#  Oliver Trapp 

 



####  calendar\_today Date and Time 

 **October 8, 2014** 

 04:15PM - 05:15PM EDT 

####  pin\_drop Location 

 **Pfizer Lecture Hall**  



 

 



 

Professor Oliver Trapp, Organisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg. *Chirality: From Dynamic Catalytic Systems to Coulomb Explosion Imaging.* Special Seminar.Abstract: Stereolabile interconverting catalysts open up the possibility of directing enantioselectivity in asymmetric synthesis by formation of diastereomeric complexes with chiral auxiliaries and deracemization. However, the stoichiometrically used chiral auxilliaries can significantly limit the potential applications of such systems. We developed new strategies based on stereochemically labile ligands and designed catalytic systems, which are able to switch their configuration by interaction with suitable selectors. Novel tropos BIPHEP ligands containing achiral and chiral selectands in the backbone were synthesized. These chiral selectands form transient diastereomeric associates with chiral selectors and thus deracemize. The obtained enantiomerically enriched BiPHEP catalysts were successfully used in organocatalytic and metal mediated transformations. The presented strategy opens up new approaches for the development of improved self-amplified asymmetric syntheses.

The second part of this presentation will be devoted to the first assignment of the absolute configuration of enantiopure (*R*,*R*)-2,3-dideuterooxirane by direct visualization of the sense of chirality using foil-induced Coulomb explosion imaging (CEI). In this experiment a small sample of enantiopure trans-2,3-dideuterooxirane is ionized, accelerated by 2.0 MeV and mass-selected. The valence electrons are stripped off within 1 fs by passing through an ultrathin diamond foil leading to Coulomb repulsion of the positively charged atoms and enlargement of the initial structure. *Trans*-2,3-Dideuterooxirane was selected as target molecule for the Coulomb explosion imaging experiment, because it can be directly derived from glyceraldehyde. The unambiguous chemical correlation of the absolute configuration of cryptochiral (*R*,*R*)-2,3-dideuterooxirane with the stereochemical key reference (+)-glyceraldehyde finally puts the absolute configuration of (+)-glyceraldehyde on firm experimental grounds.



 

 



 

 

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