Synthesis of Difluoromethyl Thioethers from Difluoromethyl Trimethylsilane and Organothiocyanates Generated In Situ

A copper‐CF₂H complex generated in situ from copper thiocyanate and TMS? CF₂H smoothly converts organothiocyanates into valuable difluoromethyl thioethers. This reaction step can be combined with several thiocyanation methods to one‐pot protocols, allowing late‐stage difluoromethylthiolations of widely available alkyl halides and arenediazonium salts. This strategy enables the introduction of difluoromethylthio groups—a largely unexplored substituent with highly promising properties—into drug‐like molecules.     

Copper(I)-promoted trifluoromethylthiolation of arenediazonium salts with AgSCF3

An efficient method for trifluoromethylthiolation of arenediazonium salts has been developed in mild conditions with a stable and convenient AgSCF₃. It provides a straightforward and convenient way for the synthesis of trifluoromethylthiolated compound from diazonium salts in moderate to good yields.     

芳基重氮盐及其冠醚络合物光解活泼自由基的ESR研究

本文用自由基捕捉剂2,3,5,6-四甲基亚硝基苯(ND)及苯亚甲基叔丁基氮氧化物(PBN)与ESR相结合的方法研究了芳基重氮盐RC_6H_4N~+_2BF~-_4(R=F, Cl, Br, I, NO_2, COOH,OCH_3及H)及其与18-冠-6、二苯并-24-冠-8的络合物在苯中的光解过程。结果表明它们光解产生了活泼自由基RC_6H_4并可被ND及PBN捕捉....     

Dediazoniation of Arenediazonium Ions in Homogeneous Solution. Part XII. Solvent effects in competitive heterolytic and homolytic dediazoniations

In heterolytic dediazoniations arenediazonium salts form aryl cations. The reaction rates are relatively slow; they depend only to a small extent on the solvent. It is shown that the solvents in which the heterolytic dediazoniation mechanism is predominant have a low nucleophilicity, whereas in solvents of high nucleophilicity homolysis of arenediazonium salts, i.e. the formation of aryl radicals and related intermediates, is favoured. Under comparable conditions, homolytic rates are faster than the corresponding rates of heterolysis. Homolysis is strongly enhanced by addition of nucleophiles which form relatively stable radicals by electron transfer. The ability of additives to catalyze homolysis of arenediazonium salts can be explained using the concept of a nucleofugic

1 In the original proposal [32] we used the word nucleofugal. In keeping with a forthcoming proposal on nomenclature in physical organic chemistry by Commission III.2 (Physical Organic Chemistry) of IUPAC we now use the word nucleofugic.

homolytic leaving group.     

Investigation of the behavior of arenediazonium salts with olefins in BmimPF6

The palladium-catalyzed reactions of olefins with arenediazonium salts in ionic liquids were investigated. For methyl acrylate and methyl acrylonitrile, normal Heck cross-coupling products are obtained in good yields. However, highly selective dimerization products are formed in excellent yields for styrenes. The catalyst system can be recycled.     

Palladium-catalyzed homocoupling of arenediazonium salts: an operationally simple synthesis of symmetrical biaryls

A simple procedure for the intermolecular homocoupling of arenediazonium salts in air using a catalytic amount of palladium acetate is described. The optimum conditions were found to be 15 mol % palladium acetate in refluxing methanol, with no additional terminal reducing agent required. These optimized conditions were used to prepare biaryls from several arenediazonium tetrafluoroborate salts, and most examples proceeded in moderate to high yields.     

Simple and catalyst-free method for the synthesis of diaryl selenides by reactions of arylselenols and arenediazonium salts

We describe here a simple and catalyst-free method to synthesize diaryl selenides by reaction of arenediazonium tetrafluoroborate salts with arylselenols, generated in situ by using diaryl diselenides and hypophosphorous acid (H₃PO₂), using THF as solvent. This is a direct nucleophilic aromatic substitution (SNAr) reaction performed with diaryl diselenides and arenediazonium salts bearing electron-withdrawing and electron-donating groups affording the corresponding diaryl selenides in moderated to good yields.     

Polyaniline‐Induced CH Arylation of Arenes with Arenediazonium Salts

A reduced form of polyaniline has been shown to induce direct arylation of an arenediazonium salt with an arene (Gomberg–Bachmann reaction) to give the cross‐coupling product in moderate to good yields under mild conditions. Various arenediazonium salts and arenes, including heteroarenes such as furans, thiophenes, and pyrroles, are employed for the reaction. The most favorable combination of substrates is an electron‐poor arenediazonium salt with an electron‐rich heteroarene. Investigation of the mechanism by reactions with radical scavengers and experiments on kinetic isotope effects indicated the occurrence of a radical chain reaction initiated by one‐electron reduction of an arenediazonium salt by the polyaniline. Only 1 mol % (based on aniline tetramer) of the polyaniline is required for the cross‐coupling reaction to occur. This reaction proceeds under metal‐free conditions and with no need for photonic activation.     

Pd-catalyzed cross-coupling reactions of arenediazonium salts with arylsilanes and aryltrifluoroborates in water

Pd-catalyzed cross-coupling reactions of various arenediazonium salts with ArSi(OR)₃ and KArBF₃ have been achieved in good to excellent yields under simple aerobic conditions in water at room temperature. The functional group tolerance makes these transformations as attractive alternatives to the traditional cross-coupling approaches. Furthermore, the sequence can also be performed in a one-pot domino process, omitting the isolation of the intermediate arenediazonium salt.     

苯基重氮盐-冠醚分子嵌合物的FAB-MS及其准分子离子生成机理的研究

Fast atom bombardment mass spectra of a series of arenediazonium salts with various substituents complexed with 18-crown-6 and dibenzo-24-crown-8 ethers were examined. The correlation between quasi-molecular ion abundance of various complexes and the properties, coordination ability of donor-acceptor linkages in the complexes were studied. By using molecular orbital calculation we have successfully demonstrated that the correlation cited is related to the electron cloud densities on the heteroatoms α-N and β-N of arenediazonium salts.     

Synthesis of a novel C2-symmetric thiourea and its application in the Pd-catalyzed cross-coupling reactions with arenediazonium salts under aerobic conditions

[reaction: see text] A novel thiourea-based C2-symmetric ligand was synthesized, and its application in the palladium-catalyzed Heck and Suzuki coupling reactions of arenediazonium salts was evaluated. The reactions, which were performed at room temperature, without added base, and under aerobic conditions, produced product in 4 h with good yield. The corresponding arenediazonium salts were easily generated in one step from anilines.     

Ion-selective electrodes in titrations involving azo-coupling reactions: Part 5. Determination of arenediazonium salts of ampholytic character

Determination of arenediazonium salts (0.3–0.7 g) of ampholytic character is based on their reaction with 1-phenyl-3-methyl-5-pyrazolone, the excess of which is titrated with a 4-bromo-1-naphthalenediazonium chloride solution. The titration is monitored potentiometrically with a PVC membrane electrode plasticized with 2,4-dinitrophenyl n-octyl ether. Eight arenediazonium salts containing hydrophilic groups (e.g., carboxylic and sulfonic acids) were determined without systematic errors.     

Methods for the synthesis of cinnolines (review)

This review analyses the principal approaches to the synthesis of the cinnoline nucleus, used as synthetic precursors of arenediazonium salts, arylhydrazones, and arylhydrazines, and also reductive methods for the synthesis of polycondensed derivatives of cinnoline. The mechanisms of the transformations and the possibilities and limitations of the various methods are discussed. Special attention is paid to methods based on the cyclization of derivatives of arenediazonium salts, which have been developed substantially in recent years. In memory of A. A. Potekhin __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 643–667, May, 2008.     

Synthesis of Heterocycles Based on Products of Anion Arylation of Unsaturated Compounds. 5. Reaction of 2-Aryl-1,4-benzoquinones with Thiourea

2-Aryl-1,4-benzoquinones, that can be obtained by arylation of quinone by arenediazonium salts, regioselectively react with thiourea in acid medium to form 7-aryl-5-hydroxy-1,3-benzoxathiol-2-ones. In the presence of excess arylquinones at room temperature, 2-amino-6-hydroxybenzothiazoles are formed in the same reaction.     

Mechanism of Meerwein arylation of furan derivatives

Catalytic arylation of furan-2-carbaldehyde with arenediazonium salts was studied. The yields of 5-arylfuran-2-carbaldehydes were found to depend on the solvent, catalyst, and anion in the arenediazonium salt. Redox catalysis and generation of aryl radicals are not sufficient conditions for the reaction to occur. The reaction is successful only under conditions ensuring formation of complex intermediates. A mechanism involving two Cu²⁺ ? Cu⁺ catalytic series and generation of furan-2-carbaldehyde was proposed.     

Palladium catalyzed Heck reaction of arenediazonium tetrafluoroborate salts with Baylis-Hillman adducts: production of α-benzyl-β-keto esters

A novel experimental procedure to obtain α-benzyl-β-keto esters from the Heck reaction between arenediazonium tetrafluoroborate salts and Baylis-Hillman (BH) adducts in the presence of Pd(OAc)₂ as catalyst is described. The methodology is simple, straightforward and the use of arenediazonium salts as opposed to conventional arylhalides/triflates over the usual Heck reaction is highlighted.     

Substrate-directable Heck reactions with arenediazonium salts. The regio- and stereoselective arylation of allylamine derivatives and applications in the synthesis of naftifine and abamines

The palladium-catalyzed, substrate-directable Heck-Matsuda reaction of allylamine derivatives with arenediazonium salts is reported. The reaction proceeds under mild conditions, with excellent regio- and stereochemical control as a function of coordinating groups present in the allylamine substrate. The distance between the olefin moiety and the carbonylic system seems to play a key role regarding the regiocontrol. The method presents itself as robust, as simple to carry out, and with wide synthetic scope concerning the allylic substrates and the type of arenediazonium employed. The synthetic potential of the method is illustrated by the short total syntheses of the bioactive compounds naftifine, abamine, and abamine SG.     

Arenediazonium salts immobilized in imidazolium ionic liquids as electrophilic partners in the Pd(OAc)2-catalyzed Matsuda-Heck arylation

The utility of arenediazonium salts immobilized in imidazolium-ILs [BMIMPF₆ and BMIMBF₄] for facile, high yielding, synthesis of olefins via the Pd(OAc)₂-catalyzed Matsuda-Heck arylation reaction has been demonstrated. The reaction can also be performed as a two-step process in the IL starting from ArNH₂, by sequential in-situ diazotization-arylation. Simple product isolation and the recycling/re-use of the IL are additional advantages of this one-pot method.     

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.     

On the absolute reactivity of aryl cations: Selectivity toward halide ions as a function of viscosity

The selectivities toward bromide and chloride ions observed in the dediazoniation of three arenediazonium salts are found to be independent of viscosity. It is inferred that the capture of aryl cations by these halide ions is diffusion controlled.