Radical C–H arylations of (hetero)arenes catalysed by gallic acid

Abstract

Gallic acid efficiently catalyses radical arylations in water-acetone at room temperature. This methodology proved to be versatile and scalable. Therefore, it constitutes a greener alternative to arylation. Moreover, considering that gallic acid is an abundant vegetable tannin, this work also unleashes an alternative method for the reutilisation of bio-wastes.

Salicylic Acid‐Catalyzed One‐Pot Hydrodeamination of Aromatic Amines by tert‐Butyl Nitrite in Tetrahydrofuran

“…Given the above mentioned control experiments and inspired by mechanistic investigations previously reported, we have proposed a plausible mechanism for this reaction (Scheme ). The fact that O ‐acetyl salicylic acid has a moderate positive impact on the reaction, while methyl salicylate does not act as catalyst suggested that the carboxylate is directly involved in the reaction.…”

“…Recently, Carrillo and co‐workers demonstrated that in‐situ generated arenediazonium ions can be conveniently reduced to aryl radicals at room temperature, using substoichiometric amounts of ascorbic acid (AscH 2 ) or gallic acid as promoters. The AscH 2 protocol has been implemented for the radical C−H arylation of (hetero)arenes in the preparation of aryl sulfides, in a [4+2] benzannulation to build phenanthrenes, and in a radical translocation to form α ‐alkoxybenzamides .…”

Salicylic Acid‐Catalyzed Arylation of Enol Acetates with Anilines

“…The group of Carrillo has reported that aryl radicals can be conveniently generated at room temperature, by reduction of the corresponding diazonium ions catalyzed by ascorbic acid [18] or gallic acid [19] . Inspired by their work, we have recently developed the hydrodeamination of in-situ formed diazonium salts, catalyzed by salicylic acid (SA) and using THF as the hydrogen donor.…”

Radical Arylation of Anilines and Pyrroles via Aryldiazotates

“…The major aim was to avoid the formation of azo compound 15 . A previous examination of existing radical transformations revealed that reactions that use aryldiazonium ions as radical sources or intermediates, such as the methods developed by the groups of Felpin, Carrillo, and Maulide, are limited to pyrroles with an electron‐withdrawing group on the nitrogen atom due to competing azo‐coupling reaction . A related silver‐nitrite‐assisted arylation by Gowrisankar and Seayad, the mechanism of which is yet unknown, might not proceed via free diazonium ions because electron‐rich pyrroles are tolerated.…”