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

Photocatalytic decarboxylation of free carboxylic acids and their functionalization

Visible light mediated decarboxylative functionalization of carboxylic acids and their derivatives has recently emerged as a novel and powerful toolkit for small molecule activation in diverse carbon-carbon and carbon-hetero bond forming reactions. Naturally abundant highly functionalized bench-stable carboxylic acid analogs have been employed as promising alternatives to non-trivial organometallic reagents for mild and eco-benign synthetic transformation with traceless CO2 by-products. In this highlight article, we focus on the development of various photodecarboxylative functionalization strategies along with intra/inter-molecular cyclization via concerted single electron transfer (SET) or energy transfer (ET) pathways. Moreover, widely explored carboxylic acids are systematically classified here into four categories; i.e., α-keto, aliphatic, α,β-unsaturated, and aromatic analogs for a concise overview to the readership. The association of decarboxylative radical species with coupling partners to construct C-C and C-N/O/S/P/X bonds for each analogous acid has been presented in brief.

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 Indolyl Phenyl Diketones through Visible-Light-Promoted Ni-Catalyzed Intramolecular Cyclization/Oxidation Sequence of Ynones

The combination of visible light catalysis and Ni catalysis has enabled the synthesis of indolyl phenyl diketones through the cyclization/oxidation process of ynones. This reaction proceeded under mild and base-free conditions and showed a broad scope and feasibility for gram-scale synthesis. Several natural products and biologically interesting molecules could be readily postfunctionalized by this method.

Dual Oxidation of Epoxides with a High-Valent Cu(III)-CF3 Compound and DMSO to Access 1,2-Diketones

This study reports sequential dehydrogenation and transfer oxygenation of 1,2-diarylepoxides by high-valent phenCu(III)(CF3)3 and DMSO to produce 1,2-diketones. The Cu(III)-CF3 compound serves as a CF3 radical source to abstract the hydrogen atom of the epoxide ring. The resulting ether α-carbon radical undergoes ring-opening rearrangement to give a ketone α-carbon radical intermediate, which is oxygenated by DMSO with the release of Me2S. The combination of a Cu(III)-CF3 compound and DMSO may be exploited to develop other novel oxidation reactions.

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.

Visible-Light-Mediated Synthesis of α-Ketoamides via Oxidative Amination of 2-Bromoacetophenones Using Eosin Y as a Photoredox Catalyst

An oxidative amination of 2-bromoacetophenones has been accomplished to provide α-ketoamides by using photoredox catalysis with air as oxidant. The reactants are readily accessible, and the method is endowed with broad substrate scope and good functional group tolerance. The practicality of the approach is also shown by a gram-scale reaction.

Recent Developments on Photochemical Synthesis of 1,n-Dicarbonyls

1,n-dicarbonyls are one of the most fascinating chemical feedstocks finding abundant usage in the field of pharmaceuticals. Besides, they are utilized in a plethora of synthesis in general synthetic organic chemistry. A number of 'conventional' methods are available for their synthesis, such as the Stetter reaction, Baker-Venkatraman rearrangement, oxidation of vicinal diols, and oxidation of deoxybenzoins, synonymous with unfriendly reagents and conditions. In the last 15 years or so, photocatalysis has taken the world of synthetic organic chemistry by a remarkable renaissance. It is fair to say now that everybody loves the light and photoredox chemistry has opened a new gateway to organic chemists towards milder, more simpler alternatives to the previously available methods, allowing access to many sensitive reactions and products. In this review, we present the readers with the photochemical synthesis of a variety of 1,n-dicarbonyls. Diverse photocatalytic pathways to these fascinating molecules have been discussed, placing special emphasis on the mechanisms, giving the reader an opportunity to find all these significant developments in one place.

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.

Merging Photocatalytic C-O Cross-Coupling for α-Oxycarbonyl-β-ketones: Esterification of Carboxylic Acids via a Decarboxylative Pathway

Herein, the first merged photocatalytic pathway for the C-O cross-coupled esterification of carboxylic acids to α-oxycarbonyl-β-ketones has been demonstrated. Decarboxylation of α,β-unsaturated acids promotes the formation of the β-ketone fragment of the desired product. Water as the source of oxygen for the ketone segment and aerial oxygen as an oxidant make the present synthetic methodology green and sustainable. This new C═O and C-O bond-forming methodology takes place in a cascade manner under a dual Ir/Pd-catalytic pathway, with the liberation of H₂O and CO₂ as the only byproducts.

Impact of Erbium (Er) and Yttrium (Y) doping on BiVO4 crystal structure towards the enhancement of photoelectrochemical water splitting and photocatalytic performance

An efficient BiVO₄nanocatalyst with Erbium (Er) and Yttrium (Y) doping was synthesized via a facile microwave irradiation route and the obtained materials were further characterized through various techniques such as p-XRD, FT-IR, FE-SEM, HR-TEM, UV-Vis DRS, PL, LSV, and EISanalysis. The obtained results revealed that the rare metals induce the stabilization of the monoclinic-tetragonal crystalline structure with a distinct morphology. The yttrium doped BiVO₄ (Y-BiVO₄) monoclinic-tetragonal exhibited anefficient photoelectrochemical water splitting and photocatalytic performanceare compared to bare BiVO₄. TheY-BiVO₄ indicated increased results of photocurrent of 0.43 mA/cm²and bare BiVO₄0.24 mA/cm². Also, the Y-doped BiVO₄ nanocatalyst showed the maximum photocatalytic activity for the degradation of MB, MO, and RhB. A maximum degradation of 93%, 85%, and 91% was achieved for MB, MO, and RhB respectively, within 180 min under the visible light illumination. The photocatalytic decomposition of acetaldehyde also was performed. The improved photoelectrochemical water splitting and photocatalytic activity are due to the narrowing the bandgap, leading to extending the photoabsorption capability and reducing the recombination rate of photoexcited electron-hole pairs through the formation inner energy state of the rare earth metals. The current study disclosed that the synthesis of nanomaterials with crystal modification could be a prospectivecontender forhydrogen energy production as well as to the photocatalytic degradation of organic pollutants.To the best of our knowledge, both photocatalytic and photoelectrochemical studies were never been reported before for this type of material.

I2-Catalyzed Carbonylation of α-Methylene Ketones to Synthesize 1,2-Diaryl Diketones and Antiviral Quinoxalines in One Pot

An efficient approach for the synthesis of 1,2-diaryl diketones was developed from readily available α-methylene ketones by catalysis of I2. In the same oxidation system, a novel one-pot procedure was established for the construction of antiviral and anticancer quinoxalines. The reactions proceeded well with a wide variety of substrates and good functional group tolerance, affording desired compounds in moderate to excellent yields. Quinoxalines 4ca and 4ad inhibited viral entry of SARS-CoV-2 spike pseudoviruses into HEK-293T-ACE2h host cells as dual blockers of both human ACE2 receptor and viral spike RBD with IC50 values of 19.70 and 21.28 μM, respectively. In addition, cytotoxic evaluation revealed that 4aa, 4ba, 4ia, and 4ab suppressed four cancer cells with IC50 values ranging from 6.25 to 28.55 μM.

A porous organic polymer supported Pd/Cu bimetallic catalyst for heterogeneous oxidation of alkynes to 1,2-diketones

A reusable Pd/Cu bimetal-loaded porous organic polymer (Pd/Cu@POP–POPh3) has been developed for heterogeneous oxidation of various alkynes to afford the corresponding 1,2-diketones in high to excellent yields.