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

• were conducted in a divided cell, giving only moderate yields [114][115]. A drastic increase in efficiency was obtained by employing sacrificial anodes [116], especially magnesium anodes [117][118]. The cathode material is again of great importance, with silver and platinum giving the highest

Synthesis of 2-trifluoromethylpyrazolo[5,1-a]isoquinolines via silver triflate-catalyzed or electrophile-mediated one-pot tandem reaction

• Xiaoli Zhou,
• Meiling Liu,
• Puying Luo,
• Yingjun Lai,
• Tangtao Yang and
• Qiuping Ding

Beilstein J. Org. Chem. 2014, 10, 2286–2292, doi:10.3762/bjoc.10.238

• Gynecology, Jiangxi Provincial people's Hospital, Nanchang, Jiangxi 330006, P. R. China 10.3762/bjoc.10.238 Abstract An efficient one-pot tandem cyclization/[3 + 2] cycloaddition reaction of N’-(2-alkynylbenzylidene)hydrazides with ethyl 4,4,4-trifluorobut-2-ynoate under silver triflate-catalyzed or

• electrophile-mediated conditions is described. Various trifluoromethylated pyrazolo[5,1-a]isoquinolines were afforded in moderate to excellent yield by this developed method. Keywords: [3 + 2] cycloaddition; electrophile; N’-(2-alkynylbenzylidene)hydrazide; silver triflate; tandem; Introduction Isoquinolines

• annulation of N’-(2-alkynylbenzylidene)hydrazides followed by an 1,3-dipolar cycloaddition. Results and Discussion Based on Wu’s work on the silver triflate-catalyzed tandem reaction of N’-(2-alkynylbenzylidene)hydrazides with dimethyl acetylenedicarboxylate [28], we started our research by examining the

Second generation silver(I)-mediated imidazole base pairs

• Susanne Hensel,
• Nicole Megger,
• Kristina Schweizer and
• Jens Müller

Beilstein J. Org. Chem. 2014, 10, 2139–2144, doi:10.3762/bjoc.10.221

• linearly coordinated silver(I) ion inserted in-between two complementary artificial imidazole nucleosides (Scheme 1, top). The NMR-based solution structure of a DNA duplex with three contiguous imidazole–Ag(I)–imidazole represented the first experimental proof that a B-DNA conformation is compatible with

• creating long contiguous metal-containing sections within oligonucleotide duplexes [35]. A closer inspection of the experimental NMR structure reveals that the silver(I) ions, despite being lined up inside the duplex along the helical axis, still appear to be accessible from the outside of the duplex

• attempt to increase the stability of the imidazole–Ag(I)–imidazole base pairs, additional shielding of the central silver(I) ions could be accomplished by introducing methyl groups on the imidazole moieties. A comparison of the pKa values [36] of 1-methylimidazole (pKa = 7.21), 1,2-dimethylimidazole (pKa

Supercritical carbon dioxide: a solvent like no other

• Jocelyn Peach and
• Julian Eastoe

Beilstein J. Org. Chem. 2014, 10, 1878–1895, doi:10.3762/bjoc.10.196

• highly CO2-philic following the successful stabilisation of silver nanoparticles using isostearic acid [74]. It was compared to TMN-6 (Table 1, compound 12), a non-ionic surfactant with highly branched alkyl tails and around eight oxyethylene units which has previously been reported as solubilising water

Theoretical study of the adsorption of benzene on coinage metals

• Werner Reckien,
• Melanie Eggers and
• Thomas Bredow

Beilstein J. Org. Chem. 2014, 10, 1775–1784, doi:10.3762/bjoc.10.185

• = Cu), silver (M = Ag) and gold (M = Au) is studied on the basis of density functional theory (DFT) calculations with an empirical dispersion correction (D3). Variants of the Perdew–Burke–Ernzerhof functionals (PBE, RPBE and RevPBE) in combination with different versions of the dispersion correction

• crucial role for the adsorption of large aromatic compounds on metal surfaces [9][10][11]. This holds in particular for the adsorption on the coinage metals copper, silver and gold. Therefore, a theoretical treatment of this process requires methods that provide an accurate description of these weak

• dependent C6 coefficients of the D3 correction. We checked this by calculating the C3 coefficients for the benzene adsorption on the Au(111) surface. Previous theoretical studies of the adsorption of organic compounds on silver and gold surfaces resulted in a good agreement with experimental results [9][10

Synthesis of trifluoromethyl-substituted pyrazolo[4,3-c]pyridines – sequential versus multicomponent reaction approach

• Barbara Palka,
• Angela Di Capua,
• Maurizio Anzini,
• Gyté Vilkauskaité,
• Algirdas Šačkus and
• Wolfgang Holzer

Beilstein J. Org. Chem. 2014, 10, 1759–1764, doi:10.3762/bjoc.10.183

• . Oximes derived from (intermediate) 5-alkynyl-1-phenyl-3-trifluoromethyl-1H-pyrazole-4-carbaldehydes were transformed into the corresponding 1H-pyrazolo[4,3-c]pyridine 5-oxides by silver triflate-catalyzed cyclization. Detailed NMR spectroscopic investigations (1H, 13C, 15N and 19F) were undertaken with

Convergent synthetic methodology for the construction of self-adjuvanting lipopeptide vaccines using a novel carbohydrate scaffold

• Vincent Fagan,
• Istvan Toth and
• Pavla Simerska

Beilstein J. Org. Chem. 2014, 10, 1741–1748, doi:10.3762/bjoc.10.181

• addition of a catalytic amount of H2SO4 to ε-caprolactone in methanol, according to Duffy et al. [23]. However, the procedure was optimized by decreasing the reaction time from 48 h to 30 minutes and purification by distillation was not required. The glycosylation was carried out by addition of silver(I

Glycosystems in nanotechnology: Gold glyconanoparticles as carrier for anti-HIV prodrugs

• Fabrizio Chiodo,
• Marco Marradi,
• Javier Calvo,
• Eloisa Yuste and
• Soledad Penadés

Beilstein J. Org. Chem. 2014, 10, 1339–1346, doi:10.3762/bjoc.10.136

• nanoparticles that showed surprisingly anti-HIV activity, probably due to the high-local concentration of the drug derivative on the gold surface. Other inorganic nanomaterials have also been explored as carriers for therapeutic drugs against HIV. For example, silver nanoparticles coated with poly(vinyl

Visible-light photoredox catalyzed synthesis of pyrroloisoquinolines via organocatalytic oxidation/[3 + 2] cycloaddition/oxidative aromatization reaction cascade with Rose Bengal

• Carlos Vila,
• Jonathan Lau and
• Magnus Rueping

Beilstein J. Org. Chem. 2014, 10, 1233–1238, doi:10.3762/bjoc.10.122

• type of compounds [22][23][24][25][26]. Recently, several metal mediated syntheses using a [3 + 2] cycloaddition reaction have been described in the literature. Porco Jr. et al. [27] described a silver-catalyzed cycloisomerization/dipolar cycloaddition for the synthesis of the pyrrolo[2,1-a

Synthesis of zearalenone-16-β,D-glucoside and zearalenone-16-sulfate: A tale of protecting resorcylic acid lactones for regiocontrolled conjugation

• Hannes Mikula,
• Julia Weber,
• Dennis Svatunek,
• Philipp Skrinjar,
• Gerhard Adam,
• Rudolf Krska,
• Christian Hametner and
• Johannes Fröhlich

Beilstein J. Org. Chem. 2014, 10, 1129–1134, doi:10.3762/bjoc.10.112

• be formed by rearrangement of 11 when activated in the presence of a weak acceptor (Scheme 2B) [31][32][33][34]. Königs–Knorr glucosylation, which in general is most frequently used for the glucosylation of phenols, using commercially available bromo sugar 13 activated by silver(I) salts or under

Novel indolin-2-one-substituted methanofullerenes bearing long n-alkyl chains: synthesis and application in bulk-heterojunction solar cells

• Irina P. Romanova,
• Andrei V. Bogdanov,
• Inessa A. Izdelieva,
• Vasily A. Trukhanov,
• Gulnara R. Shaikhutdinova,
• Dmitry G. Yakhvarov,
• Shamil K. Latypov,
• Vladimir F. Mironov,
• Vladimir A. Dyakov,
• Ilya V. Golovnin,
• Dmitry Yu. Paraschuk and
• Oleg G. Sinyashin

Beilstein J. Org. Chem. 2014, 10, 1121–1128, doi:10.3762/bjoc.10.111

• ) solution in the presence of Bu4NBF4 (0.1 M) with a potential sweep rate of 50 mV·s–1 with the help of a PI-50-1 potentiostat. A silver electrode Ag/AgNO3 (0.01 M solution in MeCN) was served as the reference electrode (E°(Fc/Fc+) = +0.20 V). A glassy carbon (GC) electrode with a working surface of 3.14 mm2

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

• were isolated as their thiophosphine analogues 135 and 136. Hayashi and co-workers have reported a rhodium-catalyzed phosphination of alkynes 134b using silylphosphines 137 as phosphinating agents (Table 15) [108]. The cationic rhodium catalyst was generated in situ by adding silver triflate to a

• 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

Towards allosteric receptors – synthesis of β-cyclodextrin-functionalised 2,2’-bipyridines and their metal complexes

• Christopher Kremer,
• Gregor Schnakenburg and
• Arne Lützen

Beilstein J. Org. Chem. 2014, 10, 814–824, doi:10.3762/bjoc.10.77

• -functionalised bipyridines in hands, we then examined their coordination behaviour towards different transition metal ions (or their complexes) to see whether these could act as effectors. In our previous work, silver(I) and copper(I) salts as well as pentacarbonylrhenium(I) chloride proved to be good effectors

• for our allosteric receptors [20][21][22]. Hence, we also started with these here. Unfortunately, silver(I) ions turned out to be not effective in this case. Although, they seem to form complexes with compounds 1–3, we did not observe any of the characteristic shifts of the signals assigned to the

• protons of the bipyridine moiety that would indicate successful binding of the silver(I) ions to the nitrogen atoms. Thus, we conclude that the soft silver(I) ions rather bind to one of the sulfur atoms of the thiourea groups. This, however, does not cause the necessary conformational change of the

Phosphinate-containing heterocycles: A mini-review

• Olivier Berger and
• Jean-Luc Montchamp

Beilstein J. Org. Chem. 2014, 10, 732–740, doi:10.3762/bjoc.10.67

• -Dieckmann condensation. Palladium-catalyzed oxidative arylation. Tandem cross-coupling/Dieckmann condensation. Rhodium-catalyzed double [2 + 2 + 2] cycloaddition. Silver oxide-mediated alkyne–arene annulation. Silver acetate-mediated alkyne–arene annulation. Cyclization through phosphinylation/alkylation of

Synthesis of (2S,3R)-3-amino-2-hydroxydecanoic acid and its enantiomer: a non-proteinogenic amino acid segment of the linear pentapeptide microginin

• Rajendra S. Rohokale and
• Dilip D. Dhavale

Beilstein J. Org. Chem. 2014, 10, 667–671, doi:10.3762/bjoc.10.59

• multicomponent condensation reactions of aldehyde, an amine and ketene silyl acetal derivatives to get the vicinal hydroxylamino acids [17]. In addition, a few strategies employ a chiral pool approach. For example, Wee et al. utilized the zinc-silver-mediated reductive elimination of α-D-lyxofuranosyl

Silver and gold-catalyzed multicomponent reactions

• Giorgio Abbiati and
• Elisabetta Rossi

Beilstein J. Org. Chem. 2014, 10, 481–513, doi:10.3762/bjoc.10.46

• Giorgio Abbiati Elisabetta Rossi Dipartimento di Scienze Farmaceutiche, Sezione di Chimica Generale e Organica “A. Marchesini”, Università degli Studi di Milano, Via Venezian, 21 – 20133 Milano, Italy 10.3762/bjoc.10.46 Abstract Silver and gold salts and complexes mainly act as soft and

• carbophilic Lewis acids even if their use as σ-activators has been rarely reported. Recently, transformations involving Au(I)/Au(III)-redox catalytic systems have been reported in the literature. In this review we highlight all these aspects of silver and gold-mediated processes and their application in

• multicomponent reactions. Keywords: A3-coupling; gold; multicomponent reactions; silver; Introduction Coinage metals (copper, silver and gold) are extensively used in the homogenous catalysis of organic reactions. Similarities and differences in the catalytic activity of these elements have been recently

Aminofluorination of 2-alkynylanilines: a Au-catalyzed entry to fluorinated indoles

• Antonio Arcadi,
• Emanuela Pietropaolo,
• Antonello Alvino and
• Véronique Michelet

Beilstein J. Org. Chem. 2014, 10, 449–458, doi:10.3762/bjoc.10.42

• -fluoroindoles from 2-alkynylanilines has been reported to fail to occur [52] using previously developed silver catalysts [68]. In our cases, the fluorination reactions were conducted at 0 °C to avoid overoxidation processes. Conclusion In conclusion, we have contributed to the development of one-pot gold

Deoxygenative gem-difluoroolefination of carbonyl compounds with (chlorodifluoromethyl)trimethylsilane and triphenylphosphine

• Fei Wang,
• Lingchun Li,
• Chuanfa Ni and
• Jinbo Hu

Beilstein J. Org. Chem. 2014, 10, 344–351, doi:10.3762/bjoc.10.32

• performed in benzonitrile (bp ~190 °C) at 80 °C using a slight excess of silver chloride under the catalysis of TBAC, a full conversion of TMSCF2Br afforded TMSCF2Cl in 54% yield. Lowering the temperature to room temperature (rt) could improve the yield to 80% (Scheme 3). It is believed that the lower

• solubility of silver bromide than silver chloride in benzonitrile provides the driving force for this bromo–chloro exchange reaction. At first, the olefination of 1-naphthaldehyde (1a) or benzaldehyde (1b) by using the combination of TMSCF2Cl and PPh3 was tried. Conceiving that the chloride ion might be

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

• Curtius rearrangement, upon heating the intermediate isocyanate was trapped with EtOH to yield ethyl carbamate protected amine 141. Deprotection of the Alloc-group [126] and chloro carbamate formation furnished 142. Exposure of this compound to a silver source led to the formation of the five-membered

• to give pentacycle 172. Reduction of the nitro group was followed by Cbz-protection. Allylic alcohol 173 resulted from radical allylic bromination followed by displacement of bromine through water under silver-catalysis. Eschenmoser–Claisen rearrangement [148] led to the formation of the remaining

• [199] upon treatment with silver benzoate. The intermediate ketene 235 underwent stereospecific DVCPR through transition state 235' under the reaction conditions to give enone 236 in excellent yield. This constituted the first example of the direct formation of an enone through a DVCPR. Stephenson and

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 cyclization was performed in toluene, 1,4-dioxane, or 1,2-dichloroethane at 80 °C for 3 h in the presence of p-benzoquinone or silver carbonate as the oxidizing agent for Pd(0) that was formed in the catalytic cycle. To the best of our knowledge, this method is the first example of a palladium

Multigramme synthesis and asymmetric dihydroxylation of a 4-fluorobut-2E-enoate

• James A. B. Laurenson,
• John A. Parkinson,
• Jonathan M. Percy,
• Giuseppe Rinaudo and
• Ricard Roig

Beilstein J. Org. Chem. 2013, 9, 2660–2668, doi:10.3762/bjoc.9.301

• literature (Scheme 3); silver mediated fluorination of butenoyl bromide 15 is known [14] delivering 16 in moderate yield but via a slow and expensive reaction. Wittig reaction, following in situ reduction of ethyl fluoroacetate (17) has been reported [15], while Purrington [16] prepared 19 by direct

New developments in gold-catalyzed manipulation of inactivated alkenes

• Michel Chiarucci and
• Marco Bandini

Beilstein J. Org. Chem. 2013, 9, 2586–2614, doi:10.3762/bjoc.9.294

• . Enantioselective variant of this transformation was recently reported by Mikami and co-workers [46]. The protocol focuses on the use of a gold complex comprising the racemic 2,2'-bis(diphenylphosphino)-1,1'-biphenyl digold(I) complex 33 which, in combination with enantiopure silver phosphate 34, afforded the

• was heated in presence of the silver free gold complex 20c a variety of highly substituted azabicyclo[4.2.0]oct-5-enes 84 was obtained in good yields as a single regio- and diastereoisomer. The protocol displayed excellent functional group compatibility and efficient transfer of chirality was observed

• ligand and chiral silver phosphate. Intramolecular [Au(I)]-catalyzed hydroamination of N-allyl-N’-aryl ureas. (PNP = pNO2-C6H4, PMP = pMeO-C6H4). [Au(I)]-catalyzed hydroamination of alkenes with ammonium salts. Enantioselective [Au(I)]-catalyzed intermolecular hydroamination of alkenes with cyclic ureas

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

• 1,10-phenanthroline and KF respectively [73]. In addition to activating the silyl group of the trifluoromethylating agent, the silver salt also acts as a stabilizer for the CF3− species and prevents its self-decomposition (Figure 4). As a result, the more economical TMSCF3 can be employed, and good

• yields were observed for both electron-rich and electron-poor aryl iodides in this cooperative silver-assisted copper-catalyzed trifluoromethylation (Table 12). Even if the pioneering work of H. Amii and Z. Q. Weng resulted in the development of reliable and robust catalytic systems, they suffer from the

• trifluoromethyl arenes without the use of trifluoromethylating reagents rely on an aryl CF2–F bond disconnection. A clever example of this strategy has been described by V. Gouverneur et al. starting from aryl difluoroacetic acids [117]. The latters can react with Selectfluor® and a catalytic amount of silver

Synthetic scope and DFT analysis of the chiral binap–gold(I) complex-catalyzed 1,3-dipolar cycloaddition of azlactones with alkenes

• María Martín-Rodríguez,
• Luis M. Castelló,
• Carmen Nájera,
• José M. Sansano,
• Olatz Larrañaga,
• Abel de Cózar and
• Fernando P. Cossío

Beilstein J. Org. Chem. 2013, 9, 2422–2433, doi:10.3762/bjoc.9.280

• silver(I) salt. These complexes were used immediately after filtration through a celite path. Particularly, complexes 3 and 4 (X = TFA) could be isolated in 96 and 89% yield, respectively, but other gold(I) complexes (see Table 1) with different anions were generated in situ and used as catalysts in the

• 10). The enantiomerically pure form of 7aa with opposite absolute configuration was isolated by working in the presence of [(Ra)-Binap·AuTFA]2 complex (Table 1, entry 11). Surprisingly, no reaction was observed in the presence of silver(I) complex (Sa)-Binap·AgTFA (Table 1, entry 15). In this section

Gold(I)-catalyzed enantioselective cycloaddition reactions

• Fernando López and
• José L. Mascareñas

Beilstein J. Org. Chem. 2013, 9, 2250–2264, doi:10.3762/bjoc.9.264

• diastereoisomers with high enantioselectivities (84–95% ee) [81]. Optimal conditions for the enantioselective variant of the process involved the use of the chiral gold complex Au5 (3.8 mol %), derived from MeO-DTBM-Biphep, in combination with AgOTf. The requirement of equimolar amounts of the silver salt and the