4th EucheMs chemistry congress

Poster Session 1
s1031
chem. Listy 106, s587–s1425 (2012)
Poster session 1 - organic chemistry
P - 0 3 3 9
hiGhLy fLuoreSCent PentACyCLiC
frAMeworK throuGh A CASCAde ProCeSS
z. e. A. ChAMAS 1 , v. MAMAne 1 , y. fort 1
1 Universite De Lorraine, Organic Chemistry, Vandoeuvre les
Nancy, France
This presentation describes the synthesis of a new family of
pentacyclic chromophore whose fluorescence properties can be
modulated according to the functional groups present in the
molecule. These chromophores were obtained through
a cascade reaction between 2-formylbenzene boronic acid and
2,5-dihalopyridines. The cascade process was initiated by a
palladium-catalyzed cross-coupling reaction and was followed by
two successive nucleophilic cyclizations; the first cyclization
performed on the pyridine nitrogen and the second occurred
regioselectively on the adjacent carbon atom. This new cascade
reaction allowed the formation of a pentacycle as a single
regioisomer with four new bonds and two contiguous
stereocenters with trans relationships. In addition, preliminary
studies have shown that these polycyclic compounds have
excellent fluorescence properties that should enable us to extend
the scope of these new chromophores to the medical field and
molecular electronics.
Keywords: Chromophores; Diastereoselectivity; Fluorescence;
Nitrogen heterocycles; Fused-ring systems;
P - 0 3 4 0
heteroGeneouS PhotoCAtALySiS in orGAniC
SyntheSiS.
M. CherevAtSKAyA 1 , M. neuMAnn 1 , S. fueLdner 1 ,
C. hArLAnder 1 , S. KueMMeL 1 , S. dAnKeSreiter 2 ,
A. Pfitzner 2 , K. zeitLer 1 , B. KoeniG 1
1 University of Regensburg, Organic Chemistry, Regensburg,
Germany
2 University of Regensburg, Inorganic Chemistry, Regensburg,
Germany
Visible light photocatalysis is a topic of increasing interest
for many applications. One way of utilizing the visible range of
the solar spectra is the combination of organo- an photoredox
catalysis as pioneered by MacMillan [1a] . Using MacMillan’s
catalyst in conjunction with inorganic semiconductors as
sensitizers, we have investigated the asymmetric C-C coupling of
octanal with different bromo-substrates [1] .
The range of investigated semiconductors includes the
well-known blank TiO (P25), dye-sensitized TiO (1) as well as
2 2
novel PbBiO Br semiconductors. The PbBiO Br semiconductor
2 2
was used in two modifications – nanoparticles and bulk material,
which have band gaps of 2.56 eV and 2.47 eV, respectively and
can be irradiated with 440 nm LEDs. TiO was sensitized by the
2
Phos-Texas Red dye, which was immobilized on the surface and
showed an absorption maximum at 560 nm.
The products could be obtained in good to very good yields
of up to 84 % (PbBiO Br nano/2-bromodiethylmalonate) and
2
with excellent enantioselectivities of up to 96% (PbBiO Br 2
nano/bromoacetophenon) [2] .
Other C-C bond formation reactions are under investigations
in our group.
Acknowledgement: Financial support: DFG:
GRK 1626 – Chemical Photocatalysis.
4 th EucheMs chemistry congress
references:
1. a) D. A. Nicewicz; D. W. C. MacMillan, Science 2008,
322, 77;
b) H. Shih, M. N. Vander Wal, R. L. Grange,
D. W. C. MacMillan, J. Am. Chem. Soc. 2010, 132, 13600;
2. M. Cherevatskaya, M. Neumann, S. Fueldner, C. Harlander,
S. Kuemmel, S. Dankesreiter, A. Pfitzner, K. Zeitler,
B. Koenig, Angew. Chemie Int. Ed., 2012, in press.
Keywords: heterogeneous photocatalysis; visible-light
photocatalysis;
AUGUst 26–30, 2012, PrAGUE, cZEcH rEPUbLIc