From betaines to anionic N-heterocyclic carbenes. Borane, gold, rhodium, and nickel complexes starting from an imidazoliumphenolate and its carbene tautomer

• Ming Liu,
• Jan C. Namyslo,
• Martin Nieger,
• Mika Polamo and
• Andreas Schmidt

Beilstein J. Org. Chem. 2016, 12, 2673–2681, doi:10.3762/bjoc.12.264

• .12.264 Abstract The mesomeric betaine imidazolium-1-ylphenolate forms a borane adduct with tris(pentafluorophenyl)borane by coordination with the phenolate oxygen, whereas its NHC tautomer 1-(2-phenol)imidazol-2-ylidene reacts with (triphenylphosphine)gold(I) chloride to give the cationic NHC complex [Au

• adduct displays two different conformers in the unit cell which differ inter alia in the torsion angles around the Nimidazole–Cphenol bonds [−53.32(16)° vs 114.12(13)°] and the Cphenyl–O bonds [49.43(17)° vs −15.29(18)°] (Figure 2). A gold complex of the N-heterocyclic carbene tautomer 6B can be obtained

• on reaction with (triphenylphosphine)gold(I) chloride in boiling anhydrous THF under a nitrogen atmosphere, under which conditions the colorless gold complex [Au(6B)2][Cl] (9) is formed in 60% yield (Scheme 1). The protons of the OH resonate at δ = 10.34 ppm in DMSO-d6, and the 13C NMR chemical shift

Efficient mechanochemical synthesis of regioselective persubstituted cyclodextrins

• Laszlo Jicsinszky,
• Marina Caporaso,
• Katia Martina,
• Emanuela Calcio Gaudino and
• Giancarlo Cravotto

Beilstein J. Org. Chem. 2016, 12, 2364–2371, doi:10.3762/bjoc.12.230

• well as solvent impurities increase synthesis and purification costs and time. Selectively per-6-thiolated CDs are also used in gold nanoparticle chemistry, particularly in electrochemical sensors [17]. Thiourea (TU) is one of the best precursors of those CDs because as the halogen is exchanged to the

Enduracididine, a rare amino acid component of peptide antibiotics: Natural products and synthesis

• Darcy J. Atkinson,
• Briar J. Naysmith,
• Daniel P. Furkert and
• Margaret A. Brimble

Beilstein J. Org. Chem. 2016, 12, 2325–2342, doi:10.3762/bjoc.12.226

• reaction site and poor compatibility of the cyclic guanidine motif with Lewis acids. Initial attempts to glycosylate cyclic guanidine 91 using an array of donors under Lewis acidic or basic conditions failed to provide access to N-mannosylguanidine 92 (Scheme 18). However, gold(I) mediated [71] N

Tunable microwave-assisted method for the solvent-free and catalyst-free peracetylation of natural products

• Manuela Oliverio,
• Paola Costanzo,
• Monica Nardi,
• Carla Calandruccio,
• Raffaele Salerno and
• Antonio Procopio

Beilstein J. Org. Chem. 2016, 12, 2222–2233, doi:10.3762/bjoc.12.214

• carrier gas) and by an DSQ II mass detector. Chromatography was performed using a Thermo Scientific Dionex Ultimate 3000 RS, injecting directly onto a Thermo Scientific Hypersil Gold C18 column (50 × 2.1 mm, 1.9 µm particle size), equilibrated in 95% solvent A (0.1% aqueous solution of formic acid), 5

Thiophene-forming one-pot synthesis of three thienyl-bridged oligophenothiazines and their electronic properties

• Dominik Urselmann,
• Konstantin Deilhof,
• Bernhard Mayer and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2016, 12, 2055–2064, doi:10.3762/bjoc.12.194

• to form self-assembled monolayers on gold [69][70][71] as well as on zinc and iron oxide surfaces [72]. Conceptually, thienyl-bridged oligophenothiazines can be considered as a novel type of structurally well-defined electron-rich oligophenothiazine–thiophene hybrids (Figure 1). Thereby, the strong

Varioloid A, a new indolyl-6,10b-dihydro-5aH-[1]benzofuro[2,3-b]indole derivative from the marine alga-derived endophytic fungus Paecilomyces variotii EN-291

• Peng Zhang,
• Xiao-Ming Li,
• Xin-Xin Mao,
• Attila Mándi,
• Tibor Kurtán and
• Bin-Gui Wang

Beilstein J. Org. Chem. 2016, 12, 2012–2018, doi:10.3762/bjoc.12.188

• an Optical Activity AA-55 polarimeter. UV spectra were measured by a Lengguang Gold S54 photometer. ECD data were collected using JASCO J-715 or J-810 spectropolarimeters. NMR data were recorded on a Bruker Avance 500 MHz spectrometer with TMS as internal standard. Low and high resolution ESI-mass

Organic chemistry meets polymers, nanoscience, therapeutics and diagnostics

• Vincent M. Rotello

Beilstein J. Org. Chem. 2016, 12, 1638–1646, doi:10.3762/bjoc.12.161

• when we demonstrated very efficient DNA transfection (i.e., gene delivery) using gold nanoparticles [55]. In later work we improved on our gene delivery vehicles [56], demonstrated the delivery of siRNA [57] and enzymes [58] using nanoparticle assemblies. All of these systems (as well as essentially

• organs – after shooting them into mice [74]. More recently, we bought an inductively coupled plasma (ICP) mass spectrometer that allows us to quantify elements. We have used ICP together with LDI to determine the stability of quantum dots [75] and gold nanoparticles in cells [76]. Once again, a tribute

• breakthrough occurred at the Fall 2006 ACS meeting where the ever-charming Uwe Bunz and I had the simultaneous inspiration of using Uwe's highly fluorescent poly(phenylene ethynelene) "molecular wire" polymers as transducers. These polymers would be quenched by the gold core of the nanoparticles while bound

Beta-hydroxyphosphonate ribonucleoside analogues derived from 4-substituted-1,2,3-triazoles as IMP/GMP mimics: synthesis and biological evaluation

• Tai Nguyen Van,
• Audrey Hospital,
• Corinne Lionne,
• Lars P. Jordheim,
• Charles Dumontet,
• Christian Périgaud,
• Laurent Chaloin and
• Suzanne Peyrottes

Beilstein J. Org. Chem. 2016, 12, 1476–1486, doi:10.3762/bjoc.12.144

• which they block the enzyme activity. For this purpose, a SAR study was carried out by molecular docking. Attempts to make a direct correlation between the inhibitory activity and the gold-computed docking score (Table 2) were unsuccessful. Indeed, all compounds exhibited a similar score with a value

Stereodynamic tetrahydrobiisoindole “NU-BIPHEP(O)”s: functionalization, rotational barriers and non-covalent interactions

• Golo Storch,
• Sebastian Pallmann,
• Frank Rominger and
• Oliver Trapp

Beilstein J. Org. Chem. 2016, 12, 1453–1458, doi:10.3762/bjoc.12.141

• ][6], palladium [7][8], platinum [9][10] and gold [11][12][13] in combination with chiral co-ligands or counter ions that are used after alignment of the ligand’s axial chirality. One major advantage of stereodynamic ligands is that there is no need for separate preparation of one ligand enantiomer as

3,6-Carbazole vs 2,7-carbazole: A comparative study of hole-transporting polymeric materials for inorganic–organic hybrid perovskite solar cells

• Wei Li,
• Munechika Otsuka,
• Takehito Kato,
• Yang Wang,
• Takehiko Mori and
• Tsuyoshi Michinobu

Beilstein J. Org. Chem. 2016, 12, 1401–1409, doi:10.3762/bjoc.12.134

• transporting materials were deposited by spin-coating a solution of P3HT, 3,6-Cbz-EDOT, or 2,7-Cbz-EDOT in chlorobenzene (7.82 g L−1). All hole-transporting layers were dried in the dark. The thickness of the hole-transporting layers was about 30 nm. Finally, gold (80 nm) was thermally evaporated on the top of

Synthesis of 2-substituted tetraphenylenes via transition-metal-catalyzed derivatization of tetraphenylene

• Shulei Pan,
• Hang Jiang,
• Yanghui Zhang,
• Yu Zhang and
• Dushen Chen

Beilstein J. Org. Chem. 2016, 12, 1302–1308, doi:10.3762/bjoc.12.122

• acetoxylation a highly interesting reaction. The Sanford and Wang group, respectively, developed a highly efficient palladium and gold-catalyzed direct acetoxylation of arenes with iodobenzene diacetate [48][49]. Based on these excellent works, we surveyed the reaction conditions for the acetoxylation of

• halogenation of tetraphenylene attracted our attention. The Wang group reported an efficient and mild protocol for a gold-catalyzed direct C–H halogenation of arenes with N-halosuccinimides [56][57]. Therefore, we initially investigated the chlorination of tetraphenylene by subjecting it to Wang’s conditions

Synthesis of highly functionalized 2,2'-bipyridines by cyclocondensation of β-ketoenamides – scope and limitations

• Paul Hommes and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2016, 12, 1170–1177, doi:10.3762/bjoc.12.112

• amide and but-3-yn-2-one (as an equivalent of 3-oxobutanal) using methanol as solvent in a sealed tube [29]. Disappointingly, the maximum yield for compound 3h was only 22%. Many attempts to improve this result – including gold catalysis [30] – either led to lower yields or no conversion at all [31]. We

Chiral cyclopentadienylruthenium sulfoxide catalysts for asymmetric redox bicycloisomerization

• Barry M. Trost,
• Michael C. Ryan and
• Meera Rao

Beilstein J. Org. Chem. 2016, 12, 1136–1152, doi:10.3762/bjoc.12.110

• rhodium first undergoes oxidative cyclization with the vinylcyclopropane prior to alkyne insertion. The asymmetric enyne cycloisomerization reaction has been shown to be instrumental in the construction of medicinal chemistry targets. For example, the Fürstner group realized that gold catalysis would be

• bicycloisomerization reaction (vide infra). Unlike ruthenium and palladium enyne cycloisomerization, which operate via metallacycle formation or hydrometallation, gold acts as a π-acid, increasing the electrophilicity of the alkyne by η2 coordination. The pendant alkene cyclizes on the alkyne, and the resulting

• tertiary carbocation is trapped by a gold carbenoid intermediate to form the fused cyclopropane. While there had been reports of utilizing chiral ruthenium complexes for asymmetric catalysis prior to our studies [30][31][32][33][34][35][36][37][38][39][40], there had previously been no reported examples of

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

• cyclopropene 97 reacted [93][94] to form the same products as the hydrazone 96 did directly when heated to 140 °C. Gold The work by the May group was soon followed by gold-promoted carbene/alkyne cascades. These cascades rely on Zhang’s discovery that the use of pyridine N-oxides allow for the formation of

• gold ketocarbenes 104 from alkynes (Scheme 22) [95]. Those carbenes are then capable of further transformations, including C–H bond insertion and the reaction with other alkynes. Notably, this approach avoids the use of unstable diazo compounds. The Zhang group also demonstrated that the gold carbenes

• generated from alkynes can produce bridged bicycles from C–H bond insertion (Scheme 23) [96]. This was first implemented by transannular insertion via 107 to give the bicyclo[3.2.1]octane 108. The diastereoselectivity of the process was not reported. Again, dual gold catalysts were used with a pyridinium

Syntheses of dibenzo[d,d']benzo[2,1-b:3,4-b']difuran derivatives and their application to organic field-effect transistors

• Minh Anh Truong and
• Koji Nakano

Beilstein J. Org. Chem. 2016, 12, 805–812, doi:10.3762/bjoc.12.79

• substrates were used to evaluate the effect of the substrate structure on the device performance. The gold source/drain electrodes were deposited on the thin films. The channel width and length were 500 μm and 50 μm, respectively. Both syn-DBBDF- and syn-DNBDF-based OFETs demonstrated typical p-type

Gold-catalyzed direct alkynylation of tryptophan in peptides using TIPS-EBX

• Gergely L. Tolnai,
• Jonathan P. Brand and
• Jerome Waser

Beilstein J. Org. Chem. 2016, 12, 745–749, doi:10.3762/bjoc.12.74

• is highly attractive, but the use of a carbon linker is usually required. Herein, we report the gold-catalyzed direct alkynylation of tryptophan in peptides using the hypervalent iodine reagent TIPS-EBX (1-[(triisopropylsilyl)ethynyl]-1,2-benziodoxol-3(1H)-one). The reaction proceeded in 50–78% yield

• under mild conditions and could be applied to peptides containing other nucleophilic and aromatic amino acids, such as serine, phenylalanine or tyrosine. Keywords: alkynes; C–H functionalization; gold catalysis; hypervalent iodine; peptides; Introduction Alkynes have always been important building

• the modification of biomolecules without the need for non-natural amino acids. However, the multiple functional groups present in biomolecules make such a process highly challenging. Based on our previous work on the alkynylation of indoles using TIPS-EBX (1a) and a gold catalysis [37][38], we

From steroids to aqueous supramolecular chemistry: an autobiographical career review

• Bruce C. Gibb

Beilstein J. Org. Chem. 2016, 12, 684–701, doi:10.3762/bjoc.12.69

• departments in the US carry out faculty searches, I now appreciate that I had struck gold. I never saw the letters that John, Jim and Neville wrote, but they must have said some nice things. And so I went through the interview process at the University of New Orleans and did well enough to get an offer. I had

The aminoindanol core as a key scaffold in bifunctional organocatalysts

• Isaac G. Sonsona,
• Eugenia Marqués-López and
• Raquel P. Herrera

Beilstein J. Org. Chem. 2016, 12, 505–523, doi:10.3762/bjoc.12.50

• formation of a hydrogen bond with the indolic proton. In the second catalytic cycle, the intermediates 9 would react to give an intramolecular Friedel–Crafts alkylation. The alkyne moiety of 9 would be previously activated by a gold complex in the presence of p-toluenesulfonic acid hydrate as the additive

• Friedel–Crafts alkylation, which involves the hydrogen-bonding catalyst ent-6 and gold catalysis and leads to the tetracyclic indoles 8. One-pot multisequence process that allows the synthesis of interesting compounds 14. The pharmacologically active compound 15 can be obtained from the properly

Self and directed assembly: people and molecules

• Tony D. James

Beilstein J. Org. Chem. 2016, 12, 391–405, doi:10.3762/bjoc.12.42

• mechanism to report saccharide binding (Figure 4). Sensei (Seiji Shinkai) then gave me my next and most important academic lesson – if you discover “gold” in one area of research you should keep on digging in that area – the hope is that you will discover a “seam of gold” leading to even more research

• achievements. This result, as far as my career goes was a Eureka moment, for which I count myself very lucky, this very simple discovery was the start of a very big “seam of gold” that has continued to fuel my research to the present day [19][20][21][22][23][24][25][26][27]. After, we discovered this simple

Optimized methods for preparation of 6^I-(ω-sulfanyl-alkylene-sulfanyl)-β-cyclodextrin derivatives

• Eva Bednářová,
• Simona Hybelbauerová and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2016, 12, 349–352, doi:10.3762/bjoc.12.38

• disulfides are derivatives usable for well-defined covalent attachment of cyclodextrin to gold or polydopamine-coated solid surfaces. Keywords: cyclodextrins; disulfides; monosubstituted derivatives; thiols; Introduction Cyclodextrins (CDs) [1], cyclic oligomers of α-D-glucopyranose, are used for their

• -cyclodextrins (β-CD-S-X-SH) – which can be attached to a gold surface [9][10] or a polydopamine-coated surface [11]. It has been already described that the surface coverage of self-assembled monolayers of CD derivatives on gold depends substantially on the linker between the sulfanyl group and the CD

• the CD and the sulfanyl group. These derivatives are needed for two projects which both will study the influence of the linker length on the properties of the whole system. The first project will study the sensitivity of quartz crystal microbalances with a CD-modified gold sensor [14]; the second will

Study on the synthesis of the cyclopenta[f]indole core of raputindole A

• Nils Marsch,
• Mario Kock and
• Thomas Lindel

Beilstein J. Org. Chem. 2016, 12, 334–342, doi:10.3762/bjoc.12.36

• which provided the hydrogenated tricyclic cyclopenta[f]indole core system in high yield. Keywords: gold-catalyzed reactions; heterocycles; indole alkaloids; natural products; synthesis; Introduction The raputindoles (1, raputindole A, Figure 1) from the rutaceous tree Raputia simulans Kallunki

• indoline and changing the N-protecting group significantly improved the yield for the cyclocitral adduct, but this still does not appear to be sufficient for a strategy towards raputindole A (1). Cyclization of propargylacetates. Key progress came when applying platinum and gold chemistry to

Scope and limitations of the dual-gold-catalysed hydrophenoxylation of alkynes

• Adrián Gómez-Suárez,
• Yoshihiro Oonishi,
• Anthony R. Martin and
• Steven P. Nolan

Beilstein J. Org. Chem. 2016, 12, 172–178, doi:10.3762/bjoc.12.19

• /bjoc.12.19 Abstract Due to the synthetic advantages presented by the dual-gold-catalysed hydrophenoxylation of alkynes, a thorough study of this reaction was carried out in order to fully define the scope and limitations of the methodology. The protocol tolerates a wide range of functional groups, such

• in unsymmetrical alkynes can help to achieve high regioselectivity in the hydrophenoxylation. Keywords: cooperative catalysis; gold catalysis; hydrophenoxylation; N-heterocyclic carbene; vinyl ethers; Introduction During the last 30 years, N-heterocyclic carbenes (NHCs) have evolved from mere

• metal and main-group chemistry [10][11][12][13]. We have been interested in exploring the use of NHC ligands in transition metal complexes for the development of highly active and well-defined catalysts. One of our main interests during the last decade has been to study the use of gold–NHC species as

Copper-catalyzed intermolecular oxyamination of olefins using carboxylic acids and O-benzoylhydroxylamines

• Brett N. Hemric and
• Qiu Wang

Beilstein J. Org. Chem. 2016, 12, 22–28, doi:10.3762/bjoc.12.4

• olefins with a tethered amino or oxygen functionality has been achieved for the construction of a variety of 1,2-oxyamino products, using palladium [19][20], platinum [21], gold [22], copper [23][24][25][26], free-radical initiators [27][28][29], hypervalent iodine [30], and electrochemical oxidation [31

Pyridylidene ligand facilitates gold-catalyzed oxidative C–H arylation of heterocycles

• Kazuhiro Hata,
• Hideto Ito,
• Yasutomo Segawa and
• Kenichiro Itami

Beilstein J. Org. Chem. 2015, 11, 2737–2746, doi:10.3762/bjoc.11.295

• University, Chikusa, Nagoya 464-8602, Japan 10.3762/bjoc.11.295 Abstract Triaryl-2-pyridylidene effectively facilitates the gold-catalyzed oxidative C–H arylation of heteroarenes with arylsilanes as a unique electron-donating ligand on gold. The employment of the 2-pyridylidene ligand, which is one of the

• strongest electron-donating N-heterocyclic carbenes, resulted in the rate acceleration of the C–H arylation reaction of heterocycles over conventional ligands such as triphenylphosphine and a classical N-heterocyclic carbene. In situ observation and isolation of the 2-pyridylidene-gold(III) species, as well

• as a DFT study, indicated unusual stability of gold(III) species stabilized by strong electron donation from the 2-pyridylidene ligand. Thus, the gold(I)-to-gold(III) oxidation process is thought to be facilitated by the highly electron-donating 2-pyridylidene ligand. Keywords: carbene ligand; C–H

Learning from the unexpected in life and DNA self-assembly

• Jennifer M. Heemstra

Beilstein J. Org. Chem. 2015, 11, 2713–2720, doi:10.3762/bjoc.11.292

• were specifically drawn to the enzyme-linked immunosorbent assay (ELISA) that is the current gold standard in this field. As shown in Figure 3, we constructed our enzyme-linked assay by immobilizing one fragment of the split aptamer on the surface of a microplate, then adding the test sample along with