Generation of alkyl and acyl radicals by visible-light photoredox catalysis: direct activation of C–O bonds in organic transformations

• Mithu Roy,
• Bitan Sardar,
• Itu Mallick and
• Dipankar Srimani

Beilstein J. Org. Chem. 2024, 20, 1348–1375, doi:10.3762/bjoc.20.119

• photocatalysis. The generated alkyl radicals then undergo the desired addition with alkyne to produce alkenyl radicals that via Ni-catalysed coupling reactions with aryl bromides form trisubstituted alkenes Z-selectively. Internal alkynes are not suitable for this transformation due to the steric reason, but

• recent photocatalysis methodologies in the field of C–O bond activation. As conventional techniques, such as Barton decarboxylation, create hazardous wastes, the use of alternative feedstocks, including alcohols and acids, has been encouraged to achieve sustainability. The recent advancements not only

Mechanistic investigations of polyaza[7]helicene in photoredox and energy transfer catalysis

• Johannes Rocker,
• Till J. B. Zähringer,
• Matthias Schmitz,
• Till Opatz and
• Christoph Kerzig

Beilstein J. Org. Chem. 2024, 20, 1236–1245, doi:10.3762/bjoc.20.106

• mechanism of the recently reported sulfonylation/arylation [45][46] reaction using laser flash photolysis (LFP). LFP is a powerful spectroscopic tool in photocatalysis that allows us not only to distinguish between energy and electron transfer but also to detect transient triplet states and radicals

Carbonylative synthesis and functionalization of indoles

• Alex De Salvo,
• Raffaella Mancuso and
• Xiao-Feng Wu

Beilstein J. Org. Chem. 2024, 20, 973–1000, doi:10.3762/bjoc.20.87

• interesting method toward indole-3-yl aryl ketones was reported by Zhang et al. Considering the ability of the aryldiazonium salts to act as aryl radical source, in presence of the suitable metal catalyst or taking advantage of photocatalysis, they decided to perform a direct carbonylation of indoles with

Regioselective quinazoline C2 modifications through the azide–tetrazole tautomeric equilibrium

• Dāgs Dāvis Līpiņš,
• Andris Jeminejs,
• Una Ušacka,
• Anatoly Mishnev,
• Māris Turks and
• Irina Novosjolova

Beilstein J. Org. Chem. 2024, 20, 675–683, doi:10.3762/bjoc.20.61

• techniques employing transition-metal and photocatalysis [15][16]. These methods facilitate C–C bond formation, enabling the introduction of alkyl groups at the C2 position of quinazoline derivatives. While arylsulfanyl group rearrangement reactions have been documented by us for modifying 2,4-substituted

Green and sustainable approaches for the Friedel–Crafts reaction between aldehydes and indoles

• Periklis X. Kolagkis,
• Eirini M. Galathri and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2024, 20, 379–426, doi:10.3762/bjoc.20.36

• development of greener synthetic technologies, like photocatalysis, organocatalysis, the use of nanocatalysts, microwave irradiation, ball milling, continuous flow, and many more. Thus, in this review, we summarize the medicinal properties of BIMs and the developed BIM synthetic protocols, utilizing the

Mechanisms for radical reactions initiating from N-hydroxyphthalimide esters

• Carlos R. Azpilcueta-Nicolas and
• Jean-Philip Lumb

Beilstein J. Org. Chem. 2024, 20, 346–378, doi:10.3762/bjoc.20.35

• , whereas the corresponding spirocycle in kadsulignan E was formed under Ir photocatalysis. In addition, photoinduced Pd catalysis was applied in the key macrocyclization

Visible-light-induced radical cascade cyclization: a catalyst-free synthetic approach to trifluoromethylated heterocycles

• Chuan Yang,
• Wei Shi,
• Jian Tian,
• Lin Guo,
• Yating Zhao and
• Wujiong Xia

Beilstein J. Org. Chem. 2024, 20, 118–124, doi:10.3762/bjoc.20.12

• enables a rapid access to heterocycles containing a trifluoromethyl group. Keywords: cascade reaction; indole derivatives; photocatalysis; radical chain process; trifluoromethylation; Introduction Dihydropyrido[1,2-a]indolone (DHPI) skeletons are commonly found in natural products and pharmaceutical

Optimizing reaction conditions for the light-driven hydrogen evolution in a loop photoreactor

• Pengcheng Li,
• Daniel Kowalczyk,
• Johannes Liessem,
• Mohamed M. Elnagar,
• Dariusz Mitoraj,
• Radim Beranek and
• Dirk Ziegenbalg

Beilstein J. Org. Chem. 2024, 20, 74–91, doi:10.3762/bjoc.20.9

• ) processes, and photocatalysis. Upon upscaling, both PV-E and PEC reactors exhibit pH gradients at electrodes and elevated solution electrical resistivity. These challenges arise from the substantial separation between reduction and oxidation sites, alongside mass transport restrictions in the liquid phase

Aromatic systems with two and three pyridine-2,6-dicarbazolyl-3,5-dicarbonitrile fragments as electron-transporting organic semiconductors exhibiting long-lived emissions

• Karolis Leitonas,
• Brigita Vigante,
• Dmytro Volyniuk,
• Audrius Bucinskas,
• Pavels Dimitrijevs,
• Sindija Lapcinska,
• Pavel Arsenyan and
• Juozas Vidas Grazulevicius

Beilstein J. Org. Chem. 2023, 19, 1867–1880, doi:10.3762/bjoc.19.139

• their application in photocatalysis has been recently published [9]. 2,6-Bis(4-cyanophenyl)-4-(9-phenyl-9H-carbazol-3-yl)pyridine-3,5-dicarbonitrile) exhibits two aggregate states in aqueous dispersions: amorphous nanospheres and ordered nanofibers with π–π molecular stacking. The nanofibers promoted

Recent advancements in iodide/phosphine-mediated photoredox radical reactions

• Tinglan Liu,
• Yu Zhou,
• Junhong Tang and
• Chengming Wang

Beilstein J. Org. Chem. 2023, 19, 1785–1803, doi:10.3762/bjoc.19.131

• remarkable advances not only highlighted the synthetic potential of photocatalysis but also served as inspiration for future developments of low-cost photocatalysis based on other non-covalent interactions. The simplicity, practicality, and broad substrate scope demonstrated by these approaches further

• emphasized their significance in facilitating the synthesis of diverse compounds and paving the way for further advancements in the field of photocatalysis. The highly efficient construction of carbon–heteroatom (C–X) bonds is of significant importance in the fields of natural products, pharmaceuticals, and

• hydrogenation or hydrogen transfer [40], electrocatalysis coupled with water oxidation [41], and sustained visible-light-induced photocatalysis [42]. Among the different strategies available, the use of a mild photocatalytic process involving hole-driven hydrogen transfer with hydrogen donors or hole scavengers

Selectivity control towards CO versus H₂ for photo-driven CO₂ reduction with a novel Co(II) catalyst

• Lisa-Lou Gracia,
• Philip Henkel,
• Olaf Fuhr and
• Claudia Bizzarri

Beilstein J. Org. Chem. 2023, 19, 1766–1775, doi:10.3762/bjoc.19.129

• chosen solvent for photocatalysis. The absorption profile evokes the structured band of the free ligand BzQuTr [42], with two intense π–π* ligand-centered transitions at circa 319 nm and 330 nm (Figure 3). The pink solid dissolves as an intense blue DMA solution. Nevertheless, the d–d transitions

Organic thermally activated delayed fluorescence material with strained benzoguanidine donor

• Alexander C. Brannan,
• Elvie F. P. Beaumont,
• Nguyen Le Phuoc,
• George F. S. Whitehead,
• Mikko Linnolahti and
• Alexander S. Romanov

Beilstein J. Org. Chem. 2023, 19, 1289–1298, doi:10.3762/bjoc.19.95

• fluorescence [1][2][3]. Organic TADF emitters have gained substantial attention in recent years for their prospective application in organic light-emitting diodes (OLEDs), photocatalysis, bioimaging, and sensors [4][5][6]. The ability to harvest both singlet and triplet excitons enable organic TADF emitters to

Radical ligand transfer: a general strategy for radical functionalization

• David T. Nemoto Jr,
• Kang-Jie Bian,
• Shih-Chieh Kao and
• Julian G. West

Beilstein J. Org. Chem. 2023, 19, 1225–1233, doi:10.3762/bjoc.19.90

• ; photocatalysis; radicals; Introduction The behavior of alkyl radicals has been studied rigorously for decades, though only recently have these come to be widely viewed as selective and useful synthetic intermediates [1][2][3][4]. This sea change has been driven by innovations in both the generation and

• quenched and functionalized through RLT. II: Modern catalysts developed for RLT catalysis. The incorporation of RLT catalysis in ATRA photocatalysis. I: The reported method is compatible with nucleophilic sources of chlorine groups, azide groups, and thioisocyanate groups. II: The proposed mechanism for

Enabling artificial photosynthesis systems with molecular recycling: A review of photo- and electrochemical methods for regenerating organic sacrificial electron donors

• Grace A. Lowe

Beilstein J. Org. Chem. 2023, 19, 1198–1215, doi:10.3762/bjoc.19.88

• sacrificial electron donors, and for researchers interested in designing new redox mediator and recyclable electron donor species. Keywords: artificial photosynthesis; photocatalysis; redox couple; sacrificial electron donor; solar fuels; Introduction Artificial photosynthesis research has resulted in the

• donors used in photoreduction catalysis for artificial photosynthesis. Specifically, organic electron or hydride donors usually applied in molecular photocatalysis. 2. Survey the literature from different fields and present a sample of potentially recyclable electron donors for artificial photosynthesis

• photocatalysis. Cyclic voltammetry carried out in standard conditions for mimicking an acetonitrile system had not been close enough to the catalytic conditions to get the required redox potentials. The difference between the oxidation potential of a sacrificial donor and the reduction potential of the excited

Exploring the role of halogen bonding in iodonium ylides: insights into unexpected reactivity and reaction control

• Carlee A. Montgomery and
• Graham K. Murphy

Beilstein J. Org. Chem. 2023, 19, 1171–1190, doi:10.3762/bjoc.19.86

• events. Xuan, Li and co-workers further investigated the coupling between iodonium ylides and tertiary amines, and showed that this thermal reaction could instead be initiated by blue light photocatalysis (Scheme 7) [124]. Therein, they investigated the iodoarene motif of the ylide, and while ylide 31

Photoredox catalysis harvesting multiple photon or electrochemical energies

• Mattia Lepori,
• Simon Schmid and
• Joshua P. Barham

Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81

• conditions. In 2020, the Polyzos group also demonstrated the carbonylative amidation of aryl halides in continuous flow with the in situ-generated [Ir2]0 (Figure 19A) [79]. This multi-photon tandem photocatalysis protocol provides an elegant alternative to established classical procedures for condensing

Clauson–Kaas pyrrole synthesis using diverse catalysts: a transition from conventional to greener approach

• Dileep Kumar Singh and
• Rajesh Kumar

Beilstein J. Org. Chem. 2023, 19, 928–955, doi:10.3762/bjoc.19.71

• to reduce energy consumption and the carbon footprint. The traditional heating techniques used to synthesize compounds are being replaced by contemporary green alternative energy systems, such as photocatalysis, microwave irradiation, ultrasonic irradiation, grinding, and ball milling processes

Photoredox catalysis enabling decarboxylative radical cyclization of γ,γ-dimethylallyltryptophan (DMAT) derivatives: formal synthesis of 6,7-secoagroclavine

• Alessio Regni,
• Francesca Bartoccini and
• Giovanni Piersanti

Beilstein J. Org. Chem. 2023, 19, 918–927, doi:10.3762/bjoc.19.70

• ][32][33], modification of biomacromolecules [34], and relatively complex pharmaceutical agents [35][36][37][38]. Photocatalysis tremendously enriches the synthetic compound library, providing a precious alternative to directly modify abundant natural substrates, including biomass, which usually

Synthesis of aliphatic nitriles from cyclobutanone oxime mediated by sulfuryl fluoride (SO₂F₂)

• Xian-Lin Chen and
• Hua-Li Qin

Beilstein J. Org. Chem. 2023, 19, 901–908, doi:10.3762/bjoc.19.68

• ], Liu [35], and Yang [36] achieved similar transformations through visible-light photocatalysis. In addition, Guo [37][38] improved the protocol by using low-cost nickel and iron catalysts. However, most of these advancements mainly relied on the excellent redox potential manipulation of cyclic oxime

Enolates ambushed – asymmetric tandem conjugate addition and subsequent enolate trapping with conventional and less traditional electrophiles

• Péter Kisszékelyi and
• Radovan Šebesta

Beilstein J. Org. Chem. 2023, 19, 593–634, doi:10.3762/bjoc.19.44

Transition-metal-catalyzed C–H bond activation as a sustainable strategy for the synthesis of fluorinated molecules: an overview

• Louis Monsigny,
• Floriane Doche and
• Tatiana Besset

Beilstein J. Org. Chem. 2023, 19, 448–473, doi:10.3762/bjoc.19.35

• derivatives. Finally, the use of abundant non-noble transition metals [209][210][211] in such reactions combined or not with modern technologies (photocatalysis and electrocatalysis) is still underexplored and any advances will be of high importance especially from a sustainability point of view aiming at

NaI/PPh₃-catalyzed visible-light-mediated decarboxylative radical cascade cyclization of N-arylacrylamides for the efficient synthesis of quaternary oxindoles

• Dan Liu,
• Yue Zhao and
• Frederic W. Patureau

Beilstein J. Org. Chem. 2023, 19, 57–65, doi:10.3762/bjoc.19.5

• afforded various functionalized oxindoles featuring a C3 quaternary stereogenic center. Mechanistic experiments suggest a radical mechanism. Keywords: decarboxylative cascade cyclization; iodide catalysis; metal-free photocatalysis; oxindole; phosphine catalysis; Introduction Radical-initiated cascade

• decarboxylative radical cascade cyclization of N-arylacrylamides with various redox-active esters derived from common and/or important carboxylic acids under mild conditions. Complementary to traditional transition metal photocatalysis and organo-photocatalysis [85], the readily available and inexpensive NaI/PPh3

Combining the best of both worlds: radical-based divergent total synthesis

• Kyriaki Gennaiou,
• Antonios Kelesidis,
• Maria Kourgiantaki and
• Alexandros L. Zografos

Beilstein J. Org. Chem. 2023, 19, 1–26, doi:10.3762/bjoc.19.1

• -mediated photocatalysis (using Pd(PPh3)2Cl2 in combination with xantphos) [112] towards 244, followed by Mukaiyama hydration with the aid of Mn(dpm)3, dioxygen, and PhSiH3 for the synthesis of kadsuphilin N (234). Conclusion The utility of radical retrosynthetic disconnections in natural product synthesis

Redox-active molecules as organocatalysts for selective oxidative transformations – an unperceived organocatalysis field

• Elena R. Lopat’eva,
• Igor B. Krylov,
• Dmitry A. Lapshin and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2022, 18, 1672–1695, doi:10.3762/bjoc.18.179

• of ethylbenzene and CH-fluorination of aldehydes catalyzed by N-hydroxybenzimidazoles, precursors of corresponding N-oxyl radicals. Mixed hetero-/homogeneous TiO2/N-hydroxyimide photocatalysis in the selective benzylic oxidation. Electrochemical benzylic iodination and benzylation of pyridine by

Mechanochemical bottom-up synthesis of phosphorus-linked, heptazine-based carbon nitrides using sodium phosphide

• Blaine G. Fiss,
• Georgia Douglas,
• Michael Ferguson,
• Jorge Becerra,
• Jesus Valdez,
• Trong-On Do,
• Tomislav Friščić and
• Audrey Moores

Beilstein J. Org. Chem. 2022, 18, 1203–1209, doi:10.3762/bjoc.18.125

• -PCN300) show a reduction in photoluminescent recombination, as well as a nearly two-time increase in photocurrent under broad spectrum irradiation, which are appealing properties for photocatalysis. Keywords: carbon nitride; density functional theory; mechanochemistry; phosphorus; photochemistry