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Nina Hermanns

Publications and source records attributed to Nina Hermanns.

7 recordsLinked to original sources
PubMed2006

Efficient and selective sulfoxidation by hydrogen peroxide, using a recyclable flavin--[BMIm]PF6 catalytic system.

A new flavin catalyst 2 immobilized in an ionic liquid ([BMIm]PF6) was used for the highly selective oxidation of sulfides to sulfoxides by hydrogen peroxide. The sulfoxides were obtained in good to high yields and high selectivity without any detectable overoxidation to sulfone. The catalyst in the ionic liquid was recycled up to seven times without loss of activity or selectivity.

Catalysis↗
PubMed2004

Preparation and redox properties of N,N,N-1,3,5-trialkylated flavin derivatives and their activity as redox catalysts.

Eight different flavin derivatives have been synthesized and the electronic effects of substituents in various positions on the flavin redox chemistry were investigated. The redox potentials of the flavins, determined by cyclic voltammetry, correlated with their efficiency as catalysts in the H2O2 oxidation of methyl p-tolyl sulfide. Introduction of electron-withdrawing groups increased the stability of the reduced catalyst precursor.

Alkylation↗
PubMed2004

The MPEG effect: improving asymmetric processes by simple additives.

Small amounts of simple methoxy poly(ethylene glycol)s (MPEGs) have a beneficial effect on catalyzed asymmetric aryl and alkyl transfer reactions onto aldehydes. The enantiomeric excesses of the products are improved, and this "MPEG effect" allows a reduction of the catalyst loading by a factor of 10.

Journal Article↗
PubMed2002

Polymer-supported ferrocenyl oxazolines for the catalyzed highly enantioselective phenyl transfer to aldehydes.

A new chiral MeO-PEG-supported ferrocenyl oxazoline was synthesized and successfully employed in the enantioselective phenyl transfer to aldehydes. The products were obtained in high yields and with excellent enantioselectivities (up to 97% ee). Furthermore, the recovery of the ferrocene was facile, and catalyst efficiency was maintained in subsequent reactions.

Benzaldehydes↗
PubMed2001

Catalyzed Asymmetric Arylation Reactions.

Addition and substitution reactions with carbon nucleophiles are fundamental processes in organic synthesis, and the development of general catalytic asymmetric variants thereof is still a major challenge today. In contrast to enantioselective alkyl transfer reactions, the corresponding arylations have not yet reached a high level of maturity. The existing protocols are either of no general applicability or are limited in terms of selectivity. This article summarizes established routes for catalytic asymmetric aryl transfer together with the latest developments in this area. The scope and limitations of this reaction are discussed.

Journal Article↗
PubMed2001

Application of a Planar Chiral eta(5)-Cyclopentadienylrhenium(I)tricarbonyl Complex in Asymmetric Catalysis: Highly Enantioselective Phenyl Transfer to Aldehydes We are grateful to the Deutsche Forschungsgemeinschaft (DFG) within the Collaborative Research Center (SFB) 380 "Asymmetric Synthesis by Chemical and Biological Methods" and the Fonds der Chemischen Industrie for financial support and to Dr. C. W. Lehmann, MPI für Kohlenforschung, Mülheim, for collecting the X-ray diffraction data. M.K. acknowledges the DFG for a predoctoral fellowship (Graduiertenkolleg). We thank Degussa and Witco for donations of chemicals and Professor Dr. A. Salzer as well as Dipl.-Ing. M. Treu for inspiring discussions. We also appreciate the stimulus of Dr. K. Muñiz for the investigation of the influence of the metal-pi-fragment on catalyses of this type.

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Journal Article↗