Visible light-mediated difluoroalkylation of electron-deficient alkenes

• Vyacheslav I. Supranovich,
• Vitalij V. Levin,
• Marina I. Struchkova,
• Jinbo Hu and
• Alexander D. Dilman

Beilstein J. Org. Chem. 2018, 14, 1637–1641, doi:10.3762/bjoc.14.139

• with blue light is described. The reaction involves radical addition of 1,1-difluorinated radicals at the double bond followed by hydrogen atom transfer from sodium cyanoborohydride. Keywords: difluoroalkylation; organofluorine compounds; radical addition; visible light; Introduction Applications of

• addition step cannot be oxidized by photocatalysts. Herein we report a convenient method for performing hydroperfluoroalkylation of electron-deficient alkenes employing iodides 1 mediated by visible light. The reaction proceeds without the use of a photosensitizer or a photocatalyst. Generation of

• hydrogen and as a trigger for the generation of free radicals mediated by visible light. Difluoroalkylation of alkenes. Isolated yields are shown. a2 equiv of the alkene were used. Fluoroalkylation of alkenes. Proposed mechanism. Optimization studies. Supporting Information Supporting Information File 220

Glycosylation reactions mediated by hypervalent iodine: application to the synthesis of nucleosides and carbohydrates

• Yuichi Yoshimura,
• Hideaki Wakamatsu,
• Yoshihiro Natori,
• Yukako Saito and
• Noriaki Minakawa

Beilstein J. Org. Chem. 2018, 14, 1595–1618, doi:10.3762/bjoc.14.137

• out by treatment with diacetoxyiodobenzene and iodine under irradiation with visible light to give acetoxy acetals 130 and 131 in good yields with high stereoselectivities. As shown in Scheme 17, the reaction was expected to proceed via the formation of anomeric alkoxyl radicals, which underwent

London dispersion as important factor for the stabilization of (Z)-azobenzenes in the presence of hydrogen bonding

• Andreas H. Heindl,
• Raffael C. Wende and
• Hermann A. Wegner

Beilstein J. Org. Chem. 2018, 14, 1238–1243, doi:10.3762/bjoc.14.106

• [12] and show reversible isomerization from the thermally stable E- to the Z-isomer upon irradiation with UV light. The metastable Z-azobenzene re-isomerizes to the E-conformer either thermally or upon irradiation with visible light [13][14]. Interestingly, the thermal stability of azobenzene isomers

Selective carboxylation of reactive benzylic C–H bonds by a hypervalent iodine(III)/inorganic bromide oxidation system

• Toshifumi Dohi,
• Shohei Ueda,
• Kosuke Iwasaki,
• Yusuke Tsunoda,
• Koji Morimoto and
• Yasuyuki Kita

Beilstein J. Org. Chem. 2018, 14, 1087–1094, doi:10.3762/bjoc.14.94

• initiated by the decomposition of PIFA to form the trifluoroacetoxy radical under visible light irradiation [50]. Our approach for the generation of radical species for the benzylic carboxylation using a hypervalent iodine reagent relies on the unique reactivity of the hypervalent iodine(III)–bromine bond

Hypervalent iodine(III)-mediated decarboxylative acetoxylation at tertiary and benzylic carbon centers

• Kensuke Kiyokawa,
• Daichi Okumatsu and
• Satoshi Minakata

Beilstein J. Org. Chem. 2018, 14, 1046–1050, doi:10.3762/bjoc.14.92

• (AcOI), which participates in the generation of RCO2I by reacting with a carboxylic acid 1. Meanwhile, RCO2I is directly generated along with AcOI when 4 reacts with I2. Subsequently, decarboxylative iodination of RCO2I under irradiation with visible light affords an alkyl iodide intermediate, which is

Hypervalent iodine-mediated Ritter-type amidation of terminal alkenes: The synthesis of isoxazoline and pyrazoline cores

• Sang Won Park,
• Soong-Hyun Kim,
• Jaeyoung Song,
• Ga Young Park,
• Darong Kim,
• Tae-Gyu Nam and
• Ki Bum Hong

Beilstein J. Org. Chem. 2018, 14, 1028–1033, doi:10.3762/bjoc.14.89

• , diverse halonium sources have been utilized for the synthesis of isoxazolines via halocyclization. Furthermore, transition metal-, visible light, and hypervalent iodine-mediated oxidative cyclization protocols provide isoxazoline backbones bearing diverse substituents such as –SR, -CF3, -OH and halogens

Functionalization of N-arylglycine esters: electrocatalytic access to C–C bonds mediated by n-Bu₄NI

• Mi-Hai Luo,
• Yang-Ye Jiang,
• Kun Xu,
• Yong-Guo Liu,
• Bao-Guo Sun and
• Cheng-Chu Zeng

Beilstein J. Org. Chem. 2018, 14, 499–505, doi:10.3762/bjoc.14.35

• ., wherein simple copper salts were used as catalysts and oxygen as the co-oxidant (Scheme 1) [17]. Alternatively, photocatalytic versions of CDC reactions of glycine derivatives with C-nucleophiles were also developed [18][19]. For example, combining the visible light catalyst Ru(bpy)3Cl2, and the

Diels–Alder cycloadditions of N-arylpyrroles via aryne intermediates using diaryliodonium salts

• Huangguan Chen,
• Jianwei Han and
• Limin Wang

Beilstein J. Org. Chem. 2018, 14, 354–363, doi:10.3762/bjoc.14.23

• coupling products were obtained in moderate to good yields (Scheme 1a) [6]. Later in 2013, Xue and Xiao et al. developed a method of photoredox catalysis in the presence of [Ru(bpy)3]2+ with visible light for the coupling reaction of arenes with unprotected or N-substituted pyrroles, pyrrole substrates

One-pot preparation of 4-aryl-3-bromocoumarins from 4-aryl-2-propynoic acids with diaryliodonium salts, TBAB, and Na₂S₂O₈

• Teppei Sasaki,
• Katsuhiko Moriyama and
• Hideo Togo

Beilstein J. Org. Chem. 2018, 14, 345–353, doi:10.3762/bjoc.14.22

• TBAB/K2S2O8 at 90 °C [31], the cyanomethyl-radical-mediated reaction of aryl 2-alkynoates with tert-butyl peroxybenzoate (TBPB)/acetonitrile at 130 °C [32], the sunlight-promoted reaction of aryl 2-alkynoates with N-iodosuccinimide (NIS) at rt [33], and the visible-light-mediated reaction of aryl 2

Progress in copper-catalyzed trifluoromethylation

• Guan-bao Li,
• Chao Zhang,
• Chun Song and
• Yu-dao Ma

Beilstein J. Org. Chem. 2018, 14, 155–181, doi:10.3762/bjoc.14.11

• relatively inexpensive CF3I. Besides, the easy conversion of CF3I to CF3 radical at room temperature with visible light developed by MacMillan facilitated these method [38][39]. On the basis of the former work, the group of Sanford [40] designed the cross-coupling of arylboronic acids with CF3I via the

• merger of photoredox and Cu catalysis (Scheme 21). In this protocol, the CF3 radical was generated by visible light photoredox, then Cu aryl species were generated through Cu catalysis. Aromatic boronic acids bearing either electron-donating or electron-withdrawing substituents underwent

Photocatalytic formation of carbon–sulfur bonds

• Alexander Wimmer and
• Burkhard König

Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4

• . General concepts, synthetic strategies and the substrate scope of reactions yielding thiols, disulfides, sulfoxides, sulfones and other organosulfur compounds are discussed together with the proposed mechanistic pathways. Keywords: disulfides; photocatalysis; sulfones; sulfoxides; thiols; visible light

• ; Introduction Visible-light photoredox catalysis has developed into an important tool for organic synthesis in the last two decades. Energy-efficient and cheap visible-light-emitting diodes are perfect light sources allowing chemists now to conduct photocatalyzed reactions without special or expensive equipment

• . Photoredox-active metal complexes or organic dyes are used to initiate photo-induced single-electron transfer (SET) processes upon excitation with visible-light. Such photooxidations or photoreductions yield reactive organic radicals, which can undergo unique bond forming reactions, under very mild

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation and chlorination. Part 2: Use of CF₃SO₂Cl

• Hélène Chachignon,
• Hélène Guyon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2800–2818, doi:10.3762/bjoc.13.273

• the presence of Eosin Y under visible light irradiation (Scheme 2) [9]. Acetophenone derivatives with various substitution patterns as well as aliphatic or heteroaromatic ketones were equally well tolerated. This methodology offered the advantage of minimising the chlorination side reaction

• interestingly, when the reaction was performed using an aryl or alkylsulfonyl chloride, instead of trifluoromethanesulfonyl chloride, no extrusion of the SO2 moiety was observed, and the sulfonated products were recovered. The reaction mechanism involved excitation of the iridium catalyst under visible light to

• visible light irradiation, a first SET reduction of CF3SO2Cl occurred, ultimately leading to the formation of the stabilised trifluoromethyl radical after releasing SO2 and chloride anion. This electron deficient radical was then added on the most electron-rich position of the arene substrate to yield

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation. Part 1: Use of CF₃SO₂Na

• Hélène Guyon,
• Hélène Chachignon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2764–2799, doi:10.3762/bjoc.13.272

• the presence of the organic photocatalyst N-methyl-9-mesitylacridinium (17), CF3SO2Na was converted into CF3• upon visible-light irradiation. The CF3• radical reacted with the vinyl azide to give the iminyl radical 18 that was reduced by Mes-Acr• (Mes-Acr: 9-mesityl-10-methylacridinium) into the

• electron oxidation of CF3SO2Na was performed by visible-light activated N-methyl-9-mesitylacridinium as a photoredox catalyst. Two hydrogen atom donors, 20 mol % of methyl thiosalicylate 38 for aliphatic alkenes (or 1 equiv of thiophenol 39 for styrenyl alkenes) and 2,2,2-trifluoroethanol (TFE), worked in

• authors also realised the same chemical transformation under visible light irradiation at 450 nm by means of the iridium photocatalyst Ir[dF(CF3)ppy]2(dtbbpy)PF6 ([4,4’-bis(tert-butyl)-2,2’-bipyridine]bis[3,5-difluoro-2-[5-(trifluoromethyl)-2-pyridinyl]phenyl]iridium(III) hexafluorophosphate), which

Mechanochemical synthesis of small organic molecules

• Tapas Kumar Achar,
• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2017, 13, 1907–1931, doi:10.3762/bjoc.13.186

• /energy, etc. Non-conventional energy sources for chemical reactions such as microwave, mechanical mixing, visible-light and ultrasound are becoming surge of interest to the chemist as alternative energy sources in laboratories [7]. By imposing these techniques innumerable chemical transformations have

Oxidative dehydrogenation of C–C and C–N bonds: A convenient approach to access diverse (dihydro)heteroaromatic compounds

• Santanu Hati,
• Ulrike Holzgrabe and
• Subhabrata Sen

Beilstein J. Org. Chem. 2017, 13, 1670–1692, doi:10.3762/bjoc.13.162

• the presence of visible light and catalytic MgI2 was described [89]. The reaction takes about 8–72 hours to complete depending on the substituents present in starting amines and aldehydes (Scheme 28). Initial condensation of 2-aminobenzylamine with an aldehyde generates 2-aryl-1,2,3,4

Synthesis and metal binding properties of N-alkylcarboxyspiropyrans

• Alexis Perry and
• Christina J. Kousseff

Beilstein J. Org. Chem. 2017, 13, 1542–1550, doi:10.3762/bjoc.13.154

• binding occurs as a result of stabilisation of the zwitterionic merocyanine isomer via phenoxide–metal complexation [17] (Figure 1). Commonly, merocyanines undergo photoreversion to their corresponding spiropyran under visible light irradiation and metal complexation is usually achieved either in darkness

Mechanochemical borylation of aryldiazonium salts; merging light and ball milling

• José G. Hernández

Beilstein J. Org. Chem. 2017, 13, 1463–1469, doi:10.3762/bjoc.13.144

• the original study, irradiation for 18 h of a MeCN solution of aryldiazonium salts, bis(pinacolato)diboron (B2pin2, 2) and eosin Y with a 25 W visible light lamp led to the corresponding arylboronates in moderate to good yields [18]. Results and Discussion To commence, a PMMA milling jar was designed

Detection of therapeutic radiation in three-dimensions

• John A. Adamovics

Beilstein J. Org. Chem. 2017, 13, 1325–1331, doi:10.3762/bjoc.13.129

• ferrous/agarose/xylenol orange (FAX) gel shows visible-light absorption at 440 nm; after exposure to ionizing radiation, there is an increase in absorption at 585 nm. Even though diffusion has been diminished it continues to be an issue [12]. These diffusion limitations were overcome in a gel matrix by

Kinetic analysis of mechanoradical formation during the mechanolysis of dextran and glycogen

• Naoki Doi,
• Yasushi Sasai,
• Yukinori Yamauchi,
• Tetsuo Adachi,
• Masayuki Kuzuya and
• Shin-ichi Kondo

Beilstein J. Org. Chem. 2017, 13, 1174–1183, doi:10.3762/bjoc.13.116

• TCNE under visible-light irradiation. We adopted this method by Sakaguchi et al for the detection of mechanoanions (see Experimental). Figure 5 shows the observed ESR spectrum before and after visible-light irradiation of the fractured sample of Dx and TCNE. As no ESR spectrum was observed after the

• mechanochemical reaction of pure TCNE, it was assumed that the ESR spectrum depicted in Figure 5a might be ascribed to the radical produced by the reaction of Dx mechanoradical and TCNE. As the characteristics of the spectrum and the intensity before and after visible-light irradiation remained unaffected, there

• several hours at room temperature in the intensity and shape within a detectable extent. Procedure to detect mechanoanions Dx was fractured in a metallic vessel at room temperature. The fractured Dx and TCNE were mixed in the dark to avoid the decomposition of mechanoanion and exposed to visible light to

Chemoselective synthesis of diaryl disulfides via a visible light-mediated coupling of arenediazonium tetrafluoroborates and CS₂

• Jing Leng,
• Shi-Meng Wang and
• Hua-Li Qin

Beilstein J. Org. Chem. 2017, 13, 903–909, doi:10.3762/bjoc.13.91

• visible light-promoted coupling of readily accessible arenediazonium tetrafluoroborates and CS2. This practical and convenient protocol provides a direct pathway for the assembly of a series of disulfides in an environmentally friendly manner with good to excellent yields. Keywords: arenediazonium

• transformation of carbon disulfide into diaryl disulfides [11]. Sunlight as abundant and almost infinitely available energy resource has been widely used for chemical transformations in the sense of cost, safety, availability, and environmental friendliness [12][13][14][15]. Herein, we report a visible light

• and to minimize the formation of the byproducts was conducted. As recently surveyed, photoredox catalysts are widely employed for the generation of radicals for diverse radical reactions [19]. Further, the application of aryl radicals generated from aryldiazonium salts under visible light irradiation

How and why kinetics, thermodynamics, and chemistry induce the logic of biological evolution

• Addy Pross and
• Robert Pascal

Beilstein J. Org. Chem. 2017, 13, 665–674, doi:10.3762/bjoc.13.66

• that of biochemical intermediates like ATP, requires a free energy potential exceeding a value of 150 kJ mol−1, equivalent to that of visible light [4][55][56]. Therefore, it turns out that considering the kinetic conditions for dynamic kinetic stability leads to the definition of conditions for the

• instructive to note that this assessment is compatible with visible light as an energy source as well as moderate temperatures, both of which could be found at the surface of the early Earth. However, these considerations by themselves do not solve the question of the origin of life, or at least the point of

• of these entities leads to a semiquantitative assessment of the environmental conditions required for a self-organisation process, one based on established organic chemical processes. It is intriguing to note that this assessment is compatible with visible light as an energy source, and a moderate

Novel β-cyclodextrin–eosin conjugates

• Gábor Benkovics,
• Damien Afonso,
• András Darcsi,
• Szabolcs Béni,
• Sabrina Conoci,
• Éva Fenyvesi,
• Lajos Szente,
• Milo Malanga and
• Salvatore Sortino

Beilstein J. Org. Chem. 2017, 13, 543–551, doi:10.3762/bjoc.13.52

• successfully utilized in photodynamic therapy (PDT). This minimally invasive therapeutic approach has proven to be very well-suited for cancer and bacterial diseases treatment. The PDT is based on the combination of three main components: visible light, a photosensitizer (PS) and molecular oxygen [4][5]. After

• being excited with visible light, the PS – while reverting to the ground state – transfers the energy of its lowest excited triplet state to nearby molecular oxygen. This leads to an in situ generation of singlet oxygen (1O2), which is the main responsible species for cytotoxic reactions in cells [6

• nitric oxide under illumination with visible light, resulting in amplified cancer-cell mortality [9]. By attaching porphyrin to γ-CD and dimeric β-CD, which are both able to form inclusion complexes with cytotoxic drug molecules such as doxorubicin and paclitaxel, nanocarriers with multimodal therapeutic

3D printed fluidics with embedded analytic functionality for automated reaction optimisation

• Andrew J. Capel,
• Andrew Wright,
• Matthew J. Harding,
• George W. Weaver,
• Yuqi Li,
• Russell A. Harris,
• Steve Edmondson,
• Ruth D. Goodridge and
• Steven D. R. Christie

Beilstein J. Org. Chem. 2017, 13, 111–119, doi:10.3762/bjoc.13.14

• ) being picked up by the detector when the light source was inactive (Figure 2). This demonstrated that due to the transparency of the Accura 60 resin to visible light, even though the part would be housed inside a dark chamber, ideally the detection wavelengths for this material should be kept below 400

Copper-catalyzed asymmetric sp³ C–H arylation of tetrahydroisoquinoline mediated by a visible light photoredox catalyst

• Pierre Querard,
• Inna Perepichka,
• Eli Zysman-Colman and
• Chao-Jun Li

Beilstein J. Org. Chem. 2016, 12, 2636–2643, doi:10.3762/bjoc.12.260

• catalysts provide a mild and highly effective sp3 C–H asymmetric arylation of THIQs. Keywords: C–H arylation; copper catalyst; enantioselectivity; visible light; Introduction Functionalization of sp3 C–H bonds is a unique and powerful transformation in modern organic synthesis, which remains a challenging

• [2]. The emerging and expanding field of visible-light-mediated photoredox catalysis presents unique opportunities for the conception of new synthetic routes [3][4][5][6][7][8][9][10][11][12]. Upon exposure to visible light, photoredox catalysts can function as both reductant and oxidant, thereby

• allow us to design a visible-light-mediated photoredox asymmetric arylation of tetrahydroisoquinolines (THIQs) [15][16][17][18][19][20]. During the last decade, numerous examples of sp3 C–H bond arylation procedures have been developed [1][21][22][23][24][25][26][27][28][29]. In 2008, our group

A self-assembled cyclodextrin nanocarrier for photoreactive squaraine

• Ulrike Kauscher and
• Bart Jan Ravoo

Beilstein J. Org. Chem. 2016, 12, 2535–2542, doi:10.3762/bjoc.12.248

• , which have the disadvantage of an absorption wavelength in the range of visible light [8][9]. Visible light is scattered and absorbed by the inhomogeneous biological tissue. In order to optimise efficiency, it is vital to skew the absorption range of the PS towards the near infrared range. Then, the