Meso-pyrimidinyl-substituted A2B- and A3-corroles

Article abstract of DOI:10.1021/jo902709c

Chemical Equation Presented A variety of meso-pyrimidinyl- substituted. A₂B- and A₃- corroles (A = 4, 6-dichloropyrimidin-5-yl) have been syn-thesized by careful optimization of the macrocyclization conditions. meso-Pyrimidinylcorroles offer the distinct ad-vantage of an unprecedented broad scope of functionaliza-tion options. Highly sterically encumbered, triarylcorroles were readily prepared via efficient, nucleophilic aromatic substitution and Suzuki cross-coupling procedures.

Full text of DOI:10.1021/jo902709c

pubs.acs.org/joc
made in the field over the past decade.2 meso-Triarylcorroles
meso-Pyrimidinyl-Substituted A2B- and A3-Corroles
show an improved stability over the previously studied β-alky-
lated (partially) meso-free analogues, and they have been
prepared from a variety of aromatic aldehyde and aryldipyrro-
methane building blocks in acceptable to good yields by diffe-
rent cyclocondensation pathways.2 As the knowledge, interest,
and activity in the corrole field are steadily growing, the
pressure on synthetic (porphyrinoid) chemists to create increas-
ingly complex corrole derivatives with peculiar properties rises
accordingly. So far, modification of the corrole framework,
apart from the introduction of specific moieties on the corrole
building blocks, has mostly been achieved by (regioselective)
functionalization of the β-pyrrolic positions.2,3 Postmacrocy-
clization elaboration via the meso-positions has only been
reported in a few cases.4 Double picket fence corroles are par-
ticularly attractive considering the success of the analogous
porphyrins, e.g., as second-generation oxidation catalysts.4
To date, functionalization of corroles has mostly been
performed on the metalated rather than the free-base (Fb)
macrocycles, since they are considerably more robust. Me-
tallocorroles have, however, demonstrated peculiar reactivi-
ties, and liberation of the Fb congener from a metallocorrole
is often not trivial.2 Recent achievements in the demetalation
of certain metallocorroles (Ag, Mn, and especially Cu) now
enable application of a metalation-demetalation protocol
as a protective strategy toward functionalized Fb corroles.5
In continuation of our studies on pyrimidinylporphyri-
noids,6 we have previously explored the synthetic chemistry
of meso-pyrimidinyl-substituted AB2-corroles (A = 4,6-di-
chloropyrimidin-5-yl).7,8 These pyrimidinylcorroles were
proven to be versatile scaffolds for the construction of
sophisticated functional corroles, since smooth functionali-
zation on the 4,6-dichloropyrimidinyl meso-moieties via
nucleophilic aromatic substitution (SNAr) and Pd-catalyzed
cross-coupling reactions (Suzuki, Stille, Liebeskind-Srogl)
Thien H. Ngo,† Francesco Nastasi,‡ Fausto Puntoriero,‡
Sebastiano Campagna,‡ Wim Dehaen,*,† and
Wouter Maes†,§
†Molecular Design and Synthesis, Department of Chemistry,
Katholieke Universiteit Leuven, Celestijnenlaan 200F, B-3001
Leuven, Belgium, ‡Dipartimento di Chimica Inorganica,
Chimica Analitica e Chimica Fisica, Universitaꢀ di Messina,
98166 Vill. S. Agata, Messina, Italy, and §Institute for
Materials Research (IMO), Research Group Organic and
(Bio)Polymeric Chemistry, Hasselt University, Universitaire
Campus, Agoralaan Building D, B-3590 Diepenbeek, Belgium
wim.dehaen@chem.kuleuven.be
Received January 21, 2010
A variety of meso-pyrimidinyl-substituted A2B- and A3-
corroles (A = 4,6-dichloropyrimidin-5-yl) have been syn-
thesized by careful optimization of the macrocyclization
conditions. meso-Pyrimidinylcorroles offer the distinct ad-
vantage of an unprecedented broad scope of functionaliza-
tion options. Highly sterically encumbered triarylcorroles
were readily prepared via efficient nucleophilic aromatic
substitution and Suzuki cross-coupling procedures.
(3) (a) Vale, L. S. H. P.; Barata, J. F. B.; Santos, C. I. M.; Neves, M. G. P.
ꢁ
M. S.; Faustino, M. A. F.; Tome, A. C.; Silva, A. M. S.; Paz, F. A. A.;
Cavaleiro, J. A. S. J. Porphyrins Phthalocyanines 2009, 13, 358. (b) Barata,
ꢁ
J. F. B.; Neves, M. G. P. M. S.; Tome, A. C.; Cavaleiro, J. A. S. J. Porphyrins
Phthalocyanines 2009, 13, 415.
(4) (a) Rose, E.; Andrioletti, B. J. Chem. Soc., Perkin. Trans. 1 2002, 715.
ꢁ
(b) Collman, J. P.; Decreau, R. A. Org. Lett. 2005, 7, 975. (c) Broring, M.;
Milsmann, C.; Ruck, S.; Kohler, S. J. Organomet. Chem. 2009, 694, 1011. (d)
€
Broring, M.; Funk, M.; Milsmann, C. J. Porphyrins Phthalocyanines 2009,
13, 107.
€
Due to their distinctive properties and envisaged advantages
for particular applications, corroles are widely studied nowa-
days, in the sense that they are currently even challenging por-
phyrins as the “crown jewels” within the porphyrinoid family.
Studies on these contracted porphyrin macrocycles have fo-
cused on their coordination chemistry, electrochemistry, and
applicability in sensors, catalysis, medicine, and molecular
electronics.1 The recent success of corrole chemistry is in great
part due to the impressive synthetic progress that has been
€
€
(5) (a) Broring, M.; Hell, C. Chem. Commun. 2001, 2336. (b) Bruckner, C.;
Barta, C. A.; Brinas, R. P.; Krause Bauer, J. A. Inorg. Chem. 2003, 42, 1673.
€
~
(c) Mandoj, F.; Nardis, S.; Pomarico, G.; Paolesse, R. J. Porphyrins
Phthalocyanines 2008, 12, 19. (d) Liu, H. Y.; Chen, L.; Yam, F.; Zhan, H.
Y.; Ying, X.; Wang, X. L.; Jiang, H. F.; Chang, C. K. Chin. Chem. Lett. 2008,
19, 1000. (e) Capar, C.; Thomas, K. E.; Ghosh, A. J. Porphyrins Phthalo-
cyanines 2008, 12, 964. (f) Ngo, T. H.; Van Rossom, W.; Dehaen, W.; Maes,
W. Org. Biomol. Chem. 2009, 7, 439. (g) Stefanelli, M.; Shen, J.; Zhu, W.;
Mastroianni, M.; Mandoj, F.; Nardis, S.; Ou, Z.; Kadish, K. M.; Fronczek,
F. R.; Smith, K. M.; Paolesse, R. Inorg. Chem. 2009, 48, 6879.
(6) (a) Smeets, S.; Asokan, C. V.; Motmans, F.; Dehaen, W. J. Org. Chem.
2000, 65, 5882. (b) Maes, W.; Dehaen, W. Synlett 2003, 79. (c) Maes, W.;
Vanderhaeghen, J.; Dehaen, W. Chem. Commun. 2005, 2612. (d) Maes, W.;
Vanderhaeghen, J.; Smeets, S.; Asokan, C. V.; Van Renterghem, L. M.; Du
Prez, F. E.; Smet, M.; Dehaen, W. J. Org. Chem. 2006, 71, 2987. (e) Maes, W.;
Dehaen, W. Pol. J. Chem. 2008, 82, 1145.
ꢀ
(1) (a) Barbe, J.-M.; Canard, G.; Brandes, S.; Guilard, R. Chem.;Eur. J.
2007, 13, 2118. (b) Aviv, I.; Gross, Z. Chem. Commun. 2007, 1987. (c)
Flamigni, L.; Gryko, D. T. Chem. Soc. Rev. 2009, 38, 1635. (d) Aviv-Harel,
I.; Gross, Z. Chem.;Eur. J. 2009, 15, 8382.
(2) Reviews on (synthetic) corrole chemistry: (a) Gryko, D. T. Eur. J.
Org. Chem. 2002, 1735. (b) Gryko, D. T.; Fox, J. P.; Goldberg, P. J.
Porphyrins Phthalocyanines 2004, 8, 1091. (c) Ghosh, A. Angew. Chem.,
Int. Ed. 2004, 43, 1918. (d) Nardis, S.; Monti, D.; Paolesse, R. Mini-Rev. Org.
Chem. 2005, 2, 355. (e) Paolesse, R. Synlett 2008, 2215. (f) Gryko, D. T.
J. Porphyrins Phthalocyanines 2008, 12, 906.
(7) Maes, W.; Ngo, T. H.; Vanderhaeghen, J.; Dehaen, W. Org. Lett.
2007, 9, 3165.
(8) These corroles have previously been denominated as A2B-pyrimidi-
nylcorroles (B = 4,6-dichloropyrimidin-5-yl) (ref 7).
DOI: 10.1021/jo902709c
r
Published on Web 02/24/2010
J. Org. Chem. 2010, 75, 2127–2130 2127
2010 American Chemical Society

Ngo et al.
SCHEME 2. Synthesis of A2B-Pyrimidinylcorroles 4a-e
JOCNote
SCHEME 1. Synthesis of 5-Pyrimidinyldipyrromethanes 2a,b
afforded a variety of AB2-corrole derivatives. Our pyrimidi-
nylcorrole research has now been extended to A2B- and A3-
corroles. The extra meso-dichloropyrimidinyl units enable
the introduction of additional functional groups, resulting in
greater structural complexity and higher sterical encum-
brance.
A2B-Pyrimidinylcorroles. To prepare A2B-corroles with
two meso-dichloropyrimidinyl substituents, 5-pyrimidinyldi-
pyrromethanes are required as precursors. We have recently
reported the synthesis of aryldipyrromethanes in water as an
attractive procedure avoiding large quantities of pyrrole.9 Start-
ing from 4,6-dichloropyrimidine-5-carbaldehydes 1a,b, 5-pyr-
imidinyldipyrromethanes 2a,b were obtained in high yields
(75% and 95%, respectively) on applying optimized conditions
(Scheme 1).10 The methylthio group might enable insertion of
other moieties on a later stage.7 The main problem associated
with the synthesis of dipyrromethanes (DPMs) in water is the
aggregation tendency of the DPM precipitate, enclosing pyrrole
and unreacted aldehyde. Depending on the aldehyde used, the
precipitate may be too sticky for efficient stirring of the reaction
mixture. A fine precipitate could be obtained through sonication
or, alternatively, via slow addition of the pyrimidinecarbalde-
hyde to the acidic H2O/pyrrole mixture.10
The synthesis of A2B-pyrimidinylcorroles was initially
performed starting from DPM 2b and an electron-poor
aromatic aldehyde, either 4-nitro- or 4-cyanobenzaldehyde.
These aldehyde precursors were chosen to maximize the
electron-deficient nature of the final A2B-corrole, ensuring
good structural stability. As a starting point, the conditions
as carefully optimized for AB2-pyrimidinylcorroles were
chosen. The maximum AB2-corrole yield (35%; precursors
mesityl-DPM and 1a) was obtained on condensation of the
building blocks in a 1:1 ratio, catalyzed by a small amount of
borontrifluoride dietherate catalyst (0.043 equiv).7 Applica-
tion of these conditions to the macrocyclization of DPM 2b
and 4-nitrobenzaldehyde (3a), in a stoichiometric 2:1 ratio,
afforded only trace amounts of the desired A2B-corrole 4a
(after oxidation with p-chloranil), even after 24 h (the reac-
tion progress being monitored by ESI-MS) (Table S1 in the
Supporting Information, Scheme 2).10 Even upon variation
of the catalyst content, the corrole yield did not rise above
3% (Table S1, Supporting Information). Starting from 4-
cyanobenzaldehyde (3b), the yield could be enhanced to a
still modest 10% A2B-corrole 4b through optimization of the
main products. A larger excess of DPM might avoid inser-
tion of the second aldehyde moiety and favor the formation
of the [2 þ 1] tetrapyrrane intermediate. Rather than adding
DPM 2b in significantly larger amounts, the excess was
created in situ by slow addition of the aldehyde, activated
with BF3 OEt2 (0.043 equiv), to a dilute solution of 2b (3
3
equiv) in dichloromethane over several hours. When this
procedure was applied to 4-cyanobenzaldehyde, A2B-cor-
role 4b was isolated in a substantially improved 28% yield.
Likewise, A2B-corroles 4a,c-e were synthesized in fair yields
(9-24%) from aldehyde precursors with either electron-
donating or -withdrawing substituents (Scheme 2). The
optimum reaction and oxidation time were slightly different
depending on the aromatic aldehyde used. In a similar way,
A2B-corrole 4f was synthesized starting from DPM 2a and
benzaldehyde (14% yield).
While performing functionalization reactions on the AB2-
pyrimidinylcorroles, it was observed that the Fb derivatives
are not really suitable for elaboration of the substitution
pattern. Modest yields were obtained in both SNAr and
Suzuki cross-coupling reactions.7 The same reactions did,
however, provide high yields when performed on the corre-
sponding Cu-corroles. Functionalized Fb corroles were
more efficiently prepared by reductive demetalation of the
Cu-corrole derivatives, rather than through direct modifica-
tion on the metal-free AB2-corroles.5f,7 Prior to studying the
functionalization scope of the A2B-pyrimidinylcorroles, they
were hence first metalated to afford their Cu analogues.
Copper insertion can readily be achieved by simple stirring of
the Fb corrole with copper(II) acetate in THF,5f and Cu-
pyrimidinylcorroles 5a,b,e were obtained in 71-87% yield
(Scheme 2). Cu-corroles, formally being Cu(III) species, are
diamagnetic at rt and can hence be characterized via NMR
spectroscopy. Recent studies have provided new insights on
the true electronic nature of corrolato copper complexes.11
Substitution of the four meso-chlorine functions was first
pursued by SNAr reactions. Gradual substitution depending
on the reaction temperature was observed. Treatment of Cu-
corrole 5b with 2.3 equiv of 4-tert-butylphenol in DMF at
90 °C afforded mainly the disubstituted A2B-corrole as a
reaction time, the amount of BF3 OEt2, and the building
3
block ratio (Table S1, Supporting Information; Scheme 2).10
Still not satisfied with the yield and the generality of the
method, a more powerful synthetic protocol was pursued. It
was observed during the optimization study that the corre-
sponding A2B2-porphyrins were generally obtained as the
€
ꢁ
(9) Rohand, T.; Dolusic, E.; Ngo, T. H.; Maes, W.; Dehaen, W.
ARKIVOC 2007, (x), 307.
(10) See the Supporting Information for more details.
(11) (a) Broring, M.; Bregier, F.; Consul Tejero, E.; Hell, C.; Holthausen,
M. C. Angew. Chem., Int. Ed. 2007, 46, 445. (b) Alemayehu, A. B.; Gonzalez,
E.; Hansen, L. K.; Ghosh, A. Inorg. Chem. 2009, 48, 7794.
2128 J. Org. Chem. Vol. 75, No. 6, 2010

Ngo et al.
JOCNote
mixture of atropoisomers 6b,c. After chromatographic se-
paration, the R,β- (6b) and R,R-atropoisomers (6c) were
isolated in 69 and 21% yield, respectively. Identification of
the atropoisomers is based on their respective 1H NMR
spectra.10 Sterical reasons might be responsible for the higher
yield of the anti-isomer 6b. R,β-Atropoisomer 6b is inher-
ently chiral, even without considering the fact that Cu-
corroles have recently been described as being chiral due to
their saddled conformation.11b Under less forcing (70 °C) or
less effective SNAr conditions,10 monosubstituted A2B-cor-
role 6a remained in appreciable amounts (32% 6a was
isolated from a reaction at 70 °C). When the reaction was
performed at an elevated temperature (120-140 °C) with a
large excess of 4-tert-butylphenol (12 equiv), tetrasubstituted
Cu-corrole 6d was obtained as the main product (57-
71%),10 with only trace amounts of the trifunctionalized
derivative. Performing the SNAr reaction under the (harsh)
conditions required for full substitution of the corresponding
Cu-AB2-pyrimidinylcorrole (DMF, K2CO3, 175 °C, micro-
wave, 1 h) resulted in 62% 6d, with trace amounts of another
Cu-corrole with higher molecular mass (m/z 1403), appar-
ently due to additional substitution of a methylsulfanyl
moiety.
SCHEME 3. Functionalization of Fb A2B-Pyrimidinylcorroles
A3-Pyrimidinylcorroles.12 A3-pyrimidinylcorroles can also
be prepared by a [2 þ 1] method employing a pyrimidinyl-
DPM and a pyrimidinecarbaldehyde precursor. Both the
procedures optimized for AB2- and A2B-pyrimidinylcorroles
could be applied. On employing the condensation conditions
optimized for A2B-corroles, A3-corrole 9a was prepared in
7% yield. On the other hand, methylthio-substituted A3-
corrole 9b was isolated in 19% yield by a protocol derived
from AB2-pyrimidinylcorroles (0.043 equiv BF3 OEt2). The
3
former method was also applied for the synthesis of unsym-
metrical pseudo-A3-corrole 9c (17% yield) starting from
pyrimidinecarbaldehyde 1b and DPM 2a (Scheme 4).10
Since Fb A3-pyrimidinylcorroles can be expected to be
even more robust than the A2B counterparts, they can be
considered valuable alternatives for the most commonly
used electron-deficient corrole to date, tris(pentafluorophe-
nyl)corrole (tpfc). Moreover, pyrimidinylcorroles are more
versatile scaffolds since numerous substitution patterns are
readily available for these derivatives. SNAr and Suzuki
cross-coupling reactions were conducted in high yields
(83%) starting from 9a affording even more sterically en-
cumbered functionalized corroles (Scheme 4). Cu-metala-
tion of the A3-corroles was not required, since the Fb
analogues were found very robust. Previous experiences with
Cu-insertion reactions in highly electron-deficient corroles
(e.g., tpfc) have even demonstrated some degree of instability
for these derivatives.5f,7 Partial, and subsequent asymmetri-
cal, substitution of the A3-corroles has not been pursued yet.
The purification and identification of the partially substi-
tuted isomers might be cumbersome due to regio- and
atropoisomerism.
Since higher (oxidative) stability of A2B-pyrimidinylcorroles
compared to the one-pyrimidine AB2-analogues can be en-
visaged, modification of the corrole skeleton was also studied
on Fb A2B-corrole 4b. Tetrasubstituted corrole 7 was isolated
in 81% yield after SNAr involving efficient substitution in
DMF at 150 °C (microwave, 1 h) (Scheme 3). The same reac-
tion at 175 °C again caused pentasubstitution (∼10%). Cu-
metalation to enhance the stability of the contracted porphyrin
skeleton is apparently not required. The electron-deficient and
sterically shielding influence of the meso-pyrimidinyl units
endow sufficient stability to the Fb derivatives. Alternatively,
modification of the pyrimidinylcorrole periphery can also be
achieved via Pd-catalyzed cross-coupling reactions. As an
example, Fb A2B-pyrimidinylcorrole 4f was treated with phe-
nylboronic acid under standard Suzuki conditions (Scheme 3),
and sterically congested A2B-corrole 8 was isolated in a nearly
quantitative yield (98%).
While functionalization of the A2B-pyrimidinylcorrole
platform has only been performed by rather simple nucleo-
philes or arylboronic acids, one can easily see the potential
of these methods toward preparation of more complex
(asymmetrically substituted) functional corrole derivatives.
While the inserted phenol groups above and below the
macrocyclic plane are conformationally mobile and might
be located away from the corrole ring, the aryl groups
introduced by Pd-catalyzed methods are inherently located
close to the corrole plane. Both types of double picket fence
corroles might have beneficial properties for metallocorrole-
based (stereo- or regioselective) catalysis.
In conclusion, meso-pyrimidinyl-substituted A2B- and A3-
corroles are versatile building blocks for the construction of
elusive functional corroles toward particular applications.
Both corrole types have been synthesized in an efficient way
by optimization of the macrocyclization conditions earlier
ꢁ
(12) Collman and Decreau synthesized A3-corrole 9a directly from 1a
using either conventional or microwave heating (in 4.5% or 6.2% yield,
ꢁ
respectively). Collman, J. P.; Decreau, R. A. Tetrahedron Lett. 2003, 44,
1207.
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Ngo et al.
JOCNote
SCHEME 4. Derivatization of Fb A3-Pyrimidinylcorroles
2H), 2.84 (s, 6H); 13C NMR (100 MHz, CDCl3) δ 174.0 (C-
SCH3), 163.4 (C-Cl), 148.6, 147.8, 135.4 (CH), 127.5 (CH),
125.8, 124.1 (CH), 122.6 (CH), 117.5 (CH), 110.7, 15.0 (CH3-
S); UV-vis (CH2Cl2) λmax (log ε) 263 (4.63), 300 (4.45), 427
(5.062), 572 (4.236), 614 (4.156).
5,15-Bis[4,6-bis(4-tert-butylphenoxy)-2-methylsulfanylpyri-
midin-5-yl]-10-(4-cyanophenyl)corrole (7). A solution of A2B-
corrole 4b (13.9 mg, 17.7 μmol), 4-tert-butylphenol (32 mg, 213
μmol, 12 equiv), and (finely grounded) K2CO3 (37.5 mg, 271
μmol) in dry DMF (5 mL) was heated by microwave irradiation
at 150 °C (100 W) for 1 h. After the mixture was cooled to rt,
ethyl acetate was added, and the resulting mixture was washed
with distilled water, dried over MgSO4, filtered, and evaporated
to dryness. After purification by column chromatography
(silica, eluent ethyl acetate/heptane 1:10) pure tetrasubstituted
Fb A2B-corrole 7 (17.8 mg, 81%) was obtained as a purple solid:
MS (ESIþ) m/z 1240.4 [M þ H]þ; FTMS (ESI-) calcd for
C76H72N9O4S2 [M - H]- 1238.5143, found m/z 1238.5091; 1H
NMR (400 MHz, CDCl3) δ 9.02 (d, J = 4.0 Hz, 2H, Hβ), 8.95 (d,
J = 4.8 Hz, 2H, Hβ), 8.72 (d, J = 3.8 Hz, 2H, Hβ), 8.50 (d, J =
4.8 Hz, 2H, Hβ), 8.30 (d, J = 7.8 Hz, 2H, CN-Ph), 8.04 (d, J =
7.8 Hz, 2H, CN-Ph), 7.17 (d, J = 8.8 Hz, 8H), 6.93 (d, J = 8.8
Hz, 8H), 2.37 (s, 6H), 1.16 (s, 36H), -1.0--3.0 (sbr, 3H, NH); 13
C
NMR (100 MHz, CDCl3) δ 171.4 (C-SCH3), 169.3, 150.7, 147.9,
135.4 (CH), 131.0 (CH), 125.9 (CH), 120.9 (CH), 116.2 (CH),
100.8, 34.4, 31.4 (CH3), 31.1 (CH3), 14.3 (CH3-S); UV-vis
(CH2Cl2) λmax (log ε) 261 (4.760), 419 (5.038), 574 (4.363), 612
(4.236).
5,15-Bis(4,6-diphenylpyrimidin-5-yl)-10-phenylcorrole (8). To
a solution of A2B-corrole 4f (22 mg, 33 μmol), phenylboronic
acid (32.1 mg, 263 μmol, 8 equiv), and Pd(PPh3)4 (2 mg, 5 mol
%) in toluene (3 mL) was added aq Na2CO3 (2 M, 0.3 mL), and
the mixture was heated by microwave irradiation at 100 °C (100
W) for 1 h. After the mixture was cooled to rt, diethyl ether was
added, and the resulting mixture was washed with distilled
water, dried over MgSO4, filtered, and evaporated to dryness.
After purification by column chromatography (silica, eluent
ethyl acetate/CH2Cl2 1:9), tetrasubstituted Fb A2B-corrole 8
was nearly quantitatively (27.0 mg, 98%) obtained: MS (ESIþ)
m/z 836.5 [M þ H]þ; FTMS (ESIþ) calcd for C57H38N8 [Mþ]
834.3214, found m/z 834.3178; 1H NMR (600 MHz, CDCl3) δ
9.72 (s, 2H, Hpyrim), 8.70 (d, J = 4.1 Hz, 2H, Hβ), 8.48 (d, J = 4.0
Hz, 2H, Hβ), 8.35-8.32 (m, 4H, Hβ), 7.98-7.95 (m, 2H, meso-
Ph), 7.69-7.64 (m, 3H, meso-Ph), 7.10 (d, J = 7.9 Hz, 8H, o-Ph),
6.70 (t, J = 7.6 Hz, 4H, p-Ph), 6.57 (t, J = 7.9 Hz, 8H, m-Ph);
13C NMR (150 MHz, CDCl3) δ 168.5, 158.4 (CH; pyrim),
141.3, 139.1, 134.7 (CH), 132.4, 128.9 (CH), 128.3 (CH), 127.7
(CH), 127.4 (CH), 116.4 (CH), 111.9, 100.1 (CH); UV-vis
(CH2Cl2) λmax (log ε) 277 (4.618), 436 (4.858), 588 (3.917),
653 (3.965).
applied for AB2-pyrimidinylcorroles, and modification of
the corrole perimeter was conducted by effective SNAr and
Suzuki reactions affording highly sterically encumbered
double picket fence functionalized corrole macrocycles.
Experimental Section
Synthesis of A2B-Pyrimidinylcorroles 4a-f (General Proce-
dure 1). A solution of the respective aldehyde (0.381 mmol) in
CH2Cl2 (50 mL), activated with BF3 OEt2 (2 μL, 0.043 equiv),
3
was added dropwise over 6-10 h to a stirred solution of
pyrimidinyldipyrromethane 2a/b (1.143 mmol, 3 equiv) in
CH2Cl2 (200 mL), under an Ar atmosphere and protected from
light. After complete addition, the reaction was continued for
14-18 h (total reaction time ∼24 h). A solution of p-chloranil
(1.143 mmol, 3 equiv) in THF (20 mL) was then added, and the
mixture was heated at reflux (the heating time dependent on the
aldehyde). Subsequently, the solvent was evaporated under
reduced pressure. Pure A2B-corroles were obtained as purple
solids after column chromatographic purification (silica, eluent
CH2Cl2/heptane mixtures).
Acknowledgment. We thank the IWT for a doctoral fel-
lowship to T.H.N., the FWO for financial support and a
postdoctoral fellowship to W.M., and the KU Leuven and
the Ministerie voor Wetenschapsbeleid for continuing finan-
cial support.
5,15-Bis(4,6-dichloro-2-methylsulfanylpyrimidin-5-yl)-10-(4-
nitrophenyl)corrole (4a): addition time 24 h, continued stirring
for 24 h, oxidation time 2 h; eluent CH2Cl2/heptane 4:1; yield
14%; MS (ESIþ) m/z 806.4 [M þ H]þ; FTMS (ESIþ) calcd for
C35H22N9O2S2Cl4 [M þ H]þ 804.0087, found m/z 804.0093; 1H
NMR (400 MHz, CDCl3) δ 9.10 (d, J = 4.3 Hz, 2H, Hβ), 8.67 (d,
J = 4.8 Hz, 2H, Hβ), 8.63 (d, J = 8.6 Hz, 2H), 8.59 (d, J = 4.8
Hz, 2H, Hβ), 8.54 (dbr, J = 4.0 Hz, 2H, Hβ), 8.37 (d, J = 8.6 Hz,
Supporting Information Available: Additional experimental
procedures and data and 1H and 13C NMR spectra for all novel
corroles and precursors. This material is available free of charge
via the Internet at http://pubs.acs.org.
2130 J. Org. Chem. Vol. 75, No. 6, 2010