2-arylhydrazono-3-oxodihydrothionaphthenes. By oxidation of the latter with hydrogen peroxide in glacial acetic add, new 2-arylhydrazonodihydrothionaphthene-(3)-one-1, 1-dioxides are synthesized. Condensation of aryl isothiocyanates with 3-oxodihydrothionaphthenes in tetrahydrofuran gives 2-(arylthiocarbamyl)-3-oxodihydrothionaphthenes; cyclization of the latter with -bromoacetophene leads to the synthesis of 4-phenyl-3-aryl-2-(3 -oxodihydrothionaphthylidene-2)-⁴-thiazolines.     

Highly efficient synthesis and application of aryl diazonium salts via femtosecond laser-tailored 3D flow microfluidic chips

The first example of the microfluidic chips (MFCs) consisting of centimeter-level 3D channels with high-density and large-volume fabricated by femtosecond laser micromachining were utilized to develop a time-saving, economical and hazardless flow synthesis process, and its advantages have been proved by in situ formation of aryldiazonium salts and subsequent borylation with bis(pinacolato)diboron. There are several important advantages in our 3D MFC-based flow synthesis technology, including the following: (1) the reaction temperature was altered from ice bath to room temperature; (2) the residence time was reduced by 10 times; (3) the yield was greatly improved, that is, several arylboronates were successfully obtained with higher yield compared to traditional batch process. Therefore, it can be envisioned that a novel, simplified flow synthetic protocol will be developed toward green organic synthesis via MFCs.     

UiO-66 microcrystals catalyzed direct arylation of enol acetates and heteroarenes with aryl diazonium salts in water

UiO-66 is a classic Metal–organic framework (MOF) that constructed by zirconium cations and terephthalate with high chemical and thermal stability. Using pristine UiO-66 nanocrystals as the catalysts, the carbon–carbon bond formation based on denitrogenative substitution of aryl diazonium salts has been achieved under mild condition. The C–H arylation of both enol acetates and heteroarenes could be performed in aqueous medium without other metal assistance. The UiO-66 catalyst shows good water stability and reusability as well as impressive functional group tolerance.     

Preparation and characterization of pore-wall modification gradients generated on porous silicon photonic crystals using diazonium salts

One-dimensional photonic crystals (rugate filters) constructed from porous silicon were modified by the chemical hydrosilylation of terminal alkenes (decyl, 10-carboxydecyl, and 10-hydroxydecyl) in the presence of a concentration gradient of diazonium salt initiators. The concentration gradient was generated by vertically orienting the Si wafer containing the porous Si layer in an alkene solution and then introducing the diazonium salt at the bottom edge of the wafer. Slow diffusion of the salt led to a varying density of grafted alkene across the surface of the porous layer. The modified surfaces were end-capped with methyl groups by electrochemical grafting to impart improved stability and greater hydrophobicity. The surface modified with 10-carboxydecyl species was ionized by deprotonation of the carboxy groups to increase the hydrophilicity of this porous silicon surface. The pore-wall modification gradients were characterized using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS). The more hydrophilic portion of the gradient changes color when water infiltrates the porous nanostructure because of a shift in the stop band of the photonic crystal. The more hydrophobic portion of the gradient excludes water, although mixtures of water and ethanol will infiltrate this region, depending on the concentration of ethanol in the mixture. A simple visual sensor for small quantities of ethanol in water, capable of detecting ethanol concentrations of between 0 and 8% with a resolution of 1% is demonstrated.     

Electrophilic substitution of diazonium salts in 2-amino-4-(alkyl or aryl)oxazoles

Aryl diazonium fluoborates react readily with 2-amino-4-alkyloxazoles and 2-amino-4-aryloxazoles under mild conditions. The products are the corresponding 5-arylazo derivatives formed, in 44-98% yield free from side products.     

Nickel-catalyzed enantioselective vinylation of aryl 2-azaallyl anions

A unique enantioselective nickel-catalyzed vinylation of 2-azaallyl anions is advanced for the first time. This method affords diverse vinyl aryl methyl amines with high enantioselectivities, which are frequently occurring scaffolds in natural products and medications. This C–H functionalization method can also be extended to the synthesis of enantioenriched 1,3-diamine derivatives by employing suitably elaborated vinyl bromides. Key to the success of this process is the identification of a Ni/chiraphos catalyst system and a less reducing 2-azaallyl anion, all of which favor an anionic vinylation route over a background radical reaction. A telescoped gram scale synthesis and a product derivatization study confirmed the scalability and synthetic potential of this method.

A unique enantioselective Ni-catalyzed vinylation of 2-azaallyl anions is advanced. This method affords vinyl aryl methyl amine or 1,3-diamine derivatives with high enantioselectivities, which are frequently occurring scaffolds in medications.