Olefin metathesis in air

• Lorenzo Piola,
• Fady Nahra and
• Steven P. Nolan

Beilstein J. Org. Chem. 2015, 11, 2038–2056, doi:10.3762/bjoc.11.221

• solvents, and yielded products with high enantiomeric excess (ee). The results where comparable to previously reported results for molybdenum-catalyzed systems [57], although the latter was used under inert conditions. In 2003, Blechert et al. reported the first systematic example of olefin metathesis in

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

Consequences of the electronic tuning of latent ruthenium-based olefin metathesis catalysts on their reactivity

• Karolina Żukowska,
• Eva Pump,
• Aleksandra E. Pazio,
• Krzysztof Woźniak,
• Luigi Cavallo and
• Christian Slugovc

Beilstein J. Org. Chem. 2015, 11, 1458–1468, doi:10.3762/bjoc.11.158

• , many stunning accomplishments have been made in the field resulting in ever increasing interests in the method. Establishment of well-defined molybdenum- and ruthenium-based complexes lead to multitude of applications [2][3][4]. Especially, the latter class of compounds have gained attention due to

Novel carbocationic rearrangements of 1-styrylpropargyl alcohols

• Christine Basmadjian,
• Fan Zhang and
• Laurent Désaubry

Beilstein J. Org. Chem. 2015, 11, 1017–1022, doi:10.3762/bjoc.11.114

• molybdenum(VI)-catalyzed etherification of allylic alcohol with a gold(I)-catalyzed intramolecular cyclization process [5][6]. During the optimization process of this synthesis, we examined several catalysts to transform allylic alcohol 1 into ether 2, including Re2O7, which is described to efficiently

N–O Cleavage reactions of heterobicycloalkene-fused 2-isoxazolines

• Jaipal R. Nagireddy,
• Geoffrey K. Tranmer,
• Emily Carlson and
• William Tam

Beilstein J. Org. Chem. 2014, 10, 2200–2205, doi:10.3762/bjoc.10.227

• former Mo(CO)6-promoted approach. We elected substrate 10a (Scheme 2, R’ = Me, R = X = Y = H) for early optimization trials. The molybdenum-mediated conditions, however, were unsuccessful at both the previously optimized temperature of 80 °C (which led to extensive degradation) and at lower temperatures

• to 22, suggesting the potential utility of the isoxazoline-cleavage reaction with other azabicyclic systems. In our initial report of molybdenum-mediated cleavage of carbobicycloalkene-fused isoxazolines 8, we proposed a general mechanism of the transformation to attached ring system 9 (Scheme 4). As

• the carbobicyclic framework contains no metal-coordinatable atom, we assumed that the cleavage reaction proceeds with initial coordination of the nitrogen atom to molybdenum, as suggeseted by Simoni and coworkers [18]. In comparison, the β-hydroxyketones 16 generated in the current investigation

Reaction of 2,2,4,4-tetrakis(trifluoromethyl)-1,3-dithiethane with N-vinyl compounds

• Viacheslav A. Petrov and
• Will Marshall

Beilstein J. Org. Chem. 2013, 9, 2615–2619, doi:10.3762/bjoc.9.295

• collected at −100 °C by using a Bruker 1K CCD system equipped with a sealed tube molybdenum source and a graphite monochromator. The structures were solved and refined with the Shelxtl [13] software package, refinement by full-matrix least squares on F2, scattering factors from Int. Tab. Vol. C Tables

An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265

• , which can then be subsequently hydrolysed to nicotinic acid. The catalyst systems most commonly used in this high temperature ammoxidation are based on vanadium, molybdenum or antimony oxides supported on silica or alumina. Since the initial Chichibabin type sequence (step 1; Scheme 3) leading to 3

Gold(I)-catalysed one-pot synthesis of chromans using allylic alcohols and phenols

• Eloi Coutant,
• Paul C. Young,
• Graeme Barker and
• Ai-Lan Lee

Beilstein J. Org. Chem. 2013, 9, 1797–1806, doi:10.3762/bjoc.9.209

• dehydrative coupling strategy) [15][16]. To this end, the use of molybdenum catalyst CpMoCl(CO)3 together with an oxidant, o-chloranil, has been documented to catalyse the reaction of allylic alcohols with phenols to form chromans [17][18]. Strong and superacids have also been utilised in the synthesis of

Gallium-containing polymer brush film as efficient supported Lewis acid catalyst in a glass microreactor

• Rajesh Munirathinam,
• Roberto Ricciardi,
• Richard J. M. Egberink,
• Jurriaan Huskens,
• Michael Holtkamp,
• Herbert Wormeester,
• Uwe Karst and
• Willem Verboom

Beilstein J. Org. Chem. 2013, 9, 1698–1704, doi:10.3762/bjoc.9.194

• AXS, Berlin, Germany) with an air-cooled molybdenum anode for X-ray generation. The excitation settings were 50 kV and 750 mA and quartz glass disks were used as sample carriers. The analysis was performed by signal integration over 500 seconds. For the determination, the signal of gallium (Kα1

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

Efficient electroorganic synthesis of 2,3,6,7,10,11-hexahydroxytriphenylene derivatives

• Carolin Regenbrecht and
• Siegfried R. Waldvogel

Beilstein J. Org. Chem. 2012, 8, 1721–1724, doi:10.3762/bjoc.8.196

• [8][9]. Typically, the oxidative trimerization of catechol derivatives can be induced by metal salts in high oxidation states, for example by molybdenum pentachloride [4][10]. Electrochemical methods can be applied to realize the oxidative trimerization since the formation of metal waste is avoided

Synthesis and in silico screening of a library of β-carboline-containing compounds

• Kay M. Brummond,
• John R. Goodell,
• Matthew G. LaPorte,
• Lirong Wang and
• Xiang-Qun Xie

Beilstein J. Org. Chem. 2012, 8, 1048–1058, doi:10.3762/bjoc.8.117

• molybdenum hexacarbonyl in DMSO/toluene solutions (Table 3). Allene-yne 9{1,2} afforded a mixture of four compounds comprising two diastereomers of 3{1,2}, the 4-alkylidene cyclopentenone, resulting from the cyclocarbonylation reaction with the distal double of the allene, and a fourth compound, which could

• not be identified (see spectral data in Supporting Information File 1). Aryl-substituted alkynones 9{1,5}–9{1,8} were not available for the molybdenum-mediated cyclocarbonylation process due to competing [2 + 2] cycloaddition reactions (Table 2). The majority of these β-carboline-containing products

Reciprocal polyhedra and the Euler relationship: cage hydrocarbons, C_nH_n and closo-boranes [B_xH_x]²⁻

• Michael J. McGlinchey and
• Henning Hopf

Beilstein J. Org. Chem. 2011, 7, 222–233, doi:10.3762/bjoc.7.30

• the centers of adjacent faces of the octahedron are connected, they yield a cube and vice versa; this is beautifully illustrated by the X-ray crystal structure of the [Mo6Cl8]4+ cluster in which an octahedron of molybdenum atoms is encapsulated within a cube of chlorines (Figure 2). The icosahedron

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

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 catalytic performance of Ru–NHC alkylidene complexes: PCy₃ versus pyridine as the dissociating ligand

• Stefan Krehl,
• Diana Geißler,
• Sylvia Hauke,
• Oliver Kunz,
• Lucia Staude and
• Bernd Schmidt

Beilstein J. Org. Chem. 2010, 6, 1188–1198, doi:10.3762/bjoc.6.136

• reactions in organic synthesis [1]. The elucidation of the crucial role of metal carbenes by Chauvin [2] and the development of stable and defined precatalysts for homogeneously catalyzed reactions by Schrock [3] and Grubbs [4] paved the way for this development. Since then, molybdenum- [5] and ruthenium

About the activity and selectivity of less well-known metathesis catalysts during ADMET polymerizations

• Hatice Mutlu,
• Lucas Montero de Espinosa,
• Oĝuz Türünç and
• Michael A. R. Meier

Beilstein J. Org. Chem. 2010, 6, 1149–1158, doi:10.3762/bjoc.6.131

• demonstrated that, while Grubbs 1st generation and Schrock's molybdenum alkylidene catalysts did not produce appreciable double bond isomerization, Grubbs 2nd generation catalyst presented significant isomerization activity, which was greatly reduced at temperatures below 30 ºC [17][28]. These studies were

Light-induced olefin metathesis

• Yuval Vidavsky and
• N. Gabriel Lemcoff

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

• ] determined the heterogeneous character of the active catalytic species obtained on irradiation of 1 in CCl4, supporting the previous proposal by Harfouch and coworkers. In another example of heterogeneous light induced metathesis, Shelimov and Kazansky [51] also found that silica supported molybdenum

Progress in metathesis chemistry

• Karol Grela

Beilstein J. Org. Chem. 2010, 6, 1089–1090, doi:10.3762/bjoc.6.124

• development of the metathesis method in organic synthesis” has been fully recognized by the award of the Nobel Prize in Chemistry for 2005 jointly to Yves Chauvin, Robert H. Grubbs, and Richard R. Schrock [2]. Organic chemists are now provided with molybdenum and ruthenium complexes that present good

• more sensitive towards air and moisture, molybdenum catalysts provide excellent results in stereoselective metathesis and are sometimes more active. Therefore these catalyst families can be used in a complementary fashion. Currently, olefin metathesis (and its sister reaction, alkyne metathesis) [3] is

Synthesis and crossover reaction of TEMPO containing block copolymer via ROMP

• Olubummo Adekunle,
• Susanne Tanner and
• Wolfgang H. Binder

Beilstein J. Org. Chem. 2010, 6, No. 59, doi:10.3762/bjoc.6.59

• catalysts for ROMP were based on molybdenum alkylidene catalysts, however, the true breakthrough of the method was hampered by the restricted functional group tolerance of Schrock initiators due to their sensitivity towards protic solvents and air [6]. With the advent of the Grubbs’ catalyst G1 (see Scheme

• molybdenum catalysts [7][8][9]. Often, the polydispersity indices of the resulting polymers obtained with initiator G1 are large with values ranging between 1.3 and 1.5 arising from an unfavorable rate of initiation (ki) relative to propagation (kp) as well as considerable secondary metathesis (backbiting

Trifluoromethyl ethers – synthesis and properties of an unusual substituent

• Frédéric R. Leroux,
• Baptiste Manteau,
• Jean-Pierre Vors and
• Sergiy Pazenok

Beilstein J. Org. Chem. 2008, 4, No. 13, doi:10.3762/bjoc.4.13

• pentachloride (Scheme 3). The latter compounds can be obtained directly when treated with molybdenum hexafluoride [22]. Unfortunately, the high percutaneous toxicity of the chlorothionoformates 1 prohibited any industrial exploitation so far. W. Sheppard described in 1964 the syntheses of aryl

Desymmetrization of 7-azabicycloalkenes by tandem olefin metathesis for the preparation of natural product scaffolds

• Wolfgang Maison,
• Marina Büchert and
• Nina Deppermann

Beilstein J. Org. Chem. 2007, 3, No. 48, doi:10.1186/1860-5397-3-48

• accomplished while generating a double bond as a valuable functional group for further manipulations. In addition, the common ruthenium (Figure 1) and molybdenum based catalysts for olefin metathesis are well known for their broad functional group tolerance. The application of RCM to the synthesis of

• desymmetrization of bis-olefin 10 with the known chiral ruthenium catalyst 3.[67] This reaction gave enantioenriched 11 in good yield (Scheme 5). However, the enantioselectivity of this reaction is only moderate compared to similar reactions using molybdenum based precatalysts and different azabicycloalkene

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

• tethers did not seem to be compatible with the Pauson-Khand reaction. Fortunately her research discovered that by combining the silicon tether with the allenic Pauson-Khand reaction mediated by molybdenum hexacarbonyl the corresponding bicyclic cyclopentenone could be formed although with poor yields

• 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