Synthesis of photo- and ionochromic N-acylated 2-(aminomethylene)benzo[b]thiophene-3(2Н)-ones with a terminal phenanthroline group

• Vladimir P. Rybalkin,
• Sofiya Yu. Zmeeva,
• Lidiya L. Popova,
• Irina V. Dubonosova,
• Olga Yu. Karlutova,
• Oleg P. Demidov,
• Alexander D. Dubonosov and
• Vladimir A. Bren

Beilstein J. Org. Chem. 2024, 20, 552–560, doi:10.3762/bjoc.20.47

• photoproducts 3a–c under the influence of irradiation was developed. We applied a modified procedure using a Sweko IP65 LED emitter that had been previously developed in our studies for similar tasks [30]. For this purpose, a suspension of a yellow solid 2a–c in acetonitrile was boiled for 10–15 s and then

• reaction occurred catalytically in the presence of HClO4. A special technique for the preparative synthesis of photoproducts was developed. For the first time in the course of studying N→O acylotropic migrations, O-acylated photoproducts were comprehensively characterized by IR, 1H and 13C NMR spectroscopy

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

• not be determined because it was not available in pure form on preparative scale. With the absorption data, specifically the molar extinction coefficients, obtained from the isolated benzo[c]quinolizinium derivatives, the yields of the initially formed photoproducts 3c, 3e, 3f, and 3g in the reaction

• mixtures were determined to be 78%, 73%, 30%, and 20% in MeCN, >97%, 80%, 44% and 55% in H2O, and 32%, 76%, 53% and 38% in Na phosphate buffer. Overall, the initially formed amounts of photoproducts are significantly larger than the ones of the isolated compounds, in the case of 3c and 3e even with good

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

• of the photoproducts (Table 2). Based on the structure of compound 11a we assumed that it could be converted into a polyaromatic product using conventional synthetic methods. However, the use of different systems (TsOH/toluene, HCl/EtOH, DBU/EtOH, MeONa/MeOH) resulted only in the decomposition of the

• -bottomed glass flask. Synthesis of photoproducts 12. Reaction conditions: method A) 10 (0.5 mmol), DMF (15 mL) irradiation for 48 h; method B) 1) 9 (0.5 mmol), DMF (15 mL), irradiation for 96 h; 2) CDI (1.75 mmol, 0.28 g), MeCN (5 mL), reflux, 2 h. Optimization of the condensation conditions.a Ratio of

• photoproducts 11 and 12.a Supporting Information Supporting Information File 42: Experimental procedures, characterization data of all products, copies of 1H, 13C NMR, HRMS spectra of all new compounds, and X-ray crystallographic data.

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

• complexes (1:1, 2:1, 1:2, and 2:2). For the 1:1, 2:1, and 1:2 host–guest complexes, the thermodynamic association (Ka) and dissociation constants (Kd) for the reactive guests and photoproducts are crucial for the fundamental understanding of supramolecular noncovalent interactions [12][13]. In addition

• , during the catalytic process, the reactive guest should have a greater binding affinity or the photoproducts should have the lowest binding affinity with the supramolecular host to avoid product inhibition, so as to produce a better catalytic turnover efficiency [14][15]. However, it is quite complicated

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

• given in Table 1. Synthesis of 7a,b. Photochemical reaction of 7a,b; a) solvent and conditions are given in Table 2. Conversion of ketene 10a to its methyl esters 11a,b. Chemical yields of the formation of photoproducts 4, 5 and 6. Result of photoreaction of 7a,b at various wavelengths in different

[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

• solutions containing 2 and AN, 3 and AN, or the corresponding complexes 2@β-CD and 3@β-CD with AN. Scheme 3 and Scheme 4 show products formed in the photochemical reactions, whereas ratio of photoproducts obtained is given in Table 2. The addition of H2O to the solution of 2 or 3 in CH3CN generally increase

• , but it did not quench the cycloaddition of 3AMY with AN. Thus, cycloadduct 11 was detected after irradiation of 3 with AN in CH3CN/H2O, but not when a base was added to the solution. Addition of β-CD did not affect the decarboxylation reaction, since the same conversion to photoproducts was observed

• CH2Cl2 (2 × 50 mL) and EtOAc (2 × 50 mL). The organic extracts were dried over anhydrous Na2SO4, and CH2Cl2 and EtOAc were combined. The solutions were filtered and the solvent was removed on a rotary evaporator. The photoproducts were separated by chromatography on semipreparative HPLC followed by

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

• [3.2.1]octadiene derivatives by irradiating the toluene solution of compound's 3–7 mixture of cis- and trans-isomers in the presence of iodine (Scheme 2 and Scheme 3). The electrocyclization reactions were successfully implemented in most cases and photoproducts 8–11 were obtained in moderate yields. The

• only exception was the cyano derivative 6 which was proven to be non-reactive, since the reaction mixture showed solely the presence of the initial cis- and trans-isomers. Figure 9 presents the 1H NMR spectra of photoproducts 8 and 9, in comparison to the spectra of the starting aldehyde 1. The effect

• the HRMS measurements is appreciated. Funding The University of Zagreb short term scientific support under the title “Synthesis and functionalization of novel (hetero)polycyclic photoproducts as cholinesterase inhibitors” is gratefully acknowledged.

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

• obtained photoproducts should not exhibit such a strong brownish color as observed in photochemical studies to explore the heptamethines 48 [63]. Nowadays, this arises as a big challenge to use such absorbers in applications where the color formed can be seen as an issue. Absorbers comprising indolium and

• with our findings where no formation of singlet oxygen was confirmed [89]. Other pathways request attention which could be formation of the O2-• radical to propose an alternative [90]. Such intermediates exhibit high reactivity resulting in similar photoproducts as disclosed for photoinduced electron

• photoproducts were formed and cationic photopolymerization even of epoxides succeeded with good conversions vide infra. Additional absorbers fitting in this scheme comprise at the meso-position alternative substituents such as Phenyl or Chlorine (see Table 1 for comparison). Surprisingly, this reaction has not

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

• latter compounds and check their photoproducts using UV spectrometry. Indeed, when they were irradiated in 1, 2, 5, 10, 15, 20, 25 and 30 min time intervals compound 12 showed the formation of an intermediate with λmax at 338 nm which gradually increased, probably indicating a one-way photochemical path

• . For the dissociation reaction of compound 12 in the triplet state, the molecule passes through a very small energy barrier and dissociates finally into its photoproducts which are the two ground state radicals indicated in Scheme 2. The almost negligible change in geometry on going from T1 min to T1

Reversible photoswitching of the DNA-binding properties of styrylquinolizinium derivatives through photochromic [2 + 2] cycloaddition and cycloreversion

• Sarah Kölsch,
• Heiko Ihmels,
• Jochen Mattay,
• Norbert Sewald and
• Brian O. Patrick

Beilstein J. Org. Chem. 2020, 16, 111–124, doi:10.3762/bjoc.16.13

• )bisquinolizinium 4b and 4c as photoproducts in quantitative yield. The products 4b and 4c were fully characterized by NMR spectroscopy (1H, 13C, COSY, HSQC, HMBC, and ROESY) and mass spectrometry, which revealed a cyclobutane structure, specifically by the appearance of the characteristic NMR signals of the

Photochemical generation of the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical from caged nitroxides by near-infrared two-photon irradiation and its cytocidal effect on lung cancer cells

• Ayato Yamada,
• Manabu Abe,
• Yoshinobu Nishimura,
• Shoji Ishizaka,
• Masashi Namba,
• Taku Nakashima,
• Kiyofumi Shimoji and
• Noboru Hattori

Beilstein J. Org. Chem. 2019, 15, 863–873, doi:10.3762/bjoc.15.84

• compound 2 with rapid radical recombination. Over 70% of the caged TEMPO 2a and ≈85% of 2b were recovered after 2 h of irradiation under degassed conditions. The retarded formation of TEMPO after 5 min of irradiation is due to the decrease in the relative absorbance of 2a to those of primary photoproducts

• . Photochemical generation of TEMPO radical. Synthesis of caged nitroxides 2a and 2b. Photochemical generation of TEMPO radical and photoproducts 6 and 7 under air atmosphere. Isodesmic reaction from BRa and 5b to 5a and BRb. Photophysical data for 2a, 2b, 5a, and 5b in benzene (DMSO). Supporting Information

The photodecarboxylative addition of carboxylates to phthalimides as a key-step in the synthesis of biologically active 3-arylmethylene-2,3-dihydro-1H-isoindolin-1-ones

• Ommid Anamimoghadam,
• Saira Mumtaz,
• Anke Nietsch,
• Gaetano Saya,
• Cherie A. Motti,
• Jun Wang,
• Peter C. Junk,
• Ashfaq Mahmood Qureshi and
• Michael Oelgemöller

Beilstein J. Org. Chem. 2017, 13, 2833–2841, doi:10.3762/bjoc.13.275

• crystalline solids in good to excellent yields of 63–95% (Table 2, entries 1–17). In many cases, the photoproducts 3 simply precipitated during irradiation or after removal of the co-solvent acetone and could be isolated by filtration. In all other cases, the desired products 3 were obtained after extraction

The chemistry and biology of mycolactones

• Matthias Gehringer and
• Karl-Heinz Altmann

Beilstein J. Org. Chem. 2017, 13, 1596–1660, doi:10.3762/bjoc.13.159

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

• photoproducts 4 and 5, respectively. By contrast, under the same conditions, 3 did not give rise to any isolable Ch-derived product. These results point to an intramolecular hydrogen abstraction in 1 and 2 from the C7 position of Ch and subsequent C–C coupling of the generated biradicals. Interestingly, 2 was

• singlet oxygen, thus being able to initiate Ch oxidation from their triplet excited states following either of the two competing mechanistic pathways. Keywords: aryl ketones; hydrogen abstraction; lipid peroxidation; photoproducts; triplet excited state; Introduction Among the constituents of cell

• unambiguous stereochemical assignment, authentic samples of 1 and 2 were prepared by direct esterification of (R)- and (S)-SP with α-Ch [17]. Steady-state photolysis In order to investigate photoproducts formation, steady-state irradiation of dichloromethane solutions (ca. 10−3 M) of 1–3 was performed under

Photochemical approach to functionalized benzobicyclo[3.2.1]octene structures via fused oxazoline derivatives from 4- and 5-(o-vinylstyryl)oxazoles

• Ivana Šagud,
• Simona Božić,
• Željko Marinić and
• Marija Šindler-Kulyk

Beilstein J. Org. Chem. 2014, 10, 2222–2229, doi:10.3762/bjoc.10.230

• , which are identified and characterized by spectroscopic methods. The photoproducts formed are relatively unstable and spontaneously or on silica gel undergo oxazoline ring opening followed by formation of formiato- or formamido-benzobicyclo[3.2.1]octenone derivatives. On irradiation of 4-(2-vinylstyryl

• formation of the photoproducts 8 and 10 can be explained by intramolecular cycloaddition and formation of resonance stabilized biradicals A/A’ followed by the 1,6-ring closure (Scheme 4). An 1,3-H shift, as in furan and thiophene derivatives [6], and rearomatization to fused oxazole derivatives B/B’ is not

Photorelease of phosphates: Mild methods for protecting phosphate derivatives

• Sanjeewa N. Senadheera,
• Abraham L. Yousef and
• Richard S. Givens

Beilstein J. Org. Chem. 2014, 10, 2038–2054, doi:10.3762/bjoc.10.212

• , however, the chromophore did not undergo the photo-Favorskii rearrangement, forming only the reduction product 2-acetyl-6-hydroxynaphthalene (6) in addition to other unidentified photoproducts (Scheme 5). These results paralleled our observations for 14a,b in aq MeCN. Finally, photolysis of 5,8-BQA

• intact or rearrange to more strongly absorbing chromophores which compete for the effective radiation wavelengths, often resulting in incomplete conversions that compromise their synthetic utility. These chromophores and especially their photoproducts are also highly fluorescent, which frequently prove

• are known to undergo nucleophilic substitution and not reduction to the methyl ketone products 6, 12 or 15 [38][39]. Substitution by solvent would trap the intermediate biradicaloid (or zwitterion) to form, in the case of 2,6-HNA, the α-methoxy ketone 42, which was not detected among the photoproducts

Photo, thermal and chemical degradation of riboflavin

• Muhammad Ali Sheraz,
• Sadia Hafeez Kazi,
• Sofia Ahmed,
• Zubair Anwar and
• Iqbal Ahmad

Beilstein J. Org. Chem. 2014, 10, 1999–2012, doi:10.3762/bjoc.10.208

• , 267, 373 and 444 nm in the UV and visible regions in aqueous solution and is degraded into various photoproducts on exposure to light [1]. These products include formylmethylflavin (FMF), lumichrome (LC), lumiflavin (LF), carboxymethylflavin (CMF), 2,3-butanedione, a β-keto acid and a diketo compound

• cyclodehydroriboflavin (CDRF) [21][30][35]. The structures of RF and its photoproducts are shown in Figure 1. FMF is an intermediate in the photodegradation of RF and is more sensitive to light than RF [15][16][17][27][32][33]. It is hydrolyzed to LC and LF [18][19][22][23][24][25][26][27][28][29][30][31][32][33] and is

• oxidized to CMF [20][27][32]. Both LC and LF are also sensitive to light, with LC having relatively better stability [36]. The nature of the photoproducts of RF depends on the reaction conditions such as solvent, pH, buffer kind and concentration, oxygen content, light intensity and wavelengths

Direct and indirect single electron transfer (SET)-photochemical approaches for the preparation of novel phthalimide and naphthalimide-based lariat-type crown ethers

• Dae Won Cho,
• Patrick S. Mariano and
• Ung Chan Yoon

Beilstein J. Org. Chem. 2014, 10, 514–527, doi:10.3762/bjoc.10.47

• corresponding polyether side chain containing the lariat-type azacrown ethers 47a–c exclusively (Scheme 11). As observed in earlier studies [34], the initially formed photoproducts undergo in situ dehydration to produce the vinyl sulfide products 46a–c [82]. The photoreactions shown in Scheme 10 and Scheme 11

Microflow photochemistry: UVC-induced [2 + 2]-photoadditions to furanone in a microcapillary reactor

• Sylvestre Bachollet,
• Kimitada Terao,
• Shin Aida,
• Yasuhiro Nishiyama,
• Kiyomi Kakiuchi and
• Michael Oelgemöller

Beilstein J. Org. Chem. 2013, 9, 2015–2021, doi:10.3762/bjoc.9.237

• ][7][8][9]. The narrow reaction channels guarantee efficient penetration of light and yield improved photonic efficiencies [10][11]. Likewise, the removal of the photoproducts from the irradiated area minimizes the risk of photodecompositions or secondary photoreactions [12][13]. Of the many

Topochemical control of the photodimerization of aromatic compounds by γ-cyclodextrin thioethers in aqueous solution

• Hai Ming Wang and
• Gerhard Wenz

Beilstein J. Org. Chem. 2013, 9, 1858–1866, doi:10.3762/bjoc.9.217

• a plausible way to enhance the reaction selectivity of the syn-HH dimer. The 1H NMR spectra of the crude photoproducts indeed showed a striking effect from changes in the salt concentration. The signals of the syn-HT and anti-HH isomers significantly diminished as shown in Figure 6. At a high salt

• , photoproducts are predictable by quantum mechanical optimization of the corresponding dimeric aggregates in vacuo. This work also showed that the addition of salt can further improve supramolecular control by suppression of the free photoactive species. Experimental General: Guests (ANT, ACE, and COU) and

• irradiation for 12 h at room temperature under a nitrogen atmosphere, the photoproducts formed were extracted with chloroform and then analyzed by 1H NMR [34]. No starting material was found anymore after this time of reaction. It is worth mentioning that a precipitate was formed after irradiation of the

High-spin intermediates of the photolysis of 2,4,6-triazido-3-chloro-5-fluoropyridine

• Sergei V. Chapyshev,
• Denis V. Korchagin,
• Patrik Neuhaus and
• Wolfram Sander

Beilstein J. Org. Chem. 2013, 9, 733–742, doi:10.3762/bjoc.9.83

• of the pyridine ring to give triplet mononitrenes 12 and 13 as the primary photoproducts. On further irradiation, quintet dinitrenes 15 and 16 and septet trinitrene 18 are formed. The maximum yield of the latter is about just 2%. Preferential photodissociation of the azido groups located in ortho

• triplet nitrenes 12–14 at the PBE/DZ level of theory. UB3LYP/6-311+G* orbital density in the LUMO of triazide 11 and CIS/6-311+G* orbital density in the highest singly occupied orbital of excited state 11a-S1*. Examples of selective photolysis of the azido groups. Possible photoproducts of triazide 11

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225

• fact we could only find two references describing photoreactions involving bisallenes. Thus, irradiation of the epoxide 197 in benzene-d6 (NMR experiment) yielded a plethora of photoproducts, among them two photodimers to which structure 198 was assigned by spectroscopic measurements (Scheme 47) [136

Photoreactions of cyclic sulfite esters: Evidence for diradical intermediates

• Rick C. White,
• Benny E. Arney Jr. and
• Heiko Ihmels

Beilstein J. Org. Chem. 2012, 8, 1208–1212, doi:10.3762/bjoc.8.134

• of cyclic carbonate esters such as 1b, as evidenced by the interception with appropriate trapping reagents; whereas the formation of persistent primary photoproducts has not been observed [13]. In contrast, we have found that under significantly milder photochemical conditions (3 h versus 15 h), the

Synthesis and photooxidation of styrene copolymer bearing camphorquinone pendant groups

• Branislav Husár,
• Norbert Moszner and
• Ivan Lukáč

Beilstein J. Org. Chem. 2012, 8, 337–343, doi:10.3762/bjoc.8.37

• subsequent reactions leading to photoproducts [21]. The rate-determining step in photoinitiation by CQ/amine is hydrogen transfer by the excited n→π* triplet state of the carbonyl group of CQ from the alkylamino group [8][9]. The photochemistry of the low molecular CQ in the polystyrene (PS) film was the

• transformation, an analogous study with low molecular CQ doped in a PS matrix was first performed. Elucidation of the structures of low molecular photoproducts was conveniently followed by spectral methods [22] and by isolation from the polymer matrix followed by spectral identification [21]. The results of the

•  3 according to the low molecular study [21] were formed to a much lesser extent. Since the phototransformation of CQ to 11 is not quantitative, n + m = 99.7; the remaining 0.3 consists of cyclopentenoic acids 14 and other unknown photoproducts. The increase of the molecular weight of MCQ/S during

Photochemical and thermal intramolecular 1,3-dipolar cycloaddition reactions of new o-stilbene-methylene-3-sydnones and their synthesis

• Kristina Butković,
• Željko Marinić,
• Krešimir Molčanov,
• Biserka Kojić-Prodić and
• Marija Šindler-Kulyk

Beilstein J. Org. Chem. 2011, 7, 1663–1670, doi:10.3762/bjoc.7.196

• ). The structure of the photoproducts was determined by spectroscopic methods. The molecular ions of 11 and 12, m/z 248 in the mass spectra, indicate that the structures have lost CO2 relative to the starting compound. In the 1H and 13C NMR spectra, the signals are found in an area which is

• spectra. Nevertheless, the proton H-5 of the fused benzene ring in structure 12 is in the multiplet together with other aromatic protons, which is in accordance with the proposed structure. The structure of the photoproducts was confirmed by an additional experiment on the crude reaction mixture with DDQ

• mixture of 11 and 12 along with decomposition and high-molecular-weight products. On shorter irradiation time (10 min, in benzene or acetonitrile) 3a (trans isomer) afforded, according to 1H NMR, the photomixture of predominantly 3b (cis isomer) with only traces of starting 3a and tricyclic photoproducts