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

• insertion to form the caged cyclopropyl ring system in 120. Alternatively, the proximity of the methylene of the benzyl ether in 123 allows for a benzylic C–H insertion to generate the bridged polycycle 124. Tungsten Iwasawa demonstrated a similar strategy for bridged-polycycle synthesis using a tungsten

• catalyst (Scheme 27) [102][103]. Again, the formation of a 1,3-dipole (see 127) allows for a cycloaddition, though this example is intermolecular in nature. One of the ethereal ethyl groups in 128 is consequently poised for C–H bond insertion by the tungsten carbene to give 129 as a single diastereomer

• . Platinum cascades. Tungsten cascade. Acknowledgements The authors are grateful to the Welch Foundation (grant E-1744) and the NSF (grant CHE-1352439) for financial support. J-L.S. is grateful for support by CBIP (UH) and the Studying Abroad Scholarship of Taiwan.

Preparation of Pickering emulsions through interfacial adsorption by soft cyclodextrin nanogels

• Shintaro Kawano,
• Toshiyuki Kida,
• Mitsuru Akashi,
• Hirofumi Sato,
• Motohiro Shizuma and
• Daisuke Ono

Beilstein J. Org. Chem. 2015, 11, 2355–2364, doi:10.3762/bjoc.11.257

• kV. Each Pickering emulsion sample was dried directly onto carbon tape and allowed to dry overnight before being sputter-coated with a thin layer of tungsten. Transmittance electron microscopy (TEM) studies were performed using a JEOL JEM-2100 operating at a voltage of 50 kV in order to clarify the

Thermal properties of ruthenium alkylidene-polymerized dicyclopentadiene

• Yuval Vidavsky,
• Yotam Navon,
• Yakov Ginzburg,
• Moshe Gottlieb and
• N. Gabriel Lemcoff

Beilstein J. Org. Chem. 2015, 11, 1469–1474, doi:10.3762/bjoc.11.159

• be disrupted first to afford a linear polymer, followed by the ring opening of the less reactive cyclopentene double bond to effectively cross-link the chains (Scheme 1). Notably, with tungsten and molybdenum initiators the linear polymer may be isolated [20][21]; unlike the case with ruthenium

The Shono-type electroorganic oxidation of unfunctionalised amides. Carbon–carbon bond formation via electrogenerated N-acyliminium ions

• Alan M. Jones and
• Craig E. Banks

Beilstein J. Org. Chem. 2014, 10, 3056–3072, doi:10.3762/bjoc.10.323

• is attached either to the carbamate or amide (Figure 5) [69][70][71] (using a platinum anode and tungsten cathode electrochemical set-up) [69] or the use of Cu-PyBox chiral ligand systems [72]. The cation pool method can be adapted to a multicomponent reaction (MCR) when an N-acyliminium ion is

Molecular ordering at electrified interfaces: Template and potential effects

• Thanh Hai Phan and
• Klaus Wandelt

Beilstein J. Org. Chem. 2014, 10, 2243–2254, doi:10.3762/bjoc.10.233

• corresponding CV data. The whole experimental setup is home-built and described in detail in [25]. The tunneling tips used in all experiments were electrochemically etched from 0.25 mm in diameter tungsten wire in 2 mM KOH solution, rinsed with high purity water, dried and subsequently insulated by passing them

Photo, thermal and chemical degradation of riboflavin

• Muhammad Ali Sheraz,
• Sadia Hafeez Kazi,
• Sofia Ahmed,
• Zubair Anwar and
• Iqbal Ahmad

Beilstein J. Org. Chem. 2014, 10, 1999–2012, doi:10.3762/bjoc.10.208

• (medium pressure mercury vapor lamp, 125 W), i.e., 2.19 ± 0.12 × 1018 quanta s−1 as compared to the visible sources (high pressure mercury vapor fluorescent lamp, 125 W and tungsten lamp, 150 W), i.e., 1.14 ± 0.10 × 1017 and 1.06 ± 0.11 × 1016 quanta s−1, respectively [24][26]. Previously it was reported

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

• - and gold-catalyzed versions of tandem reactions involving a DVCPR. Tungsten, platinum and gold catalysed cycloisomerizations leading to a DVCPR. Reisman’s total synthesis of salvileucalin B, featuring an (undesired) vinylcyclopropyl carbaldehyde rearrangement. Studies on the divinylepoxide

Photoinduced synthesis of unsymmetrical diaryl selenides from triarylbismuthines and diaryl diselenides

• Yohsuke Kobiki,
• Shin-ichi Kawaguchi,
• Takashi Ohe and
• Akiya Ogawa

Beilstein J. Org. Chem. 2013, 9, 1141–1147, doi:10.3762/bjoc.9.127

• gel chromatography (the yield was determined by HPLC). Next, optimization of the reaction conditions was investigated as shown in Table 1. Irradiation by a tungsten lamp instead of a xenon lamp did not induce the desired arylation reaction (Table 1, entry 2), and in the dark, the reaction did not

• ) [66] and accordingly, the seleno radical could be produced by the irradiation with a tungsten lamp. However, the irradiation by a tungsten lamp instead of a xenon lamp did not result in the desired reaction (Table 1, entry 3). This fact strongly suggests that the formation of a phenylseleno radical is

Flow photochemistry: Old light through new windows

• Jonathan P. Knowles,
• Luke D. Elliott and
• Kevin I. Booker-Milburn

Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229

• 0.95 g of product 21 was produced the lack of reported details make it difficult to say how scaleable this is likely to be. Rose Bengal has also been employed as a sensitiser in a microchip reactor equipped with a 20 W tungsten lamp for the addition of singlet oxygen to α-terpinene to yield the

• anthelmintic asaridole (23, Scheme 8) [32]. Comparison of this microflow reaction to a batch reaction using a 500 W tungsten lamp showed that although the microflow reaction gave a higher yield (85% versus 67%), the productivity of the flow reactor was markedly lower (1.5 mg/h versus 175 mg/h). This highlights

Tricyclic flavonoids with 1,3-dithiolium substructure

• Lucian G. Bahrin,
• Peter G. Jones and
• Henning Hopf

Beilstein J. Org. Chem. 2012, 8, 1999–2003, doi:10.3762/bjoc.8.226

• unit. In addition to this, they are known to possess anti-inflammatory activity, inhibit the lens-aldose reductase, and decrease the blood glucose level [11][12]. Moreover, compound 3 was shown to inhibit HIV-1 integrase [13][14]. Several molybdenum and tungsten oxobisdithiolene complexes have been

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225

• phosphinidenes generated in situ from various stable precursors. For example, the tungsten-complexed pentacarbonyl complex PhP=W(CO)5, generated by heating 191 (retro-Diels–Alder reaction), provided the unexpected 3,4-disubstituted phosphole 192 (Scheme 45) [133]. Analogously, the phospholene complex 194

Metal–ligand multiple bonds as frustrated Lewis pairs for C–H functionalization

• Matthew T. Whited

Beilstein J. Org. Chem. 2012, 8, 1554–1563, doi:10.3762/bjoc.8.177

•  5) [38]. This reaction is important for the hydroamination of alkynes by Cp2ZrX2 complexes, which proceeds through zirconium imido intermediates [39]. A similar [2 + 2] cycloaddition of symmetrical alkynes across a tungsten nitride is the initial step in Johnson's nitrile-alkyne cross metathesis

N-Heterocyclic carbene/Brønsted acid cooperative catalysis as a powerful tool in organic synthesis

• Rob De Vreese and
• Matthias D’hooghe

Beilstein J. Org. Chem. 2012, 8, 398–402, doi:10.3762/bjoc.8.43

• preparation and characterization of a metal carbene complex in 1964 through nucleophilic attack of phenyllithium at tungsten hexacarbonyl followed by O-alkylation [1], and Arduengo described the preparation of the first free and stable N-heterocyclic carbene 2 by deprotonation of the corresponding imidazolium

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

• 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

• alkenes. Examples of these cycloadditions, originally reported under tungsten catalysis [51], have been recently reported by Iwasawa with Au(III) and Pt(II) catalysts [52], allowing the assembly of interesting tricyclic indole skeletons 16 in good yields (Scheme 9). In 2008, Shin and coworkers reported an

• researchers to undercover new types of selective and very efficient cycloaddition reactions that would otherwise be unfeasible. Additionally, the scope and versatility of previously reported transition metal-catalyzed cycloaddition reactions (e.g., those based on tungsten or platinum catalysts) could be

Ene–yne cross-metathesis with ruthenium carbene catalysts

• Cédric Fischmeister and
• Christian Bruneau

Beilstein J. Org. Chem. 2011, 7, 156–166, doi:10.3762/bjoc.7.22

• before the discovery of the very efficient molybdenum and ruthenium metathesis catalysts. In 1980, the polymerization of alkynes initiated by tungsten carbene was demonstrated by Katz [1][2] who proposed metallacyclobutenes as key intermediates in this polymerization. At the same period of time, Geoffroy

• [3] demonstrated that alkyne polymerization could be initiated directly from terminal alkynes without previous preparation of a metal carbene but via the formation of a reactive vinylidene tungsten species. Later on, the efficiency of ruthenium vinylidene precursors was also shown in olefin

• metathesis [4][5][6][7][8][9][10]. It is noteworthy that polymerization of terminal alkynes [11][12][13] and cyclotrimerization of triynes [14][15][16][17][18][19][20] with ruthenium carbene precursors is still a topic of current interest. Then, Fischer tungsten carbene complexes were used by Katz [21], and

Recent advances in the development of alkyne metathesis catalysts

• Xian Wu and
• Matthias Tamm

Beilstein J. Org. Chem. 2011, 7, 82–93, doi:10.3762/bjoc.7.12

• Xian Wu Matthias Tamm Institut für Anorganische und Analytische Chemie, Technische Universität Braunschweig, Hagenring 30, 38106 Braunschweig, Germany 10.3762/bjoc.7.12 Abstract The number of well-defined molybdenum and tungsten alkylidyne complexes that are able to catalyze alkyne metathesis

• reactions efficiently has been significantly expanded in recent years.The latest developments in this field featuring highly active imidazolin-2-iminato- and silanolate–alkylidyne complexes are outlined in this review. Keywords: alkynes; homogeneous catalysis; metathesis; molybdenum; tungsten; Review

• Schrock system containing imidazolin-2-iminato ligands that was developed by our group; 2. silanolate-supported complexes such as molybdenum nitride and alkylidyne complexes with Ph3SiO ligands developed by Fürstner and tungsten alkylidyne complexes with (t-BuO)3SiO ligands introduced by us. Since there

The cross-metathesis of methyl oleate with cis-2-butene-1,4-diyl diacetate and the influence of protecting groups

• Arno Behr and
• Jessica Pérez Gomes

Beilstein J. Org. Chem. 2011, 7, 1–8, doi:10.3762/bjoc.7.1

• research only the tungsten catalysed cross-metathesis of methyl 10-undecenoate with 2 has been described [28]. The highest yield of the resulting cross-metathesis product was 51% after 2 h at 125 °C. With Grubbs 1st generation catalyst [Ru]-1, the reaction temperature could be lowered to 45 °C

Light-induced olefin metathesis

• Yuval Vidavsky and
• N. Gabriel Lemcoff

Beilstein J. Org. Chem. 2010, 6, 1106–1119, doi:10.3762/bjoc.6.127

• metathesis stands out as both academically motivating and practically useful. Starting from early tungsten heterogeneous photoinitiated metathesis, up to modern ruthenium methods based on complex photoisomerisation or indirect photoactivation, this survey of the relevant literature summarises past and

• present developments in the use of light to expedite olefin ring-closing, ring-opening polymerisation and cross-metathesis reactions. Keywords: catalysis; light activation; olefin metathesis; photoactivation; photoinitiation; photoisomerisation; RCM; ROMP; ruthenium; tungsten; Introduction The metal

• early beginnings of light induced olefin metathesis by the use of ill defined tungsten complexes, up to the most recent developments in light induced ruthenium based isomerisation and activation. Review Early tungsten catalysed photometathesis The first examples for photoinitiated metathesis were

Solvent-free and time-efficient Suzuki–Miyaura reaction in a ball mill: the solid reagent system KF–Al₂O₃ under inspection

• Franziska Bernhardt,
• Ronald Trotzki,
• Tony Szuppa,
• Achim Stolle and
• Bernd Ondruschka

Beilstein J. Org. Chem. 2010, 6, No. 7, doi:10.3762/bjoc.6.7

• -low amounts of Pd [64][65][66] required either longer reaction times or co-grinding with higher-weight milling balls (ZrO2, stainless steel, tungsten carbide) [40][67][68]. The application of the as-prepared KF-loaded SRS in the other Suzuki–Miyaura reactions led to interesting results summarized in

The use of silicon- based tethers for the Pauson- Khand reaction

• Adrian P. Dobbs,
• Ian J. Miller and
• Saša Martinović

Beilstein J. Org. Chem. 2007, 3, No. 21, doi:10.1186/1860-5397-3-21

• being reacted with each of molybdenum hexacarbonyl/DMSO[21]; tungsten pentacarbonyl/THF[22]; chromium hexacarbonyl and rhodium cycloooctadiene chloride dimer/pentafluorobenzaldehyde[23][24]. None of the promoters gave any Pauson-Khand adducts, although an interesting THF-insertion adduct was obtained

• from the reaction of allyldimethylpent-4-ynyloxysilane with tungsten pentacarbonyl, possibly formed via oxidation of THF to give an oxonium ion followed by addition of the alcohol cleaved from the silyl ether (Figure 3). In order to investigate if the presence of the silicon linker was preventing the

High stereoselectivity on low temperature Diels- Alder reactions

• Luiz Carlos da Silva Filho,
• Valdemar Lacerda Júnior,
• Mauricio Gomes Constantino,
• Gil Valdo José da Silva and
• Paulo Roberto Invernize

Beilstein J. Org. Chem. 2005, 1, No. 14, doi:10.1186/1860-5397-1-14

• substrates 2-Methyl-2-cyclohexen-1-one (3) [19] To a solution of 2-methyl-cyclohexanone (3.4 g, 30.3 mmol) in 40.0 mL of CCl4 was added 5.3 g of (NBS) N-bromo-succicinimide (30.0 mmol). The mixture was stirred and refluxed for 4 h heating with a 200 W tungsten lamp. The reaction was cooled, filtered and the