Extension of the 5-alkynyluridine side chain via C–C-bond formation in modified organometallic nucleosides using the Nicholas reaction

• Renata Kaczmarek,
• Dariusz Korczyński,
• James R. Green and
• Roman Dembinski

Beilstein J. Org. Chem. 2020, 16, 1–8, doi:10.3762/bjoc.16.1

• ]. In parallel, bioorganometallic chemistry provides new tools to influence biological interactions [16][17][18][19][20][21][22][23][24]. Cobalt possesses a diverse array of properties that can be manipulated to yield promising drug candidates [25]. The antiproliferative properties [26], as well as

• carbon monoxide-releasing properties [27][28] of dicobalt hexacarbonyl alkyne complexes have been noted, and their medicinal potential has been summarized [29][30][31]. Despite developments, the collection of metallo-nucleosides is limited. Hybridization of alkyl and aryl-substituted alkyne cobalt

• HeLa and K562 cell lines [31]. The formation of a reactive oxygen species in the presence of cobalt compounds was determined in K562 cells. The results indicate that the mechanism of action for most antiproliferative cobalt compounds may be related to the induction of oxidative stress [31

A review of asymmetric synthetic organic electrochemistry and electrocatalysis: concepts, applications, recent developments and future directions

• Munmun Ghosh,
• Valmik S. Shinde and
• Magnus Rueping

Beilstein J. Org. Chem. 2019, 15, 2710–2746, doi:10.3762/bjoc.15.264

• enzymes involve cobalt in the catalytically active center. In his article, Prof. Hisaeda reviewed vitamin B12-mediated electrochemical reactions in organic solvents in detail [83]. A number of pioneering results have been published in this area by leading electroorganic chemists [84][85][86]. In 1994 and

Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups

• Xiaowei Li,
• Xiaolin Shi,
• Xiangqian Li and
• Dayong Shi

Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218

• different catalysts, such as palladium, copper, silver, iron, nickel, ruthenium, cobalt, etc. Palladium catalysis Palladium is a member of the nickel triad in the periodic table, and palladium complexes exist in three oxidation states, Pd(0), Pd(II), and Pd(IV). Straightforward interconversion between

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

Synthesis of acylglycerol derivatives by mechanochemistry

• Karen J. Ardila-Fierro,
• Andrij Pich,
• Marc Spehr,
• José G. Hernández and
• Carsten Bolm

Beilstein J. Org. Chem. 2019, 15, 811–817, doi:10.3762/bjoc.15.78

• -opening reaction of 2 with stearic acid (3a) was evaluated (Scheme 3a). Specifically, we focused on the use of Jacobsen cobalt(II)-salen complex (S,S)-cat (Scheme 3b), since similar salen complexes had originally been reported to facilitate epoxide ring-opening reactions with carboxylic acids as

• a promising one to mechanochemically access MAGs by ball milling. Experimentally, we attempted the cobalt-catalyzed epoxide ring-opening reaction by milling 2 with stearic acid (3a) in the presence of (S,S)-cat (2.5 mol %) and N,N-diisopropylethylamine (DIPEA; 1.0 equiv, Scheme 3a). Mechanistically

• ). However, purification of 4a by column chromatography on SiO2 favored acyl migration in 4a, thereby dropping the yield of 4a by increasing the amount of the isomeric sn-2,3-protected monoacylglycerol 4a’ (Figure 2) [42]. Typically, cobalt complex (S,S)-cat has been used for kinetic resolution of racemic

Design, synthesis and spectroscopic properties of crown ether-capped dibenzotetraaza[14]annulenes

• Krzysztof M. Zwoliński and
• Julita Eilmes

Beilstein J. Org. Chem. 2019, 15, 617–622, doi:10.3762/bjoc.15.57

• ], little research has been undertaken regarding DBTAAs functionalized with crown ether moieties (see Figure 1). Kruse and Breitmaier [24] reported annulated DBTAA‘s containing benzo-15-crown-5 scaffolds fused with benzenoid rings of the macrocyclic core. Both nickel(II) and cobalt(II) complexes were

• presence of alkali metal and ammonium ions. Sakata et al. reported the synthesis of peripherally functionalized DBTAAs with the two benzo-15-crown-5 scaffolds appended to the meso-benzoyl substituents [27]. Both crown ether-capped macrocycles in a form of free base and nickel(II) and cobalt(II) complexes

Selective benzylic C–H monooxygenation mediated by iodine oxides

• Kelsey B. LaMartina,
• Haley K. Kuck,
• Linda S. Oglesbee,
• Asma Al-Odaini and
• Nicholas C. Boaz

Beilstein J. Org. Chem. 2019, 15, 602–609, doi:10.3762/bjoc.15.55

• by Ishii and co-workers on the aerobic oxidation of cumene in acetic acid using catalytic NHPI and cobalt(II), resulted in a mixture of 2-phenyl-2-propanol, acetophenone, and phenol [60][61]. This lack of selectivity in the product was related in part to the propensity of the cumene hydroperoxide

Syntheses and chemical properties of β-nicotinamide riboside and its analogues and derivatives

• Mikhail V. Makarov and
• Marie E. Migaud

Beilstein J. Org. Chem. 2019, 15, 401–430, doi:10.3762/bjoc.15.36

• hexachloroacetone [28][71] or cobalt(II) acetate in the presence of hydrogen peroxide followed by removal of the cobalt cations with QuadraSil AP resin [60]. The nature of the counter anion vary as a function of the conditions applied. Reduction of N1-substituted 3-nicotinamide salts to the corresponding 1,4

• cobalt acetate in the presence of hydrogen peroxide. This approach required the subsequent removal of metal ions by Quadrasil resin. The oxidized acetonides 45 were subsequently deprotected using

Repurposing the anticancer drug cisplatin with the aim of developing novel Pseudomonas aeruginosa infection control agents

• Mingjun Yuan,
• Song Lin Chua,
• Yang Liu,
• Daniela I. Drautz-Moses,
• Joey Kuok Hoong Yam,
• Thet Tun Aung,
• Roger W. Beuerman,
• May Margarette Santillan Salido,
• Stephan C. Schuster,
• Choon-Hong Tan,
• Michael Givskov,
• Liang Yang and
• Thomas E. Nielsen

Beilstein J. Org. Chem. 2018, 14, 3059–3069, doi:10.3762/bjoc.14.284

• respective drug 3 times per day. Cornea wound was visualized by the aid of cobalt-blue filter equipped slit lamp biomicroscopy (New-generation Zoom clinical Slit Lamp, NS-2D, Righton), staining with Minims fluorescein sodium eye drops (Bausch and Lomb, 2% w/v) which is used in ophthalmology clinic for

Olefin metathesis catalysts embedded in β-barrel proteins: creating artificial metalloproteins for olefin metathesis

• Daniel F. Sauer,
• Johannes Schiffels,
• Takashi Hayashi,
• Ulrich Schwaneberg and
• Jun Okuda

Beilstein J. Org. Chem. 2018, 14, 2861–2871, doi:10.3762/bjoc.14.265

• catalyst or redox catalyst. Various metalloenzymes have been applied in laboratory-scale reactions and a few metalloenzymes such as nitrile hydratase (cobalt(III) in the active site) for the production of acrylamide have found application in industry [25]. Notably, however, the reaction scope of natural

Copolymerization of epoxides with cyclic anhydrides catalyzed by dinuclear cobalt complexes

• Yo Hiranoi and
• Koji Nakano

Beilstein J. Org. Chem. 2018, 14, 2779–2788, doi:10.3762/bjoc.14.255

• synthetic method for polyesters as the polymers’ architectures and properties can be easily controlled depending on the combination of two monomers. Thus, a variety of catalyst designs has been reported to prepare the desired copolymers efficiently. We herein report dinuclear cobalt–salen complexes with a

• benzene ring as a linker and their activities in copolymerization reactions. The dinuclear cobalt complexes showed a higher catalytic activity for the copolymerization of propylene oxide with phthalic anhydride than the corresponding mononuclear cobalt–salen complex and achieved one of the highest

• turnover frequencies ever reported. A variety of epoxides and CAs were also found to be copolymerized successfully by the dinuclear cobalt complex with a high catalytic activity. Keywords: cobalt; copolymerization; cyclic anhydrides; epoxides; polyesters; Introduction Aliphatic polyesters have received

Learning from B₁₂ enzymes: biomimetic and bioinspired catalysts for eco-friendly organic synthesis

• Keishiro Tahara,
• Ling Pan,
• Toshikazu Ono and
• Yoshio Hisaeda

Beilstein J. Org. Chem. 2018, 14, 2553–2567, doi:10.3762/bjoc.14.232

• Cobalamins (B12) are naturally occurring cobalt complexes with unique structures that play various important roles in vivo [1][2][3][4][5]. In B12, the cobalt center is coordinated by four equatorial pyrroles of the corrin ring and 2,3-dimethylbenzimidazole as a lower axial ligand (Figure 1a) [6][7][8]. The

• cobalamin with an upper ligand is termed vitamin B12 (a cyanide group), methylcobalamin (a methyl group), and adenosylcobalamin (an adenosyl group), respectively. The oxidation state of cobalt ions in B12 ranges from +1 to +3. Each oxidation state of cobalamins exhibits quite different ligand-accepting

• ligands of cobalt complexes 2 are superior to porphyrin ligands in terms of the model for the corrin framework of B12; both the imine/oxime-type and corrin ligands are monoanionic [57][58][59][60]. The imine/oxime-type cobalt complex 2 can be isolated in both the monoalkylated and dialkylated forms [59

Synthesis of aryl sulfides via radical–radical cross coupling of electron-rich arenes using visible light photoredox catalysis

• Amrita Das,
• Mitasree Maity,
• Simon Malcherek,
• Burkhard König and
• Julia Rehbein

Beilstein J. Org. Chem. 2018, 14, 2520–2528, doi:10.3762/bjoc.14.228

• triflates [8], and diazonium salts [9]. Typical metals used are palladium [10][11][12][13], copper [14][15][16][17][18][19][20][21], nickel [22][23][24], iron [25][26][27][28][29], cobalt [30][31][32], and rhodium [33][34]. Aryl sulfides are also synthesized by cross coupling of thiols and aryl Grignard

Cobalt- and rhodium-catalyzed carboxylation using carbon dioxide as the C1 source

• Tetsuaki Fujihara and
• Yasushi Tsuji

Beilstein J. Org. Chem. 2018, 14, 2435–2460, doi:10.3762/bjoc.14.221

• review, the Co- and Rh-catalyzed transformation of CO2 via carbon–carbon bond-forming reactions is summarized. Combinations of metals (cobalt or rhodium), substrates, and reducing agents realize efficient carboxylation reactions using CO2. The carboxylation of propargyl acetates and alkenyl triflates

• using cobalt complexes as well as the cobalt-catalyzed reductive carboxylation of α,β-unsaturated nitriles and carboxyamides in the presence of Et2Zn proceed. A Co complex has been demonstrated to act as an efficient catalyst in the carboxylation of allylic C(sp3)–H bonds. Employing zinc as the

• [2 + 2 + 2] cycloaddition of diynes and CO2 proceeds to afford pyrones. Keywords: carbon dioxide; carboxylation; cobalt; homogeneous catalysts; rhodium; Introduction Carbon dioxide (CO2) is one of the most important materials as renewable feedstock [1][2][3][4]. However, the thermodynamic and

A challenging redox neutral Cp*Co(III)-catalysed alkylation of acetanilides with 3-buten-2-one: synthesis and key insights into the mechanism through DFT calculations

• Andrew Kenny,
• Alba Pisarello,
• Arron Bird,
• Paula G. Chirila,
• Alex Hamilton and
• Christopher J. Whiteoak

Beilstein J. Org. Chem. 2018, 14, 2366–2374, doi:10.3762/bjoc.14.212

• not the C–H activation step, but instead and unexpectedly, effective competition with more stable compounds (resting states) not involved in the catalytic cycle. Keywords: acetanilides; alkylation; C–H activation; cobalt catalysis; DFT studies; Introduction Controlled functionalisation of ubiquitous

• application of these first-row transition metals stems from their low cost, ready availability and often wider reactivity profiles. One particular example which is currently attracting significant interest is cobalt, a metal which has found many applications in C–H functionalisation through exploitation of

• its diverse mechanisms [7]. Since 2013, the cobalt pre-catalysts, [Cp*Co(C6H6)](PF6)2 and [Cp*Co(CO)I2], have been successfully applied in a number of diverse C–H functionalisation protocols [8][9][10][11][12]. Whilst many of these protocols are very elegant, few examples are able to be applied to the

Bioinspired cobalt cubanes with tunable redox potentials for photocatalytic water oxidation and CO₂ reduction

• Zhishan Luo,
• Yidong Hou,
• Jinshui Zhang,
• Sibo Wang and
• Xinchen Wang

Beilstein J. Org. Chem. 2018, 14, 2331–2339, doi:10.3762/bjoc.14.208

• reactions. Keywords: CO2 reduction; cobalt cubane; photocatalysis; water oxidation; water splitting; Introduction The direct conversion of solar energy into chemical fuels (e.g., H2, CO and hydrocarbons) through water splitting and carbon fixation reactions is a sustainable solution to environmental

• Mn4CaO5 cubane of oxygen-evolving complex in photosystem II, there is an emerging number of molecular cubanes with metallic and heterobimetallic cores that are designed and synthesized for photosynthesis and electrochemistry. Cobalt-based molecular catalysts [44], in particular the ones containing a

• oxidation over 1-R is much higher than that over Co2+ ions, which may be due to the effect of the ligand for enhancing the stability of the entire cobalt metal center [48][49]. Furthermore, a long time course of water oxidation for 1-CN and Co2+ are also compared in Figure 6. It is obvious that the overall

Hydroarylations by cobalt-catalyzed C–H activation

• Rajagopal Santhoshkumar and
• Chien-Hong Cheng

Beilstein J. Org. Chem. 2018, 14, 2266–2288, doi:10.3762/bjoc.14.202

• Rajagopal Santhoshkumar Chien-Hong Cheng Department of Chemistry, National Tsing Hua University, Taiwan 10.3762/bjoc.14.202 Abstract As an earth-abundant first-row transition metal, cobalt catalysts offer a broad range of economical methods for organic transformations via C–H activation. One of

• the transformations is the addition of C–H to C–X multiple bonds to afford alkylation, alkenation, amidation, and cyclization products using low- or high-valent cobalt catalysts. This hydroarylation is an efficient approach to build new C–C bonds in a 100% atom-economical manner. In this review, the

• recent developments of Co-catalyzed hydroarylation reactions and their mechanistic studies are summarized. Keywords: catalysis; C−C formation; C–H activation; cobalt; hydroarylation; Introduction For the last three decades, atom-economical synthetic approaches have played a substantial role in organic

Cobalt bis(acetylacetonate)–tert-butyl hydroperoxide–triethylsilane: a general reagent combination for the Markovnikov-selective hydrofunctionalization of alkenes by hydrogen atom transfer

• Xiaoshen Ma and
• Seth B. Herzon

Beilstein J. Org. Chem. 2018, 14, 2259–2265, doi:10.3762/bjoc.14.201

• Xiaoshen Ma Seth B. Herzon Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States Department of Pharmacology, Yale School of Medicine, New Haven, Connecticut 06520, United States 10.3762/bjoc.14.201 Abstract We show that cobalt bis(acetylacetonate) [Co(acac)2], tert

• -butyl hydroperoxide (TBHP), and triethylsilane (Et3SiH) constitute an inexpensive, general, and practical reagent combination to initiate a broad range of Markovnikov-selective alkene hydrofunctionalization reactions. These transformations are believed to proceed by cobalt-mediated hydrogen atom

• corresponding metal alkyl complex. This radical then undergoes addition to a second reagent (SOMOphile) to form the functionalized product (Scheme 1). A wide range of manganese, cobalt, or iron-based complexes containing diverse supporting ligands have found use in these reactions. To the best of our knowledge

Cobalt-catalyzed peri-selective alkoxylation of 1-naphthylamine derivatives

• Jiao-Na Han,
• Cong Du,
• Xinju Zhu,
• Zheng-Long Wang,
• Yue Zhu,
• Zhao-Yang Chu,
• Jun-Long Niu and
• Mao-Ping Song

Beilstein J. Org. Chem. 2018, 14, 2090–2097, doi:10.3762/bjoc.14.183

• Jiao-Na Han Cong Du Xinju Zhu Zheng-Long Wang Yue Zhu Zhao-Yang Chu Jun-Long Niu Mao-Ping Song College of Chemistry and Molecular Engineering, Zhengzhou University, Zhengzhou 450001, People’s Republic of China 10.3762/bjoc.14.183 Abstract A cobalt-catalyzed C(sp2)–H alkoxylation of 1

• system. Moreover, a series of biologically relevant fluorine-aryl ethers were easily obtained under mild reaction conditions after the removal of the directing group. Keywords: alkoxylation; C–H activation; cobalt catalysis; 1-naphthylamines; secondary alcohols; Introduction Aryl ethers are common

• systems. Recently, the inexpensive cobalt catalysts have received significant attention because of their unique and versatile activities in the C–H functionalizations [43][44][45][46][47][48][49][50][51]. In 2015, the cobalt-catalyzed alkoxylation of aromatic (and olefinic) carboxamides with primary

Cobalt-catalyzed nucleophilic addition of the allylic C(sp³)–H bond of simple alkenes to ketones

• Tsuyoshi Mita,
• Masashi Uchiyama,
• Kenichi Michigami and
• Yoshihiro Sato

Beilstein J. Org. Chem. 2018, 14, 2012–2017, doi:10.3762/bjoc.14.176

• Tsuyoshi Mita Masashi Uchiyama Kenichi Michigami Yoshihiro Sato Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan 10.3762/bjoc.14.176 Abstract We herein describe a cobalt/Xantphos-catalyzed regioselective addition of simple alkenes to acetophenone derivatives

• bonds; cobalt; ketones; Introduction The cleavage of C–H bonds of unreactive hydrocarbon followed by functionalization should be an ideal method for constructing complex molecules without introduction of reactive functionality in advance [1][2][3][4][5][6][7][8][9]. Since terminal alkenes including α

• tautomerized to η1-allylcobalt(III) III by the assistance of the oxygen atom in the Xantphos ligand [30]. When using α-olefin as a substrate, the cobalt atom should be located at the terminal position due to the avoidance of steric repulsion between the bulky Xantphos ligand and an alkyl substitution (similar

Cationic cobalt-catalyzed [1,3]-rearrangement of N-alkoxycarbonyloxyanilines

• Itaru Nakamura,
• Mao Owada,
• Takeru Jo and
• Masahiro Terada

Beilstein J. Org. Chem. 2018, 14, 1972–1979, doi:10.3762/bjoc.14.172

• , Aoba-ku, Sendai 980-8578 Japan 10.3762/bjoc.14.172 Abstract A cationic cobalt catalyst efficiently promoted the reaction of N-alkoxycarbonyloxyanilines at 30 °C, affording the corresponding ortho-aminophenols in good to high yields. As reported previously, our mechanistic studies including oxygen-18

• labelling experiments indicate that the rearrangement of the alkoxycarbonyloxy group proceeds in [1,3]-manner. In this article, we discuss the overall picture of the cobalt-catalysed [1,3]-rearrangement reaction including details of the reaction conditions and substrate scope. Keywords: anilines; cobalt

• reaction conditions with high functional group tolerance. Based on this concept, we disclosed that cationic cobalt catalysts efficiently promote the reaction of O-alkoxylcarbonyl-N-arylhydroxylamines 1 at 30 °C, affording the corresponding 2-aminophenol derivatives 2 in good to high yields [13]. Our

Graphitic carbon nitride prepared from urea as a photocatalyst for visible-light carbon dioxide reduction with the aid of a mononuclear ruthenium(II) complex

• Kazuhiko Maeda,
• Daehyeon An,
• Ryo Kuriki,
• Daling Lu and
• Osamu Ishitani

Beilstein J. Org. Chem. 2018, 14, 1806–1812, doi:10.3762/bjoc.14.153

• using cobalt-based metal complexes as reduction cocatalysts [17][18][19][20]. In these systems, structural properties of g-C3N4 such as specific surface area and porosity have a strong impact on activity, because they strongly affect the efficiency of electron/hole utilization to the surface chemical

β-Hydroxy sulfides and their syntheses

• Mokgethwa B. Marakalala,
• Edwin M. Mmutlane and
• Henok H. Kinfe

Beilstein J. Org. Chem. 2018, 14, 1668–1692, doi:10.3762/bjoc.14.143

• , alcohols, thiols, and azides as the nucleophiles [53]. The Eu3+ and Tb3+ versions were prepared by metal exchange in methanol, between the cobalt complex 67 and the triflate salts of the rare earths, giving the desired complexes CP1 and CP2 in 83% and 86% yield, respectively. The solvent free thiolysis of

Thiocarbonyl-enabled ferrocene C–H nitrogenation by cobalt(III) catalysis: thermal and mechanochemical

• Santhivardhana Reddy Yetra,
• Zhigao Shen,
• Hui Wang and
• Lutz Ackermann

Beilstein J. Org. Chem. 2018, 14, 1546–1553, doi:10.3762/bjoc.14.131

• by weakly-coordinating thiocarbonyl-assisted cobalt catalysis. Thus, carboxylates enabled ferrocene C–H nitrogenations with dioxazolones, featuring ample substrate scope and robust functional group tolerance. Mechanistic studies provided strong support for a facile organometallic C–H activation

• manifold. Keywords: amidation; C–H activation; cobalt; ferrocene; mechanochemistry; Introduction C–H activation has surfaced as a transformative tool in molecular sciences [1][2][3][4][5][6][7][8][9]. While major advances have been accomplished with precious 4d transition metals, recent focus has shifted

• towards more sustainable base metals [10][11][12][13][14][15][16][17], with considerable progress by earth-abundant cobalt catalysts [18][19][20][21][22]. In this context, well-defined cyclopentadienyl-derived cobalt(III) complexes have proven instrumental for enabling a wealth of C–H transformations [23

Cobalt-catalyzed C–H cyanations: Insights into the reaction mechanism and the role of London dispersion

• Eric Detmar,
• Valentin Müller,
• Daniel Zell,
• Lutz Ackermann and
• Martin Breugst

Beilstein J. Org. Chem. 2018, 14, 1537–1545, doi:10.3762/bjoc.14.130

• Abstract Carboxylate-assisted cobalt(III)-catalyzed C–H cyanations are highly efficient processes for the synthesis of (hetero)aromatic nitriles. We have now analyzed the cyanation of differently substituted 2-phenylpyridines in detail computationally by density functional theory and also experimentally

• -phenylpyridine furthermore highlight that London dispersion is an important factor that enables this challenging C–H transformation. Nonbonding interactions between the Cp* ligand and aromatic and C–H-rich fragments of other ligands at the cobalt center significantly contribute to a stabilization of cobalt

• , the strategic application of London dispersion in catalysis is still very difficult to achieve and, as a consequence, detailed insights in how dispersion influences organic reactions continue to be in high demand. Therefore, we have computationally analyzed the recently developed cobalt-catalyzed C–H