Tetraphenylethylene-embedded pillar[5]arene-based orthogonal self-assembly for efficient photocatalysis in water

• Zhihang Bai,
• Krishnasamy Velmurugan,
• Xueqi Tian,
• Minzan Zuo,
• Kaiya Wang and
• Xiao-Yu Hu

Beilstein J. Org. Chem. 2022, 18, 429–437, doi:10.3762/bjoc.18.45

• photosynthesis and exhibited a high catalytic efficiency for the photocatalytic dehalogenation reaction of various bromoketone derivatives with good yields in short reaction time in water. Keywords: aggregation-induced emission; Förster resonance energy transfer; host–guest interaction; photocatalysis

• of solar energy [7]. In general, an effective supramolecular donor–acceptor system was employed to construct a photocatalytic system using FRET [6][8]. To fabricate a successful FRET system, the following key points need to be considered, i) the acceptor absorption spectrum should have good

• supramolecular photocatalytic systems by self-assembly strategies [10][11]. Recently, FRET-based supramolecular self-assembled systems [12][13] as nanoreactors for various photocatalytic reactions have received significant attention from the supramolecular community because of their robust molecular design and

DABCO-promoted photocatalytic C–H functionalization of aldehydes

• Bruno Maia da Silva Santos,
• Mariana dos Santos Dupim,
• Cauê Paula de Souza,
• Thiago Messias Cardozo and
• Fernanda Gadini Finelli

Beilstein J. Org. Chem. 2021, 17, 2959–2967, doi:10.3762/bjoc.17.205

• , Universidade Federal do Rio de Janeiro 149, Athos da Silveira Ramos Ave, Rio de Janeiro RJ, 21941-909, Brazil 10.3762/bjoc.17.205 Abstract Herein we present a direct application of DABCO, an inexpensive and broadly accessible organic base, as a hydrogen atom transfer (HAT) abstractor in a photocatalytic

• abstractor in photocatalytic strategies could expand the catalyst combinations, as illustrated in Figure 1, to create new and exciting methodologies and improve the understanding on theoretical aspects of the HAT process with nitrogen radical cations. However, despite its promising chemical properties and

•  2a). Suga and co-workers reported an electrochemical approach for P–H bond activation promoted by this reactive species, leading to the synthesis of several phosphacycles [24] (Figure 2b). Concomitantly with the development of our work, some photocatalytic strategies for DABCO activation emerged. Li

Exfoliated black phosphorous-mediated CuAAC chemistry for organic and macromolecular synthesis under white LED and near-IR irradiation

• Azra Kocaarslan,
• Zafer Eroglu,
• Önder Metin and
• Yusuf Yagci

Beilstein J. Org. Chem. 2021, 17, 2477–2487, doi:10.3762/bjoc.17.164

• . In this respect, 2D materials offer great potential due to converting the inexhaustible energy of sunlight into chemical and electrical energy along with having a less environmental impact. After the discovery of the photocatalytic effect of 2D materials under UV light [14][15] the heterogeneous

Photoredox catalysis in nickel-catalyzed C–H functionalization

• Lusina Mantry,
• Rajaram Maayuri,
• Vikash Kumar and
• Parthasarathy Gandeepan

Beilstein J. Org. Chem. 2021, 17, 2209–2259, doi:10.3762/bjoc.17.143

• . Notably, the photocatalytic conditions proved suitable for the benzylic C(sp3)−H and unactivated alkane cyclohexane C‒H arylations. The catalytic cycle is proposed to involve the oxidative addition of nickel(0) 4-IV into an aryl chloride 8a to form nickel(II) intermediate 4-V (Figure 4) [56]. The SET

• for the mode of action of this cascade arylation protocol (Figure 10) [73]. In the photocatalytic cycle, the SET event between the photoexcited iridium catalyst 10-II and the substrate oxalate 33 generates a tertiary carbon-centered radical 10-IV by decarboxylation and the reduced iridium(II

• ]. Notably, this method proceeds through a unique mechanism (Figure 18) involving five steps: i) anion exchange between the iridium catalyst and nickel catalyst; ii) generation of a bromine radical and nickel(I) species in the photocatalytic cycle; iii) hydrogen atom abstraction events between the bromine

On the application of 3d metals for C–H activation toward bioactive compounds: The key step for the synthesis of silver bullets

• Renato L. Carvalho,
• Amanda S. de Miranda,
• Mateus P. Nunes,
• Roberto S. Gomes,
• Guilherme A. M. Jardim and
• Eufrânio N. da Silva Júnior

Beilstein J. Org. Chem. 2021, 17, 1849–1938, doi:10.3762/bjoc.17.126

• has been selectively feasible without activating a C(sp2)–H bond in the arene moiety. Verma and co-workers [91] have reported the use of VO(acac)2 immobilized over graphitic carbon nitride (VO@gC3N4) under visible light irradiation to perform a photocatalytic C–H activation of arene methides and

Cerium-photocatalyzed aerobic oxidation of benzylic alcohols to aldehydes and ketones

• Girish Suresh Yedase,
• Sumit Kumar,
• Jessica Stahl,
• Burkhard König and
• Veera Reddy Yatham

Beilstein J. Org. Chem. 2021, 17, 1727–1732, doi:10.3762/bjoc.17.121

• herein report a mild aerobic photocatalytic oxidation of benzylic alcohols to aldehydes and ketones using 10 mol % CeCl3·7H2O (Scheme 1). Results and Discussion A variety of reaction parameters was tested during the optimization of the reaction with 4-iodobenzyl alcohol (1a) as the model substrate and

Heterogeneous photocatalytic cyanomethylarylation of alkenes with acetonitrile: synthesis of diverse nitrogenous heterocyclic compounds

• Guanglong Pan,
• Qian Yang,
• Wentao Wang,
• Yurong Tang and
• Yunfei Cai

Beilstein J. Org. Chem. 2021, 17, 1171–1180, doi:10.3762/bjoc.17.89

• .17.89 Abstract A visible light-mediated heterogeneous photocatalytic cyanomethylarylation of alkenes with acetonitrile has been established using K-modified carbon nitride (CN-K) as a recyclable semiconductor photocatalyst. This protocol, employing readily accessible alkyl N-hydroxyphthalimide (NHPI

• independently disclosed a photocatalytic cyanomethylarylation of N-aryl/benzoyl acrylamide for the synthesis of oxindoles and isoquinolinediones using diazonium salts and PIFA/1,3,5-trimethoxybenzene as radical initiators, respectively [29][30][31]. In this case, expensive Ru and 4CzIPN-based homogeneous

• conditions. Recently, we demonstrated K-modified carbon nitride (CN-K), a semiconductor material, exhibited a remarkably enhanced photocatalytic activity in the decarboxylative Giese reaction. The effect was due to its K-intercalated poly(heptazine)-based structure existing as small lamellar nanocrystallites

Insight into functionalized-macrocycles-guided supramolecular photocatalysis

• Minzan Zuo,
• Krishnasamy Velmurugan,
• Kaiya Wang,
• Xueqi Tian and
• Xiao-Yu Hu

Beilstein J. Org. Chem. 2021, 17, 139–155, doi:10.3762/bjoc.17.15

• , calixarenes, and pillararenes. This minireview not only summarizes the role that macrocycles play in photocatalytic reactions but also clarifies the photocatalytic mechanisms. Finally, the future research efforts and new pathways to apply macrocycles and supramolecular hybrid materials in photocatalysis are

• -dependent selective arrangement of one or two substrates within the cavity for photocatalysis. Therefore, this review will focus on: i) the role of the supramolecular system in mediating the photocatalytic selectivity, yield, and the rate of the photocatalytic products and ii) macrocycle-assisted hybrid

• materials that have been exploited for photocatalytic applications, including photocatalytic dye degradations and hydrogen evolution. To successfully perform supramolecular photocatalytic reactions, various photophysical and photochemical properties of the host–guest system need to be considered [4]: i) the

Dawn of a new era in industrial photochemistry: the scale-up of micro- and mesostructured photoreactors

• Emine Kayahan,
• Mathias Jacobs,
• Leen Braeken,
• Leen C.J. Thomassen,
• Simon Kuhn,
• Tom van Gerven and
• M. Enis Leblebici

Beilstein J. Org. Chem. 2020, 16, 2484–2504, doi:10.3762/bjoc.16.202

• the starting concentration, χa is the conversion, τ is the residence time, PSTY is the photocatalytic space time yield, and P is the lamp power. In this paper, together with photomicroreactors, larger-scale photoreactors that contain micro- and mesostructures will be discussed since the performance

• conditions and the kinetics of the selected reaction can lead to drastic changes in the PSTY. de Sá et al. combined external and internal numbering up in meso- and microchemical reactors of various sizes (Figure 3e). Photocatalytic degradations of methylene blue, rhodamine B, and phenol with TiO2 were

• photoreactor by using the photocatalytic oxidation of thiols to disulfides as a model reaction [9]. Two, four, and eight photomicroreactors, each having a 0.5 mm internal diameter and a 0.95 mL volume were connected in parallel by using T-junctions. The fluid is distributed in a tree-like structure. A stable

Recent developments in enantioselective photocatalysis

• Callum Prentice,
• James Morrisson,
• Andrew D. Smith and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

• contain an exhaustive list of all enantioselective photocatalytic reactions; however, this review does aim to cover the different strategies that have been developed [5][6][7][8][9][10][11][12][13][14][15][16]. There is a subset of reactions that achieve asymmetry via a stepwise photochemical process

• ]•+, with the latter oxidising 22 to give radical cation 22•+ and turn over the photocatalytic cycle. The radical cation 22•+ is then proposed to participate in a two-step electron and proton exchange process with [CoII] to give [H–CoIII] and iminium ion 24, likely via a [CoI] intermediate. [H–CoIII] can

• et al. (Scheme 41) [103]. The proposed mechanism implicates an oxidative quenching cycle using a sacrificial oxidant (TIPS-EBX), followed by a PCET step with hydrogen-bonded complex 260 to give chiral ion pair 260•, which completes the photocatalytic cycle. Subsequent enantioselective radical

Photosensitized direct C–H fluorination and trifluoromethylation in organic synthesis

• Shahboz Yakubov and
• Joshua P. Barham

Beilstein J. Org. Chem. 2020, 16, 2151–2192, doi:10.3762/bjoc.16.183

• for inducing different organic transformations under extremely mild conditions without threatening reagents and conditions [83][84][85]. There are three commonly observed and distinct mechanisms of photocatalytic activation [86] in the context of organic synthesis: i) Most reported photocatalytic

• properties and reactivity can be synthesized on an industrial scale (Scheme 3) [194]. 2.3 General mechanism of photosensitized C–H fluorination Generally, the mechanism of photocatalytic activation induced by energy transfer involves the simultaneous photoinduced electron exchange between the photosensitizer

• photocatalytic direct fluorination of unactivated C(sp3)–H bonds by employing Selectfluor® and anthraquinone (AQN, T1 = 61.9 kcal⋅mol−1) as a photosensitizer. Control experiments showed that, under their conditions, both light and AQN were necessary for the reaction to proceed. A variety of different compounds

When metal-catalyzed C–H functionalization meets visible-light photocatalysis

• Lucas Guillemard and
• Joanna Wencel-Delord

Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147

• , few examples have been reported in which the photoredox process modifies the oxidation state of a catalyst [55][56]. Subsequently, C–H activation protocols benefiting from mild photocatalytic reoxidation have spread rapidly [60][61][62]. In such a case, a photocatalyst (PC) is introduced in the

• elimination, producing a Co(I) species. Finally, the photoexcited eosin Y reoxidizes Co(I) to Co(II), while the photosensitizer is reoxidized by molecular oxygen, thus completing the overall catalytic process. In addition, a complementary strategy towards photocatalytic C–H annulation was disclosed by Rueping

• the naphthyl ring after an intramolecular electron transfer. In the meantime, the sulfonyl radical is generated by oxidation of the sulfinate substrate via the photocatalytic cycle with the Ru(bpy)3 catalyst and K2S2O8 (the direct oxidation of sulfinate by persulfate could also be envisioned

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

• irradiation. Herein, we review some important developments of heterogeneous photocatalytic materials and their application in flow reactors for sustainable organic synthesis. Further, the application of continuous flow heterogeneous photocatalysis in environmental remediation is briefly discussed to present

• transfer catalysis (EnT, Section 4.2). The final two subsections review the importance of HPCats in flow reactors for the photocatalytic remediation of wastewater (Section 4.3) and air pollution (Section 4.4), an increasingly significant area of research to prevent damage to the environment and human

• topic in 2019 alone (Figure 1A). The credit for the development of this field is often given to MacMillan [24], Yoon [25], and Stephenson [26], whose seminal papers in 2008 and 2009 elegantly demonstrated the photocatalytic ability of ruthenium–bipyridyl complexes to drive chemical reactions with

Photocatalyzed syntheses of phenanthrenes and their aza-analogues. A review

• Alessandra Del Tito,
• Havall Othman Abdulla,
• Davide Ravelli,
• Stefano Protti and
• Maurizio Fagnoni

Beilstein J. Org. Chem. 2020, 16, 1476–1488, doi:10.3762/bjoc.16.123

• Phenanthrenes and their aza-analogues have important applications in materials science and in medicine. Aim of this review is to collect recent reports describing their synthesis, which make use of radical cyclizations promoted by a visible light-triggered photocatalytic process. Keywords: phenanthrenes

• photocatalyst, have revolutionized the way chemists can arrive to important chemical scaffolds [24][25][26]. Indeed, the photocatalytic approach combines unparalleled mild conditions, due to the use of photons as traceless reagents that leave no residue behind [27][28], with the exploitation of rather

• construct the phenanthridine core, somophilic (radical) isocyanide addition [45][46][47] is probably the most adopted one, in view of the versatility and low cost of the starting substrates. Accordingly, several protocols for the synthesis under photocatalytic conditions of phenanthridines starting from 2

An overview on disulfide-catalyzed and -cocatalyzed photoreactions

• Yeersen Patehebieke

Beilstein J. Org. Chem. 2020, 16, 1418–1435, doi:10.3762/bjoc.16.118

• Yeersen Patehebieke School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China 10.3762/bjoc.16.118 Abstract Disulfides are versatile catalysts. They can be photocatalysts, hydrogen atom transfer (HAT) catalysts, cocatalysts, or initiators in photocatalytic reactions

• , mild, and chemoselective radical catalysts that deserve more attention. The present review highlights the recent progress in the field of disulfide-catalyzed and -cocatalyzed photocatalytic reactions for different reaction types. Keywords: cycloaddition; disulfide catalyst; isomerization; oxidation

Distinctive reactivity of N-benzylidene-[1,1'-biphenyl]-2-amines under photoredox conditions

• Shrikant D. Tambe,
• Kwan Hong Min,
• Naeem Iqbal and
• Eun Jin Cho

Beilstein J. Org. Chem. 2020, 16, 1335–1342, doi:10.3762/bjoc.16.114

• Shrikant D. Tambe Kwan Hong Min Naeem Iqbal Eun Jin Cho Department of Chemistry, Chung-Ang University, 84 Heukseok-ro, Dongjak-gu, Seoul 06974, Republic of Korea 10.3762/bjoc.16.114 Abstract A simple photocatalytic method was developed for the synthesis of unsymmetrical 1,2-diamines by the

• photocatalytic synthetic methods are mainly limited to aniline-based substrates and do not encompass aliphatic amines. We planned the synthesis of 1,2-diamine compounds having an aliphatic amine moiety by the intermolecular coupling of N-benzylidines with aliphatic amines that not only act as coupling partner

• , the cyclized product with the tethered phenyl ring proposed in Scheme 1c was not generated under any of the photocatalytic conditions evaluated. With the optimized conditions in hand, the generality of the transformations was investigated using a wide variety of phenyl-substituted N-benzylideneaniline

Photocatalytic trifluoromethoxylation of arenes and heteroarenes in continuous-flow

• Alexander V. Nyuchev,
• Ting Wan,
• Borja Cendón,
• Carlo Sambiagio,
• Job J. C. Struijs,
• Michelle Ho,
• Moisés Gulías,
• Ying Wang and
• Timothy Noël

Beilstein J. Org. Chem. 2020, 16, 1305–1312, doi:10.3762/bjoc.16.111

• , Road, North Chicago, Illinois 60064, United States of America 10.3762/bjoc.16.111 Abstract The first example of photocatalytic trifluoromethoxylation of arenes and heteroarenes under continuous-flow conditions is described. Application of continuous-flow microreactor technology allowed to reduce the

Oxime radicals: generation, properties and application in organic synthesis

• Igor B. Krylov,
• Stanislav A. Paveliev,
• Alexander S. Budnikov and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2020, 16, 1234–1276, doi:10.3762/bjoc.16.107

• dithionite was omitted. High yields were reached for both monosubstituted (products 113a,d,f,h) and disubstituted C=C bonds (products 113b,c,e,g). Aliphatic oximes also undergo this transformation in high yields (products 113c,g,h). The photocatalytic oxidative cyclization of β,γ-unsaturated oximes 114 was

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

• Stephanie G. E. Amos,
• Marion Garreau,
• Luca Buzzetti and
• Jerome Waser

Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103

• renaissance of photocatalysis. Since the early seminal reports [1][2][3][4], inspired by pioneering works in photochemistry [5][6][7], this field has attracted increasing attention, and organic chemists have developed a wide variety of photocatalytic reactions [8][9][10][11]. One of the reasons for this rapid

• central role in the rapid expansion of photocatalytic methods [12]. These catalysts typically absorb light in the blue region and promote different activation modes, including photoinduced electron transfer (PET) and energy transfer (EnT), which respectively lead to the formation of open-shell and

• found particularly illustrative. This report is therefore in no means comprehensive, and readers searching to gain deeper insight into photocatalytic processes and/or for an exhaustive coverage of applications should refer to more complete specialized reviews and books [26][27][28][29][30]. We hope this

A simple and easy to perform synthetic route to functionalized thienyl bicyclo[3.2.1]octadienes

• Dragana Vuk,
• Irena Škorić,
• Valentina Milašinović,
• Krešimir Molčanov and
• Željko Marinić

Beilstein J. Org. Chem. 2020, 16, 1092–1099, doi:10.3762/bjoc.16.96

• compound 12. Possible outcomes of future photocatalytic oxygenation reactions of new benzobicyclo[3.2.1.]octadienes. Supporting Information Supporting Information File 42: Experimental details, copies of spectra and X-ray crystallographic data. Acknowledgements The competent help by Jerome Le Cunff in

Recent applications of porphyrins as photocatalysts in organic synthesis: batch and continuous flow approaches

• Rodrigo Costa e Silva,
• Luely Oliveira da Silva,
• Aloisio de Andrade Bartolomeu,
• Timothy John Brocksom and
• Kleber Thiago de Oliveira

Beilstein J. Org. Chem. 2020, 16, 917–955, doi:10.3762/bjoc.16.83

• photoprocesses [9][10][11]. Additionally, it is possible to realize tuning in terms of chemical properties by changing substituents, thus producing robust, soluble or heterogeneous, readily available and low-cost photocatalysts. The mechanisms of the photocatalytic activities of porphyrins are similar to other

• , we have demonstrated that both porphyrins, in the excited state, are thermodynamically able to promote the first photooxidation step (Scheme 4B), however, the turnover of TPFPP+ to TPFPP is much more favored which justifies the acceleration of the photocatalytic cycle. In this protocol, the scope of

• products were obtained with good TON (up to 880) and high selectivity (91–99.5%), even though the aryl C–F bonds present a high bond dissociation energy (BDE) (Scheme 13). Using a similar photocatalytic system, 2-methyl-2,3-dihydrobenzofuran was produced by an intramolecular hydro-functionalization of

Aldehydes as powerful initiators for photochemical transformations

• Maria A. Theodoropoulou,
• Nikolaos F. Nikitas and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2020, 16, 833–857, doi:10.3762/bjoc.16.76

• highlighting organocatalytically-mediated reactions [7][8][9][10] with potential in the field of photoorganocatalysis. The power of metal-based photocatalysts is indisputable and can be pinpointed through the ease that they can catalyze difficult photocatalytic reactions, such as the decarboxylation of

• supported the energy transfer pathway. Thus, the proposed triplet sensitization mechanism of the photocatalytic ATRA reaction is depicted in Scheme 25. In 2016, Ji and co-workers developed a new photoredox cross-dehydrogenative coupling (CDC) method for the α-heteroarylation of amides (α to nitrogen, e.g

• solvent, the base, and the irradiation wavelength. Next, they investigated the reaction potential, with most aryl bromides and benzaldehydes tested being compatible to this transformation, affording the products in moderate to excellent yield. The proposed photocatalytic cycle starts with the excitation

Photocatalytic deaminative benzylation and alkylation of tetrahydroisoquinolines with N-alkylpyrydinium salts

• David Schönbauer,
• Carlo Sambiagio,
• Timothy Noël and
• Michael Schnürch

Beilstein J. Org. Chem. 2020, 16, 809–817, doi:10.3762/bjoc.16.74

• . Further investigations in this direction are ongoing in our labaratories. Kinetic profile for the benzylation of 1 to 3. Examples of photocatalytic C–C bond formation by nucleophilic trapping of a reactive THIQ intermediate. Benzylation of N-phenyl-THIQ. Benzylation of substituted N-arylTHIQs. Removal of

Recent advances in photocatalyzed reactions using well-defined copper(I) complexes

• Mingbing Zhong,
• Xavier Pannecoucke,
• Philippe Jubault and
• Thomas Poisson

Beilstein J. Org. Chem. 2020, 16, 451–481, doi:10.3762/bjoc.16.42

• authors precluded a possible photocatalytic process (path II). And indeed, even though from a comparison of the redox potential of [Cu(I)(dap)2]Cl and [Ru(bpy)3]Cl2, the latter should have been capable to promote the photocatalytic reaction, the ruthenium complex was unsuccessful. Hence, to explain the

• ) [25]. This copper-catalyzed photocatalytic reduction generated an aryl radical that was trapped with various allylating reagents. First, the phenyl radical generated from the corresponding diphenyliodonium salt was added to various allyl sulfones substituted in the 2-position. The products were

• the use of Ir or Ru complexes in this transformation led to the degradation of the reagents. As this process did not involve a photocatalytic pathway, it will not be discussed here. To explain the reaction outcome, based on literature data, the authors hypothesized a catalytic cycle involving [Cu(I

Photophysics and photochemistry of NIR absorbers derived from cyanines: key to new technologies based on chemistry 4.0

• Bernd Strehmel,
• Christian Schmitz,
• Ceren Kütahya,
• Yulian Pang,
• Anke Drewitz and
• Heinz Mustroph

Beilstein J. Org. Chem. 2020, 16, 415–444, doi:10.3762/bjoc.16.40

• cation radical Sens+• forms Sens back in the cycle. The system exhibited photocatalytic behavior with no big changes of absorption for 90 min under aerobic and anaerobic conditions. However, no polymerization occurred under air showing the inhibition of polymerization by oxygen [81]. This described