Photophysics and photochemistry of NIR absorbers derived from cyanines: key to new technologies based on chemistry 4.0

• Bernd Strehmel,
• Christian Schmitz,
• Ceren Kütahya,
• Yulian Pang,
• Anke Drewitz and
• Heinz Mustroph

Beilstein J. Org. Chem. 2020, 16, 415–444, doi:10.3762/bjoc.16.40

Reversible photoswitching of the DNA-binding properties of styrylquinolizinium derivatives through photochromic [2 + 2] cycloaddition and cycloreversion

• Sarah Kölsch,
• Heiko Ihmels,
• Jochen Mattay,
• Norbert Sewald and
• Brian O. Patrick

Beilstein J. Org. Chem. 2020, 16, 111–124, doi:10.3762/bjoc.16.13

• biological activity on and off due to the reversibility of the photoreaction [15]. Indeed, the application of light to induce and control bioactivity of pharmaceuticals or bio(macro)molecules has been convincingly demonstrated in the emerging field of photopharmacology [16][17][18]. Consequently, several

• switching of binding properties [36]. Apparently, styryl-substituted aromatic derivatives could fill this gap because the [2 + 2] photocyclization reaction of stilbenes and derivatives thereof is a well-established reversible photoreaction [37][38][39][40][41][42][43][44][45][46], and styryl dyes, in

• acetonitrile solution at 520–535 nm (3a), 420–470 nm (3b and 3c), and >395 nm (3d), and the photoreaction was monitored photometrically. Notably, the amino-substituted derivative 3a did not react under these conditions, as indicated by only marginal changes of the absorption spectrum (Figure 5A). Presumably

Photoreversible stretching of a BAPTA chelator marshalling Ca²⁺-binding in aqueous media

• Aurélien Ducrot,
• Arnaud Tron,
• Robin Bofinger,
• Ingrid Sanz Beguer,
• Jean-Luc Pozzo and
• Nathan D. McClenaghan

Beilstein J. Org. Chem. 2019, 15, 2801–2811, doi:10.3762/bjoc.15.273

• the quantum yield of the photoisomerization reaction (λex = 365 nm) [40]. For solutions of 1E in the absence and presence of Ca2+, the measured quantum yields were identical (0.08) suggesting that the ion does not influence the efficiency of the photoreaction. In order to unambiguously prove the

• spectrofluorometer fitted with a PMT detector and exciting with a 450 W Xe lamp across a double monochromator, and were corrected for instrumental response. Photoreaction quantum yields were determined upon excitation at 365 nm using the couple potassium ferrioxalate–phenanthroline as a chemical actinometer on an

• optical bench equipped with a 150 W Hg–Xe lamp and a monochromator [40]. Samples (40 μM) were stirred during the irradiation and the amount of converted material was determined at 2 min intervals by UV–vis spectroscopy following the disappearance of the band at 362 nm. The error in the photoreaction

A photochemical determination of luminescence efficiency of upconverting nanoparticles

• Baptiste Amouroux,
• Clément Roux,
• Jean-Claude Micheau,
• Fabienne Gauffre and
• Christophe Coudret

Beilstein J. Org. Chem. 2019, 15, 2671–2677, doi:10.3762/bjoc.15.260

• kinetic traces were recorded at 650 nm and the data was processed in order to obtain the initial rate of the photoreaction (Figure 3). Beside these experiments, controls were made to rule out the possibility of thermal effect (irradiation of the actinometer alone with the 976 nm laser) or the possible

Mono- and bithiophene-substituted diarylethene photoswitches with emissive open or closed forms

• A. Lennart Schleper,
• Mariano L. Bossi,
• Vladimir N. Belov and
• Stefan W. Hell

Beilstein J. Org. Chem. 2019, 15, 2344–2354, doi:10.3762/bjoc.15.227

• in MeCN. A similar behavior has been recently reported and ascribed to the so-called Urbach tail effect [19][20], i.e., the ring-closing photoreaction is induced by absorbing very weak hot bands of the OF, in the visible range. Neither nonoxidized DAEs, nor the asymmetric compound AsOTh1 show this

Photochemical generation of the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical from caged nitroxides by near-infrared two-photon irradiation and its cytocidal effect on lung cancer cells

• Ayato Yamada,
• Manabu Abe,
• Yoshinobu Nishimura,
• Shoji Ishizaka,
• Masashi Namba,
• Taku Nakashima,
• Kiyofumi Shimoji and
• Noboru Hattori

Beilstein J. Org. Chem. 2019, 15, 863–873, doi:10.3762/bjoc.15.84

• generation of TEMPO in the bulk photoreaction was found to be k = 1.6 × 10–5 s−1. The amount of photochemically released TEMPO radical was determined by comparing the EPR intensity with the calibration curve of the standard TEMPO sample (Supporting Information File 1, Figure S4). The chemical yield of TEMPO

• was 80% after 10 min irradiation in benzene under air atmosphere (Figure 2g). Secondary photoreaction of TEMPO gradually decreased the chemical yield of TEMPO. The quantum yield (Φ) for photochemical release of the TEMPO radical was 2.5% at ≈1% conversion in the photolysis of 2a in benzene under

• Information File 1, Figure S6 for 2b). The typical EPR signals of TEMPO were also observed after TP excitation of 2a and 2b (Supporting Information File 1, Figure S7). The formation of TEMPO at 740 nm, k740 = 4.9 × 10−6 s−1 in the bulk photoreaction, was the fastest in the TP-uncaging reaction of 2a (Figure 3

Diazirine-functionalized mannosides for photoaffinity labeling: trouble with FimH

• Femke Beiroth,
• Tomas Koudelka,
• Thorsten Overath,
• Stefan D. Knight,
• Andreas Tholey and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2018, 14, 1890–1900, doi:10.3762/bjoc.14.163

• ) and after photoreaction (B) with mannoside 3. Intact protein ESIMS spectra of FimHtr labeling with diazirine derivative 3 with (A) 50% acetonitrile or (B) 10% DMSO additive. (C) Minor peak at 1412.8578, as part of spectrum A, representing the covalently bound label. Zoom into the signal at charge

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

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

• will be covered in the next sections. Photoreaction of 6-hydroxy-2,3-benzotropone (239) was reported by Yoshioka and Hoshino (Scheme 43) [165]. The irradiation of 239 in methanol with Pyrex-filtered light gave the products 274 and 275 in 25% and 2% yields, respectively, accompanied by undefined

The photodecarboxylative addition of carboxylates to phthalimides as a key-step in the synthesis of biologically active 3-arylmethylene-2,3-dihydro-1H-isoindolin-1-ones

• Ommid Anamimoghadam,
• Saira Mumtaz,
• Anke Nietsch,
• Gaetano Saya,
• Cherie A. Motti,
• Jun Wang,
• Peter C. Junk,
• Ashfaq Mahmood Qureshi and
• Michael Oelgemöller

Beilstein J. Org. Chem. 2017, 13, 2833–2841, doi:10.3762/bjoc.13.275

• [41], followed by amination [42] furnishes the desired target compounds. The amino group is introduced in the final step as it would otherwise interfere with the desired photoreaction. In fact, amines are very potent electron donors and are easily oxidized by the excited phthalimide chromophore [43

• compound 4, originating from intramolecular nucleophilic substitution, was obtained as a byproduct in 25–30%. Noteworthy, compound 4 is formed as the only product when 1a is treated with organometallic reagents [48][49][50]. When the photoreaction was repeated in a 1:1 mixture of acetone and pH 7 buffer at

Cycloheximide congeners produced by Streptomyces sp. SC0581 and photoinduced interconversion between (E)- and (Z)-2,3-dehydroanhydrocycloheximides

• Li Yang,
• Ping Wu,
• Jinghua Xue,
• Huitong Tan,
• Zheng Zhang and
• Xiaoyi Wei

Beilstein J. Org. Chem. 2017, 13, 1039–1049, doi:10.3762/bjoc.13.103

• of C6–Cα bond (Table 2). In respect to the photoreaction path, it is predicted that the Z/E isomerization of 2a/3a is impossible to take place along the S1 surface due to the presence of large rotational barrier (>25 kcal/mol) in accessing the twisted intermediates (Figure 6). Instead, radiationless

• &HLYP/TZVP calculated spectra of the mixture of (R)-2/3 (7:3) and individual (R)-2 and (R)-3 in MeOH (σ = 0.38 eV, shift = +18 nm, scaling factor = 0.44, 0.14, and 0.13, respectively). UPLC analysis of photoreaction products of 2 (around tR = 7.5 min) and 3 (around tR = 11.5 min). Potential energy

• surfaces of 2a/3a in the S0, S1, and T1 states, geometries of key points in the surfaces, and proposed photoreaction path (dashed arrow: vibrational relaxation; wavy arrow: ISC; double headed arrow: energy gap between the two points). 1H (500 MHz) and 13C (125 MHz) NMR data of 1–3 in CD3OD. Relative

The reductive decyanation reaction: an overview and recent developments

• Jean-Marc R. Mattalia

Beilstein J. Org. Chem. 2017, 13, 267–284, doi:10.3762/bjoc.13.30

• refer to method B [125][127]. Photoreaction of dibenzylmalononitrile with 81 [128]. Examples of decyanation promoted in acid or basic media [129][131][134][135]. Mechanism proposed for the base-induced reductive decyanation of diphenylacetonitriles [136]. Reductive decyanation of triarylacetonitriles

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

• photolysis of dyads 1 and 2. Photoreaction pathways generating biradical and singlet oxygen species of a sensitizer (S), like SP, KP or TPA, covalently linked to Ch. The obtained percentages under anaerobic conditions are given in parenthesis. Photophysical parameters of dyads in CH2Cl2. Supporting

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

• –O bond with radical initiators [7][8][9][10][11][12][13][14][15] (Scheme 1a) or using thermal [16][17][18][19][20] or photoreaction conditions [21][22][23][24][25][26][27] (Scheme 1b). An alternative route to iminyl radicals is the single-electron reduction of oxime derivatives mediated by the

Synthesis of carbohydrate-scaffolded thymine glycoconjugates to organize multivalency

• Anna K. Ciuk and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2015, 11, 668–674, doi:10.3762/bjoc.11.75

• carbohydrate-scaffolded glycothymine system and showed intramolecular syn-[2 + 2] photocycloaddition as planned. This photoreaction changes the conformational availability of the conjugated α-D-mannosyl ligands and thus adds a regulating parameter to multivalency studies. Biological assays employing this type

Visible light photoredox-catalyzed deoxygenation of alcohols

• Daniel Rackl,
• Viktor Kais,
• Peter Kreitmeier and
• Oliver Reiser

Beilstein J. Org. Chem. 2014, 10, 2157–2165, doi:10.3762/bjoc.10.223

• temperatures can be manipulated very conveniently by heating in a conventional oil bath while carrying out the photoreaction. Also light pollution is kept to a minimum, which renders the apparatus an optimal device for the fast setup of test reactions. In agreement with the reduction potentials, 3,5-bis

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

• RF preparations in order to alter the quantum yield of the photoreaction without quenching the fluorescence of RF [81]. Ascorbic acid and sodium azide are the two most studied external quenchers for RF photoreactions. Both these compounds reduce the photodegradation of RF with different quenching

Multichromophoric sugar for fluorescence photoswitching

• Stéphane Maisonneuve,
• Rémi Métivier,
• Pei Yu,
• Keitaro Nakatani and
• Juan Xie

Beilstein J. Org. Chem. 2014, 10, 1471–1481, doi:10.3762/bjoc.10.151

• , 9-OF undergoes a cyclisation photoreaction yielding the molecule in its colored and non-fluorescent closed form (9-CF), as revealed by the appearance of a large absorption band peaking in the 500–700 nm range (Figure 3c, full blue line). The photostationary state (PSS) reached under 335 nm

Visible-light photoredox catalyzed synthesis of pyrroloisoquinolines via organocatalytic oxidation/[3 + 2] cycloaddition/oxidative aromatization reaction cascade with Rose Bengal

• Carlos Vila,
• Jonathan Lau and
• Magnus Rueping

Beilstein J. Org. Chem. 2014, 10, 1233–1238, doi:10.3762/bjoc.10.122

• % yield (Table 1, entry 12). With the optimal conditions in hand, we examined the substrate scope for the photoreaction catalyzed by Rose Bengal (Scheme 2). Various tetrahydroisoquinolines with different electron-withdrawing groups (R2) such as methyl ester (1a), ethyl ester (1b), tert-butyl ester (1c

Direct and indirect single electron transfer (SET)-photochemical approaches for the preparation of novel phthalimide and naphthalimide-based lariat-type crown ethers

• Dae Won Cho,
• Patrick S. Mariano and
• Ung Chan Yoon

Beilstein J. Org. Chem. 2014, 10, 514–527, doi:10.3762/bjoc.10.47

• HClO4 (Scheme 8) [33]. Acidic photoreaction mixtures were used for the photochemical processes to cause protonation and prevent undesirable SET from nitrogen donor sites in the side chains. At the outset, we expected that photoirradiation of the polyethylenoxy- and polymethylene-linked phthalimides 32

Synthesis of nucleotide–amino acid conjugates designed for photo-CIDNP experiments by a phosphotriester approach

• Tatyana V. Abramova,
• Olga B. Morozova,
• Vladimir N. Silnikov and
• Alexandra V. Yurkovskaya

Beilstein J. Org. Chem. 2013, 9, 2898–2909, doi:10.3762/bjoc.9.326

• reduction (with the characteristic time of less than 1 μs) of the guanosyl radical by means of electron transfer from the linked tryptophan moiety in conjugate 6. This efficient reduction was strictly confirmed by comparing CIDNP kinetics of the photoreaction of conjugate 6 (with 2,2’-dipyridyl as

Topochemical control of the photodimerization of aromatic compounds by γ-cyclodextrin thioethers in aqueous solution

• Hai Ming Wang and
• Gerhard Wenz

Beilstein J. Org. Chem. 2013, 9, 1858–1866, doi:10.3762/bjoc.9.217

• using the solvent peaks as internal references, and the coupling constants (J) were measured in Hz. Photoreaction procedures: Aqueous solutions of the native CDs or γ-CD thioethers (25 mL, 6.0 mM) were added into glass vials containing excess amounts of the guest molecules. To evaluate the salting-out

Electron self-exchange activation parameters of diethyl sulfide and tetrahydrothiophene

• Martin Goez and
• Martin Vogtherr

Beilstein J. Org. Chem. 2013, 9, 1448–1454, doi:10.3762/bjoc.9.164

• photoreaction after the stage of the electron transfer. Two other demands on the sensitizer are imposed by the necessity of maximizing the CIDNP effects, because intrinsically low enhancement factors are expected in consequence [6] of the very high g values of sulfur-centered radical cations. First, to suppress

• . The CIDNP effects observed in the photoreaction of DES sensitized by TPP+ in acetonitrile are typical [12] for a self-exchange: Only the starting materials exhibit CIDNP, i.e., no other spin-polarized products are formed; hence, the radicals must ultimately stabilize by reverse electron transfer. In

Electron and hydrogen self-exchange of free radicals of sterically hindered tertiary aliphatic amines investigated by photo-CIDNP

• Martin Goez,
• Isabell Frisch and
• Ingo Sartorius

Beilstein J. Org. Chem. 2013, 9, 437–446, doi:10.3762/bjoc.9.46

• pulsed laser triggers a photoreaction; after a short delay, the polarizations of the products are probed with an NMR pulse; variation of the delay yields the kinetics. The method is very well suited to study bimolecular reactions of the free radicals, because typical NMR pulses are of microsecond

• electron self-exchange, the condition for a monoexponential decay is very likely to be fulfilled. Hence, the observed decay rate constant in the photoreaction with XA may well be a compound quantity, (kHT + kdep). In that case, no residual CIDNP signal is expected because the α hydrogen of the amine is

• ) of triisopropylamine (TIPA) in the photoreaction with xanthone (XA) as functions of the delay (given at the respective trace) between the laser flash and the sampling NMR pulse. Note the exponential increase of the delay with the spectrum number. Excitation intensity, ca. 80 mJ per flash; NMR pulse

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

• generated was compared to that generated by HPLC analysis; however, although both sets of data showed the same trend, there were differences in concentration values. This was assumed to be due to continued photoreaction in the HPLC samples (thus leading to inaccurate HPLC data), and indeed use of the online

Photochemistry with laser radiation in condensed phase using miniaturized photoreactors

• Elke Bremus-Köbberling,
• Arnold Gillner,
• Frank Avemaria,
• Céline Réthoré and
• Stefan Bräse

Beilstein J. Org. Chem. 2012, 8, 1213–1218, doi:10.3762/bjoc.8.135

• HPLC and GC [50]. Because of the miniaturization, online analysis is especially suitable for our setup. We therefore investigated whether the photoreaction can be realized in miniaturized photoreactors and to what extent the use of a laser as a photon source is advantageous. The irradiation of 2