Tetraaryldimethoxybenziporphyrins. At the edge of carbaporphyrinoid aromaticity

Article abstract of DOI:10.1021/jo070947k

(Chemical Equation Presented) A series of eight dimethoxybenziporphyrins were prepared in three steps from 1,3-dimethoxybenzene or 2,6-dimethoxytoluene. Dibromination, followed by lithium-halogen exchange and reaction with benzaldehyde gave dicarbinol int

Full text of DOI:10.1021/jo070947k

Tetraaryldimethoxybenziporphyrins. At the Edge of
Carbaporphyrinoid Aromaticity†
Timothy D. Lash,* Joseph T. Szymanski, and Gregory M. Ferrence
Department of Chemistry, Illinois State UniVersity, Normal, Illinois 61790-4160
tdlash@ilstu.edu
ReceiVed May 6, 2007
A series of eight dimethoxybenziporphyrins were prepared in three steps from 1,3-dimethoxybenzene or
2,6-dimethoxytoluene. Dibromination, followed by lithium-halogen exchange and reaction with
benzaldehyde gave dicarbinol intermediates. These reacted with pyrrole and aryl aldehydes in the presence
of BF3‚Et2O in chloroform, followed by oxidation with DDQ, to give the benziporphyrins in 15-25%
yield. These compounds readily gave nickel(II) and palladium(II) organometallic derivatives and could
be selectively reduced with sodium borohydride to give unstable benziphlorins. Regioselective oxidation
with silver acetate afforded the related 22-acetoxybenziporphyrins in 52-64% yield. The dimethoxy-
benziporphyrins showed chemical shifts by proton NMR spectroscopy that were consistent with weakly
diatropic macrocycles. However, addition of TFA gave dications that showed far more significant shifts
2+
that are attributed to the presence of a more substantial diatropic ring current. The internal CH for 11H2
was observed at 3.5 ppm, but this effect was diminished for the 3-methylbenziporphyrins 12H22+ where
this resonance appears at 4.7 ppm. Even in the absence of the methoxy substituents, the dication derived
from tetraphenylbenziporphyrin 8H22+ shows an upfield shift for this resonance to 5.5 ppm. The dications
of the 22-acetoxybenziporphyrins also show similar effects despite the presence of an internal ester moiety.
These results demonstrate that a spectrum of diatropic character can manifest even in highly crowded
benziporphyrin derivatives.
Introduction
conjugated systems that show no indication of any overall
aromatic character.5 However, the presence of electron-donating
methoxy groups in 2b, and to a lesser extent in 2c, leads to
weakly diatropic species, particularly for the protonated por-
phyrinoids.6 Furthermore, addition of a hydroxyl substituent at
C-2 facilitates a keto-enol-like tautomerization that results in
the fully aromatic carbaporphyrinoid system oxybenziporphyrin
3.3,4,7 Benziporphyrins 2 and 3, as well as related carbaporphy-
rinoids such as the azuliporphyrins 4,8 can easily be prepared
using a ‘3 + 1’ version of the MacDonald condensation.9
Although this strategy has been very successful, it relies on the
Replacement of one or two isoindole moieties in phthalo-
cyanines with benzene units gives rise to macrocycles such as
1,1 while a similar substitution of a pyrrole group in the
porphyrin macrocycle leads to benziporphyrins such as 2a (Chart
1).2-4 The presence of these benzene units give rise to cross-
† Part 42 in the series ‘Conjugated Macrocycles Related to the Porphyrins’.
(1) (a) Linstead, R. P. J. Chem. Soc. 1953, 2873-2884. (b) Wu, R.;
Cetin, A.; Durfee, W. S.; Ziegler, C. J. Angew. Chem., Int. Ed. 2006, 45,
5670-5673.
(2) Berlin, K.; Breitmaier, E. Angew. Chem., Int. Ed. Engl. 1994, 33,
1246-1247.
(3) Lash, T. D. Angew. Chem., Int. Ed. Engl. 1995, 34, 2533-2535.
(4) Lash, T. D.; Chaney, S. T.; Richter, D. T. J. Org. Chem. 1998, 63,
9076-9088.
(5) Lash, T. D. Synlett 2000, 279-295.
(6) Richter, D. T.; Lash, T. D. Tetrahedron 2001, 57, 3659-3673. See
also: Miyake, K.; Lash, T. D. Chem. Commun. 2004, 178-179.
(7) Liu, D.; Lash, T. D. J. Org. Chem. 2003, 68, 1755-1761.
10.1021/jo070947k CCC: $37.00 © 2007 American Chemical Society
Published on Web 07/26/2007
J. Org. Chem. 2007, 72, 6481-6492
6481

Lash et al.
CHART 1
SCHEME 1
We have been exploring the limits of aromatic character in
carbaporphyrinoids and for this reason wanted to prepare the
analogous dimethoxybenziporphyrins 11 and 12. In this paper,
efficient syntheses of these porphyrin analogues are reported,
and their reactivity and spectroscopic characteristics are con-
trasted to benziporphyrins 8.18,19
Results and Discussion
The synthesis of meso-tetraarylbenziporphyrins requires the
availability of dicarbinols such as 7 (Scheme 1). Stepien and
Latos-Grazynski prepared 7 in 56% yield by reacting a
deficiency of phenylmagnesium bromide with isophthalalde-
hyde.13 Although this approach could be used to prepare the
related dimethoxy derivatives 13a and 13b, we speculated that
a more efficient synthesis could be accomplished by using the
readily available dibromodimethoxybenzenes 1420 (Scheme 2).
Treatment of 4,6-dibromo-1,3-dimethoxybenzene (14a) with
n-butyllithium afforded the dilithiated species 15a, and this was
directly reacted with benzaldehyde to give the dicarbinol 13a
in 71% yield. Similarly, the dimethoxytoluene derivative 14b
afforded the related dicarbinol 13b in 62% yield. In both cases,
the proton and carbon-13 NMR spectra indicated that the
products had been isolated as a mixture of two diastereomers,
but this was not important, as the stereochemistry is not retained
in the final tetraarylbenziporphyrins. The synthesis of 11a was
availability of tripyrrane intermediates that must be prepared
by a multistep approach.10 This limits the quantities of material
available for further study. In addition, meso-unsubstituted
porphyrin analogues are often less soluble in organic solvents
and may be less stable than their meso-tetrasubstituted coun-
terparts.11 These considerations led us to develop a one-step
route to tetraarylazuliporphyrins 5 using Lindsey-Rothemund
conditions, and oxidative ring contraction allows access to the
related benzocarbaporphyrins 6.11,12 In independent work,
Stepien and Latos-Grazynski demonstrated that dicarbinol 7
condensed with pyrrole and aryl aldehydes under similar reaction
conditions to give nonaromatic tetraarylbenziporphyrins 8
(Scheme 1A).13 This approach was also successfully used in
the synthesis of the aromatic porphyrin analogue tetrapheny-
loxybenziporphyrin 9 from the phenolic dicarbinol 10 (Scheme
1B).14 These systems have been used to prepare interesting
coordination complexes and some organometallic derivatives.15-17
(15) Stepien, M.; Latos-Grazynski, L.; Szterenberg, L.; Panek, J.; Latajka,
Z. J. Am. Chem. Soc. 2004, 126, 4566-4580.
(16) Stepien, M.; Latos-Grazynski, L. Acc. Chem. Res. 2005, 38, 88-
98.
(17) (a) Graham, S. R.; Ferrence, G. M.; Lash, T. D. Chem. Commun.
2002, 894-895. (b) Muckey, M. A.; Szczepura, L. F.; Ferrence, G. M.;
Lash, T. D. Inorg. Chem. 2002, 41, 4840-4842.
(18) Preliminary communication: Szymanski, J. T.; Lash, T. D. Tetra-
hedron Lett. 2003, 44, 8613-8616.
(19) These results were presented, in part, at the following meetings:
(a) Szymanski, J. T.; Lash, T. D. Program and Abstracts, 35th Great Lakes
Regional American Chemical Society Meeting, Loyola University, Chicago,
IL, June 2003; American Chemical Society: Washington, DC, 2003;
Abstract No. 216. (b) Szymanski, J. T.; Lash, T. D. Book of Abstracts,
227th National ACS Meeting, Anaheim, CA, March 28-April 1, 2004;
American Chemical Society: Washington, DC, 2004; ORGN 147. (c)
Szymanski, J. T.; Lash, T. D. Program and Abstracts, 36th Great Lakes
Regional American Chemical Society Meeting, Peoria, IL, October 2004;
American Chemical Society: Washington, DC, 2004; Abstract No. 315.
(20) Worden, L. R.; Kaufman, K. D.; Smith, P. J.; Widiger, G. N. J.
Chem. Soc. (C) 1969, 227-230.
(8) (a) Lash, T. D.; Chaney, S. T. Angew. Chem., Int. Ed. Engl. 1997,
36, 839-840. (b) Graham, S. R.; Colby, D. A.; Lash, T. D. Angew. Chem.,
Int. Ed. 2002, 41, 1371-1374. (c) Lash, T. D.; Colby, D. A.; Graham, S.
R.; Chaney, S. T. J. Org. Chem. 2004, 69, 8851-8864.
(9) Lash, T. D. Chem. Eur. J. 1996, 2, 1197-1200.
(10) (a) Sessler, J. L.; Johnson, M. R.; Lynch, V. J. Org. Chem. 1987,
52, 4394-4397. (b) Lash, T. D. J. Porphyrins Phthalocyanines 1997, 1,
29-44.
(11) Colby, D. A.; Lash, T. D. Chem. Eur. J. 2002, 8, 5397-5402.
(12) Lash, T. D.; Colby, D. A.; Ferrence, G. M. Eur. J. Org. Chem.
2003, 4533-4548.
(13) Stepien, M.; Latos-Grazynski, L. Chem. Eur. J. 2001, 7, 5113-
5117.
(14) El-Beck, J. A.; Lash, T. D. Org. Lett. 2006, 8, 5263-5266.
6482 J. Org. Chem., Vol. 72, No. 17, 2007

Tetraaryldimethoxybenziporphyrins
SCHEME 2
initially attempted by mixing a dichloromethane solution of 13a
with 2 equiv of benzaldehyde and 3 equiv of pyrrole in the
presence of BF3‚Et2O. Following oxidation with DDQ, chro-
matography on silica and recrystallization from chloroform-
methanol, the meso-tetraphenyldimethoxybenziporphyrin 11a
was isolated in 5% yield. Previously, it has been observed that
the yields for many sterically hindered porphyrins,21,22 as well
as tetraarylazuliporphyrins,11,12 are greatly improved when
chloroform is used as the solvent for this chemistry. This appears
to be because of the presence of ethanol as a stabilizer which
modifies the reactivity of the Lewis acid catalyst. Under
optimized conditions using chloroform, the yield of 11a was
raised to 15%. Significantly, under the same conditions, 13b
reacted with pyrrole and benzaldehyde to give the related
porphyrinoid 12a in 25% yield.
The superior yields obtained in these studies, and the small
number of steps involved, allows the synthesis of significant
quantities of dimethoxybenziporphyrins. In the synthesis of
tetraphenylporphyrins, all of the carbon-carbon bond forming
steps are potentially reversible, and this can lead to the
scrambling of the meso-substituents.23 This issue arises because
the electron-rich pyrrole units can easily protonate and eliminate
and because a second pyrrole group can stabilize the resulting
carbocation. The electron-donating methoxy groups might
facilitate acidolytic cleavage reactions, and the use of other aryl
aldehydes were investigated to see whether dicarbinols 13a and
13b gave single benziporphyrin products. Hence, 13a and 13b
were treated with 4-tert-butylbenzaldehyde, p-tolualdehyde, or
4-chlorobenzaldehede under the same reaction conditions.
Following workup, column chromatography, and recrystalliza-
tion, only one isomerically pure benziporphyrin product was
obtained in each case. Yields in these reactions varied from 15
to 25%, but the methyl-substituted dicarbinol consistently gave
superior yields, and 4-chlorobenzaldehyde also gave slightly
better results in these investigations. Hence, this methodology
allows for the regiospecific introduction of two different aryl
substituents without any problems arising due to scrambling.
For benziporphyrins, the presence of a benzene ring intro-
duces an element of cross-conjugation and does not allow for
FIGURE 1. Proton NMR chemical shifts for selected protons on
tetraphenylbenziporphyrins in CDCl3 and the related dications in TFA-
CDCl3 at 25 °C.
an 18π electron delocalization pathway. For this reason, these
macrocycles would not be expected to exhibit diatropic ring
currents in their proton NMR spectra.5 In addition, meso-aryl
substituents generally decrease the planarity of porphyrins, and
in the case of 11 and 12 this effect would be further exacerbated
because of the presence of adjacent methoxy units that are
oriented toward two of the phenyl moieties. Although the proton
NMR chemical shifts for aromatic systems can be misleading,24
the diatropic character of porphyrinoid systems is generally
accepted as a reliable guide to macrocyclic aromaticity.24-26 It
was intriguing, therefore, that the internal CH of 11a resonates
at 5.84 ppm. This suggests the presence of a small diamagnetic
ring current, as tetraphenylbenziporphyrin 8 shows this reso-
nance at 7.3 ppm (Figure 1). In addition, the NH for 11a gives
rise to a broad peak at 9.2 ppm compared to 10.3 for 8. In the
proton NMR spectrum for 12a, these resonances show up at
6.42 and 9.9 ppm, respectively, indicating that 11a is more
aromatic than 12a. Although these shifts are relatively small,
the corresponding dications 11H22+ or 12H22+ that are formed
by addition of TFA to solutions of 11 or 12 in CDCl3 showed
far more pronounced effects (Figure 2). In the proton NMR
2+
spectrum of 11aH2 in TFA-CDCl3, the internal CH shifts
upfield to 3.5 ppm, while the NHs give rise to two resonances
at 8.4 (2H) and 6.8 ppm (1H). The external pyrrolic protons
also shift downfield by ca. 0.5 ppm. This effect is much reduced
for the 2-methylbenziporphyrin dication 12aH22+, where the
interior CH was observed at 4.7 ppm and the NH resonances
(21) Lindsey, J. S.; Wagner, R. W. J. Org. Chem. 1989, 54, 828-836.
(22) (a) Lash, T. D.; Novak, B. H. Angew. Chem., Int. Ed. Engl. 1995,
34, 683-685. (b) Lash, T. D.; Chandrasekar, P. J. Am. Chem. Soc. 1996,
118, 8767-8768. (c) Spence, J. D.; Lash, T. D. J. Org. Chem. 2000, 65,
1530-1539.
(23) Geier, G. R., III; Lindsey, J. S. J. Chem. Soc., Perkin Trans. 2 2001,
677-686.
(24) Wannere, C. S.; Corminboeuf, C.; Allen, W. D.; Schaefer, H. F.,
III; Schleyer, P. v. R. Org. Lett. 2005, 7, 1457-1460.
(25) Mu¨llen, K.; Meul, T.; Schade, P.; Schmickler, H.; Vogel, E. J. Am.
Chem. Soc. 1987, 109, 4992-5003.
(26) Steiner, E.; Soncini, A.; Fowler, P. W. Org. Biomol. Chem. 2005,
3, 4053-4059.
J. Org. Chem, Vol. 72, No. 17, 2007 6483

Lash et al.
SCHEME 3
SCHEME 4
systems that have properties that are intermediary between
tetraphenylbenziporphyrin 8 and tetraphenylazuliporphyrin 5.11,12
It is noteworthy that the free base and dicationic forms for these
macrocycles show increasing aromatic character going from 8
to 12 to 11 to 5. However, tetraphenyloxybenziporphyrin 9
shows the greatest aromatic character for the free base but
reverts to a nonaromatic phenolic species upon diprotonation.14
For instance, the proton NMR spectra for the free base forms
in CDCl3 show the internal CHs of 8, 12a, 11a, 5 and 9 at
7.33, 6.42, 5.84, 3.35 and -3.0 ppm, respectively. These
differences cannot be simply due to electron-donating effects,
and are paralleled by a downfield shift of the external pyrrolic
protons. The dications for 12a, 11a, and azuliporphyrin 5 show
a more pronounced trend for the inner CH, giving resonances
at 4.73, 3.5, and -0.33 ppm,12 respectively. However, this
proton is shifted downfield for 9H22+, showing up at 4.25 ppm.14
The upfield shifts for the internal CHs is paralleled by a
FIGURE 2. 400 MHz proton NMR spectra of dimethoxybenzipor-
phyrin 11a in CDCl3 (A, free base) and TFA-CDCl3 (B, dication
11aH22+). The internal CH (position 22) shows a pronounced upfield
shift from 5.8 to 3.5 ppm due to increased macrocyclic diatropicity.
appeared at 8.2 and 9.9 ppm. Even so, these shifts clearly point
2+
to the presence of a diamagnetic ring current for 12aH2 as
well as for 11aH22+. Similar results were obtained for the mixed
tetraaarylbenziporphyrins 11b-d and 12b-d, although the more
electron-donating p-tolyl- or 4-tert-butylphenyl-substituted por-
phyrinoids 11/12b,c showed a slight increase in the diatropic
shifts. The origin of the observed diatropic character for the
dimethoxybenziporphyrins most likely derives from the electron-
donating influence of the methoxy groupings. These effects
allow for better charge delocalization in the protonated species
2+
downfield shift for the external pyrrolic protons, with 9H2
again showing the opposite trend. Perhaps most surprising of
all is that the dication 8H22+ of tetraphenylbenziporphyrin shows
an upfield shift for the internal CH to 5.5 ppm (Figure 1).
Although the shift is small, this result suggests that resonance
contributors of the type shown in Scheme 4 allow for a small
diatropic ring current in this case as well.
2+
2+
11H2 and 12H2 (Scheme 3). A series of canonical forms
(e.g., A-D) can be used to describe these dications, and in
contributors such as C and D, electron-donation leads to the
presence of an 18π-electron delocalization pathway. These
electronic interactions require the oxygen atoms to take on sp2
hydrid character, and this requires the methoxy groups to lie in
the same plane as the macrocycle. The methyl-substituted system
is too sterically crowded to easily allow the methoxy units to
take on the required geometry, although the associated electronic
interaction must still occur to a limited extent. The electron-
donating groups also provide more stabilization to the delocal-
ized dicationic species. The free-base molecules 11 and 12 can
have similar dipolar resonance contributors, but these are less
favored because of the associated need for charge separation.
Hence, dimethoxytetraphenylbenziporphyrins are intriguing
The UV-vis spectra for the free base forms of 11a, 12a,
and 8 are similar to one another, showing a weak Soret-like
band slightly above 400 nm, and a broad absorption near 700
nm (Figure 3). However, there is a bathochromic shift for the
shorter wavelength band going from 8 to 12a to 11a, giving
λmax values of 437, 422, and 411 nm, respectively. The dications
of 12a, 11a, and 5 in 1% TFA-chloroform all show a strong
broad absorption in the far red, although in this case there is a
hypsochromic shift for the series with the λmax values at 889,
876, and 850 nm, respectively. The dication of 8 gives data
that are in agreement with this trend, showing the equivalent
absorption at >900 nm.13
6484 J. Org. Chem., Vol. 72, No. 17, 2007

Tetraaryldimethoxybenziporphyrins
SCHEME 6
virtually quantitative yield. Tetraphenylbenziporphyrin 8 was
generated in 13% yield using the previously reported procedure
(Scheme 1A).13 Interestingly, this reaction only gave good
results when dichloromethane was used as the reaction solvent
and, in contrast to our other results, virtually no benziporphyrin
was formed when the reaction was carried out in chloroform.
Benziporphyrin afforded the nickel(II) complex Ni8 in good
yields when using excess nickel(II) acetate in refluxing chlo-
roform-methanol. The nickel(II) complex of 8 was subse-
quently reported by Stepien et al. using somewhat different
metalation conditions as part of a far more detailed report on
the metallo-derivatives of benziporphyrins.15 In our original
communication,18 we noted that palladium(II) acetate failed to
react with 11a or 12a to give palladium(II) benziporphyrins 17,
and considerable decomposition was noted for prolonged
reaction times under the conditions used to prepare 16. However,
when the reactions were carried out in refluxing acetonitrile the
palladium(II) derivatives 17 could be isolated in 73-81% yield
(Scheme 5).
FIGURE 3. UV-vis spectra of dimethoxybenziporphyrin 11a in 1%
Et3N-chloroform (blue line, free base) and 1% TFA-chloroform (red
line, dication 11aH22+).
SCHEME 5
The proton NMR spectra for the nickel(II) and palladium(II)
complexes were consistent with the proposed diamagnetic
organometallic species 16 and 17. The proton NMR spectra for
nickel(II) benziporphyrins 16a and 16b in CDCl3 gave reso-
nances for the pyrrolic protons that were ca. 0.6 ppm further
downfield than the corresponding free bases 16a and 16b, and
similar, albeit smaller, shifts were noted for the 2-methylben-
ziporphyrin complexes 16c and 16d as well. In addition, the
external pyrrolic protons for Ni8 gave peaks that were between
0.3 and 0.5 ppm upfield from those for 16a and 16b while the
2-methyl metalloporphyrinoids 16c and 16d gave intermediary
values. For instance, the 13,14-pyrrolic protons for Ni8, 16c,
and 16a were 7.3, 7.4, and 7.6 ppm, respectively. Similar trends
were noted for the palladium(II) complexes 17 as well. These
results imply that the metallo-derivatives 16 and 17 have
significantly higher diatropic character than the corresponding
free base dimethoxybenziporphyrins, a feature that may be due
in part to a conformational change associated with binding to
metal cations. Both the nickel(II) and palladium derivatives also
show a clear trend of increased diatropic character due to the
presence of the methoxy groups with the 2-methyl versions again
showing smaller shifts due to the disruptive steric interactions
previously discussed. The UV-vis spectra for 16 and 17 showed
multiple bands with weak Soret-like absorptions between 400
and 500 nm. However, the UV-vis spectra for the nickel
complexes 16 did not give reproducible results, apparently
because of irreversible degradation processes in the dilute
solutions. No problems were encountered running the NMR
spectra of 16, and the palladium(II) derivatives 17 did not show
Azuliporphyrins and benziporphyrins undergo metalation with
nickel(II) or palladium(II) salts,15-17,27 and it was of some
interest to see whether it is also possible to synthesize organo-
metallic derivatives of this type for 11 and 12. These studies
were conducted on 11a,b and 12a,b so that four different
metallo-derivatives were available. Nickel(II) acetate in chlo-
roform-methanol was found to cleanly react with 11 and 12
to afford the related organometallic derivatives 16 in 70-80%
yield (Scheme 5). When these initial studies were conducted,18
the nickel(II) derivative of tetraphenylbenziporphyrin 8 had not
been reported and this metalloporphyrinoid was prepared so that
comparisons could be made to the dimethoxy metallo-derivatives
16. The synthesis of 8 requires dicarbinol 7 as a precursor, and
this was previously obtained by reacting a Grignard reagent with
isophthalaldehyde.13 Yields could be substantially improved by
using an excess of phenylmagnesium bromide or phenyllithium.
However, we considered dicarboxylic acids to be far more
convenient precursors to the required dicarbinols. Isophthalic
acid is easily converted into 1,3-dibenzoylbenzene (Scheme 6),28
and reduction with sodium borohydride in ethanol gives 7 in
(27) Stepien, M.; Latos-Grazynski, L.; Lash, T. D.; Szterenberg, L. Inorg.
Chem. 2001, 40, 6892-6900.
(28) Dischendorfer, O.; Verdino, A. Monatsh. Chem. 1935, 66, 255-
284.
J. Org. Chem, Vol. 72, No. 17, 2007 6485

Lash et al.
SCHEME 7
FIGURE 4. ORTEP III drawing (35% probability level, hydrogen
atoms drawn arbitrarily small) of nickel complex 16a showing the
twisted geometry of the benzene subunit. Selected bond lengths (Å):
Ni-C(22) 1.969(3), Ni-N(23) 1.922(3), Ni-N(24) 1.967(3), Ni-N(25)
1.915(3), C(1)-C(22) 1.424(5), C(5)-C(22) 1.436(4). Selected bond
angles (deg): C(22)-Ni-N(24) 166.2(1), N(23)-Ni-N(25) 166.5-
(1), C(22)-Ni-N(23) 91.6(1), C(22)-Ni-N(25) 92.1(1), N(23)-Ni-
N(24) 89.5(1), N(24)-Ni-N(25) 89.9(1), C(1)-C(22)-C(5) 114.6(3).
any significant variations in their spectra. Stepien et al. have
noted that the C-Ni bond of Ni8 can be cleaved with HCl to
generate a paramagnetic nickel(II) complex,15 but we have not
pursued this line of investigation.
Despite these observations, slow growth of X-ray quality
crystals for 16a was accomplished (Figure 4). Black single-
crystal blocks of 16a were grown by vapor diffusion of hexanes
into a dichloroethane solution followed by slow evaporation.
The nickel(II) ion coordinates to the three tripyrrane nitrogen
atoms and C(22) and is best described as having a distorted
square planar coordination geometry. The macrocycle adopts a
saddle geometry with the dimethoxyphenyl ring bent nearly 40°
out of the NiN3 plane. Close examination of the structure
indicates this striking feature is attributable to contact between
the alkoxy oxygen atoms and the adjacent phenyl ipso carbon
atoms. The 2.587(4) Å O(2a)-C(21a) and 2.599(4) Å O(4a)-
C(6a) bond separations are substantially smaller than the 2.95
Å sum of the Pauling Van der Waal radii. The 1.969(3) Å Ni-C
bond length is well within the typical range of four coordinate
divalent nickel(II) complexes;29 however, it is more than 60 pm
longer than the corresponding parameter in other nickel(II)
carbaporphyrinoid examples.17,30-32 That the steric strain im-
posed by the C(22) metal coordination coupled with the
crowding imposed by the methoxy groups is substantial is shown
by the significant dimethoxyphenyl ring distortion from planarity
demonstrated by the more than 15° C(1)-C(22)-C(5)-C(4)
and C(5)-C(22)-C(1)-C(2) torsion angles.
reduction with sodium borohydride to give benziphlorin 18,
while oxidation with silver acetate afforded the 22-acetoxy
derivative 8OAc.13 Dimethoxybenziporphyrin 11a was reacted
with NaBH4 in ethanol-chloroform for 16 h and gave blue-
green solutions of the dihydrobenziporphyrin 19a (Scheme 7).
This compound was not very stable but could be recrystallized
to give a reasonably pure product. The same chemistry could
be performed on 12a, but the resulting phlorin 19b was
significantly less stable and could not be fully purified.
Nevertheless, 11a and 12a show similar reactivity toward
NaBH4 as 8.
In order to further contrast the dimethoxy macrocycles 11
and 12 with 8, additional reactivity studies were carried out.
Benziporphyrin 8 has been shown to undergo regioselective
(29) Allen, F. H. Acta Crystallogr. 2002, B58, 380-388; Cambridge
Structural Database, version 5.28 (Nov 2006).
(30) Pawlicki, M.; Latos-Grazynski, L. Chem. Eur. J. 2003, 9, 4650-
4660.
(31) Xiao, Z.; Patrick, B. O.; Dolphin, D. Chem. Commun. 2002, 1816-
1817.
Dimethoxybenziporphyrin 11a was reacted with silver acetate
in refluxing acetonitrile-chloroform for 2 h, and following
column chromatography on basic alumina and recrystallization
from chloroform-methanol, the related acetoxy compound 20a
was isolated in 60% yield (Scheme 7). Benziporphyrins 11b
and 12a were found to react similarly to give the 22-acetoxy
(32) Schmidt, I.; Chmielewski, P. J.; Ciunik, Z. J. Org. Chem. 2002,
67, 8917-8927.
6486 J. Org. Chem., Vol. 72, No. 17, 2007

Tetraaryldimethoxybenziporphyrins
1
TABLE 1. Selected H NMR Chemical Shifts for 22-acetoxybenziporphyrins
OAc
OMe
3
8,19
9,18
13,14
24
23,25
8OAc (R ) X ) H)
in CDCl3
in TFA-CDCl3
20a (R ) H; X ) OMe)
in CDCl3
in TFA-CDCl3
20c (R ) Me; X ) OMe)
in CDCl3
1.33
1.03
-
-
7.19
7.6
7.32
7.93
6.54
7.21
6.86
7.41
9.50
6.1
-
10.3
1.12
0.51
3.4
3.5
6.35
6.51
7.4
8.0
6.5
7.3
6.9
7.7
8.9
4.2
-
8.4
1.29
0.93
3.21
3.16
-
-
7.4
7.9
6.5
7.2
6.8
7.5
9.4
5.7
-
in TFA-CDCl3
10.0
derivatives 20b and 20c, respectively, in 52-64% yield. The
same chemistry was performed on 12b, but in this case poor
results were obtained and the product 20d could not be isolated
in pure form. Clearly, 11 and 12 have similar reactivity to 8,
and the silver acetate reaction provides a convenient method
for derivatization of the internal carbon. On the basis of steric
considerations, it initially seemed somewhat implausible that
acetates 20 would exhibit any diatropic character. However, the
acetate group gives a 3H singlet at 1.12 ppm for 20a and at
1.29 ppm for 20c, indicating that this moiety is shielded by the
π-system (Table 1). More significantly, addition of TFA gives
of the dications comes from the large downfield shifts for the
pyrrolic hydrogens (∆δ ) 0.6-0.8 ppm for 20a and ∆δ ) 0.5-
0.7 ppm for 20c). In addition, the NH resonances for the
protonated species are upfield from the values expected for a
dication and in 20aH22+ show up at 4.2 (1H) and 8.4 (2H) ppm
(Table 1). The shifts suggest that these dications have compa-
2+
rable diatropicity to the parent benziporphyrin dications 11H2
and 12H22+. This property is presumably still due to resonance
2+
contributors such as 20′H2 which facilitate charge delocal-
ization, and the results imply that the system must retain
sufficient planarity to allow π-conjugation over the macrocycle.
The internal acetate unit can hydrogen bond to the NHs, and
this presumably holds the ring system in a favorable geometry
for π-electron delocalization. In addition, this intramolecular
hydrogen bonding interaction would further stabilize this system.
It is possible that this is also a factor for the free base 22-acetate
derivatives 20, but it is worth noting that the free base form of
8OAc has been characterized by X-ray crystallography and does
not show this type of interaction. Instead, 16 showed hydrogen
bonding between the imine nitrogens and a cocrystallized water
molecule, and the acetate carbonyl was orientated away from
the central cavity.13 In order to compare our data with 8OAc, a
sample of this compound was also prepared and proton NMR
spectra were obtained in CDCl3 and TFA-CDCl3 (the former
spectrum was virtually identical to the spectrum reported by
Stepien and Latos-Grazynski13). This compound again showed
significant shifts upon protonation that were consistent with a
small diatropic ring current (Table 1). The acetate methyl
resonance shifted upfield by 0.3 ppm for 8OAcH22+, and one
of the internal NH resonances was present at 6.11 ppm. The
2+
dications 20H2 where the acetate resonance for 20a shifts
upfield to 0.51 ppm (Figure 5), while in the case of 20c this
unit gives a peak at 0.93 ppm. These shifts are consistent with
a significant diatropic ring current for the acetate dications, and
once again the effect is reduced by the presence of a methyl
group at position 3. Further evidence for the diatropic character
2+
results indicate that the diatropic character is largest for 20aH2
and smallest for 8OAcH22+, but even when no methoxy
substituents are present there are still significant shifts that
support the presence of a small diatropic ring current.33 The
UV-vis spectra for the dications gave broad absorptions at 849
(33) As a counterpoint to our observations, it is worth noting that 22-
hydroxytetraphenylbenziporphyrin tautomerizes to give an antiaromatic
ketone that affords paratropic proton NMR chemical shifts: Stepien, M.;
Latos-Grazynski, L.; Szterenberg, L. J. Org. Chem. 2007, 72, 2259-2270.
For a related azuliporphyrin derivative, see: Colby, D. A.; Ferrence, G.
M.; Lash, T. D. Angew. Chem., Int. Ed. 2004, 43, 1346-1349.
FIGURE 5. Partial 400 MHz proton NMR spectra for 22-acetoxy-
benziporphyrin 20a in CDCl3 (A, free base) and TFA-CDCl3 (B,
dication 20aH22+). The acetate resonance shifts upfield from 1.1 to 0.5
ppm while the 24-NH shifts from 8.9 to 4.2 ppm.
J. Org. Chem, Vol. 72, No. 17, 2007 6487

Lash et al.
diastereomers), 156.9 (2 peaks for diastereomers). Anal. Calcd for
C23H24O4: C, 75.80; H, 6.64. Found: C, 75.44; H, 6.64.
nm for 20a and 873 nm for 20c, and in this respect these spectra
resembled those obtained for the parent benziporphyrins 11a
and 12a.
1,3-Bis(r-hydroxyphenylmethyl)benzene (7). 1,3-Dibenzoyl-
benzene (10.00 g; 35.0 mmol) and ethanol (100 mL) were placed
in a 500 mL Erlenmeyer flask and stirred with gentle heating on a
hot plate until the diketone had completely dissolved. Sodium
borohydride was added over 5 min in four portions to the hot
solution and the mixture stirred at room temperature for 15 min.
Water (100 mL) was added, and the mixture was heated to gentle
boiling and stirred for 30 min. The mixture was diluted with water
(200 mL) and cooled in an ice bath, and the resulting white
precipitate was suction filtered and washed well with water. The
sample was dried in Vacuo to give the dicarbinol (9.74 g;
33.6 mmol; 96%) as a white powder, mp 129-132 °C. As expected,
the NMR data showed the presence of two diastereomers. 1H NMR
(CDCl3): δ 2.28 (2H, d, J ) 3.5 Hz), 5.81 (2H, d, J ) 3.5 Hz),
7.23-7.37 (13H, m), 7.45-7.48 (1H, m); 13C NMR (CDCl3): δ
76.5, 125.0, 126.0, 126.1, 126.8, 126.9, 127.8, 128.7, 128.9, 144.0,
144.4.
Conclusions
A straightforward three-step route to electron-rich tetraphen-
ylbenziporphyrins 11 and 12 from dimethoxybenzenes has been
developed. These novel porphyrin analogues show enhanced
diatropic character under acidic conditions that is similar to the
results obtained for azuliporphyrins.8,11,12 While these shifts are
not as large as those observed for the azuliporphyrins, a small
diatropic ring current can even be observed for the tetraphen-
ylbenziporphyrin dication 8H22+. The new macrocycles readily
form nickel(II) and palladium(II) complexes and can be
selectively reduced with sodium borohydride to give benziphlo-
rins. Reaction with silver acetate gives 22-acetoxy derivatives,
but the internal acetate group does not disrupt the diatropicity
of the related dications 20H22+ relative to the 22-unsubstituted
versions to any significant extent. These studies make far more
diverse tetraarylbenziporphyrin structures available for study and
demonstrate that these porphyrin analogues may have varying
degrees of aromatic character even when a high degree of steric
crowding is present.
2,4-Dimethoxy-6,11,16,21-tetraphenylbenziporphyrin (11a).
Nitrogen was slowly bubbled through a stirred solution of 4,6-bis-
(R-hydroxyphenylmethyl)-1,3-dimethoxybenzene (0.70 g; 2.0 mmol)
in 900 mL of chloroform in a 1 L round-bottom flask that had
been covered with aluminum foil to protect the reaction from
ambient light. A septum was placed in the neck of the flask, and a
nitrogen-filled balloon was attached to maintain the inert atmo-
sphere. Next, freshly distilled pyrrole (420 µL; 6.0 mmol) and
benzaldehyde (400 µL; 4.0 mmol) were added via syringe, followed
by 0.20 mL of boron trifluoride etherate. The resulting mixture
was stirred for 2 h at room temperature. The initially colorless
solution turned orange and then became a deep red color. DDQ
(1.40 g; 98%; 6.0 mmol) was added and the mixture stirred for an
additional 10 min. The dark solution was evaporated under reduced
pressure and the residue purified on a Grade 3 basic alumina column
eluting with dichloromethane. Tetraphenylporphyrin and unidenti-
fied brown byproducts eluted initially, followed by a dark emerald
green band corresponding to the title benziporphyrin. Recrystalli-
zation from chloroform-methanol gave the dimethoxybenzipor-
phyrin (210 mg; 0.306 mmol; 15%) as a green powder, mp 282-
284 °C, dec; UV-vis (1% Et3N-CHCl3): λmax (log ꢀ) 354 (4.59),
437 (4.75), 657 (sh, 4.15), 699 nm (4.23); UV-vis (1% TFA-
CHCl3): λmax (log ꢀ) 322 (4.46), 404 (4.71), 488 (4.76), 601 (3.80),
664 (3.80), 876 nm (4.41); 1H NMR (CDCl3): δ 3.37 (6H, s), 5.84
(1H, s), 6.40 (1H, s), 6.56 (2H, d, J ) 4.8 Hz), 6.88 (2H, s), 7.38-
7.45 (14H, m), 7.48-7.52 (4H, m), 7.56-7.60 (4H, m), 9.23 (1H,
Experimental Section
4,6-Bis(r-hydroxyphenylmethyl)-1,3-dimethoxybenzene (13a).
A solution of n-butyllithium in hexanes (2.5 M; 40 mL; 64 mmol)
was added via a syringe to a stirred solution of 4,6-dibromo-1,3-
dimethoxybenzene (8.30 g; 28.0 mmol) in sodium-dried ether
(450 mL) under a nitrogen atmosphere. The resulting cloudy white
mixture was stirred for 15 min at room temperature. After this time,
benzaldehyde (8.10 g; 76 mmol) was added dropwise via a pressure-
equalized addition funnel over a period of approximately 5 min
and a thick white precipitate was formed. After the mixture had
stirred for a further 10 min, 200 mL of aqueous 10% ammonium
chloride solution was added. The ether layer was separated and
dried over sodium sulfate, and the solvent was evaporated under
reduced pressure. The residue was recrystallized from chloroform-
petroleum ether (60-90°) to give the dicarbinol (6.98 g; 19.9 mmol;
71%) as small white crystals, mp 114-116 °C; 1H NMR (CDCl3):
δ 2.86-2.90 (2H, m), 3.80 (6H, s), 5.95 (2H, d, J ) 5.2 Hz), 6.45
(1H, s), 7.13 and 7.18 (2 singlets for diastereomers, 1H), 7.22-
7.34 (10H, m); 13C NMR (CDCl3): δ 55.9, 72.3, 95.9, 124.4, 126.6,
127.2, 127.7, 127.8, 128.0, 128.3 (2 peaks), 143.8, 157.4. Anal.
Calcd for C22H22O4: C, 75.41; H, 6.33. Found: C, 74.85; H, 6.53.
1
br s); H NMR (TFA-CDCl3): δ 3.49 (6H, s), 3.52 (1H, s), 6.55
(1H, s), 6.93 (1H, br s), 7.17 (2H, dd, J ) 1,2 4.8 Hz), 7.50 (2H,
s), 7.62-7.730 (16H, m), 7.85-7.89 (6H, m), 8.45 (2H, br s); 13
C
NMR (TFA-CDCl3): δ 56.3, 97.0, 99.6, 115.9, 122.3, 128.3,
128.9, 129.0, 130.3, 131.9, 132.9, 133.5, 134.1, 136.6, 136.9, 140.0,
144.1, 147.0, 150.6, 158.8, 163.9; EI MS (70 eV): m/z (% rel int)
690.4 (4.5), 689.4 (11), 688.4 (15), 687.4 (27), 686.4 (2), 685.4 (2,
M+), 344.9 (3.3), 343.9 (9.6, M2+), 91.0 (100); HR MS: Calcd for
C48H35N3O2 + 2H: 687.2886. Found: 687.2877. Anal. Calcd for
C48H35N3O2·1/8CHCl3: C, 82.49; H, 5.05; N, 6.00. Found: C, 82.49;
H, 5.06; N, 6.08.
3,5-Bis(r-hydroxyphenylmethyl)-2,6-dimethoxytoluene (13b).
The title compound was prepared by the foregoing procedure from
3,5-dibromo-2,6-dimethoxytoluene (8.00 g; 25.8 mmol), 32.3 mL
of n-butyllithium (2.5 M solution in hexanes; 51.7 mmol) and
benzaldehyde (5.49 g; 51.7 mmol). Recrystallization was performed
by first dissolving the crude product in methanol, heating the
solution on a hot water bath, and adding water until the solution
remained slightly turbid even at elevated temperatures. The mixture
was allowed to stand at room temperature for 5 days in order to
allow crystal formation. The white precipitate was suction filtered,
dried in Vacuo overnight, and further recrystallized from chloroform-
ether to give the dialcohol (5.88 g; 16.1 mmol; 62%) as a white
2,4-Dimethoxy-11,16-bis(4-tert-butylphenyl)-6,21-diphenyl-
benziporphyrin (11b). The bis(tert-butylphenyl) derivative was
prepared by the same procedure from dicarbinol 13a (0.70 g;
2.0 mmol), pyrrole (415 µL; 6.0 mmol), 4-tert-butylbenzaldehyde
(0.65 g; 4.0 mmol), and 200 µL of BF3‚Et2O. Recrystallization from
chloroform-methanol gave 11b (255 mg; 0.320 mmol; 16%) as
very dark green crystals, mp 242-244 °C; UV-vis (1% Et3N-
CHCl3): λmax (log ꢀ) 325 (sh, 4.55), 356 (4.56), 440 (4.75), 674
(sh, 4.16), 711 nm (4.24); UV-vis (1% TFA-CHCl3): λmax (log
ꢀ) 327 (4.43), 416 (4.73), 494 (4.79), 674 (3.91), 895 nm (4.39);
1H NMR (CDCl3): δ 1.40 (18H, s), 3.37 (6H, s), 5.86 (1H, s),
6.40 (1H, s), 6.60 (2H, d, J ) 4.8 Hz), 6.95 (2H, s), 7.39 (2H, d,
J ) 4.8 Hz), 7.37-7.46 (14H, m), 7.57-7.60 (4H, m), 9.26 (1H,
1
powder, mp 89-91 °C; H NMR (CDCl3): δ 2.18 (3H, s), 2.9-
3.0 (2H, br m), 3.47 and 3.48 (2 singlets for the diastereomers,
6H), 5.96 (1H), 7.23-7.38 (10H, m); 13C NMR (CDCl3): δ 10.2,
60.9 (2 peaks for diastereomers), 72.3 and 72.4 (2 peaks for
diastereomers), 125.0 (2 peaks for diastereomers), 125.2 (2 peaks
for diastereomers), 126.7 (2 peaks for diastereomers), 127.5 (2 peaks
for diastereomers), 128.5 (2 peaks), 132.8, 144.2 (2 peaks for
6488 J. Org. Chem., Vol. 72, No. 17, 2007

Tetraaryldimethoxybenziporphyrins
br s); 1H NMR (TFA-CDCl3; 30 °C): δ 1.46 (18H, s), 3.36 (1H,
s), 3.48 (6H, s), 6.56 (1H, s), 6.59 (1H, br s), 7.22 (2H, dd, J )
1.6, 5.2 Hz), 7.55 (2H, d, J ) 1.2 Hz), 7.60-7.73 (16H, m), 7.85-
7.90 (6H, m), 8.26 (2H, br s); 13C NMR (CDCl3): δ 31.7, 34.8,
55.6, 98.4, 109.8, 114.5, 122.1, 124.8, 127.3, 127.7, 129.7, 130.8,
131.6, 132.4, 135.2, 137.3, 142.0, 143.6, 147.3, 150.3, 156.6, 160.0,
170.6; 13C NMR (TFA-CDCl3): δ 31.4, 35.2, 56.3, 95.7, 99.8,
116.3, 122.3, 126.1, 128.7, 129.0, 132.0, 132.9, 133.6, 134.0, 136.6,
139.9, 144.1, 146.7, 150.1, 154.2, 158.7, 163.9; HR FAB MS:
Calcd for C56H51N3O2 + H: 798.4059. Found: 798.4071. Anal.
Calcd for C56H51N3O2·1/10CHCl3: C, 83.19; H, 6.36; N, 5.19.
Found: C, 83.01; H, 6.13; N, 5.08.
toluene (0.700 g; 1.92 mmol), pyrrole (410 µL; 5.9 mmol),
benzaldehyde (405 µL; 4.0 mmol), boron trifluoride etherate
(200 µL), and DDQ (1.40 g). The crude product was purified on
Grade 3 basic alumina eluting with dichloromethane, and following
a forerun of tetraphenylporphyrin and unidentified brown byprod-
ucts, 12a was collected as a dark emerald green band. The porphyrin
analogue was rechromatographed on Grade 3 basic alumina, eluting
with dichloromethane, and the product fraction recrystallized from
chloroform-methanol to give benziporphyrin 12a (340 mg;
0.486 mmol; 25%) as a navy-blue powder, mp 286-288 °C. In
some batches, the product was obtained as lustrous dark blue-green
flakes. UV-vis (1% Et3N-CHCl3): λmax (logꢀ) 321 (4.50), 368
(4.40), 422 (4.82), 699 nm (4.17); UV-vis (1% TFA-CHCl3): λmax
(logꢀ) 324 (4.44), 404 (sh, 4.56), 472 (4.90), 658 (3.72), 889 nm
2,4-Dimethoxy-11,16-bis(4-methylphenyl)-6,21-diphenylben-
ziporphyrin (11c). The tetraarylporphyrinoid was prepared by the
earlier procedure from dicarbinol 13a (0.700 g; 2.00 mmol), pyrrole
(415 µL; 6.0 mmol), p-tolualdehyde (0.480 g; 4.0 mmol), and
200 µL of BF3‚Et2O. Recrystallization from chloroform-methanol
gave 11c (0.22 g; 0.31 mmol; 15%) as bright green crystals, mp
278-279 °C; UV-vis (1% Et3N-CHCl3): λmax (logꢀ) 326 (4.53),
355 (4.55), 440 (4.74), 670 (sh, 4.16), 707 nm (4.23); UV-vis (1%
TFA-CHCl3): λmax (logꢀ) 325 (4.42), 416 (4.71), 493 (4.77), 673
1
(4.29); H NMR (CDCl3): δ 2.01 (3H, s), 3.27 (6H, s), 6.42 (1H,
s), 6.51 (2H, d, J ) 4.8 Hz), 6.77 (2H, s), 7.38-7.48 (14H, m),
1
7.54-7.58 (8H, m), 9.93 (1H, br s); H NMR (TFA-CDCl3): δ
2.03 (3H, s), 3.19 (6H, s), 4.73 (1H, s), 7.07 (2H, dd, J ) 4.8,
0.8 Hz), 7.33 (2H, s), 7.54-7.64 (10H, m), 7.68-7.76 (10H, m),
7.87 (2H, dd, J ) 5.2, 1.2 Hz), 8.21 (1H, br s), 9.96 (2H, br s); 13
C
NMR (CDCl3): δ 10.4, 61.4, 107.7, 114.7, 127.0, 127.5, 127.8,
128.1, 128.5, 129.3, 131.1, 131.3, 132.5, 135.4, 140.0, 142.7, 142.8,
147.8, 157.2, 158.0, 171.3; 13C NMR (TFA-CDCl3): δ 11.1, 62.7,
92.6, 116.4, 128.6, 129.1, 129.2, 129.4, 130.0, 130.5, 132.5, 132.9,
133.6, 136.3, 137.7, 139.7, 144.7, 148.7, 151.7, 161.1, 162.3; EI
MS (70 eV): m/z (% rel int) 704.4 (9), 703.4 (27), 702.4 (53),
701.4 (100), 700.4 (17), 699.4 (26, M+), 350.9 (26), 349.9 (7.6,
1
(3.89), 888 nm (4.39); H NMR (CDCl3): δ 2.44 (6H, s), 3.37
(6H, s), 5.84 (1H, s), 6.40 (1H, s), 6.58 (2H, d, J ) 4.4 Hz), 6.89
(2H, s), 7.24 (4H, d, J ) 8 Hz), 7.36-7.45 (12H, m), 7.58 (4H, d,
J ) 7 Hz), 9.24 (1H, br s); 1H NMR (TFA-CDCl3): δ 2.55 (6H,
s), 3.27 (1H, s), 3.48 (6H, s), 6.34 (1H, br s), 6.57 (1H, s), 7.20
(2H, dd, J ) 1.2, 5.2 Hz), 7.45 (4H, d, J ) 8 Hz), 7.52 (2H, d, J
) 1.2 Hz), 7.56 (4H, d, J ) 8 Hz), 7.66-7.73 (6H, m), 7.85-7.89
(4H, m), 7.90 (2H, dd, J ) 1.4, 5.0 Hz), 8.17 (2H, br s); 13C NMR
(CDCl3): δ 21.4, 55.6, 98.5, 109.7, 114.4, 122.1, 127.3, 127.7,
128.7, 129.6, 130.7, 131.6, 132.6, 135.3, 137.0, 137.3, 142.1, 143.6,
147.3, 156.6, 159.7, 170.5; 13C NMR (TFA-CDCl3): δ 21.5, 56.3,
95.9, 99.8, 116.2, 122.4, 128.5, 128.9, 129.8, 131.9, 132.8, 133.5,
134.0, 136.6, 140.0, 141.0, 144.1, 146.6, 150.3, 158.8, 163.9; EI
MS (70 eV): m/z (% rel int) 719 (1.8), 718 (3.9), 717 (8.9), 716
(10), 715 (18), 358 (3.4), 91 (100); HR EI MS: Calcd for
C50H39N3O2 + 2H: 715.3199. Found: 715.3202. Anal. Calcd for
C50H39N3O2·1/3CHCl3: C, 80.21; H, 5.26; N, 5.57. Found: C, 79.88;
H, 5.17; N, 5.53.
M
2+), 91.0 (81); HR MS: Calcd for C49H37N3O2 + 2H: 701.3042.
Found: 701.3041. Anal. Calcd for C49H37N3O2‚0.4CHCl3: C, 79.37;
H, 5.04; N, 5.62. Found: C, 79.62; H, 5.02; N, 5.81.
2,4-Dimethoxy-3-methyl-11,16-bis(4-tert-butylphenyl)-6,21-
diphenylbenziporphyrin (12b). The porphyrin analogue was
prepared similarly from dicarbinol 13b (0.700 g; 1.92 mmol),
pyrrole (410 µL; 5.9 mmol), 4-tert-butylbenzaldehyde (0.65 g;
4.0 mmol), and 200 µL of BF3‚Et2O. Recrystallization from
chloroform-methanol gave 12b (0.32 g; 0.40 mmol; 21%) as
lustrous navy blue crystals, mp 260-262 °C; UV-vis (1% Et3N-
CHCl3): λmax (logꢀ) 424 (4.83), 712 nm (4.19); UV-vis (1% TFA-
CHCl3): λmax (logꢀ) 343 (4.47), 411 (sh, 4.61), 477 (4.92), 670
1
(3.80), 900 nm (4.24); H NMR (CDCl3): δ 1.39 (18H, s), 2.01
2,4-Dimethoxy-11,16-bis(4-chlorophenyl)-6,21-diphenylben-
ziporphyrin (11d). The benziporphyrin was prepared by the
foregoing procedure from dicarbinol 13a (1.40 g; 4.00 mmol),
pyrrole (830 µL; 6.0 mmol), 4-chlorobenzaldehyde (1.12 g;
8.0 mmol), and 400 µL of BF3‚Et2O in chloroform (900 mL).
Recrystallization from chloroform-methanol gave 11d (0.58 g;
0.77 mmol; 19%) as dark green crystals, mp 277-278 °C; UV-
vis (1% Et3N-CHCl3): λmax (logꢀ) 357 (4.59), 438 (4.72), 661
(sh, 4.17), 697 nm (4.23); UV-vis (1% TFA-CHCl3): λmax (logꢀ)
322 (4.49), 411 (4.73), 493 (4.77), 601 (3.89), 663 (3.89), 871 nm
(3H, s), 3.27 (6H, s), 6.42 (1H, s), 6.54 (2H, d, J ) 4.8 Hz), 6.82
(2H, s), 7.36 (4H, d, J ) 7.6 Hz), 7.38 (2H, d, J ) 4.4 Hz), 7.42-
7.48 (10H, m), 7.53-7.58 (4H, m), 9.94 (1H, br s); 1H NMR
(TFA-CDCl3): δ 1.43 (18H, s), 2.03 (3H, s), 3.21 (6H, s), 4.68
(1H, s), 7.11 (2H, dd, J ) 1.6, 5.2 Hz), 7.36 (2H, d, J ) 1.6 Hz),
7.48 (4H, d, J ) 8.4 Hz), 7.60 (4H, d, J ) 8.4 Hz), 7.66-7.75
(10H, m), 7.85 (2H, dd, J ) 1.2, 5.2 Hz), 8.22 (1H, br s), 9.92
(2H, br s); 13C NMR (CDCl3): δ 10.3, 31.6, 34.8, 61.3, 107.5,
114.6, 124.9, 126.9, 127.7, 128.3, 129.3, 130.0, 131.3, 131.4, 132.1,
135.2, 137.0, 142.4, 142.8, 147.8, 150.4, 157.2, 157.9, 171.5; 13C
NMR (TFA-CDCl3): δ 11.1, 31.4, 35.2, 62.7, 91.3, 116.7, 126.1,
128.7, 129.1, 129.7, 130.0, 132.4, 132.9, 133.5, 137.4, 139.8, 144.7,
147.9, 151.5, 154.3, 161.0, 162.1; FAB MS: m/z (% rel int) 816
(3.9), 815 (14), 814 (40), 813 (85), 812 (100), 811 (7.2, M+), 810
(3.9); HR FAB MS: Calcd for C57H53N3O2 + H: 812.4216.
Found: 812.4202. Anal. Calcd for C57H53N3O2: C, 84.31; H, 6.58;
N, 5.17. Found: C, 83.81; H, 6.45; N, 5.27.
1
(4.42); H NMR (CDCl3; 30 °C): δ 3.37 (6H, s), 5.82 (1H, s),
6.39 (1H, s), 6.55 (2H, d, J ) 4.8 Hz), 6.86 (2H, s), 7.40-7.47
1
(16H, m), 7.56-7.60 (4H, m), 9.22 (1H, br s); H NMR (TFA-
CDCl3): δ 3.45 (1H, s), 3.49 (6H, s), 6.56 (1H, s), 6.71 (1H, s),
7.17 (2H, dd, J ) 1.6, 5.2 Hz), 7.49 (2H, d, J ) 1.6 Hz), 7.60-
7.64 (8H, m), 7.66-7.76 (6H, m), 7.84-7.87 (4H, m), 7.89 (2H,
dd, J ) 2.0, 5.2 Hz), 8.34 (2H, br s); 13C NMR (CDCl3): δ 55.6,
98.4, 110.4, 113.3, 122.0, 127.4, 127.9, 128.3, 129.6, 130.1, 131.6,
133.6, 133.9, 135.7, 138.7, 143.2, 143.4, 147.1, 156.5, 160.0, 169.8;
13C NMR (TFA-CDCl3): δ 56.3, 97.9, 99.6, 114.6, 122.4, 128.0,
128.9, 129.4, 132.1, 132.7, 133.6, 135.1, 135.3, 136.8, 137.1, 139.9,
144.1, 147.7, 150.4, 158.5, 164.1; EI MS (70 eV): m/z (% rel int)
760 (1.6), 759 (3.7), 758 (4.7), 757 (9.5), 756 (5.9), 755 (10), 377
(2.0), 91 (100); HR EI MS: Calcd for C48H33Cl2N3O2 + 2H:
755.2106. Found: 755.2088. Anal. Calcd for C48H33Cl2N3O2‚1/3-
CHCl3: C, 73.07; H, 4.23; N, 5.29. Found: C, 73.05; H, 4.09; N,
5.16.
2,4-Dimethoxy-3-methyl-11,16-bis(4-methylphenyl)-6,21-di-
phenylbenziporphyrin (12c). Porphyrinoid 12c was prepared from
dicarbinol 13b (0.700 g; 1.92 mmol), pyrrole (420 µL; 6.0 mmol),
p-tolualdehyde (0.480 g; 4.00 mmol), and 200 µL of BF3‚Et2O.
Recrystallization from chloroform-methanol gave 6c (267 mg;
0.367 mmol; 19%) as small shiny purple needles, mp 280-281
°C; UV-vis (1% Et3N-CHCl3): λmax (logꢀ) 425 (4.81), 712 nm
(4.16); UV-vis (1% TFA-CHCl3): λmax (logꢀ) 328 (4.44), 410
(sh, 4.58), 477 (4.90), 673 (3.76), 900 nm (4.22); 1H NMR
(CDCl3): δ 2.01 (3H, s), 2.43 (6H, s), 3.27 (6H, s), 6.41 (1H, s),
6.52 (2H, d, J ) 4.4 Hz), 6.77 (2H, s), 7.22 (4H, d, J ) 8.4 Hz),
7.32 (2H, d, J ) 8.0 Hz), 7.38 (2H, d, J ) 4.4 Hz), 7.41-7.48
2,4-Dimethoxy-3-methyl-6,11,16,21-tetraphenylbenziporphy-
rin (12a). The porphyrin analogue was prepared by the foregoing
procedure from 3,5-bis(R-hydroxyphenylmethyl)-2,6-dimethoxy-
J. Org. Chem, Vol. 72, No. 17, 2007 6489

Lash et al.
1
(6H, m), 7.53-7.56 (4H, m), 9.93 (1H, br s); H NMR (TFA-
(3H, m), 7.89 (2H, dd, J ) 1.6, 5.2 Hz), 9.04 (1H, br s), 10.48
(2H, br s). Ni8:15 1H NMR (CDCl3): δ 6.88 (2H, d, J ) 5.2 Hz),
7.11 (1H, t, J ) 7.6 Hz), 7.16 (2H, d, J ) 5.2 Hz), 7.32 (2H, s),
7.42-7.55 (20H, m), 7.83 (2H, d, J ) 7.6 Hz); 13C NMR
(CDCl3): δ 117.4, 125.0, 126.9, 127.7, 127.9, 130.1, 132.3, 132.5,
133.8, 135.9, 137.9, 139.1, 140.6, 141.0, 143.0; HR MS (FAB):
Calcd for C46H29N3Ni + H: 682.1793. Found: 682.1793. Anal.
Calcd for C46H29N3Ni·1/4CHCl3: C, 77.99; H, 4.14; N, 5.90.
Found: C, 77.89; H, 3.98; N, 5.97. 8OAc:13 1H NMR (CDCl3): δ
1.33 (3H, s), 6.54 (2H, d, J ) 5.2 Hz), 6.86 (2H, s), 7.09 (2H, d,
J ) 8 Hz), 7.19 (1H, t, J ) 7.6 Hz), 7.32 (2H, d, J ) 4.8 Hz),
7.40-7.51 (16H, m), 7.56-7.59 (4H, m), 9.50 (1H, br s); 1H NMR
(TFA-CDCl3): δ 1.03 (3H, s), 6.11 (1H, br s), 7.20 (2H, d, J )
5.2 Hz), 7.21 (2H, d, J ) 7.6 Hz), 7.41 (2H, s), 7.58-7.68 (11H,
m), 7.72-7.74 (6H, m), 7.78-7.84 (4H, m), 7.93 (2H, d, J )
5.2 Hz), 10.31 (2H, br s).
CDCl3): δ 2.02 (3H, s), 2.52 (6H, s), 3.21 (6H, s), 4.64 (1H, s),
7.09 (2H, dd, J ) 1.6, 5.2 Hz), 7.33 (2H, d, J ) 1.2 Hz), 7.38-
7.45 (8H, AB quartet, J ) 8 Hz), 7.60 (4H, d, J ) 8.4 Hz), 7.67-
7.75 (10H, m), 7.86 (2H, dd, J ) 2.0, 5.2 Hz), 8.20 (1H, br s),
9.86 (2H, br s); 13C NMR (CDCl3): δ 10.3, 21.4, 61.3, 107.5, 114.5,
126.9, 127.7, 128.4, 128.8, 129.3, 129.9, 131.2, 132.3, 135.2, 137.0,
137.2, 142.5, 142.7, 147.8, 157.2, 157.9, 171.4; 13C NMR (TFA-
CDCl3): δ 11.0, 21.5, 62.7, 91.2, 116.7, 128.7, 129.1, 129.6, 129.9,
132.4, 132.9, 133.4, 133.6, 137.5, 139.4, 141.3, 144.7, 148.0, 151.5,
161.0, 162.1; EI MS (70 eV): m/z (% rel int) 730 (1.9), 729 (3.7),
91 (100); FAB MS: m/z (% rel int) 732 (3.7), 731 (13), 730 (40),
729 (82), 728 (100), 727 (7.2, M+), 726 (2.6); HR FAB MS: Calcd
for C51H41N3O2 + H: 728.3277. Found: 728.3291. Anal. Calcd
for C51H41N3O2‚0.3CHCl3: C, 80.68; H, 5.45; N, 5.50. Found: C,
80.78; H, 5.40; N, 5.62.
[2,4-Dimethoxy-6,11,16,21-tetraphenylbenziporphyrinato]-
nickel(II) (16a). A solution of 11a (50 mg; 0.0730 mmol) in
chloroform (50 mL) was placed in a 100 mL round-bottom flask
that was covered with foil to protect the reaction from light. A
saturated solution of nickel(II) acetate in methanol (40 mL) was
added and the mixture stirred at room temperature under nitrogen
for 2 h. During the course of the reaction, the solution turned from
a deep green to a brown color. The solution was washed with water,
dried over sodium sulfate, and evaporated under reduced pressure.
The residue was purified on a grade 3 basic alumina column eluting
with chloroform. The organometallic derivative was collected as a
brownish-green band. Recrystallization from chloroform-hexanes,
and then from chloroform-methanol, gave the nickel(II) complex
(44 mg; 0.0594 mmol; 81%) as lustrous black needles, mp 302-
304 °C; UV-vis (CHCl3): λmax (logꢀ) 350 (4.28), 458 (4.43),
2,4-Dimethoxy-3-methyl-11,16-bis(4-chlorophenyl)-6,21-di-
phenylbenziporphyrin (12d). The porphyrin analogue was pre-
pared similarly from dicarbinol 13b (1.40 g; 3.84 mmol), pyrrole
(840 µL; 12 mmol), 4-chlorobenzaldehyde (1.20 g; 8.5 mmol), and
400 µL of BF3‚Et2O in chloroform (900 mL). Recrystallization from
chloroform-methanol gave 12d (0.70 g; 0.91 mmol; 24%) as dark
bluish purple crystals, mp 282-283 °C; UV-vis (1% Et3N-
CHCl3): λmax (logꢀ) 345 (4.49), 424 (4.81), 695 nm (4.17); UV-
vis (1% TFA-CHCl3): λmax (logꢀ) 325 (4.46), 407 (sh, 4.59), 475
(4.90), 660 (3.73), 876 nm (4.31); 1H NMR (CDCl3): δ 2.01 (3H,
s), 3.25 (6H, s), 6.39 (1H, s), 6.48 (2H, d, J ) 4.8 Hz), 6.74 (2H,
s), 7.35-7.42 (8H, AB quartet, J ) 8 Hz), 7.39 (2H, d, partially
obscured), 7.44-7.50 (6H, m), 7.53-7.57 (4H, m), 9.90 (1H, br
1
s); H NMR (TFA-CDCl3): δ 2.03 (3H, s), 3.20 (6H, s), 4.75
(1H, s), 7.06 (2H, dd, J ) 1.4, 5.0 Hz), 7.31 (2H, d, J ) 1.2 Hz),
7.49 (4H, d, J ) 8.4 Hz), 7.58 (4H, d, J ) 8.4 Hz), 7.68-7.76
(10H, m), 7.87 (2H, dd, J ) 1.6, 5.2 Hz), 8.32 (1H, br s), 10.00
(2H, br s); 13C NMR (CDCl3): δ 10.4, 61.3, 108.0, 113.4, 127.0,
127.8, 128.4, 128.6, 129.2, 129.8, 130.7, 131.3, 133.6, 133.7, 135.7,
138.4, 142.6, 143.6, 147.6, 157.0, 158.2, 170.7; 13C NMR (TFA-
CDCl3): δ 11.1, 62.7, 93.4, 115.0, 128.6, 129.0, 129.2, 129.5, 129.9,
132.7, 133.0, 133.4, 134.6, 134.7, 137.3, 137.9, 139.7, 144.7, 149.5,
151.5, 160.7, 162.6; EI MS (70 eV): m/z (% rel int) 774 (2.3),
773 (6.0), 772 (9.0), 771 (18), 770 (13), 769 (23), 768 (3.0), 767
(4.4, M+), 385 (3.0), 91 (100); HR EI MS: Calcd for C49H35-
Cl2N3O2 + 2H: 769.2263. Found: 769.2265. Anal. Calcd for
C49H35Cl2N3O2‚0.4CHCl3: C, 72.67; H, 4.37; N, 5.15. Found: C,
72.74; H, 4.50; N, 5.15.
1
766 nm (4.00); H NMR (CDCl3): δ 3.36 (6H, s), 6.17 (1H, s),
7.24 (2H, d, J ) 4.8 Hz), 7.35-7.39 (2H, dt), 7.42-7.46 (4H, m),
7.48-7.54 (6H, m), 7.56-7.59 (4H, m), 7.59 (2H, s), 7.66 (2H, d,
J ) 4.8 Hz), 7.67-7.71 (4H, m); 13C NMR (CDCl3): δ 55.7, 94.6,
116.6, 125.8, 126.4, 126.8, 127.5, 127.6, 128.6, 131.4, 132.7, 133.3,
134.4, 135.0, 140.1, 144.3, 146.4, 150.7, 154.8, 155.8, 173.5; EI
MS (70 eV): m/z (% rel int) 746.3 (1.5), 745.3 (2.8), 744.3 (1.8),
743.3 (2.9), 742 (<1), 741 (<1), 91.2 (100); HR MS: Calcd for
C48H33N3O2Ni: 741.1926. Found: 741.1921. Anal. Calcd for
C48H33N3NiO2·3/5CHCl3: C, 71.70; H, 4.16; N, 5.16. Found: C,
71.87; H, 4.05; N, 5.25.
[2,4-Dimethoxy-11,16-bis(4-tert-butylphenyl)-6,21-diphenyl-
benziporphyrinato]nickel(II) (16b). Compound 16b was prepared
from benziporphyrin 11b (20 mg; 0.025 mmol) and nickel(II)
acetate using the previous procedure. Recrystallization from
chloroform-methanol gave the nickel complex (15.9 mg; 0.0186
mmol; 75%) as purple flakes, mp 275-276 °C; UV-vis (CHCl3):
6,11,16,21-Tetraphenylbenziporphyrin (8).13 Nitrogen was
slowly bubbled through a stirred solution of 1,3-bis(R-hydroxy-
phenylmethyl)benzene (0.290 g; 1.00 mmol) in 900 mL of
dichloromethane in a 1 L round-bottom flask that had been covered
with aluminum foil to protect the reaction from ambient light. A
septum was placed in the neck of the flask, and a nitrogen-filled
balloon was attached to maintain the inert atmosphere. Next, freshly
distilled pyrrole (0.208 mL; 3.00 mmol) and benzaldehyde (0.205
mL; 2.02 mmol) were added via syringe, followed by 0.20 mL of
boron trifluoride etherate. The resulting mixture was stirred for 2
h at room temperature. The initially colorless solution turned orange
and then became a deep red color. DDQ (750 mg) was added and
the mixture stirred for an additional 10 min. The dark solution was
evaporated under reduced pressure and the residue purified on a
Grade 3 basic alumina column eluting with dichloromethane.
Tetraphenylporphyrin and unidentified brown byproducts eluted
initially, followed by a dark green band corresponding to the title
benziporphyrin. Recrystallization from chloroform-methanol gave
the benziporphyrin (83 mg; 0.13 mmol; 13%) as a green powder,
mp >280 °C; 1H NMR (CDCl3): δ 6.54 (2H, d, J ) 4.8 Hz), 6.76
(2H, s), 7.00 (2H, dd, J ) 1.6, 8 Hz), 7.21 (2H, d, J ) 5.2 Hz),
7.31 (1H, t, J ) 8 Hz), 7.35 (1H, br t, J ) 1 Hz), 7.40-7.49 (20H,
1
λmax (logꢀ) 460 (4.59), 772 nm (4.14); H NMR (CDCl3): δ 1.45
(18H, s), 3.35 (6H, s), 6.17 (1H, s), 7.26 (2H, d, partially obscured
by CHCl3), 7.34-7.39 (2H, dt), 7.41-7.46 (4H, m), 7.53 (4H, d,
J ) 8 Hz), 7.56-7.59 (4H, m), 7.60-7.63 (6H, m), 7.65 (2H, d, J
) 5.2 Hz); 13C NMR (CDCl3): δ 31.7, 34.9, 55.7, 94.6, 116.7,
124.5, 125.9, 126.3, 126.8, 128.8, 131.5, 132.7, 133.0, 134.3, 134.8,
137.0, 144.4, 146.6, 150.3, 151.0, 154.9, 156.2, 173.0; EI MS
(70 eV): m/z (% rel int) 858 (3.5), 857 (8.4), 856 (11), 855 (17),
854 (10), 853 (15), 778 (4.1); HR MS: Calcd for C56H49N3NiO2:
853.3178. Found: 853.3182. Anal. Calcd for C56H49N3NiO2·1/4-
CHCl3: C, 76.38; H, 5.61; N, 4.75. Found: C, 76.08; H, 5.43; N,
4.76.
[2,4-Dimethoxy-3-methyl-6,11,16,21-tetraphenylbenziporphy-
rinato]nickel(II) (16c). The metallo-derivative was prepared from
12a (20.0 mg; 0.0286 mmol) by the procedure described above.
The crude product was purified on a Grade 3 basic alumina column
eluting with chloroform. The initial brownish-green fraction cor-
responded to the required complex. Recrystallization from chloro-
form-methanol afforded the nickel(II) porphyrinoid (16.0 mg;
0.0212 mmol; 74%) as a bronze powder, mp 288-290 °C; UV-
1
m), 10.30 (2H, br s); H NMR (TFA-CDCl3): δ 5.52 (1H, s),
7.10 (2H, dd, J ) 1, 4.8 Hz), 7.20 (2H, dd, J ) 1.2, 8.0 Hz), 7.26
(2H, s), 7.55-7.63 (14H, m), 7.70 (4H, t, J ) 7.6 Hz), 7.80-7.85
1
vis (CHCl3): λmax (logꢀ) 443 (4.67), 792 nm (4.11); H NMR
6490 J. Org. Chem., Vol. 72, No. 17, 2007

Tetraaryldimethoxybenziporphyrins
(CDCl3): δ 1.95 (3H, s), 3.21 (6H, s), 6.99 (2H, d, J ) 5.2 Hz),
7.37 (2H, s), 7.38-7.54 (16H, m), 7.55 (2H, d, J ) 5.2 Hz), 7.59-
7.63 (4H, m); 13C NMR (CDCl3): δ 10.6, 62.8, 117.0, 120.3, 127.0,
127.1, 127.6, 127.8, 128.9, 131.1, 131.3, 133.0, 133.1, 134.9, 136.2,
139.5, 143.1, 148.5, 152.6, 158.9, 170.2; EI MS (70 eV): m/z (%
rel int) 760.3 (3.5), 759.3 (8.3), 758.4 (6.4), 757.4 (10), 756.4 (2.8),
755.4 (2.7), 91.2 (100); HR MS: Calcd for C49H35N3NiO2 + 2H:
757.2239. Found: 757.2233. Anal. Calcd for C49H35N3NiO2·1/2-
CHCl3: C, 72.84; H, 4.38; N, 5.15. Found: C, 72.99; H, 4.63; N,
5.18.
[2,4-Dimethoxy-3-methyl-11,16-bis(4-tert-butylphenyl)-6,21-
diphenylbenziporphyrinato]nickel(II) (16d). The nickel complex
was prepared from 12b (20.0 mg; 0.0246 mmol) by the procedure
described above. Recrystallization from chloroform-methanol
afforded the nickel(II) porphyrinoid (16.0 mg; 0.0185 mmol; 75%)
as dark purple crystals, mp 272-273 °C; UV-vis (CHCl3): λmax
(logꢀ) 445 (4.65), 800 nm (4.08); 1H NMR (CDCl3): δ 1.43 (18H,
s), 1.95 (3H, s), 3.21 (6H, s), 7.02 (2H, d, J ) 5.2 Hz), 7.42 (2H,
s), 7.37-7.47 (6H, m), 7.49-7.55 (14H, m); 13C NMR (CDCl3):
δ 10.6, 31.7, 34.9, 62.8, 117.1, 120.3, 124.7, 127.0, 127.1, 129.2,
131.1, 131.3, 132.7, 133.1, 134.8, 135.9, 136.5, 143.2, 148.6, 150.5,
152.7, 153.6, 159.2, 169.9; EI MS (70 eV): m/z (% rel int) 873
(3.7), 872 (7.9), 871 (15), 870 (19), 869 (27), 868 (8.5), 867 (8.5),
792 (4.2); HR MS: Calcd for C57H51N3NiO2: 867.3335. Found:
867.3336. Anal. Calcd for C57H51N3NiO2·1/3CHCl3: C, 75.79; H,
5.69; N, 4.62. Found: C, 75.73; H, 5.51; N, 4.72.
(50 mg; 0.0715 mmol) and palladium(II) acetate (20 mg;
0.089 mmol) under the conditions described above. Recrystalliza-
tion from chloroform-methanol gave the palladium(II) complex
(41.9 mg; 0.0522 mmol; 73%) as dark purple crystals, mp
>300 °C; UV-vis (CHCl3): λmax (logꢀ) 349 (4.51), 454 (4.77),
557 (4.00), 859 nm (3.88); 1H NMR (CDCl3): δ 1.92 (3H, s), 3.22
(6H, s), 7.06 (2H, d, J ) 5.2 Hz), 7.28 (2H, s), 7.38-7.43 (2H,
dt), 7.46-54 (10H, m), 7.58 (2H, d, J ) 5.2 Hz), 7.60-7.67 (8H,
m); 13C NMR (CDCl3): δ 11.0, 63.2, 118.0, 120.9, 127.0, 127.6,
127.7, 129.3, 129.5, 131.3, 133.1, 133.2, 134.5, 140.3, 141.2, 144.3,
147.4, 152.3, 153.9, 157.5, 169.5; EI MS (70 eV): m/z (% rel int)
808 (3.1), 807 (6.8), 806 (5.7), 805 (11), 804 (7.9), 803 (10); HR
MS: Calcd for C49H35N3O2106Pd: 803.1764. Found: 803.1771.
Anal. Calcd for C49H35N3O2Pd‚1/10CHCl3: C, 72.25; H, 4.33; N,
5.15. Found: C, 72.32; H, 4.08; N, 4.80.
[2,4-Dimethoxy-3-methyl-11,16-bis(4-tert-butylphenyl)-6,21-
diphenylbenziporphyrinato]palladium(II) (17d). The palladium
complex was prepared under the foregoing conditions from 12b
(44.0 mg; 0.0542 mmol) and palladium(II) acetate (24.0 mg;
0.107 mmol). Recrystallization from dichloromethane-methanol
gave the palladium(II) complex (36.4 mg; 0.040 mmol; 74%) as
dark purple crystals, mp 248-250 °C; UV-vis (CHCl3): λmax (logꢀ)
1
355 (4.47), 420 (4.68), 453 (4.78), 869 (3.88); H NMR (CDCl3):
δ 1.45 (18H, s), 1.92 (3H, s), 3.23 (6H, s), 7.10 (2H, d, J )
5.2 Hz), 7.34 (2H, s), 7.39-7.43 (2H, dt), 7.46-7.50 (4H, m), 7.53
(4H, d, J ) 8 Hz), 7.56 (2H, d, J ) 5.2 Hz), 7.59 (4H, d, J )
8 Hz), 7.59-7.64 (4H, m); 13C NMR (CDCl3): δ 11.0, 31.7, 34.9,
63.2, 118.1, 121.0, 124.6, 127.0, 129.3, 129.8, 131.3, 133.0, 133.2,
134.4, 137.3, 140.9, 144.3, 147.4, 150.6, 152.5, 154.1, 157.8, 169.4;
HR EI MS: Calcd for C57H51N3O2106Pd: 913.3021. Found:
913.3016. Anal. Calcd for C57H51N3O2Pd‚1/10CHCl3: C, 73.87; H,
5.55; N, 4.53. Found: C, 74.03; H, 5.47; N, 4.55.
[2,4-Dimethoxy-6,11,16,21-tetraphenylbenziporphyrinato]-
palladium(II) (17a). A solution of 11a (20.3 mg; 0.0292 mmol)
and palladium(II) acetate (8.3 mg) in acetonitrile (20 mL) was
stirred under reflux for 2 h. During the course of the reaction, the
solution turned from a deep green to a brown color. The solution
was diluted with chloroform, washed with water, dried over sodium
sulfate, and evaporated under reduced pressure. The residue was
purified on a grade 3 basic alumina column eluting with chloroform,
and the organometallic derivative was collected as a brown band.
Recrystallization from chloroform-methanol gave the palladium-
(II) complex (19.0 mg; 0.0241 mmol; 82%) as dark purple crystals,
mp > 300 °C; UV-vis (CHCl3): λmax (logꢀ) 349 (4.65), 408 (4.67),
22-Acetoxy-2,4-dimethoxy-6,11,16,21-tetraphenylbenzipor-
phyrin (20a). Tetraphenyldimethoxybenziporphyrin 11a (100 mg;
0.146 mmol) was refluxed with silver(I) acetate (73 mg; 0.44 mmol)
in a 50/50 v/v mixture of chloroform and acetonitrile (100 mL) for
2 h. The solvent was evaporated and the residue purified on a grade
3 basic alumina column eluting with chloroform. The product eluted
as the first green fraction. Recrystallization from chloroform-
methanol gave the acetoxy derivative (84 mg; 0.113 mmol; 77%)
as turquoise flakes, mp >280 °C; UV-vis (1% Et3N-CHCl3): λmax
(logꢀ) 351 (4.54), 434 (4.72), 644 (sh, 4.19), 686 nm (4.30); UV-
vis (1% TFA-CHCl3): λmax (logꢀ) 317 (4.42), 464 (4.77), 786 (sh,
4.04), 849 nm (4.38); 1H NMR (CDCl3): δ 1.12 (3H, s), 3.40 (6H,
s), 6.35 (1H, s), 6.52 (2H, d, J ) 4.8 Hz), 6.93 (2H, s), 7.37-7.46
(14H, m), 7.50-7.53 (4H, m), 7.74-7.77 (4H, m), 8.89 (1H, br
1
463 (4.89), 556 (4.09), 599 (4.27), 736 (3.97), 812 nm (4.11); H
NMR (CDCl3): δ 3.35 (6H, s), 6.17 (1H, s), 7.30 (2H, d, J )
5.2 Hz), 7.37-7.42 (2H, dt), 7.45-7.50 (4H, m), 7.52 (2H, s),
7.52-7.57 (6H, m), 7.69-7.77 (8H, m), 7.74 (2H, d, J ) 4.8 Hz);
13C NMR (CDCl3): δ 55.8, 95.1, 117.9, 124.1, 126.3, 126.7, 127.5,
127.6, 129.0, 131.8, 132.7, 133.6, 134.0, 139.6, 140.9, 145.4, 145.7,
150.8, 154.8, 154.9, 171.7; EI MS (70 eV): m/z (% rel int) 795
(2.1), 794 (2.5), 793 (4.8), 792 (3.7), 791 (6.4), 790 (4.8), 789 (4.2),
788 (2.0), 716 (2.3), 714 (2.8, M+ - C6H5), 713 (2.0), 207 (100);
HR MS: Calcd for C48H33N3O2Pd: 789.1608. Found: 789.1614.
Anal. Calcd for C48H33N3O2Pd: C, 72.96; H, 4.21; N, 5.32.
Found: C, 72.50; H, 4.05; N, 5.17.
1
s); H NMR (TFA-CDCl3): δ 0.51 (3H, s), 3.50 (6H, s), 4.18
(1H, br s), 6.51 (1H, s), 7.25-7.27 (2H, dd, obscured by CHCl3),
7.68-7.78 (18H, m), 8.00-8.04 (6H, m), 8.44 (1H, br s); 13C NMR
(CDCl3): δ 20.2, 55.9, 96.3, 114.6, 117.5, 127.4, 127.6, 127.9,
128.0, 130.1, 130.8, 132.4, 132.8, 134.5, 137.8, 140.2, 142.4, 147.5,
157.3, 158.6, 169.2, 169.4; 13C NMR (TFA-CDCl3): δ 18.6, 56.8,
98.1, 109.7, 116.8, 118.0, 129.1, 129.3, 129.4, 131.0, 132.8, 133.6,
134.2, 134.5, 136.2, 136.8, 139.0, 142.6, 145.1, 149.7, 158.2, 162.7,
167.4; HR EI MS: Calcd for C50H37N3O4: 743.2784. Found:
743.2787. Anal. Calcd for C50H37N3O4·0.6CHCl3: C, 74.53; H, 4.64;
N, 5.15. Found: C, 74.76; H, 4.36; N, 5.08.
[2,4-Dimethoxy-11,16-bis(4-tert-butylphenyl)-6,21-diphenyl-
benziporphyrinato]palladium(II) (17b). Compound 17b was
prepared from 11b (50 mg; 0.0627 mmol) and palladium(II) acetate
(28.2 mg; 0.126 mmol) in acetonitrile (50 mL) under the conditions
described above. Recrystallization from chloroform-methanol gave
the palladium(II) complex (43.5 mg; 0.0483 mmol; 77%) as dark
purple crystals, mp 274-275 °C; UV-vis (CHCl3): λmax (logꢀ)
355 (4.60), 410 (4.64), 465 (4.86), 556 (4.12), 599 (4.22), 740
22-Acetoxy-2,4-dimethoxy-11,16-bis(4-tert-butylphenyl)-6,21-
diphenylbenziporphyrin (20b). Compound 20b was prepared from
11b (34.2 mg; 0.0428 mmol) and silver(I) acetate (23 mg;
0.15 mmol) in acetonitrile (80 mL) under the conditions described
above. Recrystallization from dichloromethane-methanol gave the
acetoxybenziporphyrin (23.4 mg; 0.0273 mmol; 64%) as dark purple
crystals, mp 215-216 °C; UV-vis (1% Et3N-CHCl3): λmax (logꢀ)
353 (4.53), 438 (4.73), 653 (sh, 4.18), 699 nm (4.31); UV-vis (1%
TFA-CHCl3): λmax (logꢀ) 320 (4.37), 359 (4.36), 449 (4.73), 489
(4.73), 677 (3.81), 881 nm (4.42); 1H NMR (CDCl3): δ 1.10 (3H,
s), 1.45 (18H, s), 3.40 (6H, s), 6.34 (1H, s), 6.55 (2H, d, J )
4.8 Hz), 7.00 (2H, s), 7.35-7.45 (16H, m), 7.75 (4H, d, J )
1
(4.02), 815 nm (4.12); H NMR (CDCl3): δ 1.45 (18H, s), 3.35
(6H, s), 6.17 (1H, s), 7.34 (2H, d, J ) 4.8 Hz), 7.39 (2H, t, J ) 7.4
Hz), 7.48 (4H, t, J ) 7.6 Hz), 7.76 (4H, d), 7.58 (2H, s, overlapped
with previous signal), 7.67-7.74 (10H, m); 13C NMR (CDCl3): δ
31.7, 34.9, 55.8, 95.1, 118.0, 124.1, 124.4, 126.3, 126.7, 129.3,
131.8, 132.8, 133.4, 133.9, 137.9, 139.4, 145.5, 145.8, 150.4, 151.0,
155.1, 171.5; HR EI MS: Calcd for C56H49N3O2Pd: 901.2860.
Found: 901.2870. Anal. Calcd for C56H49N3O2Pd·1/10CHCl3: C,
73.69; H, 5.41; N, 4.59. Found: C, 73.69; H, 5.24; N, 4.53.
[2,4-Dimethoxy-3-methyl-6,11,16,21-tetraphenylbenziporphy-
rinato]palladium(II) (17c). The complex was prepared from 12a
J. Org. Chem, Vol. 72, No. 17, 2007 6491

Lash et al.
1
7 Hz), 8.85 (1H, br s); H NMR (TFA-CDCl3): δ 0.48 (3H, s),
Crystal Structure Determination of 16a. X-ray quality crystals
of 16a were obtained by vapor diffusion of hexanes into a 1,2-
dichloroethane solution followed by slow evaporation. A black
block thereby obtained of approximate dimensions 0.38 × 0.28 ×
0.25 mm3 was affixed to a glass fiber using Paratone-N oil and
transferred to a Bruker P4/R4/SMART 1000 CCD diffractometer.
The X-ray diffraction data were collected at -80 °C using Mo-
Ka (λ ) 0.71073 Å) radiation. Data collection and cell refinement
were performed using SMART.34 The unit cell parameters were
obtained from a least-squares refinement of 4308 centered reflec-
tions. The nickel complex 16a was found to crystallize in the
monoclinic crystal system with the following unit cell parameters:
a ) 9.968(1) Å, b ) 18.833(3) Å, c ) 18.415(3) Å, â ) 95.555-
(3)°, Z ) 4. The systematic absences indicated the space group to
be P21/c (no. 14).35 A total of 20720 reflections were collected, of
1.47 (18H, s), 3.49 (6H, s), 4.11 (1H, br s), 6.51 (1H, s), 7.30 (2H,
dd, J ) 1.2, 5.2 Hz), 7.65 (4H, d, J ) 8 Hz), 7.69 (2H, s), 7.70-
7.78 (10H, m), 8.00 (2H, dd, J ) 1.6, 5.2 Hz), 8.01-8.04 (4H, m),
8.32 (1H, br s); 13C NMR (CDCl3): δ 20.2, 31.7, 34.8, 55.9, 96.3,
114.5, 117.5, 124.8, 127.5, 127.8, 130.1, 131.1, 132.47, 132.52,
134.4, 137.3, 137.4, 142.5, 147.6, 150.3, 157.35, 158.5, 169.46,
169.50; 13C NMR (TFA-CDCl3): δ 18.6, 31.4, 35.3, 56.8, 98.1,
108.6, 117.0, 117.9, 126.4, 129.2, 129.4, 132.7, 133.5, 133.6, 134.2,
134.5, 136.5, 139.0, 141.9, 145.1, 149.5, 154.9, 158.2, 162.7, 167.3;
EI MS (70 eV): m/z (% rel int) 860 (3.3), 859 (13), 858 (40), 857
(63), 856 (4.9), 855 (M+, 5.3), 815 (10), 281 (100); HR EI MS:
Calcd for C58H53N3O4 + 2H: 857.4192. Found: 857.4186. Anal.
Calcd for C58H53N3O4‚0.3CHCl3: C, 78.51; H, 6.02; N, 4.71.
Found: C, 78.36; H, 6.08; N, 4.74.
22-Acetoxy-2,4-dimethoxy-3-methyl-6,11,16,21-tetraphenyl-
benziporphyrin (20c). Acetoxy derivative 20c was prepared from
12a (100 mg; 0.143 mmol) and silver(I) acetate (70 mg; 0.42 mmol)
in acetonitrile (60 mL) and chloroform (30 mL) under the conditions
described above. Recrystallization from chloroform-methanol gave
the acetoxybenziporphyrin (69.4 mg; 0.0917 mmol; 64%) as purple
flakes, mp 242-243 °C; UV-vis (1% Et3N-CHCl3): λmax (logꢀ)
334 (4.43), 422 (4.78), 650 (sh, 4.17), 693 nm (4.27); UV-vis (1%
TFA-CHCl3): λmax (logꢀ) 474 (4.91), 662 (3.69), 873 nm (4.37);
1H NMR (CDCl3): δ 1.29 (3H, s), 2.01 (3H, s), 3.21 (6H, s), 6.49
(2H, d, J ) 4.8 Hz), 6.84 (2H, s), 7.38 (2H, d, J ) 4.4 Hz), 7.40-
7.49 (16H, m), 7.73-7.76 (4H, m), 9.39 (1H, br s); 1H NMR
(TFA-CDCl3): δ 0.93 (3H, s), 2.00 (3H, s), 3.16 (6H, s), 5.72
(1H, br s), 7.16 (2H, d, J ) 5.2 Hz), 7.46 (2H, d, J ) 1.6 Hz),
7.58-7.67 (10H, m), 7.71-7.77 (6H, m), 7.91-7.96 (6H, m), 10.00
(1H, br s); 13C NMR (CDCl3): δ 10.5, 20.3, 60.9, 114.6, 119.7,
124.67, 124.69, 127.5, 127.9, 128.1, 128.5, 130.3, 131.3, 132.3,
132.6, 134.5, 138.1, 140.0, 141.8, 147.9, 157.2, 157.7, 169.9, 170.0;
13C NMR (TFA-CDCl3): δ 11.4, 19.0, 62.6, 107.1, 117.1, 124.1,
127.9, 129.3, 129.5, 130.1, 130.9, 133.0, 133.8, 134.01, 134.04,
135.9, 137.3, 139.1, 143.7, 145.6, 151.0, 160.4, 161.6; EI MS
(70 eV): m/z (% rel int) 762 (2.4), 761 (8.7), 760 (31), 759 (57),
745 (13); HR EI MS: Calcd for C51H39N3O4: 757.2940. Found:
757.2938. Anal. Calcd for C51H39N3O4·2/3CHCl3: C, 74.10; H, 4.77;
N, 5.02. Found: C, 74.23; H, 4.56; N, 4.81.
6,23-Dihydro-2,4-dimethoxy-6,11,16,21-tetraphenylbenzipor-
phyrin (19a). A solution of sodium borohydride (50 mg) in ethanol
(15 mL) was added to a stirred solution of benziporphyrin 11a
(20.3 mg; 0.0296 mmol) in chloroform (25 mL) and the mixture
stirred at room temperature overnight. The mixture was washed
with water, back extracted with chloroform, and evaporated under
reduced pressure. The residue was chromatographed with dichlo-
romethane on a grade 3 basic alumina column, and the product
was collected as a blue-green fraction that eluted before a green
band corresponding to residual starting material. Recrystallization
from chloroform-methanol gave the dihydrobenziporphyrin (13.8
mg; 0.0201 mmol; 68%) as dark purple crystals, mp 218 °C, dec;
UV-vis (1% Et3N-CHCl3): λmax (log ꢀ) 414 (4.51), 630 (sh, 4.23),
672 nm (4.37); UV-vis (1% TFA-CHCl3): λmax (log ꢀ) 324 (4.32),
408 (4.63), 487 (4.66), 665 (3.80), 885 nm (4.16); 1H NMR
(CDCl3): δ 3.37 (3H, s), 3.89 (3H, s), 5.30 (1H, s), 6.07 (1H, s),
6.33 (1H, d, J ) 4.4 Hz), 6.42 (1H, s), 6.44 (1H, d, J ) 3.6 Hz),
6.50 (1H, d, J ) 3.6 Hz), 6.59-6.61 (2H, m), 6.73 (1H, d, J ) 4.4
Hz), 7.02 (1H, d, J ) 5.6 Hz), 7.10 (2H, d, J ) 7.6 Hz), 7.15 (1H,
t, J ) 7 Hz), 7.21-7.42 (16H, m) 7.82 (1H, br s), 9.86 (1H, br s);
1H NMR (TFA-CDCl3): δ 0.93 (3H, s), 2.00 (3H, s), 3.16 (6H,
s), 5.72 (1H, br s), 7.16 (2H, d, J ) 5.2 Hz), 7.46 (2H, d, J )
1.6 Hz), 7.58-7.67 (10H, m), 7.71-7.77 (6H, m), 7.91-7.96 (6H,
m), 10.00 (1H, br s); 13C NMR (CDCl3): δ 42.6, 56.2, 56.4, 97.3,
108.3, 112.3, 118.9, 119.9, 121.3, 121.5, 122.8, 126.4, 126.5, 126.9,
127.4, 127.7, 128.0, 128.2, 128.5, 128.6, 128.7, 129.1, 130.2, 131.6,
132.3, 132.6, 134.2, 135.1, 139.7, 140.4, 140.9, 142.0, 142.6, 142.7,
147.3, 151.4, 156.6, 158.2, 167.1; HR EI MS: Calcd for
C48H37N3O2: 687.2886. Found: 687.2899.
2
2
which 7013 were unique, and 5478 were observed Fo > 2s(Fo ).
Limiting indicies were as follows: -12 e h e 12, -23 e k e 20,
-22 e l e 22. Data reduction were accomplished using SAINT.34b
The data were corrected for absorption through use a face-indexing
procedure.
Solution and data analysis were performed using the WinGX
software package.36 The structure of 16a was solved by direct
methods using the program SIR200437 and the refinement was
completed using the program SHELX-97.38 All non-hydrogen atoms
were refined anisotropically. Hydrogen atoms were assigned
positions based on the geometries of their attached carbon atoms.
Hydrogen atoms were given thermal parameters of 20% greater
than those of the attached atoms. Full-matrix least-squares refine-
ment on F2 led to convergence, (∆/σ)max ) 0.001, (∆/σ)mean
0.0000, with R1 ) 0.0676 and wR2 ) 0.1895 for 5478 data with
)
2
2
Fo > 2s(Fo ) using 0 restraints and 487 parameters. A final
difference Fourier synthesis showed features in the range of ∆Fmax
) 1.86 e-/Å3 (0.87 Å from Ni) to ∆Fmin ) -1.31 e-/Å3 (0.88 Å
from Ni) which were deemed of no chemical significance. Molec-
ular diagrams were generated using ORTEP-3.39 X-ray structural
data has been deposited with the CCDC.40
Acknowledgment. This material is based upon work sup-
ported by the Arnold and Mabel Beckman Foundation ‘Beckman
Scholars Program’ (to J.T.S.), the National Science Foundation
under Grant No. CHE-0616555, and the Petroleum Research
Fund, administered by the American Chemical Society. We also
thank Dr. Robert McDonald and The University of Alberta
Structure Determination Laboratory for collecting the low-
temperature CCD X-ray data.
Supporting Information Available: Crystallographic data for
1
16a in CIF format and copies of the UV-vis, H NMR, and 13C
NMR spectra for selected compounds. This material is available
free of charge via the Internet at http://pubs.acs.org.
JO070947K
(34) (a) Bruker SMART 1000 CCD software package; Bruker Advanced
X-ray Solutions: Madison, WI, 1999. (b) Bruker SAINT Integration
Software for Single Crystal Data frames - h,k,l, intensity; Bruker Advanced
X-ray Solutions: Madison, WI, 1999. (c) Bruker. SADABS-Empirical
absorption correction produces; Bruker Advanced X-ray Solutions: Madi-
son, WI, 1999.
(35) McArdle, P. J. Appl. Crystallogr. 1996, 29, 306.
(36) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837.
(37) Burla, M. C.; Caliandro, R.; Camalli, M.; Carrozzini, B.; Cascarano,
G. L.; De Caro, L.; Giacovazzo, C.; Polidori, G.; Spagna, R. J. Appl.
Crystallog. 2005, 38, 381.
(38) Sheldrick, G. M., SHELX-97, Programs for Crystal Structure
Analysis (Release 97-2), Institu¨t fu¨r Anorganische Chemie der Universita¨t,
Tammanstrasse 4, D-3400 Go¨ttingen, Germany, 1998.
(39) Farrugia, L. J. J. Appl. Crystallogr. 1997, 30, 565.
(40) Crystallographic data (excluding structure factors) for 16a has been
deposited with the Cambridge Crystallographic Data Center as supplemen-
tary publication number CCDC 645634. Copies of this data can be obtained,
free of charge, on application to CCDC, 12 Union Road, Cambridge CB2
IEZ, UK [fax: +44 (0)12233 336033 or e-mail: deposit@ccdc.cam.ac.uk].
6492 J. Org. Chem., Vol. 72, No. 17, 2007