Preparation of Six Isomeric Bis-acylporphyrins with Chromophores Reaching the Near-Infrared via Intramolecular Friedel-Crafts Reaction

Article abstract of DOI:10.1021/jo035108m

We describe the preparation of six diketones based on the frameworks of five bis-naphthoporphyrins and one perinaphthoporphyrin. All diketones derive from meso-tetraarylporphyrins having incorporated two carbonyl groups, each one connected to one β-pyrrole carbon and one ortho carbon atom from a meso-aryl group. These compounds were all produced in good yield by intramolecular Friedel-Crafts acylation, either from porphyrins meso-substituted by o-carboxyphenyl or o,o′-dicarboxyphenyl substituents or from porphyrins bearing carboxy groups attached to the pyrrolic β-positions. Although the former reaction does not show significant regioselectivity when run on nickel complexes, the opposite is true for the corresponding free bases. All diketones show a spectacular bathochromic shift of the UV-vis absorption, the longest wavelength bands absorbing in the 700-825 nm range. Two compounds were structurally characterized by X-ray diffraction. In the case of the diketone, whose carbonyl groups are attached to vicinal pyrrolic β-positions, a significant intermolecular interaction between the two carbonyl groups and an aromatic hydrogen atom was detected.

Full text of DOI:10.1021/jo035108m

P r ep a r a tion of Six Isom er ic Bis-a cylp or p h yr in s w ith
Ch r om op h or es Rea ch in g th e Nea r -In fr a r ed via In tr a m olecu la r
F r ied el-Cr a fts Rea ction
Se´bastien Richeter,† Christophe J eandon,† Nathalie Kyritsakas,‡ Romain Ruppert,*,† and
Henry J . Callot*,†
Laboratoire de Chimie des Porphyrines, UMR 7123 CNRS, Universite´ Louis Pasteur,
Faculte´ de Chimie, 1 rue Blaise Pascal, 67000 Strasbourg, France, and Service Commun de Rayons X,
Universite´ Louis Pasteur, Faculte´ de Chimie, 4 rue Blaise Pascal, 67000 Strasbourg, France
callot@chimie.u-strasbg.fr
Received J uly 29, 2003
We describe the preparation of six diketones based on the frameworks of five bis-naphthoporphyrins
and one perinaphthoporphyrin. All diketones derive from meso-tetraarylporphyrins having
incorporated two carbonyl groups, each one connected to one â-pyrrole carbon and one ortho carbon
atom from a meso-aryl group. These compounds were all produced in good yield by intramolecular
Friedel-Crafts acylation, either from porphyrins meso-substituted by o-carboxyphenyl or o,o′-
dicarboxyphenyl substituents or from porphyrins bearing carboxy groups attached to the pyrrolic
â-positions. Although the former reaction does not show significant regioselectivity when run on
nickel complexes, the opposite is true for the corresponding free bases. All diketones show a
spectacular bathochromic shift of the UV-vis absorption, the longest wavelength bands absorbing
in the 700-825 nm range. Two compounds were structurally characterized by X-ray diffraction. In
the case of the diketone, whose carbonyl groups are attached to vicinal pyrrolic â-positions, a
significant intermolecular interaction between the two carbonyl groups and an aromatic hydrogen
atom was detected.
CHART 1. Str u ctu r e of Oxon a p h th op or p h yr in s (1
a n d 2) a n d th e Cor r esp on d in g En a m in ok eton es (3
a n d 4)
In tr od u ction
The tetrapyrrolic chromophores, found in many natural
photosynthetic systems, have also been used by synthetic
chemists as starting compounds to build up molecules
possessing extended π-conjugation.1 These molecules are
promising for potential applications in photodynamic
therapy or as models for the photosynthetic reaction cen-
ters and antenna arrays. In the field of material science,
improvement of the photochemical or electrochemical
properties might lead to new molecular materials.
For the widely used meso-tetraarylporphyrins, the
extension of the chromophore can be easily obtained by
fusing one pyrrole and a neighboring aryl group with a
keto function, thus leading to the so-called oxonaphtho-
porphyrins 1 or 2 (Chart 1).2-4 This addition of two
unsaturated rings in the plane of the porphyrin and the
corresponding extension of the conjugation induce inter-
esting optical properties: the nickel complex of an
oxonaphthoporphyrin like 2 shows absorption as far as
650 nm, approximatively 100 nm longer wavelength than
simple nickel porphyrins. Performing this kind of ring
fusion twice was therefore expected to lead to further
improvement of the optical properties of the porphyrin
macrocycles. To our knowledge, only two examples of
porphyrins meso+â fused with two conjugated rings have
† Laboratoire de Chimie des Porphyrines, Universite´ Louis Pasteur.
‡ Service Commun de Rayons X, Universite´ Louis Pasteur.
(1) Vicente, M. G. H.; J aquinod, L.; Smith, K. M. Chem. Commun.
1999, 1771. Anderson, H. L. Chem. Commun. 1999, 2323. Arnold, D.
P. Synlett 2000, 296. Burrell, A. K.; Officer, D. L.; Plieger, P. G.; Reid,
D. C. W. Chem. Rev. 2001, 101, 2751. Imamura, T.; Fukushima, K.
Coord. Chem. Rev. 2000, 198, 133. Wojaczynski, J .; Latos-Grazynski,
L. Coord. Chem. Rev. 2000, 204, 113. Sanders, J . K. M. In The
Porphyrin Handbook; Kadish, K. M., Smith, K. M., Guilard, R., Eds.;
Academic Press: Boston, MA, 2000; Vol. 3, p 347. For additional
references see also references cited in ref 8 in this paper.
(2) Henrick, K.; Owston, P. G.; Peters, R.; Tasker, P. A.; Dell, A.
Inorg. Chim. Acta 1980, 45, L 161.
(3) Callot, H. J .; Schaeffer, E.; Cromer, R.; Metz, F. Tetrahedron
1990, 46, 5253.
(4) Ishkov, Y. V.; Zhilina, Z. I. Zh. Org. Khim. 1995, 31, 136.
10.1021/jo035108m CCC: $25.00 © 2003 American Chemical Society
Published on Web 10/28/2003
9200
J . Org. Chem. 2003, 68, 9200-9208

Preparation of Isomeric Bis-acylporphyrins
CHART 2. Dim er s Obta in ed by Lin k in g Tw o
En a m in ok etop or p h yr in s by Meta l Ion s
pared by intramolecular cyclization of functionalized side
chains,13 but simple Friedel-Crafts acylation of porphy-
rins was little explored.14 Similar chemistry of meso-
tetraarylporphyrins was virtually unknown until re-
cently.15 An additional difficulty arises when one wishes
to obtain both free bases and metal complexes of the
target porphyrins, since Friedel-Crafts chemistry is only
compatible with a limited set of stable metal complexes.
The demetalation of these complexes may also interfere
with the survival of the new functional groups.
There are six possible diketones illustrated by struc-
tures 5-10 (Chart 3), three of them (5-7) with the
carbonyl groups attached to vicinal meso-phenyl rings,
two (8 and 9) with the carbonyl groups attached to
opposite meso-phenyl rings, and one (10) with the two
carbonyl groups attached to the same meso-phenyl ring.
Out of the six possible diketones, five (illustrated by 5,
6, 8, 9, and 10) represent potential starting materials
for the required bis-enaminoketones, while the last one
(7) shows a potentially interesting relationship between
the two very close carbonyl groups.
been obtained so far.5,6 Both compounds have one pyrrole
connected with the two adjacent phenyl groups either by
five- or six-membered rings, but the extension of the
conjugated system only produced moderate modifications
of the electronic spectra.
On the other hand, we have demonstrated7,8 that
enaminoketoporphyrins such as 3 or 4, obtained from the
corresponding ketones by amination, could be used as
chelating ligands for metal ions. Assembling two such
molecules around a metal ion leads to a dimeric porphy-
rin. These dimers (Chart 2) show an extension of the
chromophore and the splitting of the electrochemical
waves, thus demonstrating that the metal ion connection
has brought significant interactions between the two
porphyrins in the ground state.
In this paper, we describe the preparation and char-
acterization of all six porphyrin diketone frameworks, as
nickel complexes, as well as various attempts to prepare
the corresponding free bases. We also demonstrate that
several routes leading to these ketones are available,
taking advantage of performing the acylation step either
from meso-aryl groups to the porphyrin ring, but also
from the porphyrin ring to the aryl groups. We present
also the X-ray structures of two diketones and the
electronic spectra of these compounds, demonstrating
that, in these cases, the extension of the aromatic system
leads to major bathochromic shifts.
Bis-enaminoketones would allow the complexation of
two metals at the periphery of one porphyrin ring and
to build higher oligomers. It was thus useful to carry out
the synthesis of porphyrins bearing two peripheral fused
benzocyclohexenone fragments.9
The classical method for preparing such ketones, acid-
catalyzed condensation of a â-formyl group onto a meso-
aryl ring, is a very efficient cyclization procedure, giving
a 1:1 mixture of the ketone and reduced species in ca.
90% yield. It suffers from several drawbacks when
extended to higher homologues: the formylation produces
several di- or polyaldehydes10 and the subsequent cy-
clization should lead to complex mixtures of diketones,
and monoketones, along with numerous reduced species.
To avoid these difficulties, we had to develop synthetic
routes based on a different reaction sequence, and we
selected the Friedel-Crafts acylation. This reaction has
been already illustrated in the polyalkylporphyrin se-
ries.11,12 Several ketocycloalkanoporphyrins were pre-
Resu lts a n d Discu ssion
Syn th esis of Keton es fr om P or p h yr in m eso-Ben -
zoa tes (Sch em e 1). Condensation of o-carbomethoxy-
benzaldehyde, 3,5-di-tert-butylbenzaldehyde, and pyrrole
under Lindsey’s conditions16 gave a mixture of all possible
esters. Diesters 11 and 12 are both present as RR and
Râ atropisomers and were chromatographically isolated
and transformed into the nickel complexes by reaction
with nickel acetylacetonate in refluxing toluene. These
diesters were hydrolyzed with LiOH in water-dioxane
solution. The crude lithium salts were then converted into
the acid chlorides (oxalyl chloride in benzene) and,
without purification, cyclized in benzene using SnCl4 as
Lewis acid. The resulting nickel complexes of diketones
5 (24%), 6 (18%), and 7 (44%) (prepared from the 5,10
isomer; total yield 86%) as well as 8 (36%) and 9 (40%)
(prepared from the 5,15 isomer; total yield 76%) were
separated chromatographically.
(5) Barloy, L.; Dolphin, D.; Dupre´, D.; Wijesekera, T. P. J . Org.
Chem. 1994, 59, 7976.
(6) Aihara, H.; J aquinod, L.; Nurco, D. J .; Smith, K. M. Angew.
Chem., Int. Ed. 2001, 40, 3439. Nath, M.; Huffman, J . C.; Zaleski, J .
M. Chem. Commun. 2003, 858.
(7) Richeter, S.; J eandon, C.; Ruppert, R.; Callot, H. J . Chem.
Commun. 2001, 91.
(8) Richeter, S.; J eandon, C.; Gisselbrecht, J .-P.; Ruppert, R.; Callot,
H. J . J . Am. Chem. Soc. 2002, 124, 6168.
(9) Richeter, S.; J eandon, C.; Ruppert, R.; Callot, H. J . Chem.
Commun. 2002, 266.
(10) Silva, A. M. G.; Faustino, M. A. F.; Silva, T. M. P. C.; Neves,
M. G. P. M. S.; Tome´, A. C.; Silva, A. M. S.; Cavaleiro, J . A. S. J . Chem.
(13) Clezy, P. S.; Prashar, J . K. Austr. J . Chem. 1990, 43, 825. Clezy,
P. S.; J enie, U.; Prashar, J . K. Austr. J . Chem. 1990, 43, 839.
(14) Brockmann, H., J r.; Bliesener, K.-M.; Inhoffen, H. H. Liebigs
Ann. Chem. 1968, 718, 148. J eandon, C.; Bauder, C.; Callot, H. J .
Energy Fuels 1990, 4, 665 and references cited therein.
(15) J eandon, C.; Ruppert, R.; Richeter, S.; Callot, H. J . Org. Lett.
2003, 5, 1487.
(16) Lindsey, J . S.; Schreiman, I. C.; Hsu, H. C.; Kearney, P. C.;
Marguerettaz, A. M. J . Org. Chem. 1987, 52, 827. Littler, B. J .; Ciringh,
Y.; Lindsey, J . S. J . Org. Chem. 1999, 64, 2864. Lindsey, J . S. In The
Porphyrin Handbook; Kadish, K. M., Smith, K. M., Guilard, R., Eds.;
Academic Press: Boston, MA, 2000; Vol. 1, p 45.
Soc., Perkin Trans.
1 2002, 1774. Mirinov, A. F.; Grin, M. A.;
Moskal’chuk, T. V.; Shashkov, A. S.; Lokshin, B. V. Mendeleev
Commun. 2002, 5, 204.
(11) Vicente, M. G. H. In The Porphyrin Handbook; Kadish, K. M.,
Smith, K. M., Guilard, R., Eds.; Academic Press: Boston, MA, 2000;
Vol. 1, p 149.
(12) J aquinod, L. In The Porphyrin Handbook; Kadish, K. M., Smith,
K. M., Guilard, R., Eds; Academic Press: Boston, MA, 2000; Vol. 1, p
201.
J . Org. Chem, Vol. 68, No. 24, 2003 9201

Richeter et al.
CHART 3. Str u ctu r e of th e Six P or p h yr in Dik eton es 5-10
SCHEME 1. Gen er a l Rou te to Dik eton es 5-9 (M )
Ni, Ar ) 3,5-Di-ter t-bu tylp h en yl)
without isolating the bromoporphyrins, but taking ad-
vantage of the ease of separation of the polycyanopor-
phyrins, this route leads efficiently to the mono- to
tetracyano-meso-tetraarylporphyrins substituted on two
opposite pyrroles.
The feasibility of this route to porphyrin ketones was
tested from monocyano-H2TPP (TPP ) anion of meso-
tetraphenylporphyrin) (Scheme 2). This compound was
obtained as the copper complex 13 (Ar ) phenyl) when
bromoporphyrin free bases were treated with cuprous
cyanide. There is no need to demetalate the complex,
because its hydrolysis in AcOH + 48% aqueous HBr gave
quantitatively acid 14 (Ar ) phenyl) as the free base. The
crude acid was then treated in the usual way (metalation
with nickel, followed by treatment with oxalyl chloride
and SnCl4) to yield the monoketone 1 (90% from 13),
confirming that both routes are available.
Alternatively, and in order to test different conditions,
possibly compatible with acid-sensitive complexing met-
als, the cyclization of the corresponding mixed anhydride
was tested. The nickel complex of acid 14 was treated
with triethylamine and ethyl chloroformate. The crude
mixed anhydride was cyclized either with BF3 etherate
or zinc chloride to yield ketone 1 (M ) Ni, Ar ) phenyl;
32%) (Scheme 2).
Diketones 5 and 9 are the only isomers accessible from
â-dicyanoporphyrins, since due to the regioselectivity of
the bromination reaction,18 only two dibromoporphyrins
(2,12 and 2,13 isomers) are produced. The reaction
sequence was run on the mixture of the two dicyanopor-
phyrins 15 and 16 (meso-phenyl series), since we ob-
served that the separation was easier to perform at the
last step. Hydrolysis and metalation gave the nickel
diacids, which were then treated with oxalyl chloride and
SnCl4. The crude mixture of diketones was then sepa-
At this stage, it should be noted that, while 5, 6, 8,
and 9 were eluted from silica gel with hexane-CH2Cl2
mixtures, the vicinal diketone 7 was very strongly
adsorbed and required AcOEt + 0.1% AcOH.
The same reaction sequence was applied to porphyrins
with other meso-aryl groups. In particular, crystals
suitable for an X-ray diffraction study of 8 could be
obtained with 2,6-dichlorophenyl as meso-aryl group (M
) Ni, see below for structural data).
Syn th esis of Mon o- a n d Dik eton es fr om â-Cya n -
op or p h yr in s. The second route requires that carbox-
ylic acids should be located at â-pyrrolic positions. They
can be prepared from â-cyanoporphyrins which are
available via bromination17,18 of porphyrin free bases
followed by reaction with cuprous cyanide.17,19 When run
(17) Callot, H. J . Bull. Soc. Chim. Fr. 1974, 1492.
(18) Crossley, M. J .; Burn, P. L.; Chew, S. S.; Cuttance, F. B.;
Newsom, I. A. J . Chem. Soc., Chem. Commun. 1991, 1564.
(19) J aquinod, L.; Khoury, R. G.; Shen, K. M.; Smith, K. M.
Tetrahedron 1999, 55, 13151.
9202 J . Org. Chem., Vol. 68, No. 24, 2003

Preparation of Isomeric Bis-acylporphyrins
SCHEME 2. Syn th esis of Mon o- a n d Dik eton es fr om â-Cya n op or p h yr in s (Ar ) P h en yl)
SCHEME 3
rated by fractional crystallization and chromatography
on silica gel to give 5 (M ) Ni, Ar ) phenyl; 27%) and 9
(M ) Ni, Ar ) phenyl; 30%).
strong acid, proved to be inefficient with the nickel
diketones. Even in pure sulfuric acid or methanesulfonic
acid, most starting material was recovered unchanged,
while under more drastic conditions (hot acids), decom-
position occurred. This lack of reactivity of the nitrogen
atoms is best explained by the protonation of both
carbonyl groups, which will inhibit any further protona-
tion of the porphyrin. At this stage, there remained two
possibilities: either to cyclize a carboxylic acid derivative
as the free base porphyrin or to protect the porphyrin
core with an acid-sensitive metal, like zinc, and find
nonacidic cyclization conditions.
Preliminary tests on the zinc complex of acid 14
derivatives failed: attempted cyclization of the mixed
anhydride with zinc chloride did not give ketone 1. The
direct reaction of this acid with zinc chloride (which also
metalated the porphyrin ring) in refluxing chlorobenzene
(at lower temperatures, no reaction occurred) only gave
traces of ketonic material accompanied by extensive
decarboxylation. However, under similar conditions, the
corresponding nickel complex 14 (M ) Ni) showed that
the direct cyclization to ketone 1 (M ) Ni, Ar ) phenyl)
occurred albeit in low yield (15% cyclized material vs 57%
decarboxylation).
P r ep a r a tion of Dik eton e 10 (Sch em e 3). Since no
simple route to the appropriate â-dicyanoporphyrin
(2,18 isomer) was available, we carried out the prepara-
tion of 10 via the meso-aryl to porphyrin cyclization. A
reaction sequence similar to one described in the litera-
ture20 was followed starting with meso-2,6-dichlorophenyl
substituted porphyrin 17 to introduce carboxylic acids via
cyano groups and hydrolysis. Porphyrin 17 was obtained
in 20% yield by reacting 2,6-dichlorobenzaldehyde, 3,5-
di-tert-butylbenzaldehyde, and pyrrole. The cyanation
reaction was carried out in 51% yield by reacting 17 with
cuprous cyanide in N-methylpyrrolidinone at 250 °C in
a sealed tube. Hydrolysis of the cyano groups and
simultaneous demetalation of 18 in aqueous sulfuric acid,
metalation with nickel (II), treatment with oxalyl chlo-
ride, and a Friedel-Crafts reaction gave diketone 10
(37% from copper dicyanoporphyrin 18).
Syn th esis of Dik eton e F r ee Ba ses. The general
method for demetalating porphyrins, treatment with a
(20) Nakagawa, H.; Nagano, T.; Higuchi, T. Org. Lett. 2001, 3, 1805.
J . Org. Chem, Vol. 68, No. 24, 2003 9203

Richeter et al.
F IGURE 1. Two views of diketone 8 (Ar ) 2,6-Cl2Ph): (a) all hydrogen atoms omitted for clarity; (b) both meso-phenyl and all
hydrogen atoms omitted for clarity).
SCHEME 4. P r ep a r a tion of Dik eton e 9 a s F r ee Ba se (Ar ) 3,5-Di-ter t-bu tylp h en yl)
The direct cyclization of an appropriately substituted
free base porphyrins was finally carried out under the
conditions used by several groups21,22 to build rings fused
to pyrroles (Scheme 4). The reaction was first tested with
monoesters and then applied to diesters 11 and 12.
Diester 11, as free base, was treated with excess boron
tribromide in CH2Cl2 (1 M) and the reaction mixture
hydrolyzed under basic conditions. Diketone 6 (free base,
Ar ) 3,5-di-tert-butylphenyl), but not the other possible
isomers 5 and 7, was obtained in moderate yield (11%).
Under the same conditions, diester 12 produced only
diketone 9 (free base, Ar ) 3,5-di-tert-butylphenyl) in 20%
yield. The remaining porphyrinic material mostly consists
of acids arising from the esters and monocyclized com-
pounds. This reaction shows a high selectivity toward
only one diketone in each series. We suggest that, in the
presence of excess BBr3, a boron complex forms rapidly.
Since all known porphyrin boron complexes involve two
boron atoms and thus lack the high symmetry of most
porphyrin metal derivatives,23 the pyrrolic carbon atoms
are no longer equivalent and should show different
reactivities. The carbonyl oxygen-boron bonds, either in
the starting material (ester/central or external boron
interaction) or in the monocyclized intermediate (same
interactions or ketone/boron bond) are also expected to
polarize the π-system and to exert additional effects on
the selectivity of the acylation reaction.
Str u ctu r a l Da ta for Dik eton es 7 a n d 8. Single
crystals suitable for X-ray studies could be grown for
diketones 7 (M ) Ni, Ar ) 3,5-di-tert-butylphenyl) and 8
(M ) Ni, Ar ) 2,6-dichlorophenyl). However, due to
disorder observed for the tert-butyl groups and for the
solvents included in the unit cell, the quality of the
structural data for diketone 7 is rather low. Both por-
phyrins are saddle-shaped as shown by the angles
determined by nickel and the opposite meso carbons:
about 154 and 159° for 7 (C5-Ni-C15 and C10-Ni-C20)
and 158.3 and 158.4° for 8 respectively (C5-Ni-C15 and
C10-Ni-C20). However, due to the relative positions of
the carbonyl groups, this similar geometry induces a very
different relationship between these groups: in 8 carbo-
nyl groups are almost symmetrical relative to a plane
perpendicular to the porphyrin (see Figure 1), while in 7
there are placed at one end of a flattened helix (see Figure
2). In both compounds, the coordination geometry of the
(21) J efford, C. W.; Sienkiewicz, K.; Thornton, S. R. Helv. Chim. Acta
1995, 78, 1511.
(22) Sayah, B.; Pelloux-Le´on, N.; Valle´e, Y. J . Org. Chem. 2000, 65,
2824.
(23) Belcher, W.; Breede, M.; Brothers, P. J .; Rickard, C. E. F.
Angew. Chem., Int. Ed. 1998, 37, 1112. Weiss, A.; Pritzkow, H.;
Brothers, P. J .; Siebert, W. Angew. Chem., Int. Ed. 2001, 40, 4182.
9204 J . Org. Chem., Vol. 68, No. 24, 2003

Preparation of Isomeric Bis-acylporphyrins
F IGURE 2. Two views of diketone 7 (Ar ) 3,5-t-Bu2Ph): (a) t-Bu groups and all hydrogen atoms omitted for clarity; (b) both
meso-aryl and all hydrogen atoms omitted for clarity).
F IGURE 3. Two views (CPK representation) of the two independent molecules of diketone 7 (Ar ) 3,5-t-Bu2Ph) (t-Bu groups and
all hydrogen atoms except the two involved in hydrogen bonding omitted for clarity).
nickel atoms is almost perfectly square planar, with the
Ni-N bonds averaging 1.9 Å.
protonation of ketones requires generally much stronger
acids. The particularity of this geometric arrangement
has also consequences in the solid state. Each diketone
is found oriented toward one meso-phenyl C-H belonging
to the other porphyrin with oxygen to hydrogen distances
in the range of 2.38 to 2.69 Å. This is in very close
agreement with the average value (2.55 Å) found in the
litterature for the hydrogen bond involving an oxygen and
a hydrogen bound to an sp2 carbon.24
Electr on ic Sp ectr a of Dik eton es 5-10. The cycliza-
tion via the ketofunctionality of one (for 10) or two meso-
aryl groups of the nickel porphyrin has a very large effect
on the electronic spectra of the six diketoporphyrins. It
is difficult to fully describe the localization and attribu-
tion of all bands in these spectra without theoretical
calculations.25
However, two general comments can be made: (1) The
addition of unsaturated rings fused to the core of the
porphyrin leads to an extension of the conjugated system,
thus leading to a bathochromic shift of all bands. (2)
fusing additional rings leads to large deformations of the
porphyrin core structure as shown, in our case, by the
X-ray structures of diketones 7 and 8. In general, these
The formation of the additional six-membered ring
induces a close contact between one pyrrolic H and one
phenyl H (2.14 or 2.17 Å). It should be noted that, while
in 8 the â,â′ bonds are slightly longer when a carbonyl
is bound to them (1.359 and 1.364 Å, vs 1.341 and
1.326 Å), this difference is notably larger in 7 where the
two carbonyl groups are vicinal (1.39-1.40 Å vs 1.32-
1.35 Å).
Diketone 7 is found as a pair of stacked independent
porphyrins in the unit cell (see Figure 3). Very short
contacts, as low as 3.25 Å, demonstrate the interaction
between the two aromatic π-electronic systems. The two
oxygen atoms of the diketone carbonyl functions are
extremely close to each other (2.87 and 2.89 Å). This close
proximity explains the very high polarity of the molecule,
most probably due to the ease of protonation, experienced
during the chromatographic separation (see the Experi-
mental Section). This geometry is reminiscent of the one
found in the so-called proton sponges, where two nitrogen
atoms, localized at positions 1 and 8 of a naphthalene
are maintained in close proximity, thus increasing their
basicity. In the case of diketone 7, the molecule can be
protonated quantitatively by adding a relatively weak
acid like benzene sulfonic acid (pKa ) 0.7), whereas
(24) Steiner, T. Angew. Chem., Int. Ed. 2002, 41, 48.
(25) Baerends, E. J .; Ricciardi, G.; Rosa, A.; van Gisbergen, S. J . A.
Coord. Chem. Rev. 2002, 230, 5.
J . Org. Chem, Vol. 68, No. 24, 2003 9205

Richeter et al.
F IGURE 4. Electronic spectra of porphyrins 5-10 in dichloromethane.
deformations are known to induce bathochromic shifts
in the electronic spectra of porphyrins.26
proved to be a method of choice to obtain the nickel
complexes and high conversion was obtained starting
from the appropriate precursors, either esters or cyano
derivatives. The direct cyclization to porphyrin free bases
was less satisfactory. However, it illustrated the high
sensitivity of the regioselectivity of the reaction to the
nature of the complexing ions. All diketones show visible
absorption bands at very long wavelength (up to 826 nm),
as compared to simple porphyrins or monoketones. All
â-unsubstituted ketones are currently used as precursors
to bis-enaminoketones, the building blocks for metal ion
connected porphyrin oligomers.9
The electronic spectra and the electrochemical behavior
of nickel porphyrins depend strongly on electronic and
structural effects introduced by substituents at the meso
or the â-pyrrolic positions. Recently, a systematic study
of 29 nickel porphyrins was reported.27 In these examples,
the Soret bands were observed between 406 and 455 nm
and the Q-bands between 525 and 613 nm. For the
diketoporphyrins reported in this study, forcing the meso-
aryl groups in the plane of the porphyrin by the sp2
carbonyl bridge leads to much larger effects. The Soret
bands are, respectively, seen at 524, 540, 516, 490, 472,
and 482 nm for nickel porphyrins 5-10 (see Figure 4).
The loss of symmetry leads to a splitting of the Soret
bands (as a consequence, we could observe a widening of
these bands or shoulders in some cases) and, thus, to a
decrease of the intensity, compared to more sym-
metrical nickel porphyrins. The bathochromic shifts are
even more impressive for the Q-bands. All diketoporphy-
rins present strong absorption bands between 700 and
800 nm. For porphyrin 7, the lowest energy bands (700-
900 nm) reach the near infrared region. These absor-
bances are quite unusual for nonreduced porphyrins: 700
or 800 nm are typical wavelength values found for
dihydroporphyrins (chlorins) or tetrahydroporphyrins
(bacteriochlorins).
Exp er im en ta l Section
Ester s 11 a n d 12. To a degassed solution of pyrrole (1.34
g, 20 mmol), 2-carbomethoxybenzaldehyde (1.64 g, 10 mmol)
and 3,5-di-tert-butylbenzaldehyde (2.18 g, 10 mmol) in 750 mL
of CH2Cl2 was added BF3‚Et2O (0.4 mL, 3.15 mmol). After 3 h
of stirring at room temperature, in the dark and under argon,
chloranil (3 g, 12 mmol) was added and the solution heated
under reflux for 1 h. The cooled solution was passed through
a short pad of alumina and the solvent evaporated to dryness.
Chromatography (silica gel, 500 mL, hexane to CH2Cl2)
afforded in the order of elution tetra(3,5-di-tert-butylphenyl)-
porphyrin (173 mg), tris(3,5-di-tert-butylphenyl)(o-carbometh-
oxyphenyl)porphyrin (487 mg), 12 (Râ atropisomer) (111 mg),
11 (Râ) (190 mg), 12 (RR) (107 mg), 11 (RR) (299 mg), and a
mixture of the atropisomers of the tri- and tetraesters (not
isolated).
12 (R,â). 1H NMR: δ ) 8.83 (4H, d, J ) 4.8 Hz, pyrrole),
8.63 (4H, d, J ) 4.8 Hz, pyrrole), 8.06 (4H, d, J ) 1.8 Hz,
Ar-o-H), 7.77 (2H, t, J ) 1.8 Hz, Ar-p-H), 8.38 (2H, dd, J )
7.7, 1.5 Hz, benzoate), 8.15 (2H, dd, J ) 7, 1.5 Hz, benzoate),
7.80-7.88 (4H, m, benzoate), 2.80 (6H, s, OCH3), 1.52 (36H,
s, t-Bu), -2.55 (2H, s, NH).
Con clu sion
The synthesis of the six diketones was carried out
successfully. The intramolecular Friedel-Crafts reaction
(26) Kadish, K. M.; Van Caemelbecke, E.; Royal, G. In The Porphyrin
Handbook; Kadish, K. M., Smith, K. M., Guilard, R., Eds.; Academic
Press: Boston, MA, 2000; Vol. 8, p 3.
(27) Kadish, K. M.; Lin, M.; Van Caemelbecke, E.; De Stefano, G.;
Medforth, C. J .; Nurco, D. J .; Nelson, N. Y.; Krattinger, B.; Muzzi, C.
M.; J aquinod, L.; Xu, Y.; Shyr, D. C.; Smith, K. M.; Shelnutt, J . A.
Inorg. Chem. 2002, 41, 6673.
1
11 (R,â). H NMR: δ ) 8.86 (2H, s, pyrrole), 8.82 (2H, d, J
) 4.8 Hz, pyrrole), 8.63 (2H, d, J ) 4.8 Hz, pyrrole), 8.60 (2H,
s, pyrrole), 8.12 (2H, dd, J ) 1.8, 1.8 Hz, Ar-o-H), 7.99 (2H,
dd, J ) 1.8, 1.8 Hz, Ar-o-H), 7.77 (2H, t, J ) 1.8 Hz, Ar-p-H),
8.36 (2H, dd, J ) 7.2, 1.5 Hz, benzoate), 8.20 (2H, dd, J ) 7.0,
9206 J . Org. Chem., Vol. 68, No. 24, 2003

Preparation of Isomeric Bis-acylporphyrins
1.5 Hz, benzoate), 7.80-7.88 (4H, m, benzoate), 2.74 (6H, s,
OCH3), 1.53 (18H, s, t-Bu), 1.50 (18H, s, t-Bu), -2.55 (2H, s,
NH).
(CO). UV-vis: λmax(nm) ) 412 (ꢀ ) 30 100), 480 (55 000, sh),
524 (85 000), 736 (14 000). Anal. Calcd for C62H56N4O2Ni: C,
78.57; H, 5.96; N, 5.91. Found: C, 78.24; H, 5.92; N, 5.77.
12 (R,R). 1H NMR: δ ) 8.82 (2H, d, J ) 4.8 Hz, pyrrole),
8.62 (2H, d, J ) 4.8 Hz, pyrrole), 8.16 (2H, dd, J ) 1.8, 1.8
Hz, Ar-o-H), 7.97 (2H, dd, J ) 1.8, 1.8 Hz, Ar-o-H), 7.77 (2H,
t, J ) 1.8 Hz, Ar-p-H), 8.39 (2H, dd, J ) 7.5, 1.5 Hz, benzoate),
8.16 (2H, dd, J ) 7.0, 1.5 Hz, benzoate), 7.80-7.88 (4H, m,
benzoate), 2.87 (6H, s, OCH3), 1.54 (18H, s, t-Bu), 1.49 (18H,
s, t-Bu), -2.54 (2H, s, NH).
1
Dik eton e 6 (M ) Ni, Ar ) 3,5-Di-ter t-bu tylp h en yl). H
NMR: δ ) 9.34 (1H, broad s, pyrrole), 8.90 (1H, d, J ) 5 Hz,
pyrrole), 8.51 (1H, d, J ) 5 Hz, pyrrole), 8.87 (1H, s, pyrrole),
8.34 (1H, d, J ) 5 Hz, pyrrole), 8.17 (1H, d, J ) 5 Hz, pyrrole),
7.70-7.74 (6H, m, Ar-o-H and Ar-p-H), 8.38 (1H, dd, J ) 7.6,
1 Hz, cyclized phenyl), 8.28 (1H, dd, J ) 7.6, 1 Hz, cyclized
phenyl), 7.80 (1H, dd, J ) 7.6, 1 Hz, cyclized phenyl), 7.75 (1H,
dd, J ) 7.6, 1 Hz, cyclized phenyl), 7.64 (1H, ddd, J ) 7.6, 7.5,
1 Hz, cyclized phenyl), 7.61 (1H, ddd, J ) 7.6, 7.5, 1 Hz,
cyclized phenyl), 7.45 (1H, ddd, J ) 7.6, 7.5, 1 Hz, cyclized
phenyl), 7.39 (1H, ddd, J ) 7.6, 7.5, 1 Hz, cyclized phenyl),
1.47 (18H, s, t-Bu), 1.46 (18H, s, t-Bu). 13C NMR: δ ) 181.6
and 181.9 (CO). UV-vis: λmax(nm) ) 402 (ꢀ ) 36 000), 500
(38 000, sh), 540 (78 000), 646 (10 500), 750 (9000, sh). Anal.
Calcd for C62H56N4O2Ni‚H2O: C, 77.10; H, 6.05; N, 5.80.
Found: C, 77.35; H, 5.78; N, 5.67.
1
11 (R,R). H NMR: δ ) 8.86 (2H, s, pyrrole), 8.83 (2H, d, J
) 4.8 Hz, pyrrole), 8.66 (2H, d, J ) 4.8 Hz, pyrrole), 8.59 (2H,
s, pyrrole), 8.07 (2H, dd, J ) 1.8, 1.8 Hz, Ar-o-H), 8.04 (2H,
dd, J ) 1.8, 1.8 Hz, Ar-o-H), 7.78 (2H, t, J ) 1.8 Hz, Ar-p-H),
8.37 (2H, dd, J ) 7.3, 1.5 Hz, benzoate), 8.18 (2H, dd, J ) 7.0,
1.5 Hz, benzoate), 7.80-7.88 (4H, m, benzoate), 2.67 (6H, s,
OCH3), 1.52 (18H, s, t-Bu), 1.51 (18H, s, t-Bu), -2.55 (2H, s,
NH).
The two atropisomers of each diester were mixed, metalated
quantitatively with Ni(acac)2 in refluxing toluene, and crystal-
lized from CH2Cl2/MeOH.
1
Dik eton e 7 (M ) Ni, Ar ) 3,5-Di-ter t-bu tylp h en yl). H
NMR (CDCl3, 318 K): δ ) 8.92 (2H, d, J ) 5.1 Hz, pyrrole),
8.34 (2H, d, J ) 5.1 Hz, pyrrole), 8.14 (2H, s, pyrrole), 7.69
(2H, t, J ) 1.8 Hz, Ar-p-H), 7.66 (4H, d, J ) 1.8 Hz, Ar-o-H),
8.51 (2H, dd, J ) 7.7, 1 Hz, cyclized phenyl), 7.76 (2H, dd, J
) 7.7, 1 Hz, cyclized phenyl), 7.61 (2H, ddd, J ) 7.7, 7.2, 1
Hz, cyclized phenyl), 7.48 (2H, ddd, J ) 7.7, 7.2, 1 Hz, cyclized
phenyl), 1.46 (36H, s, t-Bu). 13C NMR: δ ) 179.9 (CO). UV-
vis: λmax(nm) ) 390 (ꢀ ) 41 800), 480 (51 000, sh), 516 (74 800),
738 (12 000), 826 (11 700). Anal. Calcd for C62H56N4O2Ni: C,
78.57; H, 5.96; N, 5.91. Found: C, 78.46; H, 5.78; N, 5.67.
Dik eton es 8 a n d 9 (M ) Ni, Ar ) 3,5-Di-ter t-bu tyl-
p h en yl). A solution of the nickel complex of diester 12 (96
mg, 95 µmoles) and LiOH‚H2O (100 mg, 2.48 mmol) in dioxane/
water (100 mL, 4:1) was heated at 100 °C and stirred under
argon during 24 h. The solvents were evaporated, and the solid
residue was dried under vacuum. To this residue were added
benzene (100 mL) and oxalyl chloride (5 mL, 57 mmol), and
the solution was heated during 3 h at 50 °C. The solvents were
partly evaporated (10 mL, to eliminate excess oxalyl chloride),
and SnCl4 (1 mL, 8.5 mmol) was added. After 30 min, CH2Cl2
(200 mL) was added and the solution neutralized with aqueous
NaOH. The organic phase was washed with water (5 × 1L)
and dried with Na2SO4. Chromatography (silica gel, 300 mL,
hexane to CH2Cl2) and crystallization from CH2Cl2/MeOH
afforded the brown diketone 8 (32 mg, 36%) and the yellow
diketone 9 (36 mg, 40%).
Nick el Com p lex of Keton e 1 (M ) Ni, Ar ) P h en yl)
fr om Cop p er 2-Cya n oTP P 13. A mixture of of copper
2-cyanoTPP 13 (600 mg, 0.85 mmol) in AcOH (500 mL) and
aq HBr (48%, 300 mL) was heated under reflux for 4 days and
then diluted with CHCl3 (400 mL). This solution was washed
with water until the organic phase showed a stable purple-
brown color (6 to 8 washings with 400 mL water). The solution
was dried (Na2SO4) and concentrated. Addition of hexane gave
a violet powder which was dried at 100 °C (552 mg) and used
as such. This crude product, nickel acetylacetonate (1 g), and
DMF (400 mL) were heated under reflux for 5 min. After the
solution was cooled, slow addition of 10% aq AcOH induced
the crystallization of the nickel complex of acid 14, which was
filtered, washed with 10% aq AcOH, and dried at 100 °C (635
mg). 1H NMR: δ ) 9.06 (1H, s, pyrrole), 8.75, 8.73, 8.69, 8.68,
8.64 (1+1+1+2+1H, 5d, J ) 5 Hz, pyrrole), 8-8.1 (8H, m, Ph
o-H), 7.6-7.8 (12H, m, Ph m+p-H). Ketone 1 (M ) Ni, Ar )
phenyl) was then prepared either in one step, or from the acid
chloride, or from a mixed anhydride.
Dir ect Rou te. The crude nickel complex of acid 14 (50 mg)
and dry ZnCl2 (50 mg) were stirred in refluxing 1,2-dichlo-
robenzene (25 mL) for 90 min. Evaporation of the solvent gave
a residue which was chromatographed (silica gel, CH2Cl2) to
give nickel meso-tetraphenylporphyrin (26 mg, 57% from 13)
and ketone 1 (M ) Ni, 7 mg, 15% from 13).
Acid Ch lor id e Rou te. A solution of crude nickel complex
of acid 14 (20 mg) in dry CH2Cl2 (5 mL) was treated with oxalyl
chloride (0.5 mL). After 1 h, the solvant and reagent were
evaporated under vacuum, and dry CH2Cl2 (5 mL) was added
followed by SnCl4 (0.1 mL). The red solution turned im-
mediately brown. After 5 min, the reaction mixture was
hydrolyzed with aq NaHCO3 and dried (Na2SO4). Filtration
through a short silica gel column and crystallization from
CH2Cl2/MeOH gave ketone 1 (M ) Ni, 17 mg, 90% from 13).
1
Dik eton e 8 (M ) Ni, Ar ) 3,5-Di-ter t-bu tylp h en yl). H
NMR (318 K): δ ) 9.01 (2H, d, J ) 5.1 Hz, pyrrole), 8.94
(2H, s, pyrrole), 8.41 (2H, d, J ) 5.1 Hz, pyrrole), 7.75 (1H,
t, J ) 1.8 Hz, Ar-p-H), 7.73 (1H, t, J ) 1.8 Hz, Ar-p-H), 7.70
(2H, d, J ) 1.8 Hz, Ar-o-H), 7.65 (2H, d, J ) 1.8 Hz, Ar-o-H),
8.46 (2H, dd, J ) 7.8, 1 Hz, cyclized phenyl), 7.96 (2H, dd,
J ) 7.8, 1 Hz, cyclized phenyl), 7.70 (2H, ddd, J ) 7.8, 7.8,
1 Hz, cyclized phenyl), 7.50 (2H, ddd, J ) 7.8, 7.8, 1 Hz,
cyclized phenyl), 1.47 (18H, s, t-Bu), 1.45 (18H, s, t-Bu). 13C
NMR: δ ) 182.1 (CO). UV-vis: λmax(nm) ) 420 (ꢀ ) 51 000),
490 (111 000), 550 (21 600), 726 (28 200). Anal. Calcd for
C
62H56N4O2Ni‚0.5H2O: C, 77.83; H, 6.00; N, 5.86. Found: C,
77.84; H, 5.84; N, 5.68.
1
Dik eton e 9 (M ) Ni, Ar ) 3,5-Di-ter t-bu tylp h en yl). H
NMR (318 K): δ ) 8.99 (2H, d, J ) 5 Hz, pyrrole), 8.88 (2H,
s, pyrrole), 8.52 (2H, d, J ) 5 Hz, pyrrole), 7.75 (2H, t, J )
1.8 Hz, Ar-p-H), 7.70 (4H, broad d, J ) 1.8 Hz, Ar-o-H), 8.43
(2H, dd, J ) 7.5, 1 Hz, cyclized phenyl), 8.01 (2H, dd, J ) 7.8,
1 Hz, cyclized phenyl), 7.70 (2H, ddd, J ) 7.8, 7.8, 1 Hz,
cyclized phenyl), 7.48 (2H, ddd, J ) 7.8, 7.8, 1 Hz, cyclized
phenyl), 1.47 (36H, s, t-Bu). 13C NMR: δ ) 181.4 (CO). UV-
vis: λmax(nm) ) 472 (ꢀ ) 109 000), 698 (27 400), 776 (17 300).
Anal. Calcd for C62H56N4O2Ni: C, 78.57; H, 5.96; N, 5.91.
Found: C, 78.21; H, 5.81; N, 5.83.
Dik et on es 5, 6, a n d 7 (M ) Ni, Ar ) 3,5-Di-ter t-b u -
tylp h en yl). These diketones were prepared from 11 following
the same procedure in 18, 24, and 44% respectively (see the
Supporting Information).
Mixed An h yd r id e Rou te. A solution of crude nickel com-
plex of acid 14 (50 mg) in acetone (5 mL) was treated with
triethylamine (0.1 mL) and ethyl chloroformate (0.05 mL). The
solution was stirred for 20 min, washed with water, dried, and
evaporated. Toluene (10 mL) was added and evaporated twice
to eliminate the last traces of reagents. The crude mixed
anhydride was dissolved in CH2Cl2 (5 mL), and ZnCl2 (50 mg)
was added at once. After 1 h, the brown reaction mixture was
1
Dik eton e 5 (M ) Ni, Ar ) 3,5-Di-ter t-bu tylp h en yl). H
NMR: δ ) 9.05 (2H, s, pyrrole), 8.94 (2H, s, pyrrole), 8.28 (2H,
s, pyrrole), 7.70 (2H, t, J ) 1.8 Hz, Ar-p-H), 7.66 (4H, d, J )
1.8 Hz, Ar-o-H), 8.40 (2H, dd, J ) 7.8, 1 Hz, cyclized phenyl),
7.67 (2H, dd, J ) 7.8, 1 Hz, cyclized phenyl), 7.61 (2H, ddd, J
) 7.8, 7.8, 1 Hz, cyclized phenyl), 7.44 (2H, ddd, J ) 7.8, 7.8,
1 Hz, cyclized phenyl), 1.45 (36H, s, t-Bu). 13C NMR: δ ) 182.3
J . Org. Chem, Vol. 68, No. 24, 2003 9207

Richeter et al.
washed with aq NaHCO3 and water, dried (Na2SO4), and
evaporated. Chromatography on silica gel (200 mL in CH2Cl2)
gave green ketone 1 (M ) Ni; 16 mg; 34% from 13). When
ZnCl2 was replaced by BF3‚Et2O the yield of ketone 1 dropped
to 17%.
pinkish-brown fraction containing diketone 10. Evaporation
of the solvent gave a brown solid which was put in suspension
in hexane, filtered, and washed with hexane (10 mg, 37% as
1
CHCl3 solvate). H NMR: δ ) 9.24 (2H, s, pyrrole), 8.53 (2H,
d, J ) 5 Hz, pyrrole), 8.49 (2H, dd, J ) 8 and 1.8 Hz, cyclized
phenyl), 8, 47 (2H, d, J ) 5 Hz, pyrrole), 7.83 (6H, m, di-tert-
butylphenyl o-H), 7.78 (3H, m, di-tert-butylphenyl p-H), 7.51
(1H, t, J ) 8 Hz, cyclized phenyl). UV-vis: λmax(nm) ) 348 (ꢀ
) 33 000), 386 (23 200), 482 (70 600), 522 (19 200), 698
(20 200). Anal. Calcd for C70H72N4O2Ni‚CHCl3: C, 72.30; H,
6.24; N, 4.75. Found: C, 73.05; H, 6.17; N, 4.91. A better C
figure could not be obtained.
Dik eton es 5 a n d 9 (M ) Ni, Ar ) P h en yl) fr om Dicy-
a n op or p h yr in s 15 a n d 16. Diketones 5 and 9 (Ar ) phenyl)
were prepared from 15 and 16 as above (acid chloride route)
in 30 and 27%, respectively (see the Supporting Information).
m eso-Tr is(3,5-d i-ter t-b u t ylp h en yl)(2,6-d ich lor op h en -
yl)p or p h yr in 17. To a solution of 3,5-di-tert-butylbenzalde-
hyde (982 mg, 4.5 mmol), 2,6-dichlorobenzaldehyde (262 mg,
1.5 mmol), and pyrrole (402 mg, 6 mmol) in CH2Cl2 (750 mL),
kept under argon, was added BF3‚Et2O (0.2 mL). The solution
was stirred for 1.5 h, treated with chloranil (1 g), and stirred
for an additional 1.5 h. The solution was filtered on alumina
(150 mL). Evaporation of the solvent gave a residue which was
chromatographed (silica gel; 400 mL in hexane/CH2Cl2 2:1).
Elution with the same solvent gave a first fraction containing
meso-tetra(3,5-di-tert-butylphenyl)porphyrin, followed by the
required product 17, which was crystallized from CH2Cl2/
MeOH (160 mg; 20%). 1H NMR: δ ) 8.92 (6H, m, pyrrole),
8.66 (2H, d, J ) 5 Hz, pyrrole), 8.07 (6H, m, di-tert-butylphenyl
o-H), 7.70 (6H, m, remaining phenyl H), 1.54 (54H, s, tert-
butyl), -2.6 (2H, broad signal, NH). UV-vis (as the copper
complex): λmax(nm) ) 414 (ꢀ ) 403 000), 540 (22000). Anal.
(as the copper complex) Calcd for C68H74N4Cl2Cu: C, 75.50;
H, 6.89; N, 5.18. Found: C, 75.54; H, 6.92; N, 5.23.
Dik eton e F r ee Ba ses 6 a n d 9 (M ) H2, Ar ) 3,5-Di-ter t-
bu tylp h en yl). Diester 11 (96 mg, 0.1 mmol) was dissolved in
a molar solution of BBr3 in CH2Cl2 (6 mL, 6 mmol). After 10
h at 20 °C, the solution was treated with saturated aqueous
NaHCO3, dried (Na2SO4), and evaporated. The residue was
chromatographed (silica gel, 100 mL, CH2Cl2 to CH2Cl2/AcOEt
5:2). The low polarity fraction contained only one product
which was crystallized in CH2Cl2/MeOH to give crystals of 6
(10 mg, 11%). An identical procedure was followed from diester
12 to give 9 (20%).
1
Dik eton e 6 (M ) H2, Ar ) 3,5-Di-ter t-bu tylp h en yl). H
NMR: δ ) 9.81 (1H, s, pyrrole), 8.98 (1H, s, pyrrole), 8.98 (1H,
d, J ) 4.8 Hz, pyrrole), 8.51 (1H, dd, J ) 7.8, 1 Hz, cyclized
phenyl), 8.47 (1H, dd, J ) 7.8, 1 Hz, cyclized phenyl), 8.38
(1H, d, J ) 4.8 Hz, pyrrole), 8.30 (1H, d, J ) 4.8 Hz, pyrrole),
8.19 (1H, dd, J ) 7.8, 1 Hz, cyclized phenyl), 8.18 (1H, dd,
J ) 7.8, 1 Hz, cyclized phenyl), 7.87 (2H, d, J ) 1.8 Hz, di-
tert-butylphenyl o-H), 7.82 (2H, d, J ) 1.8 Hz, di-tert-butyl-
phenyl o-H), 7.79 (1H, ddd, J ) 7.8, 7.8, 1 Hz, cyclized phenyl),
7.78 (1+1H, 2t, J ) 1.8 Hz, di-tert-butylphenyl p-H), 7.77
(1H, ddd, J ) 7.8, 7.8, 1 Hz, cyclized phenyl), 7.53 (1H, ddd, J
) 7.8, 7.8, 1 Hz, cyclized phenyl), 7.48 (1H, ddd, J ) 7.8, 7.8,
1 Hz, cyclized phenyl), 1.52 (18H, s, tert-butyl), 1.49 (18H, s,
tert-butyl). The NH signals could not be detected. UV-vis:
Cop p er Com p lex of m eso-Tr is(3,5-d i-ter t-bu tylp h en yl)-
(2,6-d icya n op h en yl)p or p h yr in 18. Porphyrin 17 (145 mg,
0.145 mmol), CuCN (230 mg, 2.5 mmol), and N-methylpyrro-
lidinone (3 mL) were sealed under vacuum in a glass tube and
heated to 250 °C for 15 h. After opening of the tube, the
reaction mixture was diluted with CH2Cl2 (30 mL), washed
with water (7 × 150 mL), dried (Na2SO4), and evaporated. The
residue was chromatographed on silica gel (300 mL, hexane/
CH2Cl2 1:1). Slow elution gave traces of starting material, an
intermediate fraction (25 mg; possibly monocyanated prod-
uct), followed by the copper dicyanoporphyrin 18, crystal-
lized from MeOH (80 mg, 51%). This product is sensitive to
light and should be protected during its purification. UV-vis:
λ
max(nm) ) 542 (ꢀ ) 89 000), 702 (13 000), 754 (12500). Anal.
Calcd for C62H58N4O2‚0.5H2O: C, 81.10; H, 6.70; N, 6.10.
Found: C, 81.01; H, 6.30; N, 6.10.
1
Dik eton e 9 (M ) H2, Ar ) 3,5-Di-ter t-bu tylp h en yl). H
NMR: δ ) 9.12 (2H, d, J ) 4.9 Hz, pyrrole), 9. 02 (2H, s,
pyrrole), 8.49 (2H, d, J ) 4.9 Hz, pyrrole), 8.45 (2H, dd, J )
7.8, 1 Hz, cyclized phenyl), 8.23 (2H, dd, J ) 7.8, 1 Hz, cyclized
phenyl), 7.81 (4H, d, J ) 1.7 Hz, di-tert-butylphenyl o-H), 7.78
(2H, t, J ) 1.7 Hz, di-tert-butylphenyl p-H), 7.76 (2H, ddd, J
) 7.8, 7.8, 1 Hz, cyclized phenyl), 7.50 (2H, ddd, J ) 7.8, 7.8,
1 Hz, cyclized phenyl), 1.53 (36H, s, tert-butyl). The NH signals
could not be detected. UV-vis: λmax(nm) ) 468 (ꢀ ) 120 100),
504 (72 000), 622 (6300), 688 (9500), 842 (19 000). Anal. Calcd
for C62H58N4O2‚2MeOH: C, 80.47; H, 6.96; N, 5.87. Found: C,
80.23; H, 6.68; N, 5.53.
λ
max(nm) ) 422 (ꢀ ) 360 000), 542 (21 200). Anal. Calcd for
C
70H74N6Cu: C, 79.10; H, 7.02; N, 7.91. Found: C, 78.67; H,
6.80; N, 8.01.
Nick el Com p lex of Dik eton e 10 (M ) Ni, Ar ) 3,5-Di-
ter t-bu tylp h en yl). Copper complex 18 (24 mg, 0.022 mmol)
was stirred in TFA/H2SO4 (10 mL, 1:1) until complete dissolu-
tion. To the green solution was added AcOH (15 mL), and 10
mL of the mixture was removed by boiling. To this solution
were added AcOH (8 mL) and water (2 mL), and the mixture
was heated under reflux for 24 h. This green solution was
cooled, diluted with CHCl3 (50 mL), and washed with water
until the organic phase showed a stable purple-brown color.
This solution was dried (Na2SO4) and evaporated to dryness.
The residue was dissolved in DMF (20 mL) and brought to
ebullition. Addition of nickel acetate (200 mg) and further
boiling for 3 min gave a red solution. After cooling, slow
addition of a water-acetic acid (1:1) mixture induced the
precipitation of the diacid, which was filtered, thoroughly
washed with water, and dried under vacuum. This product
was used as such for the next step. The crude diacid (ca 20
mg) was dissolved in dry benzene (20 mL) and treated at 25
°C with oxalyl chloride (1 mL). After 2 h, the solution was
evaporated to dryness under vacuum and the residue dissolved
in benzene (15 mL). Upon addition of SnCl4 (0.1 mL), the red
solution turned rapidly brown and was stirred for 15 min. The
reaction mixture was then diluted with CHCl3 (100 mL),
saturated aqueous NaHCO3 (100 mL) was added, and the
two phases were stirred vigorously for 30 min. The organic
phase was decanted, washed with water (3 × 100 mL), dried
(Na2SO4), and evaporated. The residue was chromatographed
on silica gel (100 mL, CHCl3). Elution with CHCl3 gave a major
Ack n ow led gm en t. We thank A. Decian (Service
Commun de Rayons X, Universite´ Louis Pasteur) for
help in solving the structures, R. Graff (Service Com-
mun de RMN, Universite´ Louis Pasteur) for the NMR
experiments, and E. Mastio and P. Wehrung for the
mass spectra.
Note Ad d ed in P r oof. A lower homologue of diketone
7 was recently described in the seco-porphyrin series.
See: McCarthy, J . R.; Hyland, M. A.; Bru¨ckner, C. Chem.
Commun. 2003, 1738.
Su p p or tin g In for m a tion Ava ila ble: General experimen-
tal procedures and selected synthetic procedures. Crystal data
for compounds 7 and 8. X-ray data for compounds 7 and 8
(CIF). This material is available free of charge via the Internet
at http://pubs.acs.org.
J O035108M
9208 J . Org. Chem., Vol. 68, No. 24, 2003