Continuous preparation of carbon-nanotube-supported platinum catalysts in a flow reactor directly heated by electric current

• Alicja Schlange,
• Antonio Rodolfo dos Santos,
• Ulrich Kunz and
• Thomas Turek

Beilstein J. Org. Chem. 2011, 7, 1412–1420, doi:10.3762/bjoc.7.165

• preparation in a flow reactor which could be used at a large scale. Keywords: carbon nanotubes; continuous catalyst synthesis; direct electrical heating; flow reactors; fuel cell platinum catalyst; Introduction Batch processes represent the state of the art in catalyst preparation. One reason for employing

• results. Most of the work is concerned with the precipitation of hydroxides, oxides or other hardly soluble metal compounds [12]. Platinum nanoparticles supported on conductive carbon materials such as carbon black or carbon nanotubes (CNTs) are commonly used as oxygen reduction reaction (ORR) catalysts

• supported Pt catalyst and its electrochemical activities [16][17][18]. To overcome this challenge, further research on electrocatalyst development is a necessity. Generally, high metal content, small platinum cluster size, and uniform particle distribution over the support material are needed to enhance the

Scaling up of continuous-flow, microwave-assisted, organic reactions by varying the size of Pd-functionalized catalytic monoliths

• Ping He,
• Stephen J. Haswell,
• Paul D. I. Fletcher,
• Stephen M. Kelly and
• Andrew Mansfield

Beilstein J. Org. Chem. 2011, 7, 1150–1157, doi:10.3762/bjoc.7.133

• sealed within the Teflon® tube to form a flow Pd-monolith reactor system. Sample characterization Scanning electron microscopy (SEM) images were obtained by means of a Cambridge S360 scanning electron microscope operated at 20 kV. Each sample was sputter coated with a thin layer of gold–platinum

A practical microreactor for electrochemistry in flow

• Kevin Watts,
• William Gattrell and
• Thomas Wirth

Beilstein J. Org. Chem. 2011, 7, 1108–1114, doi:10.3762/bjoc.7.127

• without any added electrolyte [4][5]. Atobe et al. constructed a thin layer flow cell from platinum and/or glassy carbon plates (3 × 3 cm), separated by adhesive tape (80 µm), with a space left in between to act as the channel, and the devices were sealed with epoxy resin [6]. They reported the self

• platinum electrodes with a surface area of 45 mm2 were positioned with an inter-electrode gap of either 160 µm or 320 µm, and C–C bond forming reactions based on the electro-reductive coupling of activated olefins and benzyl bromide derivatives were reported. The best result obtained was a 98% formation of

• the continuous synthesis of diaryliodonium compounds. A microflow electrochemical reactor made out of two aluminium bodies (50 mm diameter, 25 mm height) was manufactured. The electrodes are constructed of two PTFE plates (35 mm diameter, 4 mm height) onto which 0.1 mm platinum foil electrodes [16

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

• and reductive eliminations). Therefore, platinum(II) and particularly gold(I) or (III) complexes tend to activate alkynes, alkenes or allenes in a highly chemoselective manner; activation that opens interesting reaction pathways that usually involve carbocationic intermediates. Also very important is

• cycloadditions involving zwitterionic intermediates similar to I have also been developed with other transition metal catalysts such as tungsten, rhodium or platinum [32][33][34][35]. In particular, important developments were recently achieved with platinum catalysts [36][37], including the first

Asymmetric Au-catalyzed cycloisomerization of 1,6-enynes: An entry to bicyclo[4.1.0]heptene

• Alexandre Pradal,
• Chung-Meng Chao,
• Patrick Y. Toullec and
• Véronique Michelet

Beilstein J. Org. Chem. 2011, 7, 1021–1029, doi:10.3762/bjoc.7.116

• carbophilic complexes such as platinum or gold [16][17][18][19][20][21][22] that led to the formation of complex bicyclic and tricyclic compounds [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]. The first asymmetric version was described by Shibata’s group in 2005 in the presence of a

• chiral iridium catalyst [41] (Scheme 1, reaction 2). We and others recently pursued the improvement and development of this enantioselective process, by employing platinum [42][43][44], rhodium [45] or gold [46][47][48] complexes. Following our previous work with chiral gold catalysts [46], we report a

• % isolated yield respectively) resulting from 5-exo- and 6-endo cycloisomerization reactions [20][66]. Thus, the gold catalytic system cannot compete with the results obtained for the cyclizations of nitrogen-tethered enynes in the presence of iridium, platinum or rhodium catalysts [41][42][43][44][45]. The

Synthesis of novel 5-alkyl/aryl/heteroaryl substituted diethyl 3,4-dihydro-2H-pyrrole-4,4-dicarboxylates by aziridine ring expansion of 2-[(aziridin-1-yl)-1-alkyl/aryl/heteroaryl-methylene]malonic acid diethyl esters

• Satish S. More,
• T. Krishna Mohan,
• Y. Sateesh Kumar,
• U. K. Syam Kumar and
• Navin B. Patel

Beilstein J. Org. Chem. 2011, 7, 831–838, doi:10.3762/bjoc.7.95

• quantitative yields, either by reduction with sodium borohydride, or by catalytic hydrogenation using platinum on carbon [33][34]. The pyrrolines can be aromatized either by a two step procedure (i) NBS bromination and (ii) dehydrohalogenation in basic medium [35][36][37], or by dehydrogenation with Pd/C [38

High chemoselectivity in the phenol synthesis

• Matthias Rudolph,
• Melissa Q. McCreery,
• Wolfgang Frey and
• A. Stephen K. Hashmi

Beilstein J. Org. Chem. 2011, 7, 794–801, doi:10.3762/bjoc.7.90

• dinuclear gold(I) complex 36 [44] gave the same result (Figure 3). When the catalyst was changed to platinum(II) chloride in acetone, a complex mixture of inseparable products was obtained. Since the two diastereoisomers 28a and 28b with the propargylic stereocenters were separable, we investigated the gold

Gold-catalyzed heterocyclizations in alkynyl- and allenyl-β-lactams

• Benito Alcaide and
• Pedro Almendros

Beilstein J. Org. Chem. 2011, 7, 622–630, doi:10.3762/bjoc.7.73

• -(2-alkynylphenyl)-β-lactams 18 has been accomplished (Scheme 10). Platinum was the metal of choice, gold salts being less effective [51]. This cycloisomerization can be viewed as a net intramolecular insertion of one end of the alkyne into the lactam amide bond with concurrent migration of the

A gold-catalyzed alkyne-diol cycloisomerization for the synthesis of oxygenated 5,5-spiroketals

• Sami F. Tlais and
• Gregory B. Dudley

Beilstein J. Org. Chem. 2011, 7, 570–577, doi:10.3762/bjoc.7.66

• selectivity using the Utimoto conditions to prepare 6,6-spiroketals. Therefore, he suggested the preferred use of Ziese’s dimer, a platinum catalyst (Scheme 3, Reaction 2), for such cyclizations [9]. In an unrelated study that also bears on the current work, Aponick and co-workers described a gold-catalyzed

One-pot gold-catalyzed synthesis of 3-silylethynyl indoles from unprotected o-alkynylanilines

• Jonathan P. Brand,
• Clara Chevalley and
• Jérôme Waser

Beilstein J. Org. Chem. 2011, 7, 565–569, doi:10.3762/bjoc.7.65

• carbonyl groups, but using platinum catalysts [25][26][27][28]. To date, there are no gold- or platinum-catalyzed methods for the introduction of acetylenes as electrophiles. However, Cacchi developed a palladium-catalyzed domino sequence including cyclization of o-alkynyltrifluoroacetanilides and

Palladium-catalyzed formation of oxazolidinones from biscarbamates: a mechanistic study

• Benan Kilbas and
• Metin Balci

Beilstein J. Org. Chem. 2011, 7, 246–253, doi:10.3762/bjoc.7.33

• complex rings and open chain systems containing diverse functionalities. It has been reported that the complexation takes place exclusively anti to the leaving group (Figure 1) [3][4][5][6]. On the other hand, Kurosawa et al. [7] and Greenberg et al. [8] reported that the palladium(0)–olefin and platinum

• (0)–olefin complexes add to 5-(methoxycarbonyl)-2-cyclohexenyl chloride and bromide from the syn-side of the leaving group and that the leaving group is capable of coordinating the metal to give the corresponding (η3-allyl)–palladium or –platinum complexes. In order to determine from which side the

Synthesis and self-assembly of 1-deoxyglucose derivatives as low molecular weight organogelators

• Guijun Wang,
• Hao Yang,
• Sherwin Cheuk and
• Sherman Coleman

Beilstein J. Org. Chem. 2011, 7, 234–242, doi:10.3762/bjoc.7.31

• program used to acquire and store the photos was Corel Photo-Paint 7. Scanning electron microscopy. A piece of the gel was deposited on an aluminum sample holder and allowed to dry in a desiccator. The dried gel sample was coated with a thin layer of platinum (~100–150 Å) by a Denton Vacuum (model Desk II

Identification and synthesis of impurities formed during sertindole preparation

• I. V. Sunil Kumar,
• G. S. R. Anjaneyulu and
• V. Hima Bindu

Beilstein J. Org. Chem. 2011, 7, 29–33, doi:10.3762/bjoc.7.5

• hydrochloride monohydrate (14) under acidic conditions affords 5-chloro-1-(4-fluorophenyl)-3-(1,2,3,6-tetrahydropyridin-4-yl)-1H-indole hydrochloride (15). Reduction of 15 in the presence of platinum oxide yields 5-chloro-1-(4-fluorophenyl)-3-(4-piperdinyl)-1H-indole (9) which on condensation with 1-(2

• platinum catalyzed reduction of indole 15 is a critical reaction, whilst a prolonged reaction time leads to dehalogenated product 2, termination without complete reduction leads to indole 9 contaminated with 15. This contaminated material upon condensation with imidazolidinone 16 results in sertindole (1

• )-impurity 21 (Scheme 4). The catalytic hydrogenation of indole 19 proved to be a difficult reaction as significant formation of the dehalogenated products was observed, repeated recrystallization from MeOH afforded pure indole 20. Since dehalogenation was observed during the platinum oxide reduction of the

Miniemulsion polymerization as a versatile tool for the synthesis of functionalized polymers

• Daniel Crespy and
• Katharina Landfester

Beilstein J. Org. Chem. 2010, 6, 1132–1148, doi:10.3762/bjoc.6.130

• copolymerized with styrene to yield functionalized particles [34][35] and their uptake by cells was studied [34]. In general, with increased functional groups, an increase in the uptake into cells could be observed. Copolymer particles of styrene and acrylic acid were used to encapsulate a platinum(II) complex

Redox-active tetrathiafulvalene and dithiolene compounds derived from allylic 1,4-diol rearrangement products of disubstituted 1,3-dithiole derivatives

• Filipe Vilela,
• Peter J. Skabara,
• Christopher R. Mason,
• Thomas D. J. Westgate,
• Asun Luquin,
• Simon J. Coles and
• Michael B. Hursthouse

Beilstein J. Org. Chem. 2010, 6, 1002–1014, doi:10.3762/bjoc.6.113

• anhydrous CH2Cl2 with 0.1 M tetrabutylammonium hexafluorophosphate as the supporting electrolyte. Glassy carbon, platinum wire, and Ag/AgCl electrodes were used as the working, counter and reference electrodes, respectively. The cyclic voltammograms are shown in Figure 7, and the potential values of the

• voltammetric analyser with iR compensation, in anhydrous dichloromethane, with aqueous Ag/AgCl as the reference electrode and platinum wire and gold disk as the counter and working electrodes, respectively. The solution was degassed (N2) and contained the substrate in a concentration of ca. 10−3 M together

Synthesis, electronic properties and self-assembly on Au{111} of thiolated (oligo)phenothiazines

• Adam W. Franz,
• Svetlana Stoycheva,
• Michael Himmelhaus and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2010, 6, No. 72, doi:10.3762/bjoc.6.72

• mm platinum disk, the counter-electrode was a platinum wire, and the reference electrode was an Ag/AgCl electrode. The potentials were corrected to the internal standard of Fc/Fc+ in CH2Cl2 (E00/+1 = 450 mV) [61]. 7-Bromo-10,10′,10″,10′″-tetrahexyl-10H,10′H,10″H,10′″H-3,3′:7′,3″:7″,3

Functional properties of metallomesogens modulated by molecular and supramolecular exotic arrangements

• Alessandra Crispini,
• Mauro Ghedini and
• Daniela Pucci

Beilstein J. Org. Chem. 2009, 5, No. 54, doi:10.3762/bjoc.5.54

• ligand extensively used in the synthesis of cyclometallated iridium(III) and platinum(II) derivatives [46][47] but whose reactivity towards Pd(II) centres is unexplored. This kind of ligand has been functionalised with a chiral group such as a cholesteryl ester unit, introduced as terminal substituent in

• soft materials with non-conventional structures. Platinum(II) and Zinc(II) For the less explored Pt(II) and Zn(II) metal centres versatile 2,2′-bipyridines have been selected since they are well-known building blocks for the formation of inorganic functional nanomaterials [51]. The complexation of non

A convenient method for preparing rigid-core ionic liquid crystals

• Julien Fouchet,
• Laurent Douce,
• Benoît Heinrich,
• Richard Welter and
• Alain Louati

Beilstein J. Org. Chem. 2009, 5, No. 51, doi:10.3762/bjoc.5.51

• containing 0.1 M NBu4PF6 as supporting electrolyte at a platinum working electrode. The peak potentials are given vs. a SCE. Representative cyclic voltammograms of 1a are shown in Figure 10. The anodic portion of the voltage scan displays two oxidation steps having peak potentials of 0.42 V and 0.68 V, and

Synthesis of mesogenic phthalocyanine-C₆₀ donor–acceptor dyads designed for molecular heterojunction photovoltaic devices

• Yves Henri Geerts,
• Olivier Debever,
• Claire Amato and
• Sergey Sergeyev

Beilstein J. Org. Chem. 2009, 5, No. 49, doi:10.3762/bjoc.5.49

• as a working electrode. A spiral platinum wire was employed as counter electrode and an Ag/AgCl/KCl(sat) used as reference electrode was connected to the cell solution via a salt bridge containing a saturated aqueous KCl solution. The Ag/AgCl electrode was checked against the ferrocene/ferrocinium

New diarylmethanofullerene derivatives and their properties for organic thin- film solar cells

• Daisuke Sukeguchi,
• Surya Prakash Singh,
• Mamidi Ramesh Reddy,
• Hideyuki Yoshiyama,
• Rakesh A. Afre,
• Yasuhiko Hayashi,
• Hiroki Inukai,
• Tetsuo Soga,
• Shuichi Nakamura,
• Norio Shibata and
• Takeshi Toru

Beilstein J. Org. Chem. 2009, 5, No. 7, doi:10.3762/bjoc.5.7

• ) using a platinum electrode and tetrabutylammonium hexafluorophosphate as the supporting electrolyte in THF. Reduction potentials are listed in Table 1. The obtained cyclic voltammetry data were reversible. The first reduction potentials depend on the electron-donating nature of the substituents, in

Facile synthesis of two diastereomeric indolizidines corresponding to the postulated structure of alkaloid 5,9E- 259B from a Bufonid toad (Melanophryniscus)

• Angela Nelson,
• H. Martin Garraffo,
• Thomas F. Spande,
• John W. Daly and
• Paul J. Stevenson

Beilstein J. Org. Chem. 2008, 4, No. 6, doi:10.1186/1860-5397-4-6

• at about δ 3.27 ppm. Reduction of the alkene 5 with hydrogen and a heterogeneous catalyst gave the product indolizidines as a mixture of C8 diastereoisomers. When platinum oxide was used as catalyst, a 1:1 mixture of diastereoisomers resulted, but when platinum-on-carbon was employed, a 4:1 mixture

Analogues of amphibian alkaloids: total synthesis of (5R,8S,8aS)-(−)-8-methyl- 5-pentyloctahydroindolizine (8-epi-indolizidine 209B) and [(1S,4R,9aS)-(−)-4-pentyloctahydro- 2H-quinolizin- 1-yl]methanol

• Joseph P. Michael,
• Claudia Accone,
• Charles B. de Koning and
• Christiaan W. van der Westhuyzen

Beilstein J. Org. Chem. 2008, 4, No. 5, doi:10.1186/1860-5397-4-5

• approach of the reductant towards the more remote face of the double bond. Gratifyingly, hydrogenation of intermediate 39 over platinum oxide catalyst in ethanol at a pressure of five atmospheres produced the quinolizidine (−)-40 as a single diastereomer in 97% yield. The diastereoselectivity is manifestly

Effect of transannular interaction on the redox- potentials in a series of bicyclic quinones

• Grigoriy Sereda,
• Jesse Van Heukelom,
• Miles Koppang,
• Sudha Ramreddy and
• Nicole Collins

Beilstein J. Org. Chem. 2006, 2, No. 26, doi:10.1186/1860-5397-2-26

• dissolved in 25 mL of 0.1 M (n-C4H9)4N+BF4− (electrochemical grade from Southwestern Analytical) in acetonitrile (HPLC grade) and placed in a three electrode electrochemical cell. The working electrode was a BAS platinum electrode (Bioanalytical Systems, West Lafayette, IN, area ca. 0.02 cm2), the auxiliary

Multiple hydride reduction pathways in isoflavonoids

• Auli K. Salakka,
• Tuija H. Jokela and
• Kristiina Wähälä

Beilstein J. Org. Chem. 2006, 2, No. 16, doi:10.1186/1860-5397-2-16

• starting materials but overall yields in these multistep procedures tend to be low, and free hydroxy groups are not compatible. Another strategy involves the hydrogenation of isoflavones using a palladium or platinum catalyst but mixtures of reduction products are often formed [9][10]. Certain hydride