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

• catalysts in both oxidative and reductive quenching. The use of porphyrins as a photosensitizer for singlet oxygen generation is presented in the second topic, which was subdivided into two sections: pericyclic reactions and heteroatom oxidations. The first section describes the use of singlet oxygen in

• novelty (Scheme 33) [81]. They have also used TPP (immobilized acidic form) as photosensitizer and were able to produce up to 2.4 g of artemisinin per batch. The importance of artemisinin for Big Pharma has been confirmed during the last 20–30 years with many relevant publications. As mentioned before

• amides (71–99% yields) and with 5–66% ee (Scheme 42). In 2018, Meng and co-workers developed a bifunctional photo-organocatalyst combining both the photosensitizer and the chirality inducer. Relevant enantiomeric excesses were observed (up to 86% ee) in the oxidation of both β-keto esters and β-keto

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

• , proved to be completely inactive as the photosensitizer. Also, no reaction was observed when salicylaldehyde (68) was employed as a photosensitizer, despite of a triplet state energy of ≈70 kcal/mol, most probably due to an internal hydrogen bond (Scheme 16). As mentioned before, in the section on the

• precatalyst, 4,4’-di-tert-butyl-2,2’-bipyridyl (dtbbpy) as the ligand for the nickel catalyst, benzaldehyde (8) as the photosensitizer and hydrogen abstractor, K2HPO4 as the base, and UV-A light for the excitation of 8. The reaction mixture was placed under a N2 atmosphere and irradiated for 72 h. Their

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

Visible-light-induced addition of carboxymethanide to styrene from monochloroacetic acid

• Kaj M. van Vliet,
• Nicole S. van Leeuwen,
• Albert M. Brouwer and
• Bas de Bruin

Beilstein J. Org. Chem. 2020, 16, 398–408, doi:10.3762/bjoc.16.38

• photosensitizer. Because the use of polar solvents did not lead to the desired reactivity, we turned to nonpolar solvents. Since [Cu(dap)2]Cl is insoluble in nonpolar solvents, we continued with the more reducing fac-[Ir(ppy)3] photocatalyst. The choice of benzene as a solvent led to a significant formation of

p-Pyridinyl oxime carbamates: synthesis, DNA binding, DNA photocleaving activity and theoretical photodegradation studies

• Panagiotis S. Gritzapis,
• Panayiotis C. Varras,
• Nikolaos-Panagiotis Andreou,
• Katerina R. Katsani,
• Konstantinos Dafnopoulos,
• George Psomas,
• Zisis V. Peitsinis,
• Alexandros E. Koumbis and
• Konstantina C. Fylaktakidou

Beilstein J. Org. Chem. 2020, 16, 337–350, doi:10.3762/bjoc.16.33

• action via its combination with the photosensitizer. It is worth mentioning that, mainly in dermatology, even UVB irradiation is considered of therapeutic use [16][17][18]. Besides the anticancer activities of photosensitizers [19][20][21], “post-antibiotic era” is experimenting with photosensitizers as

• at 365 nm in the absence of AP (wells 3–7), nevertheless in the presence of the photosensitizer they are able to cause DNA photocleavage around 50% (wells 9–13). AP itself is inactive towards DNA, under the experimental conditions (well 8). Finally, we have used triplet energy quenchers such as

Excited state dynamics for visible-light sensitization of a photochromic benzil-subsituted phenoxyl-imidazolyl radical complex

• Yoichi Kobayashi,
• Yukie Mamiya,
• Katsuya Mutoh,
• Hikaru Sotome,
• Masafumi Koga,
• Hiroshi Miyasaka and
• Jiro Abe

Beilstein J. Org. Chem. 2019, 15, 2369–2379, doi:10.3762/bjoc.15.229

• acts as a singlet photosensitizer for PIC by the Dexter-type energy transfer. Visible-light sensitized photochromic reactions of PIC are important for expanding the versatility of potential applications to life sciences and materials science. Keywords: biradical; energy transfer; photochromism

• similar to other radical dissociation-type photochromic molecules such as HABI and pentaarylbiimidazole (PABI) [33][34][35]. Therefore, if we could substitute a singlet photosensitizer unit to PIC, the visible-light sensitivity could be achieved by singlet–singlet energy transfer. The visible-light

• sensitization of PIC expands the versatility of the rate-tunable photoswitches of PIC systems. In this study, we synthesized a novel PIC derivative conjugated with a visible-light photosensitizer (Benzil-PIC, Scheme 1) and investigated the excited state dynamics. We used a benzil framework as a photosensitizer

Fluorescent phosphorus dendrimers excited by two photons: synthesis, two-photon absorption properties and biological uses

• Anne-Marie Caminade,
• Artem Zibarov,
• Eduardo Cueto Diaz,
• Aurélien Hameau,
• Maxime Klausen,
• Kathleen Moineau-Chane Ching,
• Jean-Pierre Majoral,
• Jean-Baptiste Verlhac,
• Olivier Mongin and
• Mireille Blanchard-Desce

Beilstein J. Org. Chem. 2019, 15, 2287–2303, doi:10.3762/bjoc.15.221

• photosensitizer injection. Conclusion The modularity of the synthesis of phosphorhydrazone dendrimers enables the incorporation of TPA fluorophores everywhere in their structure. Classically, the TPA fluorophores can be used as terminal functions of the dendrimers. Less classically, they can be used as core of

α-Photooxygenation of chiral aldehydes with singlet oxygen

• Dominika J. Walaszek,
• Magdalena Jawiczuk,
• Jakub Durka,
• Olga Drapała and
• Dorota Gryko

Beilstein J. Org. Chem. 2019, 15, 2076–2084, doi:10.3762/bjoc.15.205

• , 4) as an organocatalyst and meso-tetraphenylporphyrin (H2TPP, 5) as a photosensitizer followed by in situ reduction with NaBH4, proceeded similarly to the reported results for simple, achiral aldehydes giving the desired diols 6–8 in 31–41% yields with moderate conversion and alcohols 9–11 as

Synthesis, photophysical and electrochemical properties of pyridine, pyrazine and triazine-based (D–π–)₂A fluorescent dyes

• Keiichi Imato,
• Toshiaki Enoki,
• Koji Uenaka and
• Yousuke Ooyama

Beilstein J. Org. Chem. 2019, 15, 1712–1721, doi:10.3762/bjoc.15.167

• ][18][19][20][21][22][23][24], and a promising photosensitizer for dye-sensitized solar cells (DSSCs) [25][26][27][28][29][30][31][32][33][34]. Thus, in this work, to gain insight into the photophysical and electrochemical properties of D–π–A fluorescent dyes with an azine ring as electron-withdrawing

Complexation of a guanidinium-modified calixarene with diverse dyes and investigation of the corresponding photophysical response

• Yu-Ying Wang,
• Yong Kong,
• Zhe Zheng,
• Wen-Chao Geng,
• Zi-Yi Zhao,
• Hongwei Sun and
• Dong-Sheng Guo

Beilstein J. Org. Chem. 2019, 15, 1394–1406, doi:10.3762/bjoc.15.139

• photosensitizer and thus improve the photovoltaic conversion efficiency [65]. Conclusion In summary, we have investigated the complexation behavior of GC5A with several classical luminescent dyes and analyzed their complexation-induced photophysical changes. GC5A affords strong binding (106–108 M−1) to all dyes

Synthesis and biological investigation of (+)-3-hydroxymethylartemisinin

• Toni Smeilus,
• Farnoush Mousavizadeh,
• Johannes Krieger,
• Xingzhao Tu,
• Marcel Kaiser and
• Athanassios Giannis

Beilstein J. Org. Chem. 2019, 15, 567–570, doi:10.3762/bjoc.15.51

• containing methylene blue as photosensitizer was exposed to sunlight and oxygen. The treatment of the resulting intermediate hydroperoxide with a small amount of trifluoroacetic acid as previously described [17][18], afforded in the frame of a Hock cleavage (+)-3-hydroxymethyl-9-desmethylartemisinin (16) in

Organometallic vs organic photoredox catalysts for photocuring reactions in the visible region

• Aude-Héloise Bonardi,
• Frédéric Dumur,
• Guillaume Noirbent,
• Jacques Lalevée and
• Didier Gigmes

Beilstein J. Org. Chem. 2018, 14, 3025–3046, doi:10.3762/bjoc.14.282

• species are produced, a wide range of monomers can be polymerized via a free radical or a cationic mechanism (anionic mechanisms are still rare) [8]. A PI can also be used in combination with a photosensitizer (PS) to extend the spectral sensitivity to longer wavelengths. The development of new

Learning from B₁₂ enzymes: biomimetic and bioinspired catalysts for eco-friendly organic synthesis

• Keishiro Tahara,
• Ling Pan,
• Toshikazu Ono and
• Yoshio Hisaeda

Beilstein J. Org. Chem. 2018, 14, 2553–2567, doi:10.3762/bjoc.14.232

• also described, with a focus on radical-involved reactions in terms of organic synthesis. Keywords: dehalogenation; electrolysis; green chemistry; heptamethyl cobyrinate; methyl transfer; 1,2-migration; photosensitizer; vitamin B12; Review 1. Introduction 1-1. Redox and coordination chemistry of B12

• reaction of H2bpdc, Ru(bpy)2Cl2, and a zinc source under solvothermal conditions (bpy = 2,2′-bipyridine, Scheme 5) [41]. The molecular photosensitizer [Ru(bpy)3]2+ was incorporated into the MOF through adsorption to form Ru@MOF, accompanied by a color change. Furthermore, 1 was effectively immobilized on

• water) could reduce 1 to form Co(I) species upon irradiation with ultraviolet (UV) light. We also reported a visible-light-driven system with a molecular photosensitizer such as Ru(bpy)32+ [39][40][102][103], cyclometalated iridium(III) complexes [104], and organic red dyes [105][106][107]. 4-2

Bioinspired cobalt cubanes with tunable redox potentials for photocatalytic water oxidation and CO₂ reduction

• Zhishan Luo,
• Yidong Hou,
• Jinshui Zhang,
• Sibo Wang and
• Xinchen Wang

Beilstein J. Org. Chem. 2018, 14, 2331–2339, doi:10.3762/bjoc.14.208

• . Besides the CO2 reduction performance of the molecular complexes was evaluated by cooperation with a ruthenium photosensitizer Ru(bpy)32+ (bpy = 2’,2-bipyridine) with visible light irradiation [61][62][63][64][65][66][67]. As shown in Figure 5b, the activity of the CO2 reaction is reduced with the

• after 3 h reaction in each case is due to photobleaching of the used dye photosensitizer. Moreover, after water oxidation and CO2 reduction reactions, the structures of 1-CN and 1-OMe were studied by 1H NMR spectroscopy, and no obvious changes were observed compared with the fresh samples (Supporting

Novel photochemical reactions of carbocyclic diazodiketones without elimination of nitrogen – a suitable way to N-hydrazonation of C–H-bonds

• Liudmila L. Rodina,
• Xenia V. Azarova,
• Jury J. Medvedev,
• Dmitrij V. Semenok and
• Valerij A. Nikolaev

Beilstein J. Org. Chem. 2018, 14, 2250–2258, doi:10.3762/bjoc.14.200

• sensitizers’ efficiency in this reaction (Table 2) one can conclude [41][52], that the energy of the triplet excited states 3T1 of diazodiketones 1 are about 68 kcal/mol. This provides a possible explanation why the use of Michler’s ketone was found to be ineffective as a photosensitizer in the process. The

β-Hydroxy sulfides and their syntheses

• Mokgethwa B. Marakalala,
• Edwin M. Mmutlane and
• Henok H. Kinfe

Beilstein J. Org. Chem. 2018, 14, 1668–1692, doi:10.3762/bjoc.14.143

• ]. Treatment of the thiol-ene 113 with the radical initiator 2,2-dimethoxy-2-phenylacetophenone (DPAP) and the photosensitizer 4-methoxyacetophenone (MAP) in DMF ensued to the formation of the thiyl radical 114 that underwent intramolecular cyclization to provide a mixture of biologically important thiosugars

Visible light-mediated difluoroalkylation of electron-deficient alkenes

• Vyacheslav I. Supranovich,
• Vitalij V. Levin,
• Marina I. Struchkova,
• Jinbo Hu and
• Alexander D. Dilman

Beilstein J. Org. Chem. 2018, 14, 1637–1641, doi:10.3762/bjoc.14.139

• addition step cannot be oxidized by photocatalysts. Herein we report a convenient method for performing hydroperfluoroalkylation of electron-deficient alkenes employing iodides 1 mediated by visible light. The reaction proceeds without the use of a photosensitizer or a photocatalyst. Generation of

Photocatalytic formation of carbon–sulfur bonds

• Alexander Wimmer and
• Burkhard König

Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4

• , trifluoromethyl groups and halides, but iodides led to polymer formation. Li and Wang developed a method for the α-C(sp3)–H thiolation of ethers, using Acridine Red as photosensitizer and tert-butyl hydroperoxide (TBHP) as oxidant (Scheme 38) [73]. They reported that photoexcited Acridine Red performs an energy

Dialkyl dicyanofumarates and dicyanomaleates as versatile building blocks for synthetic organic chemistry and mechanistic studies

• Grzegorz Mlostoń and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2017, 13, 2235–2251, doi:10.3762/bjoc.13.221

• [16]. However, the most efficient method for the synthesis of dialkyl dicyanomaleates Z-1 is the photochemical isomerization of the corresponding E-isomers. The reaction is performed in dichloromethane [17] and in the presence of benzophenone [18][19] or 1,4-dicyanobenzene [20] as photosensitizer. The

Chiral phase-transfer catalysis in the asymmetric α-heterofunctionalization of prochiral nucleophiles

• Johannes Schörgenhumer,
• Maximilian Tiffner and
• Mario Waser

Beilstein J. Org. Chem. 2017, 13, 1753–1769, doi:10.3762/bjoc.13.170

• (tetraphenylporphyrin) as a photosensitizer has recently been reported to proceed with satisfying selectivities by the groups of Meng and Gao [114][115]. In their first report [114], they made use of the classical cinchona catalyst A5 together with catalytic amounts of TPP under irradiation with a 100 W halogen lamp

Chemical systems, chemical contiguity and the emergence of life

• Terrence P. Kee and
• Pierre-Alain Monnard

Beilstein J. Org. Chem. 2017, 13, 1551–1563, doi:10.3762/bjoc.13.155

• ]. Such vesicles with associated ribozymes could eventually prove to be novel functional chemical systems. The production of fatty acids from non-amphiphilic picolylesters performed using a photochemical reaction involving a ruthenium tris(bipyridine), functioning as photosensitizer and redox catalyst

• reconstitute photosynthetic machinery in phospholipid liposomes [91][92] and polymersomes [93]. In these experiments, the use of photosensitizer triads or bacteriorhodopsin has allowed for the conversion of light energy into a proton gradient, which in turn could be utilized to power an ATP synthase to produce

• during system preparation was still necessary and it speaks against a separate evolution of the system parts. In the case of fatty acid experiments [90], fatty acid vesicles were formed on/around titanium oxide particles and the irradiation of the photosensitizer powered the reduction of NAD+ to NADH

Novel β-cyclodextrin–eosin conjugates

• Gábor Benkovics,
• Damien Afonso,
• András Darcsi,
• Szabolcs Béni,
• Sabrina Conoci,
• Éva Fenyvesi,
• Lajos Szente,
• Milo Malanga and
• Salvatore Sortino

Beilstein J. Org. Chem. 2017, 13, 543–551, doi:10.3762/bjoc.13.52

• successfully utilized in photodynamic therapy (PDT). This minimally invasive therapeutic approach has proven to be very well-suited for cancer and bacterial diseases treatment. The PDT is based on the combination of three main components: visible light, a photosensitizer (PS) and molecular oxygen [4][5]. After

A self-assembled cyclodextrin nanocarrier for photoreactive squaraine

• Ulrike Kauscher and
• Bart Jan Ravoo

Beilstein J. Org. Chem. 2016, 12, 2535–2542, doi:10.3762/bjoc.12.248

• ; squaraine; Introduction Photodynamic therapy (PDT) has become a very attractive alternative to traditional cancer therapies due to its efficiency and selectivity [1][2][3][4]. PDT is based on a photosensitizer (PS), which is delivered to cancerous tissue followed by the irradiation with light of an

Rearrangements of organic peroxides and related processes

• Ivan A. Yaremenko,
• Vera A. Vil’,
• Dmitry V. Demchuk and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

Biradical vs singlet oxygen photogeneration in suprofen–cholesterol systems

• Fabrizio Palumbo,
• Francisco Bosca,
• Isabel M. Morera,
• Inmaculada Andreu and
• Miguel A. Miranda

Beilstein J. Org. Chem. 2016, 12, 1196–1202, doi:10.3762/bjoc.12.115

• light. The latter involves energy transfer from the photosensitizer triplet excited state to ground state molecular oxygen [5][6]. Ketoprofen (KP) is a nonsteroidal anti-inflammatory drug that contains the benzophenone (BZP, Figure 1) chromophore and displays a n,π triplet excited state [7][8][9