Synthesis of benziporphyrins and heterobenziporphyrins and an assessment of the diatropic characteristics of the protonated species

Article abstract of DOI:10.1021/jo401365p

Benzitripyrranes were prepared by reacting diphenyl-substituted benzenedicarbinols with excess pyrrole in the presence of BF₃· Et₂O. These dipyrrolic compounds underwent acid-catalyzed condensations with a pyrrole dialdehyde to afford good yields of diphenylbenziporphyrins, and further reaction with palladium(II) acetate gave stable organometallic derivatives. The X-ray crystal structure of a palladium(II) benziporphyrin showed that the system deviates significantly from planarity. Although the benzitripyrranes failed to give stable macrocyclic products with furan or thiophene dialdehydes, they afforded tetraphenyl heterobenziporphyrins upon reaction with diphenyl-substituted furan- or thiophenedicarbinols and BF₃·Et₂O. Benziporphyrins and their heteroanalogues showed no indication of a diamagnetic ring current by proton NMR spectroscopy, but addition of TFA gave rise to the formation of weakly diatropic dications.

Full text of DOI:10.1021/jo401365p

Article
pubs.acs.org/joc
Synthesis of Benziporphyrins and Heterobenziporphyrins and an
Assessment of the Diatropic Characteristics of the Protonated
Species
Timothy D. Lash,* Ashley M. Toney, Kylie M. Castans, and Gregory M. Ferrence
Department of Chemistry, Illinois State University, Normal, Illinois 61790-4160, United States
S
* Supporting Information
ABSTRACT: Benzitripyrranes were prepared by reacting
diphenyl-substituted benzenedicarbinols with excess pyrrole
in the presence of BF3·Et2O. These dipyrrolic compounds
underwent acid-catalyzed condensations with a pyrrole
dialdehyde to afford good yields of diphenylbenziporphyrins,
and further reaction with palladium(II) acetate gave stable
organometallic derivatives. The X-ray crystal structure of a
palladium(II) benziporphyrin showed that the system deviates
significantly from planarity. Although the benzitripyrranes failed to give stable macrocyclic products with furan or thiophene
dialdehydes, they afforded tetraphenyl heterobenziporphyrins upon reaction with diphenyl-substituted furan- or
thiophenedicarbinols and BF3·Et2O. Benziporphyrins and their heteroanalogues showed no indication of a diamagnetic ring
current by proton NMR spectroscopy, but addition of TFA gave rise to the formation of weakly diatropic dications.
alternative route to meso-tetraarylbenziporphyrins 3 was
subsequently developed wherein a dicarbinol 4 is reacted
with pyrrole and benzaldehyde in the presence of boron
trifluoride etherate, followed by oxidation with DDQ (Scheme
2).5 Diverse benziporphyrin structures have been prepared by
INTRODUCTION
■
Benziporphyrins (e.g., 1a) are a family of porphyrin analogues
in which one of the pyrrole units has been replaced by a
benzene ring.1,2 This carbaporphyrinoid system was originally
prepared by the acid-catalyzed reaction of isophthalaldehyde
with a tripyrrane 2 (Scheme 1) followed by oxidation with an
electron-deficient quinone (chloranil or DDQ).1,3,4 An
Scheme 2
Scheme 1
both synthetic approaches,1,4−9 including dimethoxybenzipor-
phyrins 1b, 1c, 3c, and 3d6,7 and tert-butyl-substituted
benziporphyrins 3b.8 Benziporphyrins such as 1a do not
exhibit macrocyclic ring currents as determined by proton
NMR spectroscopy because of the presence of the cross-
conjugated benzene ring,1,4 but the introduction of electron-
donating methoxy groups gives rise to a degree of diatropic
character.6,7 When a hydroxy group is introduced at the 2-
position, a tautomerization occurs to give the fully aromatic
oxybenziporphyrin system 5 (Scheme 1).1,4 In this case, the
macrocyclic ring current leads to a resonance for the internal
CH near −7 ppm. Further oxidized aromatic benziporphyrin
Received: June 22, 2013
Published: August 14, 2013
© 2013 American Chemical Society
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systems have also been described.6,10 The coordination
chemistry of benziporphyrins has been investigated in detail,
and stable organometallic derivatives have also been
isolated.5,7,8,10−12 Furthermore, a dihydrobenziporphyrin has
shown promise as a fluorescent zinc cation detector.13 The
metalation of related phthalocyanine analogues has also been
investigated.15
types of heteroporphyrinoids were considered to be worthwhile
targets for investigation. In addition, these porphyrinoids might
also provide experimental support for the 18-π-electron model
for aromaticity in borderline aromatic systems.17 In this paper,
we report the first syntheses of oxa- and thiabenziporphyrins
and the preparation of novel meso-diphenyl-substituted
benziporphyrins.26
Addition of TFA to benziporphyrin 1a affords the
corresponding dication 1aH2 (Scheme 3).1 Even though 1a
2+
RESULTS AND DISCUSSION
■
The synthesis of heterobenziporphyrins was attempted using
the “3 + 1” variant of the MacDonald condensation (Scheme
4). In order to carry out these syntheses, benzitripyrranes 8
Scheme 3
Scheme 4
showed no indication of a macrocyclic ring current, the proton
NMR spectrum of 1a in TFA/CDCl3 showed that the internal
CH resonance was shifted upfield to 5 ppm.1,14 This effect was
greatly magnified for dimethoxybenziporphyrin dication
1bH22+, for which the CH resonance was shifted further
upfield to −0.68 ppm.6 The 3-methyl-2,4-dimethoxybenzipor-
2+
phyrin dication 1cH2 exhibited an intermediate effect, with
the resonance for the internal CH unit showing up at +0.69
ppm.6 The presence of a macrocyclic ring current in 1aH22+ was
attributed to a resonance contributor 6a that possesses an 18-π-
electron delocalization pathway.6 Resonance contributors for
2+
1bH2 with this type of delocalization pathway are further
stabilized by the presence of the methoxy units, which can give
rise to canonical forms such as 7b. However, this type of
interaction is less favorable for 1c because of the presence of a
methyl substituent between the two methoxy groups, as the
resonance interaction relies upon the OMe groups lying
coplanar with the benzene ring, which is inhibited as a result of
steric crowding.6 Similar observations have been made for
tetraarylbenziporphyrins 3.7,8 These explanations rely upon the
diaza[18]annulene model for porphyrinoid aromaticity,16,17 but
this viewpoint has been brought into question.18,19 Specifically,
theoretical studies have indicated that the aromatic character of
porphyrins is primarily due to the six-π-electron subunits rather
than the presence of 18-π-electron pathways.18,19 Nevertheless,
the diaza[18]annulene model still provides a superior
explanation for the aromatic characteristics of many porphyr-
inoid systems.17,20 We noted that no examples of hetero-
benziporphyrins had been prepared previously, although
heteroanalogues of many other carbaporphyrinoid systems are
known,21−25 and we speculated that similar borderline aromatic
properties might be observed for these systems as well. In view
of the high level of interest in benziporphyrin chemistry, these
were required as key intermediates. Structures of this type have
previously been used in the preparation of porphyrin analogues
such as pyriporphyrins27 and p-benziporphyrins.28 Benzenedi-
carbinols 9 are easily prepared in multigram quantities from
isophthalic acids 10.10 Reaction of 9 with excess pyrrole and
catalytic boron trifluoride etherate in refluxing 1,2-dichloro-
ethane afforded the required benzitripyrranes 8. Following
column chromatography on silica gel, intermediates 8 were
isolated with approximately 95% purity in 66−70% yield. In
order to assess the utility of these intermediates, 8a was reacted
with pyrroledialdehyde 11 in the presence of TFA in
dichloromethane. After 2 h, DDQ was added to oxidize the
initially formed dihydroporphyrinoid, and following extraction
and purification by column chromatography on grade-3
alumina, benziporphyrin 12a was isolated in 50% yield.
Dialdehyde 11 similarly reacted with 8b to give the tert-butyl-
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substituted benziporphyrin 12b in 58% yield. The benzipor-
phyrins eluted from the columns in pure form, but
recrystallization was not possible because of the highly soluble
nature of these porphyrinoids in a wide range of organic
solvents, including hexane and methanol.
Benziporphyrins 12 have a unique substitution pattern and
may be considered to be hybrids between etio-type
benziporphyrins 1 and meso-tetrasubstituted benziporphyrins
3. The UV−vis spectrum of 12b exhibited a Soret-like band at
403 nm and a broad absorption centered at 656 nm (Figure 1).
The proton NMR spectra of 12a and 12b showed no
indication of a macrocyclic ring current. For instance, the
proton NMR spectrum of 12b in CDCl3 showed the outer
benzene protons (2,4-H) at 7.04 ppm, while the internal CH
appeared at 7.15 ppm (Figure 2). Furthermore, the bridging
methine protons (11,16-H) were located at 6.32 ppm, a value
that falls into the olefinic region. In the presence of TFA,
however, the corresponding dication 12bH22+ again showed the
presence of a recognizable diatropic ring current, as the internal
CH shifted upfield to 5.05 ppm, while the external meso-
protons (11,16-H) moved downfield to 7.03 ppm (Figure 2).
2+
The pyrrolic protons of 12bH2 gave rise to two doublets of
doublets at 7.51 and 7.91 ppm, compared with values of 6.96
and 7.31 ppm for these resonances in the spectrum of the free
base. Although the presence of a 2+ charge on the system
contributes to the downfield shifts, the data are consistent with
the emergence of weak diatropic character over the macrocycle
as had been noted for related structures.1,6,8,14 The dication
derived from 12a in TFA/CDCl3 showed a smaller ring-current
effect, as the proton NMR spectrum exhibited a resonance for
22-H at 5.65 ppm while the meso-protons (11,16-H) gave rise
to a 2H singlet at 6.91 ppm. It has been suggested that the
electron-donating tert-butyl group helps to stabilize resonance
contributors such as 7 that favor the 18-π-electron delocaliza-
tion pathway.8
Figure 1. UV−vis spectra of 12b in 1% Et3N/CH2Cl2 (free base, blue
line) and 1% TFA/CH2Cl2 (dication 12bH22+, red line).
Benziporphyrins 12a and 12b were also characterized by 13
C
NMR spectroscopy and mass spectrometry. The 13C NMR
spectra of 12a and 12b confirmed the presence of a plane of
symmetry in these macrocycles. The spectrum of 12b in CDCl3
gave a resonance for the meso-CH bridges (11,16-C) at 95.9
ppm, while the internal carbon (22-C) was identified at 109.4
2+
In 1% TFA/CH2Cl2, a dicationic species 12bH2 (Scheme 4)
was generated that gave a strong absorption at 447 nm (ε > 105
M−1 cm−1) and a broad band at 789 nm (Figure 1).
Spectrophotometric titration showed the emergence of a peak
at 880 nm with 1 equiv of TFA that was attributed to the
monoprotonated structure 12bH+, but this species appeared to
be in equilibrium with 12bH22+. Similar results were obtained
for benziporphyrin 12a.
2+
ppm. In TFA/CDCl3, the related dication 12bH2 gave a
similar value for the meso-C resonance at 96.2 ppm, but the 22-
C signal was shifted upfield to 96.8 ppm. This compares to
Figure 2. Proton NMR spectra (500 MHz) of tert-butyl-substituted benziporphyrin 12b in CDCl3 (free base, upper spectrum) and TFA/CDCl3
(dication 12bH22+, lower spectrum).
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2+
values of 96.3 and 99.7 ppm, respectively, for dication 12aH2
showed the meso-CH peak at 99.3 ppm, while 13b gave this
resonance at 99.2 ppm.
The X-ray crystal structure of palladium complex 13b (Figure
4) both confirms the presence of a benziporphyrin macrocycle
in TFA/CDCl3. Benziporphyrins have previously been reported
to give a cluster of peaks in the molecular-ion region for
electron impact mass spectrometry,1,3 and this was also the case
for 12a and 12b. Interestingly, for 12a the [M + 2H]+ peak at
m/z 531 predominated. However, the electrospray ionization
mass spectrum for 12a gave the expected [M + H]+ signal at m/
z 530 as the base peak.
As benziporphyrins have been shown to form organometallic
derivatives under mild conditions,7,8,11,14 the preparation of
palladium complexes from porphyrinoids 12 was investigated
(Scheme 5). Benziporphyrin 12b was heated with palladium-
Scheme 5
Figure 4. ORTEP-3 drawing (50% probability level, H atoms omitted
for clarity) of palladium(II) complex 13b. Selected bond lengths: C1−
C2, 1.414(4); C2−C3, 1.385(4); C3−C4, 1.369(4); C4−C5,
1.418(4); C5−C22, 1.426(4); C22−C1, 1.426(4); C5−C6,
1.451(4); C6−C7, 1.364(4); C7−C8, 1.451(4); C7−N23, 1.391(3);
C8−C9, 1.335(4); C9−C10, 1.447(4); C10−N23, 1.356(3); C10−
C11, 1.397(4); C11−C12, 1.367(4); C12−N24, 1.369(3); C12−C13,
1.465(3); C13−C14, 1.354(4); C14−C15, 1.464(3); C15−N24,
1.368(3); C15−C16, 1.364(4); C16−C17, 1.391(4); C17−N25,
1.366(3); C17−C18, 1.439(4); C18−C19, 1.3394; C19−C20,
1.450(4); C20−N25, 1.400(3); C20−C21, 1.364(3); C21−C1,
1.453(4).
(II) acetate in acetonitrile and gave the corresponding
palladium(II) derivative 13b in 74% yield. Similarly, 12a
reacted with Pd(OAc)2 in refluxing acetonitrile/chloroform to
give 13a in 73% yield. The new organometallic compounds
were stable and easily purified by column chromatography on
grade-3 basic alumina. The UV−vis spectrum of 13b gave a
Soret-like band at 425 nm (ε = 7.74 × 104 M−1 cm−1) and a
series of minor absorptions between 500 and 850 nm (Figure
3). Although the UV−vis spectrum of 13a was very similar, the
and demonstrates that the macrocycle deviates significantly
from planarity, as evidenced by the rms distance of the
framework atoms from the coordination environment plane
defined by Pd, C22, N23, N24, and N25 (0.356 Å). Of the 25
framework atoms, 10 deviated from this plane by more than
0.25 Å. The macrocycle is somewhat saddled with the C3-
attached tert-butyl group at the horn. So defined, the framework
arene ring is tilted 19.16(6)° relative to the coordination
environment plane with C2 [0.794(3) Å], C3 [0.997(3) Å],
and C4 [0.571(3) Å] rising above the plane. The pyrrolic rings
adjacent to the framework arene ring are tilted 12.57(9)° and
9.10(8)° relative to the coordination environment plane with
C8 [0.538(3) Å], C9 [0.339(3) Å], C18 [0.378(3) Å], and C19
[0.414(3) Å] falling below the plane. The pyrrolic ring opposite
to the framework arene ring is tilted 5.73(8)° relative to the
coordination environment plane with C13 [0.241(3) Å] and
C14 [0.105(3) Å] rising a little above the plane. The larger tilt
of the arene ring is attributable to steric repulsion between the
C2 and C4 H atoms and the meso-phenyl substituents. The
phenyl groups are in fact canted 57.61(9)° and 45.61(8)°
relative to the coordination environment plane. The structure
exhibits framework bond distances consistent with a generally
localized π-bonding model. The phenyl substituents attached to
the meso-carbons have π systems separated from that of the
main macrocycle. The metal coordination environment of 13b
is essentially the typical four-coordinate square-planar geometry
characteristic of Pd(II) complexes. This is similar to related
Figure 3. UV−vis spectrum of palladium(II) benziporphyrin 13b in
CH2Cl2.
major band underwent a small blue shift to 423 nm. The proton
NMR spectrum of 13b in CDCl3 showed the pyrrolic protons
as two 2H doublets at 7.20 and 7.37 ppm, while the meso-
protons appeared as a 2H singlet at 7.32 ppm. These values are
shifted significantly downfield from those noted for the free-
base form of 12b, possibly indicating the presence of a small
macrocyclic ring current. The corresponding resonances for
13a appeared at 7.15, 7.33, and 7.27 ppm, respectively, which
are slightly upfield from those of 13b, again indicating that the
tert-butyl group enhances the weakly diatropic character of this
system. The 13C NMR spectra of 13a and 13b demonstrated
that the macrocycle had retained a plane of symmetry; 13a
relatively planar palladium(II) N-confused porphyrins,29−31
a
similar palladium(II) pyrazoloporphyrin,32 and a closely related
palladium(II) naphthiporphyrin.14 The Pd−C distance of
2.031(2) Å in 13b is comparable to the distance of 2.055(4)
Å observed in a palladium(II) naphthiporphyrin and is
consistent with the distances of 2.00(5) Å observed for nearly
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3000 crystallographically measured complexes containing Pd−
C(phenyl) σ bonds.33
Given these successes, it was anticipated that oxa- and
thiabenziporphyrins 14 could be synthesized by a similar
approach (Scheme 4). However, reaction of furan- or
thiophenedialdehyde 15 with benzitripyrranes 8 failed to give
more than trace amounts of the benziporphyrin products,
although an unstable blue fraction corresponding to a
benziphlorin was noted in the furan case. At this stage of the
work, an alternative route to oxa- and thiabenziporphyrins was
considered. In principle, reactions of 8 with thiophenedicarbi-
nol 16a and furandicarbinol 16b could be used to prepare meso-
tetraphenylheterobenziporphyrins 17 (Scheme 6). Benzitripyr-
Figure 5. UV−vis spectra of thiabenziporphyrin 17b in 1% Et3N/
Scheme 6
2+
CH2Cl2 (free base, blue line) and 1% TFA/CH2Cl2 (dication 17bH2
,
red line).
resulted in the appearance of a broad peak near 800 nm that
was attributed to monocations 17H+, but as was the case for
benziporphyrins 12a and 12b, these appeared to be in
2+
equilibrium with the dicationic species 17H2
.
The proton NMR spectra of 17a and 17b were consistent
with a system that lacks macrocyclic aromatic character. For
instance, in the proton NMR spectrum of 17b, the internal 22-
H gave a 1H triplet (J = 1.5 Hz) at 7.04 ppm, while the outer
benzene protons (2,4-H) appeared as a 2H doublet at 7.10
2+
ppm. However, in TFA/CDCl3, the resulting dication 17bH2
exhibited a degree of diatropic character (Figure 6), as the
rane 8a was reacted with 16a in the presence of boron
trifluoride etherate to initially generate benziporphyrinogen
18a. This species was not isolated but instead was immediately
oxidized with DDQ to afford thiabenziporphyrin 17a. Column
chromatography on grade-2 alumina gave a dark-green-colored
fraction, and following evaporation of the solvent, 17a was
isolated in 38% yield. The tert-butyl-substituted tripyrrane
analogue 8b similarly reacted with 16a to give thiabenzipor-
phyrin 17b in 30% yield.
Figure 6. Proton NMR spectrum (500 MHz) of thiabenziporphyrin
dication 17bH2 in TFA/CDCl3. The internal CH shows up as a
triplet at 4.93 ppm.
2+
The UV−vis spectrum of 17b in 1% Et3N/CH2Cl2 gave a
moderately strong band at 416 nm and a broad absorption at
643 nm (Figure 5). Porphyrinoid 17a gave a similar UV−vis
spectrum, but the Soret-like band was hypsochromically shifted
to 411 nm. Addition of TFA to the solution of 17b afforded a
diprotonated species that showed a strong absorption at 477
nm and broad long-wavelength absorptions at 703 and 880 nm
(Figure 5). Again, the UV−vis spectrum of 17aH2 showed a
slightly blue-shifted Soret-like band at 475 nm. Addition of 1
equiv of TFA to a solution of 17a or 17b in dichloromethane
internal CH appeared as an upfield triplet (J = 1.5 Hz) at 4.93
ppm while the external benzene hydrogens (2,4-H) gave a 2H
doublet further downfield at 7.35 ppm. The pyrrolic protons
were also shifted further downfield to give resonances at 7.23
and 7.97 ppm, while the thiophene protons gave a singlet at
2+
8.00 ppm. All of these shifts were slightly reduced for 17aH2
2+
in TFA/CDCl3, and the internal CH showed up at 5.29 ppm in
this case. These data indicate that the dications derived from
thiabenziporphyrins, like those derived from benziporphyrins,
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possess a significant degree of diatropic character and that the
presence of the tert-butyl substituent again enhances this effect.
Both the proton and 13C NMR spectra of 17a and 17b
demonstrated the presence of a plane of symmetry in these ring
systems. For spectra run in CDCl3, the internal C resonances of
17a and 17b appeared at 113.0 and 110.8 ppm, respectively,
but in TFA/CDCl3 the peaks for the corresponding dications
shifted upfield to values of 100.2 and 98.1 ppm. In this respect,
the results resembled those obtained for benziporphyrins 12a
and 12b. In addition, the electron impact mass spectra of
thiabenziporphyrins 17a and 17b gave a cluster of peaks in the
molecular-ion region, as observed for benziporphyrins 12.
Benzitripyrranes 8a and 8b also reacted with furandicarbinol
16b to give the related oxabenziporphyrins 17c and 17d,
respectively (Scheme 6). However, difficulties were encoun-
tered in purifying these porphyrinoids. Protonation of the
system occurred readily, and the best results were obtained
when the structures were deliberately protonated prior to
purification. The oxidation was carried out with DDQ in the
presence of TFA. The reaction solutions were washed with
sodium bicarbonate solution and then with 10% hydrochloric
acid, and the solvent was removed on a rotary evaporator. The
protonated mixture was run through a silica column, and the
products were obtained in a partially protonated form in 28%
yield. The isolated porphyrinoids appeared to be primarily in
the monoprotonated form. The UV−vis spectrum of 17d in
dichloromethane gave a series of bands at 352, 381, 452, and
806 nm with a stronger absorption at 265 nm, but in 5% E3N/
CH2Cl2 only broad absorptions were noted at 385 and 637 nm
(Figure 7). The latter spectrum was attributed to the free-base
butyl group in 17d is again responsible for a small increase in
the diatropicity. The chemical shifts for tetraphenylbenzipor-
2+
phyrin dications 3H2 in TFA/CDCl3 have been reported
previously.8 In order to compare the diatropic characters of the
benziporphyrins and heterobenziporphyrins, only resonances
that are not directly affected by the heteroatom substitution
were considered. For this discussion, the external pyrrole
protons at positions 9,18 and 8,19 were examined, as well as the
internal 22-H (Table 1). On the basis of the downfield shifts for
Table 1. Selected Chemical Shifts (ppm) for Benziporphyrin
and Heterobenziporphyrin Dications in TFA/CDCl3
22-H
9,18-H
8,19-H
a
a
2+
2+
3aH2
5.65
5.05
5.29
4.93
5.65
5.27
7.08
7.12
7.22
7.23
6.98
7.81
7.79
7.96
7.97
7.97
6.98
7.81
3bH2
2+
17aH2
17bH2
2+
2+
17cH2
2+
17dH2
a
Data taken from ref 8.
the external pyrrolic protons and the upfield shifts for 22-H, the
thiabenziporphyrin dications showed the largest diatropic ring
currents while the oxabenziporphyrins showed the smallest
effects. For each system, the presence of a tert-butyl group
significantly increased the diatropicity for the macrocycle. The
2+
2+
electronegative oxygen atom in 17cH2 and 17dH2 is less
effective in facilitating charge delocalization, which provides an
explanation for the reduced shifts observed for these dications.
On the other hand, sulfur enhances the aromatic character of
thiophene compared with pyrrole or furan and presumably
exerts a similar effect for 17aH22+ and 17bH22+. The 13C NMR
spectra of oxabenziporphyrin dications 17cH22+ and 17dH22+ in
TFA/CDCl3 confirmed that these structures also possess a
plane of symmetry and again showed the internal C resonance
(22-C) at relatively upfield values of 104.4 and 101.7 ppm,
respectively.
Figure 7. UV−vis spectra of oxabenziporphyrin 17d in 5% Et3N/
CH2Cl2 (free base, red line), CH2Cl2 (blue line), and 1% TFA/
CH2Cl2 (dication 17dH22+, purple line).
CONCLUSION
■
Tripyrrane analogues have been prepared by reacting
benzenedicarbinols with excess pyrrole in the presence of
boron trifluoride etherate, and these intermediates were used to
prepare diphenylbenziporphyrins by carrying out acid-catalyzed
condensations with a pyrroledialdehyde. Protonation with TFA
afforded dicationic species that showed significant, albeit
relatively small, diamagnetic ring currents. These novel
benziporphyrins also smoothly reacted with palladium(II)
acetate to give the related organometallic derivatives, and a
palladium(II) complex was characterized by X-ray crystallog-
raphy. Attempts to react benzitripyrranes with furan- or
thiophenedialdehyde failed to give macrocyclic products.
However, the benzitripyrranes did condense with furan- or
thiophenedicarbinols in the presence of boron trifluoride
etherate to give the first examples of tetraphenyl-substituted
oxa- and thiabenziporphyrins. Diprotonation of heterobenzi-
2+
form of the macrocycle. In 1% TFA/CH2Cl2, 17dH2 gave a
completely different spectrum with a strong Soret-like band at
456 nm and weaker absorptions at 352, 384, and 768 nm
(Figure 7). Similar results were obtained for oxabenziporphyrin
17c.
The proton NMR spectra of the diprotonated oxabenzipor-
phyrins were obtained in TFA/CDCl3. The tert-butyl-
substituted structure 17d showed the presence of a 1H triplet
(J = 1.5 Hz) corresponding to the internal CH at 5.30 ppm.
The pyrrolic protons produced two doublets of doublets at 7.00
and 7.83 ppm, while the furan protons appeared as a 2H singlet
at 7.50 ppm. Oxabenziporphyrin 17c showed the internal CH
at 5.65 ppm, the pyrrolic protons at 6.98 and 7.81 ppm, and the
furan protons at 7.48 ppm. These data indicate that the tert-
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gave the benziporphyrin (56.8 mg, 0.11 mmol, 50%) as a dark-green
solid. Mp: >300 °C. UV−vis (1% Et3N/CH2Cl2) λmax (log ε): 314
(4.55), 399 (4.87), 663 (3.99). UV−vis (1% TFA/CH2Cl2) λmax (log
porphyrins also gave rise to dications with diatropic character.
The shifts observed for oxabenziporphyrins were slightly
smaller than those observed for structurally similar benzipor-
phyrins, but thiabenziporphyrin dications exhibited enhanced
diatropicity. These results give further insights into the
aromatic characteristics of porphyrinoid systems and provide
access to hitherto-unknown heterobenziporphyrin structures.
1
ε): 303 (4.42), 347 (4.32), 446 (5.14), 712 (sh, 4.06), 786 (4.31). H
NMR (500 MHz, CDCl3): δ 1.28 (6H, t, J = 7.6 Hz, 2 × CH2CH3),
2.70 (4H, q, J = 7.6 Hz, 13,14-CH2), 6.28 (2H, s, 11,16-H), 6.94 (2H,
d, J = 4.7 Hz, 9,18-H), 6.99 (2H, dd, J = 1.8, 7.8 Hz, 2,4-H), 7.24 (2H,
t, J = 7.8 Hz, 3-H), 7.28 (2H, d, J = 4.7 Hz, 8,19-H), 7.41−7.48 (11H,
m, 22-H + 2 × Ph), 9.99 (1H, br s, NH). 1H NMR (500 MHz, TFA/
CDCl3): δ 1.29 (6H, t, J = 7.6 Hz, 2 × CH2CH3), 2.84 (4H, q, J = 7.6
Hz, 13,14-CH2), 5.79 (1H, br t, J = 1.7 Hz, 22-H), 6.91 (2H, s, 11,16-
H), 7.14 (2H, dd, J = 1.7, 7.8 Hz, 2,4-H), 7.44 (2H, d, J = 5.0 Hz, 9,18-
H), 7.52 (4H, d, J = 7.7 Hz, 4 × o-H), 7.67 (4H, t, J = 7.7 Hz, 4 × m-
H), 7.68 (1H, t, J = 7.8 Hz, 3-H), 7.77 (2H, t, J = 7.5 Hz, 2 × p-H),
7.83 (2H, d, J = 5.0 Hz, 8,19-H), 10.52 (2H, br s, 23,25-H). 13C NMR
(CDCl3): δ 15.8, 17.9, 96.0, 111.7, 127.2, 128.1, 128.5, 130.9, 132.9,
134.0, 137.8, 138.1, 140.3, 142.6, 143.3, 148.4, 156.7. 13C NMR (TFA/
CDCl3): δ 15.1, 18.3, 96.3, 99.7, 128.8, 129.0, 132.8, 132.9, 134.9,
136.3, 138.2, 139.4, 139.6, 143.8, 146.2, 151.1, 153.4, 161.2. HRMS
(ESI) m/z: calcd for C38H31N3 + H, 530.2596; found, 530.2293.
3-tert-Butyl-13,14-diethyl-6,21-diphenylbenziporphyrin
(12b). Tripyrrane analogue 8b (97.5 mg, 22 mmol) was reacted with
11 (39.4 mg, 0.22 mmol) under the foregoing conditions for 12a to
give benziporphyrin 12b (74.5 mg, 0.127 mmol, 58%) as a dark solid.
Mp: >300 °C. UV−vis (1% Et3N/CH2Cl2) λmax (log ε): 315 (4.48),
403 (4.83), 656 (3.96). UV−vis (1% TFA/CH2Cl2) λmax (log ε): 447
(5.07), 789 (4.26). 1H NMR (500 MHz, CDCl3): δ 0.96 (9H, s, t-Bu),
1.28 (6H, t, J = 7.6 Hz, 2 × CH2CH3), 2.72 (4H, q, J = 7.6 Hz, 13,14-
CH2), 6.32 (2H, s, 11,16-H), 6.96 (2H, d, J = 4.6 Hz, 9,18-H), 7.04
(2H, d, J = 1.6 Hz, 2,4-H), 7.15 (1H, t, J = 1.6 Hz, 22-H), 7.31 (2H, d,
J = 4.6 Hz, 8,19-H), 7.44−7.47 (10H, m, 2 × Ph), 9.81 (1H, br s, NH).
1H NMR (500 MHz, TFA/CDCl3): δ 1.05 (9H, s, t-Bu), 1.31 (6H, t, J
EXPERIMENTAL SECTION
■
Melting points are uncorrected. UV−vis data are reported as λmax/nm
(log[ε/M−1 cm−1]). NMR spectra were recorded using a 400 or 500
1
MHz NMR spectrometer. H NMR values are reported as chemical
shift (δ), relative integral, multiplicity (s, singlet; d, doublet; t, triplet;
q, quartet; m, multiplet; br, broad peak), and coupling constant (J).
Chemical shifts are reported in parts per million relative to CDCl3 (1H
residual CHCl3, δ 7.26; 13C CDCl3 triplet, δ 77.23), and coupling
constants were taken directly from the spectra. NMR assignments
1
were made with the aid of H−1H COSY, HSQC, DEPT-135, and
NOE difference proton NMR spectroscopy. 2D NMR experiments
were performed using standard software. High-resolution mass
spectrometry (HRMS) was carried out using a double-focusing
1
magnetic sector instrument. H and 13C NMR spectra for all of the
new compounds are reported in the Supporting Information.
1,3-Bis(phenylpyrrolylmethyl)benzene (8a). Nitrogen was
bubbled through a solution of bis(phenylhydroxymethyl)benzene8
(580 mg, 2.00 mmol) and pyrrole (20 mL) in 1,2-dichloroethane (40
mL) for 20 min, after which 1.5 mL of a 10% BF3·Et2O solution in
dichloromethane was added and the resulting mixture was stirred
under reflux for 16 h. The solution was cooled to room temperature,
and the reaction was quenched by addition of triethylamine (2 mL).
The solvent was removed on a rotary evaporator at aspirator pressures,
and then an oil pump was attached to remove excess pyrrole. The
product was purified by column chromatography on silica, eluting with
a mixture of hexanes, dichloromethane, and triethylamine in a ratio of
60:40:1. Evaporation of the product fractions gave the benzitripyrrane
(0.51 g, 1.31 mmol, 66%) as a pale-colored oil that was stored in the
freezer. The NMR data were consistent with the presence of two
diastereomers. 1H NMR (500 MHz, CDCl3): δ 5.253, 5.256 (2H, two
overlapping singlets), 5.65 (2H, m), 6.01 (2H, m), 6.51 (2H, m), 6.92
(2H, dd, J = 1.8, 7.6 Hz), 6.98−7.00 (1H, two overlapping triplets, J =
2.0 Hz), 7.03 (4H, d, J = 7.6 Hz), 7.09−7.13 (3H, m), 7.17 (4H, t, J =
7.6 Hz), 7.56 (2H, br s). 13C NMR (CDCl3): δ 50.68, 50.70, 108.11,
108.13, 108.4, 117.3, 126.8, 127.30, 127.31, 128.6, 128.8, 129.0,
129.79, 129.81, 133.7, 143.2, 143.47, 143.49. HRMS (EI) m/z: calcd
for C28H24N2, 388.1939; found, 388.1943.
= 7.7 Hz, 2 × CH2CH3), 2.86 (4H, q, J = 7.7 Hz, 13,14-CH2), 5.21
(1H, t, J = 1.6 Hz, 22-H), 6.88 (1H, br s, 24-NH), 7.03 (2H, s, 11,16-
H), 7.18 (2H, d, J = 1.6 Hz, 2,4-H), 7.51 (2H, dd, J = 1.2, 5.0 Hz, 9,18-
H), 7.54 (4H, d, J = 7.7 Hz, 4 × o-H), 7.71 (4H, t, J = 7.7 Hz, 4 × m-
H), 7.82 (2H, t, J = 7.5 Hz, 2 × p-H), 7.91 (2H, dd, J = 1.3, 5.0 Hz,
8,19-H), 9.95 (1H, br s, 23,25-NH). 13C NMR (CDCl3): δ 15.9, 17.9,
30.9, 34.6, 95.9, 109.4, 127.1, 128.0, 130.6, 131.6, 133.1, 137.6, 137.8,
140.2, 143.3, 143.4, 148.1, 150.5, 156.6, 170.1. 13C NMR (TFA/
CDCl3): δ 15.0, 18.3, 30.4, 35.5, 96.2, 96.8, 128.8, 129.1, 133.4, 134.3,
135.3, 138.1, 139.5, 143.8, 146.3, 152.2, 152.9, 156.9, 160.7. HRMS
(EI) m/z: calcd for C42H39N3, 585.3144; found, 585.3138.
(13,14-Diethyl-6,21-diphenylbenziporphyrinato)palladium-
(II) (13a). Benziporphyrin 12a (15.0 mg, 0.028 mmol) and
palladium(II) acetate (15 mg) in acetonitrile (15 mL) were heated
under reflux for 30 min. The solution was cooled to room temperature,
diluted with dichloromethane, and washed with water, and the organic
solution was evaporated under reduced pressure. The residue was
purified by column chromatography on grade-3 basic alumina, eluting
with chloroform, and the product was collected as a red-brown
fraction. Recrystallization from chloroform/methanol gave the
palladium complex (12.9 mg, 0.020 mmol, 73%) as dark crystals.
Mp: 269−270 °C. UV−vis (CH2Cl2) λmax (log ε): 310 (4.46), 403 (sh,
4.62), 423 (4.87), 499 (sh, 3.50), 535 (3.70), 573 (3.64), 680 (sh,
5-tert-Butyl-1,3-bis(phenylpyrrolylmethyl)benzene (8b).
Under the same conditions as described above for 8a, dicarbinol 9b8
reacted with pyrrole (20 mL) to give the tripyrrane analogue (0.62 g,
1.4 mmol, 70%) as a pale-colored oil that solidified upon standing in
the freezer. The NMR data were consistent with the presence of two
1
diastereomers. H NMR (500 MHz, CDCl3): δ 1.13 (9H, s), 5.29
(2H, s), 5.66−5.68 (2H, m), 6.03−6.05 (2H, m), 6.57−6.59 (2H, m),
6.77−6.79 (1H, two overlapping triplets, J = 1.6 Hz), 7.01 (2H, d, J =
1.6 Hz), 7.06 (4H, d, J = 7.7 Hz), 7.11−7.15 (2H, m), 7.17−7.21 (4H,
m), 7.64 (2H, br s). 13C NMR (CDCl3): δ 31.5, 34.9, 51.05, 51.07,
108.1, 108.4, 117.2, 124.6, 126.7, 126.8, 128.6, 129.0, 134.03, 134.05,
142.8, 143.53, 143.55, 151.7. HRMS (EI) m/z: calcd for C32H32N2
444.2565; found 444.2560.
13,14-Diethyl-6,21-diphenylbenziporphyrin (12a). Benzitri-
pyrrane 8a (85 mg, 0.22 mmol) and pyrroledialdehyde 1134 (39.4
mg, 0.22 mmol) were dissolved in dichloromethane (100 mL), and
nitrogen was bubbled through the solution for 5 min. TFA (1 mL) was
then added, and the resulting solution was stirred in the dark under
nitrogen at room temperature for 2 h. DDQ (51 mg) was added, and
the mixture was stirred for a further 1 h. The solution was washed with
5% aqueous sodium bicarbonate solution and water, and the solvent
was removed under reduced pressure. The residue was purified on a
grade-3 alumina column, eluting with dichloromethane, and the
product was collected as a dark-green band. Evaporation of the solvent
1
3.46), 747 (3.75), 825 (3.71). H NMR (500 MHz, CDCl3): δ 1.41
(6H, t, J = 7.6 Hz, 2 × CH2CH3), 2.95 (4H, q, J = 7.6 Hz, 13,14-CH2),
7.15 (2H, d, J = 5.0 Hz, 8,19-H), 7.18 (2H, t, J = 7.7 Hz, 3-H), 7.27
(2H, s, 11,16-H), 7.33 (2H, d, J = 5.0 Hz, 9,18-H), 7.44−7.52 (6H, m,
m-H + p-H), 7.56−7.59 (4H, m, 4 × o-H), 7.81 (2H, d, J = 7.7 Hz, 2,4-
H). 13C NMR (CDCl3): δ 16.5, 18.5, 99.3, 124.8, 126.6, 127.5, 130.7,
132.5, 134.3, 136.3, 142.2, 142.6, 142.8, 143.2, 144.1, 145.2, 153.4,
157.8. HRMS (EI) m/z: calcd for C38H29N3Pd, 633.1396; found,
633.1402.
(3-tert-Butyl-13,14-diethyl-6,21-diphenylbenziporphyrin-
ato)palladium(II) (13b). Benziporphyrin 12b (20 mg, 0.034 mmol)
and palladium(II) acetate (20 mg) were reacted in a mixture of
chloroform (10 mL) and acetonitrile (10 mL) under the foregoing
conditions for 13a. Recrystallization from chloroform/methanol gave
the palladium complex (17.3 mg, 0.025 mmol, 74%) as dark crystals.
9149
dx.doi.org/10.1021/jo401365p | J. Org. Chem. 2013, 78, 9143−9152

The Journal of Organic Chemistry
Article
Mp: 239−240 °C. UV−vis (CH2Cl2) λmax (log ε): 311 (4.47), 405 (sh,
and the residue was purified by column chromatography on silica,
eluting initially with chloroform and then with 1−2% methanol/
chloroform. The product fraction was repurified on a second silica
column, affording a dark-green band. Evaporation of the solvent under
reduced pressure gave the oxabenziporphyrin in a partially protonated
form (43.4 mg, 0.081 mmol, 28%) as shiny dark crystals. Mp: >300 °C.
UV−vis (5% Et3N/CH2Cl2) λmax (log ε): 385 (4.29), 637 (3.79). UV−
vis (CH2Cl2) λmax (log ε): 274 (4.62), 377 (4.18), 448 (4.38), 730 (sh,
3.82), 807 (4.13). UV−vis (1% TFA/CH2Cl2) λmax (log ε): 380
(4.27), 454 (4.79), 617 (3.71), 758 (3.87). 1H NMR (500 MHz, TFA/
CDCl3): δ 5.65 (1H, br t, J = 1.5 Hz, 22-H), 6.98 (2H, dd, J = 1.4, 5.0
Hz, 9,18-H), 7.31 (2H, dd, J = 1.5, 7.8 Hz, 2,4-H), 7.48 (2H, s, 13,14-
H), 7.53 (4H, d, J = 7.6 Hz), 7.58 (4H, d, J = 8.0 Hz), 7.62 (4H, t, J =
7.6 Hz), 7.67 (2H, t, J = 7.4 Hz), 7.74 (4H, t, J = 7.8 Hz), 7.81 (2H,
dd, J = 1.6, 5.0 Hz, 8,19-H), 7.85−7.88 (3H, m), 11.24 (2H, br s, 2 ×
NH). 13C NMR (TFA/CDCl3): δ 104.4, 114.5, 129.4, 129.5, 129.7,
131.2, 132.6, 133.2, 134.6, 134.7, 134.8, 135.9, 138.05, 138.08, 138.9,
144.3, 157.5, 163.5. HRMS (ESI) m/z: calcd for C46H30N2O + H,
627.2436; found, 627.2450.
3-tert-Butyl-6,11,16,21-tetraphenyl-24-oxabenziporphyrin
(17d). Furandicarbinol 8b (81.3 mg was reacted with 16b36 (128.7
mg, 0.29 mmol) under the foregoing conditions for 17c to give 17d·
HCl (45.4 mg, 0.080 mmol, 28%) as shiny dark crystals. Mp: >300 °C.
UV−vis (5% Et3N/CH2Cl2) λmax (log ε): 395 (4.25), 445 (sh, 4.06),
602 (3.72). UV−vis (CH2Cl2) λmax (log ε): 265 (4.55), 352 (4.27),
381 (4.09), 452 (4.37), 730 (sh, 3.75), 806 (4.09). UV−vis (1% TFA/
CH2Cl2) λmax (log ε): 352 (4.25), 384 (4.12), 456 (4.68), 768 (3.76).
1H NMR (500 MHz, TFA/CDCl3): δ 1.13 (9H, s, t-Bu), 5.30 (1H, t, J
= 1.5 Hz, 22-H), 7.00 (2H, dd, J = 1.6, 5.1 Hz, 9,18-H), 7.31 (2H, d, J
= 1.4 Hz, 2,4-H), 7.50 (2H, s, 13,14-H), 7.54 (4H, d, J = 7.6 Hz), 7.60
(4H, d, J = 8.0 Hz), 7.63 (4H, t, J = 7.7 Hz), 7.68 (2H, t, J = 7.4 Hz),
7.76 (4H, t, J = 7.9 Hz), 7.83 (2H, dd, J = 1.8, 5.1 Hz, 8,19-H), 7.89
(2H, t, J = 7.5 Hz), 11.05 (2H, s, 2 × NH). 13C NMR (TFA/CDCl3):
δ 30.5, 35.6, 101.7, 114.5, 129.2, 129.5, 129.7, 131.2, 132.7, 134.72,
134.78, 135.7, 136.1, 137.9, 138.6, 138.9, 144.2, 157.3, 158.1, 161.1,
163.3. HRMS (EI) m/z: calcd for C50H38N2O + H, 683.3062; found,
683.3071.
Crystallographic Experimental Details for 13b·0.5C6H14. X-
ray-quality crystals of palladium complex 13b·0.5C6H14 (C45H44N3Pd)
were obtained by vapor diffusion of hexane into a chloroform solution
of the compound. The crystals were suspended in mineral oil at
ambient temperature, and a suitable crystal was selected. The thereby-
obtained mineral-oil-coated red needle with approximate dimensions
of 0.005 mm × 0.01 mm × 0.12 mm was mounted on a 50 μm
MicroMesh MiTeGen micromount and transferred to a Bruker AXS
SMART APEX CCD X-ray diffractometer. The X-ray diffraction data
were collected at 100(2) K using Mo Kα radiation (λ = 0.71073 Å). A
total of 2556 frames were collected. The total exposure time was
127.80 h. The frames were integrated with the Bruker SAINT software
package using a narrow-frame algorithm.37 Integration of the data
using a monoclinic unit cell yielded a total of 82 747 reflections to a
maximum θ angle of 29.306° (0.73 Å resolution), of which 9535 were
4.66), 425 (4.89), 499 (sh, 3.58), 535 (3.83), 574 (3.83), 689 (sh,
1
3.51), 747 (3.75), 826 (3.73). H NMR (500 MHz, CDCl3): δ 1.01
(9H, s, t-Bu), 1.43 (6H, t, J = 7.6 Hz, 2 × CH2CH3), 2.98 (4H, q, J =
7.6 Hz, 13,14-CH2), 7.20 (2H, d, J = 5.0 Hz, 8,19-H), 7.32 (2H, s,
11,16-H), 7.37 (2H, d, J = 5.0 Hz, 9,18-H), 7.45−7.53 (6H, m, m-H +
p-H), 7.59−7.61 (4H, m, 4 × o-H), 7.90 (2H, s, 2,4-H). 13C NMR
(CDCl3): δ 16.6, 18.5, 30.6, 34.1, 99.2, 126.4, 127.5, 130.5, 132.5,
134.0, 136.2, 140.5, 142.8, 143.1, 144.0, 145.1, 146.1, 153.1, 157.4.
HRMS (EI) m/z: calcd for C42H37N3Pd, 689.2022; found, 689.2035.
6,11,16,21-Tetraphenyl-24-thiabenziporphyrin (17a). Nitro-
gen was bubbled through a solution of thiophenedicarbinol 16a35
(85.8 mg, 0.29 mmol) and benzitripyrrane 8a (112.5 mg, 0.29 mmol)
in dichloromethane (90 mL) for 10 min, and 200 μL of a 10% BF3·
Et2O solution in dichloromethane was then added. The resulting
solution was stirred in the dark at room temperature under nitrogen
for 2 h. DDQ (194 mg) was added, and the mixture was stirred for a
further 30 min. The mixture was washed with water, and the solvent
was evaporated under reduced pressure. The residue was chromato-
graphed on a grade-2 alumina column, eluting with dichloromethane,
and the product was collected as a bright-green band. Evaporation of
the solvent under reduced pressure gave the thiabenziporphyrin (70.5
mg, 0.11 mmol, 38%) as a dark solid. Mp: >300 °C. UV−vis (1%
Et3N/CH2Cl2) λmax (log ε): 335 (4.40), 411 (4.70), 643 (4.03). UV−
vis (1% TFA/CH2Cl2) λmax (log ε): 346 (4.42), 390 (4.44), 475
1
(5.00), 708 (3.92), 876 (4.19). H NMR (500 MHz, CDCl3): δ 6.62
(2H, d, J = 4.7 Hz, 9,18-H), 7.09 (2H, dd, J = 1.3, 7.7 Hz, 2,4-H), 7.17
(2H, s, 13,14-H), 7.27−7.33 (4H, m), 7.39−7.44 (6H, m), 7.45−7.48
1
(14H, m). H NMR (500 MHz, TFA/CDCl3): δ 5.29 (1H, br s, 22-
H), 7.22 (2H, d, J = 4.9 Hz, 9,18-H), 7.36 (2H, dd, J = 1.2, 7.8 Hz, 2,4-
H), 7.56 (4H, d, J = 7.6 Hz), 7.61 (4H, d, J = 7.6 Hz), 7.64−7.71 (6H,
m), 7.75 (4H, t, J = 7.6 Hz), 7.80 (1H, t, J = 7.8 Hz, 3-H), 7.89 (2H, t,
J = 7.4 Hz), 7.97 (2H, d, J = 4.9 Hz, 8,19-H), 7.98 (2H, s, 13,14-H).
13C NMR (CDCl3): δ 113.0, 126.8, 127.9, 128.4, 128.8, 129.0, 129.89,
129.96, 131.3, 132.8, 133.2, 135.7, 137.1, 138.9, 139.9, 143.1, 147.9,
154.8, 155.0, 172.2. 13C NMR (TFA/CDCl3): δ 100.2, 129.0, 129.5,
129.6, 129.8, 131.7, 132.5, 132.6, 135.0, 135.2, 135.9, 137.7, 138.7,
139.8, 140.0, 142.0, 143.3, 154.4, 156.8, 164.1. HRMS (EI) m/z: calcd
for C46H30N2S, 642.2129; found, 642.2130.
3-tert-Butyl-6,11,16,21-tetraphenyl-24-thiabenziporphyrin
(17b). Using the foregoing procedure for 17a, dicarbinol 16a35 (85.8
mg, 0.29 mmol) was reacted with 8b (128.7 mg, 0.29 mmol) to give
thiabenziporphyrin 17b (61.5 mg, 0.088 mmol, 30%) as a dark solid.
Mp: 210−212 °C (dec). UV−vis (1% Et3N/CH2Cl2) λmax (log ε): 342
(4.37), 416 (4.69), 643 (3.98). UV−vis (1% TFA/CH2Cl2) λmax (log
1
ε): 344 (4.36), 398 (4.43), 477 (4.99), 703 (3.94), 880 (4.16). H
NMR (500 MHz, CDCl3): δ 1.00 (9H, s, t-Bu), 6.64 (2H, d, J = 4.7
Hz, 9,18-H), 7.04 (1H, t, J = 1.5 Hz, 22-H), 7.10 (2H, d, J = 1.5 Hz,
2,4-H), 7.20 (2H, s, 13,14-H), 7.31 (2H, d, J = 4.7 Hz, 8,19-H), 7.39−
1
7.49 (20H, m, 4 × Ph). H NMR (500 MHz, TFA/CDCl3): δ 1.09
(9H, s, t-Bu), 4.95 (1H, t, J = 1.5 Hz, 22-H), 7.23 (2H, d, J = 5.0 Hz,
9,18-H), 7.35 (2H, d, J = 1.5, 2,4-H), 7.57 (4H, d, J = 8.0 Hz), 7.62−
7.71 (10H, m), 7.77 (4H, t, J = 7.8 Hz), 7.90 (2H, t, J = 7.5 Hz), 7.97
(2H, d, J = 5.0 Hz, 8,19-H), 8.00 (2H, s, 13,14-H). 13C NMR
(CDCl3): δ 31.0, 34.7, 110.8, 127.6, 127.9, 128.4, 128.9, 129.6, 129.9,
131.4, 131.5, 133.0, 135.6, 137.2, 139.0, 139.3, 143.4, 148.6, 150.7,
154.69, 154.75, 171.9. 13C NMR (TFA/CDCl3): δ 30.4, 35.5, 98.1,
128.8, 129.2, 129.5, 129.8, 131.6, 132.6, 134.9, 135.4, 135.7, 136.0,
138.4, 139.7, 140.0, 141.9, 143.0, 154.2, 156.6, 157.3, 163.7. HRMS
(EI) m/z: calcd for C50H38N2S, 698.2756; found, 698.2750.
independent (average redundancy 8.678, completeness = 99.9%, Rin2t
=
>
10.82%, Rsig = 7.08%) and 6719 (70.47%) were observed with Fo
2
2σ(Fo ). The final cell constants a = 10.3442(3) Å, b = 29.4631(8) Å, c
= 11.8597(3) Å, β = 105.406(2)°, and volume = 3484.63(17) Å3 are
based upon the refinement of the XYZ centroids of 9379 reflections
above 20σ(I) with 4.5° < 2θ < 53.26°. Limiting indices were as
follows: −14 ≤ h ≤ 14, −40 ≤ k ≤ 40, −16 ≤ l ≤ 16. Data were
corrected for absorption effects using the multiscan method
(SADABS).37 The ratio of minimum to maximum apparent trans-
mission was 0.788 with minimum and maximum SADABS-generated
transmission coefficients of 0.588 and 0.746. Solution and data analysis
were performed using the WinGX software package.38 The structure
was solved and refined in the space group P21/c (No. 14) with Z = 4.39
The solution was achieved by charge-flipping methods using the
program SUPERFLIP,40,41 and the refinement was completed using
the program SHELX2013.42,43 Residual electron density consistent
with disordered hexane was clearly identified, but no suitable model
for the hexane was found. The solvent electron density was near
6,11,16,21-Tetraphenyl-24-oxabenziporphyrin (17c). Nitro-
gen was bubbled through a solution of furandicarbinol 16b36 (81.3 mg,
0.29 mmol) and benzitripyrrane 8a (112.5 mg, 0.29 mmol) in
dichloromethane (90 mL) for 10 min, and 200 μL of a 10% BF3·Et2O
solution in dichloromethane was then added. The resulting solution
was stirred in the dark at room temperature under nitrogen for 2 h.
TFA (2 mL) was added, immediately followed by DDQ (194 mg), and
the mixture was stirred for a further 30 min. The solution was washed
with water, 5% aqueous sodium bicarbonate solution, water, and 10%
hydrochloric acid. The solvent was evaporated under reduced pressure,
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special positions. SQUEEZE was used to “remove” the solvent from
the original hkl file. SQUEEZE found 58 electrons in each of the voids
that contained hexane (50 electrons). Final refinement was carried out
using the SQUEEZE-modified hkl file. All non-H atoms were refined
anisotropically. All H atoms were included in the refinement in the
riding-model approximation [C−H = 0.95, 0.98, and 0.99 Å for Ar−H,
CH3, and CH2; 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 = 0.000] with R1 =
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2
0.0467 and wR2 = 0.0929 for 6719 data with Fo2 > 2σ(Fo ) using zero
restraints and 420 parameters. A final difference Fourier synthesis
showed features in the range of Δρmax = 0.644 e−/Å3 to Δρmin
=
−1.173 e−/Å3. All residual electron density away from the solvent was
within accepted norms and deemed to have no chemical significance.
Molecular diagrams were generated using ORTEP-3.38 CCDC 952780
contains the supplementary crystallographic data for this paper. These
data can be obtained free of charge from the Cambridge Crystallo-
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(21) For examples of hetero-oxybenziporphyrins and heterocarba-
porphyrins, see: (a) Liu, D.; Lash, T. D. Chem. Commun. 2002, 2426−
2427. (b) Venkatraman, S.; Anand, V. G.; Pushpan, S. K.; Sankar, J.;
Chandrashekar, T. K. Chem. Commun. 2002, 462−463. (c) Liu, D.;
Ferrence, G. M.; Lash, T. D. J. Org. Chem. 2004, 69, 6079−6093.
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ASSOCIATED CONTENT
■
S
* Supporting Information
Selected 1H NMR, 1H−1H COSY, HSQC, 13C NMR, MS, and
UV−vis spectra and a CIF for the X-ray structure of 13b. This
material is available free of charge via the Internet at http://
pubs.acs.org.
(22) For an example of an N-confused thiapyriporphyrin, see:
Mysliborski, R.; Rachlewicz, K.; Latos-Grazyn
Inorg. Chem. 2006, 45, 7828−7834.
ski, L.; Szterenberg, L.
̇
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: tdlash@ilstu.edu.
Notes
(23) For an example of a thia-p-benziporphyrin, see: Hung, C.-H.;
Lin, C.-Y.; Lin, P.-Y.; Chen, Y.-J. Tetrahedron Lett. 2004, 45, 129−132.
(24) For examples of hetero-N-confused porphyrins, see: (a) Heo,
P.-Y.; Lee, C.-H. Tetrahedron Lett. 1996, 37, 197−200. (b) Heo, P.-Y.;
Lee, C.-H. Bull. Korean Chem. Soc. 1996, 17, 515−520. (c) Lee, C.-H.;
Kim, H.-J. Tetrahedron Lett. 1997, 38, 3935−3938. (d) Lee, C.-H.;
Kim, H.-J.; Yoon, D.-W. Bull. Korean Chem. Soc. 1999, 20, 276−280.
(e) Yoon, C.-H.; Lee, C.-H. Bull. Korean Chem. Soc. 2000, 21, 618−
622. (f) Pushpan, S. K.; Srinivasan, A.; Anand, V. R. G.;
Chandrashekar, T. K.; Subramaniam, A.; Roy, R.; Siguira, K.-i.;
Sakata, Y. J. Org. Chem. 2001, 66, 153−161. (g) Pacholska, E.; Latos-
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by the National Science Foundation
under Grants CHE-0911699 and CHE-1212691 and by the
Petroleum Research Fund, administered by the American
Chemical Society. The authors also thank NSF (Grant CHE-
1039689) for providing funding for the X-ray diffractometer.
Grazyn
́
̇
8188−8196. (h) Sprutta, N.; Latos-Grazyn
1933−1936.
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