Heterogeneous metallaphotoredox catalysis in a continuous-flow packed-bed reactor

• Wei-Hsin Hsu,
• Susanne Reischauer,
• Peter H. Seeberger,
• Bartholomäus Pieber and
• Dario Cambié

Beilstein J. Org. Chem. 2022, 18, 1123–1130, doi:10.3762/bjoc.18.115

• synthesis [3]. The adoption of flow chemistry ensured short photon path lengths and overcame issues related to scalability and productivity caused by the limited light penetration in large batch reactors (Lambert–Beer law), thereby making photocatalysis a promising option for industrially relevant processes

• . Results and Discussion Reactor assembly and model reaction We started our investigations by preparing a packed-bed reactor using a glass column (6.6 mm i.d., 100 mm length) that can be used in a dedicated setup for heterogeneous flow photocatalysis carried out in a commercial photochemical flow reactor

Synthesis of α-(perfluoroalkylsulfonyl)propiophenones: a new set of reagents for the light-mediated perfluoroalkylation of aromatics

• Durbis J. Castillo-Pazos,
• Juan D. Lasso and
• Chao-Jun Li

Beilstein J. Org. Chem. 2022, 18, 788–795, doi:10.3762/bjoc.18.79

• perfluorinated chains into aromatic rings have been developed since the first reports of such transformation by George Tiers in 1960, and McLoughlin and Thrower in 1969 [2][3]. Most approaches have made extensive use of organometallic chemistry, radical initiators, photocatalysis, electrochemistry, and more

Comparative study of thermally activated delayed fluorescent properties of donor–acceptor and donor–acceptor–donor architectures based on phenoxazine and dibenzo[a,j]phenazine

• Saika Izumi,
• Prasannamani Govindharaj,
• Anna Drewniak,
• Paola Zimmermann Crocomo,
• Satoshi Minakata,
• Leonardo Evaristo de Sousa,
• Piotr de Silva,
• Przemyslaw Data and
• Youhei Takeda

Beilstein J. Org. Chem. 2022, 18, 459–468, doi:10.3762/bjoc.18.48

• organic light-emitting diodes (OLEDs) by Adachi in 2012 [2], TADF-active compounds have emerged as emitters in high-performance organic light-emitting diodes (OLEDs) [3][4][5][6][7][8], biological probes [9], photocatalysis [10], and some others [11]. Specifically, TADF-active purely organic compounds

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

Earth-abundant 3d transition metals on the rise in catalysis

• Nikolaos Kaplaneris and
• Lutz Ackermann

Beilstein J. Org. Chem. 2022, 18, 86–88, doi:10.3762/bjoc.18.8

• . Applications of this strategy range from late-stage functionalization to modern photocatalysis and electrocatalysis, with contributions from around the globe, including Brazil, China, Japan, Germany, India, and South Korea, among others. The increasing use of C–H activations in academic and industrial

Recent advances and perspectives in ruthenium-catalyzed cyanation reactions

• Thaipparambil Aneeja,
• Cheriya Mukkolakkal Abdulla Afsina,
• Padinjare Veetil Saranya and
• Gopinathan Anilkumar

Beilstein J. Org. Chem. 2022, 18, 37–52, doi:10.3762/bjoc.18.4

• investigated the cyanation of differently substituted 7-azaindoles and achieved excellent results. They also succeeded in applying this strategy to N-aryl-α-carbolines to synthesize the respective cyanated N-aryl-α-carboline products. 3 Photocatalyzed cyanation reactions Nowadays photocatalysis has emerged as

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

• differences are discussed. Keywords: C–H functionalization; DABCO; HAT; photocatalysis; Introduction The functionalization of inert C–H bonds is a goal pursued by chemists from decades, due to its ubiquity in organic molecules. This strategy also dismisses tiresome protecting groups and functional group

• interchanging steps, often required in traditional synthetic methodologies [1][2]. The development of photocatalysis enabled inexpensive access to C–H activation methodologies under mild conditions, with hydrogen atom transfer (HAT) reactions standing out as a main strategy [1][3][4]. The hydrogen abstractor is

Polymer chemistry: fundamentals and applications

• Bernhard V. K. J. Schmidt

Beilstein J. Org. Chem. 2021, 17, 2922–2923, doi:10.3762/bjoc.17.200

• photocatalysis are employed in the development of new polymer materials in order to address specific applications. Overall, I hope the thematic issue “Polymer chemistry: fundamentals and applications” highlights the breadth of current polymer research and enables the reader to dive into this fascinating area of

Visible-light-mediated copper photocatalysis for organic syntheses

• Yajing Zhang,
• Qian Wang,
• Zongsheng Yan,
• Donglai Ma and
• Yuguang Zheng

Beilstein J. Org. Chem. 2021, 17, 2520–2542, doi:10.3762/bjoc.17.169

• widely investigated, because they are abundant and less expensive. This review discusses the scope and application of photoinduced copper-based catalysis along with recent progress in this field. The special features and mechanisms of copper photocatalysis and highlights of the applications of the copper

• complexes to photocatalysis are reported. Copper-photocatalyzed reactions, including alkene and alkyne functionalization, organic halide functionalization, and alkyl C–H functionalization that have been reported over the past 5 years, are included. Keywords: copper-photocatalyzed reactions; green chemistry

• ; mechanisms of copper photocatalysis; photoinduced copper-based catalysis; photoredox catalysis; special features of copper photocatalysis; Introduction Solar light is an inexhaustible and free energy source for green plants and bacteria. Photosynthetic organisms absorb solar energy and convert it into

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

• ]. In this review, we highlight the developments in C–H activation enabled by nickel photocatalysis. Review Arylation The arylation of C(sp3)‒H bonds constitutes a potential tool for the rapid diversification of simple organic molecules into valuable scaffolds [48][49][50][51][52]. In 2014, Doyle

• iridium photocatalysis/nickel catalysis enabled the α-C(sp3)–H acylation of ethers 9 with acid chlorides 45 (Scheme 38) [121]. The optimized catalytic conditions were not limited to acid chlorides as acyl sources, and an acid anhydride proved as viable substrate, albeit in a somewhat lower yield. Based on

• lower yields due to steric effects. The photoredox nickel-catalyzed C–H acylation was not limited to C(sp3)–H functionalization. Gu, Yuan and co-workers hence succeeded in preparing 3-acylindoles 88 from indole 86 and α-oxoacids 87 at room temperature by means of iridium photocatalysis and nickel

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

• photocatalysis has emerged as an alternative to the classical conventional synthetic methods to construct carbon–carbon and carbon–heteroatom bonds [34][35][36][37]. As a mild, efficient, and environmentally friendly approach it has the potential to unlock unique reactions that are previously inaccessible under

• thermal conditions. Significant advances were made for the oxidation of benzylic alcohols by using metal-based photocatalysts [38][39][40][41][42][43][44][45][46] and metal-free photocatalysis [47][48][49][50][51][52][53] in combination with various oxidants, such as TBHP and DDQ [54][55]. However, the

• benzylic alcohol selectively to the aldehyde or ketone is still desirable. Recently, cerium photocatalysis was introduced as a robust alternative to generate oxygen or carbon-centered radicals under mild reaction conditions [57][58][59][60][61][62][63][64]. CeCl3 reacts via ligand-to-metal charge transfer

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

• photocatalysis; recyclable; Introduction Nitrogenous heterocyclic compounds, such as indolines [1][2][3][4], oxindoles [5][6][7], isoquinolinones [8][9][10], and isoquinolinediones [11][12], are pivotal structural motifs in numerous pharmaceuticals, agrochemicals, and bioactive natural products. The oxidative

• illustrate the practicability of this CN-K-based heterogeneous photocatalysis protocol, a recycling procedure was established. The CN-K was recovered via simple centrifugation after the reaction and subsequently reused. As shown in Figure 1, the CN-K catalyst could be recycled at least five times without the

• reaction mixture and reused several times, illustrating the practicability of this heterogeneous photocatalysis protocol. Further applying this sustainable and environmentally friendly CN-K heterogeneous photocatalyst to realize other synthetic useful transformations is undergoing. Evaluation of catalyst

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

• , hydrophobic cavities, and specific guest recognition), they can provide a suitable environment to realize photocatalysis via noncovalent interactions with different substrates. In this minireview, we emphasized the photochemical transformation and catalytic reactivity of different guests based on the binding

• , 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

• also discussed. Keywords: host–guest chemistry; macrocycles; noncovalent interactions; supramolecular photocatalysis; Introduction Enzyme-catalyzed reactions are often carried out fantastically in nature via noncovalent interactions of a substrate [1][2]. Inspired by these natural processes, chemists

Synthesis of tetrafluorinated piperidines from nitrones via a visible-light-promoted annelation reaction

• Vyacheslav I. Supranovich,
• Igor A. Dmitriev and
• Alexander D. Dilman

Beilstein J. Org. Chem. 2020, 16, 3104–3108, doi:10.3762/bjoc.16.260

• photocatalyst activated by blue light. The annelation is a result of a radical addition at the nitrone, intramolecular nucleophilic substitution, and reduction of the N–O bond. Keywords: difluoroalkylation; nitrones; organofluorine compounds; photocatalysis; radical addition; Introduction Nitrogen-containing

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

• Kingdom 10.3762/bjoc.16.197 Abstract Enantioselective photocatalysis has rapidly grown into a powerful tool for synthetic chemists. This review describes the various strategies for creating enantioenriched products through merging enantioselective catalysis and photocatalysis, with a focus on the most

• recent developments and a particular interest in the proposed mechanisms for each. With the aim of understanding the scope of each strategy, to help guide and inspire further innovation in this field. Keywords: enantioenrichment; enantionselective catalysis; enantioselective photocatalysis

• ; photocatalysis; photochemistry; Introduction Enantioselective catalysis has become a central focus for organic synthetic chemistry, particularly since the Nobel prize was awarded to Sharpless, Knowles, and Noyori for their pioneering work in the field. In the last 15 years, photocatalysis has become a

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

• reactions. Keywords: C–H activation; energy transfer; fluorination; photocatalysis; photosensitization; visible light; Review 1 Introduction 1.1 Importance of direct C–H fluorination/trifluoromethylation and photosensitization in organic synthesis 1.1.1 Importance of fluorine atoms in organic molecules

• excitation of the target substrate, one solution is the use of visible-light-harvesting photocatalysts that transfer their excitation energy to the target substrate. Over the last few decades, the field of visible-light photocatalysis has proven itself as a highly effective, versatile and “green” strategy

• a chemical reaction (Scheme 2C). This mechanistic class of PS TTET reactions is the focus of our review. PRC and PHAT processes are commonly grouped under the umbrella term “photocatalysis” in the literature, while PS TTET processes are often referred to as “energy transfer” [86]. 1.1.4 PRC vs

Azo-dimethylaminopyridine-functionalized Ni(II)-porphyrin as a photoswitchable nucleophilic catalyst

• Jannis Ludwig,
• Julian Helberg,
• Hendrik Zipse and
• Rainer Herges

Beilstein J. Org. Chem. 2020, 16, 2119–2126, doi:10.3762/bjoc.16.179

• with 56% decoordination (trans isomer) is less efficient. At the other end of the scale, in acetone only 69% coordination (530 nm) and 75% decoordination (435 nm) is achieved. It should be noted that a high conversion to the inactive state (in photocatalysis as well as photopharmacology) is more

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

• last decade particular attention has been focused on two modern fields, C–H bond activation, and visible-light-induced photocatalysis. Couplings through C–H bond activation involve the use of non-prefunctionalized substrates that are directly converted into more complex molecules, without the need of a

• catalytic system is extremely appealing. In that perspective, the scope of this review aims to present innovative reactions combining C–H activation and visible-light induced photocatalysis. Keywords: C–H activation; C–H functionalization; dual catalysis; photoredox catalysis; radical chemistry

• –H activations, visible-light-induced photocatalysis, electrosynthesis, enzyme catalysis, and others. Each of these techniques aims at accessing complex molecules while limiting ecological footprint. Over the last decade, the metal-catalyzed C–H activation established itself as one of the most

Photoredox-catalyzed silyldifluoromethylation of silyl enol ethers

• Vyacheslav I. Supranovich,
• Vitalij V. Levin and
• Alexander D. Dilman

Beilstein J. Org. Chem. 2020, 16, 1550–1553, doi:10.3762/bjoc.16.126

• carbon–bromine bond. Keywords: difluoroalkylation; organofluorine compounds; photocatalysis; radical addition; silicon reagents; Findings Fluorinated silicon reagents have found widespread use for the introduction of fluorinated fragments [1][2][3][4][5]. Typically, these reagents work under strongly

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

• Christopher G. Thomson Ai-Lan Lee Filipe Vilela Institute of Chemical Sciences, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, EH14 4AS Scotland, United Kingdom 10.3762/bjoc.16.125 Abstract The synergy between photocatalysis and continuous flow chemical reactors

• 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

• interest to synthetic organic chemists who are considering applying heterogeneous photocatalysis (HPC) and flow chemistry in their research, and especially those who are already involved in one of the two areas. Many independent reviews have focused on individual types of HPCat materials [1][2][3][4][5][6

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

• ; phenanthridines; photocatalysis; radicals; visible light; Introduction Phenanthrenes are widely investigated compounds, due to the impressive number of diverse applications involving this scaffold, ranging from medicinal chemistry [1] to materials sciences, including their use in optoelectronics [2][3] and in

• inexpensive visible light (or sunlight, when possible) irradiation [29]. In general terms, photocatalysis smoothly gives access to reactive radical intermediates [30], mainly carbon-centered [31][32][33], or nitrogen-centered radicals [34][35]. In turn, these species have been extensively employed in radical

• Photocatalysis is an important tool for the generation and exploitation of reactive intermediates in synthesis. The versatility of this approach allows to form in a straightforward manner several carbon and nitrogen-based radicals useful to forge C–C or C–N bonds (frequently, in an intramolecular fashion) for

An overview on disulfide-catalyzed and -cocatalyzed photoreactions

• Yeersen Patehebieke

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

• ; photocatalysis; thiyl radical; Introduction Organic disulfides are often used as the skeleton for drugs, pesticides, rubber auxiliaries, polymers, and electronic materials [1]. Over the past decade, organic disulfide-involving photoreactions have attracted increasing attention. Disulfides have versatile

• , oxidations, or isomerizations, disulfides have increasingly proven their power. Herein, we briefly describe the progress in the field of disulfide-involving photocatalysis in recent years for different reaction types. Review Cycloaddition reactions As early as 1988, Feldman and co-workers reported an example

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

• . The developed method can be employed for the synthesis of various bulky vicinal diamines, which are potential ligands in stereoselective synthesis. Keywords: 1,2-diamine; diversity; imine; photocatalysis; visible light; Introduction The selective formation of distinct valuable compounds from the

• same starting material is a highly attractive divergent approach, though it represents significant synthetic challenges. Recent advances in visible-light photocatalysis, mediated by visible-light-absorbing photosensitizers, have allowed ready access to complex molecules in a controlled manner, where

• extensively explored under visible-light photocatalysis [10][11][12][13][14][15][16]. N-Benzylidenes can undergo facile single-electron reduction to generate α-amino radical intermediates, which can participate in diverse processes, depending upon the nature of the substrates and the reaction conditions

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

• -, nitrogen-, oxygen-, and sulfur-centered radicals, open-shell charged species, and sensitized organic compounds. Keywords: organic dyes; photocatalysis; photoredox catalysis; radicals; reactive intermediates; Review Introduction In the last decade, synthetic organic chemistry has experienced the

• 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

• , such as acridiniums (OD1–4), cyanoarenes (OD5–8), diaryl ketones (OD9/10), flavins (OD11/12), xanthenes (OD13–15), thiazines (OD16/17) and various other dyes, such as OD18–21, have been exploited (Figure 1), and the field of organic photocatalysis has been extensively covered by various reviews [16][19

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

• conjugated photosensitizers show increasing potential in photocatalysis since they combine both photo- and electrochemical properties which can substitute available metalloorganic photocatalysts. Batch and continuous-flow approaches are presented highlighting the relevance of enabling technologies for the

• renewal of porphyrin applications in photocatalysis. Finally, the reaction scale in which the methodologies were developed are highlighted since this is an important parameter in the authors’ opinion. Keywords: energy transfer; photocatalysis; photooxygenation; photoredox; porphyrins; Introduction In

• involving Ni complexes as catalysts, MacMillan and co-workers showed that Ni metallocatalysis can be successfully combined with photocatalysis (with Ir complexes) in a dual catalysis platform, which enables sp3–sp3 and sp2–sp3 bond formations [35]. In this context, metalloporphyrins emerge as an interesting