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

• are rare. In this work an environmentally benign protocol for the activation of carbon–oxygen single bonds of alcohols towards a reductive bond cleavage under visible light photocatalysis was developed. Alcohols were activated as 3,5-bis(trifluoromethyl)-substituted benzoates and irradiation with blue

• achieved under visible light photocatalysis and the auxiliary activation group can be readily recovered and reused. This method, ultimately requiring only energy and a tertiary amine as stoichiometric reductant, gives high yields after short illumination times under mild conditions for the deoxygenation of

• microreactor (see Supporting Information File 1). Conclusion In summary a protocol for the deoxygenation of benzylic alcohols, α-hydroxycarbonyl and α-cyanohydrin compounds under visible light photocatalysis was developed using 3,5-bis(trifluoromethyl)benzoic anhydride for alcohol activation. Since 3,5-bis

Homogeneous and heterogeneous photoredox-catalyzed hydroxymethylation of ketones and keto esters: catalyst screening, chemoselectivity and dilution effects

• Axel G. Griesbeck and
• Melissa Reckenthäler

Beilstein J. Org. Chem. 2014, 10, 1143–1150, doi:10.3762/bjoc.10.114

• ; photocatalysis; photoredox catalysis; redox; semiconductor; Introduction Stimulated by the principles of sustainable chemical synthesis and the progress in our understanding of catalytic and photoinduced electron-transfer processes, in recent years photoredox catalysis emerged as a new and powerful area for

• semiconductor particles that absorb in the UV-A and near visible reagion. The widely used TiO2 has found numerous applications in photochemical water detoxification or surface purification because of its favourable excited-state redox properties [11]. In synthetic applications of semiconductor photocatalysis

• the semiconductor valence band hole, the other from the substrate radical anion that is formed from reduction by the semiconductor conduction band electron. Mostly, one of these steps consumes a sacrificial electron/hole donor. In type B photocatalysis, combination of the radical ions leads to a new

Organic synthesis using photoredox catalysis

• Axel G. Griesbeck

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

• photocatalysis in general) is a young research field with regard to synthetic applications. The collection of papers in this Thematic Series on organic synthesis using photoredox catalysis shows this convincingly. It was a great pleasure to act as the editor of this Thematic Series on photochemical reactions

On the mechanism of photocatalytic reactions with eosin Y

• Michal Majek,
• Fabiana Filace and
• Axel Jacobi von Wangelin

Beilstein J. Org. Chem. 2014, 10, 981–989, doi:10.3762/bjoc.10.97

• discussed on the basis of pH, solvent polarity, lamp type, absorption properties, and quantum yields. Determination of the latter proved to be an especially valuable tool for the distinction between radical chain and photocatalytic reactions. Keywords: mechanism; organocatalysis; photocatalysis; photoredox

• differentiate between radical chain and photocatalysis mechanisms by monitoring the reaction progress after the light sources have been switched off [20]. Clearly, such experiments neglect the existence of short radical chains and thus provide no conclusive evidence of the mechanism. In general, the

• -mediated photocatalysis For better comparison, we have employed identical reagent concentrations and reaction conditions (solvents) as reported in the original papers [15][16][17][18][19][20][21]. Dry DMSO was mostly used as solvent, with the exception of the phenanthrene [19] and arylboron pinacolate [21

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

• transfer; kinetic; photocatalysis; photochemistry; photocyclic initiating system; photopolymerization; photoredox catalysis; radical generator; Introduction Among the possible usage of light, the conversion of photons into chemical energy, as stored into radicals or ions, is of great interest. As a part

Recent applications of the divinylcyclopropane–cycloheptadiene rearrangement in organic synthesis

• Sebastian Krüger and
• Tanja Gaich

Beilstein J. Org. Chem. 2014, 10, 163–193, doi:10.3762/bjoc.10.14

• organoiron route towards the guianolide skeleton. Stoltz’s tandem Wolff/DVCPR rearrangement. Stephenson’s tandem photocatalysis/arylvinylcyclopropane rearrangement. Padwa’s rhodium cascade involving a DVCPR. Matsubara’s version of a DVCPR. Toste’s tandem gold-catalyzed Claisen-rearrangement/DVCPR. Ruthenium

The chemistry of amine radical cations produced by visible light photoredox catalysis

• Jie Hu,
• Jiang Wang,
• Theresa H. Nguyen and
• Nan Zheng

Beilstein J. Org. Chem. 2013, 9, 1977–2001, doi:10.3762/bjoc.9.234

• are emerging as a powerful tool in amine synthesis. This article reviews synthetic applications of amine radical cations produced by visible light photocatalysis. Keywords: α-amino radical; amine radical cation; catalysis; distonic ion; free radical; iminium ion; photoredox; visible light

• light-mediated reactions. The synergistic effect between carbocatalysis and visible light-mediated photocatalysis has the potential to be further explored in other photocatalyzed reactions. Since visible light photocatalysis is often orthogonal to or compatible with a number of common catalytic

• processes, merging it with another type of catalysis has become a recent development in the field of visible light photocatalysis. One direct benefit of this dual catalysis approach is to allow expansion of the types of nucleophiles capable of adding to the iminium ions generated under photoredox conditions

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

• be made. Keywords: cycloaddition; flow chemistry; photocatalysis; photochemistry; photooxygenation; Introduction The use of ultraviolet light to carry out bond-forming reactions in synthetic organic chemistry has a long history dating back to the mid-19th century. The observation by Trommsdorff [1

• ]. Photocatalysis can also be performed by using visible light. This has been applied to the hydrodehalogenation of α-haloketones by using the dye Eosin Y (36) as a photocatalyst, and both DIPEA and Hantzsch ester 35 as electron donors (Scheme 13). The reaction was shown to be high yielding for a number of

• also be performed with visible-light photocatalysis, in this case with either ruthenium or iridium catalysts (Scheme 14). Again, residence times in the 100 µL microreactor were significantly shorter than those for the batch reactor, and in this case the microflow system also allowed reactions that were

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

• activity was investigated in benzyl ester cleavage, nitroarene reduction and a Diels–Alder reaction. The modified flavins photocatalyze the reactions, but the introduced substrate binding site does not enhance their performance. Keywords: flavin; guanidine; Kemp’s acid; photocatalysis; template