Cycloaddition von N-phenyltriazolindion an 1,5-dialkyl substituierte semibullvalene

Askani, R.; Kirsten, R.; Dugall, B.

doi:10.1016/0040-4020(81)80010-5

Cited by 38 publications

(9 citation statements)

References 45 publications

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“…All attempts to separate the regioisomeric dienes 4 and 9 by flash chromatography failed. Therefore, we tested a method initially developed by Askani for the separation of isomeric semibullvalene precursors via Pd complexes …”

Section: Resultsmentioning

confidence: 93%

“…After 18 h, Pd–diene complex 10 precipitated as a red solid, which was isolated in 45% yield. As observed for related Pd complexes, complex 10 was poorly soluble and thus characterized only by 1 H and 13 C NMR. According to 1 H NMR spectra the filtrate consisted of a 68:32 mixture of 4a / 9a with regioisomer 4a as the major compound.…”

Section: Resultsmentioning

confidence: 93%

“…According to 1 H NMR spectra the filtrate consisted of a 68:32 mixture of 4a / 9a with regioisomer 4a as the major compound. Decomplexation of 10 with a saturated KCN solution in the presence of K 2 CO 3 in pentane at room temperature gave exclusively regioisomer 4a with 92% ee as determined by analytical HPLC on a chiral Chiracel OJ-H column, however, only in a meager 33% yield. Further attempts were therefore abandoned, and we focused on the separation of regioisomers 4 / 9 by preparative HPLC using various chiral stationary phases.…”

Section: Resultsmentioning

confidence: 99%

“…Such decrease of the enantioselectivity was indeed experimentally observed (see, for example, Table , entry 4 vs 5 and entry 11 vs 14). The palladium complexation of tetrahydropentalene derivatives is known to proceed via isomerization of the double bond . Taking this finding into account an analogous Rh-catalyzed isomerization of ligand 9a may lead to partial racemization of regioisomer 4a and thus decreased enantioselectivity.…”

Section: Resultsmentioning

confidence: 99%

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Role of Regioisomeric Bicyclo[3.3.0]octa-2,5-diene Ligands in Rh Catalysis: Synthesis, Structural Analysis, Theoretical Study, and Application in Asymmetric 1,2- and 1,4-Additions

et al. 2017

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In order to study the impact of regioisomeric diene ligands on the formation and catalytic activity of Rh complexes, a series of C- and C-symmetric 2,5-disubstituted bicyclo[3.3.0]octa-2,5-dienes C-L and C-L, respectively, were synthesized from Weiss diketone by simultaneous deprotonation/electrophilic trapping of both oxo functions, and the catalytic behavior was studied in the presence of [RhCl(CH)]. Complexes [RhCl(C-L)] bearing C-symmetric ligands catalyzed effectively the asymmetric arylation of N-tosylaldimines to (S)-diarylamines with yields and ee values up to 99%. In Hayashi-Miyaura reactions, however, the complexes showed poor catalytic activity. When complexes [RhCl(C-L)] with C-symmetric ligand or mixtures of [RhCl(C-L)] and [RhCl(C-L)] were employed in 1,2-additions, racemic addition products were observed, suggesting a C═C isomerization of the diene ligands. X-ray crystal structure analysis of both Rh complexes formed from the [RhCl(CH)] precursor and ligands C-L and C-L revealed that only the C-symmetric ligand C-L coordinated to the Rh, whereas C-L underwent a Rh-catalyzed C═C isomerization to rac-C-L, which then gave the racemic [RhCl(rac-C-L)] complex. DFT calculations of the relative stabilities of the Rh complexes and the proposed intermediates provided a mechanistic rationale via Rh-mediated hydride transfer.

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Section: Resultsmentioning

confidence: 93%

Section: Resultsmentioning

confidence: 93%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 2 more Smart Citations

Role of Regioisomeric Bicyclo[3.3.0]octa-2,5-diene Ligands in Rh Catalysis: Synthesis, Structural Analysis, Theoretical Study, and Application in Asymmetric 1,2- and 1,4-Additions

et al. 2017

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“…The semibullvalenes 1b, [19] 13a, [20] b, [21] and 17 [22] used in this study were available from previous work. 1,5-Dimethylcyclooctatetraene (2b) has been synthesized from 1b by flash vacuum pyrolysis.…”

Section: Methods and Resultsmentioning

confidence: 99%

Thermal Isomerisation of Substituted Semibullvalenes and Cyclooctatetraenes – A Kinetic Study

Quast¹,

Heubes

Dietz

et al. 1999

Eur. J. Org. Chem.

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Whereas 1,5‐dimethylsemibullvalene (1b) equilibrates with 1,5‐dimethylcyclooctatetraene (2b), the semibullvalene‐2,6‐dicarbonitriles 13 rearrange irreversibly to afford mixtures of the isomeric cyclooctatetraene‐1,5‐dicarbonitriles 14 and 15. Arrhenius and Eyring parameters of these thermal isomerisation reactions have been determined for the gas phase (1b → 2b) and [D6]benzene solutions (1b → 2b, 13 → 14 + 15). Furthermore, the activation parameters of the known rearrangement of octamethylcyclooctatetraene (3) to octamethylsemibullvalene (4) have been determined. – The data for these compounds, together with those for related compounds previously reported in the literature, show that substituents not only influence the relative stabilities of the semibullvalene and cyclooctatetraene systems but also the height of the energy barrier for their interconversion. Those substituents that lower the barrier toward the degenerate Cope rearrangement of semibullvalenes simultaneously accelerate their rearrangement to cyclooctatetraenes thus limiting the thermal stability of the former.

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Condensation of Dimethyl 1,3‐Acetonedicarboxylate with 1,2‐Dicarbonyl Compounds: cis ‐bicyclo[3.3.0]octane‐3,7‐diones

et al. 2003

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Condensation of Dimethyl 1,3‐Acetonedicarboxylate with 1,2‐Dicarbonyl Compounds: cis ‐Bicyclo[3.3.0]octane‐3,7‐diones intermediate: Tetramethyl 3,7‐dihydroxybicyclo[3.3.0]octa‐2,6‐diene‐2,4,6,8‐tetracarboxylate product: cis‐Bicyclo[3.3.0]octane‐3,7‐dione intermediate: Tetramethyl 3,7‐dihydroxy‐1,5‐dimethylbicyclo[3.3.0]octa‐2,6‐diene‐2,4,6,8‐tetracarboxylate product: cis‐1,5‐Dimethylbicyclo[3.3.0]octane‐3,7‐dione intermediate: C16H16O10Na2·H2O

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Cycloaddition von N-phenyltriazolindion an 1,5-dialkyl substituierte semibullvalene

Cited by 38 publications

References 45 publications

Role of Regioisomeric Bicyclo[3.3.0]octa-2,5-diene Ligands in Rh Catalysis: Synthesis, Structural Analysis, Theoretical Study, and Application in Asymmetric 1,2- and 1,4-Additions

Role of Regioisomeric Bicyclo[3.3.0]octa-2,5-diene Ligands in Rh Catalysis: Synthesis, Structural Analysis, Theoretical Study, and Application in Asymmetric 1,2- and 1,4-Additions

Thermal Isomerisation of Substituted Semibullvalenes and Cyclooctatetraenes – A Kinetic Study

Condensation of Dimethyl 1,3‐Acetonedicarboxylate with 1,2‐Dicarbonyl Compounds: cis ‐bicyclo[3.3.0]octane‐3,7‐diones

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