4th EucheMs chemistry congress

Poster Session 1
s1041
chem. Listy 106, s587–s1425 (2012)
Poster session 1 - organic chemistry
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MoLeCuLAr SwitCheS for AfM
MeASureMentS
i. KÖhL 1 , P. of. dr. uLriCh LüninG 1
1 Christian-Albrechts-Universität zu Kiel, Otto-Diels-Institut für
Organische Chemie, Kiel, Germany
Azobenzenes are the prototype of switchable molecules. [1]
Therefore, the mechanical work of their photoisomerization shall
be determined quantitatively. Azobenzene derivatives shall be
attached covalently between a glass surface and a cantilever in an
atomic force microscope (AFM).
New azobiphenyl molecules to amplify the effective
distance change during the E,Z-isomerization will be presented.
This shall lead to a better signal-to-noise ratio due to increased
change of length. [2] The azobiphenyls are substituted with
methylgroups to improve solubility. All synthesis were done by
an oxidative copper(II)-catalyzed coupling reaction in
combination with a Suzuki reaction.
In solution, the switching behavior of azobenzenes and
azobiphenyles was examined by NMR and UV/Vis spectroscopy.
The amount of cis isomer was determined by NMR spectroscopy.
The reversibility of switching was investigated by
UV/Vis spectroscopy. All investigated molecules showed
E,Z-isomerization and sufficiently long half-life times.
references:
1. G. S. Hartley, Nature 1937, 140, 281.
2. C. Glockner, Dissertation 2011, CAU Kiel.
Keywords: Azo compounds; Photochemistry; Oxidation;
4 th EucheMs chemistry congress
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viSiBLe LiGht Photoredox CAtALySiS with
n-A-rAdiCALS AS interMediAteS
P. KohLS 1 , d. JAdhAv 2 , G. PAndey 2 , o. reiSer 1
1 Institute of Organic Chemistry, Chemie und Pharmazie,
Regensburg, Germany
2 Organic Chemistry, NCL, Pune, India
In recent years many discoveries were made in the field of
photochemistry mediated by visible light. Light is inexpensive
and readily available worldwide. It is not polluting the
environment and can transfer energy under mild reaction
conditions. Applying the concept of photoredox catalysis with
visible light, ruthenium(II) and iridium(III) complexes proved to
be versatile catalysts due to their good charge separation abilities
and redox properties. [1] The transition metal complex acts hereby
as an electron shuttle which transfers electrons from a donor to
an acceptor or vice versa.
Due to our progress in the field of photocatalytical
debromination reactions we started to investigate photocatalytical
conjugate addition reactions. [2] In the course of our studies, we
discovered that tert. amines can be oxidized by photoredox
catalysts to an amine located radical cation which rearranges to a
N-α-radical under loss of an proton. This radical than attacks an
enone system and forms the conjugate addition product
subsequently. [3] N-Phenyltetrahydroisoquinoline species proofed
to be the most suitable tert. amine. On the other hand, most enone
systems are applicable in this reaction and lead to the expected
conjugate addition products in moderate to good yields.
Our current studies focus on expanding the scope and
increasing the yield of the reaction. Especially the
functionalization of different tert. amines would be of interest due
to their regular appearance in natural products and pharmaceutical
drugs. We are also concentrated on the development of a selective
photocatalytic conjugate addition.
references:
1. a)Teplý, F. Collect. Czech.Chem. Commun.2011, 76, 859;
b) K. Zeitler, Angew. Chem. Int. Ed. 2009, 48, 9785–9789.
2. Maji, T.; Karmakar, A.; Reiser, O. J. Org. Chem.2011, 76,
736.
3. Kohls, P.; Jadhav, D.; Pandey, G.; Reiser, O. Org. Lett.
2012, 14, 672.
Keywords: photocatalysis; conjugate addition; photoredox
catalysis;
AUGUst 26–30, 2012, PrAGUE, cZEcH rEPUbLIc