Electrocarboxylation: towards sustainable and efficient synthesis of valuable carboxylic acids

• Roman Matthessen,
• Jan Fransaer,
• Koen Binnemans and
• Dirk E. De Vos

Beilstein J. Org. Chem. 2014, 10, 2484–2500, doi:10.3762/bjoc.10.260

• cobalt complexes [133][134][135][136][137]. Similar to what was mentioned above for aromatic ketones, benzylic chlorides can also be converted to 2-arylpropionic acids (Scheme 18), with applications in the pharmaceutical industry, mainly as NSAIDs. Here too, some articles described the use of ionic

Phosphinocyclodextrins as confining units for catalytic metal centres. Applications to carbon–carbon bond forming reactions

• Matthieu Jouffroy,
• Rafael Gramage-Doria,
• David Sémeril,
• Dominique Armspach,
• Dominique Matt,
• Werner Oberhauser and
• Loïc Toupet

Beilstein J. Org. Chem. 2014, 10, 2388–2405, doi:10.3762/bjoc.10.249

• differs from that of the only other reported trans-[RhH(CO)3L] complex (where L is a bulky phosphoramidite), the observed three carbonyl bands (2055 (sh), 2022 (w) and 1998 (s) cm−1) being here spread over a larger frequency range [31]. Note that the related cobalt complex trans-[CoH(CO)3(PCy3)] displays

Building complex carbon skeletons with ethynyl[2.2]paracyclophanes

• Ina Dix,
• Lidija Bondarenko,
• Peter G. Jones,
• Thomas Oeser and
• Henning Hopf

Beilstein J. Org. Chem. 2014, 10, 2013–2020, doi:10.3762/bjoc.10.209

• triple bonds under the influence of a cobalt catalyst such as CpCo(CO)2 has been observed many times, notably by the Vollhardt group [12]. In our case, however, the process is not complete. Rather than yielding the expected biphenylenophane 27, the reaction stops at the stage of the cyclobutadiene

• last step is prohibitive. Instead it prefers the isomerization to the isolated CpCo-complex 26. Compound 26 was identified by its spectroscopic data (see Supporting Information File 1) and also by a single-crystal X-ray analysis. The result is displayed in Figure 6. The cobalt complex 26 shows

Copolymerization and terpolymerization of carbon dioxide/propylene oxide/phthalic anhydride using a (salen)Co(III) complex tethering four quaternary ammonium salts

• Jong Yeob Jeon,
• Seong Chan Eo,
• Jobi Kodiyan Varghese and
• Bun Yeoul Lee

Beilstein J. Org. Chem. 2014, 10, 1787–1795, doi:10.3762/bjoc.10.187

• -transition temperature (48 °C) than the CO2/PO alternating copolymer (40 °C). Keywords: carbon dioxide; CO2 chemistry; cobalt complex; phthalic anhydride; propylene oxide; terpolymerization; Introduction Carbon dioxide (CO2) can be utilized to prepare aliphatic polycarbonates through coupling reactions

An experimental and theoretical NMR study of NH-benzimidazoles in solution and in the solid state: proton transfer and tautomerism

• Carla I. Nieto,
• Pilar Cabildo,
• M. Ángeles García,
• Rosa M. Claramunt,
• Ibon Alkorta and
• José Elguero

Beilstein J. Org. Chem. 2014, 10, 1620–1629, doi:10.3762/bjoc.10.168

• relevant drugs (fungicides, anthelmintics, antiulcerative, antiviral,…) [2][3] are also part of some natural products (the most prominent benzimidazole compound in nature is N-ribosyl-5,6-dimethylbenzimidazole, which serves as an axial ligand for cobalt in vitamin B12) and have interesting ferroelectric

Synthesis of chiral N-phosphoryl aziridines through enantioselective aziridination of alkenes with phosphoryl azide via Co(II)-based metalloradical catalysis

• Jingran Tao,
• Li-Mei Jin and
• X. Peter Zhang

Beilstein J. Org. Chem. 2014, 10, 1282–1289, doi:10.3762/bjoc.10.129

• ; cobalt complex; metalloradical catalysis; organophosphorus; phosphoryl azide; Introduction Aziridines, the smallest three-membered nitrogen-containing heterocycles, are highly valuable heterocyclic compounds that are widely used in organic synthesis and pharmaceuticals [1][2]. As a result, tremendous

• environments toward the cobalt metalloradical center, but also function as potential donors to engage in hydrogen bonding with acceptors located at the nitrene moiety in the Co(III)–nitrene radical intermediate [18][35][36]. These secondary hydrogen bonding interactions are expected to lower the energy barrier

• the porphyrin ring are also omitted in (B). Structures of D2-symmetric chiral cobalt(II) porphyrins. [Co(TPP)]-catalyzed olefin aziridination with DPPA. [Co(P1)]-catalyzed asymmetric olefin aziridination with DPPA. Optimization of catalytic aziridination of styrene with phosphoryl azides by Co(II

Preparation of phosphines through C–P bond formation

• Iris Wauters,
• Wouter Debrouwer and
• Christian V. Stevens

Beilstein J. Org. Chem. 2014, 10, 1064–1096, doi:10.3762/bjoc.10.106

• catalysis (Table 16) [244]. Besides copper(I) iodide several other copper salts effectuated the reaction albeit in lower yields as did silver(I) iodide, palladium(II) chloride and platinum(II) chloride. Other transition metal catalysts such as gold(I) chloride, nickel(II) chloride and cobalt(II) chloride

A new manganese-mediated, cobalt-catalyzed three-component synthesis of (diarylmethyl)sulfonamides

• Antoine Pignon,
• Erwan Le Gall and
• Thierry Martens

Beilstein J. Org. Chem. 2014, 10, 425–431, doi:10.3762/bjoc.10.39

• related compounds by a new manganese-mediated, cobalt-catalyzed three-component reaction between sulfonamides, carbonyl compounds and organic bromides is described. This organometallic Mannich-like process allows the formation of the coupling products within minutes at room temperature. A possible

• mechanism, emphasizing the crucial role of manganese is proposed. Keywords: carbonyl compounds; cobalt; manganese; multicomponent reaction; organic bromides; sulfonamides; Introduction (Diarylmethyl)amines constitute an important class of pharmacologically active compounds, displaying e.g. antihistaminic

• and versatility of multicomponent procedures, we describe herein a new manganese-mediated, cobalt-catalyzed three-component reaction, which circumvents the above-mentioned limitations by allowing the synthesis of an extended range of (diarylmethyl)sulfonamides (and related compounds) within minutes at

Boron-substituted 1,3-dienes and heterodienes as key elements in multicomponent processes

• Ludovic Eberlin,
• Fabien Tripoteau,
• François Carreaux,
• Andrew Whiting and
• Bertrand Carboni

Beilstein J. Org. Chem. 2014, 10, 237–250, doi:10.3762/bjoc.10.19

• was produced from 5. If the [4 + 2]-cycloadduct 9 was obtained with N-phenylmaleimide, it failed to give homoallylic alcohols, probably due to steric hindrance [42]. An elegant three-component process was developed by Hilt and co-workers using a cobalt-catalyzed Diels–Alder reaction as the key step in

• -phenylmaleimide and 4-phenyltriazoline-3,5-dione. Asymmetric synthesis of a α-hydroxyalkylcyclohexane. Tandem [4 + 2]-cycloaddition/allylboration of 3-silyloxy- and 4-alkoxy-dienyl boronates. Metal-mediated cycloisomerization/Diels–Alder reaction/allylboration sequence. Cobalt-catalyzed Diels–Alder/allylboration

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

• the Co(II)/Et3SiH/O2 system (Isayama–Mukaiyama reaction) Peroxysilylation of alkenes with molecular oxygen in the presence of triethylsilane catalyzed by cobalt(II) diketonates was described for the first time by S. Isayama and T. Mukaiyama in 1989 [246][247]. Currently, this approach is one of the

• -dicyclohexenylpropan-2-yl acetate (56) catalyzed by cobalt complexed with 2,2,6,6-tetramethylheptane-3,5-dione (Co(THD)2) as the first step giving 1,3-bis(1-(triethylsilylperoxy)cyclohexyl)propan-2-yl acetate (57) that was subsequently transformed into the carbonyl-containing diperoxide (1,3-bis(1-(triethylsilylperoxy

• , desilylation, and recyclization accompanied by a ring opening of oxirane or oxetane (Scheme 62 and Scheme 63). Cobalt(II) acetylacetonate (acac) or bis-2,2,6,6-tetramethylheptane-3,5-dienoate (thd) were used as the catalyst for the peroxidation of 219. The cyclization of the intermediate peroxide 220 was

Recent advances in transition metal-catalyzed Csp²-monofluoro-, difluoro-, perfluoromethylation and trifluoromethylthiolation

• Grégory Landelle,
• Armen Panossian,
• Sergiy Pazenok,
• Jean-Pierre Vors and
• Frédéric R. Leroux

Beilstein J. Org. Chem. 2013, 9, 2476–2536, doi:10.3762/bjoc.9.287

• ]. In the same paper, the authors showed that cobalt perchlorate could also improve the yield of the uncatalyzed reaction. Iron sulfate, on the other hand, gave the same yield as in the absence of added metals. 4 Catalytic trifluoromethylthiolation Aryl trifluoromethyl sulfides (ArSCF3) play an

An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265

• pyridine structural class. Pyridine itself is produced industrially by either the traditional Chichibabin pyridine synthesis (Scheme 1, A), the Bönnemann reaction, a cobalt-catalysed cyclotrimerisation of alkynes and nitriles (Scheme 1, B) or the aerobic gas-phase condensation of croton aldehyde

• crude material in the subsequent Knoevenagel condensation with thiazolidinedione 1.68. In order to reduce the intermediate benzylidene double bond in this example sodium borohydride is used in the presence of cobalt chloride efficiently delivering pioglitazone in high purity. Other syntheses of

Flexible synthesis of anthracycline aglycone mimics via domino carbopalladation reactions

• Markus Leibeling and
• Daniel B. Werz

Beilstein J. Org. Chem. 2013, 9, 2194–2201, doi:10.3762/bjoc.9.258

• in 88% overall yield (over two steps). Another approach to non-linear systems utilizes a cobalt-mediated intramolecular [2 + 2 + 2]-cycloaddition of a triyne system 9 leading to the fourfold annulated ring system 10 in only one step [16]. Late stage functionalization led to the anticipated structural

A concise enantioselective synthesis of the guaiane sesquiterpene (−)-oxyphyllol

• Martin Zahel and
• Peter Metz

Beilstein J. Org. Chem. 2013, 9, 2028–2032, doi:10.3762/bjoc.9.239

• , 977 cm−1; GC–MS: m/z = 296 [M]+; anal. calcd for C15H20O4S: C 60.79, H 6.80; found: C 60.88, H 6.92. Alcohol 3: Epoxide 4 (100.0 mg, 454 μmol) and cobalt(II) acetylacetonate (23.3 mg, 91 μmol) were dissolved in THF (5 mL), and the solution was cooled to 0 °C. Oxygen was bubbled through the solution

Palladium(II)-catalyzed Heck reaction of aryl halides and arylboronic acids with olefins under mild conditions

• Tanveer Mahamadali Shaikh and
• Fung-E Hong

Beilstein J. Org. Chem. 2013, 9, 1578–1588, doi:10.3762/bjoc.9.180

• ][29][30][31]. Previously, we also reported the synthesis of cobalt-containing SPO ligands and their palladium complex. This was successfully applied as a catalytic precursor in oxidative Heck reactions [32]. However, these reactions were carried out at high temperatures with limited substrate scope

Spin state switching in iron coordination compounds

• Philipp Gütlich,
• Ana B. Gaspar and
• Yann Garcia

Beilstein J. Org. Chem. 2013, 9, 342–391, doi:10.3762/bjoc.9.39

• further examples of iron(II) SCO compounds have been published [7][8][9][10][11][12][13][16][17][18][19][20][21][22][23][24][25][26][27][28], and other coordination compounds of 3d transition elements such as cobalt(II) [29][30], and to a much lesser extent cobalt(III), chromium(II), manganese(II

• )↔t2g3eg2 (6A1g, HS). ΔrHL is even less pronounced in cobalt(II) SCO compounds (ΔrHL ≤ 10 pm) with ΔS = 1 transitions between the electron configurations t2g6eg1 (2Eg, LS)↔t2g5eg2 (4T1g, HS), because only one electron is transferred from antibonding eg* to t2g orbitals. The size of ΔrHL is important for the

• research than has NMR. SCO compounds of iron(III), iron(II), and cobalt(II), which are the 3d transition metal elements most actively studied with EPR, typically reveal characteristic spectra that are sufficiently well resolved in both HS and LS states. There is no spin–orbit coupling in SCO compounds of

Recent advances in transition-metal-catalyzed intermolecular carbomagnesiation and carbozincation

• Kei Murakami and
• Hideki Yorimitsu

Beilstein J. Org. Chem. 2013, 9, 278–302, doi:10.3762/bjoc.9.34

• ). Recently, iron and cobalt have been regarded as efficient catalysts for carbometalation of simple alkynes. Shirakawa and Hayashi reported that iron salts could catalyze arylmagnesiation of arylacetylenes in the presence of an N-heterocyclic carbene (NHC) ligand (Scheme 29) [103]. In 2012, Shirakawa and

• efficiently with good stereoselectivity (Scheme 33). A more versatile arylmetalation of dialkylacetylenes using arylzinc reagents in the presence of a cobalt catalyst was then reported by Yorimitsu and Oshima (Scheme 34, top) [115]. Treatment of dialkylacetylenes with arylzinc reagents in acetonitrile in the

• presence of a catalytic amount of cobalt bromide afforded the corresponding arylated intermediate 4e. Further study by Yoshikai revealed that the use of Xantphos as a ligand totally changed the products [116]. Smooth 1,4-hydride migration from 4A to 4B happened to provide organozinc 4f (Scheme 34, bottom

Tandem aldehyde–alkyne–amine coupling/cycloisomerization: A new synthesis of coumarins

• Maddi Sridhar Reddy,
• Nuligonda Thirupathi and
• Madala Haribabu

Beilstein J. Org. Chem. 2013, 9, 180–184, doi:10.3762/bjoc.9.21

• , cobalt, iridium and iron. Similarly, cycloisomerization of alkynols and alkynamines has also been an attractive approach for the synthesis of various known and new heterocyclic frameworks [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. Various alkynophilic catalysts such as

Copper-catalyzed CuAAC/intramolecular C–H arylation sequence: Synthesis of annulated 1,2,3-triazoles

• Rajkumar Jeyachandran,
• Harish Kumar Potukuchi and
• Lutz Ackermann

Beilstein J. Org. Chem. 2012, 8, 1771–1777, doi:10.3762/bjoc.8.202

• ][16]. This streamlining of organic synthesis has predominantly been accomplished with palladium [4][5][6][7][8][9][10][11][12][13][14][15][16], rhodium [17][18][19] or ruthenium [20][21][22] complexes [4][5][6][7][8][9][10][11][12][13][14][15][16]. However, less expensive nickel, cobalt, iron or

C2-Alkylation of N-pyrimidylindole with vinylsilane via cobalt-catalyzed C–H bond activation

• Zhenhua Ding and
• Naohiko Yoshikai

Beilstein J. Org. Chem. 2012, 8, 1536–1542, doi:10.3762/bjoc.8.174

• with a vinylsilane was achieved by using a cobalt catalyst generated in situ from CoBr2, bathocuproine, and cyclohexylmagnesium bromide. The reaction allows coupling between a series of N-pyrimidylindoles and vinylsilanes at a mild reaction temperature of 60 °C, affording the corresponding alkylated

• indoles in moderate to good yields. Keywords: alkylation; C–H functionalization; cobalt; indole; vinylsilane; Introduction The indole ring ubiquitously occurs in biologically active natural and unnatural compounds [1][2][3]. Consequently, there has been a strong demand for catalytic methods allowing

• palladium-catalyzed, norbornene-mediated C2-alkylation reaction with a broad spectrum of alkyl bromides [21]. Over the past few years, our group and others have explored C–H bond functionalization reactions using cobalt complexes as inexpensive transition-metal catalysts [22], which often feature mild

Synthesis of highly functionalized β-aminocyclopentanecarboxylate stereoisomers by reductive ring opening reaction of isoxazolines

• Melinda Nonn,
• Loránd Kiss,
• Reijo Sillanpää and
• Ferenc Fülöp

Beilstein J. Org. Chem. 2012, 8, 100–106, doi:10.3762/bjoc.8.10

•  3). Combinations of NaBH4 (as a mild and selective reducing agent) with cobalt, nickel, iridium or rhodium halide have previously been employed for cleavage of the isoxazoline ring system, which is otherwise inert to NaBH4 without such metal halide additives [50]. Accordingly, we investigated the

Recent developments in gold-catalyzed cycloaddition reactions

• Fernando López and
• José L. Mascareñas

Beilstein J. Org. Chem. 2011, 7, 1075–1094, doi:10.3762/bjoc.7.124

• , cobalt, nickel or palladium catalysts [4]. In recent years, however, platinum and particularly gold complexes have also emerged as excellent catalysts for the promotion of novel types of cycloaddition reactions, usually involving non-activated unsaturated systems (e.g., alkynes, allenes, alkenes or 1,3

A practical route to tertiary diarylmethylamides or -carbamates from imines, organozinc reagents and acyl chlorides or chloroformates

• Erwan Le Gall,
• Antoine Pignon and
• Thierry Martens

Beilstein J. Org. Chem. 2011, 7, 997–1002, doi:10.3762/bjoc.7.112

• , prepared in parallel via a cobalt-catalyzed procedure [36] was added and the resulting solution was stirred for 30 minutes at ambient temperature. The chromatographic purification of the crude oil afforded the expected diarylmethylamide or -carbamate 4. Representative experimental results are reported in

• continuous stirring. The aryl bromide (15 mmol) and anhydrous cobalt bromide (330 mg) were then added to the mixture, which was stirred at rt for additional 20 min. Stirring was then stopped and the surrounding solution was taken-up with a syringe. The solution was then added to the flask containing the

Nano copper oxide catalyzed synthesis of symmetrical diaryl sulfides under ligand free conditions

• K. Harsha Vardhan Reddy,
• V. Prakash Reddy,
• A. Ashwan Kumar,
• G. Kranthi and
• Y.V.D. Nageswar

Beilstein J. Org. Chem. 2011, 7, 886–891, doi:10.3762/bjoc.7.101

• cobalt [42] have been used in cross-coupling reactions, developed for the formation of carbon–sulfur bonds. Most of these coupling protocols involve the reaction between thiols and aryl halides, resulting in the formation of C–S bonds. Most of these metal-catalyzed reactions involve volatile and foul

Gold-catalyzed propargylic substitutions: Scope and synthetic developments

• Olivier Debleds,
• Eric Gayon,
• Emmanuel Vrancken and
• Jean-Marc Campagne

Beilstein J. Org. Chem. 2011, 7, 866–877, doi:10.3762/bjoc.7.99

• of a cobalt complex. In 1994, Murahashi [8] described in a seminal paper the propargylic substitution of monosubstituted alkynes bearing a good leaving group on the propargylic alcohol moiety, where a mechanism through a copper-allenylidene intermediate was postulated. Subsequently, asymmetric