Diazonium Salts as Nitrogen-Based Lewis Acids

Abstract

Aryldiazonium salts are widely used in many organic transformations with displacement of N2 or through addition to the terminal nitrogen. Such aryldiazonium salts can be viewed as N-based Lewis acids that can react with Lewis bases to synthesize a wide variety of azo compounds. Additionally, diazonium salts are known to undergo single-electron transfer and release N2, forming an aryl radical, which results in different reactivity. Herein, we provide a concise overview of the reactivity of aryldiazonium salts undergoing classical donor-acceptor reactivity or single-electron transfer.

Selective Radical Transformations with Aryldiazonium Salts

“…[11] The former reactivity is highly employed to produce dyes, photoresponsive materials and biorthogonal processes. [12,13] Although reactive cationic intermediates might be obtained under anaerobic heating, the most general pathway relies upon the transition metal catalyzed oxidative addition into these salts. [14][15][16][17] This chemistry has been witnessing a remarkable evolution in the last years and was covered in recent reviews.…”

“…Most of their reactions explore three major reactivities: a) nucleophilic attack into the diazonium moiety producing azo compounds; b) heterolytic cleavage producing aryl cations; and c) homolytic C−N cleavage leading to aryl radicals [11] . The former reactivity is highly employed to produce dyes, photoresponsive materials and biorthogonal processes [12,13] . Although reactive cationic intermediates might be obtained under anaerobic heating, the most general pathway relies upon the transition metal catalyzed oxidative addition into these salts [14–17] .…”

Effects of Electrolytes on the Dediazoniation of Aryldiazonium Ions in Acidic MeOH/H2O Mixtures

“…The chemistry of these compounds has been originally carried out in aqueous solutions [4], but chemists went further and developed new synthetic methods that use reactions of diazonium salts in organic solvents [5][6][7][8]. In recent years, their chemistry has been exploited in the synthesis of unnatural amino acids [5], inpalladium-catalyzed cross-coupling reactions [7,9,10] and, for example, as nitrogen-based Lewis acids [6,11].…”

Aryl DiazoniumSalt‐TriggeredCyclization and Cycloaddition Reactions: Past, Present, and Future

“…[ 23‐25 ] In addition, direct reduction or nucleophilic addition‐type reactions of the N≡N moiety have also been realized to give arylhydrazines and azo compounds (Figure 1b). [ 26‐32 ] In sharp contrast, the potential of transforming aryl diazonium salts into N ‐heterocycles while keeping the two nitrogen atoms intact (Figure 1c), has been living in the shadows of coupling and reduction/addition reactions. In fact, from a sustainable point of view, introducing both nitrogen atoms into the final products would be more atom‐economic.…”