Iodine-Promoted Sulfoximidation of Cinnamic Acids via Oxidative C═C Bond Cleavage

An iodine-promoted C═C bond cleavage with concomitant decarboxylation and cross-coupling between cinnamic acids and NH-sulfoximines has been developed. This reaction proceeds via selective C═C bond cleavage, followed by decarboxylation and oxidative sulfoximidation. This metal- and base-free protocol involves dioxygen as the source of oxygen, which is facilitated by tert-butyl hydroperoxide (TBHP) as the oxidant affording N-aroylated sulfoximines with good functional group tolerance and good yields.

Sulfur-Mediated Decarboxylative Amidation of Cinnamic Acids via C═C Bond Cleavage

A new strategy for the synthesis of amides has been developed using sulfur-mediated decarboxylative coupling of cinnamic acids with amines via oxidative cleavage of the C═C bond.

Synthesis of unsymmetrical ketones via dual catalysed cross-coupling of α,β-unsaturated carboxylic acids with aryldiazonium salts

A visible light-enabled synthesis of unsymmetrical ketones has been accomplished by the cross-coupling of α,β-unsaturated carboxylic acids and aryldiazonium salts embracing a synergistic eosin Y and Co(OAc)2·4H2O catalysis. The reaction involves decarboxylative aerobic CC bond cleavage, and is endowed with the creation of new C-C and C-O bonds with good substrate scope.

NIS-initiated photo-induced oxidative decarboxylative sulfoximidation of cinnamic acids

N-Iodosuccinimide catalyzed, visible-light-induced oxidative decarboxylative cross-coupling between cinnamic acids and NH-sulfoximines is presented. This strategy results in the formation of α-keto-N-acyl sulfoximines via the construction of two new CO bonds and one C-N bond. The in situ-generated N-iodosulfoximine serves as the light-absorbing species in the absence of any external photosensitizer. The keto carbonyl and amidic carbonyl oxygen in the resulting product originate from dioxygen and water respectively.

Copper-Catalyzed Decarboxylative Elimination of Carboxylic Acids to Styrenes

A copper-catalyzed decarboxylative elimination reaction of (hetero)aromatic propionic acids to vinyl (hetero)arenes has been developed. This method furnishes alkenes from carboxylic acids without the need for stochiometric Pb or Ag additives or expensive or specialized photocatalysts. A series of mechanistic experiments indicate that the reaction proceeds via benzylic deprotonation and subsequent radical decarboxylation; a pathway that is distinct from the single-electron-transfer mechanisms implicated in related decarboxylative elimination reactions.

Novel synthesis of 1,2-diaza-1,3-dienes with potential biological activity from cinnamic acids and diazonium salts of anilines

Cinnamic acids are an important class of phenolic compounds, which have many beneficial effects on human health but are also interesting synthetic intermediates thanks to the presence of several reactive sites. While studying the reactivity of cinnamic acids with diazonium salts from aromatic amines, an unexpected reactivity has been discovered, leading to the formation of 1,2-diaza-1,3-dienes instead of traditional diazo-coupling products. The new compounds have been fully characterized by mono and bidimensional NMR spectroscopy and mass spectrometry. Preliminary studies on the biological activity of the compounds have been carried out testing both their antibacterial and antitumor activity, leading to promising results.

Iron-catalyzed domino decarboxylation-oxidation of α,β-unsaturated carboxylic acids enabled aldehyde C-H methylation

A practical and general iron-catalyzed domino decarboxylation-oxidation of α,β-unsaturated carboxylic acids enabling aldehyde C-H methylation for the synthesis of methyl ketones has been developed. This mild, operationally simple method uses ambient air as the sole oxidant and tolerates sensitive functional groups for the late-stage functionalization of complex natural-product-derived and polyfunctionalized molecules.

Recent developments in decarboxylative C(aryl)-X bond formation from (hetero)aryl carboxylic acids

Decarboxylative coupling reactions using readily available (hetero)aryl carboxylic acids are a highly efficient approach for the formation of new C-C and C-X bonds. These decarboxylative coupling reactions eliminate CO2 as a by-product, resulting in a greener and environmentally more benign approach than conventional coupling reactions. In this review, we summarize the recent developments in ipso-decarboxylative C-X (X = O/N/halo/S/Se/P/CN) bond formations using (hetero)aryl carboxylic acids. Furthermore, we highlight the current limitations and future research opportunities of aryl-decarboxylative coupling reactions.

An iodine-mediated new avenue to sulfonylation employing N-hydroxy aryl sulfonamide as a sulfonylating agent

A novel and highly efficient I2/K2CO3 mediated regioselective sulfonylation of thiophenols, aryl acetylenic acid and aromatic alkynes with N-hydroxy sulfonamide has been developed. N-hydroxy sulfonamide has been used for the first time for the synthesis of these sulfones. The scope and versatility of the reaction has been demonstrated by the regio- and stereoselective synthesis of different analogs of sulfones with various structural features.

Wonderful fusion of organofluorine chemistry and decarboxylation strategy

Decarboxylation strategy has been emerging as a powerful tool for the synthesis of fluorine-containing organic compounds that play important roles in various fields such as pharmaceuticals, agrochemicals, and materials science. Considerable progress in decarboxylation has been made over the past decade towards the construction of diverse valuable fluorinated fine chemicals for which the fluorinated part can be brought in two ways. The first way is described as the reaction of non-fluorinated carboxylic acids (and their derivatives) with fluorinating reagents, as well as fluorine-containing building blocks. The second way is dedicated to the exploration and the use of fluorine-containing carboxylic acids (and their derivatives) in decarboxylative transformations. This review aims to provide a comprehensive summary of the development and applications of decarboxylative radical, nucleophilic and cross-coupling strategies in organofluorine chemistry.

Visible-Light-Induced Photocatalytic Oxidative Decarboxylation of Cinnamic Acids to 1,2-Diketones

A concerted metallophotoredox catalysis has been realized for the efficient decarboxylative functionalization of α,β-unsaturated carboxylic acids with aryl iodides in the presence of perylene bisimide dye to afford 1,2-diketones.

Advances in Electrochemical Decarboxylative Transformation Reactions

Owing to their non-toxic, stable, inexpensive properties, carboxylic acids are considered as environmentally benign alternatives as coupling partners in various organic transformations. Electrochemical mediated decarboxylation of carboxylic acid has emerged as a new and efficient methodology for the construction of carbon-carbon or carbon-heteroatom bonds. Compared with transition-metal catalysis and photoredox catalysis, electro-organic decarboxylative transformations are considered as a green and sustainable protocol due to the absence of chemical oxidants and strong bases. Further, it exhibits good tolerance with various functional groups. In this Minireview, we summarize the recent advances and discoveries on the electrochemical decarboxylative transformations on C-C and C-heteroatoms bond formations.

Boosting free radical type photocatalysis over Pd/Fe-MOFs by coordination structure engineering

The development of novel heterogeneous photocatalytic systems, along with a deep understanding of the relationship between the catalytic center chemical environment and the catalytic performance, is of great significance.

Copper-Catalyzed Decarboxylative Functionalization of Conjugated β,γ-Unsaturated Carboxylic Acids

Copper-catalyzed decarboxylative coupling reactions of conjugated β,γ-unsaturated carboxylic acids have been achieved for allylic amination, alkylation, sulfonylation, and phosphinoylation. This approach was effective for a broad scope of amino, alkyl, sulfonyl, and phosphinoyl radical precursors as well as various conjugated β,γ-unsaturated carboxylic acids. These reactions also feature high regioselectivity, good functional group tolerance, and simple operation procedure. Mechanistic studies show that the reaction proceeds via copper-catalyzed electrophilic addition onto an olefin followed by decarboxylation, with radical intermediates involved. These insights present a modular and powerful strategy to access versatilely functionalized allyl-containing skeletons from readily available and stable carboxylic acids.

Copper-catalyzed oxidative decarboxylative alkylation of cinnamic acids with 4-alkyl-1,4-dihydropyridines

We have developed a new oxidative decarboxylation of cinnamic acids with 4-alkyl-1,4-dihydropyridines to construct C(sp3)-C(sp2) bonds in the presence of copper catalyst and dicumyl peroxide (DCP). A variety of internal alkenes have been obtained with mild conditions, broad substrate scope and excellent functional group tolerance. This method has significant potential for application by using inexpensive and stable cinnamic acids instead of alkenyl halides and nitro-olefins.

Photocatalytic decarboxylative alkenylation of α-amino and α-hydroxy acid-derived redox active esters by NaI/PPh3 catalysis

Herein, we report the photocatalytic decarboxylative alkenylation reactions of N-(acyloxy)phthalimide derived from α-amino and α-hydroxy acids with 1,1-diarylethene, and with cinnamic acid derivatives through double decarboxylation, using sodium iodide and triphenylphosphine as redox catalysts. The reaction proceeds under mild irradiation conditions with visible blue light (440 nm or 456 nm) in an acetone solvent without recourse to transition-metal or organic dye based photoredox catalysts. The reaction proceeds via photoactivation of a transiently self-assembled chromophore from N-(acyloxy)phthalimide and NaI/PPh3. Solvation plays a crucial role in the reactivity.

Metal- and Solvent-Free Multicomponent Decarboxylative A3-Coupling for the Synthesis of Propargylamines: Experimental, Computational, and Biological Investigations

Decarboxylative A³-coupling of ortho-hydroxybenzaldehydes, secondary amines, and alkynoic acids is performed under catalyst and solvent-free conditions. The developed methodology provided a waste-free method for the synthesis of hydroxylated propargylamines which are versatile precursors for various bioactive heterocyclic scaffolds. The experimental and density functional theory studies revealed that the in situ-formed ortho-quinonoid intermediate (formed from ortho-hydroxybenzaldehyde and amine) undergoes a concerted Eschweiler-Clarke type decarboxylation with alkynoic acids. The synthesized compounds were evaluated for MAO-A, MAO-B, and AChE inhibitory activities as potential drug candidates for the treatment of various neurological disorders. Compound 4f was found to be the most potent and selective MAO-B (high selectivity over MAO-A) and AChE inhibitor in the series with IC₅₀ values of 4.27 ± 0.07 and 0.79 ± 0.03 μM, respectively.

Base-controlled divergent synthesis of vinyl sulfones from (benzylsulfonyl)benzenes and paraformaldehyde

A tuneable metal-free protocol for the selective preparation of α-substituted vinyl sulfone and (E)-vinyl sulfone derivatives has been described. The base played an important role in the selectivity control of transformation.

Rhodium(i)-catalyzed C6-selective C-H alkenylation and polyenylation of 2-pyridones with alkenyl and conjugated polyenyl carboxylic acids

A versatile Rh(i)-catalyzed C6-selective decarbonylative C-H alkenylation of 2-pyridones with readily available, and inexpensive alkenyl carboxylic acids has been developed. This directed dehydrogenative cross-coupling reaction affords 6-alkenylated 2-pyridones that would otherwise be difficult to access using conventional C-H functionalization protocols. The reaction occurs with high efficiency and is tolerant of a broad range of functional groups. A wide scope of alkenyl carboxylic acids, including challenging conjugated polyene carboxylic acids, are amenable to this transformation and no addition of external oxidant is required. Mechanistic studies revealed that (1) Boc2O acts as the activator for the in situ transformation of the carboxylic acids into anhydrides before oxidative addition by the Rh catalyst, (2) a decarbonylation step is involved in the catalytic cycle, and (3) the C-H bond cleavage is likely the turnover-limiting step.

Electrochemistry and Photoredox Catalysis: A Comparative Evaluation in Organic Synthesis

This review provides an overview of synthetic transformations that have been performed by both electro- and photoredox catalysis. Both toolboxes are evaluated and compared in their ability to enable said transformations. Analogies and distinctions are formulated to obtain a better understanding in both research areas. This knowledge can be used to conceptualize new methodological strategies for either of both approaches starting from the other. It was attempted to extract key components that can be used as guidelines to refine, complement and innovate these two disciplines of organic synthesis.

Cleavage of carbon–carbon bonds by radical reactions

This review provides insights into the in situ generated radicals triggered carbon–carbon bond cleavage reactions.

Direct access to bis-S-heterocyclesviacopper-catalyzed three component tandem cyclization using S8as a sulfur source

An elemental sulfur atom donor strategy for constructing a thiophene-fused thiazole bis-S-heterocyclic skeletonviaCu-catalyzed three-component tandem cyclization has been developed.

Cu-Catalysed oxidative amidation of cinnamic acids/arylacetic acids with 2° amines: an efficient synthesis of α-ketoamides

Copper-catalysed decarboxylation/oxidative amidation of cinnamic acids and oxidative amidation of arylacetic acids with 2° amines have been developed leading to the formation of α-ketoamides.