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

The chemical behavior of terminally tert-butylated polyolefins

• Dagmar Klein,
• Henning Hopf,
• Peter G. Jones,
• Ina Dix and
• Ralf Hänel

Beilstein J. Org. Chem. 2015, 11, 1246–1258, doi:10.3762/bjoc.11.139

• the photolysis is carried out under argon, only polymeric material is produced from 19 after extended irradiation (20 h). The structure of compound 4 in the crystal. Ellipsoids correspond to 30% probability levels. (a) The structure of compound 24 in the crystal. Ellipsoids correspond to 50

Come-back of phenanthridine and phenanthridinium derivatives in the 21st century

• Lidija-Marija Tumir,
• Marijana Radić Stojković and
• Ivo Piantanida

Beilstein J. Org. Chem. 2014, 10, 2930–2954, doi:10.3762/bjoc.10.312

• yields (up to 95%, Scheme 4). McBurney et al. prepared various N-heterocycles, using oxime carbonates as excellent precursors for the photoinduced generation of iminyl radicals, whereby at standard photolysis conditions, 3-substituted 6-methylphenanthridines were obtained in good to quantitative yields

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

• does not occur in aqueous acetonitrile although diethyl phosphate is released. Other substitution patterns on the naphthyl or quinolin-5-yl core, such as the 2,6-naphthyl 10 or 8-benzyloxyquinolin-5-yl 24 platforms, also do not rearrange by aryl migration upon photolysis and, therefore, do not proceed

• GTP) were among the first to be covalently bound to chromophores in a cage or PPG format that were demonstrably released upon photolysis. Benzoin caged cAMP and o-nitrophenethyl caged ATP, seminal examples of caged phosphates, are often the two classic caged biochemical substrates cited [6][7][8][9

• , temporal and concentration parameters for releasing substrates are controlled by adjusting the focus, time resolution, and intensity of the light source in conjunction with other variables such as the photochemical reactivity and molecular reaction pathway. Since photolysis reactions are generally

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

• aerobic and anaerobic conditions [11][14][15][18][20][21][23][24][25][26][27][28][29][30][31][32][33][34][35][65]. A number of studies have been conducted by employing different low and high intensity radiation sources emitting at different wavelengths in the UV and visible regions for the photolysis of

• photodegraded to LC whereas in alkaline media it forms LC along with LF. Both these major photoproducts are formed via the triplet excited state through the mediation of FMF, which serves as an intermediate in the photolysis of RF [10][11][18][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][59][78

• and 10.2 [78]. The rate of photolysis of RF depends on its ionization states and their susceptibility to excitation. Ahmad et al. [24] studied the kinetics of RF over a wide pH range of 1–12 and evaluated its effect on the rate of photolysis. They determined the optimum range for the stability of RF

Homogeneous and heterogeneous photoredox-catalyzed hydroxymethylation of ketones and keto esters: catalyst screening, chemoselectivity and dilution effects

• Axel G. Griesbeck and
• Melissa Reckenthäler

Beilstein J. Org. Chem. 2014, 10, 1143–1150, doi:10.3762/bjoc.10.114

• titanium species, photolysis at 254 and 300 nm, respectively, led only to trace amounts of the hydroxymethylation product 4 via a (triplet carbonyl) excited-state hydrogen-transfer process, obviously a sluggish process under these conditions (Table 1). In the presence of titanium complexes TiCln(OiPr)4−n

• and the (more reactive and easier oxidizable) hydroxymethyl radicals. As shown in Table 5, this is actually the case for the semiconductor particle TiO2 P25 catalysis. If acetophenone is added to the photolysis solution constantly over a period of 24 h, the absolute amount of hydroxymethylation

• the photolysis of TiO2 in the absence of additional acceptor compounds with formation of hydrogen and eventually formation of formaldehyde [46]. Both hydrogen and formaldehyde were also detected in our experiments by gas-phase analysis. Thus, higher amounts of hydroxymethyl radicals can be produced

On the mechanism of photocatalytic reactions with eosin Y

• Michal Majek,
• Fabiana Filace and
• Axel Jacobi von Wangelin

Beilstein J. Org. Chem. 2014, 10, 981–989, doi:10.3762/bjoc.10.97

• spectroscopic, synthetic, and apparative study has allowed a more detailed mechanistic rationalization of several recently reported eosin Y-catalyzed aromatic substitutions at arenediazonium salts. The operation of rapid acid–base equilibria, direct photolysis pathways, and radical chain reactions has been

• addition of the photocatalyst eosin Y, 54% yield of the borylation product were obtained by direct photolysis (Scheme 4). These observations are in full accord with a report of direct reaction of thermally generated aryl cations (from arenediazonium salts) with bispinacolato diboron to give the

• Deronzier from 1984 [32]. The significant overlap of the absorption spectra of the arenediazonium salt recorded before and after the addition of eosin Y (Figure 4) suggests that direct photolysis of the C–N bond could account for the erosion of product yield in the catalytic process due to competitive

Tailoring of organic dyes with oxidoreductive compounds to obtain photocyclic radical generator systems exhibiting photocatalytic behavior

• Christian Ley,
• Julien Christmann,
• Ahmad Ibrahim,
• Luciano H. Di Stefano and
• Xavier Allonas

Beilstein J. Org. Chem. 2014, 10, 936–947, doi:10.3762/bjoc.10.92

• of the complex kinetics underlying PCIS chemical reactions, allowing a better and simplest selection of chemicals combination. Results and Discussion In order to outline this behavior, the photochemical consumption of the dye (i.e., photolysis) was studied in a typical Type II and a 3-cpt PCIS based

• reaction. Thus, according to Beer–Lambert's law, the absorbance of the system decreases during the reaction: this bleaching could be followed by UV–visible absorption spectroscopy. The photolysis of an acetonitrile solution of RB/TA was done within a 1 cm width cell with a monochromatic 532 nm laser diode

• dye (see insert Figure 1). It should be noted that in the same conditions, no photolysis occurs for an acetonitrile solution of neat RB. To quantify the consumption of the PS, the photolysis quantum yield (Φphotolysis) was determined. Φphotolysis is defined by the ratio of the initial number of

Metal and metal-free photocatalysts: mechanistic approach and application as photoinitiators of photopolymerization

• Jacques Lalevée,
• Sofia Telitel,
• Pu Xiao,
• Marc Lepeltier,
• Frédéric Dumur,
• Fabrice Morlet-Savary,
• Didier Gigmes and
• Jean-Pierre Fouassier

Beilstein J. Org. Chem. 2014, 10, 863–876, doi:10.3762/bjoc.10.83

• -trapping, laser flash photolysis, steady state photolysis, cyclic voltammetry and luminescence experiments. Keywords: LEDs; photoinitiators; photopolymerization; photoredox catalysis; Introduction Photoredox catalysis is now well-known and largely used in organic synthesis, especially in the development

• panchromatic behavior in the 400–650 nm range. The PIC/Ph2I+/NVK system The photochemical properties of Ir(piq)2(tmd) A triplet-state lifetime of 1.1 μs has been determined for Ir(piq)2(tmd) by laser flash photolysis experiments. A relatively similar lifetime (1.3 μs) was previously measured for 3Ir(ppy)3 [68

• + interaction is also in line with a fast photolysis of the PIC observed during the irradiation of Ir(piq)2(tmd)/Ph2I+ (Figure 8). In ESR spin-trapping experiments on irradiated Ir(piq)2(tmd)/Ph2I+ in the presence of phenyl-N-tert-butylnitrone (PBN), phenyl radicals are also detected (Figure 9). In the presence

The chemistry of amine radical cations produced by visible light photoredox catalysis

• Jie Hu,
• Jiang Wang,
• Theresa H. Nguyen and
• Nan Zheng

Beilstein J. Org. Chem. 2013, 9, 1977–2001, doi:10.3762/bjoc.9.234

• lend support to some of the key steps in the catalytic cycle. An oxygen uptake experiment showed that 0.75 equiv of O2 was consumed for the complete conversion of N-phenyltetrahydroisoquinoline 13. This data strongly supports the role of O2 as the stoichiometric oxidant. Flash photolysis studies

Damage of polyesters by the atmospheric free radical oxidant NO₃^•: a product study involving model systems

• Catrin Goeschen and
• Uta Wille

Beilstein J. Org. Chem. 2013, 9, 1907–1916, doi:10.3762/bjoc.9.225

• are initially required in the polyester to promote further degradation on a large scale through chain and other processes. Reaction of polyester-model compounds 1–3 with NO3• from CAN photolysis Study of the products formed in the reaction of NO3• obtained from CAN photolysis provides the opportunity

• these systems. Thus, CAN photolysis generates NO3• in the presence of excess NO3−, which acts as Brønsted base and mediates deprotonation of the initial radical cation 3•+ to give benzyl radical 7 [23], followed by transformation to the products 4–6. In the NO2•/O3 system, on the other hand, [NO3−] = [3

• % acetonitrile within 2–3 hours. UV detection was performed at λ = 214 and 230 nm. Purity was assessed by analytical RP HPLC on an SGE Protecol C18 5 μM 250 × 4.6 mm column. Reactions with NO3• from CAN photolysis In a typical experiment 1.0 mmol of the model substrate and 4.0 mmol of CAN were dissolved in 5 and

[3 + 2]-Cycloadditions of nitrile ylides after photoactivation of vinyl azides under flow conditions

• Stephan Cludius-Brandt,
• Lukas Kupracz and
• Andreas Kirschning

Beilstein J. Org. Chem. 2013, 9, 1745–1750, doi:10.3762/bjoc.9.201

• of 2H-azirines 2 under inductive heating and photochemical conditions. The experiments were conducted at a concentration of 0.05 M. Optimization of the photolysis of vinyl azide 1a and trapping of nitrile ylide with acrylonitrile 4a under flow conditions. Supporting Information Supporting