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

• chelotropic elimination of 1,3-dioxolan-2-ylidene is not likely. This carbene has been generated from a norbornadiene spiro ketal, and it cleanly fragmented into CO2 and ethylene [30]. Theoretical calculations support the low barrier for fragmentation [31]. We explain the different reaction behaviour of our

Conformational analysis and intramolecular interactions in monosubstituted phenylboranes and phenylboronic acids

• Josué M. Silla,
• Rodrigo A. Cormanich,
• Roberto Rittner and
• Matheus P. Freitas

Beilstein J. Org. Chem. 2013, 9, 1127–1134, doi:10.3762/bjoc.9.125

• goals, NMR spectroscopy (by means of suitable coupling constants) and theoretical calculations were used. Second-order perturbation analysis of donor–acceptor interactions in the natural bond orbitals (NBO) was used to interpret conformational isomerism in terms of hyperconjugative interactions, in such

• ca. 2 mg mL−1 in benzene-d6 and 20 mg mL−1 in CD3CN solutions. The infrared spectrum was acquired in a BOMEM MB100 spectrometer from 0.1 M CDCl3 solution, using a liquid cell with NaCl windows and 0.5 mm spacer, collecting 32 scans at 1 cm−1 resolution. For the theoretical calculations, a Monte Carlo

An aniline dication-like transition state in the Bamberger rearrangement

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

Beilstein J. Org. Chem. 2013, 9, 1073–1082, doi:10.3762/bjoc.9.119

• rearrangement. Theoretical calculations The reacting systems were investigated by density functional theory (DFT) calculations. The B3LYP [8][9] method was used to trace the reaction path. The basis sets employed were 6-31G(d) and 6-311+G(d,p), where the latter was adopted for the key (OH transfer) steps. For

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

• further supported by theoretical calculations (see below). For ligands 8 and 9, with increasing generation of the dendron from G1 and G2, a slight red-shift in the lowest energy absorption maximum and a significant enhancement in the molar absorption coefficient were observed. Furthermore, the absorption

Asymmetric Diels–Alder reaction with >C=P– functionality of the 2-phosphaindolizine-η¹-P-aluminium(O-menthoxy) dichloride complex: experimental and theoretical results

• Rajendra K. Jangid,
• Nidhi Sogani,
• Neelima Gupta,
• Raj K. Bansal,
• Moritz von Hopffgarten and
• Gernot Frenking

Beilstein J. Org. Chem. 2013, 9, 392–400, doi:10.3762/bjoc.9.40

• DA reactions of 2-phosphaindolizine-η1-P-AlEtCl2 complexes [21]. Theoretical calculations at the DFT (B3LYP/6-31+G**) level indicated lowering of the activation barrier by 6 kcal mol–1 for the reaction of σ2,λ3-P-coordinated 2-phosphindolizine to methylaluminium dichloride with 1,3-butadiene as

Metal-mediated aminocatalysis provides mild conditions: Enantioselective Michael addition mediated by primary amino catalysts and alkali-metal ions

• Matthias Leven,
• Jörg M. Neudörfl and
• Bernd Goldfuss

Beilstein J. Org. Chem. 2013, 9, 155–165, doi:10.3762/bjoc.9.18

• measurements were repeated three times and three samples were prepared to give identical results. Computational details. All theoretical calculations were performed with the program package TURBOMOLE-6.3 [34]. The employed density functionals were the nonempirical TPSS-functional developed by Tao, Perdew

Photoreactions of cyclic sulfite esters: Evidence for diradical intermediates

• Rick C. White,
• Benny E. Arney Jr. and
• Heiko Ihmels

Beilstein J. Org. Chem. 2012, 8, 1208–1212, doi:10.3762/bjoc.8.134

• biradical BR2 with a conformation that is unfavorable for oxirane formation, but enables efficient hydrogen migration to result in aldehyde 3a. Theoretical calculations have confirmed that acetaldehyde derivatives may be formed upon rearrangement of the 1,3-oxyethandiyl [20][21] and that a subsequent

Enantioselective supramolecular devices in the gas phase. Resorcin[4]arene as a model system

• Caterina Fraschetti,
• Matthias C. Letzel,
• Antonello Filippi,
• Maurizio Speranza and
• Jochen Mattay

Beilstein J. Org. Chem. 2012, 8, 539–550, doi:10.3762/bjoc.8.62

• experimentally considered: The configuration of the amine B and that of the guest G. According to theoretical calculations, the chiral effects are insignificant if the guest molecule in the [YS∙H∙G]+ complex is located outside the cavity of the host, while a bimodal kinetic is mirrored by the coexistence of a

Intramolecular carbenoid ylide forming reactions of 2-diazo-3-keto-4-phthalimidocarboxylic esters derived from methionine and cysteine

• Marc Enßle,
• Stefan Buck,
• Roland Werz and
• Gerhard Maas

Beilstein J. Org. Chem. 2012, 8, 433–440, doi:10.3762/bjoc.8.49

• is remarkable. In this geometry, however, p(Cylide)–σ*(S–C) conjugation of the unshared pair of electrons at the ylidic carbon atom would be feasible. While this interaction is a key stabilisation factor for the parent sulfonium ylides (e.g., H2S–CH2 and Me2S–CH2) according to theoretical

• calculations [24], its energetic contribution in the case of sulfonium ylides stabilised by acceptor substituents is likely to be small. The oxazapolycycles 13a and b are head-to-tail dimers of carbonyl ylides, resulting from a [3 + 3]-cycloaddition. Their constitution and relative stereochemistry was assigned

Synthesis of multivalent host and guest molecules for the construction of multithreaded diamide pseudorotaxanes

• Nora L. Löw,
• Egor V. Dzyuba,
• Boris Brusilowskij,
• Lena Kaufmann,
• Elisa Franzmann,
• Wolfgang Maison,
• Emily Brandt,
• Daniel Aicher,
• Arno Wiehe and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2012, 8, 234–245, doi:10.3762/bjoc.8.24

• view of previous theoretical calculations on amide/tetralactam macrocycle complexes [111], which show that simple amide axles dethread in the gas phase because of a favourable entropy term arising from the increase in particle number upon complex dissociation. This entropic contribution overcompensates

Computational evidence for intramolecular hydrogen bonding and nonbonding X···O interactions in 2'-haloflavonols

• Tânia A. O. Fonseca,
• Matheus P. Freitas,
• Rodrigo A. Cormanich,
• Teodorico C. Ramalho,
• Cláudio F. Tormena and
• Roberto Rittner

Beilstein J. Org. Chem. 2012, 8, 112–117, doi:10.3762/bjoc.8.12

• interactions; theoretical calculations; Introduction Intermolecular hydrogen bonding (HB) is an interaction governing self-assembly and is responsible for the architecture and organization of molecular aggregates [1], and also ligand–receptor interactions that are responsible for the bioactivity of compounds

• (antioxidant, anti-inflammatory, antiviral, etc.) [12]. The goal of this work is to understand the intramolecular forces determining the preferred conformations of these molecules through the use of DFT theoretical calculations, quantum theory of atoms in molecules (QTAIM) [13][14][15][16][17] and natural bond

Valence isomerization of cyclohepta-1,3,5-triene and its heteroelement analogues

• Helen Jansen,
• J. Chris Slootweg and
• Koop Lammertsma

Beilstein J. Org. Chem. 2011, 7, 1713–1721, doi:10.3762/bjoc.7.201

• necessitates a brief overview of the parent all-carbon system. This section is followed by one in which experimental data on the oxepine, thiepine, 1H-azepine, and 1H-phosphepine valence isomerizations are compared with those obtained by theoretical calculations. Computational methods have the advantage that

• stern (β) tilt angles) with those determined by electron diffraction standing out. Theoretical calculations at the B3LYP/6-311+G(d,p) level gave α and β angles of 52.9° and 25.4°, respectively [15][16][17], which are in reasonable harmony with those of the microwave and X-ray studies. Low temperature 1H

• -shape structure with alternating C=C bonds for 3 [39][40], which was supported by single-crystal X-ray structure analyses of simple derivatives [41]. Table 1 also summarizes the relative energies obtained by high-level theoretical calculations for the parent heteropines and the corresponding bicyclic

Meta-metallation of N,N-dimethylaniline: Contrasting direct sodium-mediated zincation with indirect sodiation-dialkylzinc co-complexation

• David R. Armstrong,
• Liam Balloch,
• Eva Hevia,
• Alan R. Kennedy,
• Robert E. Mulvey,
• Charles T. O'Hara and
• Stuart D. Robertson

Beilstein J. Org. Chem. 2011, 7, 1234–1248, doi:10.3762/bjoc.7.144

• ratio. Interestingly, when the TMP(H) containing solution was heated under reflux for 18 hours more meta-isomer was produced (corresponding ratio 3.7:4.2:1.0). It is likely that this change has its origin in a retro reaction that produces the original base 1 as an intermediate. Theoretical calculations

• molecule. DFT calculations In an attempt to rationalise the different metallation regioselectivities afforded by the homo and heterobimetallic bases, theoretical calculations at the DFT level using the B3LYP method and the 6-311G** basis set were employed to compute the relative stabilities of the four

Recent developments in gold-catalyzed cycloaddition reactions

• Fernando López and
• José L. Mascareñas

Beilstein J. Org. Chem. 2011, 7, 1075–1094, doi:10.3762/bjoc.7.124

• with a gold(I) catalyst bearing a π-acceptor ligand, such as a triarylphosphite (Au8/AgSbF6, Scheme 28) [98][99][102][103]. Several experimental results as well as theoretical calculations suggest that the observed (4 + 2) cycloadducts 53 are indeed the result of a ring contraction process (1,2-alkyl

Solvent- and ligand-induced switch of selectivity in gold(I)-catalyzed tandem reactions of 3-propargylindoles

• Estela Álvarez,
• Delia Miguel,
• Patricia García-García,
• Manuel A. Fernández-Rodríguez,
• Félix Rodríguez and
• Roberto Sanz

Beilstein J. Org. Chem. 2011, 7, 786–793, doi:10.3762/bjoc.7.89

• gold variants of the Nazarov (cyclization from 2 to 4) or iso-Nazarov reactions (cyclization from 2 to 3) [14]. These theoretical calculations also showed that in those cases where both cyclization pathways are possible (for example in 2a arising from 1a; Scheme 1), the calculated energy barriers for

Molecular rearrangements of superelectrophiles

• Douglas A. Klumpp

Beilstein J. Org. Chem. 2011, 7, 346–363, doi:10.3762/bjoc.7.45

• -diprotonated species 93. Migration of the methyl group leads to separation of the charge centers and the formation of dication 94. Theoretical calculations show that hydride shift for the dications (94 → 95) is energetically unfavorable, presumably due to the closer proximity of the charges. In the final steps

Reciprocal polyhedra and the Euler relationship: cage hydrocarbons, C_nH_n and closo-boranes [B_xH_x]²⁻

• Michael J. McGlinchey and
• Henning Hopf

Beilstein J. Org. Chem. 2011, 7, 222–233, doi:10.3762/bjoc.7.30

• , prepared in 8% yield simply by heating the phosphaalkyne t-BuC≡P, 77, at 130 °C for several days (Scheme 17) [50]. Finally, we note an interesting recent paper that reported high level theoretical calculations on the structures and stabilities of heterocubanes [XY]4 comprised of Group 13 (X = B, Al, Ga

SbCl₃-catalyzed one-pot synthesis of 4,4′-diaminotriarylmethanes under solvent-free conditions: Synthesis, characterization, and DFT studies

• Ghasem Rezanejade Bardajee

Beilstein J. Org. Chem. 2011, 7, 135–144, doi:10.3762/bjoc.7.19

• performing theoretical calculations at the HF and DFT levels of theory by standard 6-31G*, 6-31G*/B3LYP, and B3LYP/cc-pVDZ methods and good agreement was obtained between experimental and theoretical results. Keywords: diaminotriarylmethane; SbCl3; solvent-free reactions; synthesis; vibrational analysis

• performed theoretical calculations with compound 11 as the model compound (Figure 1). All theoretical calculations were carried out with the GAMESS program [46]. The first stage for geometry optimization of this molecule was completed by the standard HF/6-31G* method. The resulted HF geometry was then

• prepare a wide range of products are the advantages of this protocol. Molecular geometry parameters and vibrational wavenumbers of the triarylmethanes have been obtained from theoretical calculations for the first time. The theoretical results show good agreement between theoretical and experimental data

Quinoline based receptor in fluorometric discrimination of carboxylic acids

• Kumaresh Ghosh,
• Suman Adhikari,
• Asoke P. Chattopadhyay and
• Purnendu Roy Chowdhury

Beilstein J. Org. Chem. 2008, 4, No. 52, doi:10.3762/bjoc.4.52

• ring protons (Figure 14) during complexation with citric acid. The quinoline ring protons (marked with asterisks in Figure 14) suffer a downfield shift upon complexation and led us to presume a weak edge to face type π-stacking interaction between the pendant quinolines. Theoretical calculations on

High stereoselectivity on low temperature Diels- Alder reactions

• Luiz Carlos da Silva Filho,
• Valdemar Lacerda Júnior,
• Mauricio Gomes Constantino,
• Gil Valdo José da Silva and
• Paulo Roberto Invernize

Beilstein J. Org. Chem. 2005, 1, No. 14, doi:10.1186/1860-5397-1-14

• spectroscopic and spectrometric methods (1H NMR, 13C NMR, IR and mass spectra). A detailed NMR analysis and theoretical calculations with total assignment of 1H and 13C NMR data for compounds 9a and 9b was recently published [16]. As observed in Table 1, unsubstituted 2-cycloenones 1 and 2 react well with