2-Hetaryl-1,3-tropolones based on five-membered nitrogen heterocycles: synthesis, structure and properties

• Yury A. Sayapin,
• Inna O. Tupaeva,
• Alexandra A. Kolodina,
• Eugeny A. Gusakov,
• Vitaly N. Komissarov,
• Igor V. Dorogan,
• Nadezhda I. Makarova,
• Anatoly V. Metelitsa,
• Valery V. Tkachev,
• Sergey M. Aldoshin and
• Vladimir I. Minkin

Beilstein J. Org. Chem. 2015, 11, 2179–2188, doi:10.3762/bjoc.11.236

• activation energy barrier of the limiting step of the formation of 1,3-tropolone derivatives in the reaction of methylene-active five-membered heterocycles with o-chloranil in acetic acid solution strongly depends on the properties of the fragment X in the heterocyclic compounds. The larger the

Computational study of productive and non-productive cycles in fluoroalkene metathesis

• Markéta Rybáčková,
• Jan Hošek,
• Ondřej Šimůnek,
• Viola Kolaříková and
• Jaroslav Kvíčala

Beilstein J. Org. Chem. 2015, 11, 2150–2157, doi:10.3762/bjoc.11.232

• -difluoromethyleneruthenium complex 2AC, leading to symmetrical metallacyclobutane 2NA with activation energy around 65 kJ/mol and through the same transition state back to complex 2AC and 1,1-difluoroethene (2). However, for the productive anti-coordination of 1,1-difluoroethene (2), no stable metallacyclobutane structure

Mechanism, kinetics and selectivity of selenocyclization of 5-alkenylhydantoins: an experimental and computational study

• Biljana M. Šmit,
• Radoslav Z. Pavlović,
• Dejan A. Milenković and
• Zoran S. Marković

Beilstein J. Org. Chem. 2015, 11, 1865–1875, doi:10.3762/bjoc.11.200

• energies were calculated at T = 298 K. Rate constants were calculated using Transition state theory as implemented in TheRate program [48] and 1 M standard state as: where kB, h and R stand for the Boltzman, Planck, and the gas constant, and ΔG≠ is the free activation energy, which is calculated as the G

Synthesis of racemic and chiral BEDT-TTF derivatives possessing hydroxy groups and their achiral and chiral charge transfer complexes

• Sara J. Krivickas,
• Chiho Hashimoto,
• Junya Yoshida,
• Akira Ueda,
• Kazuyuki Takahashi,
• John D. Wallis and
• Hatsumi Mori

Beilstein J. Org. Chem. 2015, 11, 1561–1569, doi:10.3762/bjoc.11.172

• and 0.6 ohm cm for θ21-[(S,S)-2]3[(R,R)-2]3(ClO4)2 and α'-[(R,R)-2]2ClO4(H2O), respectively. Both salts show semiconducting behaviour and the activation energy of θ21-[(S,S)-2]3[(R,R)-2]3(ClO4)2 is Ea = 86 meV which is lower than that of α'-[(R,R)-2]2ClO4(H2O) which has Ea = 140 meV. Conclusion In

Synthesis of a tricyclic lactam via Beckmann rearrangement and ring-rearrangement metathesis as key steps

• Sambasivarao Kotha,
• Ongolu Ravikumar and
• Jadab Majhi

Beilstein J. Org. Chem. 2015, 11, 1503–1508, doi:10.3762/bjoc.11.163

• -caprolactam from cyclohexanone oxime involving the BR. The activation energy for the BR is almost the same as that of the nucleophilic substitution at sp2 nitrogen. To synthesize various aza-arenes and cyclic imines, such as quinolines, aza-spiro compounds and dihydropyrroles, the intramolecular SN2-type

Surprisingly facile CO₂ insertion into cobalt alkoxide bonds: A theoretical investigation

• Willem K. Offermans,
• Claudia Bizzarri,
• Walter Leitner and
• Thomas E. Müller

Beilstein J. Org. Chem. 2015, 11, 1340–1351, doi:10.3762/bjoc.11.144

• , a linear Brønsted–Evans–Polanyi relationship was found between the activation energy and the reaction energy. Keywords: activation; alkoxide; carbon dioxide; cobalt; insertion; salen; Introduction Carbon dioxide (CO2) has been known to be an attractive carbon source for decades [1][2][3][4][5][6

• , the insertion step into an Al(III)-alkoxide bond is a simple intramolecular process with a small activation energy (∆E# = 9.12 kcal/mol) [30][51]. Nevertheless, a bimetallic aluminium complex is considered in the mechanism. Since it is a bimolecular reaction, the Gibbs energies will be higher. Carbon

• that the activation energy decreases with increasing exothermicity of the CO2 insertion. Thereby, a linear relationship between the activation energy and the reaction energy – a so-called Brønsted–Evans–Polanyi relationship – was found. This relationship enables one to predict the activation barrier

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

• . Thermodynamic parameters To better understand the degradation process, the pseudo first-order kinetic equation was used to determine the kinetic parameters. The Arrhenius law was used to calculate the activation energy (Ea). The determination of the entropy and the enthalpy of activations (ΔS* and ΔH*) were

• performed using the Eyring equation [37]. The results are summarized in Table 3. The activation energy (Ea) has been found to be low (16.669 kJ mol−1) confirming that the complex 9 was very efficient for the degradation of azo dyes using H2O2. Reuse of the catalysts In this section, the reusability of the

Mechanical stability of bivalent transition metal complexes analyzed by single-molecule force spectroscopy

• Manuel Gensler,
• Christian Eidamshaus,
• Maurice Taszarek,
• Hans-Ulrich Reissig and
• Jürgen P. Rabe

Beilstein J. Org. Chem. 2015, 11, 817–827, doi:10.3762/bjoc.11.91

• to a hypothetical potential energy diagram (PED) along the rupture coordinate z (Figure 3). Starting from a bound state 0, a certain activation energy EA is needed to escape over transition state I. Under an applied force, f, the whole PED is tilted by ∆E = −f ∆z, where ∆z is the distance from state

• deforms the potential energy along the rupture coordinate z according to ∆E, thereby reducing activation energy EA and increasing force-driven rupture koff(f). Most probable rupture forces plotted over their corresponding loading rate. Each point denotes for one series of measurements at a certain pulling

On the strong difference in reactivity of acyclic and cyclic diazodiketones with thioketones: experimental results and quantum-chemical interpretation

• Andrey S. Mereshchenko,
• Alexey V. Ivanov,
• Viktor I. Baranovskii,
• Grzegorz Mloston,
• Ludmila L. Rodina and
• Valerij A. Nikolaev

Beilstein J. Org. Chem. 2015, 11, 504–513, doi:10.3762/bjoc.11.57

• intermediate thiocarbonyl ylides of type 7 from 1a–d and 2a is thermodynamically favorable. The activation energy of the 1,3-dipolar cycloaddition of diazo compounds 1 to thiobenzophenone (2a, ΔG1#) is significantly larger than the decomposition energy of 1,3,4-thiadiazolines 6 (ΔG2#). In line with these data

• equation: ΔG1–7’ = ΔG1 + ΔG2. The lower relative energy of the 1,3,4-thiadiazoline 6' decomposition products, as well as the smaller activation energy of the second step of the process (ΔG2# < ΔG1#), result in the formation of thiocarbonyl ylide 7'. Since the activation energy of the cycloaddition step is

• with 2b also proceed via a concerted pathway. The calculated activation energy of DDC 1a–f cycloadditions with thioketone 2b correlate well with the experimental results, where the lowest values of ΔG1# (30.7–31.2 kcal·mol−1; Table 2) are related to the most reactive of acyclic diazoadicarbonyl

IR and electrochemical synthesis and characterization of thin films of PEDOT grown on platinum single crystal electrodes in [EMMIM]Tf₂N ionic liquid

• Andrea P. Sandoval,
• Marco F. Suárez-Herrera and
• Juan M. Feliu

Beilstein J. Org. Chem. 2015, 11, 348–357, doi:10.3762/bjoc.11.40

• possible to establish a relation between the current and the temperature using the “initial rate” approximation and the Arrhenius Equation. Since the logarithm of the current density vs the inverse of the temperature plot showed a linear dependence, Figure 4b, the apparent activation energy were calculated

• (Table 1). The values of the activation energy for the oxidation and reduction processes are very similar and very close to the one reported for polythiophene (16 kJ mol−1) [24], which means that the oxidation and reduction of PEDOT (and the corresponding counterion exchange) occurs easily in spite of

• the fact that the viscosity of the ionic liquid is quite high [16]. It is important to state that the activation energy of the nucleation kinetics related to the ion exchange depends on the overpotential used. Even so, the results shown in Table 1, Figure 3a and Figure 4 show that the kinetics of the

Molecular ordering at electrified interfaces: Template and potential effects

• Thanh Hai Phan and
• Klaus Wandelt

Beilstein J. Org. Chem. 2014, 10, 2243–2254, doi:10.3762/bjoc.10.233

• , provided a sufficient surface mobility allows the adsorbed molecules to reach their equilibrium positions, i.e., minima in the corrugation function. In this case the substrate surface acts as a “template”. Under UHV conditions the activation energy for structural equilibration is usually provided by

• the 120° step edge serves as a positional marker. The phase-transition process starts preferentially at point defects and domain boundaries (as marked by the white arrows in Figure 6b) because this requires a relatively low activation energy. Finally, the new stripe pattern is completed right after

Proton transfers in the Strecker reaction revealed by DFT calculations

• Shinichi Yamabe,
• Guixiang Zeng,
• Wei Guan and
• Shigeyoshi Sakaki

Beilstein J. Org. Chem. 2014, 10, 1765–1774, doi:10.3762/bjoc.10.184

• alanine was studied by DFT calculations for the first time, which involves two reaction stages. In the first reaction stage, the aminonitrile was formed. The rate-determining step is the deprotonation of the NH3+ group in MeCH(OH)-NH3+ to form 1-aminoethanol, which occurs with an activation energy barrier

• + and CN−]. This step is exothermic by 5.5 kcal/mol with a small activation energy barrier (ΔE≠) of 1.4 kcal/mol. Starting from 4, a proton of the NH3+ group migrates to one water molecule to form 5 [Me(H)C(OH)-NH2(H3O+) and CN−] via a transition state TS4/5. After that, the proton migrates from H3O+ to

• addition model of TS1/2 was examined by the use of the amine in Scheme 2. The activation energy of the less crowded TS1/2–A is 1.8 kcal/mol smaller than the more crowded TS1/2–B; see Figure 3. This calculation result is consistent with Harada's work that a chiral product [4] was obtained in the Strecker

Theoretical studies on the intramolecular cyclization of 2,4,6-t-Bu₃C₆H₂P=C: and effects of conjugation between the P=C and aromatic moieties

• Masaaki Yoshifuji and
• Shigekazu Ito

Beilstein J. Org. Chem. 2014, 10, 1032–1036, doi:10.3762/bjoc.10.103

• alternative Fritsch–Buttenberg–Wiechell-type rearrangement requires almost no activation energy, the intramolecular cyclization needs an activation energy of 12.3 kcal/mol at the MP2(full)/6-31G(d) condition. DFT calculations supported that the optimized structure of the cyclization product of Mes*P=C

• activation energy (ΔEa) was 12.3 kcal/mol, and the Gibbs free energy ΔG was estimated as 11.6 kcal/mol. Such energy profile indicates a sharp contrast to the modeled FBW rearrangement of phosphanylidenecarbene requiring no activation energy [20], and would be partially explicable for the experimental result

• conclusion, the chemistry of the intramolecular C–H insertion of phosphanylidenecarbene 1 affording 2 was studied by ab initio and DFT calculations. The intramolecular cyclization requires an activation energy, whereas the phosphorus version of the FBW rearrangement proceeded without an energetic barrier

On the mechanism of photocatalytic reactions with eosin Y

• Michal Majek,
• Fabiana Filace and
• Axel Jacobi von Wangelin

Beilstein J. Org. Chem. 2014, 10, 981–989, doi:10.3762/bjoc.10.97

• -colored LEDs (see Supporting Information File 1 for spectrum). The activation energy of thermal heterolysis of arenediazonium ions is approx. 115 kJ/mol (1.19 eV) [29]. The energy of a photon at the edge of the visible spectrum (400 nm) is 3.1 eV so that such photons carry sufficient energy to heterolyze

Site-selective covalent functionalization at interior carbon atoms and on the rim of circumtrindene, a C₃₆H₁₂ open geodesic polyarene

• Hee Yeon Cho,
• Ronald B. M. Ansems and
• Lawrence T. Scott

Beilstein J. Org. Chem. 2014, 10, 956–968, doi:10.3762/bjoc.10.94

• in a cold trap [10][11][12]. The high temperatures used in FVP (often up to 1100 °C) provide sufficient thermal energy to enable molecules to overcome high activation energy barriers. The FVP approach takes advantage of the fact that the normal out-of-plane deformations of simple planar polyarenes

Dimerisation, rhodium complex formation and rearrangements of N-heterocyclic carbenes of indazoles

• Zong Guan,
• Jan C. Namyslo,
• Martin H. H. Drafz,
• Martin Nieger and
• Andreas Schmidt

Beilstein J. Org. Chem. 2014, 10, 832–840, doi:10.3762/bjoc.10.79

• frequencies on Z→E isomerisation. The following scheme presents diagnostic peak assignments of the 1H and 13C NMR spectra, taken at 400 and 100 MHz in CDCl3, respectively. According to DFT calculations the conversion of 13a to 14a requires an activation energy of ΔG# = +79 kJ/mol (ΔE = +89 kJ/mol) while the

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

• pure form by crystallization. While Rice and Brossi focused on the optical and crystallographic properties of these compounds, Szántay et al. gave a first estimate of the activation energy of the interconversion of these two rotamers based on dynamic NMR spectroscopy at variable temperature. They

• ‡ (293 K) = 93.2 ± 0.1 kJ/mol (E to Z) respectively (Figure 1, Figure 2). Dynamic HPLC studies Like the DNMR data, the simple kinetic analysis only permits the determination of the free activation energy while the separation of entropic and enthalpic contributions requires a variation of the temperature

• implemented the unified equation. For the evaluation of activation parameters of the interconversion process experiments between 30 °C and 55 °C were considered, because at lower temperatures the plateau height was too low to be determined with high precision. The Gibbs free activation energy ΔG‡ (T) was

Substrate dependent reaction channels of the Wolff–Kishner reduction reaction: A theoretical study

• Shinichi Yamabe,
• Guixiang Zeng,
• Wei Guan and
• Shigeyoshi Sakaki

Beilstein J. Org. Chem. 2014, 10, 259–270, doi:10.3762/bjoc.10.21

• , the ethylbenzene product was obtained and this is shown in XVIIIPh of Figure 6. Figure 7 shows energy changes of the acetophenone reaction. The rate-determining step was found to be TS5 with the activation energy, +18.04 kcal/mol. The protonation of the anion Ph–C(−)Me–N–N–H in XPh is difficult

• , because the anion character is delocalized in the phenyl ring by canonical resonance structures. The activation energy relative to the hydrazone is +26.34 (= + 18.04 − (−8.30)) kcal/mol, which is somewhat larger yet comparable to the experimental one, +22.9 kcal/mol in the solvent butyl carbitol, n-C4H9

• obtained, it was found to be unlikely because of the very large activation energy at the N2 extrusion step TS5, (xi). Second, elementary steps of OH− containing two reactions were traced, where ketones are acetone and acetophenone. These results are summarized in Scheme 7. From the ketone to the hydrazone

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

• the real mechanism of the protodeauration step. Interestingly the reaction profile with the lowest activation energy was distinguished in the TfO− promoted tautomerization of 11 to form 12 followed by direct proton transfer to afford the product 13 and regeneration of the catalyst. Intermediates of

Regioselective carbon–carbon bond formation of 5,5,5-trifluoro-1-phenylpent-3-en-1-yne

• Motoki Naka,
• Tomoko Kawasaki-Takasuka and
• Takashi Yamazaki

Beilstein J. Org. Chem. 2013, 9, 2182–2188, doi:10.3762/bjoc.9.256

• elucidated as follows: deuteration would quickly occur to afford 4-d1 and 4-d2 whose proportion would reflect the ratio of 4-Li1 and 4-Li2. On the other hand, less reactive aldehydes should be captured more slowly and the product preference of 5 to 6 would be kinetically determined by their activation energy

Cyclization of substitued 2-(2-fluorophenylazo)azines to azino[1,2-c]benzo[d][1,2,4]triazinium derivatives

• Aleksandra Jankowiak,
• Emilia Obijalska and
• Piotr Kaszynski

Beilstein J. Org. Chem. 2013, 9, 1873–1880, doi:10.3762/bjoc.9.219

• reaction (NAS) electron-donating groups in the C(4) position of the pyridine ring in 4 should increase the reaction rate. Computational results demonstrate the contrary and as the electron donation of the substituent R increases in the order H (4a) < CH3 (4b) < OCH3 (4g) so does the activation energy

• cyclization process involves 6 π electrons, which allows the formation of the non-zwitterionic product such as 10. Comparison of cyclization of 4c-Z and 13-Z further demonstrates that the activation energy is lower for the azene than for the analogues stilbene, which presumably is related to the

• Table 1. For further probing of the cyclization mechanism, the mildly activating [13][14] N=N-bridging group in 4c–Z was replaced by the non-activating CH=CH group in 13-Z (Figure 6). A computational analysis demonstrated that this structural modification resulted in a modest increase of activation

Gallium-containing polymer brush film as efficient supported Lewis acid catalyst in a glass microreactor

• Rajesh Munirathinam,
• Roberto Ricciardi,
• Richard J. M. Egberink,
• Jurriaan Huskens,
• Michael Holtkamp,
• Herbert Wormeester,
• Uwe Karst and
• Willem Verboom

Beilstein J. Org. Chem. 2013, 9, 1698–1704, doi:10.3762/bjoc.9.194

• concentrations of 1 (10–25 µM, Figure 1). The experimental data were fitted to a first-order rate equation, giving an observed rate constant, kobs, of (11 ± 2) × 10−3 s−1. The values of the rate constants at different oxime concentrations were the same, within experimental error. The activation energy of the

• dehydration of oxime 1 was determined by calculating the kobs values at different temperatures ranging from 70–90 °C (Supporting Information, Figure 1), with increments of five degrees. From the slope of the Arrhenius plot (Figure 2), the resulting activation energy was calculated to be 6.55 kJ·mol−1. The

Computational study of the rate constants and free energies of intramolecular radical addition to substituted anilines

• Andreas Gansäuer,
• Meriam Seddiqzai,
• Tobias Dahmen,
• Rebecca Sure and
• Stefan Grimme

Beilstein J. Org. Chem. 2013, 9, 1620–1629, doi:10.3762/bjoc.9.185

• clear that the semi-local TPSS and BP86 functionals strongly underestimate the activation energy of the 5-exo cyclization (by about 3 kcal mol−1) due to the SIE but this behavior is as expected for functionals of this type. The hybrid functional B3LYP slightly overestimates the activation barrier when

Tandem dinucleophilic cyclization of cyclohexane-1,3-diones with pyridinium salts

• Mostafa Kiamehr,
• Firouz Matloubi Moghaddam,
• Satenik Mkrtchyan,
• Volodymyr Semeniuchenko,
• Linda Supe,
• Alexander Villinger,
• Peter Langer and
• Viktor O. Iaroshenko

Beilstein J. Org. Chem. 2013, 9, 1119–1126, doi:10.3762/bjoc.9.124

• . Hence, the attack by oxygen on the last stage must be excluded. Within the scope of this mechanism the activation energy is 21.3 kcal/mol (energy gap between 22a and 19). Other TSs (K-S1a-2, K-S1a-3, see Supporting Information File 2), inherent for the initial stage of new C–C bond formation turned out

Interplay of ortho- with spiro-cyclisation during iminyl radical closures onto arenes and heteroarenes

• Roy T. McBurney and
• John C. Walton

Beilstein J. Org. Chem. 2013, 9, 1083–1092, doi:10.3762/bjoc.9.120

• -addition may result from the electron-releasing character of the t-Bu substituent. The SOMO in 9a has a node at C(3) so electron–electron repulsion is smaller than in the SOMOs for para- or ortho-attack. This will lower the activation energy for meta-addition relative to para- or ortho-addition. For all

• spectra [46]. We estimated that the concentration ratio [12a]/[11a] > 4 at 230 K, and hence ksc(230 K) > 55 s−1 (see Supporting Information File 1 for details). Most radical cyclisations have Arrhenius log(Ac) ≈ 10.5 s−1 [47][48] and, by assuming that this holds for 12a, an activation energy Esc < 9 kcal

• the EPR spectra and with the lack of cyclised products. For the parent biphenyliminyl radical 5a the ortho-ring closure (Table 4, entry 5) was computed to have a lower activation energy than spiro-cyclisation (Table 4, entry 4) and to be exothermic in comparison with the endothermic spiro-mode. This