Biocatalysis for the application of CO₂ as a chemical feedstock

• Apostolos Alissandratos and
• Christopher J. Easton

Beilstein J. Org. Chem. 2015, 11, 2370–2387, doi:10.3762/bjoc.11.259

• source of reducing equivalents is sunlight [20]. Solar energy may be directly utilised through the application of photosynthetic machinery employed by photoautotrophs to carry out the “light reactions” of photosynthesis. This will require technological advances, such as the development of bioreactors

• capable of maximising exposure to sunlight [157]. Another limitation to any approach relying on photosynthesis to harvest solar energy is the inherently poor efficiency and sensitivity of photosynthetic pigments and reaction centres, as highlighted by Michel [158]. An alternative approach is to convert

Photoinduced 1,2,3,4-tetrahydropyridine ring conversions

• Baiba Turovska,
• Henning Lund,
• Viesturs Lūsis,
• Anna Lielpētere,
• Edvards Liepiņš,
• Sergejs Beljakovs,
• Inguna Goba and
• Jānis Stradiņš

Beilstein J. Org. Chem. 2015, 11, 2166–2170, doi:10.3762/bjoc.11.234

• , Langelandsgade 140, DK 8000 Aarhus, Denmark 10.3762/bjoc.11.234 Abstract Stable heterocyclic hydroperoxide can be easily prepared as a product of fast oxidation of a 1,2,3,4-tetrahydropyridine by 3O2 if the solution is exposed to sunlight. The driving force for the photoinduced electron transfer is calculated

• (Figure 1). Moreover, it was found that tetrahydropyridine 1 (Figure 2) reacts with dioxygen if the solution is exposed to intense sunlight. In order to study this reaction, the solution of 1 (0.5 g, 1.51 mmol) was left under an irradiation of intense sunlight and continuously purged with dioxygen (~9.1

• the sunlight in summer at 300 nm is sufficient to initiate the photooxygenation of 1. Direct reactions of dioxygen with organic substrates in the absence of a catalyst are usually slow, unless the substrate is a particularly good reducing agent. Excited state species are easier to oxidize than the

Effective ascorbate-free and photolatent click reactions in water using a photoreducible copper(II)-ethylenediamine precatalyst

• Redouane Beniazza,
• Natalia Bayo,
• Florian Molton,
• Carole Duboc,
• Stéphane Massip,
• Nathan McClenaghan,
• Dominique Lastécouères and
• Jean-Marc Vincent

Beilstein J. Org. Chem. 2015, 11, 1950–1959, doi:10.3762/bjoc.11.211

• mercury lamp (type TLC = thin-layer chromatography, 365 nm), or by a 23 W fluorescent bulb, or by ambient/sunlight. In water, a much poorer hydrogen atom donating solvent, the photoreduction of 1 proved inefficient. Interestingly, EPR studies revealed that complex 1 could nonetheless be effectively

• effective, that the UVA photons (350–400 nm) present in sunlight/ambient light were sufficient to achieve the reduction with satisfactory rates, i.e., ≈30 min and 60 min when the samples were exposed behind a window to direct light of a sunny or a rainy day, respectively. It should also be noted that over

• shown by UV–vis spectroscopy (Figure 2). This rate is comparable to that observed previously with the analogous complex 2, for which a photoreduction quantum yield close to unity has been determined in THF [14]. Because of such a high efficiency, the photoreduction proceeded well under direct sunlight

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

• , and the atmosphere can be completely mineralized by this means. Furthermore, self-cleaning glass [18], bathroom and kitchen tiles, thinly coated with TiO2, are supplied by several manufacturers. As sunlight falls on the ceramics the oxidative process is promoted and the material stays clean. Another

• electron-deficient alkenes; including maleic anhydride, maleic acid and related nitriles, in good yields (Scheme 10). Excess alkene was required to act as a trap for the conduction band electrons. In one instance a multigram reaction was successfully carried out with sunlight as the irradiation source

A hybrid electron donor comprising cyclopentadithiophene and dithiafulvenyl for dye-sensitized solar cells

• Gleb Sorohhov,
• Chenyi Yi,
• Michael Grätzel,
• Silvio Decurtins and
• Shi-Xia Liu

Beilstein J. Org. Chem. 2015, 11, 1052–1059, doi:10.3762/bjoc.11.118

• ). Electronic absorption spectra of 1 (blue line) and 2 (red line) in CH2Cl2 solutions. Photovoltaic performance of the two sensitizers. Photocurrent density (J) as a function of voltage (V) for 1 (black and blue curves) and 2 (red and green curves) measured under standard air mass 1.5 and simulated sunlight at

Photocatalytic nucleophilic addition of alcohols to styrenes in Markovnikov and anti-Markovnikov orientation

• Martin Weiser,
• Sergej Hermann,
• Alexander Penner and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2015, 11, 568–575, doi:10.3762/bjoc.11.62

• different electron density. Representative mesoflow reactor experiments allowed to significantly shorten the irradiation times and to use sunlight as “green” light source. Keywords: electron transfer; perylene bisimide; photocatalysis; photochemistry; pyrene; Introduction Photocatalysts are organic or

• inorganic compounds that couple the physical process of light absorption with a chemical reaction by means of time, space and energetics, in order to catalyse it. With respect to the “green” character of sunlight as unlimited natural light source and the availability of LEDs as cheap and reliable artificial

• photoirradiation by both sunlight and green light-emitting diodes. Furthermore, based on Ered(PDI/PDI●−) = −0.28 V (measured by cyclic voltammetry, vs SCE, see Supporting Information File 1) and E00 = 2.35 eV (see Supporting Information File 1), PDI is an electron deficient chromophore with an excited state

Electrochemical oxidation of cholesterol

• Jacek W. Morzycki and
• Andrzej Sobkowiak

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

• toxic products. These are formed due to oxidation reactions caused by the contact with oxygen, the exposure to sunlight, heating treatments, etc. [5][6][7]. Furthermore, they can be generated in the human organism through different oxidation processes, some of which require enzymes. Cholesterol

Photovoltaic-driven organic electrosynthesis and efforts toward more sustainable oxidation reactions

• Bichlien H. Nguyen,
• Robert J. Perkins,
• Jake A. Smith and
• Kevin D. Moeller

Beilstein J. Org. Chem. 2015, 11, 280–287, doi:10.3762/bjoc.11.32

• projects and the operation of solar-driven toys [10]. Both can be used to power an electrochemical reaction, and both offer the opportunity to perform oxidation reactions that consume only sunlight and generate hydrogen gas as the only byproduct. The experimental setup for a photochemically driven reaction

• variations in sunlight intensity, as the current through the cell can be adjusted very quickly using these methods. With an experimental design in place, a series of direct and indirect oxidation reactions were used to determine the viability of the method [11][12]. Discussion Direct oxidation Initial

• reason, the sunlight-driven oxidation reactions were extended to the recycling of chemical oxidants. Three examples are shown in Scheme 4 [12] where each was chosen for its unique feature related to the indirect electrochemical approach. In the first reaction (Scheme 4a), an asymmetric dihydroxylation

Oxidative phenylamination of 5-substituted 1-hydroxynaphthalenes to N-phenyl-1,4-naphthoquinone monoimines by air and light “on water”

• Julio Benites,
• Juan Meléndez,
• Cynthia Estela,
• David Ríos,
• Luis Espinoza,
• Iván Brito and
• Jaime A. Valderrama

Beilstein J. Org. Chem. 2014, 10, 2448–2452, doi:10.3762/bjoc.10.255

• [1][2][3][4][5][6]. In this context, the sunlight-induced synthesis of 5-hydroxy-1,4-naphthoquinone (2, juglone, Figure 1) by sensitized phothooxygenation of 1,5-dihydroxynaphthalene (1, 1,5-DHN) [7] and the preparation of 2-phenylamino-1,4-naphthoquinones by reaction of 1,4-naphthoquinones with

• then in the same flask, the arylamination of 2 to the respective aminoquinones was accomplished [14]. The on-water photooxygenation of 1,5-DHN (1) was carried out for 5 h in round-bottom flasks, under the presence of 1.6 mmol % of rose bengal (RB) as singlet oxygen sensitizer, by using sunlight

• (Canchones Experimental Center in Iquique/Chile, latitude 20°26´43.80´´ S, 990 m above sea level) and green LEDs as photochemical sources. Meanwhile, a gently stream of air was bubbled through the solutions. Under these conditions juglone (2) was isolated in 81% (sunlight) and 55% (LEDs) yields. On the other

Scalable synthesis of 5,11-diethynylated indeno[1,2-b]fluorene-6,12-diones and exploration of their solid state packing

• Bradley D. Rose,
• Peter J. Santa Maria,
• Aaron G. Fix,
• Chris L. Vonnegut,
• Lev N. Zakharov,
• Sean R. Parkin and
• Michael M. Haley

Beilstein J. Org. Chem. 2014, 10, 2122–2130, doi:10.3762/bjoc.10.219

• shock sensitive [22], a fact that we can readily reaffirm; and (4) the iodine atoms on 9 are quite labile as we often observed formation of elemental iodine if solutions of 9 were exposed to heat or sunlight. If we wanted to obtain quantities of diones 8 beyond 20–30 milligrams at a time, we had to

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

• number of factors that are discussed as follows: Radiation source, intensity and wavelengths The emission characteristics of the radiation source are an important factor that plays a significant role in the photodegradation of RF. Around 30% of RF is destroyed by sunlight in milk within only 30 minutes

Synthesis of new, highly luminescent bis(2,2’-bithiophen-5-yl) substituted 1,3,4-oxadiazole, 1,3,4-thiadiazole and 1,2,4-triazole

• Anastasia S. Kostyuchenko,
• Vyacheslav L.Yurpalov,
• Aleksandra Kurowska,
• Wojciech Domagala,
• Adam Pron and
• Alexander S. Fisyuk

Beilstein J. Org. Chem. 2014, 10, 1596–1602, doi:10.3762/bjoc.10.165

• ultraviolet, tailing into high energy visible spectral range, giving them yellow to orange-tinted colouration in the solid state. When dissolved, they produce faint yellow coloured solutions exhibiting clear fluorescence properties, perceivable as a blue to bluish-green hue when exposed to direct sunlight

The Ugi four-component reaction as a concise modular synthetic tool for photo-induced electron transfer donor-anthraquinone dyads

• Sarah Bay,
• Gamall Makhloufi,
• Christoph Janiak and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2014, 10, 1006–1016, doi:10.3762/bjoc.10.100

• persistent light-induced charge separation between a donor and an acceptor originates from photosynthesis, nature’s most important process to convert sunlight into chemical energy. One of the most challenging endeavors of mankind is the unlimited generation of electrical energy from sunlight, with great

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

• of sustainable radical-mediated chemical processes under very soft irradiation conditions (e.g., household fluorescence or LED bulbs, halogen lamps, sunlight, Xe lamp), e.g., enantioselective alkylation, cycloaddition, etc. [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Ruthenium- and iridium-based

• delivered, e.g., by household lamps and LED bulbs) can be used; this is a catalytic process without loss of efficiency with irradiation. Photopolymerization under sunlight becomes reachable. The production of the radical or cationic initiating species for the FRP of acrylates or the FRPCP of epoxides

• light sources (Hg, Xe or Hg–Xe lamps, laser diodes) can be obviously employed. However, and with more interest, very soft irradiation conditions (using, e.g., household fluorescence or LED bulbs, halogen lamps or even sunlight) are also suitable to polymerize radical and cationic monomers (see Figure 4

Cyclization of substitued 2-(2-fluorophenylazo)azines to azino[1,2-c]benzo[d][1,2,4]triazinium derivatives

• Aleksandra Jankowiak,
• Emilia Obijalska and
• Piotr Kaszynski

Beilstein J. Org. Chem. 2013, 9, 1873–1880, doi:10.3762/bjoc.9.219

• cyclization was carried out with sunlight and tosylate 1c was isolated in pure form in 90% yield. In contrast, cation 1d partially decomposed during the workup, presumably due to the activation by means of the fluorine atoms and their electron-withdrawing effect. A pure sample of 1d could not be isolated. A

• comparison of the cyclization rates of the three fluorophenylazo derivatives 4b–4d was conducted in NMR tubes exposed to sunlight. The experiment demonstrated that the rate of cyclization increases with increasing number of fluorine atoms, and after 1 h conversion of 4b to 1b was 30%, 4c to cation 1c 80

• pattern that could be ascribed to the cation 1f was detected. Similarly unsuccessful were the attempts to cyclize azopyrazine 5 (halogen lamp/ice bath or sunlight, Figure 4) and azopyrimidine 6 (halogen lamp/reflux); instead complex mixtures of products were obtained. Synthesis of azo precursors Azo

Bromination of hydrocarbons with CBr₄, initiated by light-emitting diode irradiation

• Yuta Nishina,
• Bunsho Ohtani and
• Kotaro Kikushima

Beilstein J. Org. Chem. 2013, 9, 1663–1667, doi:10.3762/bjoc.9.190

• -bromohexane (41%) (Table 2, entry 2). On the other hand, no bromination of toluene occurred under LED irradiation. In this case, light would be absorbed by the aromatic ring of toluene, suppressing the activation of CBr4. Using sunlight in place of LED light, however, resulted in the bromination of the

Organotellurium-mediated living radical polymerization under photoirradiation by a low-intensity light-emitting diode

• Yasuyuki Nakamura and
• Shigeru Yamago

Beilstein J. Org. Chem. 2013, 9, 1607–1612, doi:10.3762/bjoc.9.183

• thermal conditions to give highly controlled polymers [37]. The polymerization proceeded by irradiation with a weak-intensity light source such as a 60–100 W black lamp or sunlight, but we routinely used a high-intensity light source, namely, a 500 W high pressure Hg lamp, combined with a light cutoff

Polymerization of novel methacrylated anthraquinone dyes

• Christian Dollendorf,
• Susanne Katharina Kreth,
• Soo Whan Choi and
• Helmut Ritter

Beilstein J. Org. Chem. 2013, 9, 453–459, doi:10.3762/bjoc.9.48

• [14][15][16]. Coloration of polymers is usually achieved by mixing dyes or pigments with (other) polymeric ingredients. In many cases, the colors rapidly fade or change as well as lose their mechanical properties when exposed to sunlight. More stable polymers can be prepared by the reaction 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

• ] that crystals of the sesquiterpene santonin would literally burst open upon exposure to sunlight can perhaps be considered as the beginning of organic photochemistry. In 1883 Cannizzaro and Sestini [2] investigated this further and reported the formation of photosantonic acid upon irradiation of

Syntheses and properties of thienyl-substituted dithienophenazines

• Annemarie Meyer,
• Eva Sigmund,
• Friedhelm Luppertz,
• Gregor Schnakenburg,
• Immanuel Gadaczek,
• Thomas Bredow,
• Stefan-S. Jester and
• Sigurd Höger

Beilstein J. Org. Chem. 2010, 6, 1180–1187, doi:10.3762/bjoc.6.135

• -acceptor (DA) approach), thereby red-shifting the absorption edge. This is of special importance, as there is still a need for new materials (exhibiting additionally the above mentioned processability criteria) absorbing the longer wavelength region (> 600 nm) of the sunlight spectrum, being required for

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

• oxidation and an intramolecular Heck reaction [149]. Exposure of the quinone 207 to sunlight triggered the formation of benzoxazole 208, which cleaved to form an intermediate iminium salt. Subsequent proton transfer gave the vinylogous carbamate 209 (Scheme 57). After oxidation of the hydroquinone to the

Green oxidations: Titanium dioxide induced tandem oxidation coupling reactions

• Vineet Jeena and
• Ross S. Robinson

Beilstein J. Org. Chem. 2009, 5, No. 24, doi:10.3762/bjoc.5.24

• is known to be highly reactive under sunlight [17] and this seemed to be the most obvious starting point. Initially, 2-hydroxyacetophenone was reacted with o-phenylenediamine under natural sunlight. We were delighted to observe the formation of the quinoxaline derivative in an isolated yield of 90

The first preparative solution phase synthesis of melanotan II

• Vladimir V. Ryakhovsky,
• Georgy A. Khachiyan,
• Nina F. Kosovova,
• Elena F. Isamiddinova and
• Andrey S. Ivanov

Beilstein J. Org. Chem. 2008, 4, No. 39, doi:10.3762/bjoc.4.39

• Vladimir V. Ryakhovsky Georgy A. Khachiyan Nina F. Kosovova Elena F. Isamiddinova Andrey S. Ivanov R&D Dept., Pharm-Sintez, 38 Shosse Entusiastov, 111123 Moscow, Russia 10.3762/bjoc.4.39 Abstract Melanotan II is a synthetic cyclic heptapeptide used to prevent a sunlight-induced skin cancer by