The Effects of Fluorine and Chlorine Substituents across the Fjords of Bifluorenylidenes: Overcrowding and Stereochemistry

Pogodin, Sergey; Rae, Ian D.; Agranat, Israel

doi:10.1002/ejoc.200600460

Cited by 20 publications

(14 citation statements)

References 39 publications

(60 reference statements)

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“…DFT methods are capable of generating a variety of isolated molecular properties quite accurately, especially with the aid of the hybrid functional, and in a cost‐effective way 35,36. The B3LYP hybrid functional has been successfully employed to treat BAEs37,38 and overcrowdednaphtho analogues of mono‐bridged tetraarylethylenes 18. The PAEs 3 and 4 , the siloxane anions 18 and 16 , the β‐hydroxysilanes 19 and 20 (the O ‐protonated derivatives of the β‐oxysilanes 11 and 15 , respectively), the lithium salts 21 and 22 of 11 and 15 , respectively, the 1‐naphthyl anion ( Z )‐ 12 , the 3‐naphthyl anion ( Z )‐ 14 , the phenyl anion ( Z )‐ 13 , and the parent 1‐naphthalenyl anion 23 and 2‐naphthanenyl anion 24 were subjected to a computational DFT study of their conformations.…”

Section: Resultsmentioning

confidence: 99%

Peterson Olefination: Unexpected Rearrangement in the Overcrowded Polycyclic Aromatic Ene Series

2011

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An attempted synthesis of the angularly annelated 9-(11Ј-benzo[a]fluoren-11Ј-ylidene)-9H-fluorene (3) through a Peterson olefination reaction between (9H-fluoren-9-yl)trimethylsilyl anion (5a) and 11H-benzo[a]fluoren-11-one (6) led to the linearly annelated 9-(11Ј-benzo[b]fluoren-11Ј-ylidene)-9H-fluorene (4), due to an unexpected rearrangement. The proposed mechanism of the rearrangement is illustrated. The core of the mechanism is an intramolecular Haller-Bauer cleavage of the naphthyl C 11aЈ -C 11Ј bond in the β-oxysilane

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Section: Resultsmentioning

confidence: 99%

Peterson Olefination: Unexpected Rearrangement in the Overcrowded Polycyclic Aromatic Ene Series

2011

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“…For example, B3LYP has been compared to 36 other density functionals on the set of 44 small organic molecules, and has been ranked second best for bond lengths calculations, seventh for barrier heights calculations, and ninth for hydrogen‐bonding binding energies . Recently, the B3LYP hybrid functional was successfully employed to treat dinaphthyl ketones, dinaphthyl thioketones, and dinaphthyl diazomethanes and overcrowded BAEs . However, B3LYP often fails to accurately represent London dispersion interactions, often underestimating interaction energies of dispersion and dipole–dipole bound complexes .…”

Section: Methodsmentioning

confidence: 99%

Single Enantiomer Versus Racemate: Chiral Distinction in the Proton Pump Inhibitors Omeprazole and Esomeprazole

2014

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Chiral distinction in the proton pump inhibitor drugs omeprazole and in its chiral-switch esomeprazole magnesium was studied employing the Density Functional Theory (DFT) method. At B3LYP/6-311G(d,p), the 6-methoxy∙∙∙6-methoxy and 5-methoxy∙∙∙5-methoxy homochiral and heterochiral dimers were calculated. The chiral distinction free energies (ΔΔG(298,(RS-SS))) between the cyclic C2-(S,S)- and Ci-(R,S)-dimers with two intermolecular hydrogen bonds are 3.8, 1.9 (with BSSE counterpoise correction), and -6.9 (with D3 dispersion and BSSE counterpoise corrections) kJ/mol. Adding water as an implicit solvent (polarized continuum model [PCM] model) resulted in a chiral distinction energy of -3.3 kJ/mol, indicating a reversal of the order of the relative stabilities of C2-(S,S)- and Ci-(R,S)-dimers. The chiral distinction free energies between the corresponding (less stable) C1-dimers with one intermolecular hydrogen bond are -9.3, -5.8 (with BSSE CC), 17.6 (D3 + BSSE CC), and -3.2 (H2O) kJ/mol. The results highlight the contention that omeprazole is not just a superposition of its enantiomer constituents. They are consistent with the pharmacological evidence of enantiomer-enantiomer interactions in omeprazole versus esomeprazole and the differences between the drugs omeprazole and esomeprazole magnesium and support the lodged application for regulatory supplementary protection certificate (SPC) exclusivity for the esomeprazole-related combination drug Vimovo.

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“…Recently, the B3LYP hybrid functional was successfully employed to treat dinaphthyl ketones, dinaphthyl thioketones and dinaphthyl diazomethanes [42], and overcrowded BAEs [18,52,53]. However, B3LYP often fails to accurately represent London dispersion interactions, often underestimating interaction energies of dispersion and dipole-dipole bound complexes [50].…”

Section: Dft Studymentioning

confidence: 98%

Variations of bistricyclic aromatic enes: mono-bridged tetraarylethene naphthologs

et al. 2014

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The syntheses, molecular and crystal structures, NMR spectroscopic study, and DFT computational study of naphthologs of mono-bridged (X = -, O, S, Se, and Te) tetraarylethene (BAE-1s) 11-25 with a,a-, b,b-, and a,b-dinaphthalenyl substituents have been reported. The BAE-1s have been prepared by Barton-Kellog twofold extrusion from the respective chalcogenothiones and diazomethylenebisnaphthylenes. Complete assignments of 1 Hand 13 C-NMR spectra of 11-25 have been made through 2-dimensional correlation spectroscopy (DQF-COSY, HSQC, HMBC, and NOESY). The corresponding intermediates, thiiranes 33-47, have been also isolated (except 38), and their molecular and crystal structures have been determined. The molecular structures of BAE-1s 12-15, 20, and 22-25 adopted folded-twisted conformations with considerably folded (u = 30°-57°) tricyclic moieties. The a,a-and a,b-dinaphthalenyl derivatives are more overcrowded than b,b-dinaphthalenyl derivatives. The relief of the steric strain due to the overcrowding around C 9 = C 9 0 caused by the presence of naphthalenyl substituents was achieved by their twisting around the single bonds that connect the a-naphthalenyl and b-naphthalenyl moieties to C 9 0 . The 1 H-NMR spectra have shown shielding of H 2 , H 7 of 11-25 and the pronounced deshielding of H 8 0 , H 8 00 of a,a-dinaphthalenyl-substituted BAE-1s 13-15 in contrast to b,b-dinaphthalenyl-substituted BAE-1s 16-20. The upfield shifts of H 2 , H 7 suggested conformations in which these hydrogens are located above the planes of the opposing naphthalene rings. DFT calculations of 11-20 have been performed at B3LYP/6-31G(d) and B3LYP/ SDD. The results have shown that the global minima of BAE-1s without a chalcogen bridge 11 and 16 are twisted (-sc,-sc)-C 2 -t conformations. The global minima of BAE1s with a chalcogen bridge are folded-twisted (-sc,-ac)-C 1 -ft conformations for a,a-dinaphthalenyl-substituted BAE1s 12-15 and either anti-or syn-(-sc,ac)-C 1 -ft conformations for b,b-dinaphthalenyl-substituted BAE-1s 17-20. The pronounced differences between the a,a-dinaphthalenyl and the b,b-dinaphthalenyl derivatives are noted. Dispersion-corrected B3LYP calculations stabilize significantly the a,a-dinaphthalenyl derivatives versus the b,b-dinaphthalenyl derivatives. The geometrical parameters of BAEs-1 11-15 and 20, derived from their molecular X-ray structures and from their B3LYP-optimized geometries are in a good agreement.

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The Effects of Fluorine and Chlorine Substituents across the Fjords of Bifluorenylidenes: Overcrowding and Stereochemistry

Cited by 20 publications

References 39 publications

Peterson Olefination: Unexpected Rearrangement in the Overcrowded Polycyclic Aromatic Ene Series

Peterson Olefination: Unexpected Rearrangement in the Overcrowded Polycyclic Aromatic Ene Series

Single Enantiomer Versus Racemate: Chiral Distinction in the Proton Pump Inhibitors Omeprazole and Esomeprazole

Variations of bistricyclic aromatic enes: mono-bridged tetraarylethene naphthologs

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