Combined experimental and theoretical studies of regio- and stereoselectivity in reactions of β-isoxazolyl- and β-imidazolyl enamines with nitrile oxides

• Ilya V. Efimov,
• Marsel Z. Shafikov,
• Nikolai A. Beliaev,
• Natalia N. Volkova,
• Tetyana V. Beryozkina,
• Wim Dehaen,
• Zhijin Fan,
• Viktoria V. Grishko,
• Gert Lubec,
• Pavel A. Slepukhin and
• Vasiliy A. Bakulev

Beilstein J. Org. Chem. 2016, 12, 2390–2401, doi:10.3762/bjoc.12.233

• with inverse electron demand, similarly to the reaction of enamines with azides [37]. To gain deeper insights into the mechanism of the cycloaddition between nitrile oxides and enamines, quantum chemical calculations were carried out using the Gaussian 09 [38] programs package at B3LYP/def2-TZVP [39

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

Superelectrophilic activation of 5-hydroxymethylfurfural and 2,5-diformylfuran: organic synthesis based on biomass-derived products

• Dmitry S. Ryabukhin,
• Dmitry N. Zakusilo,
• Mikhail O. Kompanets,
• Anton A.Tarakanov,
• Irina A. Boyarskaya,
• Tatiana O. Artamonova,
• Mikhail A. Khohodorkovskiy,
• Iosyp O. Opeida and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2016, 12, 2125–2135, doi:10.3762/bjoc.12.202

• (Scheme 1). All species A, B, C, and D may play a role as reactive intermediates derived from 1a and 2 in superacids. To estimate the electrophilic properties of cations A, B, C, and D we performed quantum chemical calculations by the DFT method (Table 1). HOMO and LUMO energies, global electrophilicity

Experimental and theoretical insights in the alkene–arene intramolecular π-stacking interaction

• Valeria Corne,
• Ariel M. Sarotti,
• Carmen Ramirez de Arellano,
• Rolando A. Spanevello and
• Alejandra G. Suárez

Beilstein J. Org. Chem. 2016, 12, 1616–1623, doi:10.3762/bjoc.12.158

• , Universidad de Valencia, Valencia 46100, Spain 10.3762/bjoc.12.158 Abstract Chiral acrylic esters derived from biomass were developed as models to have a better insight in the aryl–vinyl π-stacking interactions. Quantum chemical calculations, NMR studies and experimental evidences demonstrated the presence

Synthesis of 2,1-benzisoxazole-3(1H)-ones by base-mediated photochemical N–O bond-forming cyclization of 2-azidobenzoic acids

• Daria Yu. Dzhons and
• Andrei V. Budruev

Beilstein J. Org. Chem. 2016, 12, 874–881, doi:10.3762/bjoc.12.86

• to quantum-chemical calculations, the energy barrier of this rearrangement is approximately 40 kJ mol−1 [51], with the limiting step being the formation of B. Therefore, the direction of this reaction solely depends on the conversion of A and formation of C. Dyall et al. [52][53] have proposed a

Recent highlights in biosynthesis research using stable isotopes

• Jan Rinkel and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2015, 11, 2493–2508, doi:10.3762/bjoc.11.271

• subsequent 1,2-hydride migration to 63 followed by ring closure gives 64, which is deprotonated to give pentalenene (65). Quantum chemical calculations led to the suggestion of the protoilludyl cation 66 as central intermediate between 61 and 64 (pathway B), which is directly formed from 61 [72

Deproto-metallation of N-arylated pyrroles and indoles using a mixed lithium–zinc base and regioselectivity-computed CH acidity relationship

• Mohamed Yacine Ameur Messaoud,
• Ghenia Bentabed-Ababsa,
• Madani Hedidi,
• Aïcha Derdour,
• Floris Chevallier,
• Yury S. Halauko,
• Oleg A. Ivashkevich,
• Vadim E. Matulis,
• Laurent Picot,
• Valérie Thiéry,
• Thierry Roisnel,
• Vincent Dorcet and
• Florence Mongin

Beilstein J. Org. Chem. 2015, 11, 1475–1485, doi:10.3762/bjoc.11.160

• recently [42][52]. The results of quantum chemical calculations on CH acidity of the different N-arylated pyrroles 1 and indoles 2, obtained both for THF solution (Figure 5) and gas phase (see Supporting Information File 1), are presented in the current paper. A potential acidity of the methoxy groups in

Antioxidant potential of curcumin-related compounds studied by chemiluminescence kinetics, chain-breaking efficiencies, scavenging activity (ORAC) and DFT calculations

• Adriana K. Slavova-Kazakova,
• Silvia E. Angelova,
• Timur L. Veprintsev,
• Petko Denev,
• Davide Fabbri,
• Maria Antonietta Dettori,
• Maria Kratchanova,
• Vladimir V. Naumov,
• Aleksei V. Trofimov,
• Rostislav F. Vasil’ev,
• Giovanna Delogu and
• Vessela D. Kancheva

Beilstein J. Org. Chem. 2015, 11, 1398–1411, doi:10.3762/bjoc.11.151

• quantum chemical calculations (see section “Model 4: DFT calculations”) for BDE of 13 and studied compounds in water medium confirm our hypothesis. It is noteworthy that the literature data for individual phenolic compounds acquired with ORAC as a model system are rather poor in comparison with the data

• to act as chain-breaking antioxidants. The experimental results (models 1–3) obtained are qualitatively supported by quantum chemical calculations (model 4). Dimers showed higher activity than the corresponding monomers in the experiments in homogeneous solutions (models 1 and 2) and similar activity

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

• -oxathiole 3 and alkene 5 (4:1) was formed, whereas at 80 °C, product 5 was formed exclusively (81%) [20]. In order to explain the obtained results and to elucidate the reaction pathway (which governs reactions of DDC 1 with aromatic and aliphatic thioketones 2), detailed quantum-chemical calculations of the

• transient thiirane S-sulfide 8’d (step d), it is most likely that it follows the pathway proposed for the spontaneous desulfurization of matrix-isolated oxathiiranes [32]. Conclusion The quantum-chemical calculations show that the initial step of the 1,3-dipolar cycloaddition of acyclic 2-diazo-1,3

• relative energy of the reagents, reaction intermediates, transition states, and reaction products on the potential energy surfaces were carried out. The results of the performed study are summarized and discussed in the present publication. Results and Discussion The subjects of the quantum-chemical

Synthesis and characterization of a new photoinduced switchable β-cyclodextrin dimer

• Florian Hamon,
• Claire Blaszkiewicz,
• Marie Buchotte,
• Estelle Banaszak-Léonard,
• Hervé Bricout,
• Sébastien Tilloy,
• Eric Monflier,
• Christine Cézard,
• Laurent Bouteiller,
• Christophe Len and
• Florence Djedaini-Pilard

Beilstein J. Org. Chem. 2014, 10, 2874–2885, doi:10.3762/bjoc.10.304

• of 1 atm and a temperature of 300 K. In order to obtain representative ensembles of conformations for the two bis-CD systems, molecular configurations from MD trajectories were clustered. Ab initio calculations were performed with the Gaussian 09 program [50] to perform quantum chemical calculations

Isoxazolium N-ylides and 1-oxa-5-azahexa-1,3,5-trienes on the way from isoxazoles to 2H-1,3-oxazines

• Alexander F. Khlebnikov,
• Mikhail S. Novikov,
• Yelizaveta G. Gorbunova,
• Ekaterina E. Galenko,
• Kirill I. Mikhailov,
• Viktoriia V. Pakalnis and
• Margarita S. Avdontceva

Beilstein J. Org. Chem. 2014, 10, 1896–1905, doi:10.3762/bjoc.10.197

• really formed in this reaction?” and “What is their reactivity?” To this end, we carried out quantum-chemical calculations of the formation and the ring opening of isoxazolium N-ylides. Probing the type of the mechanistic scheme of the 2H-1,3-oxazine formation was also conducted by searching for the

Substitution effect and effect of axle’s flexibility at (pseudo-)rotaxanes

• Friedrich Malberg,
• Jan Gerit Brandenburg,
• Werner Reckien,
• Oldamur Hollóczki,
• Stefan Grimme and
• Barbara Kirchner

Beilstein J. Org. Chem. 2014, 10, 1299–1307, doi:10.3762/bjoc.10.131

• substitution with different functional groups and of molecular flexibility by changing within the axle from a single C–C bond to a double C=C bond. Therefore, we present static quantum chemical calculations at the dispersion-corrected density functional level (DFT-D3) for several Leigh-type rotaxanes. The

• from a more bowed axle with respect to the wheel. Conclusion We investigated several rotaxanes by static quantum chemical calculations in order to gain insight into the interplay of different non-covalent interactions. Therefore, we studied the substitution of the rotaxanes with different functional

cis–trans Isomerization of silybins A and B

• Michaela Novotná,
• Radek Gažák,
• David Biedermann,
• Florent Di Meo,
• Petr Marhol,
• Marek Kuzma,
• Lucie Bednárová,
• Kateřina Fuksová,
• Patrick Trouillas and
• Vladimír Křen

Beilstein J. Org. Chem. 2014, 10, 1047–1063, doi:10.3762/bjoc.10.105

• isomerization can be initiated by the formation of coordination complexes at either C-4=O or O-1 (see Scheme 5). Nevertheless, based on the quantum chemical calculations (Table 3 and Table 4) together with the representation of cis-isomers in the isomerization mixture, the most stable coordination complex IIa

• of taxifolin isomerization [34]. A deuterium incorporation NMR study supported by quantum chemical calculations showed that the intermediate of taxifolin with an open benzopyranone ring (α-hydroxychalcone related to IIc in our study) is very short-lived and the energy barrier for its formation is

Use of activated enol ethers in the synthesis of pyrazoles: reactions with hydrazine and a study of pyrazole tautomerism

• Denisa Tarabová,
• Stanislava Šoralová,
• Martin Breza,
• Marek Fronc,
• Wolfgang Holzer and
• Viktor Milata

Beilstein J. Org. Chem. 2014, 10, 752–760, doi:10.3762/bjoc.10.70

• ). Quantum-chemical calculations To support the experimental results were also performed DFT (Density Functional Theory method) calculations by using the B3LYP hybrid functional [31][32][33] and 6-311++G** basis sets of the Gaussian basis set library [34]. The SCRF theory via the IEFPCM (Integral Equation

• unsymmetrical structures of the ethylene substituent. This structure has been established by X-ray analysis. The tautomeric behavior of these materials has been modelled by using DFT quantum-chemical calculations. The most stable structural forms are 5aA1, 5aA2, 5bE1, 5bE2, 5cE1, 5cE2, 5dA1 and 5dA2. As

One-pot three-component synthesis and photophysical characteristics of novel triene merocyanines

• Christian Muschelknautz,
• Robin Visse,
• Jan Nordmann and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2014, 10, 599–612, doi:10.3762/bjoc.10.51

• quantum chemical calculations on the DFT level (B3LYP functional, 6-31G* basis set) [40]. The computed Kohn–Sham frontier molecular orbitals of compound 8a clearly indicate a charge transfer from the aminovinyl dominated donor fragment in the HOMO to the indolone-centered LUMO, which is generally

Decandrinin, an unprecedented C₉-spiro-fused 7,8-seco-ent-abietane from the Godavari mangrove Ceriops decandra

• Hui Wang,
• Min-Yi Li,
• Félix Zongwe Katele,
• Tirumani Satyanandamurty,
• Jun Wu and
• Gerhard Bringmann

Beilstein J. Org. Chem. 2014, 10, 276–281, doi:10.3762/bjoc.10.23

• combination with quantum-chemical calculations. Decandrinin is the first 7,8-seco-ent-abietane. Keywords: abietane; absolute configuration; Ceriops decandra; circular dichroism; decandrinin; Rhizophoraceae; Introduction Ceriops decandra is a mangrove of the family Rhizophoraceae. It is widely distributed

• NMR investigations, and by circular dichroism (CD) and optical-rotatory dispersion (ORD) spectroscopy in combination with quantum-chemical calculations. Results and Discussion Decandrinin (1) was obtained as a colorless solid. Its molecular formula was established as C20H28O4 by HRMS (ESI) (m/z

• because there would be several atoms between the concerned protons (Figure S9 in Supporting Information File 1). Therefore, the relative configuration of 1 was identified as shown in Figure 1. The absolute configuration of 1 was assigned by CD and ORD spectroscopy in combination with quantum-chemical

New hydrogen-bonding organocatalysts: Chiral cyclophosphazanes and phosphorus amides as catalysts for asymmetric Michael additions

• Helge Klare,
• Jörg M. Neudörfl and
• Bernd Goldfuss

Beilstein J. Org. Chem. 2014, 10, 224–236, doi:10.3762/bjoc.10.18

• and the OMG group for generous support. We would also like to thank Dr. Nils Schlörer for the NMR measurements, Dr. Matthias Leven for competent advice on quantum chemical calculations and Dipl. Chem. Falco Fox for the preparation of precursors. We thank the RRZK Cologne for computing time.

Less reactive dipoles of diazodicarbonyl compounds in reaction with cycloaliphatic thioketones – First evidence for the 1,3-oxathiole–thiocarbonyl ylide interconversion

• Valerij A. Nikolaev,
• Alexey V. Ivanov,
• Ludmila L. Rodina and
• Grzegorz Mlostoń

Beilstein J. Org. Chem. 2013, 9, 2751–2761, doi:10.3762/bjoc.9.309

• . Victor Baranovski and Dr. Andrey Mereshchenko (St. Petersburg State University) for their help in quantum chemical calculations, and Prof. Anthony Linden (University of Zurich) for the X-ray analysis of 1,3-dithiolane 3a. Skillful help by Dr. K. Urbaniak and Mrs. Małgorzata Celeda in the preparation of

Thermochemistry and photochemistry of spiroketals derived from indan-2-one: Stepwise processes versus coarctate fragmentations

• Götz Bucher,
• Gernot Heitmann and
• Rainer Herges

Beilstein J. Org. Chem. 2013, 9, 1668–1676, doi:10.3762/bjoc.9.191

• useful, but suitable to check the coarctate stereochemical rules, is a peculiar fragmentation reaction that we discovered 15 years ago (Scheme 1) [9][10]. The reaction proceeds spontaneously at temperatures below −80 °C. Quantum chemical calculations of the parent reaction predict an activation barrier

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

• enthalpies and relative values for different compounds (trends) should have an error <1 kcal mol−1. Results and Discussion Theoretical methods and benchmarking Computational details The quantum chemical calculations have been performed with the TURBOMOLE 6.4 suite of programs [34]. All geometry optimizations

Host–guest complexes of mixed glycol-bipyridine cryptands: prediction of ion selectivity by quantum chemical calculations, part V

• Svetlana Begel,
• Ralph Puchta and
• Rudi van Eldik

Beilstein J. Org. Chem. 2013, 9, 1252–1268, doi:10.3762/bjoc.9.142

• , nondynamic quantum chemical calculations, performed in the absence of solvent molecules and focusing on the system itself, were utilized very successfully for the careful examination of the supramolecules, excluding possible disturbing side effects. The current work extends our explorations into the outlined

Substituent effect on the energy barrier for σ-bond formation from π-single-bonded species, singlet 2,2-dialkoxycyclopentane-1,3-diyls

• Jianhuai Ye,
• Yoshihisa Fujiwara and
• Manabu Abe

Beilstein J. Org. Chem. 2013, 9, 925–933, doi:10.3762/bjoc.9.106

• categorized as Type-1 diradicals [1][27], which possess a π-single-bonding character (–π–, closed-shell character) between the two radical sites. The role of the alkoxy group (OR) on the lifetime (k = 1/τ) was investigated by combined studies of experiments and quantum chemical calculations [26][28]. The

Synthesis, photophysical and electrochemical characterization of terpyridine-functionalized dendritic oligothiophenes and their Ru(II) complexes

• Amaresh Mishra,
• Elena Mena-Osteritz and
• Peter Bäuerle

Beilstein J. Org. Chem. 2013, 9, 866–876, doi:10.3762/bjoc.9.100

• nonemissive [Ru(tpy)2]2+ center of the metallodendrimer. Quantum chemical calculations. In order to gain insight into the structural properties, the electron density distribution of the frontier orbitals of both complexes was analyzed by density functional theory (DFT) using the B3LYP/LANL2DZ basis set

Direct alkenylation of indolin-2-ones by 6-aryl-4-methylthio-2H-pyran-2-one-3-carbonitriles: a novel approach

• Sandeep Kumar,
• Ramendra Pratap,
• Abhinav Kumar,
• Brijesh Kumar,
• Vishnu K. Tandon and
• Vishnu Ji Ram

Beilstein J. Org. Chem. 2013, 9, 809–817, doi:10.3762/bjoc.9.92

• desired product. NaH in THF was found to be the most suitable for the alkenylation of indolin-2-ones. Reaction in the presence of other bases led to the formation of 1-aryl-3-methoxy/methylthio-5H-dibenzo[d,f][1,3]diazepin-6(7H)-ones. Quantum chemical calculations have been performed to explain the nature

• isolated compound. Single-crystal X-ray studies revealed that out of the three tautomeric forms, the 8y is the most suitable structure based on the bond lengths. Quantum chemical calculations have been performed in order to gain information regarding the relative energy difference, which in turn reflects

• -oxindoles. Furthermore, the synthesis of 8y and its relative stability with respect to the other tautomers has been confirmed by single-crystal X-ray analysis and quantum chemical calculations. X-ray diffraction displayed various C−H…π, C−H…O and Ar-H…π intermolecular interactions. These interactions have

Caryolene-forming carbocation rearrangements

• Quynh Nhu N. Nguyen and
• Dean J. Tantillo

Beilstein J. Org. Chem. 2013, 9, 323–331, doi:10.3762/bjoc.9.37

• about putting this proposal to the test using quantum chemical calculations [8]. Results and Discussion Structure validation: We first computed 1H and 13C chemical shifts for 1 to assure ourselves that the assigned structure was reasonable [9][10]. Our calculated chemical shifts and the reported data

• biosynthetic precursor to 1. Despite the apparent reasonability of this proposed mechanism, our quantum chemical calculations indicated that the pathway as formulated in Scheme 1 is not energetically viable (see below). Computed mechanism: The first deviation from the proposed mechanism in Scheme 1 was