Cationic Pd(II)-catalyzed C–H activation/cross-coupling reactions at room temperature: synthetic and mechanistic studies

• Takashi Nishikata,
• Alexander R. Abela,
• Shenlin Huang and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2016, 12, 1040–1064, doi:10.3762/bjoc.12.99

• complexes are commercially available, they may also be generated in situ via a variety of routes (Scheme 2), including: (a) reaction of a palladium complex with a non-coordinating anion source, usually an acid or metal salt; (b) reaction of Pd(II) halide complexes and silver salts [143][144][145]; (c

• ”), there was a noticeable drop in the extent of conversion. In addition, lower loadings of HBF4, silver salt, or the palladium catalyst also gave inferior results. In the case of C–H activation/Suzuki–Miyaura coupling reactions, the commercially available, pre-formed cationic Pd(II) catalyst [Pd(MeCN)4

• were examined, such as Pd(OAc)2, PdCl2Ln, Pd2(dba)3, in the absence of added acid, but none led to cross-coupling at room temperature. 1,4-Benzoquinone (BQ) was found to be an effective additive in promoting the reaction, while addition of stoichiometric metal salts (e.g., silver or copper salts) was

The synthesis of functionalized bridged polycycles via C–H bond insertion

• Jiun-Le Shih,
• Po-An Chen and
• Jeremy A. May

Beilstein J. Org. Chem. 2016, 12, 985–999, doi:10.3762/bjoc.12.97

• [31]. Metal-catalyzed reactions Copper The earliest example to our knowledge of transition metal catalysis for the formation of bridged rings via C–H bond insertion was Wolff’s use of copper (Scheme 6) [32][33]. Silver was also examined as a possible catalyst, but then a Wolff rearrangement was the

Stimuli-responsive HBPS-g-PDMAEMA and its application as nanocarrier in loading hydrophobic molecules

• Yongsheng Chen,
• Li Wang,
• Haojie Yu,
• Zain-Ul-Abdin,
• Ruoli Sun,
• Guanghui Jing,
• Rongbai Tong and
• Zheng Deng

Beilstein J. Org. Chem. 2016, 12, 939–949, doi:10.3762/bjoc.12.92

• reactions were performed under argon and argon gas was purified by passing through four columns loaded with potassium hydroxide, 4 Å molecular sieves, silver molecular sieves and potassium/sodium alloy. Vinylbenzyl chloride (VBC) was purified by passing through a column packed with alkaline alumina. DMAEMA

Bi- and trinuclear copper(I) complexes of 1,2,3-triazole-tethered NHC ligands: synthesis, structure, and catalytic properties

• Shaojin Gu,
• Jiehao Du,
• Jingjing Huang,
• Huan Xia,
• Ling Yang,
• Weilin Xu and
• Chunxin Lu

Beilstein J. Org. Chem. 2016, 12, 863–873, doi:10.3762/bjoc.12.85

• 2.024(6)–2.092(6) Å, respectively, which are slightly longer than in dinuclear complexes 3 and 4. Benzimidazolylidene acts as a bridging ligand in a u2 mode and bonded equally to two Cu(I) ions, which is only observed in a few silver(I) and copper(I) complexes. Catalytic application in CuAAC reactions

Recent advances in C(sp³)–H bond functionalization via metal–carbene insertions

• Bo Wang,
• Di Qiu,
• Yan Zhang and
• Jianbo Wang

Beilstein J. Org. Chem. 2016, 12, 796–804, doi:10.3762/bjoc.12.78

• development of intermolecular C–H insertion in the application of C(sp3)–H bond functionalizations, especially for light alkanes, is reviewed. The challenging problem of regioselectivity in C–H bond insertions has been tackled by the use of sterically bulky metal catalysts, such as metal porphyrins and silver

• and with up to 93% ee. Pérez and co-workers have explored different types of catalysts based on copper and silver in metal–carbene C(sp3)–H insertions. Tris(pyrazoly)borate complexes of copper (TpCu) [32][33][34] and silver (TpAg) [35][36][37] have been employed for C(sp3)–H insertion of alkanes

• and Etienne reported a perfluorinated F21-tris(pyrazoly)borate (F21-Tp) scorpionate ligand, which enhanced alkane C–H functionalization by carbene insertion with (F21-Tp)Cu and (F21-Tp)Ag catalysts (Figure 1) [38]. In particular, with silver catalyst remarkably low catalyst loading (ca. 0.5%), and

A selective and mild glycosylation method of natural phenolic alcohols

• Mária Mastihubová and
• Monika Poláková

Beilstein J. Org. Chem. 2016, 12, 524–530, doi:10.3762/bjoc.12.51

• look for milder conditions for an efficient and inexpensive method of glycosylation while excluding the use of toxic mercury salts as promoter (Helferich reaction) or silver salts. The latter are often rather expensive, moisture and light sensitive, and uncomfortable to handle. Accordingly, various

Simple activation by acid of latent Ru-NHC-based metathesis initiators bearing 8-quinolinolate co-ligands

• Julia Wappel,
• Roland C. Fischer,
• Luigi Cavallo,
• Christian Slugovc and
• Albert Poater

Beilstein J. Org. Chem. 2016, 12, 154–165, doi:10.3762/bjoc.12.17

• -heterocyclic carbene bearing precursor complexes M31, HovII or M32 with excess of 5,7-dichloro-8-hydroxyquinoline or 5,7-dibromo-8-hydroxyquinoline in the presence of excess Cs2CO3 as the base (see Scheme 1). The silver-free method [41] resulted in any case in the formation of at least two new products (as

Carbon–carbon bond cleavage for Cu-mediated aromatic trifluoromethylations and pentafluoroethylations

• Tsuyuka Sugiishi,
• Hideki Amii,
• Kohsuke Aikawa and
• Koichi Mikami

Beilstein J. Org. Chem. 2015, 11, 2661–2670, doi:10.3762/bjoc.11.286

• the addition of silver salts is effective for the copper-mediated trifluoromethylation of aryl iodides [38] (Scheme 5). The amount of copper used in the reaction was reduced to 30 or 40 mol % by adding a small amount of Ag2O. As a related decarboxylative transformation, silver-mediated aromatic

Synthesis of Xenia diterpenoids and related metabolites isolated from marine organisms

• Tatjana Huber,
• Lara Weisheit and
• Thomas Magauer

Beilstein J. Org. Chem. 2015, 11, 2521–2539, doi:10.3762/bjoc.11.273

• product 63 in very good yield, however, as a mixture of lactol epimers (α/β ≈ 56:44). Silyl protection of the lactol and subsequent Tebbe olefination [42] of the ketone group installed the exocyclic double bond of the nine-membered carbocycle. Desilylation followed by oxidation with silver carbonate then

Copper-catalyzed asymmetric conjugate addition of organometallic reagents to extended Michael acceptors

• Thibault E. Schmid,
• Sammy Drissi-Amraoui,
• Christophe Crévisy,
• Olivier Baslé and
• Marc Mauduit

Beilstein J. Org. Chem. 2015, 11, 2418–2434, doi:10.3762/bjoc.11.263

• example of copper-catalyzed selective 1,4-ACA of low-cost trialkylaluminium reagents on extended Michael acceptors in 2008 [39]. The reported catalytic system, featuring Cu(OTf)2 and sulfonated NHC-based silver complex L15 as the ligand source, appeared as the most potent system in the conversion of

Influence of bulky yet flexible N-heterocyclic carbene ligands in gold catalysis

• Alba Collado,
• Scott R. Patrick,
• Danila Gasperini,
• Sebastien Meiries and
• Steven P. Nolan

Beilstein J. Org. Chem. 2015, 11, 1809–1814, doi:10.3762/bjoc.11.196

• transformations. Gagosz-type species have been typically prepared by reacting the corresponding [Au(L)Cl] derivative (L = PR3, NHC) with AgNTf2 [46][47]. Alternative protocols that avoid the use of silver salts involve the treatment of gold-hydroxide [48] or gold-acetonyl [49] complexes with

• trifluoromethanesulfonimide. Following this silver-free procedure, [Au(ITent)(OH)] complexes 4–6 were reacted with HNTf2 to obtain the corresponding [Au(ITent)(NTf2)] species 7–9 which were isolated as white solids in good to excellent yields (Scheme 2). Complexes 7–9 were characterised by 1H, 13C{1H}, and 19F{1H} NMR

• measurements in solution of the [Ni(ITent)CO3] complexes [21][42]. Synthesis of gold complexes bearing the ITent ligands. Silver-free synthesis of [Au(ITent)(NTf2)] complexes. Influence of the ITent ligands in gold-catalysed alkyne hydration.a Influence of the ITent ligands in gold-catalysed nitrile

Synthesis and structures of ruthenium–NHC complexes and their catalysis in hydrogen transfer reaction

• Chao Chen,
• Chunxin Lu,
• Qing Zheng,
• Shengliang Ni,
• Min Zhang and
• Wanzhi Chen

Beilstein J. Org. Chem. 2015, 11, 1786–1795, doi:10.3762/bjoc.11.194

• reaction of halides with silver complexes (AgPF6 or AgBF4) in acetonitrile solution [20]. The reaction in refluxing acetonitrile is more convenient than the above mentioned procedure. The formulations of complexes 1 and 2 were first characterized by NMR measurements and further confirmed by elemental

Pyridinoacridine alkaloids of marine origin: NMR and MS spectral data, synthesis, biosynthesis and biological activity

• Louis P. Sandjo,
• Victor Kuete and
• Maique W. Biavatti

Beilstein J. Org. Chem. 2015, 11, 1667–1699, doi:10.3762/bjoc.11.183

• . Precursors A and B were adequately prepared and used to synthesize 1 and 4 in a one-pot manner in the presence of cesium chloride, silver oxide in methanol and acetic acid under nitrogen atmosphere. The reaction lasted 90 min at 40 °C. The proposed mechanism postulated that silver oxide oxidized the N

Latent ruthenium–indenylidene catalysts bearing a N-heterocyclic carbene and a bidentate picolinate ligand

• Thibault E. Schmid,
• Florian Modicom,
• Adrien Dumas,
• Etienne Borré,
• Loic Toupet,
• Olivier Baslé and
• Marc Mauduit

Beilstein J. Org. Chem. 2015, 11, 1541–1546, doi:10.3762/bjoc.11.169

• Cedex, France 10.3762/bjoc.11.169 Abstract A silver-free methodology was developed for the synthesis of unprecedented N-heterocyclic carbene ruthenium indenylidene complexes bearing a bidentate picolinate ligand. The highly stable (SIPr)(picolinate)RuCl(indenylidene) complex 4a (SIPr = 1,3-bis(2-6

• in model ring closing metathesis and cross-metathesis transformations. Results and Discussion With the objective to develop an attractive strategy for the synthesis of indenylidene-picolinic ruthenium complexes, we initially attempted their preparation using a silver-free methodology. In fact, silver

Tetrathiafulvalene-based azine ligands for anion and metal cation coordination

• Awatef Ayadi,
• Aziz El Alamy,
• Olivier Alévêque,
• Magali Allain,
• Nabil Zouari,
• Mohammed Bouachrine and
• Abdelkrim El-Ghayoury

Beilstein J. Org. Chem. 2015, 11, 1379–1391, doi:10.3762/bjoc.11.149

• were performed in a three-electrode cell equipped with a platinum millielectrode as the working electrode , a platinum wire as a counter electrode and a silver wire Ag/Ag+ used as a reference electrode. The electrolytic media involved a 0.1 mol/L solution of (n-Bu4N)PF6 in dichloromethane/acetonitrile

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

Glycoluril–tetrathiafulvalene molecular clips: on the influence of electronic and spatial properties for binding neutral accepting guests

• Yoann Cotelle,
• Marie Hardouin-Lerouge,
• Stéphanie Legoupy,
• Olivier Alévêque,
• Eric Levillain and
• Piétrick Hudhomme

Beilstein J. Org. Chem. 2015, 11, 1023–1036, doi:10.3762/bjoc.11.115

• ]. Electrochemical measurements were carried out using a platinum wire counter electrode and a silver wire as a quasi-reference electrode with a Biologic SP-150 potentiostat driven by the EC-Lab software including ohmic drop compensation. Experiments were recorded in dry HPLC-grade acetonitrile and dichloromethane

Interactions between tetrathiafulvalene units in dimeric structures – the influence of cyclic cores

• Huixin Jiang,
• Virginia Mazzanti,
• Christian R. Parker,
• Søren Lindbæk Broman,
• Jens Heide Wallberg,
• Karol Lušpai,
• Adam Brincko,
• Henrik G. Kjaergaard,
• Anders Kadziola,
• Peter Rapta,
• Ole Hammerich and
• Mogens Brøndsted Nielsen

Beilstein J. Org. Chem. 2015, 11, 930–948, doi:10.3762/bjoc.11.104

• working electrode was a circular glassy carbon disk (d = 3 mm), the counter electrode was a platinum wire and the reference electrode was a silver wire immersed in the solvent-supporting electrolyte mixture and separated from the solution containing the substrate by a ceramic frit. The potential of the

• . Triggering is performed by the software package PotMaster v2x40 (HEKA Electronik, Germany). For standard in situ ESR/vis–NIR spectroelectrochemical experiments an ESR flat cell was used. A laminated platinum mesh as the working electrode, a silver wire as the pseudo-reference electrode, and a platinum wire

Gold-catalyzed formation of pyrrolo- and indolo-oxazin-1-one derivatives: The key structure of some marine natural products

• Sultan Taskaya,
• Nurettin Menges and
• Metin Balci

Beilstein J. Org. Chem. 2015, 11, 897–905, doi:10.3762/bjoc.11.101

• fully recovered. Gold N-heterocyclic carbene complexes, in conjunction with a silver salt, were found to efficiently catalyze different types of reactions [67][68][69]. Therefore, 15 was reacted with [(NHC)AuCl] complex in the presence of AgOTf as the cocatalyst in chloroform. Beside the expected

N-Alkyl derivatives of diosgenyl 2-amino-2-deoxy-β-D-glucopyranoside; synthesis and antimicrobial activity

• Agata Walczewska,
• Daria Grzywacz,
• Dorota Bednarczyk,
• Małgorzata Dawgul,
• Andrzej Nowacki,
• Wojciech Kamysz,
• Beata Liberek and
• Henryk Myszka

Beilstein J. Org. Chem. 2015, 11, 869–874, doi:10.3762/bjoc.11.97

• -hydroxy derivatives of D-glucose and L-rhamnose [49]. Glycosylation of diosgenin with twelve different derivatives of D-glucosamine (2a–d, 3a–d, and 5a–d), was examined using “normal” and “reverse” procedures [50] (Table 1). In the “normal” procedure, the promoter (silver triflate or trimethylsilyl

Impact of multivalent charge presentation on peptide–nanoparticle aggregation

• Daniel Schöne,
• Boris Schade,
• Christoph Böttcher and
• Beate Koksch

Beilstein J. Org. Chem. 2015, 11, 792–803, doi:10.3762/bjoc.11.89

• immobilization of the peptide on the nanoparticle surface in multiple layers. Thus, the concentration of dissolved peptide is dramatically decreased and a CD signal can not be detected anymore. A similar effect could be described by Calzolai and coworkers using silver nanoparticles [40]. Furthermore, the minimum

Weakly nucleophilic potassium aryltrifluoroborates in palladium-catalyzed Suzuki–Miyaura reactions: relative reactivity of K[4-RC₆F₄BF₃] and the role of silver-assistance in acceleration of transmetallation

• Vadim V. Bardin,
• Anton Yu. Shabalin and
• Nicolay Yu. Adonin

Beilstein J. Org. Chem. 2015, 11, 608–616, doi:10.3762/bjoc.11.68

• of Catalysis, SB RAS, Acad. Lavrentjev Ave. 5, Novosibirsk, 630090, Russian Federation 10.3762/bjoc.11.68 Abstract Small differences in the reactivity of weakly nucleophilic potassium aryltrifluoroborates are revealed in the silver-assisted Pd-catalyzed cross-coupling of K[4-RC6F4BF3] (R = H, Bu

• , MeO, EtO, PrO, iPrO, BuO, t-BuO, CH2=CHCH2O, PhCH2O, PhCH2CH2O, PhO, F, pyrazol-1-yl, pyrrol-1-yl, and indol-1-yl) with ArX (4-BrC6H4CH3, 4-IC6H4F and 3-IC6H4F). An assumed role of silver(I) compounds AgmY (Y = O, NO3, SO4, BF4, F) consists in polarization of the Pd–X bond in neutral complex ArPdLnX

• correlation between the reactivity of K[4-RC6F4BF3] and substituent electron parameters, σI and σR°, of the aryl group 4-RC6F4 was found. Keywords: potassium polyfluoroaryltrifluoroborate; silver(I) acceleration; Suzuki–Miyaura reaction; Introduction The palladium-catalyzed reaction of organoboron compounds

Direct access to pyrido/pyrrolo[2,1-b]quinazolin-9(1H)-ones through silver-mediated intramolecular alkyne hydroamination reactions

• Hengshuai Wang,
• Shengchao Jiao,
• Kerong Chen,
• Xu Zhang,
• Linxiang Zhao,
• Dan Liu,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2015, 11, 416–424, doi:10.3762/bjoc.11.47

• . The methodology is applicable to a wide scope of substrates and produces a series of fused quinazolinone heterocycles in good to excellent yields. Keywords: heterocyclic molecules; intramolecular alkyne hydroamination; silver; Introduction Quinazolinone is a core skeleton for naturally existing

• studied for the construction of heterocycles. We have reported on a highly efficient gold/silver-catalyzed intramolecular hydroamination of terminal alkynes in water for the synthesis of fused tricyclic xanthenes [34]. On the basis of this methodology, we have also afforded two fused benzimidazoles

• through silver-catalyzed intramolecular hydroamination from readily available starting materials with a long-chain alkyne [35][36]. Motivated by the unique structural properties and the biological activities characteristic of the vasicinone type alkaloids, we extended our work in this direction by

Electrochemical oxidation of cholesterol

• Jacek W. Morzycki and
• Andrzej Sobkowiak

Beilstein J. Org. Chem. 2015, 11, 392–402, doi:10.3762/bjoc.11.45

• nanoparticles [65], and zinc oxide nanorods directly grown on silver [66], has also been reported on. The “cholesterol self-powered biosensor” [67], in which the cathodic process is determined by cholesterol oxidase and on an anode phenothiazine-mediated oxidation of cholesterol as well as immobilization of

IR and electrochemical synthesis and characterization of thin films of PEDOT grown on platinum single crystal electrodes in [EMMIM]Tf₂N ionic liquid

• Andrea P. Sandoval,
• Marco F. Suárez-Herrera and
• Juan M. Feliu

Beilstein J. Org. Chem. 2015, 11, 348–357, doi:10.3762/bjoc.11.40

• on the nature and number of charge carriers take place. Experimental The electrochemical experiments were performed in single compartment glass cells. A platinum wire was used as counter electrode, and a silver wire was used as the pseudoreference electrode. Platinum single crystals were used as