The cyclopropylcarbinyl route to γ-silyl carbocations

• Xavier Creary

Beilstein J. Org. Chem. 2019, 15, 1769–1780, doi:10.3762/bjoc.15.170

• analogous mesylate derivatives were relatively unreactive. Triflate 69 was a highly reactive substrate that could only be prepared in about 80% purity. The less reactive mesylate derivative 75 was therefore prepared and used for kinetic studies. The triflates 61, 68, and 69 (with electron-withdrawing groups

• trans to trimethylsilyl) were all solvolyzed in CD3CO2D and results are shown in Scheme 14. Since the triflate 69 was highly reactive and could not be isolated in pure form, the mesylate derivative 75 was used in kinetic studies that were carried out in the 40–60 °C range. Rates of reaction of mesylate

Diazocine-functionalized TATA platforms

• Roland Löw,
• Talina Rusch,
• Fynn Röhricht,
• Olaf Magnussen and
• Rainer Herges

Beilstein J. Org. Chem. 2019, 15, 1485–1490, doi:10.3762/bjoc.15.150

• ) surfaces. Further studies will include IRRAS measurements to determine the trans→cis isomerization kinetics on Au(111) surfaces. Experimental For detailed experimental procedures, including NMR, UV–vis and MS spectra see Supporting Information File 1, chapters I–IV, for kinetic studies see Supporting

• activation energies (Ea) are calculated from the linear fit of an Arrhenius plot. Supporting Information Supporting Information File 526: Analytical methods, experimental procedures, NMR and UV spectra, kinetic studies and DFT calculations. Acknowledgements The authors gratefully acknowledge financial

Efficient resolution of racemic crown-shaped cyclotriveratrylene derivatives and isolation and characterization of the intermediate saddle isomer

• Sven Götz,
• Andreas Schneider and
• Arne Lützen

Beilstein J. Org. Chem. 2019, 15, 1339–1346, doi:10.3762/bjoc.15.133

• formation of diastereomeric esters were also used for other chiral CTV derivatives [63][64][65][66][67]. However, performing the separation on the stage of a monomeric CTV always bears the risk of racemization because of the flexibility of these molecules and kinetic studies for several CTVs demonstrate

Understanding the unexpected effect of frequency on the kinetics of a covalent reaction under ball-milling conditions

• Ana M. Belenguer,
• Adam A. L. Michalchuk,
• Giulio I. Lampronti and
• Jeremy K. M. Sanders

Beilstein J. Org. Chem. 2019, 15, 1226–1235, doi:10.3762/bjoc.15.120

• kinetics is a relatively unexplored field, and we have explored only one reaction, but it seems likely that similar effects will operate for other reactions. Experimental The kinetic studies presented here were performed under ball-mill neat grinding (NG) and under ball mill liquid-assisted grinding (LAG

Precious metal-free molecular machines for solar thermal energy storage

• Meglena I. Kandinska,
• Snejana M. Kitova,
• Vladimira S. Videva,
• Stanimir S. Stoyanov,
• Stanislava B. Yordanova,
• Stanislav B. Baluschev,
• Silvia E. Angelova and
• Aleksey A. Vasilev

Beilstein J. Org. Chem. 2019, 15, 1096–1106, doi:10.3762/bjoc.15.106

• reached. The absorbance was measured by Ocean Optic HR2000+ high resolution USB fiber optic spectrometer fitted with 500 nm interference filter in the incident beam (10 nm bandwidth). During the irradiation and kinetic studies, the solutions were intensively magnetically stirred. A cuvette holder for

Tuning the stability of alkoxyisopropyl protection groups

• Zehong Liang,
• Henna Koivikko,
• Mikko Oivanen and
• Petri Heinonen

Beilstein J. Org. Chem. 2019, 15, 746–751, doi:10.3762/bjoc.15.70

• lower part of Scheme 2. However, accumulation of 8b was not observed during our kinetic studies. Compound 8b was found to be about 15-fold more stable than the cyclohexyl derivative 7c at pH 4.94, which means that it should have been accumulating as an intermediate, if formed in a significant amount

Cyclopropene derivatives of aminosugars for metabolic glycoengineering

• Jessica Hassenrück and
• Valentin Wittmann

Beilstein J. Org. Chem. 2019, 15, 584–601, doi:10.3762/bjoc.15.54

• have been reported: Ac4ManNCyc [23], Ac4ManNCyoc [24][25], and Ac4ManNCp [27] (Figure 1). They differ in their type of linkage (amide or carbamate) and the presence/absence of a stabilizing methyl group at the double bond. Kinetic studies using model compounds revealed that a carbamate-linked

• acceptance of the Cp-modified sugar inspired us to develop novel derivatives of glucosamine and galactosamine containing this cyclopropene modification and to explore their behavior in MGE both for membrane-bound and intracellular glycoproteins. Results and Discussion Kinetic studies The second-order rate

• moiety is connected by a carbamate-linkage. All three cyclopropene derivatives easily undergo DAinv reactions. Kinetic studies revealed that the carbamate derivative ManNCyoc has the highest reaction rate, followed by ManNCp and finally ManNCyc with the slowest reaction kinetics. Performing MGE

Olefin metathesis in multiblock copolymer synthesis

• Maria L. Gringolts,
• Yulia I. Denisova,
• Eugene Sh. Finkelshtein and
• Yaroslav V. Kudryavtsev

Beilstein J. Org. Chem. 2019, 15, 218–235, doi:10.3762/bjoc.15.21

• introduced into NB copolymer blocks by the cross metathesis of poly(5-trimethylsilylnorbornene) with PCOE [89]. Kinetic studies demonstrated that a substituent in the NB monomer units considerably lowers the MCM rate. The introduction of hydroxy groups into COE units of a NB–COE copolymer met certain

• copolymers reveal the ability to self-assemble into ordered structures, enhanced mechanical properties, and nontrivial crystalline and thermal characteristics. Recent kinetic studies with the use of in situ and ex situ NMR have shed some light on the regularities of the macromolecular cross-metathesis

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

• . Therefore, trisubstituted alkenes work best with the same catalysts used for E-alkenes (e.g., Ru-7, Ru-8 and Ru-9). 3 Kinetic studies Grubbs studied the kinetic behavior of several Ru-dithiolate catalysts [6][14][15]. In a typical study the disappearance of the benzylidene proton of the ruthenium complex

Revisiting ring-degenerate rearrangements of 1-substituted-4-imino-1,2,3-triazoles

• James T. Fletcher,
• Matthew D. Hanson,
• Joseph A. Christensen and
• Eric M. Villa

Beilstein J. Org. Chem. 2018, 14, 2098–2105, doi:10.3762/bjoc.14.184

• four imine products via a dynamic equilibrium of condensation, rearrangement and hydrolysis steps. Kinetic studies utilizing 1-(4-nitrophenyl)-1H-1,2,3-triazole-4-carbaldehyde with varying amines showed rearrangement rates sensitive to both steric and electronic factors. Such measurements were

Phosphodiester models for cleavage of nucleic acids

• Satu Mikkola,
• Tuomas Lönnberg and
• Harri Lönnberg

Beilstein J. Org. Chem. 2018, 14, 803–837, doi:10.3762/bjoc.14.68

• in mechanistic studies of small molecular phosphodiester models. Kinetic studies over a wide pH-range allow division of observed rate constants to contributions of different ionic forms and, hence, the upper limit for the effect of protonation or deprotonation of a particular atom on the rate is

• of the catalyst to the phosphate group [27][38]. Dinucleoside-3´,5´-monophosphates are obvious small molecular models with which to study the cleavage of phosphodiester linkages in nucleic acids. Kinetic studies with these compounds are, however, somewhat laborious, since HPLC chromatography has to

• stereochemical course of enzymatic reactions and stereochemical requirements for Mg2+ binding. That is why, comparative kinetic studies with phosphorothioate analogs of phosphodiesters are of interest. Bridging 3´S-substitution accelerates the hydroxide-ion-catalyzed cleavage of the phosphodiester linkage

Mannich base-connected syntheses mediated by ortho-quinone methides

• Petra Barta,
• Ferenc Fülöp and
• István Szatmári

Beilstein J. Org. Chem. 2018, 14, 560–575, doi:10.3762/bjoc.14.43

• phenolic Mannich bases bearing functional groups that are suitable for cross-linking DNA; therefore, their antitumor effects could also be confirmed [96]. The formation of o-QMs and their biological properties were also illustrated by kinetic studies. Rokita et al. using laser flash photolysis showed that

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation. Part 1: Use of CF₃SO₂Na

• Hélène Guyon,
• Hélène Chachignon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2764–2799, doi:10.3762/bjoc.13.272

• in good yields from a variety of di- and trisubstituted alkenes (Scheme 17). Labelling and IR experiments were conducted to investigate the reaction mechanism as well as kinetic studies that revealed the reaction rate dependence on O2 diffusion. A case of intramolecular oxytrifluoromethylation of

A Brønsted base-promoted diastereoselective dimerization of azlactones

• Danielle L. J. Pinheiro,
• Gabriel M. F. Batista,
• Pedro P. de Castro,
• Leonã S. Flores,
• Gustavo F. S. Andrade and
• Giovanni W. Amarante

Beilstein J. Org. Chem. 2017, 13, 2663–2670, doi:10.3762/bjoc.13.264

• into this kind of transformation, we carried out some kinetics experiments. Taking into account the dimerization kinetic studies suggested by Mazurkiewicz et al. and experiments by NMR spectroscopy, we report here kinetic studies revealing mechanistic features on the dimerization reaction catalyzed by

Main group mechanochemistry

• Agota A. Gečiauskaitė and
• Felipe García

Beilstein J. Org. Chem. 2017, 13, 2068–2077, doi:10.3762/bjoc.13.204

• either as a matrix or a dopant, for catalytic applications [75][76]; and (iii) MOFS containing alkaline earth metals [77][78]. Of particular note are the high yielding syntheses of non-solvated AlH3 from LiAlH4 and AlCl3 under mild conditions, and kinetic studies on the synthesis of alkaline-earth metal

Grip on complexity in chemical reaction networks

• Albert S. Y. Wong and
• Wilhelm T. S. Huck

Beilstein J. Org. Chem. 2017, 13, 1486–1497, doi:10.3762/bjoc.13.147

• were determined from kinetic studies in isolated individual reactions, allowing accurate simulations to test specific details of the experiments. We used the model to vary the rate constant that is induced by the changes to the molecular structure. First we show in Figure 7b that the tuning of R1

NMR reaction monitoring in flow synthesis

• M. Victoria Gomez and
• Antonio de la Hoz

Beilstein J. Org. Chem. 2017, 13, 285–300, doi:10.3762/bjoc.13.31

• of one or other method could be crucial. In this regard, flow NMR gives more accurate results for kinetic studies, while static NMR is suitable to obtain structural information and determination of the mechanism. The NMR instrument should also be evaluated considering that high-resolution NMR

• to analyze NMR (via Labview software) data and optimize the reaction conditions. They performed a range of reactions including imine formation (Figure 14), electrophilic fluorinations and Diels–Alder reactions. This system was employed to perform kinetic studies, in-line structural characterization

Self-optimisation and model-based design of experiments for developing a C–H activation flow process

• Alexander Echtermeyer,
• Yehia Amar,
• Jacek Zakrzewski and
• Alexei Lapkin

Beilstein J. Org. Chem. 2017, 13, 150–163, doi:10.3762/bjoc.13.18

• system was generated. The approach of using automated flow experiments in combination with MBDoE allows to minimise experimental effort compared to classical kinetic studies, but results in a process model that can be directly used in optimisation. This approach is clearly preferred for the cases when a

Diels–Alder reactions of myrcene using intensified continuous-flow reactors

• Christian H. Hornung,
• Miguel Á. Álvarez-Diéguez,
• Thomas M. Kohl and
• John Tsanaktsidis

Beilstein J. Org. Chem. 2017, 13, 120–126, doi:10.3762/bjoc.13.15

• conditions and reagent compositions for each batch experiment can be found in Table 1 and Table 2. For kinetic studies, small samples of the reaction mixture for 1H NMR were withdrawn through the septum of the microwave reactor glass vial using a syringe. For this the microwave reaction was stopped at

• conditions and reagent compositions for each experiment in the plate-type flow reactor can be found in Table 3. Kinetic studies of the Diels–Alder reaction between myrcene (1) and acrylic acid (2b); a) for different solvents and temperatures, ratio of myrcene to acrylic acid: 0.9; b) for different starting

Organometallic chemistry

• Bernd F. Straub,
• Rolf Gleiter,
• Claudia Meier and
• Lutz H. Gade

Beilstein J. Org. Chem. 2016, 12, 2216–2221, doi:10.3762/bjoc.12.213

• improved understanding of this industrially important process was achieved by a combination of ligand design for the rhodium catalysts, kinetic studies, and high-level quantum-chemical calculations [126][135][142][145][146][152][155]. In 2006, he initiated the foundation of the “Catalysis Research

Enantioconvergent catalysis

• Justin T. Mohr,
• Jared T. Moore and
• Brian M. Stoltz

Beilstein J. Org. Chem. 2016, 12, 2038–2045, doi:10.3762/bjoc.12.192

• ]. The observed product arises from hydrolysis of each enantiomer of epoxide at the S-configured carbon atom. Isotopic labeling studies with 18OH2 not only confirmed this mechanistic hypothesis, but also facilitated kinetic studies to determine relative rate constants for each of the four reaction

Biosynthesis of oxygen and nitrogen-containing heterocycles in polyketides

• Franziska Hemmerling and
• Frank Hahn

Beilstein J. Org. Chem. 2016, 12, 1512–1550, doi:10.3762/bjoc.12.148

• and was verified by mutagenesis and kinetic studies. In the active site, Glu141 and His129 activate the C3 keto group by protonation. The pro-S hydride of the reduced nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) is then transferred to the C3. The resulting hydroxy group participates in the

On the mechanism of imine elimination from Fischer tungsten carbene complexes

• Philipp Veit,
• Christoph Förster and
• Katja Heinze

Beilstein J. Org. Chem. 2016, 12, 1322–1333, doi:10.3762/bjoc.12.125

• ) followed by detailed mechanistic studies regarding the formation of imine E-3 are presented including mass spectrometric, NMR, IR and UV–vis spectroscopic kinetic studies in combination with (TD)-DFT methods. Results and Discussion Synthesis of W(CO)5(E-2) The diferrocenyl NH carbene complex W(CO)5(E-2) is

• pentacarbonyl tungsten complex W(CO)5(E-2) was investigated by density functional theory methods and mechanistic experimental studies (NMR, IR, UV–vis spectroscopy, FD mass spectrometry, kinetic studies, trapping of intermediates). All available data support the initial dissociation of a CO ligand to give the

Conjugate addition–enantioselective protonation reactions

• James P. Phelan and
• Jonathan A. Ellman

Beilstein J. Org. Chem. 2016, 12, 1203–1228, doi:10.3762/bjoc.12.116

• NaCl/D2O, α-deuterated products could be obtained in similar enantiomeric ratios as the α-protonated products. Luo and Cheng went on to further investigate this reaction using kinetic studies and DFT calculations [53][60]. Based on their studies, they proposed TS-141 involving a water molecule

A cross-metathesis approach to novel pantothenamide derivatives

• Jinming Guan,
• Matthew Hachey,
• Lekha Puri,
• Vanessa Howieson,
• Kevin J. Saliba and
• Karine Auclair

Beilstein J. Org. Chem. 2016, 12, 963–968, doi:10.3762/bjoc.12.95

• visible growth inhibition was observed for E. coli or S. aureus in the presence of compound 16 (up to 512 μM). To determine if the lack of activity was due to poor target affinity or cell-permeability issues, kinetic studies with purified E. coli PanK were performed as previously reported [28]. Compound