ISMSC 2007 - Università degli Studi di Pavia

Application of a new classes podands in solid-liquid phase transfer
catalysis
Bogusawa ska, Radosaw Pankiewicz and Grzegorz Schroeder
Faculty of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Pozna, Poland
Phase transfer catalysis (PTC) is now a well established method in organic synthesis
applicable to reactions of inorganic and organic anions and other active species with organic
compounds. Phase transfer catalysis is a general technique widely used in organic chemistry,
which usually, but not always, based on the reactions involving transfer of anion from an
aqueous or solid phase into an organic phase followed by the reaction of anion with the
substrate in organic phase. Reacting anions are continuously introduced into non-polar organic
phase as ion pairs with complexed cations supplied by the catalyst. Further reactions of these
ion pairs proceed in the organic phase. Nowadays the term “phase transfer catalysis” refers to
several effective techniques whose typical advantages are simplicity, mild conditions, high
reaction rates and rather inexpensive reagents. It is also one of the most versatile preparative
methods. The search for new catalysts, their use in PTC asymmetric synthesis and the attempts
to understand their mechanistic role are exciting topics of investigation.
In this presentation we report a systematic study of boron polypodands 1-4 and podands
2-8 synthesized on the base of Triton-X with B, Si and P as central atoms in the molecule,
obtained in high yield by the reaction presented in Scheme 1. We used podands as catalysts in
some phase transfer catalysis processes and they have been found excellent catalysts in some
anion promoted reactions (nucleophilic substitution, reduction, alkylation, ect.) under solid-liquid
conditions in chlorobenzene as low polarity medium and acetonitrile as polar aprotic solvent. A
comparison is planned with the well known PTC catalysts: crown ethers DCH18C6 (9),
PEG400Me2 (10) and Si-podand (11), studied previously by us [1, 2].
B-podands
O
O
B
O
Triton’s podands
O CH3 2
O CH3 2
O CH3 2
O
O
B
O
O CH3 7
O CH3 7
O CH3 7
O
O
B
1 2 3 4
Tr =
n = 10
Tr
Tr
Tr
O
O
O
O
nO
Si
nO
O
n
O CH3 12
O CH3 12
O CH3 12
O
O
Si
O
O
O
B
O
O
B
O
O Tr
n
O Tr
n
O Tr
n
O
O
P
O
O Tr
n
O Tr
n
O Tr
n
O
O
Si
O
O Tr
n
O Tr
n
O Tr
n
5 6 7
O
O Tr
n
O Tr
n
O Tr
n
O CH3 16
[1] A. Maia, D. Landini, B. ska and, G. Schroeder, Tetrahedron, 2004, 60, 10111-10115.
[2] B. ska, R. Pankiewicz, G. Schroeder, A. Maia, Tetrahedron Lett., 2006, 47, 5673-5676.
8
O
O
CH 3
16
CH3 16
PSA 91
New DOTP analogue for possible medical applications
Luís M. P. Lima a , Rita Delgado a,b , Petr Hermann c , Jan Kotek c
a Instituto de Tecnologia Química e Biológica, UNL, Oeiras, Portugal
b Instituto Superior Técnico, UTL, Lisboa, Portugal
c Department of Inorganic Chemistry, Charles University, Prague, Czech Republic
Cyclen derivatives with coordinating pendant arms are suitable ligands for transition metal and
lanthanide ions. In particular, lanthanide (III) complexes of ligands such as DOTA, DOTP and
others have found important applications in the field of medicinal chemistry, namely as contrast
agents for Magnetic Resonance Imaging and as radiopharmaceuticals for diagnosis or therapy.
However, available data from the studies of such ligands are frequently obtained in different
experimental conditions, which makes it difficult to compare the properties of different ligands.
To overcome that problem we have recently studied the solution behaviour of a series of
macrocycles functionalized with acetic and methylphosphonic acid pendant arms [1].
The synthesis of macrocycles bearing mixed pendant arms is an important tool for developing
ligands with improved chemical and biological properties or suitable for use as bifunctional
chelators. During recent years we have focused on the synthesis and study of such macrocyclic
derivatives [2].
(HO)2OP
(HO)2OP
N N
N N
R
PO(OH)2
PSA 92
A new ligand analogue of DOTP was synthesized by
introducing one pendant arm of a different type on the
DOTP structure. The protonation sites of the ligand
were studied by 31 P NMR titration. Protonation
constants of the ligand as well as thermodynamic
stability constants for some transition metal and
lanthanide complexes were determined by
potentiometric titrations. This ligand shows a very high
overall basicity, and its metal complexes present also a very high stability. The discussed
properties are compared with those published for DOTP and other similar ligands.
[1] R. Delgado, J. Costa, K. P. Guerra, and L. M. P. Lima, Pure Appl. Chem., 2005, 77, 569-
579.
[2] V. Kubiek, J. Rudovský, J. Kotek, P. Hermann, L. Vander Elst, R. N. Muller, Z. I. Kolar, H.
Th. Wolterbeek, J. A. Peters, and I. Lukeš, J. Am. Chem. Soc., 2005, 127, 16477-16485.