SELECTIVE SYNTHESES AND DERIVATISATION OF A2Bmeso-TRIARYLCORROLES
E.
aDept.
a
Dolusic ,
H.
b
Radecka ,
Corroles are porphyrin analogues, lacking one meso carbon. Until
recently they were rather rare chemicals, but in the last few years a
number of publications have appeared describing the synthesis of
corroles and core-modified corroles.1-3 This has made these interesting
compounds much more available than before, allowing the study of
their coordination chemistry, applications of metallocorroles in catalysis
and their photophysical behaviour.
In this work a two-step synthesis of sterically encumbered
triarylcorroles 2 by an acid catalysed [2+1] condensation of
dipyrromethanes 1 and aromatic aldehydes followed by oxidation with
p-chloranil is described. Preparation of bifunctional corrole-indole
reagents, which should serve to monitor binding of indolic compounds
to proteins in living plant cells, is in progress.
O
Ar
1
1
H
O
NH
H+
N
H
Ar2 / H+
NH HN
Ar2
Ar2
NH HN
Ar
1a
Ar
1
p-chloranil
NH HN
1a
NH
1
Ar
N
Ar1
H
N
HN
2
Synthesis of the corroles
The general procedure for the synthesis of the corroles was as
outlined in the scheme above. The aldehyde was subjected to an acid
catalysed reaction with an excess of 1 in CH2Cl2 to produce the
intermediate tetrapyrromethane 1a which was not isolated. Instead, the
entire reaction mixture was subjected to oxidation with p-chloranil to
yield the corrole 2.
Three methods were tried out within the scope of the procedure:
method A generally follows the procedure described by Asokan et al.1
With lowering the ratio of dipyrromethane and aldehyde the yields of
corrole decreased and some porphyrin (bearing two pentafluorophenyl
moieties) could be isolated.
Method B was essentially as described by Gryko and Jadach.2
We also carried out the reaction at 0ºC rather than at room
temperature, which should slow down the formation of the by-product
tris(2,6-dichlorophenyl) corrole, otherwise formed in a substantial
amount.
Better results were obtained by choosing method C, basically the
same as method B except for catalysing the reaction with trichloro(TCA) rather than trifluoroacetic acid, and this in a concentration as low
as about 1/75 that of the aldehyde.
The corroles, which in most cases were not prepared previously,
and possible by-products were isolated by careful column- or plate
chromatography in mixtures of CH2Cl2 and heptane and characterized
by 1H and 13C NMR spectroscopy, electrospray mass spectrometry and
UV spectroscopy. The details can be seen in the Table.
HN
Ratio
Reaction
c(ALD.)/
c(DPM)/c time and
mM
(ALD.)
temp.
Ar2
Method
2a
C6H3Cl2
C6F5
A
4.3
5/1
1h
r.t.
2a
C6H3Cl2
C6F5
A
3.5
6/1
30 min
r.t.
2b
C6H3Cl2
C6H4NO2
B
11.9
3/1
2h
0ºC
2b
C6H3Cl2
C6H4NO2
C
16.1
3/1
1 day
0ºC
B
11.8
3/1
2 days
r.t.
C
11.4
3/1
1 day
0ºC
O
C6H3Cl2
C6H4O(CH2)11SCCH3
O
2c
C6H3Cl2
2d
C6H3Cl2
C6H5COOMe
C
11.4
3/1
1 day
0ºC
2e
mesityl
C6H4NO2
C
11.6
3/1
1 day
0ºC
C
11.6
3/1
1 day
0ºC
OH
Ar
HN
NH
Ar1
2c
NH HN
Ar1
BelgiumN
Target
corrole
2f
1
1
NH
C6H4O(CH2)11SCCH3
Ar2
Ar
and W.
a
Dehaen
of Chemistry, University of Leuven, Celestijnenlaan 200F, B-3001 Leuven,
bInstitute of Animal Reproduction and Food Research of Polish Academy of Sciences,
Division of Food Science, Tuwima 10, 10-747 Olsztyn, Poland
e-mail : eduard.dolusic@chem.kuleuven.ac.be
Introduction
H
J.
b
Radecki
TYPE
1
C6H3Cl2
Acid,
conc./
mM
BF3.Et2O
1/3
c(ALD.)
BF3.Et2O
1/3
c(ALD.)
TFA
1/13
c(AL.)
TCA
1/77
c(AL.)
TFA
1/13
c(AL.)
TCA
1/63
c(AL.)
TCA
1/63
c(AL.)
TCA
1/73
c(AL.)
TCA
1/64
c(AL.)
Yield
22
11
10
16
13
10
20
18
<1
Application of the corroles
Samples of some of the corroles 2 were incorporated in
membranes or self-assembled monolayers. The modified
membranes show very significant response to small neutral phenol
analytes. The response towards these analytes is much higher than
for the porphyrin and calixpyrroles that were used previously in the
framework of our collaboration,4 since the basicity of the corroles is
much higher.
Alternatively, conjugates of 2c with derivatives 4 of plant
hormone (auxin) indole-3-acetic acid are currently being prepared
(according to the scheme below) in order to give rise to novel
probes 7 for indole-binding proteins in living cells. This work is
being done in collaboration with Prof. V. Magnus, Zagreb, Croatia.
COOH
H2N
Cl
4
NH HN
N
H
3
O
O
N
OC11H22 SCCH3
NH
O
+
Cl
N
N
Cl
Cl
Cl
Cl
O
2c
O
O
5
O
COOH
O
H
N
N
O
O
Cl
NH HN
OC11H22 SH
NH
N
H
6
Cl
3
COOH
O
OC11H22S
Cl
Cl
Cl
NH HN
NH
N
N
Cl
H
N
N
7
O
O
N
H
References
1. C. V. Asokan, S. Smeets, W. Dehaen, Tetrahedron Lett. 2001,
42, 4483-4485.
2. D. T. Gryko, K. Jadach, J. Org. Chem. 2001, 66, 4267-4275.
3. D. T. Gryko, Eur. J. Org. Chem. 2002, 1735-1743.
4. T. Piotrowski, H. Radecka, J. Radecki, S. Depraetere, W.
Dehaen, Mat. Sci. Eng. C 2001, 18, 223-228.