Thiaporphyrins with One, Two and Four Unsubstituted meso-Carbons
SHORT COMMUNICATION
Scheme 4. Synthetic scheme for porphyrin 14
organolithium reagents, as developed by Senge et al.[3] Re-
action of 6 with n-butyllithium at 0 °C in THF followed by
oxidation with DDQ at room temperature afforded the bu-
tyl derivative 14 in 65% yield (Scheme 4).
Scheme 3. Synthetic scheme for 11, 12 and 13
In conclusion, we have prepared meso-unsubstituted thia-
porphyrins with one, two and four meso-unsubstituted car-
bons using simple thiophene diols. Previously no one has
explored the synthesis of meso-unsubstituted thiaporphyr-
ins in detail which has several applications in porphyrin
synthetic chemistry. We demonstrated the reactivity of
meso-unsubstituted thiaporphyrins by carrying out the re-
cently reported reactions and synthesized some important
functionalized meso-thiaporphyrins. These functionalized
porphyrins can be used to construct some complicated thia-
porphyrin systems with novel physical and chemical proper-
ties and such efforts are presently underway in our labora-
tory.
CH Cl as eluent to give dibromo derivative 11 in 55%
2
2
yield (Scheme 3).
The ethyne derivative 12 was prepared[11] in 58% yield
by treating porphyrin 11 with trimethylsilylacetylene in the
presence of a catalytic amount of [PdCl (PPh ) ]/CuI in
2
3 2
THF/triethylamine followed by deprotection of the trimeth-
ylsilyl group with K CO in THF/CH OH. The bromo and
2
3
3
ethyne functional groups are very useful to synthesize mul-
[
12]
tiporphyrin arrays.
prepared by following the method of Arnold et al.
phyrin 11 was treated with two equivalents of Pd (dba) /
meso-Bis(palladio)porphyrin 13 was
[
13]
Por-
2
3
PPh in toluene at room temperature and the crude com-
3
Supporting Information Available (see also footnote on
the first page of this article): Mass spectra, NMR spectra,
X-ray crystal structures and absorption data of selected
compounds and tables of crystal data.
pound was purified by column chromatography to afford
the palladioporphyrin 13 in 28% yield. The introduction of
substituents at the meso carbons resulted in large red shifts
of the absorption (Figure 2) and fluorescence bands and
maximum shifts were observed for porphyrins 12 and 13
indicating that the electronic properties of the meso-unsub- Acknowledgments
stituted porphyrins are altered drastically by introducing
substituents at the meso carbons (see Supporting Infor-
mation).
MR thanks DAE and DST for funding the project. We also thank
Dr. Ajay Kumar Sah for helpful discussions.
We also tested the reactivity of meso-unsubstituted thia-
porphyrins by reacting meso-unsubstituted porphyrins with
[
[
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Figure 2. Absorption spectra, recorded in toluene for 5 (Ϫ), 11
(---) and 12 (-·-·-).
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www.eurjoc.org
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