Recent Advances in the Decarboxylative Strategy of Coumarin‐3‐carboxylic Acid

Abstract

Coumarin is a highly proficient scaffold with great effectiveness which uplifts emerging chemists to create coumarin derivatives using cutting‐edge synthetic techniques. However, severe reaction conditions are required to develop substituted coumarin analogous. Notably, the carboxylic acid group in coumarin has emerged as a flexible functionality facilitating the construction of coumarin‐containing building blocks, emphasizing the decarboxylative strategy. Use of the decarboxylative technique has tremendously increased, due to its ability to increase the reactivity of the substrate. Moreover, it is the most extensively investigated synthetic strategy incorporating various functionalities in coumarin nuclei. This review discusses the decarboxylative strategies for creating C‐3 and C‐4 substituted coumarin derivatives. It emphasizes various interactions, including catalyst‐based, catalyst‐free, Michael addition, cyclo addition, three components, oxidative, and photocatalytic system involving the decarboxylation process.

Iron-Catalyzed Oxidative C(sp3)–C(sp3) Radical Coupling Reaction between Thiohydantoins and O-Acetyloximes for the Synthesis of 1,3-Dibenzyl-3,4-dihydropyrrolo[2,3-d]imidazole-2(1H)-thione Derivatives

“…Iron salts are frequently employed as redox catalysts in the formation of C-C and C-X bonds by radical coupling strategy during the synthesis of diverse heterocyclic compounds. [22][23][24][25][26][27][28] Radicals generated from metals energize O-acetyl oximes, forming bonds with diverse, active cycles that adhere to intramolecular condensation and generate cyclic products. It is formed when the active hydrogen of thiohydantoin is activated via undergoing radical coupling.…”

Copper Catalyzed Heteroannelation Reaction between 4‐Thiazolidinones and O‐Acetyl Oximes to Synthesize 2,5‐Diphenyl‐3‐(Pyrimidin‐2‐yl)‐3,4‐Dihydro‐2H‐Pyrrolo‐[2,3‐d]‐Thiazole

“…In particular, an oxidative coupling/annulation strategy has attracted more interest because it is a relatively atom‐economical and environmentally benign route for the synthesis of pyrrole rings. Various strategies for C−H and N−H bond annulation of aryl amides with unactivated olefins by merging Cobalt(III) and photoredox catalysis have also been reported [16,17] …”

“…The protocol to construct C−C and C−X radical couplings using transition metals has been established as an efficient method in the synthetic organic chemistry [29,30] . Formation of a direct C−C bond using C−H functionalization further goes for aromatization and annulation reduces the steps, which is an advancement in the synthetic route to get a valuable heterocyclic nucleus.…”

“…Various strategies for CÀ H and NÀ H bond annulation of aryl amides with unactivated olefins by merging Cobalt(III) and photoredox catalysis have also been reported. [16,17] Ketoximes are known to produce NÀ CÀ C fragments for the synthesis of N-heterocycles through homocouplings with various unsaturated functionalities. [18][19][20][21][22] Recently, synthesis of numbers of fused heterocyclic compounds have been reported using ketoximes and transition metal catalysts.…”

“…In 2024, Chikhalia et al. developed an iron‐catalyzed oxidative Csp 3 ‐Csp 3 radical coupling for the synthesis of 1,3‐dibenzyl‐3,4‐dihydropyrrolo[2,3‐ d ]imidazole‐2(1 H )‐thione derivatives [28] . Based on the above literature, we were tempted to work on the 4‐thiazolidinone nucleus via a radical coupling synthetic strategy.…”