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

• for 2b in benzene. The cytocidal effect of compound 2a on lung cancer cells under photolysis conditions was also assessed to test the efficacy as anticancer agents. In a medium containing 100 μg mL−1 of 2a exposed to light, the number of living cells decreased significantly compared to the unexposed

• counterparts (65.8% vs 85.5%). Keywords: caged compound; nitroxide; photolysis; radical; theranostics; two-photon; Introduction Nitroxides (aminoxyl radicals) possess a delocalized unpaired electron and exhibit negligible dimerization reactivity, making them persistent open-shell species [1][2][3][4]. In

• %) for 2a, and 390 (70%) and 890 ps (30%) for 2b (Table 1, entries 1 and 2). For 2a and 2b, intermolecular charge transfer processes induced by the TEMPO moiety may account for the double-exponential decay curves to some extent. OP photolysis of 2a (5 mM) was first conducted in benzene at ≈298 K using

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

• methylcobalamin and adenosylcobalamin (coenzyme B12) that serve as organometallic cofactors in B12-dependent enzymes. The photolysis (thermolysis) of alkylcob(III)alamins leads to the formation of the corresponding alkyl radical and cob(II)alamin with homolytic Co(III)–C bond cleavage (Figure 1b). This high

Synthesis of aryl sulfides via radical–radical cross coupling of electron-rich arenes using visible light photoredox catalysis

• Amrita Das,
• Mitasree Maity,
• Simon Malcherek,
• Burkhard König and
• Julia Rehbein

Beilstein J. Org. Chem. 2018, 14, 2520–2528, doi:10.3762/bjoc.14.228

• (1,3,5-TMB•+) is formed indeed during the quenching process of the catalyst by 1,3,5-TMB (Scheme 5) ns-time-resolved transient absorption spectroscopy was used [50]. To allow for a decomposition of the multicomponent spectra we conducted laser flash photolysis (LFP) experiments on the single components

Semi-synthesis and insecticidal activity of spinetoram J and its D-forosamine replacement analogues

• Kai Zhang,
• Jiarong Li,
• Honglin Liu,
• Haiyou Wang and
• Lamusi A

Beilstein J. Org. Chem. 2018, 14, 2321–2330, doi:10.3762/bjoc.14.207

• spinosyn molecule interacts with both gamma-aminobutyric acid (GABA) receptor and nicotine acetylcholine (NACh) receptors [9]. Spinosad and spinetoram can be degraded via a combination of photolysis and microbial action, ultimately producing CO2, H2O, and nitrogen oxides [10]. That suggests that along with

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

• %. Further irradiation of hydrazones derived from furan-fused tricyclic diazocyclopentanediones culminates in the cycloelimination of furans to yield 2-N-(alkyl)hydrazone of cyclopentene-1,2,3-trione. By contrast, the direct photolysis of carbocyclic diazodiketones gives only Wolff rearrangement products

• Michler’s ketone, with different levels of triplet state energy were tested. Furthermore, to clearly demonstrate the difference of light-induced reactions of diazo compounds 1 in the triplet and singlet excited states, the direct photolysis of diazodiketones 1a-c without sensitizers was also examined

• formation of the appropriate hydrazones 2a–d,f and the most effective sensitizer for this reaction was found to be benzophenone. The direct photolysis of diazodiketones 1a–c was carried out by UV light (λ > 210 nm) in THF solution containing a small amount of H2O or MeOH to trap the proposed intermediate α

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

• -triene (78), and triplet 2-naphthylcarbene (79). Formation of allene 83 as an alternative carbene rearrangement product was not detected under the studied photolysis conditions (Scheme 14). Kitahara’s group reported the one-step synthesis of heptafulvalenes and benzoheptafulvalenes from monocyclic

• ], while the allenic rearrangement product 183 for the carbene 75 was not detected in the photolysis of a diazo compound (Scheme 33) [78]. 2,3-Benzotropone (12) was converted to gem-dichloride 187 to achieve diazirine as carbene precursor (Scheme 33) [77][144]. 3.2.2. Ring-expansion reactions via a tropone

Selective carboxylation of reactive benzylic C–H bonds by a hypervalent iodine(III)/inorganic bromide oxidation system

• Toshifumi Dohi,
• Shohei Ueda,
• Kosuke Iwasaki,
• Yusuke Tsunoda,
• Koji Morimoto and
• Yasuyuki Kita

Beilstein J. Org. Chem. 2018, 14, 1087–1094, doi:10.3762/bjoc.14.94

• electrophilic aromatic rings, non-acidic carbonyl groups, and suitable oxygen, nitrogen, and sulfur functionalities. Carbonyloxy radicals derived from typical hypervalent iodine(III) carboxylates by photolysis and other conditions [65][66][67][68] are known to undergo irreversible decarboxylation [69][70

Cobalt-catalyzed directed C–H alkenylation of pivalophenone N–H imine with alkenyl phosphates

• Wengang Xu and
• Naohiko Yoshikai

Beilstein J. Org. Chem. 2018, 14, 709–715, doi:10.3762/bjoc.14.60

• alkenylation reaction, affording the product 3aj with an E/Z ratio of 4:1. In our previous study on the C–H alkylation and arylation of pivalophenone N–H imines, we demonstrated that the pivaloyl imine readily undergoes fragmentation into a cyano group via an iminyl radical under peroxide photolysis or copper

• -catalyzed aerobic conditions [29]. Under the same peroxide photolysis conditions (t-BuOOt-Bu with UV (254 nm) irradiation), the ortho-alkenylated imine 3aa underwent a C–N bond-forming cyclization to afford the spirocyclic imine 4 in 81% yield (Scheme 4). The reaction likely involves the initial formation

Mannich base-connected syntheses mediated by ortho-quinone methides

• Petra Barta,
• Ferenc Fülöp and
• István Szatmári

Beilstein J. Org. Chem. 2018, 14, 560–575, doi:10.3762/bjoc.14.43

• , mutagenous properties were also shown. Freccero et al. examined the photogeneration by laser flash photolysis and reactivity of naphthoquinone methides as well as their activity as purine selective DNA alkylating agents [93]. Farrell et al. studied the mechanism of the cytotoxic action of naphthoquinone

• phenolic Mannich bases bearing functional groups that are suitable for cross-linking DNA; therefore, their antitumor effects could also be confirmed [96]. The formation of o-QMs and their biological properties were also illustrated by kinetic studies. Rokita et al. using laser flash photolysis showed that

Continuous multistep synthesis of 2-(azidomethyl)oxazoles

• Thaís A. Rossa,
• Nícolas S. Suveges,
• Marcus M. Sá,
• David Cantillo and
• C. Oliver Kappe

Beilstein J. Org. Chem. 2018, 14, 506–514, doi:10.3762/bjoc.14.36

• from vinyl azides through an azirine intermediate (Scheme 3). The process starts with the generation of the azirine from the vinyl azide by thermolysis. Formation of azirines from vinyl azides by photolysis and thermolysis in continuous flow has been previously described [38][39]. The azirine

Stimuli-responsive oligonucleotides in prodrug-based approaches for gene silencing

• Françoise Debart,
• Christelle Dupouy and
• Jean-Jacques Vasseur

Beilstein J. Org. Chem. 2018, 14, 436–469, doi:10.3762/bjoc.14.32

• deprotected under photolysis restoring the activity of the native siRNA. As stated previously, the introduction of a photoreactive moiety into the phosphodiester backbone of an ON with diazo compounds is not specific. Xiang et al. developed a more efficient and specific post-synthetic method. It is based on

Mechanochemical borylation of aryldiazonium salts; merging light and ball milling

• José G. Hernández

Beilstein J. Org. Chem. 2017, 13, 1463–1469, doi:10.3762/bjoc.13.144

• . Simultaneous neat grinding/irradiation of the reactants and the photocatalyst led to the formation of boronates in a molten state. On the other hand, the catalyst-free liquid-assisted grinding/irradiation reaction also led to product formation, featuring a direct photolysis pathway facilitated by substrate

• borylated product 3a. In addition to the 1H NMR analysis in solution, this result was confirmed by immediate ex situ analysis using IR spectroscopy of the solid reaction mixture, which revealed only the presence of both starting materials. Thereby, excluding a direct thermal [20][21] or photolysis pathway

• potential for switching the activation mode from a SET process to a direct heterolytic photolysis. Jacobi von Wangelin et al. noticed that the borylation product 3a could also occurred in the absence of eosin Y, upon irradiation of a MeCN solution of the reactants with white LEDs [23][25]. Pleasingly, LAG

Glycoscience@Synchrotron: Synchrotron radiation applied to structural glycoscience

• Serge Pérez and
• Daniele de Sanctis

Beilstein J. Org. Chem. 2017, 13, 1145–1167, doi:10.3762/bjoc.13.114

• that had been synthesized. They all included a substrate donor, either UDP-Gal or UDP-GalNAc with an additional group on the sugar or on the uracil. Photolysis at 100 K was monitored by UV–vis absorption, both in solution and in crystals in order to assess the efficiency of the laser ablation in the

Synthesis of 1-indanones with a broad range of biological activity

• Marika Turek,
• Dorota Szczęsna,
• Marek Koprowski and
• Piotr Bałczewski

Beilstein J. Org. Chem. 2017, 13, 451–494, doi:10.3762/bjoc.13.48

• /toluene for the Knoevenagel reaction or NaH/THF for the Horner–Witting reaction) (Scheme 43). Photochemical reactions play an important role in the synthesis of 1-indanone derivatives. Thus, photolysis of the ketone 149 gave the 1-indanone 150 in 94% yield. It is worth mentioning that photolysis of the

Unusual reactions of diazocarbonyl compounds with α,β-unsaturated δ-amino esters: Rh(II)-catalyzed Wolff rearrangement and oxidative cleavage of N–H-insertion products

• Valerij A. Nikolaev,
• Jury J. Medvedev,
• Olesia S. Galkina,
• Ksenia V. Azarova and
• Christoph Schneider

Beilstein J. Org. Chem. 2016, 12, 1904–1910, doi:10.3762/bjoc.12.180

• corresponding amides, are known in the literature [17][18][19][20][21][22][23][24][25]. It is believed that these reactions follow a usual scheme of thermolysis (or photolysis) of diazocarbonyl compounds with intermediate formation of ketenes, which further acylate N-nucleophiles presented in the reaction

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

• 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

• with reduction of the BZT chromophore. Dyads 1 and 2 were efficiently photolyzed under anaerobic conditions, whereas 3 was markedly unreactive. Interestingly, 2 was significantly more photoreactive than 1 indicating a clear stereodifferentiation in the photochemical behavior. Laser flash photolysis

• ammonium molybdate reagent. The residues were purified through silica gel 60 (0.063–0.2 mm). Exact mass was obtained by Waters ACQUITY™ XevoQToF spectrometer. Laser flash photolysis (LFP) measurements As described in [17], a pulsed Nd:YAG laser was used for the excitation at 355 nm. The single pulses were

Chiral cyclopentadienylruthenium sulfoxide catalysts for asymmetric redox bicycloisomerization

• Barry M. Trost,
• Michael C. Ryan and
• Meera Rao

Beilstein J. Org. Chem. 2016, 12, 1136–1152, doi:10.3762/bjoc.12.110

• exchange, and photolysis of 6 completes the synthesis of catalyst 1. Using this strategy, a variety of catalysts including p-tolyl, 2-naphthyl, 1-naphthyl, and tert-butyl sulfoxide complexes were all synthesized in an analogous fashion. This method has a distinct advantage over a traditional CpRu catalyst

Synthesis of 2,1-benzisoxazole-3(1H)-ones by base-mediated photochemical N–O bond-forming cyclization of 2-azidobenzoic acids

• Daria Yu. Dzhons and
• Andrei V. Budruev

Beilstein J. Org. Chem. 2016, 12, 874–881, doi:10.3762/bjoc.12.86

• 2,1-benzisoxazole-3(1H)-ones is reported. The optimization and scope of this cyclization reaction is discussed. It is shown that an essential step of the ring closure of 2-azidobenzoic acids is the formation and photolysis of 2-azidobenzoate anions. Keywords: aryl azides; azepinones; 2,1

• solvent dioxane with acetonitrile or THF did not affect the yield of the cyclization products. The photolysis of 1a (Scheme 1, intermediate A) resulted in low yields of 2a because of the competitive formation of reaction products. In the past, research has been focused on the formation of 2-substituted 3H

• -azepines 3 as products of the photolysis or thermolysis of aromatic azides [34][35]. The proposed mechanism for their formation was confirmed by identification of the reaction intermediates using low-temperature and time-resolved spectroscopy [36][37][38][39][40][41][42][43]. It is currently believed that

Interactions of cyclodextrins and their derivatives with toxic organophosphorus compounds

• Sophie Letort,
• Sébastien Balieu,
• William Erb,
• Géraldine Gouhier and
• François Estour

Beilstein J. Org. Chem. 2016, 12, 204–228, doi:10.3762/bjoc.12.23

• ). The α- and γ-CD respectively exhibit a slight promotive and inhibitive effect on the photolysis of both parathion and paraoxon, whereas a full reverse of reactivity is noticed with β-CD (inhibiting parathion photolysis but promoting paraoxon’s one). Following the same trend as for pesticide hydrolysis

• , the photolysis outcome is related to the inclusion depth of the pesticide within the CD cavity. For the paraoxon/β-CD complex, the inclusion depth remains moderate, which places the reactive phosphorus center close to the CD’s hydroxy groups. On the contrary, for the parathion/β-CD, paraoxon/γ-CD and

Copper-catalyzed aerobic radical C–C bond cleavage of N–H ketimines

• Ya Lin Tnay,
• Gim Yean Ang and
• Shunsuke Chiba

Beilstein J. Org. Chem. 2015, 11, 1933–1943, doi:10.3762/bjoc.11.209

• appropriate lower valent transition metals [28][29][30][31][32], electron-rich organic electron donors [33][34][35][36][37][38], or sensitized photolysis [39][40][41][42] (Scheme 1c). Although the oxidative generation of iminyl radicals has also been reported, only iminooxyacetic acids have been used as the

Synthesis, antimicrobial and cytotoxicity evaluation of new cholesterol congeners

• Mohamed Ramadan El Sayed Aly,
• Hosam Ali Saad and
• Shams Hashim Abdel-Hafez

Beilstein J. Org. Chem. 2015, 11, 1922–1932, doi:10.3762/bjoc.11.208

• II, were triggered to release bioactive coumarines by photolysis at 350 nm [14]. Dendrogenin A (DDA, III) is a natural metabolite in healthy mammals. It arises from conjugation of 5,6α-epoxycholesterol (5,6α-EC) with histamine. In vitro studies showed that DDA induced tumor cell re-differentiation

Star-shaped tetrathiafulvalene oligomers towards the construction of conducting supramolecular assembly

• Masahiko Iyoda and
• Masashi Hasegawa

Beilstein J. Org. Chem. 2015, 11, 1596–1613, doi:10.3762/bjoc.11.175

• hand, the conductivities of the corresponding neutral nanoobjects are determined by pulse-radiolysis or flash-photolysis time-resolved microwave conductivity techniques [48][49]. Current-sensing atomic force microscopy (CS-AFM) and combination of scanning tunneling microscopy and spectroscopy (STM/STS

Preparative semiconductor photoredox catalysis: An emerging theme in organic synthesis

• David W. Manley and
• John C. Walton

Beilstein J. Org. Chem. 2015, 11, 1570–1582, doi:10.3762/bjoc.11.173

• remove oxygen. Stirring is maintained during photolysis to keep the TiO2 particles evenly dispersed. With P25 catalyst, irradiation with two hemispherical banks of 15 W Cleo tubes (λ = 350 nm) (for example two face tanning units) is maintained at ambient temperature. For some surface-modified TiO2

• yields, but the coatings detached after about three usages. Lower conversions and yields resulted when photospheres, comprising hollow Pyrex beads coated with TiO2 [57], were employed; probably because of the difficulty in dispersing them evenly during photolysis. The standard P25 catalyst was re

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142