Aryldiazonium Salts in Photoredox Catalysis – Recent Trends

Abstract

Aryl diazonium salts are an important class of organic compounds that are now widely used as arylating agents in photoredox catalysis owing to their lower redox potential, broad substrate scope, and atom economy. They have successfully been used in many interesting organic transformations to introduce an aryl group. They serve as good alternatives for aryl halides and other aryl organometallic reagents primarily used as aryl group surrogates. New reactions using aryl diazonium salts are continually emerging, and in this review, we have highlighted some recent developments in photoredox arylations and their applications. 4.3. Oxy-Arylation of Alkynes for the Synthesis of Benzofuran 4.4.

Aromatization as the driving force for single electron transfer towards C–C cross-coupling reactions

“…Aryldiazonium salts were chosen as the aryl partner, as N 2 is released as a by-product from the reaction, making the reduction easier. 30,31 As disclosed earlier, the chloro substituted diazonium salt gave 80% yield within 10 h. 4-Tolyl and 2-tolyl diazonium salts afforded their respective biphenyls 2b and 2d in 72-82% yields. Similarly, the m-xylyl diazonium salt reacted with benzene to furnish biphenyl product 2c in 74% yield.…”

Aqueous and Visible-Light-Promoted C–H (Hetero)arylation of Uracil Derivatives with Diazoniums

“…In contrast to the traditional functionalization of uridine, which required protection of hydroxyls and prehalogenation at the C5-position, this strategy could utilize the ribose directly, indicating that the photocatalytic C−H bond arylation may be developed into bioorthogonal transformations under physiological conditions. The above two schemes have proven that the diazonium salts 26 are excellent (hetero)aryl sources for the selective C−H functionalization of uracil derivatives. Based on the mechanisms proposed by others for related systems, 33,34 we conjectured that the excited Eosin-Y (Eosin-Y*) upon light irradiation with blue LED bulbs underwent a single-electron transfer with the diazonium salt 5 to yield the corresponding aryl radical I, together with nitrogen and tetrafluoroborate anion (Scheme 4).…”

Multicomponent reactions and photo/electrochemistry join forces: atom economy meets energy efficiency

“…Aryl diazonium salts represent another class of widely employed radical precursors. 71 Facile preparation from the corresponding anilines and relatively low redox potential concurred to the success of aryldiazonium salts, starting with the seminal contributions from Pschorr and Meerwein. 72 The latter Scheme 20 Friedel Crafts-type alkylation of (hetero)arenes.…”