Neues aus der Bullvalen‐Chemie

Schröder, Gerhard; Oth, Jean F. M.

doi:10.1002/ange.19670791004

Cited by 67 publications

(14 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…940 sec-1 ; this corresponds to . :lG* = 9.7 kcal/mole, a value in good accord with that observed for the valence isomerizations in homotropylidenes bridged by two carbon atoms as shown in formula VIII [14].…”

Section: VIIsupporting

confidence: 86%

Cyclooctatetraene Tetramer

Hoesch¹,

Dreiding²,

Oth³

1972

Israel Journal of Chemistry

View full text Add to dashboard Cite

The constitution of the cyclooctatetraene tetramer, mp 182° (VI), is derived from its spectroscopic properties and from the results of catalytic hydrogenation experiments. The 1H‐NMR spectrum of VI is temperature dependent and indicates the presence of two homotropylidene residues in the molecule, one isomerizing isodynamically, the other anisodynamically. The mass spectrum of VI shows remarkable similarities with those of the cyclooctatetraene dimer, mp 76° (III) and of bullvalene (IX). The tetramer VI is concluded to be the product of a 2 + 4‐cycloaddition reaction between the cyclohexa‐1,3‐diene units of two molecules of III. The tetramer VI appears to be configurationally unique. This is explained and a configuration is proposed on the basis of the stereospecificity of the reaction leading to VI.

show abstract

Section: VIIsupporting

confidence: 86%

Cyclooctatetraene Tetramer

Hoesch¹,

Dreiding²,

Oth³

1972

Israel Journal of Chemistry

View full text Add to dashboard Cite

show abstract

“…The results of[14] had only preliminary character, and the measured data of[16] are the most recent and reliable values.…”

mentioning

confidence: 99%

Density Functional Study of the Oxy-Cope Rearrangement

Baumann¹,

Chen²

2001

HCA

View full text Add to dashboard Cite

With the goal of explaining the very large rate acceleration in the anion-assisted Cope rearrangement, the behavior of the prototypes of the Cope rearrangements, namely hexa-1,5-diene (4), hexa-1,5-dien-3-ol (5), and the oxy anion 6 of the latter were compared. For this purpose, two-dimensional DFT (hybrid B3LYP functionals with 6-31G* basis set) potential-energy surfaces (PESs) were computed, based on two interatomic distances. As the reliability of DFT/B3LYP-computed energies can not be taken for granted, we first performed model computations on the experimentally well-studied bridged homotropylidenes 1 ± 3. Then, the transition states of the Cope rearrangements of 3-methylhexa-1,5-dien-3-ol (7), (2Z,4Z,7Z)-cyclonona-2,4,7-trien-1-ol (9), 1-methoxy-2-endo-vinylbicyclo[2.2.2]oct-5-en-2-exo-ol (11), and (1S,2R)-2-hydroxy-1-methyl-2-vinylbicyclo[4.4.0]dec-6-en-8-one (arbitrary numbering; 13) and of their oxy anions 8, 10, 12, and 14, respectively, were computed by the same method. These examples were chosen because kinetic data have been measured for most of them (except for 13 and 14) and/or because they furnished already important contributions to the discussion of the character of the Cope rearrangement. The computation of DG = for a given temperature allowed to calculate the rate constants at that temperature for the different rearrangements and to compare them with the experimental data. In the cases of the neutral and anionic oxy-Cope rearrangements, the equation DDG = 2.3026´RT´DpK a suggested a correlation between the difference in the pK a values of the pair of reactants and the pair of transition states and the change of the two free energies of activation.

show abstract

“…In the bottom lines of Table 4 we have quoted the isotropic shieldings at the bullvalene nuclei under the premise of a dynamical equivalence between all 13 C ( 1 H) centres C av (H av ). It is this behaviour that is observed in NMR under ''fast'' isomerization conditions [18,[20][21][22].…”

Section: Absolute Isotropic Shieldings In the Presence Of The Cope Rementioning

confidence: 86%

“…The first example studied with this intention is the C 10 H 10 hydrocarbon tricyclo[3.3.2.0 4,6 ]deca-2,7,9-triene (= bullvalene) [18][19][20] shown in Fig. 1.…”

Section: Introductionmentioning

confidence: 99%