4th EucheMs chemistry congress

Poster Session 2
s1288
chem. Listy 106, s257–s1425 (2012)
Poster session 2 - organic chemistry
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StudieS in the iodinAtion of
3(5)-(2-hydroxyPhenyL)-5(3)-StyryL-1h-
-PyrAzoLeS
J. ferreirA 1 , v. SiLvA 1 , A. SiLvA 1 , J. CAvALeiro 1
1 University of Aveiro, Chemistry, Aveiro, Portugal
4-Iodopyrazoles are valuable starting materials in the
synthesis of important biologically active substances. They have
been used in transition-metal catalyzed cross-coupling reactions,
such as Heck, Stille, Suzuki, Sonogashira and Negishi couplings
and other important reactions. There are several methods reported
for the iodination of pyrazoles, but they present rather complicated
problems such as the use of large amounts of reactants and the
lack of regioselectivity giving mixtures of iodinated compounds.
So regioselective iodination of 4-pyrazolic position in order to
obtain 4-functionalized derivatives is an important issue.
Continuing our work on the search for biologically active
pyrazoles, now we report our findings concerning the reactivity
of 3(5)-(2-hydroxyphenyl)-5(3)-styryl-1H-pyrazole derivatives,
containing electron donor and electron withdrawing substituents
in the aromatic ring of the styryl group, in the oxidative iodination
using molecular iodine and ceric(IV) ammoniun nitrate (CAN) as
the in situ oxidant. We found that the reactivity of the C-4 position
in the iodination reaction is sensitive to the electronic properties
of its neighboring substituents. Electron donating groups promote
the monoiodination in the activated orto and para positions of the
2'-hydroxyphenyl group while electron withdrawing groups direct
the iodination to the 4-position of the pyrazole ring. The structural
elucidation of the obtained iodinated derivatives was
accomplished by 1D and 2D NMR spectroscopic studies.
Theoretical studies are underway to rationalize the
obtained iodination results of 3(5)-(2-hydroxyphenyl)-5(3)-styryl-
-1H-pyrazoles.
Keywords: Nitrogen Heterocycles; Halogenation; Iodine;
Substituents effects; NMR spectroscopy;
4 th EucheMs chemistry congress
P - 0 8 5 1
direCt PrePArAtion of
MononitroCALix[5]Arene uSinG [4+1]
CondenSAtion
K. fLidrovA 1 , P. LhotAK 1
1 Institute of Chemical Technology Prague, Department of
Organic Chemistry, Prague, Czech Republic
Calix[5]arene is known as an effective receptor for
fullerenes C and C . Despite its excelent complexation
60 70
behaviour,the utilization of calix[5]arene is limited by
complicated synthesis and derivatization. The direct synthesis of
calix[5]arene substituted in p-position significantly simplifies the
process of the preparation of fullerene receptors. The commonly
used methodology is a cyclization of linear dimer and trimer
[2+3]. We chose another approach and optimized the cyclization
of p-nitrosubstituted monomer and tetramer [1+4]. Surprisingly,
the mass spectroscopy revealed presence of not only
mononitrocalix[5]arene but also mononitrocalix[6]arene and
mononitrocalix[7]arene in appreciable yield.
We studied possibilities of the separation of these higher
calixarenes and the influence of reaction condition and template
effect on the relative abundance of these products.
Acknowledgement: This work is supported by the Czech
Science Foundation (203/09/0691). Financial support from
specific university research (MSMT No 21/2012).
Keywords: calixarene;
AUGUst 26–30, 2012, PrAGUE, cZEcH rEPUbLIc