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

Abstract

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.

Radical Arylation of Anilines and Pyrroles via Aryldiazotates

“…[b] For the ptGB 10 and Diaz 10 procedures the yield was determined after flash column chromatography.…”

“…The most commonk nown radicalp recursors for arylation reactions are aryldiazonium salts, [10] which may also be generated in situ, [11] as well as aryl chlorides, bromides, and iodides. [12] This variety has recently been complemented by arylhydrazines, [13] diaryliodonium salts, [14] and arylboronic acids.…”

Designing conjugated porous polymers for visible light-driven photocatalytic chemical transformations

“…A few early examples of organic polymer photocatalysts were linear chains with delocalized p-systems, 59,60 followed by recent studies of linear polymers with considerable photocatalytic performance. [61][62][63][64][65] By integrating morphological and surficial properties in three dimensional structures, additional strengths such as high stability, reusability and selectivity could be generated as add-on advantages, resulting into recent research activities on CPPs. In the following sections, our main focus will be firstly on the molecular design of CPPs according to the principle of photocatalysis with semiconductive materials.…”

C–H Arylation of N‐Heteroarenes under Metal‐Free Conditions and its Application towards the Synthesis of Pentabromo‐ and Pentachloropseudilins

“…The direct arylation of pyrroles via C–H bond activation under transition metal and metal‐free conditions have been tried by employing diverse coupling partners such as aryl halides, and aryl boronic acids , . In addition to this, Meerwein‐type arylation using diazonium salts, and anilines, have also been employed (Figureà). In the recent decade, this approach has attracted the major attraction because of the recent development regarding the exploration of suitable conditions for the in situ generation of diazonium salts .…”

“…Moreover, this approach work via aryl radical upon electron addition which has been exploited from metals and photoredox conditions. Recently, small molecules such as ascorbic acid,[19a] polyaniline[17a], [19b] hydrazine,[17b] gallic acid,[17c] and hydrogen peroxide[19c] capable of single electron‐transfer reactions were also used for the reduction of diazonium salts to generate aryl radicals. However, most of these method works well with an electron‐withdrawing group containing pyrroles such as N ‐Boc and N ‐tosyl pyrroles and pose problem with electron‐donating group containing pyrroles and NH ‐pyrroles which gave unwanted azo‐products instead of 2‐arylated pyrroles[18a] except, Gowrisankar and Seayed method.…”