Organic synthesis using photoredox catalysis

• Axel G. Griesbeck

Beilstein J. Org. Chem. 2014, 10, 1097–1098, doi:10.3762/bjoc.10.107

• synthesis, the principles of photoredox chemistry serve as guidelines, i.e., photoinduced electron transfer (PET) kinetics and thermodynamics as expressed in the Rehm–Weller and Marcus equations. For catalytic versions, the photoinduced redox processes require efficient and robust photocatalysts, and in

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

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

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

• quenching rate constants 1kq/A and 3kq/A, respectively). The oxidized form of the dye (PS•+) is formed together with the reduced acceptor (A•−) which lead to initiating radicals [33][48][49]. As a consequence, the PS is consumed (i.e., photolysed or bleached) during the photoinduced electron transfer

• photolysis quantum yield of 0.19 for RB/TA is obtained. Photocyclic initiating system A typical photocyclic initiating system (PCIS) consists of a light absorbing dye (PS), an electron acceptor (A) and an electron donor (D) (Scheme 3). In such systems, upon irradiation photoinduced electron transfer reaction

• possible. The values of the Gibbs free energy change for photoinduced electron transfer is given by the Rehm–Weller equation [56]: , where E* stands for the energy of the excited state. The Coulombic term C is usually neglected in polar solvent. will determine the rate of electron transfer and the dye

Visible-light-induced, Ir-catalyzed reactions of N-methyl-N-((trimethylsilyl)methyl)aniline with cyclic α,β-unsaturated carbonyl compounds

• Dominik Lenhart and
• Thorsten Bach

Beilstein J. Org. Chem. 2014, 10, 890–896, doi:10.3762/bjoc.10.86

• ; Introduction The photoinduced electron transfer (PET) of an amine to an excited oxidant followed by the loss of a cationic leaving group allows accessing a broad variety of α-aminoalkyl radicals [1][2][3][4]. As first shown by Mariano et al. [5][6] and by Pandey et al. [7] a trimethylsilyl (TMS) group is a

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

• reduced through a photoinduced electron transfer with an electron donor eD. A suitable B-Y (or B-Y+) compound leads to a regeneration of PIC and the formation of a radical and an anion (or a radical and a neutral product). Therefore, FRP can be achieved. Examples of PICs in the photopolymerization area

Synthesis of five- and six-membered cyclic organic peroxides: Key transformations into peroxide ring-retaining products

• Alexander O. Terent'ev,
• Dmitry A. Borisov,
• Vera A. Vil’ and
• Valery M. Dembitsky

Beilstein J. Org. Chem. 2014, 10, 34–114, doi:10.3762/bjoc.10.6

• methylenecyclopropanes 28a and 28b under photoinduced electron-transfer conditions is described by a similar scheme (Scheme 10). The reaction was performed in acetonitrile or in a mixture of toluene and acetonitrile with the use of 9,10-dicyanoanthracene (DCA), 1,2,4,5-tetracyanobenzene (TCNB), or N-methyl-quinolinium

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

• their radical cations, which were generated by photoinduced electron transfer from the sulfides to excited 2,4,6-triphenylpyrylium cations, was investigated by time-resolved measurements of chemically induced dynamic nuclear polarization (CIDNP) in acetonitrile. The strongly negative activation

• NMR spectrometer, so the polarizations in the diamagnetic products can be directly sampled by a radiofrequency pulse and manifest themselves as anomalous line intensities in the NMR spectrum. Given an appropriate acceptor/donor combination A/D, photoinduced electron transfer [11] is an expedient route

• ]; both in acetonitrile versus SCE) the opposite order, even with a numerically similar difference, is calculated for the radical pair with D•+, although observations [28][29] that for bifunctional donors comprising both an amine and a sulfide moiety photoinduced electron transfer occurs exclusively from

Spectroscopic characterization of photoaccumulated radical anions: a litmus test to evaluate the efficiency of photoinduced electron transfer (PET) processes

• Maurizio Fagnoni,
• Stefano Protti,
• Davide Ravelli and
• Angelo Albini

Beilstein J. Org. Chem. 2013, 9, 800–808, doi:10.3762/bjoc.9.91

• intermediates. Keywords: aromatic nitriles; persistent radical anion; photochemical activation; photoinduced electron transfer (PET); photooxidant; reactive intermediates; Introduction Redox reactions between organic molecules have a limited scope because of the rarely matched redox potential. On the other

• under mild conditions, avoiding the use of aggressive inorganic reagents otherwise required. Photoinduced electron transfer indeed offers an advantageous access to radical ions as well as the possibility to control the ensuing chemistry, in a way hardly attained through electrochemical or chemical

• subsequent electron-transfer step in the same direction is likely. In contrast, photoinduced electron transfer generates a radical-ion pair. Electron transfer in the reverse direction (back electron transfer, BET) is thus likely and leads again to the starting molecules [7], unless one or both of the radical

Efficient Cu-catalyzed base-free C–S coupling under conventional and microwave heating. A simple access to S-heterocycles and sulfides

• Silvia M. Soria-Castro and
• Alicia B. Peñéñory

Beilstein J. Org. Chem. 2013, 9, 467–475, doi:10.3762/bjoc.9.50

• thiobenzoate anion (PhCOS−), can be effectively achieved by photoinduced electron transfer reactions to form new C–S bonds [4][5]. We have previously described the reactivity of sulfur anions, such as S2− [6], −SCNH(NH2) [7][8], and MeCOS− [9], in photoinduced aromatic radical nucleophilic substitution (SRN1

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

Fifty years of oxacalix[3]arenes: A review

• Kevin Cottet,
• Paula M. Marcos and
• Peter J. Cragg

Beilstein J. Org. Chem. 2012, 8, 201–226, doi:10.3762/bjoc.8.22

• bind to the anionic DNA whereupon 1O2 generated by photoinduced electron transfer from guanine and C60, or alternatively photochemically by C60 alone, cleaves the DNA strand. Ikeda later advanced this line of research to carbohydrate-containing oxacalix[3]arenes that functioned in water [82]. The same

Sexithiophenes as efficient luminescence quenchers of quantum dots

• Christopher R. Mason,
• Yang Li,
• Paul O’Brien,
• Neil J. Findlay and
• Peter J. Skabara

Beilstein J. Org. Chem. 2011, 7, 1722–1731, doi:10.3762/bjoc.7.202

• overcoming processing difficulties associated with devices containing quantum dots alone [15]. The complementary properties of conjugated oligomers/polymers and nanoparticles, and the possible photoinduced electron-transfer processes between them, have led to these materials being combined successfully in

Fine-tuning alkyne cycloadditions: Insights into photochemistry responsible for the double-strand DNA cleavage via structural perturbations in diaryl alkyne conjugates

• Wang-Yong Yang,
• Samantha A. Marrone,
• Nalisha Minors,
• Diego A. R. Zorio and
• Igor V. Alabugin

Beilstein J. Org. Chem. 2011, 7, 813–823, doi:10.3762/bjoc.7.93

• the kinetics of photoinduced electron transfer (PET). The three analogous isomeric lysine conjugates cleaved DNA with different efficiencies (34, 15, and 0% of ds DNA cleavage for p-, m-, and o-substituted lysine conjugates, respectively) consistent with the alkylating ability of the respective

• transformation does not require H-atom abstraction from an external H-atom source such as CHD and DNA, and thus the DNA-damaging ability of this chromophore is not expected to be significant. Photophysics and kinetics of photoinduced electron transfer The fluorescence quenching by triethylamine (Et3N) was

• )-OH/pyridine; f. HCl(g)/MeOH. Photochemical reactions of TFP-substituted aryl alkynes with selected π-systems. In short, the reaction proceeds through the photoinduced electron transfer from thiophene to the singlet excited state of the diaryl acetylene. The initially formed cyclobutene product

Photoinduced electron-transfer chemistry of the bielectrophoric N-phthaloyl derivatives of the amino acids tyrosine, histidine and tryptophan

• Axel G. Griesbeck,
• Jörg Neudörfl and
• Alan de Kiff

Beilstein J. Org. Chem. 2011, 7, 518–524, doi:10.3762/bjoc.7.60

• and tryptophan 8–10 was studied with respect to photoinduced electron-transfer (PET) induced decarboxylation and Norrish II bond cleavage. Whereas exclusive photodecarboxylation of the tyrosine substrate 8 was observed, the histidine compound 9 resulted in a mixture of histamine and preferential

• photoinduced electron-transfer (PET) reactions. N-Alkylated phthalimides typically absorb in the 295 nm region with extinction coefficients around 103. The quantum yields for intersystem crossing ФISC significantly change with the substitution on the imide nitrogen, e.g., ФISC = 0.5 for N-isobutylphthalimide

Donor-acceptor substituted phenylethynyltriphenylenes – excited state intramolecular charge transfer, solvatochromic absorption and fluorescence emission

• Ritesh Nandy and
• Sethuraman Sankararaman

Beilstein J. Org. Chem. 2010, 6, 992–1001, doi:10.3762/bjoc.6.112

• electron transfer [12][13][14][15] and metal ion induced enhancement or quenching of fluorescence [16][17][18][19]. Among these, fluorophores that exhibit excited state ICT are very popular. In this context fluorescent donor-π spacer-acceptor (d-π-a) type molecules are of considerable interest and

• important especially in the in vivo study of biological samples. Otherwise the background blue emission of the biological samples interferes with the fluorescence sensing. The mechanism of fluorescence sensing often involves excited state intramolecular charge transfer (ICT) [8][9][10][11], photoinduced

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

• electron transfer (PET) is inhibited and the system shows an enhanced fluorescence. The binding was dependent on the chain length between the two cations, displaying a maximum stability in the case of the protonated 1,3-diaminopropane. for the bis(aza-15-crown-5) chemosensor 48a the following binding

• alkyldiammonium ions in ethanol or in a chloroform/methanol mixture (9:1) based on the PET principle [191]. The fluorescence of the anthracene function is quenched by the free electron pairs of the nitrogen atoms. When hydrogen bonds are formed by both nitrogen atoms to the bis-ammonium guests, the photoinduced

Synthetic incorporation of Nile Blue into DNA using 2′-deoxyriboside substitutes: Representative comparison of (R)- and (S)-aminopropanediol as an acyclic linker

• Daniel Lachmann,
• Sina Berndl,
• Otto S. Wolfbeis and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2010, 6, No. 13, doi:10.3762/bjoc.6.13

• , DNA2C), or both (DNA2G). It becomes clear from a rough estimation of the excited state potential for the Nile Blue dye that guanine oxidation by an photoinduced electron transfer causes the fluorescence quenching. If the singlet–singlet transition energy E00 = 1.9 eV is added to the reduction potential

Synthesis of rigidified flavin–guanidinium ion conjugates and investigation of their photocatalytic properties

• Harald Schmaderer,
• Mouchumi Bhuyan and
• Burkhard König

Beilstein J. Org. Chem. 2009, 5, No. 26, doi:10.3762/bjoc.5.26

• and flavin should enhance the rate of photoinduced electron transfer processes, which strongly depend on distance [44]. We present here the synthesis of geometrically defined flavin-guanidinium ion conjugates based on a Kemp’s acid skeleton (Scheme 1). The guanidinium moiety should serve as a hydrogen

• photocatalytic activity of 1 and 2 was expected, as the binding site could keep reaction substrates in close proximity to the redox active chromophore, facilitating photoinduced electron transfer processes. Initial exemplary photocatalytic experiments showed that flavin-derivatives 1 and 2 catalyze oxidative

Synthesis and redox behavior of new ferrocene- π-extended- dithiafulvalenes: An approach for anticipated organic conductors

• Abdelwareth A. O. Sarhan,
• Omar F. Mohammed and
• Taeko Izumi

Beilstein J. Org. Chem. 2009, 5, No. 6, doi:10.3762/bjoc.5.6

• as excellent building blocks for intramolecular charge and photoinduced electron-transfer processes [4]; (iv) they can be oxidized successively and reversibly (multistage redox states) to the cation radical and dication species. Related to this issue, Hudhomme and co-workers have synthesized and