Advancements in hydrochlorination of alkenes

• Daniel S. Müller

Beilstein J. Org. Chem. 2024, 20, 787–814, doi:10.3762/bjoc.20.72

• reaction, the protonation of the alkene is the rate-determining step. This process can be viewed as the reaction between a nucleophile (alkene) and an electrophile (proton). According to the Mayr–Patz equation log(k) = s(N + E), the second order reaction rate constant k at 20 °C for a reaction is related

Regioselective quinazoline C2 modifications through the azide–tetrazole tautomeric equilibrium

• Dāgs Dāvis Līpiņš,
• Andris Jeminejs,
• Una Ušacka,
• Anatoly Mishnev,
• Māris Turks and
• Irina Novosjolova

Beilstein J. Org. Chem. 2024, 20, 675–683, doi:10.3762/bjoc.20.61

• reactivity in the SNAr reactions in comparison to polar solvents such as DMSO and DMF. This is explained by solvent hydrogen bond acidity and basicity descriptors α and β, for example, α(DMSO) = 0, β(DMSO) = 0.88, α(MeOH) = 0.43, β(MeOH) = 0.47. The rate constant of the SNAr process escalates with an

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

• , and benzamide 1c (Table 4). Under standard conditions (2.5 mol % [JPhosAu(NCCH3)]SbF6, 0.05 M alkene in DCM) benzamide and carbamate hydroamination were too slow to measure, so the reactions were done with 55 μL MeOH promoter but still only an estimated rate constant was obtained for 1c (14

Optimizing reaction conditions for the light-driven hydrogen evolution in a loop photoreactor

• Pengcheng Li,
• Daniel Kowalczyk,
• Johannes Liessem,
• Mohamed M. Elnagar,
• Dariusz Mitoraj,
• Radim Beranek and
• Dirk Ziegenbalg

Beilstein J. Org. Chem. 2024, 20, 74–91, doi:10.3762/bjoc.20.9

• and reaction rate [42], which was used in this work to fit the experiment results (see Equation 4). where is the average (observed) reaction rate, k* is the kinetic rate constant, θ is the surface coverage of the photocatalyst, α is the optical density, ϕ is the quantum yield, qp is the volumetric

Using the phospha-Michael reaction for making phosphonium phenolate zwitterions

• Matthias R. Steiner,
• Max Schmallegger,
• Larissa Donner,
• Johann A. Hlina,
• Christoph Marschner,
• Judith Baumgartner and
• Christian Slugovc

Beilstein J. Org. Chem. 2024, 20, 41–51, doi:10.3762/bjoc.20.6

• , methanol has a detrimental effect on the reaction velocity as the rate constant (kMeOH = 1.2 mM−1 s−1) is almost halved compared to chloroform. The strong Michael acceptor acrylonitrile reacts only very slowly in chloroform (kCHCl3 = 5.6 × 10−3 mM−1 s−1). In methanol, 2a is formed with a similar rate

• constant (kMeOH = 2.1 mM−1 s−1) as 2b, the product of the poor Michael acceptor acrylamide in CHCl3. The results show no correlation of the rate constant with the electrophilicity parameter of the Michael acceptors. The low rate constant for the acrylonitrile reaction in chloroform suggests that the

Beyond n-dopants for organic semiconductors: use of bibenzo[d]imidazoles in UV-promoted dehalogenation reactions of organic halides

• Kan Tang,
• Megan R. Brown,
• Chad Risko,
• Melissa K. Gish,
• Garry Rumbles,
• Phuc H. Pham,
• Oana R. Luca,
• Stephen Barlow and
• Seth R. Marder

Beilstein J. Org. Chem. 2023, 19, 1912–1922, doi:10.3762/bjoc.19.142

• competitive. In the case of (Cyc-DMBI)2, the second-order rate constant, kET, is estimated as 6.0 × 10−3 M−1 s−1, whereas for (N-DMBI)2, kcl = 4.7 × 10−5 s−1 and kET = 1.0 × 10−2 M−1s−1. The difference in kET values is qualitatively consistent with the peak oxidation potentials, Epa(D2•+/D2), of the two

• dimers; values of −0.06 and −0.13 V vs FeCp2+/0 are found for (Cyc-DMBI)2 and (N-DMBI)2, respectively [18][44], indicating that ET from the former to benzyl bromide is more endergonic than from the latter. The rate constant for (Cyc-DMBI)2-to-BnBr ET is also much smaller than that previously determined

A deep-red fluorophore based on naphthothiadiazole as emitter with hybridized local and charge transfer and ambipolar transporting properties for electroluminescent devices

• Suangsiri Arunlimsawat,
• Patteera Funchien,
• Pongsakorn Chasing,
• Atthapon Saenubol,
• Taweesak Sudyoadsuk and
• Vinich Promarak

Beilstein J. Org. Chem. 2023, 19, 1664–1676, doi:10.3762/bjoc.19.122

• simple mix-up of the two states [56]. Furthermore, to further understand the PLQY of the molecule in solution and thin film, the radiative rate constant (kr) and non-radiative rate constant (knr) were calculated from the PLQY values and PL lifetimes (τ) according to Equation 1 and Equation 2. As can be

Benzoimidazolium-derived dimeric and hydride n-dopants for organic electron-transport materials: impact of substitution on structures, electrochemistry, and reactivity

• Swagat K. Mohapatra,
• Khaled Al Kurdi,
• Samik Jhulki,
• Georgii Bogdanov,
• John Bacsa,
• Maxwell Conte,
• Tatiana V. Timofeeva,
• Seth R. Marder and
• Stephen Barlow

Beilstein J. Org. Chem. 2023, 19, 1651–1663, doi:10.3762/bjoc.19.121

• V) and VII•– to VII2– (−1.93 V); since the cleavage is rate determining, VII will be converted to VII•– and then, when excess dimer is used, to VII2– with a comparable rate constant. Indeed spectra obtained at long-reaction times (see Supporting Information File 1, Figure S7) are similar to those

Radical chemistry in polymer science: an overview and recent advances

• Zixiao Wang,
• Feichen Cui,
• Yang Sui and
• Jiajun Yan

Beilstein J. Org. Chem. 2023, 19, 1580–1603, doi:10.3762/bjoc.19.116

• can decompose to produce a stoichiometric pair of the primary initiating radical and a nitroxide radical, thus combining the roles of a conventional initiator and a control agent. The mechanism is shown in Scheme 4 [35]. Due to the steric effect of TEMPO, the dissociation rate constant, kd, of the

Photoredox catalysis harvesting multiple photon or electrochemical energies

• Mattia Lepori,
• Simon Schmid and
• Joshua P. Barham

Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81

• a two-photon process. DBU was found to quench the steady-state fluorescence of *PC1 with a quenching rate constant two orders of magnitude smaller than the diffusion rate constant in DMSO at 298 K and one order of magnitude greater under the borylation reaction conditions (i.e., 0.20 M DBU) than the

CuAAC-inspired synthesis of 1,2,3-triazole-bridged porphyrin conjugates: an overview

• Dileep Kumar Singh

Beilstein J. Org. Chem. 2023, 19, 349–379, doi:10.3762/bjoc.19.29

• . The ultrafast pump-probe technique was used to determine the photoinduced charge separation in zinc porphyrin 96 and the rate constant was found on the order of 1010 s−1, clearly showing ultrafast electron-transfer between graphene and porphyrin units. Hence, these hybrids could be useful for light

Experimental and theoretical studies on the synthesis of 1,4,5-trisubstituted pyrrolidine-2,3-diones

• Nguyen Tran Nguyen,
• Vo Viet Dai,
• Nguyen Ngoc Tri,
• Luc Van Meervelt,
• Nguyen Tien Trung and
• Wim Dehaen

Beilstein J. Org. Chem. 2022, 18, 1140–1153, doi:10.3762/bjoc.18.118

• /bjoc.18.118 Abstract Substituted 4-acetyl-3-hydroxy-3-pyrroline-2-ones have been prepared via three-component reactions and the tautomerism of these 3-pyrroline-2-ones is due to the slight difference of energy, and the significantly large rate constant of transformation between two tautomers. 1,4,5

• ···O intramolecular hydrogen bond (distance ca. 1.7–1.8 Å) (cf. Figures 4–6). The isomerization of 4a/4a’ is extremely fast due to the high rate constant of about 1012 s−1 at 298 K, calculated by the transitional state theory method and quantum tunneling effect [47]. It is thus impossible to

• IS8 can be omitted because it is so fast with a small activation energy of 2.1 kcal·mol−1), the formation of product 10ab is superior as compared to its isomer. In terms of the value of the rate constant k, the direction of 10ab formation is in the range of 103–106 times faster than 10ab-v2. The

Synthesis, optical and electrochemical properties of (D–π)₂-type and (D–π)₂Ph-type fluorescent dyes

• Kosuke Takemura,
• Kazuki Ohira,
• Taiki Higashino,
• Keiichi Imato and
• Yousuke Ooyama

Beilstein J. Org. Chem. 2022, 18, 1047–1054, doi:10.3762/bjoc.18.106

• -resolved fluorescence spectroscopy of the two dyes revealed that the fluorescence lifetimes (τfl) are 0.62 ns for OTK-2 and 0.66 ns for OTT-2, indicating that there is a little difference in the τfl values of the two dyes. The radiative rate constant (kr = 6.2 × 108 s−1) for OTT-2 is slightly larger than

• that (5.8 × 108 s−1) for OTK-2. However, the nonradiative rate constant (knr = 8.9 × 108 s−1) of OTT-2 is smaller than that (1.0 × 109 s−1) for OTK-2. As the result, the ratio of nonradiative constant to radiative constant (knr/kr = 1.4) for OTT-2 is smaller than that (1.7) for OTK-2, suggesting that

Site-selective reactions mediated by molecular containers

• Rui Wang and
• Yang Yu

Beilstein J. Org. Chem. 2022, 18, 309–324, doi:10.3762/bjoc.18.35

• ester group in turn to the aqueous solution. Addition of base would result in the hydrolysis of one ester group to the corresponding carboxylic acid. Product distributions indicated a two- to four-fold relative decrease in the hydrolysis rate constant of the second ester caused by the confined space in

A photochemical C=C cleavage process: toward access to backbone N-formyl peptides

• Haopei Wang and
• Zachary T. Ball

Beilstein J. Org. Chem. 2021, 17, 2932–2938, doi:10.3762/bjoc.17.202

• 1 in acetone. Preparation and hydrolysis kinetics (inset) of N-formyl product 11. Dashed line: first-order decay fit used in calculating the rate constant. Proposed mechanism for the formation of aldehyde 3 and N-formyl product 8. Supporting Information Supporting Information File 280: Experimental

Kinetics of enzyme-catalysed desymmetrisation of prochiral substrates: product enantiomeric excess is not always constant

• Peter J. Halling

Beilstein J. Org. Chem. 2021, 17, 873–884, doi:10.3762/bjoc.17.73

• elementary rate constants by the same factor will not change the shape of the progress of product formation and enantiomeric excess, just the timescale over which this occurs. Hence one elementary rate constant may be set to an arbitrary value, with others effectively expressed as a multiplier times this

Insight into functionalized-macrocycles-guided supramolecular photocatalysis

• Minzan Zuo,
• Krishnasamy Velmurugan,
• Kaiya Wang,
• Xueqi Tian and
• Xiao-Yu Hu

Beilstein J. Org. Chem. 2021, 17, 139–155, doi:10.3762/bjoc.17.15

• due to the reduced electrostatic repulsion between the carboxylate groups of AC and the cationic ammonium groups of WP6. Although the selectivity is enhanced, the reaction rate constant of AC with WP6 is 4 times slower compared to that without any host molecule, which may be due to the mismatching

Synthesis of purines and adenines containing the hexafluoroisopropyl group

• Viacheslav Petrov,
• Rebecca J. Dooley,
• Alexander A. Marchione,
• Elizabeth L. Diaz,
• Brittany S. Clem and
• William Marshall

Beilstein J. Org. Chem. 2020, 16, 2739–2748, doi:10.3762/bjoc.16.224

• nonselective inversion recovery experiments. The rate constant for the interconversion between the rotamers at each temperature was determined using numerical integration, minimizing the square of residuals, with the obtained T1 relaxation time as an input to the model. The linewidths at elevated temperature

Dawn of a new era in industrial photochemistry: the scale-up of micro- and mesostructured photoreactors

• Emine Kayahan,
• Mathias Jacobs,
• Leen Braeken,
• Leen C.J. Thomassen,
• Simon Kuhn,
• Tom van Gerven and
• M. Enis Leblebici

Beilstein J. Org. Chem. 2020, 16, 2484–2504, doi:10.3762/bjoc.16.202

• platform for enhancing the photoreaction rates and easier scale-up. One of the hurdles in scaling up of photoreactors is the lack of a consensus on a benchmark to compare different scales and geometries. The simplest benchmark is the apparent rate constant kapp [12][13][14][15] shown in Equation 1. where

• transport. When DaII is larger than 1, the reaction is mass-transport-limited. The residence time needs to be larger than the characteristic reaction time to achieve a complete conversion [11]. where tr is the characteristic reaction time, which can be loosely defined as the inverse of the reaction rate

• constant. Many photoreactions are heterogeneous, which means that the reaction requires the presence of at least two phases. Heterogeneous reactions require either a solid photocatalyst in a liquid medium or gas and liquid phases as the reactants. The mass transport and mixing gain extra importance in such

[3 + 2] Cycloaddition with photogenerated azomethine ylides in β-cyclodextrin

• Margareta Sohora,
• Leo Mandić and
• Nikola Basarić

Beilstein J. Org. Chem. 2020, 16, 1296–1304, doi:10.3762/bjoc.16.110

• most probably undergoes decarboxylation delivering 1AMY from the S1 state [49]. In CH3CN, 1AMY decays with a rate constant of 2.9 × 106 M−1 s−1, and reacts with methyl acrylate in [3 + 2] cycloaddition with the rate constant 2.7 × 107 M−1 s−1 [49]. Protic solvents such as CH3OH or H2O quench

• and intercepted with AN to yield cycloadducts 7 or 11, respectively. However, the formation of cycloadducts is very inefficient, which may be ascribed to a smaller rate constant for the quenching due to steric hindrance imposed by the bulky cyclohexane or adamantine moiety. Thus, irradiation of 2 gave

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

• possesses an internal activation barrier resulting in a system having a certain energy threshold. Equation 8 shows how temperature affects the rate constant for electron transfer ket The free activation enthalpy [67][72] controls the internal activation barrier, Equation 8 [65]. The free enthalpy of

p-Pyridinyl oxime carbamates: synthesis, DNA binding, DNA photocleaving activity and theoretical photodegradation studies

• Panagiotis S. Gritzapis,
• Panayiotis C. Varras,
• Nikolaos-Panagiotis Andreou,
• Katerina R. Katsani,
• Konstantinos Dafnopoulos,
• George Psomas,
• Zisis V. Peitsinis,
• Alexandros E. Koumbis and
• Konstantina C. Fylaktakidou

Beilstein J. Org. Chem. 2020, 16, 337–350, doi:10.3762/bjoc.16.33

• corresponding activation energy (Equation 1) and free activation energy (Equation 2) were calculated for compound 12 and found 3.14 and 2.95 kcal/mol, respectively. These values were used in Equation 3 in order to calculate the rate constant for the N−O bond dissociation. Accordingly, kr, was found to be 4.27

• chemical reaction below (Scheme 3). The activation free energy for the decarboxylation reaction is only 1.09 kcal/mol and by using Equation 4 (see theoretical calculations section) we find a rate constant kr = 9.87∙1011 s−1, characterizing the reaction as an ultrafast one, with a corresponding life-time of

• energy and free energy of activation are given in Equation 1 and Equation 2, respectively: For the calculation of the rate constant, kr, the Eyring’s classical Equation 3 was used, where in the above equation kB is the Boltzmann’s constant (1.380662∙10−23 J/K), h is the Planck’s constant (6.626176∙10−34

Photoreversible stretching of a BAPTA chelator marshalling Ca²⁺-binding in aqueous media

• Aurélien Ducrot,
• Arnaud Tron,
• Robin Bofinger,
• Ingrid Sanz Beguer,
• Jean-Luc Pozzo and
• Nathan D. McClenaghan

Beilstein J. Org. Chem. 2019, 15, 2801–2811, doi:10.3762/bjoc.15.273

• restoration of the electronic absorption band attributed to the π–π* transition at 30 °C (Figure 5), the rate constant (k) was estimated at 5.4 × 10−5 s−1. Photoisomerization was also recorded in electron-absorption spectroscopy in the presence of calcium (see Figure S2 in Supporting Information File 1). The

A combinatorial approach to improving the performance of azoarene photoswitches

• Joaquin Calbo,
• Aditya R. Thawani,
• Rosina S. L. Gibson,
• Andrew J. P. White and
• Matthew J. Fuchter

Beilstein J. Org. Chem. 2019, 15, 2753–2764, doi:10.3762/bjoc.15.266

• inversely proportional to the rate constant, and this is exponentially dependent on the free-energy barrier according to Eyring theory. Thus, a small variation in the energy barrier of <1 kcal/mol leads to a change of few orders of magnitude in half-life. Vertical electronic transition energies for the

Reversible switching of arylazopyrazole within a metal–organic cage

• Anton I. Hanopolskyi,
• Soumen De,
• Michał J. Białek,
• Yael Diskin-Posner,
• Liat Avram,
• Moran Feller and
• Rafal Klajn

Beilstein J. Org. Chem. 2019, 15, 2398–2407, doi:10.3762/bjoc.15.232

• linear profile of the recovery suggests that the reaction obeys first-order kinetics, with a rate constant of 0.0975 h−1, corresponding to a thermal half-life of Z-1, τ1/2 ≈ 7.1 hours. This value of τ1/2 is surprisingly small vis-à-vis the previously reported [35] τ1/2 ≈ 10 days in acetonitrile. To

• extent than does aqueous 2. These results suggest that cage 2 can catalyze the thermal back-isomerization of Z-1 to E-1, whose kinetics can be written down as: where the pseudo-first-order rate constant kobs is the product of k and the concentration of the cage, c2, which remains constant over time. To

• increasing concentrations of 2 (A∞ denotes the absorbance at λmax before irradiation; A0 – immediately after exposure to UV light; At – after thermal relaxation for time t). b) Cage concentration dependence of the pseudo-first-order rate constant kobs. c) The proposed mechanism underlying the Pd2