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COVALENT ORGANIC FRAMEWORKS AND APPLICATIONS AS PHOTOCATALYSTS
Described herein are covalent organic frameworks. The covalent organic frameworks have unique structural and physical properties, which lends them to be versatile in a number of different applications and uses. In one aspect, the covalent organic frameworks are composed of a plurality of fused aromatic groups and electron-deficient chromophores. The covalent organic frameworks are useful as photocatalysts in a number of different applications.
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(2021/05/21)

Singlet Oxygen Generation from a Water-Soluble Hypervalent Iodine(V) Reagent AIBX and H2O2: An Access to Artemisinin
Herein, we report an efficient method for the chemical generation of 1O2 by treatment of H2O2 with AIBX, a highly water-soluble, bench-stable, recyclable hypervalent iodine(V) reagent developed by our group. The generation of 1O2 was confirmed by the following results: (1) capture of 1O2 with the sodium salt of anthracene-9,10-bis(ethanesulfonate) produced the corresponding endoperoxide and (2) TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) produced by the oxidation of 2,2,6,6-tetramethylpiperidine with 1O2 generated using the AIBX/H2O2 system was detected by electron spin resonance spectroscopy. To illustrate the potential utility of this method for organic synthesis, we used the AIBX/H2O2 system to perform typical reactions of 1O2: [2 + 2]/[4 + 2] cycloadditions, Schenck ene reactions, and heteroatom oxidation reactions, which afforded the corresponding products in high yields. Moreover, we used the method to synthesize the antimalarial drug artemisinin. Finally, we demonstrated that AIBX could be regenerated after the reaction by means of a workup involving extraction and removal of water to obtain a precursor of AIBX, which could then be re-oxidized.
Hu, Ze-Nan,Shen, Hui-Jie,Zhang, Chi
(2021/06/21)

Nature inspired singlet oxygen generation to access α-amino carbonyl compounds: Via 1,2-acyl migration
We have discovered chlorophyll catalyzed 1,2-acyl migration reactions to achieve α-amino carbonyl compounds directly from the enaminones. In general, singlet oxygen is generated during photosynthesis in the photosystem II center. This singlet oxygen can readily react with the unsaturated double bonds present in biomolecules. This reactivity intrigued us to apply this concept towards unsaturated enaminones and others to achieve highly valuable compounds. Indeed, this photosensitizer is very cheap, commercially available, main group metal based and provided excellent efficiency for singlet oxygen mediated chemistry by achieving high turnover number (TON) > 300 with a high turnover frequency (TOF) of 50 h-1. Finally, a combination of DFT calculations and detailed mechanistic experiments provided the exact role of the photosensitizer and clear insights into the reaction.
Schilling, Waldemar,Zhang, Yu,Sahoo, Prakash Kumar,Sarkar, Samir Kumar,Gandhi, Sivaraman,Roesky, Herbert W.,Das, Shoubhik
supporting information
p. 379 - 387
(2021/01/28)

8,8′-(Benzo[c][1,2,5]thiadiazole-4,7-diyl)bis(quinolin-4(1H)-one): a twisted photosensitizer with AIE properties
A new benzothiadiazole (BTZ) luminogen is preparedviathe Suzuki-Miyaura Pd-catalysed C-C cross-coupling of 8-iodoquinolin-4(1H)-one and a BTZ bispinacol boronic ester. The rapid reaction (5 min) affords the air-, thermo-, and photostable product in 97% yield as a yellow precipitate that can be isolated by filtration. The luminogen exhibits aggregated-induced emission (AIE) properties, which are attributed to its photoactive BTZ core and nonplanar geometry. It also behaves as a molecular heterogeneous photosensitizer for the production of singlet oxygen under continuous flow conditions.
Broumidis, Emmanouil,Jones, Callum M. S.,Kourtellaris, Andreas,Koutentis, Panayiotis A.,Koyioni, Maria,Lloyd, Gareth O.,Marques-Hueso, Jose,Vilela, Filipe
p. 29102 - 29107
(2021/10/08)

Singlet-Oxygen Generation by Peroxidases and Peroxygenases for Chemoenzymatic Synthesis
Singlet oxygen is a reactive oxygen species undesired in living cells but a rare and valuable reagent in chemical synthesis. We present a fluorescence spectroscopic analysis of the singlet-oxygen formation activity of commercial peroxidases and novel peroxygenases. Singlet-oxygen sensor green (SOSG) is used as fluorogenic singlet oxygen trap. Establishing a kinetic model for the reaction cascade to the fluorescent SOSG endoperoxide permits a kinetic analysis of enzymatic singlet-oxygen formation. All peroxidases and peroxygenases show singlet-oxygen formation. No singlet oxygen activity could be found for any catalase under investigation. Substrate inhibition is observed for all reactive enzymes. The commercial dye-decolorizing peroxidase industrially used for dairy bleaching shows the highest singlet-oxygen activity and the lowest inhibition. This enzyme was immobilized on a textile carrier and successfully applied for a chemical synthesis. Here, ascaridole was synthesized via enzymatically produced singlet oxygen.
Ingenbosch, Kim N.,Quint, Stephan,Dyllick-Brenzinger, Melanie,Wunschik, Dennis S.,Kiebist, Jan,Süss, Philipp,Liebelt, Ute,Zuhse, Ralf,Menyes, Ulf,Scheibner, Katrin,Mayer, Christian,Opwis, Klaus,Gutmann, Jochen S.,Hoffmann-Jacobsen, Kerstin
p. 398 - 407
(2020/10/09)

A method to determine the correct photocatalyst concentration for photooxidation reactions conducted in continuous flow reactors
When conducting a photooxidation reaction, the key question is what is the best amount of photocatalyst to be used in the reaction? This work demonstrates a fast and simple method to calculate a reliable concentration of the photocatalyst that will ensure an efficient reaction. The determination is based on shifting the calculation away from the concentration of the compound to be oxidized to utilizing the limitations on the total light dose that can be delivered to the catalyst. These limitations are defined by the photoflow setup, specifically the channel height and the emission peak of the light source. This method was tested and shown to work well for three catalysts with different absorption properties through using LEDs with emission maxima close to the absorption maximum of each catalyst.
Gremetz, Sylvain,Horn, Clemens R.
supporting information
p. 871 - 879
(2020/05/14)

Synthesis and application of photosensitizer
The invention relates to the field of organic synthesis and biological medicine, particularly to synthesis of a class of photosensitizers with aggregation-induced emission properties, and applicationof the photosensitizers loaded on a solid-phase material in synthesis of bioactive molecules or medical intermediates and application of the photosensitizers in the medical fields of photodynamic therapy, immunogenic cell death and the like. According to the invention, the photosensitizer can effectively generate singlet oxygen under an illumination condition; compared with the traditional photosensitizer, the photosensitizer of the invention has the following characteristics that the phenomena of aggregation fluorescence quenching and aggregation singlet oxygen generation capacity reduction are avoided; and when the photosensitizer is applied to synthesis of bioactive molecules or medical intermediates, the photosensitizer has the advantages of reusability, simple and convenient post-treatment and the like, and the characteristics are not possessed by traditional photosensitizers.
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(2020/09/23)

Efficient generation of singlet oxygen by perylene diimide photosensitizers covalently bound to conjugate polymers
New conjugated polymers with perylene diimides (PDI) as pendant groups were synthesized and deposited on glass substrates by the spin coating. The resulting thin films were characterized by UV–vis, Raman spectroscopy, atomic force microscopy and profilometry. It was shown that PDI photosensitizers retain its photoactivity after covalent immobilization and the formed layers can be applied as efficient and environmentally stable source of singlet oxygen, 1O2, as tested with 1,3-diphenylisobenzofuran (DPBF) specific trap. Additionally, α-terpinene heterogeneous photooxidation was studied as the practical use of singlet oxygen generated by this novel PDI-based materials. The use of such heterogeneous source of singlet oxygen can be beneficial for the fine chemicals synthesis, due to simplified products isolation and purification step.
Blacha-Grzechnik, Agata,Drewniak, Anna,Walczak, Krzysztof Z.,Szindler, Marek,Ledwon, Przemyslaw
(2019/11/03)

Discrete Ti?O?Ti Complexes: Visible-Light-Activated, Homogeneous Alternative to TiO2 Photosensitisers
A series of novel bimetallic TiIV amine bis(phenolate) complexes was synthesised and fully characterised. X-ray crystallography studies revealed distorted octahedral geometries around the Ti centres with single or double oxo-bridges connecting the two metals. These robust, air- and moisture-stable complexes were employed as photosensitisers generating singlet oxygen following irradiation with visible light (420 nm) LED module in a commercial flow reactor. All five complexes showed high activity in the photo-oxygenation of α-terpinene and achieved complete conversion to ascaridole in four hours at ambient temperature. The excellent selectivity of these photosensitisers towards ascaridole (vs. transformation to p-cymene) was demonstrated with control experiments using a traditional TiO2 catalyst. Further comparative studies employing the free pro-ligands as well as a monometallic analogue highlighted the importance of the ‘TiO2-like’ moiety in the polymetallic catalysts. Computational studies were used to determine the nature of the ligand to metal charge transfer (LMCT) states and singlet–triplet gaps for each complex, the calculated trends in the UV-vis absorption spectra across the series agreed well with the experimental results.
Behm, Kira,Fazekas, Eszter,Paterson, Martin J.,Vilela, Filipe,McIntosh, Ruaraidh D.
p. 9486 - 9494
(2020/07/13)

Robust Organic Photosensitizers Immobilized on a Vinylimidazolium Functionalized Support for Singlet Oxygen Generation under Continuous-Flow Conditions
Rose Bengal was immobilized on a vinylimidazolium functionalized support, and the heterogeneous organic photosensitizer thus prepared was applied for photooxidation reactions of organic molecules under continuous-flow conditions. Substituents of the cation part of the support were found to play a crucial role in determining the lifetime of the catalyst. More than 11 days continuous operation of a flow reaction was achieved.
Kobayashi, Shū,Koumura, Nagatoshi,Masuda, Koichiro,Onozawa, Shun-Ya,Sato, Kazuhiko,Shimada, Shigeru,Wang, Yao
supporting information
p. 497 - 501
(2020/03/13)

An entirely solvent-free photooxygenation of olefins under continuous flow conditions
Photooxygenations of alkenes with singlet oxygen are a versatile, atom-economical transformation. The choice of solvents is key to the success of this oxyfunctionalization with direct impact on the solubility of substrates, the lifetime of the reactive oxygen species, and the up-scaling of the process. We report an entirely solvent-free continuous-flow photooxygenation that operates at very high substrate/sensitizer ratios and enables high space-time yields.
Bayer, Patrick,Jacobi Von Wangelin, Axel
p. 2359 - 2364
(2020/05/28)

Photocatalytic Molecular Oxygen Activation by Regulating Excitonic Effects in Covalent Organic Frameworks
Excitonic effects caused by Coulomb interactions between electrons and holes play subtle and significant roles on photocatalysis, yet have been long ignored. Herein, porphyrinic covalent organic frameworks (COFs, specifically DhaTph-M), in the absence or presence of different metals in porphyrin centers, have been shown as ideal models to regulate excitonic effects. Remarkably, the incorporation of Zn2+ in the COF facilitates the conversion of singlet to triplet excitons, whereas the Ni2+ introduction promotes the dissociation of excitons to hot carriers under photoexcitation. Accordingly, the discriminative excitonic behavior of DhaTph-Zn and DhaTph-Ni enables the activation of O2 to 1O2 and O2?-, respectively, under visible light irradiation, resulting in distinctly different activity and selectivity in photocatalytic terpinene oxidation. Benefiting from these results, DhaTph-Ni exhibits excellent photocatalytic activity in O2?-engaged hydroxylation of boronic acid, while DhaTph-Zn possesses superior performance in 1O2-mediated selective oxidation of organic sulfides. This work provides in-depth insights into molecular oxygen activation and opens an avenue to the regulation of excitonic effects based on COFs.
Qian, Yunyang,Li, Dandan,Han, Yulan,Jiang, Hai-Long
p. 20763 - 20771
(2020/12/23)

Energy-Efficient Solar Photochemistry with Luminescent Solar Concentrator Based Photomicroreactors
The sun is the most sustainable light source available on our planet, therefore the direct use of sunlight for photochemistry is extremely appealing. Demonstrated here, for the first time, is that a diverse set of photon-driven transformations can be efficiently powered by solar irradiation with the use of solvent-resistant and cheap luminescent solar concentrator based photomicroreactors. Blue, green, and red reactors can accommodate both homogeneous and multiphase reaction conditions, including photochemical oxidations, photocatalytic trifluoromethylation chemistry, and metallaphotoredox transformations, thus spanning applications over the entire visible-light spectrum. To further illustrate the efficacy of these novel solar reactors, medicinally relevant molecules, such as ascaridole and an intermediate of artemisinin, were prepared as well.
Cambié, Dario,Dobbelaar, Jeroen,Riente, Paola,Vanderspikken, Jochen,Shen, Chong,Seeberger, Peter H.,Gilmore, Kerry,Debije, Michael G.,No?l, Timothy
supporting information
p. 14374 - 14378
(2019/08/30)

“Dark” Singlet Oxygen Made Easy
An operationally simple continuous flow generator of “dark” singlet oxygen has been developed. The singlet oxygen was efficiently reacted with several chemical traps to give the corresponding oxygenated products in high yields. The developed “dark” singlet oxygen generator has been successfully applied in the synthesis of the antimalarial drug artemisinin.
Elsherbini, Mohamed,Allemann, Rudolf K.,Wirth, Thomas
supporting information
p. 12486 - 12490
(2019/08/26)

Photon upconversion for the enhancement of microfluidic photochemical synthesis
Photochemical transformations are greatly improved in yield by fluidic reactor technology. However, the delivery of synthetically-active light to the reactants is a challenge. Here, we use upconversion in a bio-inspired microreactor to augment the flux of critical wavelengths of light. This new technology increased of a model reaction by converting a greater portion of sunlight to photochemically-available photons.
Wu,Moser,Steeves,Figueroa,Wallace,Kim,Esser-Kahn,Steinhardt
p. 26172 - 26175
(2019/09/09)

Efficient photocatalytic oxidation sensitized by conjugated polymers in a batch reaction and microreactors under visible light
We studied microfluidic reaction systems for the efficient catalytic oxidation of α-terpinene sensitized by conjugated polymers. Different microreactors, including flow-reaction-based mono- and dual-channel, as well as polymer-coated dual-channel microreactors, were designed and evaluated, which demonstrated improved reaction efficiency.
Li, Anqi,Tan, Chunyan,Yuan, Tianying,Liang, Jiamei,Gao, Dan,Tan, Ying,Jiang, Yuyang
p. 15927 - 15932
(2018/08/28)

Selective endoperoxide formation by heterogeneous TiO2 photocatalysis with dioxygen
We report the selective formation of endoperoxides by aerobic TiO2 photocatalysis through the cyclic addition of dioxygen and a non-conjugated diene, the first heterogeneous catalytic system for endoperoxide synthesis. This green protocol does not require any additive and the photocatalyst is abundant and recyclable, providing a yield up to 64% and >20:1 diastereoselectivity. Mechanistic investigations were carried out by using product analysis, kinetic studies, O-18 labelling experiments, electron-spin resonance and a set of quenching experiments. Superoxide (but not singlet oxygen, triplet oxygen or peroxide) is directly involved in the reaction cascade to form the endoperoxide product. The new findings may be helpful for future for designing eco-friendly and energy sustainable strategies for selective oxygenation reactions using semiconductors, O2 and sunlight.
Qiao, Xiaofeng,Biswas, Subharanjan,Wu, Wenli,Zhu, Feng,Tung, Chen-Ho,Wang, Yifeng
supporting information
p. 2421 - 2427
(2018/04/11)

Photocatalytic Properties and Mechanistic Insights into Visible Light-Promoted Aerobic Oxidation of Sulfides to Sulfoxides via Tin Porphyrin-Based Porous Aromatic Frameworks
Using concepts of biomimetic catalysis, a kind of tin porphyrin-based porous aromatic framework (SnPor@ PAF) with broad and strong optical absorption in the visible light region was successfully synthesized and subsequently used in the aerobic oxidation of sulfides to sulfoxides under ambient conditions and visible light irradiation, in which exhibited enzyme-like features of high efficiency and high selectivity. More interestingly, heterogeneous SnPor@PAF was naturally regarded as an intriguing and versatile photosensitizer for photocatalytic transformation and could be reused several times because of its robust and rigid porphyrin framework. As expected, their π-conjugated structure characteristic in the molecular skeleton might facilitate the activation of molecular oxygen under mild reaction conditions and promoted the production of reactive oxygen species (singlet oxygen (1O2) and superoxide radical anion (O2.?)), which would involve energy transfer and/or electron transfer process. Experimental investigations including emission quenching experiment, oxygen-isotope labelling, typical inhibition experiments, classical fluorescence probe study, photo-oxidation of α-terpinene and in situ electron spin resonance, could provide a mechanistic insight into the photocatalytic reactions. (Figure presented.).
Jiang, Jun,Luo, Rongchang,Zhou, Xiantai,Chen, Yaju,Ji, Hongbing
supporting information
p. 4402 - 4411
(2018/10/15)

Fluoropolymer-Coated PDMS Microfluidic Devices for Application in Organic Synthesis
In recent years there has been huge interest in the development of microfluidic reactors for the synthesis of small molecules and nanomaterials. Such reaction platforms represent a powerful and versatile alternative to traditional formats since they allow for the precise, controlled, and flexible management of reactive processes. To date, the majority of microfluidic reactors used in small-molecule synthesis have been manufactured using conventional lithographic techniques from materials such as glasses, ceramics, stainless steel, and silicon. Surprisingly, the fabrication of microfluidic devices from such rigid materials remains ill-defined, complex, and expensive. Accordingly, the microfluidic toolkit for chemical synthesis would significantly benefit from the development of solvent-resistant microfluidic devices that can be manufactured using soft-lithographic prototyping methods. Whilst significant advances in the development of solvent-resistant polymers have been made, only modest steps have been taken towards simplifying their use as microfluidic reactors. Herein, we emphasize the benefits of using a commercially available, amorphous perfluorinated polymer, CYTOP, as a coating with which to transform PDMS into a chemically inert material for use in organic synthesis applications. Its efficacy is demonstrated through the subsequent performance of photooxidation reactions and reactions under extremely acidic or basic conditions.
Yang, Tianjin,Choo, Jaebum,Stavrakis, Stavros,de Mello, Andrew
p. 12078 - 12083
(2018/08/21)

Singlet oxygen-engaged selective photo-oxidation over pt nanocrystals/porphyrinic MOF: The roles of photothermal effect and pt electronic state
The selectivity control toward aldehyde in the aromatic alcohol oxidation remains a grand challenge using molecular oxygen under mild conditions. In this work, we designed and synthesized Pt/PCN-224(M) composites by integration of Pt nanocrystals and porphyrinic metal-organic frameworks (MOFs), PCN-224(M). The composites exhibit excellent catalytic performance in the photo-oxidation of aromatic alcohols by 1 atm O2 at ambient temperature, based on a synergetic photothermal effect and singlet oxygen production. Additionally, in opposition to the function of the Schottky junction, injection of hot electrons from plasmonic Pt into PCN-224(M) would lower the electron density of the Pt surface, which thus is tailorable for the optimized catalytic performance via the competition between the Schottky junction and the plasmonic effect by altering the light intensity. To the best of our knowledge, this is not only an unprecedented report on singlet oxygen-engaged selective oxidation of aromatic alcohols to aldehydes but also the first report on photothermal effect of MOFs.
Chen, Yu-Zhen,Wang, Zhiyong U.,Wang, Hengwei,Lu, Junling,Yu, Shu-Hong,Jiang, Hai-Long
supporting information
p. 2035 - 2044
(2017/02/15)

Scalable Photocatalytic Oxidation of Methionine under Continuous-Flow Conditions
Highly efficient and chemoselective singlet oxygen oxidation of unprotected methionine was performed in water using a continuous mesofluidic reactor. Sustainable process engineering and conditions were combined to maximize process efficiency and atom economy, with virtually no waste generation and safe operating conditions. Three water-soluble metal-free photosensitizers [Rose Bengal, Methylene Blue, and tetrakis(4-carboxyphenyl)porphyrin] were assessed. The best results were obtained with Rose Bengal (0.1 mol %) at room temperature under white light irradiation and a slight excess of oxygen. Process and reaction parameters were monitored in real-time with in-line NMR. Other classical organic substrates (α-terpinene and citronellol) were oxidized under similar conditions with excellent performances.
Emmanuel, Noémie,Mendoza, Carlos,Winter, Marc,Horn, Clemens R.,Vizza, Alessandra,Dreesen, Laurent,Heinrichs, Beno?t,Monbaliu, Jean-Christophe M.
supporting information
p. 1435 - 1438
(2017/09/22)

Continuous Photo-Oxidation in a Vortex Reactor: Efficient Operations Using Air Drawn from the Laboratory
We report the construction and use of a vortex reactor which uses a rapidly rotating cylinder to generate Taylor vortices for continuous flow thermal and photochemical reactions. The reactor is designed to operate under conditions required for vortex generation. The flow pattern of the vortices has been represented using computational fluid dynamics, and the presence of the vortices can be easily visualized by observing streams of bubbles within the reactor. This approach presents certain advantages for reactions with added gases. For reactions with oxygen, the reactor offers an alternative to traditional setups as it efficiently draws in air from the lab without the need specifically to pressurize with oxygen. The rapid mixing generated by the vortices enables rapid mass transfer between the gas and the liquid phases allowing for a high efficiency dissolution of gases. The reactor has been applied to several photochemical reactions involving singlet oxygen (1O2) including the photo-oxidations of α-terpinene and furfuryl alcohol and the photodeborylation of phenyl boronic acid. The rotation speed of the cylinder proved to be key for reaction efficiency, and in the operation we found that the uptake of air was highest at 4000 rpm. The reactor has also been successfully applied to the synthesis of artemisinin, a potent antimalarial compound; and this three-step synthesis involving a Schenk-ene reaction with 1O2, Hock cleavage with H+, and an oxidative cyclization cascade with triplet oxygen (3O2), from dihydroartemisinic acid was carried out as a single process in the vortex reactor.
Lee, Darren S.,Amara, Zacharias,Clark, Charlotte A.,Xu, Zeyuan,Kakimpa, Bruce,Morvan, Herve P.,Pickering, Stephen J.,Poliakoff, Martyn,George, Michael W.
supporting information
p. 1042 - 1050
(2017/07/26)

Polymer-Supported Photosensitizers for Oxidative Organic Transformations in Flow and under Visible Light Irradiation
A 2,1,3-benzothiadiazole (BTZ)-based vinyl cross-linker was synthesized and copolymerized with large excesses of styrene using free radical polymerization to deliver heterogeneous triplet photosensitizers in three distinct physical formats: gels, beads, and monoliths. These photosensitizers were employed for the production of singlet oxygen (1O2) and for the aerobic hydroxylation of arylboronic acids via superoxide radical anion (O2?-), whereby the materials demonstrated good chemical and light stability. BTZ-containing beads and monoliths were exploited as photosensitizers in a commercial flow reactor, and 1O2 production was also demonstrated using direct sunlight irradiation, with a conversion rate comparable to the rates achieved when a 420 nm LED module is used as the source of photons.
Tobin, John M.,McCabe, Timothy J. D.,Prentice, Andrew W.,Holzer, Sarah,Lloyd, Gareth O.,Paterson, Martin J.,Arrighi, Valeria,Cormack, Peter A. G.,Vilela, Filipe
p. 4602 - 4612
(2017/07/24)

Singlet oxygen generation from poly[4-diacetoxyiodo]styrene and hydrogen peroxide
Treatment of hydrogen peroxide with a polymer-supported hypervalent iodine compound, poly[4-diacetoxyiodo] styrene (PDAIS), generates singlet molecular oxygen (1O2). Singlet oxygen generation was proved by trapping with typical organic compounds such as conjugated dienes, aromatic dienes, and electron-rich alkene. When compared to monomer analogue, the use of PDAIS in peroxidation of substrates gave slightly better yields (45%–96%). Regeneration and reuse of PDAIS showed similar activity. The mechanism underlying generation of singlet oxygen and reaction scope was examined.
?atir, Mustafa
p. 467 - 475
(2017/09/15)

Visible light dye-photosensitised oxidation of pyrroles using a simple LED photoreactor
The photooxidation of pyrrole is typically low yielding due to the absorbance of ultraviolet light, which leads to uncontrolled polymerisation and decomposition. Presented herein is the development of a simple and cost-effective photoreactor utilising Light Emitting Diodes (LEDs) as the light source, and its application to the dye-sensitised oxidation of a range of pyrroles to give corresponding 3-pyrrolin-2-ones. The broader applicability of this approach to the generation of 1O2 is also explored.
Howard, James K.,Rihak, Kieran J.,Hyland, Christopher J. T.,Bissember, Alex C.,Smith, Jason A.
p. 8873 - 8880
(2016/10/03)

Getting the Most out of Solar Irradiation: Efficient Use of Polychromatic Light for Water Splitting
To increase the fraction of utilizable polychromatic light, a new reactor concept was developed and manufactured by using rapid prototyping technologies. Investigation of the prototypes revealed enhancements of the photocurrent by up to one order of magnitude, when TiO2was used as the photoanode in combination with commercially available photovoltaic cells. The reported concept is scalable and an easy transfer to technical scale is expected from a technological as well as an economical perspective. Experimental results underline the conclusion that to achieve efficient overall use of solar irradiation both the material as well as the reactor/process must be considered. Combining these complementary approaches allows largest possible optimization potential. With respect to ongoing research, the concept also breaks ground for the development of catalysts.
Ta?tan, ümit,Ziegenbalg, Dirk
p. 18824 - 18832
(2016/12/26)

The method for manufacturing the same and hexa- cheer penta- plug compd., and optical catalyst comprising the same
PROBLEM TO BE SOLVED: To provide a hexathiapentacene compound having excellent stability and high solubility and suitable for an organic semiconductor material and a photocatalyst. SOLUTION: The hexathiapentacene compound is represented by general formula (1) [in formula, R1, R2, R3and R4each denotes at least one selected from the group consisting of a 1-100C organic group which may independently have substituents and a halogen atom]. COPYRIGHT: (C)2012,JPOandINPIT
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(2016/10/20)

Synergy between bis(dimethyldioctylammonium) molybdate and tetraethylene glycol monooctyl ether: A winning combination for interfacial catalysis in thermo-controlled and switchable microemulsions
A simple thermo-responsive one-phase microemulsion (μem) is designed to enable the dark singlet oxidation of organic substrates while allowing a straightforward separation of the catalytic surfactant and products in two distinct phases by cooling down the reaction medium. This latter is prepared by combining a small amount (1%) of the catalytic surfactant bis(dimethyldioctylammonium) molybdate, [DiC8]2[MoO4], with the nonionic amphiphile tetraethylene glycol monooctyl ether, C8E4. Tensiometry and dynamic light scattering are used to rationalize the synergy between the two surfactants which strongly interact. The oxidation takes place in the effective one-phase Winsor IV system which separates into two phases (μem + oil, i.e. Winsor I) just by temperature change thanks to the presence of the thermosensitive C8E4. The thermal-controlled nanostructured reaction medium is applied to the ene reaction, [4+2] cycloaddition and sulfide oxidation.
Hong, Bing,Leclercq, Lo?c,Collinet-Fressancourt, Marion,Lai, Jonathan,Bauduin, Pierre,Aubry, Jean-Marie,Nardello-Rataj, Véronique
p. 142 - 149
(2015/02/19)

Continuous flow photooxygenation of monoterpenes
Photooxygenation of monoterpenes was conducted in two continuous flow reactors. The first, suitable for lab-scale research, had a maximum yield of 99.9%, and the second, focused on industrial applications, showed a daily output that was 270.0-fold higher than that in batch systems. The use of sunlight instead of an LED lamp gave 68.28% conversion.
Park, Chan Yi,Kim, Young Joon,Lim, Hyo Jin,Park, Jeong Hyeon,Kim, Mi Jin,Seo, Seung Woo,Park, Chan Pil
p. 4233 - 4237
(2015/02/19)

Bismuth-substituted "sandwich" type polyoxometalate catalyst for activation of peroxide: Umpolung of the peroxo intermediate and change of chemoselectivity
The epoxidation of alkenes with peroxides by WVI, MoVI, VV, and TiIV compounds is well established, and it is well accepted that the active intermediate peroxo species are electrophilic toward nucleophilic substrates. Polyoxotungstates, for example, those of the "sandwich" structure, [WZn(TM-L)2(ZnW9O34)2]q- in which TM = transition metal and L = H2O, have in the past been found to be excellent epoxidation catalysts. It has now been found that substituting the Lewis basic BiIII into the terminal position of the "sandwich" polyoxometalate structure to yield [Zn2BiIII2(ZnW9O34)2]14- leads to an apparent umpolung of the peroxo species and formation of a nucleophilic peroxo intermediate. There are two lines of evidence that support the formation of a reactive nucleophilic peroxo intermediate: (1) More electrophilic sulfoxides are more reactive than more nucleophilic sulfides, and (2) nonfunctionalized aliphatic alkenes and dienes showed ene type reactivity rather than epoxidation pointing toward "dark" formation of singlet oxygen from the nucleophilic intermediate peroxo species. Allylic alcohols reacted much faster than alkenes but showed chemoselectivity toward C-H bond activation of the alcohol and formation of aldehydes or ketones rather than epoxidation. This explained via alkoxide formation at the BiIII center followed by oxidative β-elimination.
Amanchi, Srinivasa Rao,Khenkin, Alexander M.,Diskin-Posner, Yael,Neumann, Ronny
p. 3336 - 3341
(2015/06/16)

IMPROVED PRODUCTION METHOD FOR OXYDATION PRODUCT BY OPTICAL OXYGEN OXIDATION
PROBLEM TO BE SOLVED: To provide an improved optical oxygen oxidation method for an organic compound in which reaction can be progressed by high speed and efficiency, and also, the use of a photosensitizer can be reduced or made needless. SOLUTION: Provided is an improved production method in the production of a product by the optical oxygen oxidation of a raw material organic compound, characterized in that a solution containing the raw material organic compound placed under light irradiation is injected with an oxygen-containing gas in the form of nanobubbles, and the state where the nanobubbles of the oxygen-containing gas are dispersed into the solution is retained, thus the optical oxygen oxidation reaction of the raw material organic compound is progressed to obtain the product. COPYRIGHT: (C)2015,JPOandINPIT
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(2017/01/02)

SEPARATION TECHNIQUE, PHOTO-OXIDATION OF ORGANIC SUBSTRATES, AND PHOTO CATALYSTS
A method for photo-oxidising an organic substrate to form an organic product is disclosed comprising: a) mixing oxygen, a supercritical fluid, a photocatalyst, a liquid fluorous solvent and an organic substrate to form a mixture; and b) irradiating the mixture to form an organic product. Also disclosed is a method for separating a photocatalyst from an organic product comprising the steps of: a) providing a mixture comprising a supercritical fluid; an organic product; a fluorous solvent; a photocatalyst; and optionally an organic substrate and optionally oxygen; wherein the organic product, fluorous solvent, photocatalyst and optional organic substrate and optional oxygen are dissolved in the supercritical fluid; and b) reducing the pressure of the mixture to a pressure below the critical pressure of the supercritical fluid in order to form a gaseous phase.
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(2014/09/30)

Efficient Solar Photooxygenation with Supported Porphyrins as Catalysts
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Ribeiro, Sonia,Serra, Armenio C.,A.RochaGonsalves, Antonio M. D'
p. 134 - 137
(2013/03/13)

Surface area control and photocatalytic activity of conjugated microporous poly(benzothiadiazole) networks
Conjugated microporous polymers (CMPs) with controlled specific surface area have been prepared through Sonogashira-Hagihara cross-coupling reactions in the presence of silica nanoparticles as templating agents. The CMPs act as heterogeneous photosensitizers for producing singlet oxygen in a continuous flow synthesis (see picture). Copyright
Zhang, Kai,Kopetzki, Daniel,Seeberger, Peter H.,Antonietti, Markus,Vilela, Filipe
p. 1432 - 1436
(2013/03/13)

SEPARATION TECHNIQUE, PHOTO-OXIDATION OF ORGANIC SUBSTRATES, AND PHOTO CATALYSTS
A method for photo -oxidising an organic substrate to form an organic product is disclosed comprising: a) mixing oxygen, a supercritical fluid, a photocatalyst, a liquid fluorous solvent and an organic substrate to form a mixture; and b) irradiating the mixture to form an organic product. Also disclosed is a method for separating a photocatalyst from an organic product comprising the steps of: a) providing a mixture comprising a supercritical fluid; an organic product; a fluorous solvent; a photocatalyst; and optionally an organic substrate and optionally oxygen; wherein the organic product, fluorous solvent, photocatalyst and optional organic substrate and optional oxygen are dissolved in the supercritical fluid; and b) reducing the pressure of the mixture to a pressure below the critical pressure of the supercritical fluid in order to form a gaseous phase.
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Page/Page column 19

(2013/06/05)

Visible-light photosensitized oxidation of α-terpinene using novel silica-supported sensitizers: Photooxygenation vs. photodehydrogenation
Three silica-immobilized organic photocatalysts, based on rose bengal (RB), antraquinone-2-carboxylic acid (ANT-COOH) and a new cyanoanthracene derivative (DBTP-COOH), were prepared and characterized. Their efficiency for the photooxidation of α-terpinene was compared to that of their soluble counterparts. In solution, the three sensitizers showed high quantum yield of singlet oxygen production. Significant autooxidation to p-cymene occurred in the absence of catalyst while the mechanism of the sensitized reaction strongly depended on sensitizer structure. With DBTP and RB materials, ascaridole was rapidly produced by singlet oxygen addition. In contrast, ANT-based sensitizers favored photodehydrogenation to p-cymene through an electron-transfer step inducing a radical chain reaction, followed by further p-cymene oxidation upon prolonged irradiation. The highest efficiency and selectivity were obtained for photooxygenation with DBTP-based materials, and for photodehydrogenation with ANT-based materials, these properties make them attractive for future applications as immobilized photocatalyst in solar synthesis, waste treatment, and microflow reactors.
Ronzani, Filippo,Costarramone, Nathalie,Blanc, Sylvie,Benabbou, Abdelhamid Khalil,Bechec, Mickael Le,Pigot, Thierry,Oelgemoeller, Michael,Lacombe, Sylvie
p. 164 - 174
(2013/07/05)

Ozonolysis of bicyclic 1,2-dioxines: Initial scope and mechanistic insights
The ozonolysis of bicyclic 1,2-dioxines was investigated using a variety of 1,4-disubstituted 1,2-dioxines along with a 1,3-dialkyl and steroidal example, with yields ranging from moderate to excellent. Two different pathways were observed upon reaction of the 1,4-disubstituted 1,2-dioxines with ozone; one pathway saw the "expected" results, that is, cleavage of the olefinic moiety with generation of 1,4-dicarbonyl 1,2-dioxines, while the other pathway revealed a previously unobserved rearrangement involving cleavage of the peroxide linkage along with loss of either CO or CO2. Several unsymmetrical ozonolyses were also performed to further investigate the origins of this rearrangement, and initial mechanistic insights into the fragmentation pathways are discussed.
Cain, Nicole M.,Tiekink, Edward R. T.,Taylor, Dennis K.
experimental part
p. 3808 - 3819
(2012/06/29)

Microphotochemistry using 5-mm light-emitting diodes: Energy-efficient photooxidations
Commercial, inexpensive 5-mm milliwatt light-emitting diodes are effective sources for batch microphotochemical oxidations. Using limited quantities of singlet oxygen, these oxidations are atom economical and therefore useful for labeling experiments with rare isotopes. Georg Thieme Verlag Stuttgart · New York.
Carney, John M.,Hammer, Reagan J.,Hulce, Martin,Lomas, Chad M.,Miyashiro, Dayna
experimental part
p. 2560 - 2566
(2012/09/07)

Generation of singlet oxygen from fragmentation of monoactivated 1,1-dihydroperoxides
The first singlet excited state of molecular oxygen (1O 2) is an important oxidant in chemistry, biology, and medicine. 1O2 is most often generated through photosensitized excitation of ground-state oxygen. 1O2 can also be generated chemically through the decomposition of hydrogen peroxide and other peroxides. However, most of these "dark oxygenations" require water-rich media associated with short 1O2 lifetimes, and there is a need for oxygenations able to be conducted in organic solvents. We now report that monoactivated derivatives of 1,1-dihydroperoxides undergo a previously unobserved fragmentation to generate high yields of singlet molecular oxygen (1O2). The fragmentations, which can be conducted in a variety of organic solvents, require a geminal relationship between a peroxyanion and a peroxide activated toward heterolytic cleavage. The reaction is general for a range of skeletal frameworks and activating groups and, via in situ activation, can be applied directly to 1,1-dihydroperoxides. Our investigation suggests the fragmentation involves rate-limiting formation of a peroxyanion that decomposes via a Grob-like process.
Hang, Jiliang,Ghorai, Prasanta,Finkenstaedt-Quinn, Solaire A.,Findik, Ilhan,Sliz, Emily,Kuwata, Keith T.,Dussault, Patrick H.
supporting information; experimental part
p. 1233 - 1243
(2012/03/27)

Maximising the efficiency of continuous photo-oxidation with singlet oxygen in supercritical CO2 by use of fluorous biphasic catalysis
Using a continuous fluorous biphasic separation, a photo-oxidation catalyst can be recycled, with increased productivity and a ×20 fold decrease in the amount of catalyst required. The Royal Society of Chemistry 2012.
Hall, Jessica F. B.,Han, Xue,Poliakoff, Martyn,Bourne, Richard A.,George, Michael W.
supporting information; experimental part
p. 3073 - 3075
(2012/04/17)

Photooxygenations in a bubble column reactor
A novel column reactor was constructed and successfully applied to dye-sensitized photooxygenation reactions in aqueous alcohol solutions. The air flow pattern within the narrow glass column could be controlled via the size of the air inlet capillary. Using a 500 μm capillary, a slug flow pattern was realized which allowed for superior mass transfer and light transparency within a thin solvent layer. These features subsequently gave higher conversion rates and isolated yields.
Yavorskyy, Alexander,Shvydkiv, Oksana,Limburg, Carolin,Nolan, Kieran,Delaure, Yan M. C.,Oelgemoeller, Michael
experimental part
p. 888 - 892
(2012/06/18)

Comparison of photo-oxidation reactions in batch and a new photosensitizer-immobilized microfluidic device
A glass microfluidic device has been functionalized with photoactive porphyrins for performing reactions which are mediated by singlet molecular oxygen. The resulting device was used to investigate the photochemical oxidation of cholesterol, α-terpinene, and citronellol under flow conditions, and the results were compared with similar batch reactions.
Lumley, Emily K.,Dyer, Charlotte E.,Pamme, Nicole,Boyle, Ross W.
supporting information
p. 5724 - 5727
(2013/01/15)

High-efficiency microphotooxidation using milliwatt LED sources
Inexpensive milliwatt light emitting diode (LED) sources allow energy- and atom-efficient microphotochemical reactions. Thus, sources constructed from three 120 mW 5 mm diameter 627 nm LED's enable μmol-mmol scale methylene blue-sensitized singlet oxygen photooxidations of various arenes and cyclopentadienones using a 3-5 M excess of oxygen in 82-98% yields.
Carney, John M.,Hammer, Reagan J.,Hulce, Martin,Lomas, Chad M.,Miyashiro, Dayna
supporting information; experimental part
p. 352 - 355
(2011/02/28)

Triple-channel microreactor for biphasic gas-liquid reactions: Photosensitized oxygenations
A triple-channel microreactor fabricated by means of a soft-lithography technique was devised for efficient biphasic gas-liquid reactions. The excellent performance of the microreactor was demonstrated by carrying out photosensitized oxygenations of α-terpinene, citronellol, and allyl alcohols.
Maurya, Ram Awatar,Park, Chan Pil,Kim, Dong-Pyo
supporting information; experimental part
p. 1158 - 1163
(2011/10/09)

Efficient photosensitized oxygenations in phase contact enhanced microreactors
A transparent dual-channel microreactor with highly enhanced contact area-to-volume ratio was fabricated for efficient photosensitized oxygenations. The dual-channel microreactor shielded with polyvinylsilazane (PVSZ) consisting of an upper channel for liquid flow and a lower channel for O2 flow, allows sufficient phase contact along the parallel channels through a gas permeable PDMS membrane for maintaining the O2 saturated solution. Under full exposure of reactants to light, the reactions in high concentration are completed in minutes rather than hours that it takes to complete in a batch reactor. Moreover, the scale-up process using the microreactor revealed higher productivity than the batch reactor, which would be valuable for the practical applications in a broad range of gas-liquid chemical reactions.
Park, Chan Pil,Maurya, Ram Awatar,Lee, Jang Han,Kim, Dong-Pyo
experimental part
p. 1941 - 1945
(2012/03/22)

Highly efficient continuous flow reactions using singlet oxygen as a "Green" reagent
Described is a new method for the efficient in situ production of singlet oxygen in a simple continuous flow photochemical reactor. The extremely large interfacial area generated by running the biphasic mixture in a narrow channel at a high flow rate ensures high throughput as well as fast and efficient oxidation of various alkenes, 1,3-dienes, and thioethers on a preparative scale.
Levesque, Francois,Seeberger, Peter H.
supporting information; experimental part
p. 5008 - 5011
(2011/12/04)

Covalently immobilized porphyrins on silica modified structures as photooxidation catalysts
Heterogeneous photooxidation catalysts were prepared by the covalent linkage of a porphyrin to aminoalkylated silica particles by chlorosulphonation activation of the porphyrin nucleus. These catalysts were tested in [4+2] cycloaddition and ene reactions promoted by singlet oxygen. Photooxidation of substrates originates high yields of products but with longer reaction times compared to the free porphyrin catalysts. Quenching of singlet oxygen by the silica structure can be the plausible explanation. In the case of the ene reaction with citronellol the supported catalysts originate a distribution of the regioisomeric products which is opposite to that of the homogeneous catalyst.
Ribeiro, Sónia M.,Serra, Arménio C.,Rocha Gonsalves, A.M.d'A.
experimental part
p. 121 - 127
(2010/10/01)

Dimethylsulfoxide as a kinetic booster for the chemical generation of singlet oxygen in methanol
The kinetic booster effect of dimethylsulfoxide on the chemical generation of singlet oxygen, 1O2, from the disproportionation of hydrogen peroxide catalyzed by molybdate ions in methanol has been evidenced by detection of the IR luminescence of 1O2 at 1270 nm and by 95Mo NMR spectroscopy. DMSO interacts rapidly, through a direct oxygen transfer with the stable tetraperoxomolybdate Mo(O2) 42-, leading to DMSO2 and to the unstable triperoxomolybdate Mo(02)32-, which releases 1O2. The procedure was applied to accelerate the dark singlet oxygenation of β-citronellol and α-terpinene.
Collinet-Fressancourt, Marion,Azaroual, Nathalie,Aubry, Jean-Marie,Nardello-Rataj, Véronique
experimental part
p. 6531 - 6534
(2011/02/24)

The influence of the support on the singlet oxygen quantum yields of porphyrin supported photosensitizers
A halogenated porphyrin was covalently supported on aminoalkylated silica and aminoalkylated Merrifield polymer through a chlorosulfonation reaction. The supported porphyrin was tested for the photoxidation of α-terpinene. The kinetics of photocatalysis were evaluated using 9,10-dimethylanthracene as target and singlet oxygen formation quantum yield was calculated. The influence of the support, silica, Merrifield and other polymers, on the quenching of singlet oxygen were also evaluated.
Pineiro, Marta,Ribeiro, Sonia M.,Serra, Armenio C.
experimental part
p. 51 - 63
(2010/08/22)

Synthesis and chemistry of 2,3-dioxabicyclo[2.2.2]octane-5,6-diols
(Chemical Equation Presented) 1,4-Disubstituted 2,3-dioxabicyclo[2.2.2]oct- 5-enes were dihydroxylated with osmium tetroxide to yield diols anti to the peroxide linkage in a highly selective manner. Reduction of the peroxide bond furnished cyclohexane-1,2,3,4-tetraols with toxocarol relative stereochemistry in excellent yield. This new methodology was employed to synthesize the natural product (1S,2R,3S,4R,5R)-2-methyl-5-(propan-2-yl)cyclohexane-1,2,3,4-tetrol (1) in a short sequence from (R)-α-phellandrene. Moreover, during the study of the chemistry of 2,3-dioxabicyclo[2.2.2]octane-5,6-diols a hitherto unknown rearrangement was discovered which has wide applicability for the synthesis of 1,4-dicarbonyls, including optically enriched synthons. A broad range of mechanistic investigations applicable to this rearrangement are also reported.
Valente, Peter,Avery, Thomas D.,Taylor, Dennis K.,Tiekink, Edward R. T.
experimental part
p. 274 - 282
(2009/04/10)