4th EucheMs chemistry congress

Poster Session 2
s1356
chem. Listy 106, s257–s1425 (2012)
Poster session 2 - organic chemistry
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noveL heteroAreniuM CAtALyStS for
SuLfoxidAtionS
J. SturALA 1 , r. CiBuLKA 1
1 Institute of Chemical Technology Prague,
Department of Organic Chemistry, Prague, Czech Republic
Chemoselective introduction of oxygen into an organic
molecule represents one of the key transformations in organic
synthesis. Many organocatalysts are capable to introduce oxygen
(even stereoselectively) into an organic substrate, e.g. chiral
ketones and iminium salts. Among them, flavinium salts seem to
be the most promising mediators for sulfoxidations and
Baeyer-Villiger oxidations. [1] These catalysts are inspired by
natural enzymes, where flavin moiety is present in the active site.
In the catalysis of oxidations with hydrogen peroxide, flavinium
salts form flavin-hydroperoxide which is the oxidising agent for
the substrate. Oxidations of sulfides promoted by flavinium salts
are highly chemoselective – no overoxidation to sulfones occurs.
Use of chiral flavinium salt results in stereoselective oxidation. [2]
We have found that flavin moiety is not necessary
– pyrazinium salts [3] bearing electron-withdrawing substituents
form pyrazine-6-hydroperoxides and oxidise substrates in similar
manner as flavin catalysts. Major advantage of these salts is easy
availability.
This work is focused on heteroarenium salts based on
pyrimidine. Effect of both electron-withdrawing and
electron-donating groups in position 2- and 4- is examined to
determine influence of electronic effects on catalytic cycle. Also
effect of alkyl chain length and counteranion was studied to
optimize catalyst core for introduction of cyclodextrin moiety and
to make oxidations stereoselective.
Acknowledgement: This work was financially supported by
Ministry of Youth, Sports and Education of the Czech Republic
(specific university research no. A2_FCHT_2012_012) and the
Czech Science Foundation (Grant No. P207/12/0447).
references:
1. Gelalcha, F. G. Chem. Rev. 2007, 107, 3338-3361.
2. Mojr, V.; Budesinsky, M.; Cibulka, R.; Kraus, T. Org.
Biomol. Chem. 2011, 9, 7318-7326.
3. Ménová, P.; Kafka, F.; Dvoráková, H.; Gunnoo, S.; Šanda,
M.; Cibulka, R. Adv. Synth. Catal. 2011, 353, 865-870.
Keywords: organocatalysis; pyrimidine salts; sulfoxidation;
organic peroxides;
4 th EucheMs chemistry congress
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MoLeCuLAr SwitCh BASed on CuCurBituriL
J. SveC 1 , v. SindeLár 1
1 Masaryk University Fac Sci, Department of Chemistry, Brno,
Czech Republic
Macrocycles cucurbit[n]uriles (CBn) can create
supramolecular complexes with some positivly charced guest. We
used as a guest simple lutidine derivative with carboxyalkyl
group. We will demonstrated that the lutidine derivative forms
stable inclusion complexes with CB6 and CB7 at acidic water.
Under the complex formation CB6 engulfs aliphatic part of the
guest contrary to CB7 which bind lutidinium part. Affinity of
lutidinium toward CB6 is weaker compared to CB7 also the
exchange of the guest molecule within the macrocycle take place
significantly slower in the former case. Under basic condition the
lutidinium•CB6 complex dissociates while the formation of
lutidinium•CB7 also with smaller value of association constant.
Acknowledgements: Support for this work was provided by the
project CETOCOEN (no. CZ.1.05/2.1.00/01.0001) from the
European Regional Development Fund (V.S.) and
AMVIS/KONTAKT II (LH11012; V.S.).
Keywords: Receptors; Macrocycles;
AUGUst 26–30, 2012, PrAGUE, cZEcH rEPUbLIc