Tandem radical addition–aldol condensations: evidence for the formation of zinc enolates in diethylzinc mediated radical additions to N-enoyloxazolidinones

International audienc

Tandem Radical Addition—Aldol Condensations: Evidence for the Formation of Zinc Enolates in Diethylzinc Mediated Radical Additions to N-Enoyloxazolidinones.

International audienc

Chiral Nanographene Propeller Embedding Six Enantiomerically Stable [5]Helicene Units

A one-step synthesis of a nanographene propeller with a D3-symmetry was obtained starting from 7,8-dibromo[5]helicene by Yamamoto nickel(0) couplings. It afforded a chiral polyaromatic hydrocarbon (PAH) embedding six enantiomerically stable [5]helicene units. This dense accumulation of helical strain resulted in a distorted geometry, but stable stereochemistry. The conformational, structural, chiroptical, and photophysical properties of the molecule are reported

Determination of the absolute configuration of 1,3,5-triphenyl-4,5- dihydropyrazole enantiomers by a combination of VCD, ECD measurements, and theoretical calculations

The enantiomers of 1,3,5-triphenyl-4,5-dihydropyrazole (an intense blue fluorescent compound) have been separated for the first time and their absolute configuration was established by a combination of VCD and ECD measurements and theoretical calculations. The enantiomers of 1,3,5-triphenyl-4,5-dihydropyrazole which are highly fluorescent both in solution (CH2Cl2) and in the solid state may find application in the very active field of enantioselective fluorosensors. © 2011 Elsevier Ltd. All rights reserved.Peer Reviewe

Allosteric Guest Binding in Chiral Zirconium(IV) Double Decker Porphyrin Cages

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Absolute configuration and host-guest binding of chiral porphyrin-cages by a combined chiroptical and theoretical approach

International audiencePorphyrin cage-compounds are used as biomimetic models and substrate-selective catalysts in supramolecular chemistry. In this work we present the resolution of planar-chiral porphyrin cages and the determination of their absolute configuration by vibrational circular dichroism in combination with density functional theory calculations. The chiral porphyrin-cages form complexes with achiral and chiral viologen-guests and upon binding one of the axial enantiomorphs of the guest is bound selectively, as is indicated by induced-electronic-dichroism-spectra in combination with calculations. This host-guest binding also leads to unusual enhanced vibrational circular dichroism, which is the result of a combination of phenomena, such as rigidification of the host and guest structures, charge transfer, and coupling of specific vibration modes of the host and guest. The results offer insights in how the porphyrin cage-compounds may be used to construct a future molecular Turing machine that can write chiral information onto polymer chains