Photochemically assisted synthesis of phenacenes fluorinated at the terminal benzene rings and their electronic spectra

• Yuuki Ishii,
• Minoru Yamaji,
• Fumito Tani,
• Kenta Goto,
• Yoshihiro Kubozono and
• Hideki Okamoto

Beilstein J. Org. Chem. 2025, 21, 670–679, doi:10.3762/bjoc.21.53

• fluorination on the electronic features of phenacene molecules. F8-Phenacenes were conveniently synthesized by the Mallory photoreaction of the corresponding fluorinated diarylethenes as the key step. Upon fluorination on the phenacene cores, the absorption and fluorescence bands of the F8-phenacenes in CHCl3

• , most likely due to different crystalline packing motifs. Keywords: fluorescence; fluorinated aromatics; phenacene; photoreaction; Introduction Polycyclic aromatic hydrocarbons (PAHs) have been subject of continuous interest not only from aspects of fundamental synthetic, structural, and physical

• . In this study, octafluorinated phenacenes, F8-phenacenes F8PIC, F8FUL, and F87PHEN (see Figure 1 for their chemical structures), were systematically synthesized via the Mallory photoreaction [46] as the key step, and their UV–vis and fluorescence spectra were investigated in comparison with those of

Unprecedented visible light-initiated topochemical [2 + 2] cycloaddition in a functionalized bimane dye

• Metodej Dvoracek,
• Brendan Twamley,
• Mathias O. Senge and
• Mikhail A. Filatov

Beilstein J. Org. Chem. 2025, 21, 500–509, doi:10.3762/bjoc.21.37

• irradiation conditions. Inefficient intersystem crossing (or complete lack thereof) and short singlet-state lifetimes can both affect the efficiency of a photoreaction [20]. Crystal packing Similar to Cl2B, the potentially reactive double bonds in Me2B are coplanar and parallel, with a torsion angle of 0(0

Photomechanochemistry: harnessing mechanical forces to enhance photochemical reactions

• Francesco Mele,
• Ana M. Constantin,
• Andrea Porcheddu,
• Raimondo Maggi,
• Giovanni Maestri,
• Nicola Della Ca’ and
• Luca Capaldo

Beilstein J. Org. Chem. 2025, 21, 458–472, doi:10.3762/bjoc.21.33

• cost for photomechanochemical reactions. However, its primary limitation lies in the manual operation and the separation of the grinding and photoreaction steps. This approach affects the reproducibility of the reaction, as it depends on the energy applied by the operator. Moreover, it is time

• the adopted Zn-plated steel balls could also relieve any stress that builds up in the solid as a result of the photoreaction. In 2014, the MacGillivray group resorted to liquid-assisted vortex grinding (LAVG) to broaden the applicability of vortex grinding (Scheme 5) [68]. The authors reported that

Effect of substitution position of aryl groups on the thermal back reactivity of aza-diarylethene photoswitches and prediction by density functional theory

• Misato Suganuma,
• Daichi Kitagawa,
• Shota Hamatani and
• Seiya Kobatake

Beilstein J. Org. Chem. 2025, 21, 242–252, doi:10.3762/bjoc.21.16

• which the photogenerated isomers are thermally unstable at room temperature and return to the initial isomers not only by photoreaction but also by the thermal back reaction, are utilized for eyeglass lenses [43], security inks [44], and real-time holograms [45]. Especially, it is important to control

Extension of the π-system of monoaryl-substituted norbornadienes with acetylene bridges: influence on the photochemical conversion and storage of light energy

• Robin Schulte,
• Dustin Schade,
• Thomas Paululat,
• Till J. B. Zähringer,
• Christoph Kerzig and
• Heiko Ihmels

Beilstein J. Org. Chem. 2024, 20, 3061–3068, doi:10.3762/bjoc.20.254

• , such as absorption in the range of the solar spectrum, a high quantum yield of the photoreaction, long half-lives of the photoproducts, and a high energy storage density [7][8][12][13][14]. In this context, several different MOST systems have been explored, including, for example, anthracenes [15

• derivatives during the photoreaction, whereas the blue-shifted maximum of the photoproduct was formed. In addition, isosbestic points were observed for the derivatives 1h (A), 1i (B), 1k (D), and 1l (E). The irradiations of the derivatives 1h, 1i, 1k, and 1l were stopped once no more changes of the absorbance

• spectra were observed. In the case of compounds 1j and 1n, the endpoint of the photoreaction could not be identified, as a steady decrease of the whole absorption spectra during irradiation indicated secondary decomposition reactions. We previously reported triplet energy transfer between 3[Ru(phen)3](PF6

Development of a flow photochemical process for a π-Lewis acidic metal-catalyzed cyclization/radical addition sequence: in situ-generated 2-benzopyrylium as photoredox catalyst and reactive intermediate

• Masahiro Terada,
• Zen Iwasaki,
• Ryohei Yazaki,
• Shigenobu Umemiya and
• Jun Kikuchi

Beilstein J. Org. Chem. 2024, 20, 1973–1980, doi:10.3762/bjoc.20.173

• continues to flow and the reaction can be quenched immediately when necessary, the decomposition of an unstable product under the reaction conditions can be avoided [22][23][24][25]. Furthermore, when a photoreaction is performed in a flow system, there is an advantage that the light irradiation efficiency

A fiber-optic spectroscopic setup for isomerization quantum yield determination

• Anouk Volker,
• Jorn D. Steen and
• Stefano Crespi

Beilstein J. Org. Chem. 2024, 20, 1684–1692, doi:10.3762/bjoc.20.150

• monochromatic light). In line with the findings of Ladányi et al., the precision of Φtrans→cis is generally better than the precision for the reverse photoreaction. This difference in precision could be attributed to the trans→cis reaction being more dominant, especially for irradiation in the π→π* band, where

Ring opening of photogenerated azetidinols as a strategy for the synthesis of aminodioxolanes

• Henning Maag,
• Daniel J. Lemcke and
• Johannes M. Wahl

Beilstein J. Org. Chem. 2024, 20, 1671–1676, doi:10.3762/bjoc.20.148

• effect on product formation, potentially by changing the substrate’s conformation. Ring opening Based on its outstanding performance in the photoreaction, we selected Ts-protected azetidinol 3a as our preferred substrate to test ring-opening reactions. However, initial attempts were met with limited

• acids. Comparison of the effect of structural variations on the photoreaction. Supporting Information Supporting Information File 2: Experimental procedures, characterization data and copies of NMR spectra. Acknowledgements Generous support from the Johannes Gutenberg-Universität Mainz is acknowledged

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

• Information File 1). A remarkable turnover number of 4440 was achieved when 1 M stilbene was used (see Supporting Information File 1 for more information). Furthermore, the photocatalyst was utilized in a photosensitized cyclization reaction of cinnamyl chloride [84]. This photoreaction was originally

Photochromic derivatives of indigo: historical overview of development, challenges and applications

• Gökhan Kaplan,
• Zeynel Seferoğlu and
• Daria V. Berdnikova

Beilstein J. Org. Chem. 2024, 20, 228–242, doi:10.3762/bjoc.20.23

• ) and N,N'-dimethyl-5,5',7,7'-tetrabromoindigo (12) showed similar photochemical isomerization in the chloroalkane solvents. Additionally, a slow photoreaction in benzene was detected for compound 12 [40]. 11 years later, Margerum and co-workers investigated the photochromic behavior of 11a and 12 using

• the photoreaction, is advantageous for applications in bulk materials because the photoisomers have decreased absorbance at the excitation wavelength [9]. Depending on the substitution pattern, the quantum yields for the E–Z photoisomerization of indigo photochromes vary from 0.001 to 0.46 and the

Photoinduced in situ generation of DNA-targeting ligands: DNA-binding and DNA-photodamaging properties of benzo[c]quinolizinium ions

• Julika Schlosser,
• Olga Fedorova,
• Yuri Fedorov and
• Heiko Ihmels

Beilstein J. Org. Chem. 2024, 20, 101–117, doi:10.3762/bjoc.20.11

• general, the absorption maximum of the derivatives 2b–g decreased during the photoreaction with formation of new red-shifted absorption bands. Nevertheless, the new red-shifted absorption band of the amino-substituted styryl derivative 2b in MeCN was weak and very broad, indicating only negligible

• formation of different intermediates in the reaction sequence starting with E–Z isomerization, followed by photocyclization and subsequent oxidation. In general, the photoreaction was more efficient in polar, protic aqueous solvents (cf. Supporting Information File 1, Figures S2B–S6B) or in buffer solution

• as optimal efficiencies for the formation of photocyclization products. But even under these optimized conditions, compounds 3c–g could be isolated only in low yields of <5–21%. Hence, to assess whether the products are generally formed to minor extent in the photoreaction or whether the low yields

Controlling the reactivity of La@C₈₂ by reduction: reaction of the La@C₈₂ anion with alkyl halide with high regioselectivity

• Yutaka Maeda,
• Saeka Akita,
• Mitsuaki Suzuki,
• Michio Yamada,
• Takeshi Akasaka,
• Kaoru Kobayashi and
• Shigeru Nagase

Beilstein J. Org. Chem. 2023, 19, 1858–1866, doi:10.3762/bjoc.19.138

• 39, 42, 5, and 5%, respectively, and that of 1c gave 2c–5c in yields of 34, 33, 16, and 10%, respectively, based on the consumption of La@C2v-C82 (see Supporting Information File 1, Figures S2–S6). For the comparison, the photoreaction of the La@C2v-C82 anion with 1a was performed in ODCB using a

• high-pressure mercury arc lamp (cutoff < 350 nm, 1 h). The HPLC profile after the photoreaction indicates that several products other than 2a–5a were present (Figure 2c), similar to the photoreaction of La@C2v-C82 with 1a (Figure 2d). A previous study reported that the reaction of La@C2v-C82 with

Synthesis of substituted 8H-benzo[h]pyrano[2,3-f]quinazolin-8-ones via photochemical 6π-electrocyclization of pyrimidines containing an allomaltol fragment

• Constantine V. Milyutin,
• Andrey N. Komogortsev,
• Boris V. Lichitsky,
• Mikhail E. Minyaev and
• Valeriya G. Melekhina

Beilstein J. Org. Chem. 2023, 19, 778–788, doi:10.3762/bjoc.19.58

• shown that for the hydroxy derivatives the main pathway of phototransformation is a 6π-electrocyclization of the 1,3,5-hexatriene system and subsequent [1,9]-H sigmatropic shift leading to dihydrobenzo[h]pyrano[2,3-f]quinazolines. At the same time, for methylated analogues the photoreaction proceeds in

• that an alternative option for blocking ESIPT-induced processes for allomaltol derivatives is the use of DMF as a solvent [24]. Based on this fact, we assumed that the photoreaction in DMF would also allow the conversion of the starting pyrimidines 9 into the corresponding polycycles 12. However, the

• photoreaction can be carried out for starting compounds with both donor and acceptor substituents in the aryl fragment. However, it is interesting to note that the UV irradiation of thiophene containing pyrimidines 9g and 10g leads to a complicated mixture of unidentified products. Probably, this is due to

A study of the photochemical behavior of terarylenes containing allomaltol and pyrazole fragments

• Constantine V. Milyutin,
• Andrey N. Komogortsev,
• Boris V. Lichitsky and
• Valeriya G. Melekhina

Beilstein J. Org. Chem. 2022, 18, 588–596, doi:10.3762/bjoc.18.61

• -phenylenediamine. The general method for the preparation of the corresponding quinoxalines on the basis of the aforementioned condensation was implemented. It was demonstrated that the studied photoreaction does not depend on the type of pyrazole bridge. The structures of three of synthesized products were

• complex mixture of products. At the same time the blocking of ESIPT-processes by the modification of the hydroxy group allows one to direct the photoreaction exclusively to the pathway of 6π-electrocyclization of the 1,3,5-hexatriene system. Thus, the study of the photochemical properties of similar

• (Scheme 1D). In contrast to the previously described phototransformation of analogously substituted oxazolones 9, in the considered case, the photoreaction proceeds exclusively as a contraction of the pyranone ring, while 6π-electrocyclization of the hexatriene system was not observed. Results and

Borylated norbornadiene derivatives: Synthesis and application in Pd-catalyzed Suzuki–Miyaura coupling reactions

• Robin Schulte and
• Heiko Ihmels

Beilstein J. Org. Chem. 2022, 18, 368–373, doi:10.3762/bjoc.18.41

• , which usually indicates the formation of the corresponding quadricyclane 6b [10][11][12][29][36]. In addition, the isosbestic points, that developed upon superposition of the spectra obtained during the photoreaction, clearly indicated that only two absorbing species were present in the reaction mixture

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

• [28][50], Cu(dap)Cl2 acted as a potential precatalyst in this photoreaction. Upon irradiation, the CuII complex undergoes homolytic cleavage of a Cu–Cl bond forming CuI as the catalytically active species; thus, the CuII complex is the precatalyst and provides a more efficient transformation than CuI

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

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

• bimolecular photoreaction quantum yield in an isotropic medium, and iii) the substrate and the products should be released from the supramolecular system via a dynamic exchange, which directs to a better yield and catalytic efficiency. To strengthen the above concepts, supramolecular photocatalysis needs a

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

• platform for enhancing the photoreaction rates and easier scale-up. One of the hurdles in scaling up of photoreactors is the lack of a consensus on a benchmark to compare different scales and geometries. The simplest benchmark is the apparent rate constant kapp [12][13][14][15] shown in Equation 1. where

• energy efficiency. In addition, the solvent should not absorb light strongly nor be a quencher of the photoreaction. In order to avoid excessive heating of the light source, cooling systems might be necessary. The distribution of light inside the reactor brings a lot of complexity into the design. Since

• characterizing and deciding on the operational conditions of a photoreactor when a specific photoreaction is to be scaled up. The flow and light need to be distributed properly to all units of the microstructured reactors while scaling up in order to ensure the same reaction conditions everywhere. For multiphase

Formation of an exceptionally stable ketene during phototransformations of bicyclo[2.2.2]oct-5-en-2-ones having mixed chromophores

• Asitanga Ghosh

Beilstein J. Org. Chem. 2020, 16, 2297–2303, doi:10.3762/bjoc.16.190

• distribution of these photoproducts may be wavelength dependent [7]. In order to investigate the photoreaction of such enones, we observed a complete 1,2-acyl shift (1,2-AS) photoproduct formation when 1a–h have been irradiated (Scheme 1) [14][16]. We also observed that such a rearrangement took place very

• (characteristic of β,γ-enone moiety) and the type-B path (characteristic of an α,β-enone moiety). However, with the help of the photoinduced electron transfer (PET) reaction of 1a,c,d,g–h and photoreaction of the partially olefinated product of 1c,d,h, we have recognized that in a mixed α,β- and β,γ-enone system

• ]. Photoreaction of 7a and 7b Irradiation of a degassed solution of 7a,b in benzene at 254 nm for 3–4 h yielded a pale yellow solid of ketene 10a,b (Scheme 5, Table 2) through regioselective photoinduced 1,5-phenyl migration and we did not obtain any 1,2-AS or any other photoproduct. The same ketenes were isolated

Recent synthesis of thietanes

• Jiaxi Xu

Beilstein J. Org. Chem. 2020, 16, 1357–1410, doi:10.3762/bjoc.16.116

• photoreaction of N-methylthiosuccinimide (236) with 2,3-dimethylbut-2-ene (215a) gave rise to a mixture of thietane and oxetane derivatives 238 and 239, with thietane 238 as the major component. However, the reaction of the aromatic counterpart, N-methylmonothiophthalimide (237a) with olefins 215a and 186b

• 264 formed preferably, in the reaction of 256 with ethyl vinyl ether (215e) and propen-2-ylbenzene (186a). Notably, the photoreaction of 2,4-dithiobarbiturate 257 and 2,3-dimethylbut-2-ene (215a) produced exclusively the 4-thietane derivative 265 in 91% yield. 2,4,6-Trithiobarbiturate 258 reacted with

[3 + 2] Cycloaddition with photogenerated azomethine ylides in β-cyclodextrin

• Margareta Sohora,
• Leo Mandić and
• Nikola Basarić

Beilstein J. Org. Chem. 2020, 16, 1296–1304, doi:10.3762/bjoc.16.110

• cycloadducts. On the other hand, upon photolysis in the presence of H2O and a base, the photoreaction is about twenty times more efficient, but it delivers simple decarboxylation product 4 only. Attempts to use β-CD to complex both reactants and enhance the efficiency for the cycloaddition failed. In the

Cation-induced ring-opening and oxidation reaction of photoreluctant spirooxazine–quinolizinium conjugates

• Phil M. Pithan,
• Sören Steup and
• Heiko Ihmels

Beilstein J. Org. Chem. 2020, 16, 904–916, doi:10.3762/bjoc.16.82

• photoreaction [12][15][16]. The photochromism is based on a reversible electrocyclic reaction that proceeds through the UV light-induced cleavage of the C2’–O bond of the closed, colorless form to give the colored, metastable merocyanine form, whereas the back reaction can be initiated thermally or by the

A method to determine the correct photocatalyst concentration for photooxidation reactions conducted in continuous flow reactors

• Clemens R. Horn and
• Sylvain Gremetz

Beilstein J. Org. Chem. 2020, 16, 871–879, doi:10.3762/bjoc.16.78

• overcome the difficulties that occur upon scale-up. The most desirable approach for industrial-scale reactions is described by the quote “the best approach to the scale-up of a photoreaction seems to be the enlarging of a laboratory-type prototype reactor, with the important parameters being changed as

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

• , to the amide 83, as shown in Scheme 22. The low yield of the amide formation was attributed mainly to a concurrent imine formation, which was catalyzed by benzoic acid formed as a result of benzaldehyde (8) oxidation during the photoreaction. There was also a competition between two bimolecular