Tandem Hock and Friedel–Crafts reactions allowing an expedient synthesis of a cyclolignan-type scaffold

• Viktoria A. Ikonnikova,
• Cristina Cheibas,
• Oscar Gayraud,
• Alexandra E. Bosnidou,
• Nicolas Casaretto,
• Gilles Frison and
• Bastien Nay

Beilstein J. Org. Chem. 2024, 20, 162–169, doi:10.3762/bjoc.20.15

• ]. Results and Discussion To test the feasibility of this reaction sequence, the aromatic substrate 1 readily accessible by the prenylation of commercial diethyl benzylmalonate [21] was first used. The photooxygenation of 1 was performed in CH2Cl2 in the presence of methylene blue (MB) as a photosensitizer

Optimizing reaction conditions for the light-driven hydrogen evolution in a loop photoreactor

• Pengcheng Li,
• Daniel Kowalczyk,
• Johannes Liessem,
• Mohamed M. Elnagar,
• Dariusz Mitoraj,
• Radim Beranek and
• Dirk Ziegenbalg

Beilstein J. Org. Chem. 2024, 20, 74–91, doi:10.3762/bjoc.20.9

• . However, the mixing time outside of the draft tube shows a clear dependence on the stirring speed. As expected, both sides of the reactor show an almost identical mixing behavior. Data for a stirring speed of 430 rpm shows pronounced fluctuation. This is because not the whole methylene blue solution is

• with 460 mL deionized water. The stirrer motor was then turned on with an appropriate rotational speed. When a steady hydrodynamic state was reached in the reactor, 5 mL of a 0.8 g L‒1 methylene blue solution was injected at the top surface of water at the top of the reactor. To ensure reproducibility

• and comparability, the methylene blue solution was always rapidly injected at the same spot using a syringe with a large opening. The tracer injection time was kept constant throughout the experiment at 1.2 s. The coloring of the solution was monitored with a video camera (Sony ZV-1). The video was

Preparation of β-cyclodextrin/polysaccharide foams using saponin

• Max Petitjean and
• José Ramón Isasi

Beilstein J. Org. Chem. 2023, 19, 78–88, doi:10.3762/bjoc.19.7

• carbon has been developed by Ma et al. [26], by the production of chitosan–saponin gels thanks to glutaraldehyde crosslinking. After adding potassium hydroxide, they freeze-dried the material and pyrolyzed the product. The resulting material possess a high absorption capacity of methylene blue, thanks to

Redox-active molecules as organocatalysts for selective oxidative transformations – an unperceived organocatalysis field

• Elena R. Lopat’eva,
• Igor B. Krylov,
• Dmitry A. Lapshin and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2022, 18, 1672–1695, doi:10.3762/bjoc.18.179

• ][29] and specialized on the specific types of organophotoredox catalysts, such as quinone derivatives [30][31], carbon nitrides [32][33], eosin [34][35][36], 4CzIPN [37][38], Bodipy derivatives [39], methylene blue [40], pyrylium salts [41], and perylene diimides [42]. Photochemical processes

Photophysical, photostability, and ROS generation properties of new trifluoromethylated quinoline-phenol Schiff bases

• Inaiá O. Rocha,
• Yuri G. Kappenberg,
• Wilian C. Rosa,
• Clarissa P. Frizzo,
• Nilo Zanatta,
• Marcos A. P. Martins,
• Isadora Tisoco,
• Bernardo A. Iglesias and
• Helio G. Bonacorso

Beilstein J. Org. Chem. 2021, 17, 2799–2811, doi:10.3762/bjoc.17.191

• was studied in DMSO solution using a 1,3-diphenylisobenzofuran (DPBF) photooxidation assay and the adequate equation as described by Pivetta and co-workers [33]. In this study, the methylene blue dye (MB) was used as a reference. The photooxidation rate constants (k) and 1O2 yield of derivatives (ΦΔ

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

• change the performance of photoreactions. Takei et al. reported a reaction rate that is 70 times higher in a photomicroreactor compared to a batch cuvette, with the same yield for the synthesis of ʟ-pipecolinic acid [16]. The rate of methylene blue reduction increased more than 150 times in a

• conditions and the kinetics of the selected reaction can lead to drastic changes in the PSTY. de Sá et al. combined external and internal numbering up in meso- and microchemical reactors of various sizes (Figure 3e). Photocatalytic degradations of methylene blue, rhodamine B, and phenol with TiO2 were

• and a monolith are shown in Figure 5a and Figure 5b, respectively. The performance of a capillary photomicroreactor packed with TiO2-coated glass beads were compared to a photomicroreactor having the walls coated with TiO2. The degradation of methylene blue was chosen as a model reaction. Complete

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

• used for the photocatalytic generation of H2O2, the degradation of methylene blue dye, and the reduction of nitrobenzene to aniline. Although it was an interesting and novel approach to efficiently irradiating HPCats, the report did not address the potential concerns with the heat dissipation from the

Activated carbon as catalyst support: precursors, preparation, modification and characterization

• Melanie Iwanow,
• Tobias Gärtner,
• Volker Sieber and
• Burkhard König

Beilstein J. Org. Chem. 2020, 16, 1188–1202, doi:10.3762/bjoc.16.104

• be produced by salt templating or ultrasonic spray pyrolysis as well as by microwave irradiation. The resulting activated carbon materials are characterized by a variety of techniques such as SEM, FTIR, nitrogen adsorption, Boehm titrations, adsorption of phenol, methylene blue and iodine, TPD, CHNS

• groups and simultaneously increase of basic properties [10]. Phenol, methylene blue and iodine adsorption: Adsorption capacity and amount of pores of activated carbon materials are determined by using different adsorbates (phenol, methylene blue and iodine). The activated carbons are added to defined

• methylene blue or phenol solutions and are shaken for a certain time. The concentration of the adsorbates methylene blue and phenol is spectrophotometrically determined at defined absorbance wavelengths. The iodine number is determined by titration with sodium thiosulfate. Generally, the iodine number

Fabrication, characterization and adsorption properties of cucurbit[7]uril-functionalized polycaprolactone electrospun nanofibrous membranes

• Changzhong Chen,
• Fengbo Liu,
• Xiongzhi Zhang,
• Zhiyong Zhao and
• Simin Liu

Beilstein J. Org. Chem. 2019, 15, 992–999, doi:10.3762/bjoc.15.97

• present in the PCL fiber matrix in an uncomplexed state. The static adsorption behavior of the PCL/CB[7] nanofibers towards methylene blue (MB) was also preliminary investigated. The results indicate that the adsorption of MB onto the nanofibrous membranes fits the second-order kinetic model and Langmuir

• isotherm model. Keywords: adsorption; cucurbit[7]uril; electrospinning; macrocycles; methylene blue; nanofiber; Introduction Electrospinning is recognized as the most simple and versatile method to fabricate multifunctional nanofibers from the solution or melt of polymers, polymer/nanoparticle mixtures

• the adsorption of methylene blue (MB) by the electrospun nanofibrous membranes. Adsorption isotherms (a) and the corresponding Langmuir plot (b) and Freundlich plot (c) for MB adsorption onto the electrospun nanofibrous membranes. Schematic illustration of the fabricating process of PCL/CB[7

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

• )/(Z) = 1:1]; c) Martin sulfurane, DCM, 0 °C, 10 min, 95%; d) NiCl2, NaBH4, −60 °C to −40 °C, 1 h, 96% (dr = 1:0.03); e) Li, EtOH, NH3, −70 °C, 10 min, 61% (dr = 1:0.4); f) i. O2, methylene blue, light, DCM, −30 °C, 30 h; ii. then O2, cat. TFA, DCM, rt, 2 d, 24%; g) i. O2, methylene blue, light, DCM

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

• allow access to unique chemistries such as photocatalysis at different wavelength or photoconductivity for example [76]. Moreover, they can be characterized by lower costs. For examples, methylene blue or eosin-Y are examples of widespread photoredox catalytic dyes [18]. There is a wide range of

Applications of organocatalysed visible-light photoredox reactions for medicinal chemistry

• Michael K. Bogdos,
• Emmanuel Pinard and
• John A. Murphy

Beilstein J. Org. Chem. 2018, 14, 2035–2064, doi:10.3762/bjoc.14.179

• it a uniquely suited method for LSF. For example, Scaiano et al. have demonstrated the direct C–H trifluoromethylation of heterocycles using TMEDA, visible light from white LEDs, Methylene Blue as the photocatalyst and Togni’s reagent as the trifluoromethyl source (Scheme 26) [71]. The reaction is

Stabilization of nanosized titanium dioxide by cyclodextrin polymers and its photocatalytic effect on the degradation of wastewater pollutants

• Tamás Zoltán Agócs,
• István Puskás,
• Erzsébet Varga,
• Mónika Molnár and
• Éva Fenyvesi

Beilstein J. Org. Chem. 2016, 12, 2873–2882, doi:10.3762/bjoc.12.286

• carboxymethyl β-cyclodextrin polymer (CMBCD-P) for stabilization of nanoTiO2 dispersions. The photocatalytic degradation of methylene blue and ibuprofen as model organic pollutants in various media (distilled water, NaCl solution and tap water) has been studied using nanoTiO2 as catalyst stabilized by CMBCD-P

• . CMBCD-P itself showed a catalytic effect on the UV degradation of methylene blue. In addition to enhancing the colloid stability of nanoTiO2 CMBCD-P showed also synergistic effects in catalyzing the photodecomposition process of the dye. On the other hand, ibuprofen as a model pharmaceutical, a

• ; methylene blue; nanoTiO2; synergetic effect; wastewater treatment; Introduction The wastewater purification and reuse are key challenges of our society. Globally 330 km3year−1 municipal wastewater is produced [1]. According to the European Investment Bank, by 2025, 800 million people will be living in

A flow reactor setup for photochemistry of biphasic gas/liquid reactions

• Josef Schachtner,
• Patrick Bayer and
• Axel Jacobi von Wangelin

Beilstein J. Org. Chem. 2016, 12, 1798–1811, doi:10.3762/bjoc.12.170

• processes (e.g., N-alkyl maleimides, ε = ~700 M−1 cm−1) [62] lead to more efficient light penetration in batch reactions and therefore only show a limited benefit of using flow reactors for such purposes. On the other hand, a 1 mM solution of methylene blue exhibits total absorption (>99.9%) at 0.35 mm

• . Following an optimized Schenck ene reaction procedure, N-methyl-1,2,3,6-tetrahydrophthalimide (1a) was reacted with molecular oxygen in the presence of methylene blue as sensitizer (Scheme 6). The resultant hydroperoxide motif (2a) constitutes a valuable carbocyclic building block. For reasons of

• residence time resulted from variations of the concentration of the sensitizer methylene blue (Figure 8). At >0.5 mmol L−1, a plateau was reached (at very high dye concentrations, >2.0 mmol L−1, 1O2 quenching leads to lower conversions) [43][77]. Variations of the used light source regarding power and

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

Stereoselective synthesis of hernandulcin, peroxylippidulcine A, lippidulcines A, B and C and taste evaluation

• Marco G. Rigamonti and
• Francesco G. Gatti

Beilstein J. Org. Chem. 2015, 11, 2117–2124, doi:10.3762/bjoc.11.228

• [32] of (+)-hernandulcin in a mixed solvent system (CH2Cl2/MeOH, 4:1) and in presence of a catalytic amount of the methylene blue photosensitizer (<0.1% in weight, λ = 280 nm) afforded a mixture of peroxylippidulcines A, B and C, i.e., 2a–c, in the ratio of 47:21:32 (by 1H NMR) and in an almost

• ) TBAF, MeCN, rt, 2 h. Reagents and conditions: (a) cat. methylene blue, light, bubbling O2, CH2Cl2/MeOH 4:1, rt, 15 h; (b) imidazole, TBDPSCl, cat. DMAP, DMF, rt, 24 h; (c) TBAF, THF, rt, 12 h; (d) TMSCl, cat. DMAP, CH2Cl2/pyridine 2:1, 0 °C/rt, 24 h; (e) acidic-aqueous work-up then PPh3, CH2Cl2, rt, 15

Eosin Y-catalyzed visible-light-mediated aerobic oxidative cyclization of N,N-dimethylanilines with maleimides

• Zhongwei Liang,
• Song Xu,
• Wenyan Tian and
• Ronghua Zhang

Beilstein J. Org. Chem. 2015, 11, 425–430, doi:10.3762/bjoc.11.48

• and not sustainable. Similar to the redox properties of these organometallic complexes, some metal-free organic dyes such as Eosin Y, Rose Bengal, Fluorescein, and Methylene Blue, have shown superiority of their applications as photocatalysts, which are easy to handle, environmentally friendly

• 1), Rose Bengal gave a slightly lower yield (Table 1, entry 2), whereas Methylene Blue and Fluorescein gave poor yields (Table 1, entries 3 and 4). Under an O2 atmosphere, the yield of tetrahydroquinoline product 3a was decreased to 77% (Table 1, entry 5). When the molar proportion of 1a and 2a was

Electrochemical oxidation of cholesterol

• Jacek W. Morzycki and
• Andrzej Sobkowiak

Beilstein J. Org. Chem. 2015, 11, 392–402, doi:10.3762/bjoc.11.45

• of sensing, which have a distinct advantage over conventional enzymatic processes, have recently been developed. Some of these methods are based on the indirect electrochemical oxidation of cholesterol by using bromine species in organic media [69][70]. In a recent method, methylene blue formed an

• inclusion complex with β-cyclodextrin functionalized graphene and emerged as a cholesterol sensing matrix. Methylene blue was then replaced by the cholesterol molecule and moved out in the buffer solution, where it was detected electrochemically by using the differential pulse voltammetric technique [71

Flow synthesis of a versatile fructosamine mimic and quenching studies of a fructose transport probe

• Matthew B. Plutschack,
• D. Tyler McQuade,
• Giulio Valenti and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2013, 9, 2022–2027, doi:10.3762/bjoc.9.238

• is known to self-quench at high concentrations [21][22]. Trypan blue is routinely used to quench autofluorescence in confocal fluorescence microscopy and fluorescence activated cell sorting (FACS) [23][24], and dyes like Bromophenol Blue, Brilliant Blue R, and Methylene Blue have been applied to

• ). The data set was plotted in OriginPro 8.6 and fitted using a self-quenching model, with direct weighting. Comparison of quenching 2 µM NBDM, as measured by fluorescence intensity of Trypan Blue, Bromophenol Blue, Brilliant Blue R, and Methylene Blue. Each data set was plotted in OriginPro 8.6 and

Polymeric redox-responsive delivery systems bearing ammonium salts cross-linked via disulfides

• Christian Dollendorf,
• Martin Hetzer and
• Helmut Ritter

Beilstein J. Org. Chem. 2013, 9, 1652–1662, doi:10.3762/bjoc.9.189

• networks can be used for molecular inclusion and controlled release. As an example, phenolphthalein, methylene blue and reactive orange 16 were included into the network. After treatment with DTT a release of the dye could be recognized. Physical properties of the cross-linked materials, e.g., glass

• different polymeric chains in close proximity can form cross-linked disulfide bonds and, therefore, polymeric networks. As an example for the enclosure of drugs or other molecules, the dyes phenolphthalein, methylene blue and reactive orange 16, respectively, were embedded into the polycationic networks

• cannot only reduce disulfide bonds to thiols but it can also reduce the functional groups of dyes or substances. For example, methylene blue showed an initial loss of color during the release investigations due to the reduction by DTT, but regained it after exposure to oxygen as the leuco form of

Flow photochemistry: Old light through new windows

• Jonathan P. Knowles,
• Luke D. Elliott and
• Kevin I. Booker-Milburn

Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229

• issues such as oxygen depletion in the reaction mixture during the reaction, and bubble formation. Such reactors have been shown to be effective in the oxidative degradations of para-chlorophenol, toluene [36], phenol and methylene blue [37] with a deposited TiO2 photocatalyst. Aside from oxidative

• . However, not all dual channel microreactors need suffer such low productivity; the oxidation of β-citronellol (24) has been performed in the dual channel reactor designed by Kim et al. and gave a daily output of 45.5 mmol (1.9 mmol/h) by using methylene blue as the sensitiser and a 16 W LED light source

• microreactor surface, thus eliminating the need for subsequent removal of the catalyst in dispersed powder form as would be required in a batch reactor. This methodology has been shown to be effective in the oxidative degradation of a range of organic compounds, including methylene blue, [41][42][43] o-cresol

An easily accessible sulfated saccharide mimetic inhibits in vitro human tumor cell adhesion and angiogenesis of vascular endothelial cells

• Grazia Marano,
• Claas Gronewold,
• Martin Frank,
• Anette Merling,
• Christian Kliem,
• Sandra Sauer,
• Manfred Wiessler,
• Eva Frei and
• Reinhard Schwartz-Albiez

Beilstein J. Org. Chem. 2012, 8, 787–803, doi:10.3762/bjoc.8.89

Triple-channel microreactor for biphasic gas–liquid reactions: Photosensitized oxygenations

• Ram Awatar Maurya,
• Chan Pil Park and
• Dong-Pyo Kim

Beilstein J. Org. Chem. 2011, 7, 1158–1163, doi:10.3762/bjoc.7.134

• -terpinene. Photosensitized oxygenation of (−)-citronellol The photosensitized oxygenation of citronellol is an industrially important synthetic transformation [47] as it is used for bulk production of a fragrance, rose oxide (Scheme 1). The reaction was performed with methylene blue as a sensitizer in

• expected with the new triple-channel microreactor. The microreactor was irradiated with a 16 W white LED light source (FAWOO-Tech. Korea, LH16-AFE39S-White) kept in close contact. The reaction mixture (a solution of citronellol and methylene blue in acetonitrile) was pumped into the middle channel without

• efficiency of the triple-channel microreactor. The product of this reaction is an allyl hydroperoxide alcohol that is used in the synthesis of artemisinin-derived antimalarial 1,2,4-trioxanes [48]. The reaction in the triple-channel and in batch was carried out as aforementioned with methylene blue as

Molecular recognition of organic ammonium ions in solution using synthetic receptors

• Andreas Späth and
• Burkhard König

Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32