Schrittweiser Donorbasenaustausch in Anthracenyllithiumverbindungen

Stern, Daniel; Finkelmeier, Nils; Meindl, Kathrin; Henn, Julian

doi:10.1002/ange.201002873

Cited by 12 publications

(15 citation statements)

References 49 publications

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“…Additionally solvent molecules can associate and dissociate in solution. 31 Therefore we anticipate that the space between all atoms is less packed than in the “sigma bonded-compact spheres” model. On the other hand alkaline organometallics frequently adopt spherical and ellipsoidal shapes, according to the ring-stacking principle.…”

Section: Resultsmentioning

confidence: 99%

Accurate molecular weight determination of small molecules via DOSY-NMR by using external calibration curves with normalized diffusion coefficients

2015

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Section: Resultsmentioning

confidence: 99%

Accurate molecular weight determination of small molecules via DOSY-NMR by using external calibration curves with normalized diffusion coefficients

2015

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“…In a first series of exploratory experiments, we treated 9,10‐dibromo‐DBA ( A ; R 1 =R 2 =Br)13 with two equivalents of 9‐lithioanthracene36 in diethyl ether and obtained a brick‐red microcrystalline solid, which was insoluble in all common solvents. We therefore decided to introduce solubilizing side chains into the 9‐anthryl substituents and selected the readily available 2,6‐di‐ tert ‐butyl derivative for further investigations.…”

Section: Resultsmentioning

confidence: 99%

Boron‐Doped Tri(9,10‐anthrylene)s: Synthesis, Structural Characterization, and Optoelectronic Properties

Hoffend

Schödel

Bolte

et al. 2012

Chemistry A European J

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The reaction of 9,10-dibromo-9,10-dihydro-9,10-diboraanthracene (9,10-dibromo-DBA, 3) with two equivalents of 9-lithio-2,6- or 9-lithio-2,7-di-tert-butylanthracene gave the corresponding 9,10-dianthryl-DBAs featuring two (4) or four (5) inward-pointing tert-butyl groups. Compound 4 exists as two atropisomers, 4 and 4', due to hindered rotation about the exocyclic B-C bonds. X-ray crystallography of 5 suggests that the overall interactions between facing tert-butyl groups are attractive rather than repulsive. Even in solution, 4/4' and 5 are stable toward air and moisture for several hours. Treatment of 3 with 10-lithio-9-R-2,7-di-tert-butylanthracenes carrying phenyl (R=Ph), dimesitylboryl (R=Mes(2)B), or N,N-di(p-tolyl)amino (R=Tol(2)N) groups gave the corresponding 9,10-dianthryl-DBA derivatives 9-11 in moderate to good yields. In these molecules, all four solubilizing tert-butyl groups are outward pointing. The solid-state structures of 4, 5, 9, and 10 reveal twisted conformations about the exocyclic B-C bonds with dihedral angles of 70-90°. A significant electron-withdrawing character was proven for the Mes(2)B moiety, but no appreciable +M effect was evident for Tol(2)N. Compounds 5, 9, and 11 show two reversible DBA-centered reduction waves in the cyclic voltammogram. In the case of 10, a third reversible redox transition can be assigned to the Mes(2)B-anthryl substituents. The UV/Vis absorption spectrum of 5 is characterized by a very broad band at λ(max)=510 nm, attributable to a twisted intramolecular charge-transfer interaction from the anthryl donors to the DBA acceptor. The corresponding emission band shows pronounced positive solvatochromism (λ(em)=567 nm, C(6)H(12); 680 nm, CH(2)Cl(2)) in line with a highly polar excited state. The charge-transfer bands of 10 and 11, as well as the emission bands of 9 and 10, are redshifted relative to those of 5. The Tol(2)N derivative 11 is essentially nonfluorescent in solution, but emits bright wine-red light in the solid state.

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“…In the case of 1-Li, in the presence of TMEDA, the nature of the CÀLi bond was significantly affected and the racemization rate was reduced considerably in THF and completely blocked in hexane. [17] a-Lithiated p-trifluoromethylstyrene oxide (2-Li), generated in THF/Et 2 O (3:2) by lithiation of optically active (R)-2 (99:1 e.r.) with sBuLi (1.5 equiv), was found to undergo faster racemization than the meta isomer 1-Li even at a temperature as low as 157 K (t 1/2 = 14 s, DG 6 ¼ enant = 10.1 AE 0.1 kcal mol À1 ).…”

Section: Resultsmentioning

confidence: 99%

Solvent and TMEDA Effects on the Configurational Stability of Chiral Lithiated Aryloxiranes

Perna¹,

Salomone²,

Dammacco³

et al. 2011

Chemistry A European J

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The employment of hexane/N,N,N',N'-tetramethylethylenediamine (TMEDA) dramatically hinders the racemization of those lithiated styrene oxides (trifluoromethyl-, chloro-, and phenylthio-substituted) that have been proven to be configurationally unstable in THF on the timescale of their reactions. The barriers to inversion and the activation parameters, calculated (Eyring equation) for reactions performed in THF, THF/TMEDA, and hexane/TMEDA, suggest the intervention of particular enantiomerization mechanisms for each case. The role of TMEDA in both coordinating and noncoordinating solvents has also been questioned and discussed in light of the kinetic data gathered and a model for deprotonation in hexane/TMEDA has also been proposed. The synthetic benefits of our results became apparent on establishing an asymmetric synthesis of an industrially important antifungal agent.

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Schrittweiser Donorbasenaustausch in Anthracenyllithiumverbindungen

Cited by 12 publications

References 49 publications

Accurate molecular weight determination of small molecules via DOSY-NMR by using external calibration curves with normalized diffusion coefficients

Accurate molecular weight determination of small molecules via DOSY-NMR by using external calibration curves with normalized diffusion coefficients

Boron‐Doped Tri(9,10‐anthrylene)s: Synthesis, Structural Characterization, and Optoelectronic Properties

Solvent and TMEDA Effects on the Configurational Stability of Chiral Lithiated Aryloxiranes

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