Radical Decarboxylative Functionalizations Enabled by Dual Photoredox Catalysis

Abstract

Organic carboxylates are readily available feedstock chemicals, and the carboxylate group is a latent activating group which can be easily removed by decarboxylation. The radical decarboxylative functionalization by photoredox catalysis undergoes rapid development recently, with which many difficult transformations can be achieved by dual photoredox catalysis. We summarize radical decarboxylative functionalizations via additional transition metal catalysts, thiol catalysts, or hypervalent iodine catalysts, which either activate the carboxylates or enable new radical transformations.

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

“…Since the dawn of organic chemistry, several radical decarboxylations have been developed, including the Kolbe electrolysis [33,34], the Hunsdiecker reaction [35], and the Barton decarboxylation [36][37][38]. More recently, photoredox catalysis has appeared as a mild alternative to these venerable transformations [39,40], allowing the smooth generation of alkyl radicals from carboxylic acid derivatives. One of the main strategies for accessing C(sp 3 ) radi-Scheme 3: Illustrative example for the photocatalytic oxidative generation of radicals from carboxylic acids: the hydrodecarboxylation reported by Nicewicz and co-workers [41].…”

Mild, visible light-mediated decarboxylation of aryl carboxylic acids to access aryl radicals

“…In contrast, aryl carboxylic acids are abundant and cheap, making them appealing starting materials. Considering the wealth of methods for the functionalisation of alkyl carboxylic acids using photoredox catalysis, 1 the development of a mild protocol for the decarboxylative functionalisation of aryl carboxylic acids is of high importance.…”

Decarboxylative couplings as versatile tools for late‐stage peptide modifications

“…Developments in photocatalytic systems have enabled access to alkyl radicals using a variety of alternative photosensitizers and under various reactions conditions . Importantly, amino acid alkyl radicals generated in this manner are also known to engage readily with suitable radical traps or to be intercepted by standard transition‐metal‐catalyzed cross‐coupling cycles, setting the stage for downstream diversification.…”