Unexpected polymorphism during a catalyzed mechanochemical Knoevenagel condensation

• Sebastian Haferkamp,
• Andrea Paul,
• Adam A. L. Michalchuk and
• Franziska Emmerling

Beilstein J. Org. Chem. 2019, 15, 1141–1148, doi:10.3762/bjoc.15.110

• ] in understanding reaction kinetics of these processes. Early insight into formation pathways was provided ex situ, in which the mechanical treatment was stopped, and powder removed for analysis [10][11]. More recently, further detail has been gained by monitoring mechanochemical transformations in

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

• supplied into the sample, the process rate is limited by the diffusion, and the oxidation takes place in a diffusion mode. The reaction kinetics is consecutive and hence, it is characterized by a wide range of rate constants and can be described by the following equation: where the first element on the

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

• reaction kinetics and their labeling intensities after metabolic incorporation. To determine the efficiencies by which the derivatives are metabolized to sialic acids, we synthesized and investigated the corresponding cyclopropane derivatives because cyclopropenes are not stable under the analysis

• norbornenes, have high DAinv reaction kinetics, but suffer from low incorporation efficiencies [21]. Cyclopropenes, that combine fast reaction kinetics and small size, turned out to be excellent reporters for application in MGE [22][23][24][25][26][27]. Three cyclopropene-derivatized mannosamine derivatives

• 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

• sufficient to carry out the process effectively [86][87]. In the PBD–polyisoprene (PI) cross metathesis, Gr1 can be replaced by Gr–H1 but longer reaction times are needed [87]. A control over the reaction kinetics can be sometimes complicated because the overall composition of a polymer mixture does not

Computational characterization of enzyme-bound thiamin diphosphate reveals a surprisingly stable tricyclic state: implications for catalysis

• Ferran Planas,
• Michael J. McLeish and
• Fahmi Himo

Beilstein J. Org. Chem. 2019, 15, 145–159, doi:10.3762/bjoc.15.15

• catalytically inactive tricyclic state. Conversely, the inhibitor binding greatly destabilized the ylide formation. Together, these observations have significant implications for the reaction kinetics of the ThDP-dependent enzymes, and, potentially, for the use of unnatural substrates in such reactions

Selective ring-opening metathesis polymerization (ROMP) of cyclobutenes. Unsymmetrical ladderphane containing polycyclobutene and polynorbornene strands

• Yuan-Zhen Ke,
• Shou-Ling Huang,
• Guoqiao Lai and
• Tien-Yau Luh

Beilstein J. Org. Chem. 2019, 15, 44–51, doi:10.3762/bjoc.15.4

• examined the first order reaction kinetics of ROMPs of 4 and of 5 in the presence of 10 mol per cent of Grubbs first generation catalyst (6) [36] in DCM at 10 °C [37]. The rate constants for the reactions of 4 and 5 were 1.3 × 10−3 and 5.1 × 10−4 s−1, respectively. On the other hand, when the reaction was

A general and atom-efficient continuous-flow approach to prepare amines, amides and imines via reactive N-chloramines

• Katherine E. Jolley,
• Michael R. Chapman and
• A. John Blacker

Beilstein J. Org. Chem. 2018, 14, 2220–2228, doi:10.3762/bjoc.14.196

• provide a tres for optimal conversion. This was achieved according to reaction kinetics and hydrophobicity of the amine, which affects its partition between phases. Herein, we report improvements to this process and the use of N-alkyl-N-chloramine in subsequent continuous-flow reactions (Figure 1). These

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

• colorimetric indicator byproduct encouraged its use in a reaction kinetics investigation, where both electronic and steric properties of the amine reactant were shown to influence rearrangement rates. Having demonstrated its utility in studying this reaction using a high-throughput assay, it is proposed that 1

Investigating radical cation chain processes in the electrocatalytic Diels–Alder reaction

• Yasushi Imada,
• Yohei Okada and
• Kazuhiro Chiba

Beilstein J. Org. Chem. 2018, 14, 642–647, doi:10.3762/bjoc.14.51

• reaction kinetics. However, the observed induction period indicated that this was not the case and an intermediate(s) was involved in the rate determining step. This mechanism could be rationalized on the basis of a radical cation chain process since the concentrations of both starting trans-anethole (1

The effect of milling frequency on a mechanochemical organic reaction monitored by in situ Raman spectroscopy

• Patrick A. Julien,
• Ivani Malvestiti and
• Tomislav Friščić

Beilstein J. Org. Chem. 2017, 13, 2160–2168, doi:10.3762/bjoc.13.216

• reactivity on small variations in milling frequency. In particular, in situ measurements revealed the establishment of two different regimes of reaction kinetics at different frequencies, providing tentative insight into processes of mechanical activation in organic mechanochemical synthesis. Keywords

• mechanochemical synthesis of a MOF from ZnO and imidazole in the presence of a small amount of N,N-dimethylformamide [41]. This study revealed reaction kinetics consistent with a 2nd order reaction rate law, rationalized through a “pseudo-fluid” reaction model in which the rate-determining factor is the frequency

• , they might be relevant for the observed variation of reaction kinetics with milling frequency, especially as a recent variable-temperature in situ PXRD study has demonstrated that mechanochemical reaction rates can be highly sensitive to temperature [52]. Conclusion In conclusion, we have utilized an

Framing major prebiotic transitions as stages of protocell development: three challenges for origins-of-life research

• Ben Shirt-Ediss,
• Sara Murillo-Sánchez and
• Kepa Ruiz-Mirazo

Beilstein J. Org. Chem. 2017, 13, 1388–1395, doi:10.3762/bjoc.13.135

• devoted to control division processes. Challenge 3: characterizing the evolutionary dynamics of pre-Darwinian protocells. Rather than focusing on the reaction kinetics and evolutionary dynamics of populations of naked nucleic acid molecules (the core idea underlying the ‘RNA world’ hypothesis), or even

Sugar-based micro/mesoporous hypercross-linked polymers with in situ embedded silver nanoparticles for catalytic reduction

• Qing Yin,
• Qi Chen,
• Li-Can Lu and
• Bao-Hang Han

Beilstein J. Org. Chem. 2017, 13, 1212–1221, doi:10.3762/bjoc.13.120

• , the absorption peak at 400 nm disappeared, implying full conversion of 4-NP to 4-AP. The reaction kinetics of the reduction of 4-NP is considered to be pseudo-first order [48] and can be expressed by the following equation: where rt is the consumption rate of 4-NP at time t, ct is the concentration

Towards open-ended evolution in self-replicating molecular systems

• Herman Duim and
• Sijbren Otto

Beilstein J. Org. Chem. 2017, 13, 1189–1203, doi:10.3762/bjoc.13.118

• formation of the TCD template. 2.3 Reaction kinetics and its implications When considering a mixture containing only building blocks A and B in the minimal replicator model (Figure 2), the formation of template molecules T can initially only take place via the bimolecular reaction pathway. The bimolecular

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

• -pressure and thus adjusts the system pressure. In this way a new kinetic model could be developed for this reaction taking into consideration a wide range of temperatures and pH values. The results obtained extend the knowledge of the reaction kinetics for this industrially important system. Similarly

• and, before entering the NMR flow probe, the sample was filtered and the volume selected with a split valve. In order to estimate the equilibrium time the authors performed dilutions using a micromixer prior to the NMR probe. In this way, it was possible to elucidate the reaction kinetics of the

• and Sons. Flowsheet of the experimental setup used to study the reaction kinetics of the oligomer formation in mixtures of acetaldehyde (AA) and water (A) (Flow rates VAA 254 μL min−1 and VW 748 μL min−1). Reproduced with permission from reference [46]. Copyright 2014 The American Chemical Society

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

• the preferable reaction kinetics of the acrylic acid–myrcene system. Table 2 presents a set of experiments using this system, at different process conditions and in different solvents; samples were analyzed over time in order to establish kinetic profiles of these reactions. Figure 1 shows the kinetic

Inhibition of peptide aggregation by means of enzymatic phosphorylation

• Kristin Folmert,
• Malgorzata Broncel,
• Hans v. Berlepsch,
• Christopher H. Ullrich,
• Mary-Ann Siegert and
• Beate Koksch

Beilstein J. Org. Chem. 2016, 12, 2462–2470, doi:10.3762/bjoc.12.240

• soluble structures, as no further precipitation was observed. It remains unclear whether the decreasing effect of the phosphorylation during later stages of the aggregation is due to the lower flexibility of the recognition site, leading to slow reaction kinetics of the enzyme or to the competitive

Rearrangements of organic peroxides and related processes

• Ivan A. Yaremenko,
• Vera A. Vil’,
• Dmitry V. Demchuk and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

• ketones [199]. There are thousands of publications on the Baeyer–Villiger reaction. In the latest reviews published by Krow [195] in 1993 and by Renz and Meunier [185] in 1999, the field of application, the reactivity of substrates, and the reaction kinetics and mechanisms are considered in detail. In the

Copper-catalysed asymmetric allylic alkylation of alkylzirconocenes to racemic 3,6-dihydro-2H-pyrans

• Emeline Rideau and
• Stephen P. Fletcher

Beilstein J. Org. Chem. 2015, 11, 2435–2443, doi:10.3762/bjoc.11.264

• 5.0 equiv), in specified solvent (2.0 mL), room temperature. ee determined by HPLC. For more information on the procedures see Supporting Information File 1. ● (wave 1, entries 1–17), ♦ (wave 2, entries 18–30), ▼ (wave 3, entries 31–38). Reaction kinetics as monitored by in situ 1H NMR spectroscopy

• from 3-chloro-3,6-dihydro-2H-pyran (2a). Reaction kinetics as monitored by in situ 1H NMR spectroscopy from 3,6-dihydro-2H-pyran-3-yl diethyl phosphate (2d). Kinetic ee analysis using 2a. ee of reaction with 3-chloro-3,6-dihydro-2H-pyran (2a) as measured by removing aliquots in time. Kinetic ee

Profluorescent substrates for the screening of olefin metathesis catalysts

• Raphael Reuter and
• Thomas R. Ward

Beilstein J. Org. Chem. 2015, 11, 1886–1892, doi:10.3762/bjoc.11.203

• chemical biologists. Since microplates are a very common and practical tool for biological applications, we developed a screening assay in 96-well plate format to quickly evaluate the reaction kinetics of different commercially available metathesis catalysts. Since fluorescence spectroscopy is a highly

Structure and conformational analysis of spiroketals from 6-O-methyl-9(E)-hydroxyiminoerythronolide A

• Ana Čikoš,
• Irena Ćaleta,
• Dinko Žiher,
• Mark B. Vine,
• Ivaylo J. Elenkov,
• Marko Dukši,
• Dubravka Gembarovski,
• Marina Ilijaš,
• Snježana Dragojević,
• Ivica Malnar and
• Sulejman Alihodžić

Beilstein J. Org. Chem. 2015, 11, 1447–1457, doi:10.3762/bjoc.11.157

• spectroscopy and molecular modelling. The reaction kinetics and mechanistic aspects of this transformation are discussed. These rearrangements provide a facile synthesis of novel macrolide scaffolds. Keywords: configuration; conformation; 6-O-methyl-9(E)-hydroxyiminoerythronolide A; reaction mechanism

• , translactonisation or formation of anhydroerythromycin A, perhaps resulting from acetic acid traces generated during the reaction acting upon either the starting material, or deoximation of the intended product. We therefore repeated the experiment in fresh, stabilised chloroform to study the reaction kinetics and

• between the two suggests that both compounds share the same configuration. Reaction kinetics Dissolution in fresh stabilised CDCl3 showed no evidence of change, suggesting that observed transformations were caused by acidic species arising from chloroform decomposition. It was shown [16][23][60] that

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

• and above pH 5.4 when heated at 121–123 °C for 1 hour [150][151]. Thermal studies have also been carried out on the degradation products of RF such as FMF and LF in order to better understand the reaction kinetics [79][163]. FMF when heated at 40–60 °C in acidic solutions in the dark undergoes thermal

Continuous flow nitration in miniaturized devices

• Amol A. Kulkarni

Beilstein J. Org. Chem. 2014, 10, 405–424, doi:10.3762/bjoc.10.38

One-step synthesis of pyridines and dihydropyridines in a continuous flow microwave reactor

• Mark C. Bagley,
• Vincenzo Fusillo,
• Robert L. Jenkins,
• M. Caterina Lubinu and
• Christopher Mason

Beilstein J. Org. Chem. 2013, 9, 1957–1968, doi:10.3762/bjoc.9.232

• provides improvements in reaction kinetics and processing rate. Finally the improved performance of flow processing in this transformation was validated by a larger scale (15 mmol) microwave-assisted batch reaction in a 60 mL Teflon vessel using a commercial multi-mode instrument (Table 1, entries 8 and 9

Integrating reaction and analysis: investigation of higher-order reactions by cryogenic trapping

• Skrollan Stockinger and
• Oliver Trapp

Beilstein J. Org. Chem. 2013, 9, 1837–1842, doi:10.3762/bjoc.9.214

• direct analytical information about a reaction is obtained, including the formation of by-products and eventually even the reaction kinetics [1][2][3][4]. This information is important to design efficient flow-through experiments and to scale-up a reaction in a continuous process [5][6][7][8][9], which

• reactions, so that the reaction kinetics can be investigated under comparable reaction conditions. So far, we investigated only first-order or pseudo-first-order reactions, where, for example, one reactant is used as a carrier gas, i.e., hydrogen in hydrogenation reactions or hydrogen peroxide as oxidant

3D-printed devices for continuous-flow organic chemistry

• Vincenza Dragone,
• Victor Sans,
• Mali H. Rosnes,
• Philip J. Kitson and
• Leroy Cronin

Beilstein J. Org. Chem. 2013, 9, 951–959, doi:10.3762/bjoc.9.109

• experiments were conducted using 2 M methanolic solutions of the different substrates. This is convenient from a processing point of view, since high concentrations favor increased reaction kinetics [26] whilst minimizing the amount of waste generated during the downstream work-up [27]. The reactor output was