Porphyrin on a half-shell! Synthesis and characterization of corannulenoporphyrins

Article abstract of DOI:10.1021/jo902592u

An efficient synthetic method for preparing corannulenoporphyrins is described. Nitrocorannulene was reacted with ethyl isocyanoacetate in the presence of a phosphazene base to generate the pivotal corannulenopyrrole intermediate. Following cleavage of the ethyl ester moiety with KOH in ethylene glycol at 180?190 °C, the heptacyclic system was reacted with acetoxymethylpyrroles under mildly acidic conditions to afford tripyrranes. The proton NMR spectra for these tripyrrolic intermediates suggest that they can take on helical geometries, but the conformations are dependent on the nature of the terminal ester groupings and may be altered by solvent interactions. Treatment of a di-tert-butyl ester tripyrrane with TFA cleaved the protective groups, and subsequent condensation with diformylpyrroles in TFA-CH ₂Cl₂, followed by oxidation with DDQ or ferric chloride, gave excellent yields of corannulenoporphyrins. Nickel(II), copper(II), and zinc complexes of this system were also prepared, and the nickel derivative was also further characterized by X-ray crystallography. The same synthetic strategy was also used to prepare a porphyrin with fused acenaphthylene and corannulene subunits. The fused bowl-shaped corannulene provides these porphyrins with a unique structural component that increases solubility by reducing stacking interactions.

Full text of DOI:10.1021/jo902592u

pubs.acs.org/joc
Porphyrin on a Half-Shell! Synthesis and Characterization of
Corannulenoporphyrins†
Holly Boedigheimer, Gregory M. Ferrence, and Timothy D. Lash*
Department of Chemistry, Illinois State University, Normal, Illinois 61790-4160
tdlash@ilstu.edu
Received December 14, 2009
An efficient synthetic method for preparing corannulenoporphyrins is described. Nitrocorannulene was
reacted with ethyl isocyanoacetate in the presence of a phosphazene base to generate the pivotal corannul-
enopyrrole intermediate. Following cleavage of the ethyl ester moiety with KOH in ethylene glycol at
180-190 °C, the heptacyclic system was reacted with acetoxymethylpyrroles under mildly acidic conditions
to afford tripyrranes. The proton NMR spectra for these tripyrrolic intermediates suggest that they can take
on helical geometries, but the conformations are dependent on the nature of the terminal ester groupings and
may be altered by solvent interactions. Treatment of a di-tert-butyl ester tripyrrane with TFA cleaved the
protective groups, and subsequent condensation with diformylpyrroles in TFA-CH2Cl2, followed by
oxidation with DDQ or ferric chloride, gave excellent yields of corannulenoporphyrins. Nickel(II), copper-
(II), and zinc complexes of this system were also prepared, and the nickel derivative was also further charac-
terized by X-ray crystallography. The same synthetic strategy was also used to prepare a porphyrin with
fused acenaphthylene and corannulene subunits. The fused bowl-shaped corannulene provides these porphy-
rins with a unique structural component that increases solubility by reducing π-π stacking interactions.
Introduction
corannulene system is due in part to its unusual curved
geometry, which corresponds to one-third of the cage-like
structure found in buckminsterfullerene (C60). Now that
gram quantities of corannulene can be synthesized using
currently available methodologies, the chemistry of this
“buckybowl” can be explored in detail.5 Furthermore, these
methods have allowed numerous derivatives to be synthe-
sized that exhibit unique properties, including liquid crys-
talline materials,6 dendimers,7 bicorannulenes,8 and fused
Corannulene (1) is a bowl-shaped hydrocarbon that has
attracted considerable attention since it was first described
by Barth and Lawton in 1966.1 Although the original
synthesis involved 16 consecutive steps, more direct routes
were subsequently developed using flash vacuum pyro-
lysis.2 Fairly recently, more convenient solution phase syn-
theses have been developed.3,4 The continued interest in the
† Part 26 in the series “Porphyrins with Exocyclic Rings”.
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Tsefrikas, V. M.; Scott, L. T. Organometallics 2005, 24, 1394–1397. (c)
Petrukhina, M. A.; Sevryugina, Y.; Rogachev, A. Y.; Jackson, E. A.; Scott,
L. T. Organometallics 2006, 25, 5492–5495.
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2518 J. Org. Chem. 2010, 75, 2518–2527
Published on Web 03/18/2010
DOI: 10.1021/jo902592u
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2010 American Chemical Society

Boedigheimer et al.
JOCArticle
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SCHEME 1
SCHEME 2
These properties also make the incorporation of porphyrins into
nanomolecular systems desirable, particularly given the well-
defined geometry of the porphyrin macrocycle.32 Ring fusion
allows this desirable geometry to be extended and can thereby
lead to the construction of molecular wires or nanoscale de-
vices.33 However, ring-fused porphyrins of this type are often
poorly soluble in organic solvents, and this places limitations on
their applications. The curved geometry of a fused corannulene
unit would decrease π-π stacking interactions and could poten-
tially increase the solubility of annulated porphyrins. Further-
more, the curved architecture of corannulene will greatly affect
intermolecular associations and could lead to an enhancement of
fullerene-porphyrin interactions. Hence, the development of a
synthetic route to corannulenoporphyrins would represent a
significant departure from previous investigations in this area.
this synthesis, crude nitrocorannulene was reacted with ethyl
isocyanoacetate in the presence of 7 in THF, and the related
corannulenopyrrole 8 was isolated in 50% yield. The ester
group of 8 could then be saponified with concomitant
decarboxylation using KOH in ethylene glycol at 180-
190 °C to give the unsubstituted corannulenopyrrole 9 in
quantitative yields. This pyrrole was reasonably stable, but
the surface of the solid material became discolored over the
period of several hours, and prolonged exposure to air led to
a significant amount of decomposition.
Results and Discussion
Nitroalkenes react with esters of isocyanoacetic acid in the
presence of a non-nucleophilic base such as DBU to give
pyrrole esters.34,35 In some cases, this chemistry can be
extended to the reaction of isocyanoacetates with nitroaro-
matic compounds, and this provides a convenient route to
c-annelated pyrroles 5 (Scheme 1). This strategy has been
applied in the synthesis of naphthopyrroles, phenanthropyr-
roles, acenaphthopyrroles, fluoranthopyrroles, and many
other ring-fused pyrroles,36 and these heterocyclic deriva-
tives have been used as intermediates in the synthesis of ring-
fused porphyrins.15 This approach therefore provides a
viable methodology for the synthesis of corannulenopyrroles
from nitrocorannulene (6, Scheme 2). Although a synthesis
of 6 has been noted,37 no details on the preparation of this
compound are available in the literature. We found that the
treatment of corannulene with nitronium tetrafluoroborate
gave good yields of reasonably pure samples of 6 that could
be taken on directly for the Barton-Zard pyrrole synthesis.
However, a small sample was further purified by column
chromatography and fully characterized. In other work, we
had obtained superior yields of pyrrolic products using
phosphazene base 7 in place of DBU in the Barton-Zard
chemistry.38 Hence, in order to maximize the efficiency of
Corannulenopyrroles 8 and 9 are representatives of a new
heterocyclic system and were therefore carefully character-
ized. In DMSO-d6, the proton NMR spectrum of 8 showed
the pyrrole CH at 8.32 ppm and the NH at 13.0 ppm, values
that are consistent with a pyrrolic structure of this type. The
corannulene unit is asymmetrical, and the eight associated
protons give rise to eight different doublets or AB quartets in
the range of 7.9-8.9 ppm. The carbon-13 NMR spectrum
showed 22 resonances for the aromatic carbons between 116
and 136 ppm, an ester carbonyl peak at 160.7 ppm, and the
aliphatic ester carbons at 14.7 and 60.4 ppm. The IR
spectrum showed the ester carbonyl stretch at 1657 cm-1, a
value that is typical for pyrrole esters and which reflects the
highly electron-donating characteristics of the pyrrole nu-
cleus. The EIMS for 8 showed loss of EtOH as the primary
fragmentation pathway, followed by loss of CN radical and
CO to give a tropylium-type species 10 (Scheme 3). Coran-
nulenopyrrole 9 also showed properties that were similar to
the constituent pyrrole and corannulene subunits. The NMR
data clearly demonstrated the presence of a plane of sym-
metry, and the carbon-13 NMR spectra in CDCl3 or DMSO-
d6 showed a total of 12 resonances in the aromatic region.
The EIMS for 9 showed a strong molecular ion at m/z 289
together with a moderately strong doubly charged ion. The
favored fragmentation pathway in this case involved sequen-
tial loss of H• and HCN to again give cation 10 (Scheme 3).
The synthesis of the desired corannulenoporphyrin 11 was
accomplished by using the “3 þ 1” variant of the MacDonald
methodology (Scheme 4).21,39,40 Corannulenopyrrole 9 was
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SCHEME 3
SCHEME 4
reacted with 2 equiv of an acetoxymethylpyrrole 12 and
acetic acid in an alcohol solvent to give the corresponding
tripyrranes 13. When 9 was reacted with benzyl ester 12a41 in
refluxing ethanol, the insoluble product 13a could be filtered
off in 73% yield. However, when 9 was reacted with 12b,42
the corresponding di-tert-butyl ester 13b remained in solu-
tion and had to be precipitated out by pouring the reaction
mixture into ice-water. In this fashion, the crude tripyrrane
could be isolated in 86% yield. As tripyrranes of this type are
not sufficiently stable to allow purification by column chro-
matography, this intermediate had to be used directly for
porphyrin synthesis. Nevertheless, the di-tert-butyl ester was
a convenient intermediate in our studies as the ester protec-
tive groups can be cleaved and taken on for macrocycle
formation in a one-step procedure. Dibenzyl ester 13a can
also easily be deprotected by hydrogenolysis over 10% Pd/C,
but this would require the isolation of an intermediary
dicarboxylic acid. Although 13a was not used to prepare
corannulenoporphyrins, it was isolated in pure form and
fully characterized. The proton NMR data for 13a in CDCl3
gave broadened resonances, and the bridge methylenes and
benzyl ester CH2 units gave rise to a very broad 6H absorp-
tion between 4.1 and 4.7 ppm and a further broad 2H peak at
3.6 ppm. The complexity of this spectrum, together with the
upfield shift for the benzyl CH2 resonances, is typical for
tripyrranes and is attributable to the tripyrrolic unit taking
on a helical geometry.43 This conformation is also beneficial
for macrocycle formation. Another feature of the spectrum is
that the terminal benzyl ester units are shielded because they
fall over the π-system for the other end of the tripyrrole. The
ortho-, meta-, and para-protons for the benzyl ester gave rise
to resonances at 6.64, 6.93, and 7.06 ppm, significantly
upfield from the expected values and again consistent with
the tripyrrane taking on a helical conformation. Interest-
ingly, the proton NMR spectrum of 13a in DMSO-d6 was
well-resolved and showed none of the atypical upfield shifts
observed in CDCl3. In DMSO-d6, the bridge CH2 units
appeared at 4.55 ppm (4H, s), the benzyl methylenes were
observed as a 4H singlet at 5.27 ppm, and the terminal C6H5
groups gave rise to multiplets between 7.30 and 7.45 ppm.
The marked differences in the spectra are due to the DMSO
hydrogen bonding to the NH protons, which in turn alters
the conformation of the tripyrrolic system. Tripyrrane 13b
also shows a well-resolved proton NMR spectrum in CDCl3
and gave no unusual upfield shifts that were consistent with
the compound taking on a helical conformation. This app-
ears to be typical for the tert-butyl ester derivatives of
tripyrranes21,22 and is most likely due to unfavorable steric
interactions due to the bulky ester units. Nevertheless,
following the loss of the tert-butyl esters, the deprotected
tripyrrane can again take on a required conformation for
porphyrin formation.
Tripyrrane 13b was stirred with TFA for 10 min at room
temperature, the solution diluted with dichloromethane,
pyrrole dialdehyde 14 immediately added, and the mixture
stirred under nitrogen for 16 h. The resulting mixture
was oxidized with ferric chloride44 or DDQ. Following
(41) Johnson, A. W.; Kay, I. T.; Markham, E.; Price, R.; Shaw, K. B. J.
Chem. Soc. 1959, 3416–3424.
(42) Clezy, P. S.; Crowley, R. J.; Hai, T. T. Aust. J. Chem. 1982, 35, 411–
421.
(43) Jiao, W.; Lash, T. D. J. Org. Chem. 2003, 68, 3896–3901.
(44) Lash, T. D.; Richter, D. T.; Shiner, C. M. J. Org. Chem. 1999, 64,
7973–7982.
J. Org. Chem. Vol. 75, No. 8, 2010 2521

Boedigheimer et al.
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2þ
dication 11H2 in TFA-CDCl3 showed the meso-protons
further downfield at 10.63 and 11.68 ppm, while the NH
resonances were observed near -3 ppm. These results sug-
gest that the diatropic ring current for the dication is
enhanced compared to the free base structure, as is com-
monly the case for protonated porphyrins, but the shifts are
also modulated by the presence of two positive charges. An
indirect measure of the porphyrin diatropicity can be taken
from the downfield shift of nearby protons, and by this
2þ
measure, 11H2 actually shows a decreased ring current.
The methyl substituents in 11 gave a 6H singlet at 3.75 for the
free base in CDCl3, but this peak shifted slightly upfield to
3.69 ppm for the dication in TFA-CDCl3. The CH2 units for
the ethyl substituents showed a similar upfield shift upon
protonation. This effect is also mirrored for the corannulene
protons that are nearest to the porphyrin macrocycle as they
give rise to a 2H doublet at 9.57 ppm for the free base form of
11 in CDCl3, but this resonance shifts upfield to 9.32 ppm for
the dication 11H22þ in TFA-CDCl3.47 Therefore, the overall
data indicate that the diatropicity is slightly lowered for the
dication. The proton NMR data in CDCl3 or TFA-CDCl3
were consistent with the presence of a plane of symmetry.
This was confirmed by the carbon-13 NMR spectrum of
FIGURE 1. UV-vis spectra of corannulenoporphyrin 11. Blue
line: free base in 1% Et3N-chloroform. Red line: Dication 11H2
in 1% TFA-chloroform.
2þ
2þ
11H2 in TFA-CDCl3, which showed 5 sp3 carbon reso-
nances between 12 and 21 ppm, two resonances for the meso-
bridge carbons at 98.9 and 99.3 ppm, and 17 of the 18
expected resonances for the pyrrole and corannulene car-
bons between 126 and 145 ppm.
FIGURE 2. Partial 500 MHz proton NMR spectrum of corannu-
lenoporphyrin 11 in CDCl3 showing details of the downfield region.
Metalation of 11 was accomplished with nickel(II),
copper(II), or zinc acetate in refluxing DMF. The resulting
nickel(II) and copper(II) porphyrins 15a and 15b, respec-
tively, were reasonably soluble, unlike metallo-derivatives of
phenanthroporphyrins 2a, acenaphthoporphyrins 3, or re-
lated systems (e.g., 4),19,22,23 but the zinc complex 15c was
only sparingly soluble in chloroform. Proton NMR data
could be obtained for the diamagnetic nickel(II) and zinc
porphyrins 15a and 15c, but it is not possible to characterize
paramagnetic copper(II) porphyrins by NMR spectroscopy.
The proton NMR spectrum for the nickel(II) complex
showed the meso-protons as two 2H singlets at 9.63 and
10.63 ppm, significantly upfield from the values obtained for
the free base porphyrin, and the reduced ring current effect
can also be discerned from the chemical shifts for closely
connected units.47 The methyl groups give a 6H resonance at
3.42 ppm, compared to 3.75 ppm for 11, while the proximal
corannulene protons show up at 9.17 ppm, a 0.4 ppm upfield
shift compared to the free base porphyrin. Only poor-quality
NMR spectra could be obtained for the zinc complex 15c in
CDCl3, but the highly aggregated metalloporphyrin showed
two very broad peaks for the meso-protons at 9.67 and 10.53
ppm. However, addition of a drop of pyrrolidine to the
NMR tube greatly increased the solubility of the zinc por-
phyrin and allowed well-resolved NMR spectra to be ob-
tained. Zinc porphyrins coordinate with the secondary
amine, and this disrupts π-π stacking interactions. The
proton NMR spectrum now showed two sharp 2H singlets
for the meso-protons at 9.90 and 11.07 ppm, and these results
indicate that the diatropic character of 15c lies midway
between the free base porphyrin 11 and the nickel(II) com-
plex 15a. This interpretation is supported by the chemical
shifts for nearby protons. The methyl resonance for 15c is
observed at 3.56 ppm, while the downfield corannulene
extraction, purification by column chromatography on
neutral alumina, and recrystallization from chloroform-
methanol, corannulenoporphyrin 11 was isolated in 68%
yield. The UV-vis absorption spectrum for 11 in chloroform
gave a strong Soret band at 429 nm and a series of Q bands
from 523 to 644 nm (Figure 1). Although these absorptions
are bathochromically shifted compared to octaethylpor-
phyrin, the presence of a fused corannulene moiety has a
minimal effect on the porphyrin chromophore. Addition of
TFA gives a dication 11H22þ with a split Soret band at 427
and 446 nm and weaker absorptions at 569 and 619 nm
(Figure 1). Again, this spectrum is somewhat modified
compared to porphyrin dications without fused aromatic
rings, but the wavelength shifts are still minor. Although
some annelated porphyrins are greatly affected by ring
fusion, phenanthroporphyrins, fluoranthoporphyrins, and
related systems have similar spectroscopic properties.45
Hence, the presence of a fused buckybowl structure does
not significantly alter the electronic properties of the por-
phyrin macrocycle. Porphyrin 11 is reasonably soluble in
chlorinated solvents and gave a high-quality proton NMR
spectrum in CDCl3 (Figure 2). As would be expected for an
aromatic porphyrin system,46 the internal NHs gave rise to a
2H upfield resonance at -3.4 ppm, whereas the meso-pro-
tons were shifted downfield to give two 2H singlets at 10.10
and 11.26 ppm.47 The latter resonance is further deshielded
due to its proximity to the corannulene moiety. The related
(45) Lash, T. D. J. Porphyrins Phthalocyanines 2001, 5, 267–288.
(46) Medforth, C. J. In The Porphyrin Handbook; Kadish, K. M., Smith,
K. M., Guilard, R., Eds.; Academic Press: San Diego, CA, 2000; Vol. 5, pp
1-80.
(47) Proton NMR spectra for 11, 11H22þ, 15a, and 16 were fully assigned
using 1H-1H COSY and NOE difference proton NMR spectroscopy. For
details, see Supporting Information.
2522 J. Org. Chem. Vol. 75, No. 8, 2010

Boedigheimer et al.
JOCArticle
FIGURE 3. UV-vis spectra of metallocorannulenoporphyrins in
chloroform. Red line: nickel(II) complex 15a. Blue line: copper(II)
complex 15b.
FIGURE 5. ORTEP-3 drawing (50% probability level, hydrogen
atoms drawn arbitrarily small) of compound 15a. Selected bond
lengths (A): Ni-N(23) 1.943(5), Ni-N(24) 1.959(5), Ni-N(21)
˚
1.960(5), Ni-N(22) 1.964(5), N(21)-C(1) 1.376(8), N(21)-C(4)
1.400(7), N(22)-C(9) 1.376(8), N(22)-C(6) 1.377(7), N(23)-C(11)
1.387(8), N(23)-C(14) 1.403(8), N(24)-C(16) 1.384(7), N(24)-C-
(19) 1.389(7), C(1)-C(20) 1.402(8), C(1)-C(2) 1.437(8), C(2)-C(3)
1.398(8), C(3)-C(4) 1.442(8), C(4)-C(5) 1.366(8), C(5)-C(6)
1.363(8), C(6)-C(7) 1.442(9), C(7)-C(8) 1.358(9), C(8)-C(9)
1.451(9), C(9)-C(10) 1.376(9), C(10)-C(11) 1.369(9), C(11)-C(12)
1.446(8), C(12)-C(13) 1.333(9), C(13)-C(14) 1.442(9), C(14)-C-
(15) 1.360(9), C(15)-C(16) 1.371(9), C(16)-C(17) 1.430(9), C(17-
)-C(18) 1.345(8), C(18)-C(19) 1.449(8), C(19)-C(20) 1.356(8),
C(2)-C(2a) 1.454(8), C(2a)-C(2b) 1.447(8), C(2b)-C(2c)
1.368(9), C(2c)-C(2d) 1.450(8), C(2d)-C(3 g) 1.363(8), C(2d)-C-
(2e) 1.456(9), C(2e)-C(2f) 1.380(9), C(2f)-C(2g) 1.444(9), C(2g-
)-C(3f) 1.352(8), C(2g)-C(2h) 1.457(9), C(2h)-C(2i) 1.379(9),
C(2i)-C(3d) 1.436(9), C(3)-C(3a) 1.463(8), C(3a)-C(3i) 1.368(8),
C(3a)-C(3b) 1.452(8), C(3b)-C(3c) 1.379(8), C(3c)-C(3d)
1.439(9), C(3d)-C(3e) 1.389(8), C(3e)-C(3i) 1.402(8), C(3e)-C(3f)
1.410(9), C(3f)-C(3g) 1.434(8), C(3g)-C(3h) 1.406(8), C(3h)-
C(3i) 1.438(8).
FIGURE 4. UV-vis spectra of zinc corannulenoporphyrin 15c.
Red line: 15c in chloroform. The inset shows the weak absorptions
at longer wavelengths. Blue line: 15c in 1% pyrrolidine-chloroform.
doublet shifts to 9.55 ppm. The plane of symmetry in
metalloporphyrins 15a and 15c is also evident in both the
proton and carbon-13 NMR spectra, and all of the expected
aromatic carbons resolved as separate peaks for these deri-
vatives. The meso-carbon resonances for both complexes
again show up between 96 and 100 ppm. The UV-vis
absorption spectra for these metalloporphyrins were also
insightful. The nickel(II) complex 15a showed a Soret band
at 420 nm and weaker absorptions at 565 and 589 nm
(Figure 3). These bands were bathochromically shifted in
the copper(II) chelate 15b to 426, 552, and 595 nm (Figure 3).
Metalloporphyrins show a trend of bathochromic shifts
across the periodic table from nickel to copper to zinc,48
and these trends are commonly also seen in modified por-
phyrin systems.45 The zinc complex 15c did indeed show a
further shift to longer wavelength, giving a Soret band at
431 nm and the principal Q bands at 554 and 601 nm
(Figure 4). However, weak absorptions were also noted at
780 and 854 nm. This spectrum, which corresponds to
aggregated zinc porphyrin 15c, is significantly modified
and bathochromically shifted on addition of pyrrolidine.
The Soret band is intensified and shifted to 446 nm, and
minor bands are now observed at 562, 610, and 669 nm
(Figure 4).
(NiOEP).49 The corannulene unit also shows bond lengths
that closely resemble other corannulene structures,50 apart
from the bond length for ring fusion (C2-C3), which is
50
˚
approximately 0.02 A longer than the other “rim” bonds.
Even the bowl shape is essentially isostructural with corannu-
˚
lene, as evidenced by the 0.81 A separation between the
centroid defined by the 10 peripheral carbon atoms. This
˚
corresponds to the 0.89 and 0.86 A distances observed in two
crystallographically independent molecules in pure corannu-
lene.50 Most nickel(II)-containing porphyrins are significantly
ruffled or saddled,49,51,52 although crystal packing forces may
be sufficient to induce planar conformations in the solid
state.49 For instance, NiOEP has been characterized in three
crystalline forms, two of which are near planar while the other
one of these is highly ruffled.49 Nevertheless, the ruffled
conformation of NiOEP has also been shown to be favored
insolution,51 and thismayalso be the case for 15abased on the
reduced downfield shifts for the external protons in the proton
NMR spectra for the nickel(II) complex.
Slow evaporation of a solution of nickel(II) complex 15a in
CDCl3 gave crystals that were suitable for X-ray crystal-
lographic analysis (Figure 5). The porphyrin macrocycle is
essentiallyplanar andshows bond lengths thatare very similar
to the values reported for nickel(II) octaethylporphyrin
Acenaphthoporphyrins 3 show highly modified UV-vis
absorptions and strong Q absorptions between 650 and 700
nm.22 These valuable characteristics made the hybrid cor-
annulenoacenaphthoporphyrin 16 a worthwhile target for
(50) (a) Petrukhina, M. A.; Andreini, K. W.; Mack, J.; Scott, L. T. J. Org.
Chem. 2005, 70, 5713–5716. (b) Sevryugina, Y.; Rogachev, A. Y.; Jackson,
E. A.; Scott, L. T.; Petrukhina, M. A. J. Org. Chem. 2006, 71, 6615–6618.
(51) Alden, R. G.; Crawford, B. A.; Doolen, R.; Ondrias, M. R.; Shelnutt,
J. A. J. Am. Chem. Soc. 1989, 111, 2070–2072.
(48) Porphyrins and Metalloporphyrins; Smith, K. M., Ed., Elsevier:
Amsterdam, 1975; pp 871-889.
(49) (a) Meyer, E. F., Jr. Acta Crystallogr., Sect. B 1972, 28, 2162–2167.
(b) Cullen, D. L.; Meyer, E. F., Jr. J. Am. Chem. Soc. 1974, 96, 2095–2102. (c)
Brennan, T. D.; Scheidt, W. R.; Shelnutt, J. A. J. Am. Chem. Soc. 1988, 110,
3919–3924.
(52) Grigg, R.; Trocha-Grimshaw, J.; King, T. J. J. Chem. Soc., Chem.
Commun. 1978, 571–572.
J. Org. Chem. Vol. 75, No. 8, 2010 2523

Boedigheimer et al.
JOCArticle
C60 before the buckminsterfullerene absorptions obscured
the peaks due to the corannulenoporphyrin. Nevertheless,
interactions with fullerenes are likely to be fairly weak, and
these molecules may need to be further elaborated to provide
suitable cavities for these interactions.
Conclusions
Nitrocorannulene has been shown to undergo a Barton-
Zard pyrrole condensation with ethyl isocyanoacetate in the
presence of a phosphazene base to give a a novel corannu-
lenopyrrole. The carboxylate group was cleaved in virtually
quantitative yield to afford the unsubstituted c-annelated
pyrrole, and further reaction with acetoxymethylpyrroles in
the presence of acetic acid gave tripyrranes. The terminal
ester units were cleaved, and further reaction with pyrrole
dialdehydes in TFA-CH2Cl2 afforded excellent yields of
corannulenoporphyrins 11 and 16. Nickel(II), copper(II),
and zinc complexes of corannulenoporphyrin 11 were also
easily prepared. The new porphyrin systems retained highly
diatropic characteristics and showed only minor modifica-
tions to their UV-vis spectra. The nickel(II) complex gave
crystals that were suitable for X-ray crystallographic analy-
sis and showed the expected curved architecture for the fused
corannulene unit. These results show that corannulenopor-
phyrins are easily prepared from corannulene and the novel
shell-like geometry of the fused corannulene system may
provide access to more complex supramolecular systems.
FIGURE 6. UV-vis spectra of acenaphthoporphyrin 16. Blue line:
free base in 1% Et3N-chloroform. Red line: Dication 16H22þ in 1%
TFA-chloroform.
SCHEME 5
synthesis. This porphyrin was prepared by reacting tripyr-
rane 13b with acenaphthopyrrole dialdehyde 1722c in the
presence of TFA, followed by oxidation with ferric chloride
(Scheme 5). Following purification by column chromato-
graphy and recrystallization from chloroform-methanol,
the π-extended porphyrin was isolated in 33% yield. The
UV-vis absorption spectrum showed a weakened Soret
band at 438 nm, followed by a series of weaker absorptions
extending to 683 nm (Figure 6). In 1% TFA-chloroform, a
split Soret band at 449 and 470 nm is observed followed by
several weaker bands culminating in a relatively strong
absorption at 656 nm (Figure 6). These results demonstrate
that 16 has a similarly modified chromophore to other
acenaphthoporphyrins. Corannulenoacenaphthoporphyrin
16 has poor solubility in chloroform and gave only a weak
aggregated NMR spectrum in CDCl3, but the dication
Experimental Section
Nitrocorannulene (6). A solution of nitronium tetrafluorobo-
rate (133 mg, 1.00 mmol) in anhydrous acetonitrile (25 mL) was
added over a 30 min period to a stirred solution of corannulene
(250 mg, 1.00 mmol) in dichloromethane (45 mL), and the
resulting mixture was stirred under reflux overnight. The mix-
ture was washed with water (ꢀ3), dried over sodium sulfate, and
evaporated to give a yellow-orange residue (290 mg, 0.983
mmol, 98%). A pure sample of nitrocorannulene was obtained
by running the crude material through a silica column, eluting
with cyclohexane. Recrystallization from toluene gave the nitro
1
compound as a yellow solid: mp 248-249 °C; H NMR (500
MHz, CDCl3) δ 7.82-7.90 (4H, 2 overlapping AB quartets, J =
8.7 Hz), 7.89-7.93 (2H, AB quartet, J = 8.8 Hz), 7.98 (1H, d,
J = 9.0 Hz), 8.54 (1H, d, J = 9.0 Hz), 8.97 (1H, s); 13C NMR
(CDCl3) δ 123.3, 126.6, 127.47, 127.52, 127.65, 127.70, 128.3,
128.5, 128.7, 129.2, 130.0, 131.2, 131.4, 132.9, 134.90, 134.93,
135.7, 136.8, 138.0, 146.2; HRMS (EI) m/z calcd for C20H9NO2
295.0633, found 295.0629.
2þ
16H2 in TFA-CDCl3 gave a well-resolved proton NMR
spectrum showing the internal NHs as two broad 2H reso-
nances between -2 and -3.5 ppm. The meso-protons are
shifted downfield to give two 2H singlets at 11.08 and 11.65
ppm, and the remaining data are consistent with a highly
diatropic system.47 The carbon-13 NMR spectrum in TFA-
CDCl3 confirms the presence of a plane of symmetry and
also shows the meso-carbon resonances at 99.4 and 101.1
ppm. These results demonstrate that this synthetic strategy
allows access to porphyrins with two different fused aro-
matic subunits, but the curvature of the corannulene system
does not significantly enhance the solubility of further π-
extended systems.
The association of nickel(II) corannulenoporphyrin 15a
with C60 was also briefly examined. Addition of 1 equiv of
C60 in toluene-d8 to a solution of 15a in CDCl3 gave rise to no
significant shifts in the proton NMR spectrum. Similarly, a
spectroscopic titration of C60 in toluene to a dilute solution
of 15a in toluene showed no shifts in the UV-vis absorp-
tions, but this experiment could only be taken to 20 equiv of
Ethyl corannuleno[1,2-c]pyrrole-1-carboxylate (8). Phospha-
zene base 7 (1.58 g) was added dropwise to a stirred solution of
nitrocorannulene (1.20 g, 4.06 mmol) and ethyl isocyanoacetate
(460 mg, 4.07 mmol) in freshly distilled THF (100 mL), and the
resulting solution was stirred at room temperature overnight.
The solution was diluted with dichloromethane, washed with
water, and evaporated under reduced pressure. The residue was
purified by flash chromatography on a silica column, eluting
initially with 25% cyclohexane/dichloromethane and then in-
creasing proportions of dichloromethane. The product fraction
was evaporated under reduced pressure and recrystallized from
toluene to give the corannulenopyrrole ethyl ester (0.712 g, 2.03
mmol, 50%) as a yellow crystals: mp 233-235 °C; IR (Nujol
mull) ν 3273 (NH stretch), 1657 cm-1 (CdO stretch); 1H NMR
(500 MHz, DMSO-d6) δ 1.47 (3H, t, J = 7.1 Hz), 4.50 (2H, q,
J = 7.1 Hz), 7.90-7.98 (4H, two overlapping AB quartets),
7.99 (1H, d, J = 8.8 Hz), 8.02 (1H, d, J = 8.6 Hz), 8.19 (1H, d,
2524 J. Org. Chem. Vol. 75, No. 8, 2010

Boedigheimer et al.
JOCArticle
J = 8.6 Hz), 8.32 (1H, d, J = 3.2 Hz), 8.90 (1H, d, J = 8.8 Hz),
13.02 (1H, br s); 13C NMR (DMSO-d6) δ 14.7, 60.4, 116.6, 119.2,
122.9, 125.0, 125.3, 125.9, 126.5, 126.6, 126.96, 126.98, 127.4,
127.5, 128.09, 128.10, 129.2, 130.1, 130.3, 133.1, 134.43, 134.46,
134.9, 136.0, 160.7; EIMS (70 eV) m/z (relative intensity) 362
(15), 361 (55, Mþ), 316 (18, [M - OEt]þ), 315 (59, [M -
EtOH]þ), 290 (24), 289 (100, [M - EtOH - CN]þ), 288 (27),
287 (31, [M - EtOH - CO]þ), 286 (27), 261 (37, [M - EtOH -
CN - CO]þ); HRMS (EI) m/z calcd for C25H15NO2 361.1103,
found 361.1102. Anal. Calcd for C25H15NO2: C, 83.09; H, 4.18;
N, 3.87. Found: C, 83.52; H, 4.02; N, 3.85.
mmol, 86%) as a light brown powder: mp 138 °C dec This material
was used without further purification: 1H NMR (500 MHz,
CDCl3) δ 1.00 (6H, t, J = 7.5 Hz), 1.47 (18H, s), 2.28 (6H, s),
2.41 (4H, q, J = 7.5 Hz), 4.53 (4H, s), 7.78 (2H, d, J = 8.7 Hz), 7.82
(2H, d, J = 8.7 Hz), 7.84-7.87 (4H, AB quartet, J = 8.5 Hz),
8.11 (1H, br s), 8.50 (2H, br s); 13C NMR (CDCl3) δ 10.7, 15.6,
17.5, 25.2, 28.6, 80.6, 119.2, 119.6, 121.6, 124.4, 124.7, 126.2,
126.4, 127.2, 127.3, 127.58, 127.65, 129.2, 130.6, 134.8, 135.4,
137.0, 161.3; HRMS (EI) m/z calcd for C48H49N3O4 731.3723,
found 731.3727.
8,12,13,17-Tetraethyl-7,18-dimethylcorannuleno[1,2-b]porphy-
rin (11). In a 100 mL pear-shaped flask, crude tripyrrane di-tert-
butyl ester 13b (120 mg, 0.164 mmol) was stirred with TFA (2 mL)
under nitrogen for 10 min. The mixture was diluted with dichlor-
omethane (98 mL), pyrrole dialdehyde 1453 (29 mg, 0.16 mmol) was
added, and the resulting mixture was stirred for 16 h. The mixture
was neutralized by the dropwise addition of triethylamine, DDQ
(38 mg) was added, and the resulting mixture was stirred for a
further 1 h. The solution was washed with water and evaporated
under reduced pressure. The residue was purified by column
chromatography on grade 3 alumina, eluting with dichloro-
methane, and the product eluted as a dark red band. Recrystalliza-
tion from chloroform-methanol gave the corannulenoporphyrin
(74 mg, 0.11 mmol, 68%) as dark purple crystals: mp >300 °C;
UV-vis (1% Et3N-CHCl3) λmax (log10 ε) 370 (sh, 4.64), 407 (sh,
4.95), 429 (5.38), 523 (3.86), 562 (4.66), 578 (4.39), 631 (3.03), 644
nm (3.19); UV-vis (1% TFA-CHCl3) λmax (log10 ε) 427 (5.22), 446
Corannuleno[1,2-c]pyrrole (9). Potassium hydroxide (1.10 g)
and 5 drops of hydrazine were added to a mixture of ethyl ester 8
(400 mg, 1.14 mmol) and ethylene glycol (50 mL), and nitrogen
was bubbled through the mixture for 5 min. The stirred mixture
was heated at 180-190 °C for 1 h under nitrogen and the resulting
mixture poured into ice-water. The precipitate was suction
filtered, washed well with water, and dried in vacuo to give the
unsubstituted corannulenopyrrole (314 mg, 1.09 mmol, 96%) as
1
an off-white solid: mp 185-188 °C dec; H NMR (500 MHz,
CDCl3) δ 7.69 (2H, d, J = 2.8 Hz), 7.75 (2H, d, J = 8.7 Hz), 7.81
(2H, d, J = 8.7 Hz), 7.85 (2H, d, J = 8.5 Hz), 7.90 (2H, d, J = 8.5
Hz), 9.00 (1H, br s); 1H NMR (500 MHz, DMSO-d6) δ 7.84 (2H,
d, J = 8.7 Hz), 7.90 (2H, d, J = 8.7 Hz), 7.93 (2H, d, J = 2.8 Hz),
7.94 (2H, d, J = 8.5Hz), 8.04 (2H, d, J = 8.5 Hz), 12.10 (1H, br s);
13C NMR (CDCl3) δ 112.0, 122.4, 124.9, 126.1, 127.26, 127.28,
127.4, 129.4, 130.6, 134.8, 135.8, 137.1; 13C NMR (DMSO-d6) δ
113.1, 120.9, 125.4, 125.9, 127.4, 127.5, 127.9, 128.6, 130.3, 133.3,
135.0, 136.0; EIMS (70 eV) m/z (relative intensity) 290 (23), 289
(100, Mþ), 288 (15, [M - H]þ), 261 (21, [M - H - HCN]þ), 144.6
(20, M2þ), 130.7 (22); HRMS (EI) m/z calcd for C22H11N
1
(5.16), 569 (4.25), 618 nm (4.60); H NMR (500 MHz, CDCl3)
δ-3.40 (2H, br s), 1.94 (6H, t, J= 7.7 Hz), 2.08 (6H, t, J=7.7Hz),
3.75 (6H, s), 4.05 (4H, q, J = 7.7 Hz), 4.37 (4H, q, J = 7.7 Hz), 7.96
(2H, d, J = 8.6 Hz), 8.03 (2H, d, J = 8.6 Hz), 8.37 (2H, d, J = 8.7
Hz), 9.57 (2H, d, J = 8.7 Hz), 10.10 (2H, s), 11.26 (2H, s); 1H NMR
(500 MHz, TFA-CDCl3) δ -3.47 (1H, br s), -2.99 (3H, br s), 1.72
(6H, t, J = 7.7 Hz), 1.85 (6H, t, J = 7.7 Hz), 3.69 (6H, s), 4.13 (4H,
q, J = 7.7 Hz), 4.31 (4H, q, J = 7.7 Hz), 7.97-8.02 (4H, AB
quartet, J = 8.6 Hz), 8.44 (2H, d, J = 8.7 Hz), 9.32 (2H, d, J = 8.7
Hz), 10.63 (2H, s), 11.68 (2H, s); 13C NMR (TFA-CDCl3) δ 12.0,
16.7, 17.4, 20.1, 20.6, 98.9, 99.3, 126.3, 127.7, 128.1, 129.1, 130.7,
131.9, 133.8, 135.5, 137.2, 138.2, 138.6, 139.1, 142.0, 142.2, 143.0,
144.1, 144.5; HRMS (EI) m/z calcd for C48H40N4 672.3253, found
289.0892, found 289.0891. Anal. Calcd for C22H11N 1/2H2O: C,
3
88.57; H, 4.05; N, 4.69. Found: C, 88.80; H, 3.85; N, 5.01.
1,3-Bis(5-benzyloxycarbonyl-3-ethyl-4-methyl-2-pyrrolyl-
methyl)corannuleno[1,2-c]pyrrole (13a). Nitrogen was bubbled
through a stirred mixture of acetoxymethylpyrrole 12a41 (109 mg,
0.346 mmol) and corannulenopyrrole 9 (50.0 mg, 0.173 mmol) in
ethanol (4 mL) and acetic acid (0.5 mL), and the stirred mixture
was then refluxed under nitrogen for 16 h. The mixture was cooled
in an ice bath, and the precipitate was filtered, washed with ethanol,
and dried in vacuo overnight. The tripyrrane (101.5 mg, 0.127
mmol, 73%) was obtained as an off-white solid: mp 238 °C dec; 1H
NMR (500 MHz, CDCl3) δ 0.95 (6H, t, J = 7.5 Hz), 2.31 (6H, s),
2.47 (4H, br), 3.63 (2H, v br), 4.10-4.70 (6H, v br), 6.64 (4H, br d,
J = 7.2 Hz), 6.93 (4H, t, J = 7.6 Hz), 7.06 (2H, t, J = 7.4 Hz), 7.83
(2H, d, J = 8.7 Hz), 7.90 (2H, d, J = 8.7 Hz), 7.96 (2H, d, J = 8.5
Hz), 8.12 (2H, d, J = 8.5 Hz), 10.16 (1H, br s), 11.70 (2H, br s); 1H
NMR (500 MHz, DMSO-d6) δ 0.61 (6H, t, J = 7.5 Hz), 2.14 (6H,
s), 2.16 (4H, q, J = 7.5 Hz), 4.55 (4H, s), 5.27 (4H, s), 7.32 (2H, m),
7.37 (4H, m), 7.43 (4H, m), 7.85 (2H, d, J = 8.7 Hz), 7.90 (2H, d,
J = 8.6 Hz), 7.92 (2H, d, J = 8.7 Hz), 8.10 (2H, d, J = 8.6 Hz),
11.28 (2H, br s), 11.29 (1H, br s); 13C NMR (CDCl3) δ 11.3, 16.0,
17.7, 24.0, 65.4, 117.5, 117.7, 123.9, 124.3, 124.4, 125.6, 126.0,
127.20, 127.23, 127.3, 127.4, 128.2, 128.4, 129.0, 130.7, 132.6, 134.7,
135.4, 136.7, 137.1, 163.4; 13C NMR (DMSO-d6) δ 10.4, 15.1, 16.8,
24.5, 64.6, 116.2, 117.3, 123.4, 123.6, 125.0, 125.9, 126.6, 127.3,
127.4, 127.84, 127.88, 128.0, 128.5, 128.6, 130.3, 131.3, 133.2, 134.4,
135.9, 137.2, 160.8; HRMS (ESI) m/z calcd for C54H45N3O4
799.3410, found 799.3391. Anal. Calcd for C54H45N3O4: C,
81.08; H, 5.67; N, 5.25. Found: C, 81.12; H, 5.55; N, 5.32.
1
672.3254. Anal. Calcd for C48H40N4 /10CHCl3: C, 84.36; H, 5.90;
N, 8.18. Found: C, 84.26; H, 5.84; N, 8.22.
3
[8,12,13,17-Tetraethyl-7,18-dimethylcorannuleno[1,2-b]porphy-
rinato]nickel(II) (15a). A mixture of corannulenoporphyrin 11
(10.0 mg, 0.015 mmol) and Ni(OAc)2 4H2O (9.4 mg) in DMF
3
(10 mL) was stirred under reflux for 1 h. The solution was cooled
to room temperature, diluted with chloroform, and then washed
with water. The organic layer was separated and evaporated
under reduced pressure. The residue was purified by column
chromatography on grade 3 neutral alumina, eluting with
dichloromethane, and the product fraction was evaporated
and then recrystallized from chloroform-methanol to give the
nickel chelate (8.6 mg, 0.012 mmol, 80%) as a purple solid: mp
>300 °C; UV-vis (CHCl3) λmax (log10 ε) 420 (5.14), 528 (3.89),
562 (4.15), 587 nm (4.73); UV-vis (toluene): λmax (log10 ε) 422
(5.15), 524 (sh, 3.93), 565 (4.21), 589 nm (4.82); 1H NMR (500
MHz, CDCl3) δ 1.80 (6H, t, J = 7.6 Hz), 1.85 (6H, t, J = 7.6
Hz), 3.42 (6H, s), 3.88 (4H, q, J = 7.6 Hz), 3.92 (4H, q, J = 7.6
Hz), 7.89 (2H, d, J = 8.5 Hz), 7.95 (2H, d, J = 8.5 Hz), 8.23 (2H,
d, J = 8.5 Hz), 9.17 (2H, d, J = 8.5 Hz), 9.63 (2H, s), 10.63 (2H,
s); 13C NMR (CDCl3) δ 11.7, 17.9, 18.5, 19.9, 20.2, 97.1, 99.8,
126.9, 127.0, 127.2, 127.5, 129.0, 129.6, 131.2, 135.4, 136.0,
136.4, 136.6, 136.9, 137.8, 140.8, 141.5, 142.4, 143.2, 144.0;
EIMS (70 eV) m/z (relative intensity) 732 (11), 731 (23), 730
(50), 729 (48), 728 (100, Mþ), 713 (8.7, [M - CH3]þ), 364.9 (15),
1,3-Bis(5-tert-butoxycarbonyl-3-ethyl-4-methyl-2-pyrrolyl-
methyl)corannuleno[1,2-c]pyrrole (13b). A mixture of acetoxy-
methylpyrrole 12b42 (195 mg, 0.694 mmol) and corannulenopyrrole
9 (100 mg, 0.346 mmol) in 2-propanol (5 mL) and acetic acid
(0.5 mL) was refluxed under nitrogen for 16 h. The mixture was
cooled to room temperature and poured into ice-water. The
resulting precipitate was suction filtered, washed well with water,
and dried overnight in vacuo to give the tripyrrane (218 mg, 0.298
(53) Tardieux, C.; Bolze, F.; Gros, C. P.; Guilard, R. Synthesis 1998, 267–
268.
J. Org. Chem. Vol. 75, No. 8, 2010 2525

Boedigheimer et al.
JOCArticle
364.1 (15, M2þ); HRMS (EI), m/z calcd for C48H38N4Ni
728.2450, found 728.2454.
(2H, d, J = 8.0 Hz), 8.44 (2H, d, J = 8.8 Hz), 9.13 (2H, br d, J =
7.0 Hz), 9.31 (2H, d, J = 8.8 Hz), 11.08 (2H, s), 11.65 (2H, s); 13
C
[8,12,13,17-Tetraethyl-7,18-dimethylcorannuleno[1,2-b]porphy-
rinato]copper(II) (15b). The title compound was prepared by the
foregoing conditions from 11 (10.0 mg, 0.015 mmol) and
copper(II) acetate (11.8 mg). Following chromatography on
grade 3 neutral alumina and recrystallization from chloroform-
methanol, the metal complex (8.7 mg; 0.012 mmol, 80%) was
isolated as a purple solid: mp >300 °C; UV-vis (CHCl3) λmax
(log10 ε) 426 (5.33), 552 (4.03), 595 nm (4.77); EIMS (70 eV) m/z
(relative intensity) 736 (19), 735 (45), 734 (36), 733 (75, Mþ), 718
(6.3, [M - CH3]þ), 368 (24), 367 (27, M2þ); HRMS (EI) m/z
calcd for C48H38N4Cu 733.2392, found 733.2392.
[8,12,13,17-Tetraethyl-7,18-dimethylcorannuleno[1,2-b]porphy-
rinato]zinc(II) (15c). The zinc complex was prepared by the
foregoing conditions from 11 (10.4 mg, 0.0155 mmol) and zinc
acetate (11.8 mg). Following chromatography on grade 3 neu-
tral alumina and recrystallization from chloroform-methanol,
the zinc derivative (9.1 mg; 0.0124 mmol, 80%) was isolated as a
purple solid: mp >300 °C; UV-vis (CHCl3) λmax (log10 ε) 431
(5.23), 554 (4.01), 601 (4.65), 780 (3.40), 854 nm (3.48); UV-vis
(1% pyrrolidine-CHCl3) λmax (log10 ε) 383 (4.51), 420 (sh, 4.72),
446 (5.32), 562 (4.14), 610 (4.71), 669 nm (3.80); 1H NMR (500
MHz, CDCl3) δ 1.82-1.95 (12H, br), 3.32-3.70 (6H, br),
3.81-4.21 (8H, br), 7.83 (2H, br), 7.94 (2H, br), 8.21 (2H, br),
9.26 (2H, br), 9.67 (2H, v br), 10.53 (2H, v br); 1H NMR (500
MHz, pyrrolidine-CDCl3) δ 1.80 (6H, t, J = 7.7 Hz), 1.93 (6H, t,
J = 7.7 Hz), 3.56 (6H, s), 3.97 (4H, q, J = 7.7 Hz), 4.18 (4H, q,
J = 7.7 Hz), 7.82 (2H, d, J = 8.6 Hz), 7.90 (2H, d, J = 8.6 Hz),
8.28 (2H, d, J = 8.6 Hz), 9.55 (2H, d, J = 8.6 Hz), 9.90 (2H, s),
11.07 (2H, s); 13C NMR (pyrrolidine-CDCl3) δ 18.1, 18.7, 19.8,
20.2, 96.8, 99.6, 126.9, 127.0, 127.26, 127.33, 128.2, 128.7, 129.3,
131.0, 135.4, 135.6, 136.1, 136.6, 137.2, 142.5, 143.3, 143.8, 147.8,
148.7, 149.6; EIMS (70 eV) m/z (relative intensity) 739 (18), 738
(43), 737 (37), 736 (68), 735 (59), 734 (100, Mþ), 733 (23), 719 (12,
[M - CH3]þ), 369 (15), 368 (21), 367 (22, M2þ); HRMS (EI) m/z
calcd for C48H38N4Zn 734.2375, found 734.2378.
NMR (TFA-CDCl3) δ 12.1, 16.8, 20.6, 99.4, 101.1, 126.3, 127.0,
127.6, 128.1, 129.1, 129.3, 130.7, 131.0, 131.1, 131.3, 131.4,
131.9, 133.9, 135.5, 135.9, 136.7, 137.2, 138.6, 139.1, 139.5,
143.0, 143.3, 143.9, 144.5; HRMS (FAB) m/z calcd for
C54H36N4þH 741.3016, Found 741.3018.
Crystallographic Experimental Details of 15a. X-ray quality
crystals of 15a were obtained by vapor diffusion of hexanes into
a CDCl3 solution. The crystals were quickly suspended in
mineral oil at ambient temperature, and a suitable crystal was
selected. A mineral oil coated red block thereby obtained of
approximate dimensions 0.15 ꢀ 0.13 ꢀ 0.11 mm3 was mounted
and transferred to a CCD equipped diffractometer. The X-ray
diffraction data were collected at -173 °C using Mo KR (λ =
˚
0.71073 A) radiation. Data collection and cell refinement were
performed using SMART and SAINTþ, respectively.54 The
unit cell parameters were obtained from a least-squares refine-
ment of 1026 centered reflections. Compound 15a was found to
crystallize as the chloroform solvate in the monoclinic crystal
system with the following unit cell parameters: a = 32.288(11)
˚
˚
˚
A, b = 13.621(4) A, c = 20.774(7) A, β = 122.411(6)°, Z = 8.
The systematic absences indicated the space group to be Cc
(no. 9) or C2/c (no. 15);55 the latter was chosen on the basis of
centricity and led to a quality solution. A total of 19 337
reflections were collected, of which 7237 were unique, and
3684 were observed Fo > 2σ(Fo2). Limiting indicies were as
2
follows: -39 e h e 38, -16 e k e 11, -25 e l e 25. Data
reduction was accomplished using SAINT.54 The data were
corrected for absorption using the SADABS procedure.54
Solution and data analysis were performed using the WinGX
software package.56 The structure of 15a was solved by charge
flipping methods using the program SUPERFLIP,57 and the
refinement was completed using the program SHELX-97.58 All
non-hydrogen atoms were refined anisotropically. All H atoms
were included in the refinement in the riding-model approxima-
˚
tion (C-H = 0.95, 0.98, 0.99, and 1.00 A for Ar-H, CH3, CH2,
7,18-Diethyl-8,17-dimethylacenaphtho[1,2-b]corannuleno[1,2-
l]porphyrin (16). Tripyrrane 13b (106 mg, 0.145) was stirred with
TFA (2 mL) for 10 min under nitrogen. The mixture was diluted
with dichloromethane (38 mL), followed by the addition of
acenaphthopyrrole dialdehyde 1722c (35.7 mg, 0.144 mmol), and
the resulting solution was stirred for 3 h. The mixture was
washed with water, and the aqueous layer was back-extracted
with chloroform. The combined organic solutions were shaken
vigorously with 0.1% aqueous ferric chloride solution for
10 min, and the organic phase was separated and washed with
water, saturated sodium bicarbonate solution, and water. The
solvent was removed under reduced pressure, and the residue
was purified by column chromatography on grade 3 neutral
alumina eluting initially with dichloromethane, then with
chloroform and finally with 10% methanol-chloroform. The
porphyrin-containing fractions were rechromatographed on
silica, eluting with the same sequence of solvents, and the
product was collected as a dark green band. Recrystallization
from chloroform-methanol gave the acenaphthoporphyrin
(35.6 mg, 0.048 mmol, 33%) as shiny purple crystals: mp
>300 °C; UV-vis (1% Et3N-CHCl3) λmax (log10 ε) 410 (sh,
4.56), 438 (5.00), 540 (3.70), 564 (sh, 3.90), 587 (sh, 4.39), 601 (sh,
4.30), 618 (4.54), 683 nm (3.67); UV-vis (1% TFA-CHCl3) λmax
(log10 ε) 379 (4.39), 449 (5.00), 470 (5.25), 554 (3.78), 579 (4.06),
and CH; Uiso(H) = 1.2Ueq(C) except for methyl groups, where
Uiso(H) = 1.5Ueq(C)). Full-matrix least-squares refinement on
F2 led to convergence, (Δ/σ)max = 0.001, (Δ/σ)mean = 0.0000,
with R1 = 0.0791 and wR2 = 0.1424 for 3684 data with Fo >
2
2σ(Fo2) using 0 restraints and 516 parameters. A final difference
Fourier synthesis showed features in the range of ΔFmax = 0.524
-
3
-
3
˚
˚
e /A to ΔFmin = -0.825 e /A , which were deemed of no
chemical significance. The structure validation program
Mogul59 indicated that most bond distances and angles were
within expected norms. The two organic bond distances and 19
angles outside “normal” ranges appear to be reasonable and
explainable by the nature of the macrocycle. All involved the
corannulene moiety, and in fact, these parameters were similarly
flagged as unusual for other corannulene derivatives.60-62
Molecular diagrams were generated using ORTEP-363 and
POV-Ray.64
(54) Bruker, APEX2 v2008.2-4, Bruker AXS Inc.: Madison, WI, 2008.
(55) McArdle, P. J. Appl. Crystallogr. 1996, 29, 306.
(56) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837–838.
(57) Palatinus, L.; Chapuis, G. J. Appl. Crystallogr. 2007, 40, 786–790.
(58) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112–122.
(59) Bruno, I. J.; Cole, J. C.; Kessler, M.; Luo, J.; Motherwell, W. D. S.;
Purkis, L. H.; Smith, B. R.; Taylor, R.; Cooper, R. I.; Harris, S. E.; Orpen,
A. G. J. Chem. Inf. Comput. Sci. 2004, 44, 2133–2144.
(60) Morita, Y.; Ueda, A.; Nishida, S.; Fukui, K.; Ise, T.; Shiomi, D.;
Sato, K.; Takui, T.; Nakasuji, K. Angew. Chem., Int. Ed. 2008, 47, 2035–
2038.
(61) Sygula, A.; Folsom, H. E.; Sygula, R.; Abdourazak, A. H.; Marcinow,
Z.; Fronczek, F. R.; Rabideau, P. W. Chem. Commun. 1994, 2571–2572.
(62) Sygula, A.; Fronczek, F. R.; Sygula, R.; Rabideau, P. W.; Olmstead,
M. M. J. Am. Chem. Soc. 2007, 129, 3842–3843.
(63) Farrugia, L. J. J. Appl. Crystallogr. 1997, 30, 565.
(64) Persistence of Vision Team, 2006, www.povray.org.
1
598 (4.02), 626 (sh, 3.92), 656 nm (4.84); H NMR (500 MHz,
CDCl3, 50 °C, aromatic region only) δ 7.85-8.05 (8H, m), 8.37
(2H, d, J = 8.6 Hz), 8.85 (2H, d, J = 7.5 Hz), 9.52 (2H, d, J =
8.6 Hz), 10.37 (2H, s), 11.14 (2H, s); 1H NMR (500 MHz, TFA-
CDCl3) δ -3.04 (2H, br s), -2.50 (2H, v br, 1.92 (6H, br t, J =
7.7 Hz), 3.78 (6H, s), 4.33 (4H, q, J = 7.7 Hz), 7.99-8.03 (4H,
AB quartet, J = 8.7 Hz), 8.11 (2H, dd, J = 7.0, 8.0 Hz), 8.30
2526 J. Org. Chem. Vol. 75, No. 8, 2010

Boedigheimer et al.
JOCArticle
Acknowledgment. This work was supported by the Na-
tional Science Foundation under Grant Nos. CHE-0616555
and CHE-0911699 (to T.D.L.), and CHE-0348158 and
CHE-0725294 (to G.M.F.), and the Petroleum Research
Fund, administered by the American Chemical Society.
Funding for a 500 MHz NMR spectrometer was also
provided by the National Science Foundation under Grant
No. CHE-0722385. The authors thank Youngstown State
University Structure & Chemical Instrumentation Facility’s
Matthias Zeller for X-ray data collection. The diffractometer
was funded by NSF Grant 0087210, Ohio Board of Regents
Grant CAP-491, and YSU. H.B. also thanks J.S. Siegel and
C. Jones at the University of California;San Diego for
helpful advice on the synthesis of a precursor to corannulene.
Supporting Information Available: ORTEP-3 and POV-
Ray figures for the X-ray crystal structure of 15a, and selected
UV-vis spectra, proton, NOE difference, COSY, HMQC,
HMBC, DEPT-135 and carbon-13 NMR spectra, and MS data
are provided. This material is available free of charge via the
Internet at http://pubs.acs.org.
J. Org. Chem. Vol. 75, No. 8, 2010 2527