Hoveyda–Grubbs catalysts with an N→Ru coordinate bond in a six-membered ring. Synthesis of stable, industrially scalable, highly efficient ruthenium metathesis catalysts and 2-vinylbenzylamine ligands as their precursors

• Kirill B. Polyanskii,
• Kseniia A. Alekseeva,
• Pavel V. Raspertov,
• Pavel A. Kumandin,
• Eugeniya V. Nikitina,
• Atash V. Gurbanov and
• Fedor I. Zubkov

Beilstein J. Org. Chem. 2019, 15, 769–779, doi:10.3762/bjoc.15.73

• possible to overcome this problem [44]. Thus, the pathways described in Schemes 1–3 permit one to vary the steric volume of substituents at the nitrogen atom in a wide range enabling synthesis of selective Grubbs catalysts with different catalytic activity. These styrenes were used in the preparation of

• should have the strongest effect on the catalytic activity. With the increase of the steric volume of substituents at the nitrogen atom, the ruthenium–nitrogen coordinate bond is extended, which makes it weaker. That should, obviously, increase the activity of the catalyst towards metathesis reactions

• process, temperature also exerts a strong influence on the catalytic activity of metallo complexes 11. None of catalysts 11 were active at room temperature (19–23 °С) towards the styrene cross metathesis, meaning that all reactions required temperatures higher than 30–35 °С. After all observations, we

Synthesis of polydicyclopentadiene using the Cp₂TiCl₂/Et₂AlCl catalytic system and thin-layer oxidation of the polymer in air

• Zhargolma B. Bazarova,
• Ludmila S. Soroka,
• Alex A. Lyapkov,
• Мekhman S. Yusubov and
• Francis Verpoort

Beilstein J. Org. Chem. 2019, 15, 733–745, doi:10.3762/bjoc.15.69

• catalytic activity of the Cp2TiCl2/organoaluminum compound is determined by the molar ratio of the components of the catalytic system [15]. The rate of transformation in the system depends both on the Al:Ti molar ratio and on the temperature [16]. UV spectra of toluene solutions of Cp2TiCl2 and AlEt2Cl

Back to the future: Why we need enzymology to build a synthetic metabolism of the future

• Tobias J. Erb

Beilstein J. Org. Chem. 2019, 15, 551–557, doi:10.3762/bjoc.15.49

• point to search for enzyme variants that possess a desired catalytic activity. While existing databases might provide a good resource to find the parts to reconstruct level 3 pathways, this task becomes more challenging in respect to level 4 and level 5 designs that require new-to-nature reactions. How

Aqueous olefin metathesis: recent developments and applications

• Valerio Sabatino and
• Thomas R. Ward

Beilstein J. Org. Chem. 2019, 15, 445–468, doi:10.3762/bjoc.15.39

• on the catalytic activity of the reaction. In fact, catalyst and substrate are encapsulated into emulsion droplets formed in the reaction media above the aqueous layer, making the reaction proceed “on water” [21][22]. The introduction of amphiphilic molecules for aqueous micellar catalysis allows

• -metathesis of allyl alcohol (59) and the cis–trans isomerization of cis-butenedienol (Z-58). Metathesis catalysts bearing quaternary ammonium groups provide an attractive alternative to classical ruthenium catalysts. Although they do not represent a great improvement in terms of catalytic activity, they

Application of olefin metathesis in the synthesis of functionalized polyhedral oligomeric silsesquioxanes (POSS) and POSS-containing polymeric materials

• Patrycja Żak and
• Cezary Pietraszuk

Beilstein J. Org. Chem. 2019, 15, 310–332, doi:10.3762/bjoc.15.28

• and do not show catalytic activity in metathesis. The most important consequences of the above-described reactivity in metathesis of vinyl-substituted siloxanes, spherosilicates and silsesquioxanes are presented in Figure 2. It should be indicated that one of the consequences of the described

• allyltrimethoxysilane, ethyl undec-10-enylate, oct-7-enyltrimethoxysilane, 5-bromopentene, pent-4-en-1-ol) and styrene. Moreover, the catalytic activity of the first generation Grubbs’ catalyst (Ru-1) was demonstrated in CM of OVS with pent-4-en-1-ol and 5-bromopentene. It has been found that terminal alkenes undergo

Catalysis of linear alkene metathesis by Grubbs-type ruthenium alkylidene complexes containing hemilabile α,α-diphenyl-(monosubstituted-pyridin-2-yl)methanolato ligands

• Tegene T. Tole,
• Johan H. L. Jordaan and
• Hermanus C. M. Vosloo

Beilstein J. Org. Chem. 2019, 15, 194–209, doi:10.3762/bjoc.15.19

• -quinolinolate Grubbs 2-type derivative, patented by Slugovc and Wappel [15] for use in ROMP reactions, was found to be inactive (<1% conversion) for 1-octene metathesis at 60 °C [12]. Schachner et al. [16] evaluated the catalytic activity of 5b, 5d and related complexes for the ROMP of cyclooctene, CM of hex-5

• precatalyst 6 at 420 min. At 420 min, 1-octene conversion is 98.0% (110 °C), 93.0% (100 °C), 70.5% (90 °C), 19.4% (80 °C), 6.8% (70 °C) and 2.5% (60 °C). This shows the dramatic increase of the catalytic activity upon increasing the temperature. An investigation of the PMPs formation reveals a huge 66

• , on the overall metathesis reaction. During the course of PMPs formation, high catalytic activity for 9 is observed within 200 min at temperatures above 90 °C (ca. 60%), while the activity of the precatalyst showed a dramatic increase from 70 to 90 °C after ca. 500 min, similar to that of 6 (see

Silanediol versus chlorosilanol: hydrolyses and hydrogen-bonding catalyses with fenchole-based silanes

• Falco Fox,
• Jörg M. Neudörfl and
• Bernd Goldfuss

Beilstein J. Org. Chem. 2019, 15, 167–186, doi:10.3762/bjoc.15.17

• )–2.05(2) Å) than with chlorosilanol 8 (OH···2.16(0) Å). Due to its two hydroxy units, the silanediol 9 shows higher catalytic activity as hydrogen bond donor than chlorosilanol 8, e.g., C–C coupling N-acyl Mannich reaction of silyl ketene acetals 11 with N-acylisoquinolinium ions (up to 85% yield and 12

• (Scheme 6). The reactivity and stability of such an ion pair depend on the employed solvent. For this reaction and BIFOXSi(OH)2 (9) as catalyst, several solvents are tested (Table 7). In a nonpolar solvent like n-hexane, no catalytic activity is observed (Table 7, entry 1). In halogenated solvents as

• not show catalytic activity for the reaction of 18 with 11a, as the background reaction is slightly faster (54% vs 58%, Table 10, entries 9 and 13). With increasing of the steric demand of the nucleophilic silyl group, the background reaction slows down and chlorosilanol 8 has a positive influence on

Ammonium-tagged ruthenium-based catalysts for olefin metathesis in aqueous media under ultrasound and microwave irradiation

• Łukasz Gułajski,
• Andrzej Tracz,
• Katarzyna Urbaniak,
• Stefan J. Czarnocki,
• Michał Bieniek and
• Tomasz K. Olszewski

Beilstein J. Org. Chem. 2019, 15, 160–166, doi:10.3762/bjoc.15.16

• Abstract The influence of microwave and ultrasonic irradiation on the performance of ammonium-tagged Ru-based catalysts in olefin metathesis transformations in aqueous media was studied. Differences in the catalytic activity in correlation with the nature of the present counter ion and the size of the N

• only in academia but also in industry [7][8][9][10][11][12]. However, there is still a large interest in improving the catalytic activity of the existing Ru-based metathesis catalysts as there is no universal catalyst for all the metathesis transformations. This is especially true for olefin metathesis

• (e.g., 50 mg mL−1 for 1a or 3a) whereas for those with I− as counter-ion is much lower (e.g., 4.0 mg mL−1 for 1b). In turn catalysts bearing PF6− or BF4− as counter ions are not soluble in water [71]. We have started our study with the comparison of the catalytic activity of complex 4b, having the

Gold-catalyzed ethylene cyclopropanation

• Silvia G. Rull,
• Andrea Olmos and
• Pedro J. Pérez

Beilstein J. Org. Chem. 2019, 15, 67–71, doi:10.3762/bjoc.15.7

• ethyl diazoacetate.a Catalytic activity of IPrAuCl/NaBArF4 in the reaction of ethylene and ethyl diazoacetate.a Acknowledgements Support for this work was provided by the MINECO (CTQ2017-82893-C2-1-R and CTQ2015-73693-JIN).

Asymmetric synthesis of a high added value chiral amine using immobilized ω-transaminases

• Antonella Petri,
• Valeria Colonna and
• Oreste Piccolo

Beilstein J. Org. Chem. 2019, 15, 60–66, doi:10.3762/bjoc.15.6

• excess starting from a commercial substrate. The reaction was carried out by using different commercially available immobilized enzymes, evaluating the catalytic activity and the enantioselectivity under different experimental conditions. Re-use of the most efficient enzyme was performed both in batch

Ruthenium-based olefin metathesis catalysts with monodentate unsymmetrical NHC ligands

• Veronica Paradiso,
• Chiara Costabile and
• Fabia Grisi

Beilstein J. Org. Chem. 2018, 14, 3122–3149, doi:10.3762/bjoc.14.292

• and 4a clearly outperformed GII-SIMes, with catalyst 4a emerging as the most efficient of all (>97% conversion in 9 min). Complex 5a showed a higher initiation rate with respect to GII-SIMes, but eventually was found to be less efficient due to a decrease in its catalytic activity related to

• beneficial effect on the catalytic activity was observed. Indeed complex 22 revealed a very poor olefin metathesis catalyst, likely as a consequence of the excessive steric hindrance of the adamantyl moiety at the ruthenium center. It is worth to underline that the first Z-selective ruthenium catalyst (23

• reported by Blechert and co-workers [21]. In addition to the concept that the presence of more electron-donating alkyl groups on the NHC could lead to enhanced σ-donor properties, and, consequently, to higher catalytic activity, the authors postulated that the unsymmetrical nature of the NHC ligands could

Thermophilic phosphoribosyltransferases Thermus thermophilus HB27 in nucleotide synthesis

• Ilja V. Fateev,
• Ekaterina V. Sinitsina,
• Aiguzel U. Bikanasova,
• Maria A. Kostromina,
• Elena S. Tuzova,
• Larisa V. Esipova,
• Tatiana I. Muravyova,
• Alexei L. Kayushin,
• Irina D. Konstantinova and
• Roman S. Esipov

Beilstein J. Org. Chem. 2018, 14, 3098–3105, doi:10.3762/bjoc.14.289

• phosphoribosyltransferase Thermus thermophilus (TthHPRT), investigated its substrate specificity and optimal conditions for catalytic activity, and determined the kinetic parameters of the enzyme. A comparative study of the substrate specificity of TthAPRT and TthHPRT was performed to determine the usability of

A tutorial review of stereoretentive olefin metathesis based on ruthenium dithiolate catalysts

• Daniel S. Müller,
• Olivier Baslé and
• Marc Mauduit

Beilstein J. Org. Chem. 2018, 14, 2999–3010, doi:10.3762/bjoc.14.279

• introduced by Hoveyda in 2015 [4] showed moderate to good catalytic activity and can therefore be considered as a relatively general catalyst (Figure 1). In 2016 Pederson and Grubbs reported SIPr-based catalyst Ru-4 with increased catalytic activity for Z-alkenes (Figure 1) [3]. Further improvement was made

MoO₃ on zeolites MCM-22, MCM-56 and 2D-MFI as catalysts for 1-octene metathesis

• Hynek Balcar,
• Martin Kubů,
• Naděžda Žilková and
• Mariya Shamzhy

Beilstein J. Org. Chem. 2018, 14, 2931–2939, doi:10.3762/bjoc.14.272

• metathesis catalysts [1]. Albeit typical ill-defined catalysts they are still popular as relatively cheap catalysts finding industrial applications especially in the treatment of low olefins [2][3][4][5]. Their catalytic activity depends on many factors, especially on Mo loading, support acidity, and pre

• -reaction activations. Surface isolated MoO4 tetrahedra were proved as the main precursors of the catalytic species [6][7], thus the perfect dispersion of MoO3 on the surface is a crucial precondition for a high catalytic activity. The mechanisms of transformation of these precursors to the surface Mo

• the parent supports. It may be explained by the formation of some amount of Mo in a lower oxidation state which has been already described for siliceous supports (MCM-41, SBA-15) [9][26]. Catalytic activity MCM-22-based catalysts Na+ forms of zeolites turned out to be unsuitable supports for

Protein–protein interactions in bacteria: a promising and challenging avenue towards the discovery of new antibiotics

• Laura Carro

Beilstein J. Org. Chem. 2018, 14, 2881–2896, doi:10.3762/bjoc.14.267

• inhibition of the catalytic activity of the enzyme [23]. All these drug discovery successes have validated PPIs as a target and, in conjunction with the elucidation and reconstruction of protein–protein interaction networks in bacteria, have paved the way towards the development of novel and promising

Copolymerization of epoxides with cyclic anhydrides catalyzed by dinuclear cobalt complexes

• Yo Hiranoi and
• Koji Nakano

Beilstein J. Org. Chem. 2018, 14, 2779–2788, doi:10.3762/bjoc.14.255

• benzene ring as a linker and their activities in copolymerization reactions. The dinuclear cobalt complexes showed a higher catalytic activity for the copolymerization of propylene oxide with phthalic anhydride than the corresponding mononuclear cobalt–salen complex and achieved one of the highest

• turnover frequencies ever reported. A variety of epoxides and CAs were also found to be copolymerized successfully by the dinuclear cobalt complex with a high catalytic activity. Keywords: cobalt; copolymerization; cyclic anhydrides; epoxides; polyesters; Introduction Aliphatic polyesters have received

• epoxide/CA copolymerization was constricted until recently because of low catalytic activity and poor control over the main chain sequence (formation of ether linkages through consecutive epoxide enchainment) and molecular weight. In 2007, Coates and co-workers reported that β-diiminate zinc complexes

An overview on recent advances in the synthesis of sulfonated organic materials, sulfonated silica materials, and sulfonated carbon materials and their catalytic applications in chemical processes

• Hashem Sharghi,
• Pezhman Shiri and
• Mahdi Aberi

Beilstein J. Org. Chem. 2018, 14, 2745–2770, doi:10.3762/bjoc.14.253

• homogeneous catalysts (Scheme 7). Significantly, IL catalysts 47b,c could be extracted from the reaction mixture for six consecutive cycles. In all runs, IL catalysts 47b,c showed excellent catalytic activity. The FTIR spectra of two of these reused ILs after the 6th run and the fresh ILs have been used to

• prove the retention of their catalytic activity [46]. Khazaei et al. prepared 3-methyl-1-sulfo-1H-imidazolium tetrachloroferrate ([Msim]FeCl4, 3) as a nanostructured catalyst via the reaction of 3-methyl-1-sulfon-1H-imidazolium chloride with dry FeCl3. After stirring the starting materials for 60

• products from the catalyst. The catalyst showed good catalytic activity for four successive runs [47]. Tayebee and co-workers prepared 3-sulfo-imidazolopyridinium hydrogen sulfate ([Simp]HSO4, 53) as a new natural ionic liquid by the reaction between caffeine (51) as a natural, inexpensive, and available

Photocatalyic Appel reaction enabled by copper-based complexes in continuous flow

• Clémentine Minozzi,
• Jean-Christophe Grenier-Petel,
• Shawn Parisien-Collette and
• Shawn K. Collins

Beilstein J. Org. Chem. 2018, 14, 2730–2736, doi:10.3762/bjoc.14.251

• conversion of an alcohol to bromide involved screening a wide variety of structurally varied complexes. Our group has previously demonstrated that the nature of each ligand influences the physical and photophysical properties as well as catalytic activity of the resulting catalyst (Figure 2) [27]. A library

Transition metal-free oxidative and deoxygenative C–H/C–Li cross-couplings of 2H-imidazole 1-oxides with carboranyl lithium as an efficient synthetic approach to azaheterocyclic carboranes

• Lidia A. Smyshliaeva,
• Mikhail V. Varaksin,
• Pavel A. Slepukhin,
• Oleg N. Chupakhin and
• Valery N. Charushin

Beilstein J. Org. Chem. 2018, 14, 2618–2626, doi:10.3762/bjoc.14.240

• capture therapy (BNCT) of cancer [8][9][10][11][12], as well as agonists and antagonists of biological receptors [13][14][15][16][17], etc. In addition, azaheterocyclic carboranes are actively used as ligands in the synthesis of metal complexes of various architectures, possessing catalytic activity [18

Learning from B₁₂ enzymes: biomimetic and bioinspired catalysts for eco-friendly organic synthesis

• Keishiro Tahara,
• Ling Pan,
• Toshikazu Ono and
• Yoshio Hisaeda

Beilstein J. Org. Chem. 2018, 14, 2553–2567, doi:10.3762/bjoc.14.232

• terms of both catalytic activity and visible-light harvesting. In relation to the reactivity of 1 with DDT, interesting reactions of trichlorinated organic compounds have recently been investigated [100][114]. The B12-TiO2 hybrid catalyst converted trichlorinated organic compounds into esters and amides

• use of vitamin B12 [116]. Furthermore, cobalester, an amphiphilic vitamin B12 derivative with six ester groups and a nucleotide loop, has recently been developed to show good catalytic activity for C–C bond forming reactions [117][118]. The above-mentioned visible-light-driven system composed of 1

Efficient catalytic alkyne metathesis with a fluoroalkoxy-supported ditungsten(III) complex

• Henrike Ehrhorn,
• Janin Schlösser,
• Dirk Bockfeld and
• Matthias Tamm

Beilstein J. Org. Chem. 2018, 14, 2425–2434, doi:10.3762/bjoc.14.220

• expanded the “low-oxidation-state route” to the synthesis of 2,4,6-trimethylbenzylidyne complexes of molybdenum and tungsten [18][49][50], which led to an increased steric demand at the metal center. This proved to be advantageous for the catalytic activity, since the removal of coordinating solvents like

• studies With the bimetallic complexes Mo2F6 and W2F3 and the new alkylidyne complex WPhF3 at hand, we aimed at systematically investigating the catalytic activity of those complexes. Even though we failed in selectively cleaving the Mo≡Mo triple bond, we attempted catalytic alkyne metathesis with Mo2F6

• . Interestingly, a marginal catalytic activity could be detected for complex Mo2F6: over the course of four days, the dimolybdenum complex achieved a conversion of 70% in the self-metathesis of the standard substrate 3-pentynyl benzyl ether in toluene in the presence of molecular sieves (MS 5 Å) as 2-butyne

Cationic cobalt-catalyzed [1,3]-rearrangement of N-alkoxycarbonyloxyanilines

• Itaru Nakamura,
• Mao Owada,
• Takeru Jo and
• Masahiro Terada

Beilstein J. Org. Chem. 2018, 14, 1972–1979, doi:10.3762/bjoc.14.172

• 1,3-bis(diphenylphosphino)propane (dppp), totally diminished the activity of cationic cobalt catalyst (Table 1, entries 6 and 7). Among metal chlorides examined, CoCl2 exhibited the best catalytic activity at 30 °C, affording the corresponding 2a in 68% yield (Table 1, entry 9), as reported previously

• , entry 20), the catalytic activity was diminished at 30 °C (Table 1, entry 21). Neutral CoCl2 did not promote the present reaction (Table 1, entry 22). Brønsted acids, such as trifluoromethanesulfonic acid and diphenylphosphoric acid, were much less active (Table 1, entries 23 and 24). The kind of the

• :1) as eluent to obtain 2k (113.9 mg, 82%). ortho-Aminophenol derivatives. Rearrangement of N-acyloxyanilines. Mechanistic studies, reported in [13]. Competitive experiments, reported in [13]. Mechanism for rearrangement to the para-position. Catalytic activity. Solvent and concentration effects

Water-soluble SNS cationic palladium(II) complexes and their Suzuki–Miyaura cross-coupling reactions in aqueous medium

• Alphonse Fiebor,
• Richard Tia,
• Banothile C. E. Makhubela and
• Henok H. Kinfe

Beilstein J. Org. Chem. 2018, 14, 1859–1870, doi:10.3762/bjoc.14.160

• their SCS analogues, SNS pincer complexes are poorly studied for their use in coupling reactions. Accordingly, a series of water soluble cationic Pd(II) SNS pincer complexes have been successfully synthesised and investigated in detail for their catalytic activity in Suzuki–Miyaura coupling reactions

• inactivated aryl bromides according to the study conducted by Bai and Hor [34]. Similarly, Kumar et al. studied the catalytic activity of pincer complex 16 and reported that the catalyst was compatible with activated aryl bromides to provide reasonable yields over 12 h at 100 °C using 2 mol % catalyst loading

• investigation of their catalytic activity in the aqueous Suzuki–Miyaura coupling reaction. Herein, we report the synthesis of the SNS Pd(II) pincer complexes and their interesting catalytic activities in the Suzuki–Miyaura cross coupling reactions in neat water. Results and Discussion Our study commenced with

β-Hydroxy sulfides and their syntheses

• Mokgethwa B. Marakalala,
• Edwin M. Mmutlane and
• Henok H. Kinfe

Beilstein J. Org. Chem. 2018, 14, 1668–1692, doi:10.3762/bjoc.14.143

• Brønsted and Lewis acid and base catalysis. Pizzo and co-workers conducted a comparative study on the catalytic activity of Lewis and Brønsted acids as well as bases for the thiolysis of epoxides using InCl3, p-TsOH, n-Bu3P and K2CO3 as representative examples, respectively. Although all of them effected

• organophosphine was found to have a profound effect on the catalytic activity; some reactions were sluggish when tricyclohexylphosphine or triphenylphosphine were used as catalysts. The tributylphosphine acts as a nucleophilic trigger to attack, and thus initiates the reaction. 3.1.1.3 Use of zinc salts. In

Spectroelectrochemical studies on the effect of cations in the alkaline glycerol oxidation reaction over carbon nanotube-supported Pd nanoparticles

• Dennis Hiltrop,
• Steffen Cychy,
• Karina Elumeeva,
• Wolfgang Schuhmann and
• Martin Muhler

Beilstein J. Org. Chem. 2018, 14, 1428–1435, doi:10.3762/bjoc.14.120

• (Ep1 and Ep2) are found at lower anodic potentials (−29 and −52 mV vs RHE on average) compared with Pd/OCNT. Although the peak current densities are almost equal, the catalytic activity towards glycerol oxidation is higher for Pd/NCNT, as the reaction starts at lower anodic overpotentials. This

• structural properties of the catalyst, whereas the changes in jp1 and jp2 are caused by the nature of the cation in the electrolyte. The higher catalytic activity of the metallic Pd NPs supported on NCNTs in heterogeneous gas-phase catalysis has been explained by an electronic effect due to the electron