4th EucheMs chemistry congress

Poster Session 2
s1285
chem. Listy 106, s257–s1425 (2012)
Poster session 2 - organic chemistry
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SyntheSiS of SuBStituted BiPyridineS And
terPyridineS By PALLAdiuM-CAtALyzed
direCt C-h AryLAtion of Pyridine n-oxideS
And BiPyridine n-oxideS
S. duriC 1 , f. d. SyPASeuth 1 , S. hoof 1 ,
C. C. tzSChuCKe 1
1 Freie Universität Berlin, Institut für Chemie und Biochemie
– Organische Chemie, Berlin, Germany
Bipyridines and terpyridines constitute an important class
of heterocycles and numerous synthetic approaches have been
described. [1] Cross coupling and ring assembly reactions are the
most widely used. However, these synthetic routes make use of
pyridyl organometallics and assembly precursor, which are
frequently unstable and require multistep preparation procedures.
Catalytic C-H-activation allows direct C-C-coupling and reduces
the number of synthetic steps significantly. [2] In this context, we
present a new versatile synthesis of functionalized bipyridines and
terpyridines based on palladium-catalyzed C-H-functionalization
of pyridine N-oxides. [3] Several examples of asymmetrically
substituted 2,2'-, 2,3'- and 2,4'-bipyridine N-oxides, containing
alkyl, methoxy, ester, nitrile, nitro, fluorine, and trifluoromethyl
substituents, have been successfully synthesized. The
2,2'-bipyridine N-oxides have been further used for the
preparation of 2,2';6',2''-terpyridine N-oxides, with asymmetric
substitution patterns that are not easily accessible by other
methodologies. The final deoxygenation of the N-oxides to the
coressponding bipyridine or terpyridine is accomplished in high
yield by either catalytic hydrogenation or reduction with PCl . 3
references:
1. Hapke, M.; Brandt, L.; Lützen, A., Chem. Soc. Rev. 2008,
37, 2782.
Newkome, G. R.; Patri, A. K.; Holder, E.; Schubert, U. S.,
Eur. J. Org. Chem. 2004, 235.
Heller, M.; Schubert, U. S., Eur. J. Org. Chem. 2003, 947.
2. Alberico, D.; Scott, M. E.; Lautens, M., Chem. Rev. 2007,
107, 174.
3. Duric, S.; Tzschucke, C. C., Org. Lett. 2011, 13, 2310.
Campeau, L. C.; Rousseaux, S.; Fagnou, K., J. Am. Chem.
Soc. 2005, 127, 18020.
Keywords: C-H activation; Palladium; Heterocycles; C-C
coupling;
4 th EucheMs chemistry congress
P - 0 8 4 5
PotASSiuM
(trifLuoroMethyL)triMethoxyBorAte – A
SheLf-StABLe trifLuoroMethyLAtinG
reAGent
w. dziK 1 , t. KnAuBer 1 , A. BuBA 1 , B. KhAn 1 ,
L. GooSSen 1
1 Technische Universität, Fachbereich Chemie – Organische
Chemie, Kaiserslautern, Germany
The introduction of a CF group has a profound effect on the
3
chemical and physical properties of a molecule. This is highly
beneficial in many functional molecules spanning from
pharmaceuticals or agrochemicals to high performance polymeric
materials.Traditional methods for trifluoromethylations operate
at harsh reaction conditions and use corrosive reagents like HF,
SbF or SF . Therefore, substantial research has been devoted to
5 4
the development of milder reagents suitable for a selective
late-stage trifluoromethylation of functionalized molecules. Stateof-the-art
trifluoromethylation reactions use trifluoromethyl
silanes, which are rather difficult to handle due to their volatility
and moisture-sensitivity, as the sources of a CF nucleophiles.
3
Here, we introduce potassium (trifluoromethyl)trimethoxyborate
as a new source of CF nucleophiles for trifluoromethylation
3
reactions. The crystalline salt is stable on storage, easy to handle,
and can be obtained in near-quantitative yields simply by mixing
B(OMe) , CF SiMe , and KF. This reagent is suitable for
3 3 3
trifluoromethylating both aryl electrophiles and nucleophiles
under oxidative conditions. The scope of possible transformations
includes the copper-catalyzed synthesis of trifluoromethyl
(hetero)arenes from aryl iodides or boronates, and metal-free
synthesis of trifluoromethyl alcohols from carbonyl compounds.
Alkoxy, ester, amide, alkylamine, nitro, cyano and bromo
substituents are tolerated and the reaction proceeds under very
mild conditions.
This new reagent is an attractive alternative, to
trifluoromethyl silanes and allows a smooth conversion of a
variety of compounds into their trifluoromethyl derivatives.
Keywords: Borates; C-C coupling; Arenes; Homogeneous
catalysis; Fluorine;
AUGUst 26–30, 2012, PrAGUE, cZEcH rEPUbLIc