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

Muraymycin nucleoside-peptide antibiotics: uridine-derived natural products as lead structures for the development of novel antibacterial agents

• Daniel Wiegmann,
• Stefan Koppermann,
• Marius Wirth,
• Giuliana Niro,
• Kristin Leyerer and
• Christian Ducho

Beilstein J. Org. Chem. 2016, 12, 769–795, doi:10.3762/bjoc.12.77

• for a long time [64][65], the structure of the MraY protein remained unclear. The mechanism of the MraY-catalysed reaction was investigated by kinetic studies by Heydanek, Neuhaus et al. in the 1960s. They proposed a two-step mechanism for lipid I formation that was later revised (Figure 6A) [55][66

Amino-functionalized (meth)acryl polymers by use of a solvent-polarity sensitive protecting group (Br-t-BOC)

• Helmut Ritter,
• Monir Tabatabai and
• Markus Herrmann

Beilstein J. Org. Chem. 2016, 12, 245–252, doi:10.3762/bjoc.12.26

• -substituted carbon atom to fulfill the nucleophilic intramolecular displacement could be expected (Scheme 4). The kinetic studies of 3a, 6a and 7a are shown in Figure 4. Additionally, Figure 5 shows the 1H NMR spectra of homopolymer 6a and deprotected polymer 8a. The calculated t0.5 and t0.3 values of

• in polar solvents. 300 MHz 1H NMR spectrum of 3a in CDCl3. 300 MHz 1H NMR spectrum of 3b in CDCl3. Kinetic studies of the deprotection of 3a, 6a and 7a. 300 MHz 1H NMR spectra of a) 6a in CDCl3 and b) 8a in DMSO-d6. Synthesis of Br-t-Boc-protected monomers 3a,b and homopolymers 6a,b. Stability of 3

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

• species and calibrated accordingly. Through these kinetic studies, it is clear that the allyl chloride 2a system fails because the starting material dimerises to give 11 as the major reaction product (60% isolated yield – 30 mol % by NMR) (Figure 2). This is consistent with the observed ≈100% conversion

• provide a full mechanistic rationalization of these reactions. It is also not immediately obvious how to improve yields and enantiomeric excesses. The kinetic studies suggest that the two reactions work through very different mechanisms and it strikes us as remarkable how both systems give roughly the

• respectable levels of ee (≈83% ee) were developed. Unfortunately, the yields were poor in both cases. Kinetic studies were performed to help to understand the difficulties associated with these reactions. While we were not able to resolve the issues of yield in these studies, this work reveals remarkable

Cross-metathesis of polynorbornene with polyoctenamer: a kinetic study

• Yulia I. Denisova,
• Maria L. Gringolts,
• Alexander S. Peregudov,
• Liya B. Krentsel,
• Ekaterina A. Litmanovich,
• Arkadiy D. Litmanovich,
• Eugene Sh. Finkelshtein and
• Yaroslav V. Kudryavtsev

Beilstein J. Org. Chem. 2015, 11, 1796–1808, doi:10.3762/bjoc.11.195

• corresponding experimental NMR data plotted in Figure 6. Qualitatively, it means that the cleavage of a polymeric double C=C bond is about an order of magnitude more probable in the reaction with a polymer-bound Ru-carbene than with a [Ru]=CHPh carbene. Further kinetic studies on that issue are needed to get

Engineering Pichia pastoris for improved NADH regeneration: A novel chassis strain for whole-cell catalysis

• Martina Geier,
• Christoph Brandner,
• Gernot A. Strohmeier,
• Mélanie Hall,
• Franz S. Hartner and
• Anton Glieder

Beilstein J. Org. Chem. 2015, 11, 1741–1748, doi:10.3762/bjoc.11.190

• twice with 400 µL ethyl acetate containing 50 mM n-butanol as internal standard for the determination of acetoin conversions. The combined organic phases were dried over Na2SO4 and subjected to GC-FID analyses as described below. Kinetic studies of biotransformations Biotransformations in shake flasks

Preparative semiconductor photoredox catalysis: An emerging theme in organic synthesis

• David W. Manley and
• John C. Walton

Beilstein J. Org. Chem. 2015, 11, 1570–1582, doi:10.3762/bjoc.11.173

• carboxylic acids RCO2H release radicals (R•) in the photo-Kolbé reaction was referred to above. Ni and co-workers showed that vinyl acetate polymerization could be mediated by TiO2 nanoparticle photocatalyzed reactions with carboxylic acids [50]. Kinetic studies established that amongst simple carboxylic

Synthesis of γ-hydroxypropyl P-chirogenic (±)-phosphorus oxide derivatives by regioselective ring-opening of oxaphospholane 2-oxide precursors

• Iris Binyamin,
• Shoval Meidan-Shani and
• Nissan Ashkenazi

Beilstein J. Org. Chem. 2015, 11, 1332–1339, doi:10.3762/bjoc.11.143

• between apical to equatorial positions (a and b) [20]. Notably, some selectivity could be obtained once the P center of the phospholane is ligated to two different heteroatoms (i.e., O, N or O, S) [22][23][24][25][26][27], albeit, both the P–O and the P–N bonds are susceptible to cleavage. Kinetic studies

New depsidones and isoindolinones from the mangrove endophytic fungus Meyerozyma guilliermondii (HZ-Y₂) isolated from the South China Sea

• Senhua Chen,
• Zhaoming Liu,
• Yayue Liu,
• Yongjun Lu,
• Lei He and
• Zhigang She

Beilstein J. Org. Chem. 2015, 11, 1187–1193, doi:10.3762/bjoc.11.133

• exhibited strong α-glucosidase inhibitory activity with IC50 values ranging from 2.1 to 13.3 μM. Moreover, kinetic studies of compounds 2 and 6 showed that both of them were noncompetitive inhibitors of α-glucosidase. Keywords: endophytic fungus; depsidone; α-glucosidase inhibitory activity; isoindolinone

• -glucosidase inhibitory activity, while the methyl group at C-3′ did not affect that activity. Moreover, kinetic studies of compounds 2 and 6 showed that both of them were noncompetitive inhibitors of α-glucosidase (Figure 4). Compound 7 showed the promising α-glucosidase inhibitory activity, whereas compound

New palladium–oxazoline complexes: Synthesis and evaluation of the optical properties and the catalytic power during the oxidation of textile dyes

• Rym Hassani,
• Mahjoub Jabli,
• Yakdhane Kacem,
• Jérôme Marrot,
• Damien Prim and
• Béchir Ben Hassine

Beilstein J. Org. Chem. 2015, 11, 1175–1186, doi:10.3762/bjoc.11.132

• evidence of the kinetic studies and the literature data, we propose the mechanistic pathway depicted in Scheme 4. The first step involves the complexation of the azo dye to palladium(II) hydroperoxide 13, followed by a peroxymetalation of the azo moiety. This then affords the pseudocyclic five membered

Hetero-Diels–Alder reactions of hetaryl and aryl thioketones with acetylenic dienophiles

• Grzegorz Mlostoń,
• Paulina Grzelak,
• Maciej Mikina,
• Anthony Linden and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2015, 11, 576–582, doi:10.3762/bjoc.11.63

• preparation of diverse sulfur heterocycles [1][2][3]. Studies performed by Huisgen and coworkers are of special importance and they resulted in the formulation of the name ‘superdipolarophiles’ for aromatic thioketones [4][5][6]. In addition, Sauer and coworkers called them ‘superdienophiles’ based on kinetic

• studies [7][8]. Moreover, thiobenzophenone (1a) was reported to react as a heterodiene smoothly with cyclooctyne, dicyanoacetylene, and dimethyl acetylenedicarboxylate (2a) to give [4 + 2] cycloadducts of type 3a, which spontaneously rearrange via a 1,3-hydrogen shift yielding rearomatized products of

First chemoenzymatic stereodivergent synthesis of both enantiomers of promethazine and ethopropazine

• Paweł Borowiecki,
• Daniel Paprocki and
• Maciej Dranka

Beilstein J. Org. Chem. 2014, 10, 3038–3055, doi:10.3762/bjoc.10.322

• the reaction progress of each of the chosen lipases in general, comprehensive kinetic studies were assessed (Figure 1). Effect of the reaction time on the conversion degree of phenothiazinic alcohol (±)-3 and the overall progress of the followed enzymatic process was estimated by high-performance

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

• methanol in the presence of various dendrimers [103]. A number of kinetic studies have been conducted on the photodegradation of RF and FMF in aqueous media at various pH values [17][23][24][25][26][27][28][29][30][31][32][33][34][35]. The quality of water also affects the rate of photodegradation of RF as

Comparing kinetic profiles between bifunctional and binary type of Zn(salen)-based catalysts for organic carbonate formation

• Carmen Martín and
• Arjan W. Kleij

Beilstein J. Org. Chem. 2014, 10, 1817–1825, doi:10.3762/bjoc.10.191

• opposed to the binary catalyst that is connected with a first-order dependence on the catalyst concentration and a monometallic mechanism. Keywords: CO2 chemistry; cyclic carbonates; kinetic studies; salen complexes; zinc; Introduction Carbon dioxide may be regarded as an ideal, renewable carbon feed

• studies involving kinetic measurements have also been undertaken with the aim to obtain more insight into the operating mechanism [15][37][38][39][40][41][42][43][44][45]. Prominent among these studies is the work carried out by North and co-workers [15][39] who described kinetic studies of a binary

• are the efforts from Coates and co-workers [44] and the kinetic studies described by the group of Williams [45]. In each of these latter cases a binuclear mechanism was proposed for the copolymerization reaction of CO2 and epoxide, establishing a second-order dependence for mononuclear Zn complex 7

A convenient enantioselective decarboxylative aldol reaction to access chiral α-hydroxy esters using β-keto acids

• Zhiqiang Duan,
• Jianlin Han,
• Ping Qian,
• Zirui Zhang,
• Yi Wang and
• Yi Pan

Beilstein J. Org. Chem. 2014, 10, 969–974, doi:10.3762/bjoc.10.95

• did not improve in the cases of methyl, isopropyl or benzyl esters (Table 2, entries 2–4). The mechanism of the reaction was proposed based on the kinetic studies of the malonic acid half thioester system by Shair [33]. Essentially β-keto acids can undergo decarboxylation or deprotonation to generate

Chromatographically separable rotamers of an unhindered amide

• Mario Geffe,
• Lars Andernach,
• Oliver Trapp and
• Till Opatz

Beilstein J. Org. Chem. 2014, 10, 701–706, doi:10.3762/bjoc.10.63

• were separated by HPLC and their reequilibration was followed with the same technique. Kinetic studies The kinetic studies were performed at 20 °C on a Knauer normal-phase HPLC (see Supporting Information File 1 for details) using hexane/2-propanol 80:20 as mobile phase. Each rotamer was collected

Synthesis, characterization and initial evaluation of 5-nitro-1-(trifluoromethyl)-3H-1λ³,2-benziodaoxol-3-one

• Nico Santschi,
• Roman C. Sarott,
• Elisabeth Otth,
• Reinhard Kissner and
• Antonio Togni

Beilstein J. Org. Chem. 2014, 10, 1–6, doi:10.3762/bjoc.10.1

• kinetic studies showed that this new derivative is almost one order of magnitude more reactive. Furthermore, differential scanning calorimetry measurements indicated that, in addition, it is also safer to handle. Keywords: cyclic voltammetry; differential scanning calorimetry; electrophilic

Advancements in the mechanistic understanding of the copper-catalyzed azide–alkyne cycloaddition

• Regina Berg and
• Bernd F. Straub

Beilstein J. Org. Chem. 2013, 9, 2715–2750, doi:10.3762/bjoc.9.308

• can be further advanced by kinetic studies and the isolation and characterization of key intermediates. Keywords: alkyne; azide; Click; copper; CuAAC; DFT study; Huisgen–Meldal–Sharpless cycloaddition; kinetics; reaction mechanism; Introduction In 1893, Michael discovered a reaction between dimethyl

• stable towards aqueous conditions, and the procedures can hardly be modulated according to specific requirements. As for mechanistic investigations, the nature of the catalytically active copper(I) complex is unknown and there is scarcely any chance to rationally explain the results of kinetic studies

• the reaction or have no effect on its rate. The rational explanation for this behaviour together with a mechanistic proposal for CuAAC reactions with this family of ligands is presented in this review’s section on kinetic studies. In one of their first investigations regarding the influence of

New developments in gold-catalyzed manipulation of inactivated alkenes

• Michel Chiarucci and
• Marco Bandini

Beilstein J. Org. Chem. 2013, 9, 2586–2614, doi:10.3762/bjoc.9.294

• ligand 53 and AgBF4 was used in combination with alcoholic additives, the rate of the intramolecular hydroamination of 52 increased considerably, leading to the concomitant formation of 55 in combination with the expected product 54. A screening of various chiral alcohols and kinetic studies established

Temperature measurements with two different IR sensors in a continuous-flow microwave heated system

• Jonas Rydfjord,
• Fredrik Svensson,
• Magnus Fagrell,
• Jonas Sävmarker,
• Måns Thulin and
• Mats Larhed

Beilstein J. Org. Chem. 2013, 9, 2079–2087, doi:10.3762/bjoc.9.244

• model found during the calibration to show the internal temperature. This is also our recommendation in general if knowledge of the exact temperature is of importance e.g for kinetic studies. Finally, recommending one type of IR sensor is not trivial, as both have their advantages and disadvantages; IR