C–C Coupling in sterically demanding porphyrin environments

• Liam Cribbin,
• Brendan Twamley,
• Nicolae Buga,
• John E. O’ Brien,
• Raphael Bühler,
• Roland A. Fischer and
• Mathias O. Senge

Beilstein J. Org. Chem. 2024, 20, 2784–2798, doi:10.3762/bjoc.20.234

• of lower yields experienced for porphyrins 41, 42, and 43 of 4%, 30%, and 10%, respectively. Overall, a general trend of decreased yield moving from the para- to meta-position was observed, also a general increased catalyst concentration was needed for reactivity to occur at the meta-position. Lastly

Ligand effects, solvent cooperation, and large kinetic solvent deuterium isotope effects in gold(I)-catalyzed intramolecular alkene hydroamination

• Ruichen Lan,
• Brock Yager,
• Yoonsun Jee,
• Cynthia S. Day and
• Amanda C. Jones

Beilstein J. Org. Chem. 2024, 20, 479–496, doi:10.3762/bjoc.20.43

• catalyst. With the more reactive Jackiephos-based catalyst 6a, first order dependence on alkene concentration was observed when carbamate 1b concentration was in the 0.03–0.133 M range, but then the rate dropped at 0.24 M carbamate (Figure 7). The impact of catalyst concentration on the cyclization of urea

• alkene 1a (0.05 M, CH2Cl2) was tested with no added MeOH and with 10 μL of added MeOH (Figure 8). The catalyst loading was varied from 0.5 mol % to 2.5 mol %. In the absence of MeOH, the reaction showed a first-order dependence on catalyst concentration. In the presence of MeOH, the dependence was non

• -linear and less than first order in catalyst. The impact of catalyst concentration on cyclization of 1a was also determined in CD3OD (0.05 M) with 2.5, 10 and 20 mol % catalyst 5; first order dependence on catalyst concentration was determined (see Supporting Information File 1, Figure S37). Under the

Friedel–Crafts acylation of benzene derivatives in tunable aryl alkyl ionic liquids (TAAILs)

• Swantje Lerch,
• Stefan Fritsch and
• Thomas Strassner

Beilstein J. Org. Chem. 2023, 19, 212–216, doi:10.3762/bjoc.19.20

• diminished yields, but the loss is rather small compared to the reduced catalyst concentration. To further characterize our catalytic system, the acylation was performed on a larger scale to investigate whether upscaling changes the performance of the catalytic system. Table 3 shows the results of the

Heteroleptic metallosupramolecular aggregates/complexation for supramolecular catalysis

• Prodip Howlader and
• Michael Schmittel

Beilstein J. Org. Chem. 2022, 18, 597–630, doi:10.3762/bjoc.18.62

• a maximum yield of 88% at the highest 30/31 ratio of 24:0. The system was benchmarked with the building unit 30 itself and Ph3PAuCl where they observed a negligible conversion, which points toward the importance of local catalyst concentration. A wide range of cavity-based artificial supramolecular

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

• less active than the primary amine. The authors suggest the reaction occurs through an imine/iminium intermediate as they confirmed a first order relationship between the reaction rate and the catalyst concentration. After washing with nitromethane, the catalyst could be reused a second time, obtaining

Valorisation of plastic waste via metal-catalysed depolymerisation

• Francesca Liguori,
• Carmen Moreno-Marrodán and
• Pierluigi Barbaro

Beilstein J. Org. Chem. 2021, 17, 589–621, doi:10.3762/bjoc.17.53

• examined, showing the critical operational parameters to be temperature and catalyst concentration, whereas the process was not significantly affected by particle size or stirring speed. Thus, up to 100% Me-La yield was obtained using the six-coordinated Zn(ligand)2 complex sketched in Scheme 9a, either at

A method to determine the correct photocatalyst concentration for photooxidation reactions conducted in continuous flow reactors

• Clemens R. Horn and
• Sylvain Gremetz

Beilstein J. Org. Chem. 2020, 16, 871–879, doi:10.3762/bjoc.16.78

• maxima close to the absorption maximum of each catalyst. Keywords: catalyst concentration; channel height; flow chemistry; photooxidation; Introduction The renaissance of photochemistry that occurred over the last decade has been described as “old light through new windows”, and much of this work

• only in 15% of the cases, the catalyst concentration was high enough to absorb all the light at the given wavelength (highlighted with a bold frame, transmission < 1%). Overall, the results show that 1 mol % of the catalyst was not the ideal concentration for the various initiators. For example, in the

• noted that in typical studies on photooxidation reactions, the concentration of the reactants is usually varied, while the catalyst concentration is rarely addressed [24][25][26]. To study the required photocatalyst concentration, we pursued a different approach based on the realization that in a

Photophysics and photochemistry of NIR absorbers derived from cyanines: key to new technologies based on chemistry 4.0

• Bernd Strehmel,
• Christian Schmitz,
• Ceren Kütahya,
• Yulian Pang,
• Anke Drewitz and
• Heinz Mustroph

Beilstein J. Org. Chem. 2020, 16, 415–444, doi:10.3762/bjoc.16.40

• catalyst concentration by continuous regeneration of Cu(I) species using Cu(II) as starting material. These methods include initiators for continuous activator regeneration (ICAR) ATRP, activators regenerated by electron transfer (ARGET) ATRP, supplemental activators and reducing agent (SARA) ATRP, and

• system opens the possibility to synthesize well-defined polymeric materials in a green way due to the photochemical stability, low copper-catalyst concentration and the use of NIR light. Taking advantage of good penetration of NIR light, this approach provides also the opportunity to embed UV absorbing

α,ß-Didehydrosuberoylanilide hydroxamic acid (DDSAHA) as precursor and possible analogue of the anticancer drug SAHA

• Shital K. Chattopadhyay,
• Subhankar Ghosh,
• Sarita Sarkar and
• Kakali Bhadra

Beilstein J. Org. Chem. 2019, 15, 2524–2533, doi:10.3762/bjoc.15.245

• (phenylmethylene)(tricyclohexylphosphine)ruthenium, 9a] in dichloromethane at room temperature provided the CM-product 10a in a moderate yield of 41% within 16 hours. However, raising the catalyst concentration to 5 mol % and employing elevated temperature increased the yield to 56% within 6 hours. Contrarily, the

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

• product powder color decreased from a deep orange to white, with decreasing quantity of catalyst (Figure 2b). Importantly, none of the starting materials are colored, and the color of the product phase was found to vary systematically with increasing catalyst concentration. This coloring was observed

• conditions or catalyst concentration. Multivariate analysis of in situ Raman spectra by both PCA and MCR suggests the formation of a transient product with almost identical spectral properties as the final product, the triclinic polymorph of 3a. These results are consistent with those of XRPD analysis. Hence

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

• ) are the peak intensities related to the alternating dyads. The average block lengths decreased with the conversion, reaction time, and catalyst concentration and asymptotically approached the value of 2, characteristic of a completely random (Bernoullian) equimolar copolymer. Thus, a proper choice of

• the catalyst concentration [84][88]. Another reason for lowering the copolymer molecular mass is related to intramolecular metathesis that leads to low molecular mass cyclooligomers [77], which are lost during isolation of the reaction product. This negative effect can be partially counteracted by

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

• . This will only be due to the substituent effect on the activity of the precatalyst. Effect of catalyst concentration Earlier studies indicated that 80 °C is the optimum temperature for 5d [10][11]. It was therefor decided to investigate the effect of the concentration of the precatalyst on the

N-Arylphenothiazines as strong donors for photoredox catalysis – pushing the frontiers of nucleophilic addition of alcohols to alkenes

• Fabienne Speck,
• David Rombach and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2019, 15, 52–59, doi:10.3762/bjoc.15.5

• transfer as the rate-determining step the substrate concentration was reduced to 42 mM and the catalyst concentration was increased to 10 mol %. This change in the reaction conditions led to a quantitative product formation after 65 h. Finally, the rather long reaction times were addressed by speeding up

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

• (Scheme 1), performed at 20 °C in CD2Cl2 at a catalyst concentration of 4.52 mM and a substrate/catalyst ratio of 200 (0.5 mol % of catalyst), a strong dependence of the catalytic activities on the steric bulkiness of the N-alkyl substituents was observed. Indeed, an increase in the size of the alkyl

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

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

• shows oscillations in Tr activity (with experimental conditions in inset). Adapted with permission from [94], copyright 2015 Nature Publishing Group. Functions obtained by linking multiple network modules in microfluidic flow reactors (depicted as CSTR 1 and 2). In each case, the oscillating catalyst

• concentration [Tr] from CSTR 1 is coupled to another CSTR that contains reagents producing (a) an amplification, (b) analog-to-digital conversion, or (c) a periodic control over equilibrium systems. The respective processes are: trypsin-catalyzed conversion of chymotrypsinogen (ChTg) to chymotrypsin (ChTr

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

• a closed circuit, at a flow rate of 1 mL min−1. The kinetic rate could be studied as a function of the catalyst concentration and good agreement was found with the results obtained by gas chromatography. As expected for a first-order reaction, a linear dependence of the kinetic constant on the

• catalyst concentration was found. An interesting point to consider is the comparison of in-line and off-line analysis. For example, Duchateau et al. [41] described the preparation of Grignard reagents from aryl halides and magnesium using a fluidized bed reactor under continuous-flow conditions. In a

Solvent-free, visible-light photocatalytic alcohol oxidations applying an organic photocatalyst

• Martin Obst and
• Burkhard König

Beilstein J. Org. Chem. 2016, 12, 2358–2363, doi:10.3762/bjoc.12.229

• outside. We started our investigations with the oxidation of 4,4’-dimethoxybenzhydrol (1a) to 4,4’-dimethoxybenzophenone (1b), applying 10% RFTA (Scheme 1). In this initial trial, the product could be obtained in 72% yield. Subsequently, we varied the amount of RFTA (Table 1). Lowering the catalyst

• concentration from 10% to 5% does not significantly influence the yield (entry 2, Table 1, yield in average of four trials). Even a further decrease to 2% (entry 3, Table 1) causes no essential decline. However, at a RFTA concentration of 1% (entry 4, Table 1), the isolated yield was only 61%; very low catalyst

Ionic liquids as transesterification catalysts: applications for the synthesis of linear and cyclic organic carbonates

• Maurizio Selva,
• Alvise Perosa,
• Sandro Guidi and
• Lisa Cattelan

Beilstein J. Org. Chem. 2016, 12, 1911–1924, doi:10.3762/bjoc.12.181

• that the decarboxylation of glycerol carbonate increased with increasing catalyst concentration in solution and thus, the high basicity of the catalyst was not the sole reason for the high activity. This implied that both, the presence of a basic (anionic) center and an electrophilic (cationic) center

The hydrolysis of geminal ethers: a kinetic appraisal of orthoesters and ketals

• Sonia L. Repetto,
• James F. Costello,
• Craig P. Butts,
• Joseph K. W. Lam and
• Norman M. Ratcliffe

Beilstein J. Org. Chem. 2016, 12, 1467–1475, doi:10.3762/bjoc.12.143

• catalyst concentration, i.e., kobs = kH+ [H+]. Nevertheless, we have used the same acid catalyst concentration ([H+] = 2 × 10−4 M) as previous workers [18] except in the case of particularly slow reactions where [H+] was increased to 5 × 10−4 M to ensure completion within a reasonable time. Acyclic

• . Adjustments to the acid catalyst concentration were made on an iterative basis in order to ensure the kinetic runs were complete within reasonable time-scales. Freshly distilled 2 (33 µL, 0.3 mmol) and 6 (38 µL, 0.3 mmol) were added to anhydrous CD3CN (1200 µL), and the resulting solution was divided equally

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

• sensitive technique, we aimed at using a low catalyst concentration (e.g., 100 µM) in a small reaction volume (150 µL). With this format, only 1 mg of catalyst is required to perform fifty to a hundred kinetic experiments. For this proof-of-principle study, we selected four commercially available, second

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

• the decay of primary carbenes due to the reasons other than their interaction with macromolecules. Interaction of PCOE (Mn = 120000 g/mol, Ð = 1.8) with Gr-1 was studied in CDCl3 at the initial polymer/catalyst concentration ratio of 20:1. Note that the initial catalyst concentration found by in situ

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

• was done between the binary catalyst system Zn(salphen)/NBu4I and a bifunctional system Zn(salpyr)·MeI with a built-in nucleophile. The latter system demonstrates an apparent second-order dependence on the bifunctional catalyst concentration and thus follows a different, bimetallic mechanism as

• 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

• may be considered pseudo constant at the initial stage of the reaction. The natural logarithm of the rate law (Equation 2) results in Equation 3, from which is possible to afford the order “c” with respect to the catalyst concentration by examination of a double logarithmic plot. with [cat]c = [Zn]d

Visible-light-induced, Ir-catalyzed reactions of N-methyl-N-((trimethylsilyl)methyl)aniline with cyclic α,β-unsaturated carbonyl compounds

• Dominik Lenhart and
• Thorsten Bach

Beilstein J. Org. Chem. 2014, 10, 890–896, doi:10.3762/bjoc.10.86

• MeOH, however, only the tricyclic product 10 was formed. A slight yield improvement was observed when raising the catalyst loading in the latter case from 1 mol % to 2.5 mol % while a decrease of the catalyst concentration led to lower yields. The results of the reactions under optimized conditions are

Continuous-flow Heck synthesis of 4-methoxybiphenyl and methyl 4-methoxycinnamate in supercritical carbon dioxide expanded solvent solutions

• Phei Li Lau,
• Ray W. K. Allen and
• Peter Styring

Beilstein J. Org. Chem. 2013, 9, 2886–2897, doi:10.3762/bjoc.9.325

• calculated for the reactions of styrene and methyl acrylate with 4-iodoanisole in the 1 mm PFRs in order to normalise with respect to catalyst concentration as the lengths of the reactor and therefore residence times for the same flow rate differed three-fold. The results are shown in Figure 9 and emphasise