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