4th EucheMs chemistry congress

Poster Session 1
s1047
chem. Listy 106, s587–s1425 (2012)
Poster session 1 - organic chemistry
P - 0 3 7 1
viSiBLe LiGht PhotoCAtALySiS – fLAvinS AS
CAtALyStS in orGAniC reACtionS
S. KueMMeL 1 , r. LeChner 1 , B. KoeniG 1
1 Institute of Organic Chemistry, Chemistry and Pharmacy,
Regensburg, Germany
Flavins are nature’s beloved redox co-factors. [1] When
irradiated by blue light, their ability to oxidize is dramatically
increased and thus they can be used in photocatalysis. [2] They are
easily accessible by synthesis and their properties can be tuned
by substitution pattern. [3]
Recently we reported different organic reactions with
vitamin B 2 derivatives as efficient photocatalysts. [4,5] The key step
of the photocatalytic cycle is the formation of the triplet state of
the flavin. [6] Based on the conclusions of these investigations we
are now able to present some improved derivatives of this catalyst
that yield higher triplet state populations due to heavy atom effect.
These new photocatalysts accelerate the oxidation reactions and
improve quantum yields.
Acknowledgement: Research supports: Deutsche
Bundesumweltstiftung (DBU), DFG: GRK 1626 – Chemical
Photocatalysis.
references:
1. V. Massey, Biochem. Soc. Trans. 2000, 28, 283-296.
2. a) B. J. Fritz, S. Kasai, K. Matsui, Photochem. Photobiol.
1987, 45, 113-117;
b) A. Bowd, P. Byrom, J. B. Hudson, J. H. Turnbull,
Photochem. Photobiol. 1968, 8, 1.
3. Chemistry and Biochemistry of Flavoenzymes;
F. Müller, Ed., CRC Boca Raton, Fl, 1991.
4. R. Lechner, B. König, Synthesis 2010, 10, 1712.
5. R. Lechner, S. Kümmel, B. König, Photochem. Photobiol.
Sci. 2010, 9, 1367-1377.
6. U. Megerle, M. Wenninger, R.-J. Kutta, R. Lechner,
B. König, B. Dick, E. Riedle, Phys. Chem. Chem. Phys.
2011, 13, 8869-8880.
Keywords: Photochemistry; Homogeneous Catalysis; Green
Chemistry;
4 th EucheMs chemistry congress
P - 0 3 7 2
orGAnoCAtALySiS of dynAMiC iMine Bond
exChAnGe
S. KuLChAt 1 , K. MeGueLLAti 1 , n. ALLendÖrfer 1 ,
J. M. Lehn 1
1 Institut de Science et d’Ingenierie Supramoleculaire,
Chemistry, Strasbourg, France
Oganocatalysis by primary and secondary amines via
enamine and iminium intermediates has been actively pursued in
recent years to facilitate carbonyl condensation reactions. [1]
Reversible covalent bond formation and exchange of imines are
fundamental reactions in organic chemistry. [2, 3] Recently, the
imine bond exchange has been given considerable attention with
the development of dynamic covalent chemistry. [2] In this study,
we describe the component exchange of imines using L-proline
as an organocatalyst to significantly accelerate the exchange
reaction, in some cases, up to a 10-fold rate increase.
references:
1. a) B. List, Chem. Rev. 2007, 107, 5413.
b) D.A. Bock, C.W. Lehnmann, B. List, Proc. Natl. Acad.
Sci. U.S.A. 2010, 107, 20636.
2. a) J.-M. Lehn, Chem. Eur. J. 1999, 5, 2455.
b) P.T. Corbett, J. Leclaire, L. Vial, K. R. West,
J.-L. Wietor, J.K.M. Sanders, and S. Otto, Chem. Rev.
2006, 106, 3652.
3. M.E. Belowich and J.F. Stoddart, Chem. Soc. Rev. 2012,
41, 2003.
Keywords: Combinatorial chemistry; Organocatalysis;
Supramolecular chemistry;
AUGUst 26–30, 2012, PrAGUE, cZEcH rEPUbLIc