5,10,15-Triaryl-21,23-dioxacorrole and its isomer with a protruding furan ring

Article abstract of DOI:10.1021/jo025773f

An oxa-analogue of 5,10,15-triarylcorrole, i.e., 5,10,15-triaryl-21,23-dioxacorrole (21,23-O₂Cor)H, where two pyrrole rings are replaced by furan moieties, has been produced by condensation of 2,5-bis(arylhydroxymethyl)furan, 2-phenylhydroxymethylfuran, and pyrrole. 2-Phenylhydroxymethylfuran serves as the suitable synthone to introduce a furan ring with the ability create a direct pyrrole-furan α-α bond. The replacement of 2-phenylhydroxymethylfuran by 3-phenylhydroxymethylfuran led to a nonaromatic isomer of (21,23-O₂Cor)H, i.e., (iso-21,23-O₂Cor)H, which accommodates two furan rings. The protruding furan is built into the macrocycle via β and β′ carbon atoms with the oxygen atom pointing outward. Crystal structures of the [(21,23-O₂Cor)H₂]₂[ZnCl₄] and [(iso-21,23-O₂Cor)H₂] Cl have been studied by X-ray crystallography. The complex ZnCl₄^2- anion is located in a clam-shell-like cavity formed by two 21,23-dioxacorrole cations of the [(21,23-O₂-Cor)H₂]₂[ZnCl₄] unit. The 21,23-dioxacorrole cation is only slightly distorted from planarity. In [(iso-21,23-O₂Cor)H₂]Cl, the macrocycle is strongly puckered as the internal ring is contracted by two carbon atoms when compared to regular porphyrin. The chloride anion is located over the center of the macrocycle and is involved in two intra (N)···HCl and two intermolecular (C)···HCl interactions to be classified as a tetrafurcate system. The (21,23-O₂Cor)H molecule preserves aromaticity of the parental corrole with characteristic downfield positions of furan and pyrrole resonances in ¹H NMR accompanied the NH resonance at the upfield position (-2.53 ppm). The temperature- dependent features detected in ¹H NMR spectra of (21,23-O₂Cor)H are consistent with the existence of a tautomeric equilibrium which involves two tautomers alternatively protonated on N(22) or N(24) nitrogen atoms. The density functional theory (DFT) has been applied to model the molecular and electronic structure of two tautomers of 21,23-dioxacorrole {22-N, 24-NH}, {22-NH, 24-N}. The total energies calculated using the B3LYP/6-31G**//B3LYP/6-31G* approach demonstrate a very small energy difference (1.4 kcal/mol) between tautomers suggesting their simultaneous presence in equilibrium. Insertion of nickel(II) into (21,23-O₂Cor)H yields five-coordinate (21,23-O₂Cor)Ni^IICl-the first high-spin nickel(II) in a corrole-like macrocyclic environment.

Full text of DOI:10.1021/jo025773f

5
,10,15-Tr ia r yl-21,23-d ioxa cor r ole a n d Its Isom er w ith a
P r otr u d in g F u r a n Rin g
Miłosz Pawlicki, Lechosław Latos-Gra z˘ y n´ ski,* and Ludmiła Szterenberg
Department of Chemistry, University of Wrocław, 50 383 Wrocław, Poland
llg@wchuwr.chem.uni.wroc.pl
Received March 28, 2002
An oxa-analogue of 5,10,15-triarylcorrole, i.e., 5,10,15-triaryl-21,23-dioxacorrole (21,23-O
where two pyrrole rings are replaced by furan moieties, has been produced by condensation of
,5-bis(arylhydroxymethyl)furan, 2-phenylhydroxymethylfuran, and pyrrole. 2-Phenylhydroxym-
2
Cor)H,
2
ethylfuran serves as the suitable synthone to introduce a furan ring with the ability create a direct
pyrrole-furan R-R bond. The replacement of 2-phenylhydroxymethylfuran by 3-phenylhydroxym-
2 2
ethylfuran led to a nonaromatic isomer of (21,23-O Cor)H, i.e., (iso-21,23-O Cor)H, which accom-
modates two furan rings. The protruding furan is built into the macrocycle via â and â′ carbon
atoms with the oxygen atom pointing outward. Crystal structures of the [(21,23-O
2
Cor)H
2
]
4
2
2
[ZnCl
anion
4
]
-
and [(iso-21,23-O Cor)H ]Cl have been studied by X-ray crystallography. The complex ZnCl
2
2
is located in a clam-shell-like cavity formed by two 21,23-dioxacorrole cations of the [(21,23-O
Cor)H [ZnCl ] unit. The 21,23-dioxacorrole cation is only slightly distorted from planarity. In [(iso-
1,23-O Cor)H ]Cl, the macrocycle is strongly puckered as the internal ring is contracted by two
2
-
2
]
2
4
2
2
2
carbon atoms when compared to regular porphyrin. The chloride anion is located over the center
of the macrocycle and is involved in two intra (N)H‚‚‚Cl and two intermolecular (C)H‚‚‚Cl interactions
2
to be classified as a tetrafurcate system. The (21,23-O Cor)H molecule preserves aromaticity of
1
the parental corrole with characteristic downfield positions of furan and pyrrole resonances in H
NMR accompanied the NH resonance at the upfield position (-2.53 ppm). The temperature-
1
dependent features detected in H NMR spectra of (21,23-O
2
Cor)H are consistent with the existence
of a tautomeric equilibrium which involves two tautomers alternatively protonated on N(22) or
N(24) nitrogen atoms. The density functional theory (DFT) has been applied to model the molecular
and electronic structure of two tautomers of 21,23-dioxacorrole {22-N, 24-NH}, {22-NH, 24-N}.
The total energies calculated using the B3LYP/6-31G**//B3LYP/6-31G* approach demonstrate a
very small energy difference (1.4 kcal/mol) between tautomers suggesting their simultaneous
presence in equilibrium. Insertion of nickel(II) into (21,23-O
2
Cor)H yields five-coordinate (21,23-
II
O
2
Cor)Ni Clsthe first high-spin nickel(II) in a corrole-like macrocyclic environment.
In tr od u ction
applied to explore properties of corroles and their
complexes.1
4-16
Novel efficient procedures for synthesis of 5,10,15-
triarylcorroles that are based on condensation of simple
building blocks, i.e., (1) pyrrole and aryl aldehydes, (2)
A corrole molecule is an 18 π electron aromatic mac-
rocycle with a direct R-R pyrrole-pyrrole link. Formally,
one can consider 5,10,15-triarylcorrole as a molecule
derived from 5,10,15,20-tetraarylporphyrins simply by
1
-4
5
,6
dipyromethane and aldehyde,
or oxidant-mediated
coupling of tetrapyrromethanes,7 give an incentive to
exploit triarylcoroles as suitable ligands.8
-13
6 5
extrusion of a C-C H moiety. As a matter of fact, the
Previously,
â-alkylated, meso-unsubstituted corroles have been largely
(10) Simkhovich, L.; Galili, N.; Saltsman, I.; Goldberg, I.; Gross, Z.
*
(
To whom correspondence should be addressed.
1) Paolesse, R.; J aquinoid, L.; Nurco, D. J .; Mini, S.; Sagone, F.;
Boschi, T.; Smith, K. M. Chem. Commun. 1999, 1307.
2) Paolesse, R.; Nardis, S.; Sagone, F.; Khoury, R. G. J . Org. Chem.
001, 66, 550.
3) Gross, Z.; Galili, N.; Saltsman, I. Angew. Chem., Int. Ed. Engl.
999, 38, 1427.
4) Gross, Z.; Galili, N.; Simkhovich, L.; Saltsman, I.; Botoshansky,
M.; Bl a¨ ser, D.; Boese, R.; Goldberg, I. Org. Lett. 1999, 1, 599.
Inorg. Chem. 2000, 39, 2704.
(11) Simkhovich, L.; Mahammed, A.; Goldberg, I.; Gross, Z. Chem.
Eur. J . 2001, 7, 1041.
(12) Mahammed, A.; Goldberg, I.; Gross, Z. Org. Lett. 2001, 3, 3443.
(13) Meier-Callahan, A. E.; Di Bilio, A. J .; Simkhovich, L.; Ma-
hammed, A.; Goldberg, I.; Gray, H. B.; Gross, Z. Inorg. Chem. 2001,
40, 6788.
(
2
1
(
(
(14) Liccocia, S.; Paolesse, R. Struct. Bonding (Berlin) 1995, 84, 72-
133.
(
(
(
5) Gryko, D. Chem. Commun. 2000, 2243.
6) Gryko, D.; J adach, K. J . Org. Chem. 2001, 66, 4267.
7) Ka, J .-W.; Cho, W.-S.; Lee, C.-H. Tetrahedron Lett. 2000, 41,
(15) Paolesse, R. Syntheses of Corroles. In The Porphyrin Handbook;
Kadish, K. M., Smith, K. M., Guilard, R., Eds.; Academic Press: New
York, 2000; p 201.
(16) Erben, C.; Will, S.; Kadish, K. M. Metallocorroles: Molecular
Structure, Spectroscopy and Electronic States. In The Porphyrin
Handbook; Kadish, K. M., Smith, K. M., Guilard, R., Eds.; Academic
Press: New York, 2000; p 233.
8
121.
(8) Gross, Z.; Simkhovich, L.; Galili, N. Chem.Commun. 1999, 599.
9) Meier-Callahan, A. E.; Gray, H. B.; Gross, Z. Inorg. Chem. 2000,
(
3
9, 3605.
1
0.1021/jo025773f CCC: $22.00 © 2002 American Chemical Society
Published on Web 07/03/2002
5
644
J . Org. Chem. 2002, 67, 5644-5653

5
,10,15-Triaryl-21,23-dioxacorrole
first triarylcorrole was prepared in this way.17 The
formation of 5,10,15-triarylcorroles seems to be a natural
and predictable consequence of the classical Rothemund-
like pyrrole-arylaldehyde condensation considering the
dipyrromethane and furylpyrromethanediol yielded
5,10,15-triaryloxacorrole in addition to the expected
5,10,15,20-tetraaryl-21-oxaporphyrin.34 Lee and co-work-
ers have reported on an original way to produce 5,10,15-
triaryl-21-oxacorrole and, for the first time, the isomeric
1
8-22
mechanism of the process.
Actually, a variety of other
3
5
macrocylic products accompanying tetraarylporphyrins
5,10,15-triaryl-22-oxacorrole. Finally, the Vogel group
are formed in the course of condensation.2
3-26
succeeded
36,37
in preparation of tetraoxacorrole cation and
Potential applications of metallotriarylcorroles in cata-
lytic processes of oxygen atom transfer or cyclopropana-
tion provide the essential stimuli for further synthetic
studies.8 Certainly, the presence of meso aryl rings
opens an access to control the electronic structure and
overall molecular architecture including an access to the
corrole core by means of well-planned peripheral substi-
tutions. First the contracted macrocyclic core has proper-
ties significantly different compared with the porphyrins
or metalloporphyrins.14-16 In particular, metallocorroles
revealed a tendency to stabilize the higher oxidation
states of coordinated metal ions or metal ion and
macrocycle.1
octaethyltetroxacorrole cation, although these results are
practically available in the review articles.1
5,16
A comple-
mentary area of corrole modifications, which can be
described as a replacement of carbon atom(s) in the
corrole skeleton by heteroatom(s), yielded 10-oxacorrole,
,11
3
8,39
10-thiacorrole,
and 5,10,15-triazacorrole (corrola-
zine).40
Complexes of 5,10,15-triaryl-21-oxacorrole with nickel-
(II), copper(II), cobalt(II), and rhodium(I) have been
33
investigated. The monooxacorrole acts as a dianionic
ligand that stabilizes nickel(II) (low-spin) and copper(II)
complexes. These observations remain in contrast with
corroles that act as a trianionic ligand favoring higher
oxidation states of complexes.27 Previously, we have
elucidated a relationship between the number of oxygen
atoms and the coordination properties of nickel(II) and
nickel(I) in the conceptually related series of 5,10,15,20-
tetraphenylporphyrin, 5,10,15,20-tetraaryl-21-oxapor-
0,13,27-30
Apart from perimeter substitution, a different strategy,
involving core alteration, can be considered as an inde-
pendent route for controlling the reactivity of metallo-
corroles. In such an approach, at least one of the inner
nitrogen atoms should be replaced by another hetero-
atom. At present, known core modified heterocorroles are
not numerous. In their pioneering investigations of core-
4
1-43
phyrin, and 5,10,15,20-tetraaryl-21,23-dioxaporphyrin.
Thus, considering the fundamental changes introduced
by replacement of one nitrogen atom by oxygen to yield
21-oxacorrole, we have found it important to explore the
properties of other compounds in the series.
Here, we describe the synthesis and spectroscopic
properties of the first 21,23-dioxacorrole, i.e., 5,10,15-
triaryl-21,23-dioxacorrole and its isomer with a protrud-
ing furan ring. In particular, the applicability of 2-phe-
nylhydroxymethylfuran and 3-phenylhydroxymethylfuran
as synthones in the oxacorrole ring construction have
been explored.
3
1
modified porphyrins and expanded porphyrins pre-
sented in 1972, J ohnson and co-workers introduced
â-alkylated 21,24-dioxacorrole, 21-oxacorrole, and 22-
oxacorrole. Recently, Chandrashekar and co-workers
have demonstrated that the R-R coupling of 5,10-
diphenyl-16-oxatripyrrane and dipyrromethane yields
5
,10,15-triaryl-21-oxacorrole.32,33 Lindsey and co-workers
have remarked that the condensation of 5-(p-tolyl)-
(
17) Paolesse, R.; Liccocia, S.; Bandoli, G.; Dolmella, A.; Boschi, T.
Inorg. Chem. 1994, 33, 1171.
18) Rose, E.; Kossanyi, A.; Quelquejeu, M.; Soleilhavoup, M.;
Duwavran, F.; Bernard, N.; Lecas, A. J . Am. Chem. Soc. 1994, 118,
567.
19) Loim, N. M.; Grishko, E. V.; Pyshnograeva, N. I.; Vorontsov,
E. V.; Sokolov, V. I. Izv. Akad. Nauk, Ser. Chem. 1994, 5, 925.
20) Latos-Gra z˘ y n´ ski, L.; Chmielewski, P. J . New J . Chem. 1997,
1, 691.
(
Resu lt a n d Discu ssion
1
(
Syn th esis an d Ch ar acter ization of 5-P h en yl-10,15-
bis(p-tolyl)-21,23-d ioxa cor r ole. The synthesis involves
the condensation of 2,5-bis(p-tolylhydroxymethyl)furan
(
2
(
21) Latos-Gra z˘ y n´ ski, L. Core Modified Heteroanalogues of Porphy-
1
and 2-phenylhydroxymethylfuran 2, with pyrrole (1:
1:2 molar ratio), carried out in dichloromethane and
catalyzed by BF ‚Et O. After oxidation with p-chloranil,
-phenyl-10,15-bis(p-tolyl)-21,23-dioxacorrole 3 is ob-
tained in 8% yield. The reaction is presented in Scheme
rins and Metalloporphyrins. In The Porphyrin Handbook; Kadish, K.
M., Smith, K. M., Guilard, R., Eds.; Academic Press: New York, 2000;
p 361.
3
2
(22) Lindsey, J . S. Synthesis of Meso-Substituted Porphyrins. In The
5
Porphyrin Handbook; Kadish, K. M., Smith, K. M., Guilard, R., Eds.;
Academic Press: New York, 2000; pp 45-118.
(23) Chmielewski, P. J .; Latos-Gra z˘ y n´ ski, L.; Rachlewicz, K.; Glow-
1
.
iak, T. Angew. Chem., Int. Ed. Engl. 1994, 33, 779.
24) Furuta, H.; Asano, T.; Ogawa, T. J . Am. Chem. Soc. 1994, 116,
67.
25) Chmielewski, P. J .; Latos-Gra z˘ y n´ ski, L.; Rachlewicz, K. Chem.
Eur. J . 1995, 1, 68.
26) Shin, J .-Y.; Furuta, H.; Yoza, K.; Igarashi, S.; Osuka, A. J . Am.
Chem. Soc. 2001, 123, 7190.
27) Will, S.; Lex, J .; Vogel, E.; Schmickler, H.; Gisselbrecht, J .-P.;
Haubtman, C.; Bernard, M.; Gross, M. Angew. Chem., Int. Ed. Engl.
997, 36, 357.
28) Van Caemelbecke, E.; Will, S.; Autret, A.; Adamian, V.; Lex,
J .; Gisselbrecht, J .-P.; Gross, M.; Vogel, E.; Kadish, K. M. Inorg. Chem.
996, 35, 184.
(
The reaction applies 2-phenylhydroxymethylfuran as
the suitable synthone to introduce the furan ring, which
7
(
(
(34) Cho, W.-S.; Kim, H.-J .; Litter, B. J .; Miller, M. A.; Lee, C.-H.;
Lindsey, J . S. J . Org. Chem. 1999, 64, 7890.
(35) Lee, C.-H.; Cho, W.-S.; Ka, J .-W.; Kim, H.-J .; Lee, P. H. Bull.
Korean Chem. Soc. 2000, 21, 429.
(36) Behrens, F. Ph.D. Thesis, University of Cologne, 1994.
(37) Dorr, J . Ph.D. Thesis, University of Cologne, 1994.
(38) J ohnson, A. W.; Kay, I. T. Proc.Chem. Soc. 1961, 168.
(39) J ohnson, A. W.; Kay, I. T.; Rodrigo, R. J . Chem. Soc. 1963, 2336.
(40) Ramdhanie, B.; Stern, C. L.; Goldberg, D. P. J . Am. Chem. Soc.
2001, 123, 9447.
(41) Chmielewski, P. J .; Latos-Gra z˘ y n´ ski, L.; Olmstead, M. M.;
Balch, A. L. Chem. Eur. J . 1997, 3, 268.
(42) Pacholska, E.; Chmielewski, P. J .; Latos-Gra z˘ y n´ ski, L. Inorg.
Chim. Acta 1998, 273, 184.
(
1
(
1
(29) Cai, S.; Walker, F. A.; Liccocia, S. Inorg. Chem. 2002, 39, 3466.
(30) Cai, S.; Liccocia, S.; Walker, F. A. Inorg. Chem. 2001, 40, 5795.
(31) Brodhurst, M. J .; Grigg, R.; J ohnson, A. W. J . Chem. Soc.,
Perkin Trans.1 1972, 1124.
32) Narayanan, S. J .; Sridevi, B.; Chandrashekar, T. K.; Englich,
U.; Ruhlandt-Senge, K. Org. Lett. 1999, 1, 587.
33) Sridevi, B.; Narayanan, S. J .; Chandrashekar, T. K.; Englich,
U.; Ruhlandt-Senge, K. Chem. Eur. J . 2000, 6, 2554.
(
(
(43) Chmielewski, P. J .; Latos-Gra z˘ y n´ ski, L. Inorg. Chem. 1998, 37,
4179.
J . Org. Chem, Vol. 67, No. 16, 2002 5645

Pawlicki, M.
SCHEME 1
is able to create the direct pyrrole-furan R-R bond. The
synthesis resembles that which led to formation of 21,23-
dioxaporphyrin but requires an R-R condensation be-
tween the pyrrole and furan rings of 2.41 A similar step
has been previously suggested in the process of formation
of monoxacorrole.35 The identity of 3 has been confirmed
F IGURE 1. Electronic spectra of (21,23-O Cor)H 3 (solid line),
2
+
II
(21,23-O
2
Cor)H
2
2
3-H (dashed line), and (21,23-O Cor)Ni Cl
1
by high-resolution mass spectrometry, H NMR spectros-
7 (dotted line) in dichloromethane.
copy, and X-ray crystallography.
Sp ectr oscop ic Ch a r a cter iza tion of 21,23-Dioxa -
cor r ole. 5-Phenyl-10,15-bis(p-tolyl)-21,23-dioxacorrole 3
demonstrates spectroscopic properties typical of corroles
and core-modified corroles. The UV-vis spectrum of 3 is
triarylcorrole-like. The spectrum presents a markedly
split Soret band (397 and 422 nm) (Figure 1) and a series
of Q-bands in the 480-640 nm range. Presumably, the
split Soret band reflects the symmetry lowering due to
the trans localization of two oxygen atoms, and this
feature is preserved after protonation. The isosbestic
points corresponding to a single protonation steps have
been detected in the course of titration of a dichlo-
romethane solution of 3 with TFA followed by electronic
spectroscopy. The acid titration is accompanied by a
distinct color change from violet to blue-green.
1
The complete assignment of all H NMR resonances
for 3, shown in Figure 2, has been obtained by means of
1
2
D H NMR COSY and NOESY experiments using the
unique NOE correlation between H(3)-o-H(5-phenyl) as
a starting point. All perimeter furan [9.53 (H(2)), 9.14
3
(
H(3)) (AB, J AB ) 4.2 Hz), 9.30 (H(13)), 8.94 (H(12)) (AB,
3
J ) 4.6 Hz)] and pyrrole [8.96 (H(7)), 8.70 (H(8)) (AB,
J ) 4.6 Hz), 9.24 (H(18)), 8.83 (H(17)) (AB, J ) 4.2 Hz)]
3
3
are downfield shifted due to the ring current effect.
Essentially, molecule 3 preserves the aromaticity of the
parent corrole. Consistent with the aromacity of 3, the
broad NH resonance has been located at -2.53 ppm (298
K).
2
1,23-Dioxacorrole 3 tautomerizes via a rapid exchange
of the NH proton between two structurally unequivalent
nitrogen atoms of 3′ and 3′′ as seen in Scheme 2.
Significant spectral changes have been detected in vari-
1
able-temperature H NMR studies carried out for 3 in
dichloromethane-d
2
solutions (Figure 2, traces A and B).
F IGURE 2. 1H NMR spectra: (A) (21,23-O
2
Cor)H (dichlo-
Cor)H (dichloromethane-
As the temperature gradually decreases, the resonances
H(2), H(13), H(7), and H(8) broaden selectively. Even at
the lowest temperature studied (188 K in dichloromethane-
romethane-d
2
, 233 K), (B) (21,23-O
2
+
d
2
, 298 K, (C) (21,23-O
2
Cor)H
2
(TFA/dichloromethane-d ), 1/5
2
v/v, 298 K). Insets (not to scale) in traces B and C present the
NH resonances. Peak labels follow systematic position num-
bering from Scheme 3 or denote proton groups: o, m, psortho,
meta, and para positions of meso-phenyl (Ph) or meso-p-tolyl
2
d ) the dynamic process is still close to the fast exchange
limit and a single, eventually very broad line is seen for
each dynamically related couple. We have concluded that
a low exchange rate has not been achieved at the
accessible low-temperature limits of chlorinated solvents.
Hypothetically, two well-resolved AB sets corresponding
to 3′ and 3′′, respectively, are expected for each five-
(Tol) rings, respectively.
membered ring once the process is determined to be slow
on the H NMR time scale. Interestingly, the markedly
different dynamic behavior can be observed even for
1
5
646 J . Org. Chem., Vol. 67, No. 16, 2002

5
,10,15-Triaryl-21,23-dioxacorrole
SCHEME 2
doublets that belong to the same AB multiplet, e.g., H(2)
and H(3); H(13) and H(12). Presumably the chemical shift
difference determined for exchangeable pairs H(2)-3′,
H(2)-3′′; H(13)-3′, H(13)-3′′; H(7)-3′, H(7)-3′′; and H(8)-
3
′, H(8)-3′′ are in the range where the slow exchange limit
is approached but above the collapsing point. The shift
differences for the accompanying dynamic pairs H(3)-3′,
H(3)-3′′; H(12)-3′, H(12)-3′′; H(17)-3′, H(17)-3′′, and H(18)-
3
′, H(18)-3′′ are markedly smaller. Eventually, the slightly
dynamically broadened lines assigned to these hydrogen
atoms could be seen at low-temperature limits. It is
important to notice that even at 298 K the exchange of
NH protons play an essential role. It is clearly demon-
strated by the pronounced differences in the line width
of the AB multiplets as reflected by peculiar differences
in heights of scalar coupled doublets (Figure 2, traces A
and B). All chemical shifts varied as temperature de-
creased, which is due to changes in populations of the
two tautomers.
F IGURE 3. Crystal structure of the 5,10,15-triaryl-21,23-
dioxacorrole cation of [(21,23-O Cor)H [ZnCl ] (top, perspec-
tive view; bottom, side-view phenyl groups omitted for clarity).
The N(1)‚‚‚N(2) distance ) 3.685 Å. The vibrational ellipsoids
represent 50% probability.
2
2
]
2
4
1
The H NMR spectroscopic titration with TFA carried
out in dichloromethane-d at 228 K demonstrated that
2
the monocation allowed the avoidance of the broadening
due to tautomeric equilibria seen for neutral 3). In
general, all shifts are in the range expected for a corrole
or an aromatic heterocorrole.
the addition of the proton results in a smooth change of
the chemical shifts, which suggests fast exchange be-
tween 3 and 3-H and facilitates resonance assignment
via the straightforward correlation of shifts between the
neutral and cationic forms. Protonation takes place at
nitrogen atoms, as documented by a rise of two NH
resonances at -1.46 and -1.98 ppm (Figure 2, trace C).
The protonation is accompanied by the downfield shift
of â-H furan resonances and the upfield relocation of â-H
pyrrole resonances. Importantly, the shift of NH protons
is strongly dependent on the choice of acid (TFA, -1.46,
2 2 2 4
Cr ysta l Str u ctu r e of [(21,23-O Cor )H ] [Zn Cl ].
The structure has been studied by X-ray crystallography.
The perspective views of the molecule are shown in
Figure 3.
The cation is only slightly distorted from planarity as
seen in Figure 3 despite two NH protons in the center.
The hydrogen atoms of the NH groups were clearly
located in a difference map, and their positions were
subsequently refined. The geometry of tetrachlorozinc-
II
-
1.98 ppm; HCl, -0.83, -0.9 ppm), which implies an
(II) anion is typical. The Zn -Cl distances of 2.277(1),
interaction between the 21,23-dioxacorrole monocation
and the respective anion. The essential differences of the
chemical shifts and spectral patterns reflect immediately
2.307(1), 2.277(1), and 2.307(1) Å are comparable with
2
- 46,47
the 2.245-2.289 Å range reported for ZnCl
anion is located in a clam-shell like cavity formed by two
21,23-dioxacorrole cations of the [(21,23-O Cor)H)
[ZnCl ] unit (Figure 4). The dihedral angle between the
4
.
The
4
4,45
the different properties of counteranions.
2
2 2
] -
The monocationic form(3-H)TFA becomes the major
4
species at the 1:1 macrocycle to TFA molar ratio (Figure
21,23-dioxacorole planes equals 61.5°. There are three
2
, trace C). In further steps of the titration (not shown),
(Zn)Cl‚‚‚HC hydrogen bonding interactions of the trifur-
2
-
all â-H resonances moved gradually downfield. Pre-
sumably, the independent interaction of the (3-H)TFA
ionic aggregate with the bulk of TFA through a net-
work of hydrogen bonds accounts for these changes. Such
a behavior was previously detected in titrations of
cate geometry between the Cl(1) anion of ZnCl
4
and two
â-H and ortho-H ((â-C)H)‚‚‚Cl, 2.8 Å (2.8 Å), ((â-C)-H)‚‚
‚Cl, 118.1° (128.3°); ((o-C)H‚‚‚Cl), 2.8 Å, ((o-C)-H‚‚‚Cl,
149°). Both hydrogen atoms involved in the interaction
2 2 2 4
are located on the adjacent [(21,23-O Cor)H) ] [ZnCl ]
5
,10,15,20-tetraphenylsaphyrin or 2-N-methyl-5,10,15,20-
fragment which points into the open side of the clam-
like cavity toward the chloride. In addition, the Cl(2)
interacts with two hydrogen atoms (see the figure in the
Supporting Information).
4
4,45
tetraphenyl-21-carbaporphyrin with TFA.
The HMQC and HMBC studies resulted in the full
assignment of all 13C resonances of 3-H (the studies on
(
44) Chmielewski, P. J .; Latos-Gra z˘ y n´ ski, L. J . Chem.Soc., Perkin
Trans. 2 1995, 503.
45) Rachlewicz, K.; Sprutta, N.; Latos-Gra z˘ y n´ ski, L.; Chmielewski,
P. J .; Szterenberg, L. J . Chem. Soc., Perkin Trans. 2 1998, 959.
(46) Buckingham, D. A.; Clark, C. R.; Rogers, A. J .; Simpson, J .
Inorg. Chem. 1995, 34, 3646.
(47) Ma, Y.; Reardon, D.; Gambarotta, S.; Yap, G.; Zahalka, H.;
Lemay, C. Organometallics 1999, 18, 2773.
(
J . Org. Chem, Vol. 67, No. 16, 2002 5647

Pawlicki, M.
F IGURE 5. Electronic spectra of 6 (solid line) and 6-H+
(dashed line) in dichloromethane.
product identified in the reaction was 5,10,15,20-tetra-
(p-tolyl)-21,23-dioxaporphyrin.
Formally, structures 3, 5, and 6 preserve the common
F IGUR E 4. Views of a clam-shell-like arrangement of the
(21,23-O Cor)H) [ZnCl ] unit.
fragment of 21,23-dioxacorrole that is related to the
acyclic 5,10-bis(p-tolyl)-14-(phenylhydroxymethyl)-16-
oxatripyrrin. In 3 and 6, both ends of the acyclic chain
are linked by the furan ring at the R and R′ positions for
and the â and â′ positions for 6. The â-R′ connectivity
of furan in the hypothetical 5 could not be realized in
the described reaction conditions.
Sp ectr oscop ic Ch a r a cter iza tion of th e 21,23-Di-
oxa cor r ole Isom er . The electronic spectrum of 6 and
its monocation is presented in Figure 5. The UV-vis
spectrum of 3 is different from that detected for the
isomeric 21,23-oxacorrole and its monocation. A split
Soret band has been observed at 375 and 409 nm
accompanied by a broad band at 753 nm.
[
2
2
]
2
4
There is an appreciable effect from the aromatic
character of the macrocycle on the furan portions. The
-C and C -C bond lengths are practically identical.
Thus, in these macrocycles, the C -C distances are
3
C
R
â
â
â
R
â
longer and the C
â
â
-C distances are shorter than in free
furan.48 These bond changes indicate that the π delocal-
ization of the furan ring is altered in 21,23-dioxacorrole.
A similar influence of the aromatic macrocycle on the
delocalization pattern in the furan ring was observed in
4
9
the case of tetraoxa[18]porphyrin (1.1.1.1) dication,
5
0
ozaphyrin, 21-oxaporphyrin, and 21,23-dioxaporphy-
rin.41
The isosbestic points corresponding to a single proto-
nation step have been detected in the course of titration
of a dichloromethane solution of 6 with TFA, followed
by electronic spectroscopy. The broad band of 6-H shows
a remarkably bathochromic shift to 962 nm. The acid
titration is accompanied by a distinct color change from
green to brown. The electronic spectra resemble those of
other porphyrin related molecules which preserve con-
jugation in the tripirryne fragment but delocalization
through the macrocycle is blocked by the completing
linkage, e.g., 6,11,16,21-tetraphenyl-m-benziporphyrin
Syn th esis a n d Ch a r a cter iza tion of th e 21,23-
Dioxa cor r ole Isom er w ith a P r otr u d in g F u r a n
Rin g. In the course of our investigations on 21,23-
dioxacorrole, we have realized that the replacement of
2
-phenylhydroxymethylfuran 2 with 3-phenylhydroxy-
methylfuran 4 should provide the similar spatial ar-
rangement in the course of condensation as that seen at
Scheme 1, also providing an access to the reactive R
position. Potentially the condensation involving 1 and 4
and pyrrole could result in 5, i.e., an isomer of 3 with a
resembling structural skeleton. The structure 5 results
form the formal reshuffling of the oxygen atom and the
(
neutral, 723, dication 920 nm)51 or 5,10,15,20-tetraphe-
nyl-2-thia-21-carbathiaporphyrin (neutral 697, 756, di-
cation 908 nm).5
2,53
2
-CH group of 21,23-dioxacorrole to give 21-carba-2,23-
1
The complete assignment of 6 all H NMR resonances
dioxacorrole 5.
1
shown in Figure 6 has been obtained by means of H
Contrary to our expectation based upon steric reasons
and the known reactivity differences between the R and
â positions of furan, the condensation has taken place at
the only available and sterically hindered â position. As
the result, we have obtained 6, i.e., an isomer of 3, with
a protruding furan ring. The only other macrocyclic
NMR COSY and NOESY experiments using the H(4)-
o-H(6-phenyl) ring and H(2)-H(19) dipolar correlations
as a starting point for the analysis of connectivity. For
topological reasons, the molecule 6 cannot retain mac-
rocyclic aromacity typical of porphyrins or corroles. The
1
H NMR spectrum of 6 presents the â-H resonances at
positions consistent with a nonaromatic structure (6.87
(
48) Forume, R. Acta Crystallogr., Sect. B: Struct. Sci. 1972, 28,
984.
49) Vogel, E.; D o¨ rr, J .; Herrmann, A.; Lex, J .; Schmickler, H.;
4
(H(2)), 6.29 (H(4)), J ) 2.1 Hz; 6.39 (H(8)), 5.88 (H(9)),
2
(
Walgenbach, P.; Gisselbrecht, J .-P.; Gross, M. Angew. Chem., Int. Ed.
Engl. 1993, 32, 1600.
(51) St e¸ pie n´ , M.; Latos-Gra z˘ y n´ ski, L. Chem. Eur. J . 2001, 7, 5113.
(52) Sprutta, N.; Latos-Gra z˘ y n´ ski, L. Tetrahedron Lett. 1999, 40,
8457.
(50) Miller, D. C.; J ohnson, M. R.; Becker, J . J .; Ibers, J . A. J .
Heterocycl. Chem. 1993, 30, 1485.
(53) Sprutta, N. Ph.D. Thesis, University of Wroclaw, 2001.
5
648 J . Org. Chem., Vol. 67, No. 16, 2002

5
,10,15-Triaryl-21,23-dioxacorrole
TABLE 1. Selected Bon d Len gth s of 6
6
furan of
regular
protruding
furan
21-oxaporphyrin
O-CR
CR-Câ
Câ-Câ
1.397(3)
1.429(3)
1.363(3)
1.373(3)
1.356(3)
1.461(3)
1.370
1.322
1.425
1.380(4)
1.403(4)
1.363(4)
F IGURE 6. 1H NMR spectra of 6: (A) 6 (chloroform-d, 298
K), (B) 6-H (chloroform-d, 298 K). Peak labels follow systematic
position numbering of the macrocycle ring or denote proton
groups: o, m, psortho, meta, and para positions of meso-
phenyl (Ph) or meso-p-tolyl rings, respectively. Inset presents
the AA′BB′ multiplet of 11-p-tolyl as measured in dichlo-
2
romethane-d .
SCHEME 3
F IGURE 7. Crystal structure of (6-H)Cl (top, perspective
view; bottom, side-view phenyl groups omitted for clarity). The
vibrational ellipsoids represent 50% probability.
Cr ysta l Str u ctu r e of th e Cor r ole Isom er w ith a
P r otr u d in g F u r a n Rin g. The structure of (6-H)Cl was
determined by X-ray crystallography. A selection of
important bond distances is reported in Table 1.
The macrocycle is strongly puckered as its internal ring
is contracted by two carbon atoms when compared to a
regular porphyrin or by one when to corrole. The ar-
rangements of the furan and pyrrole rings is demon-
strated by the respective projections in Figure 7. In the
crystal, the monocation of 6 acts as an anion receptor.
Two NH groups are involved in the N-H‚‚‚Cl hydrogen
bond. The hydrogen bond distances N(1)‚‚‚Cl(1) of 3.136-
(2) Å and N(2)‚‚‚Cl(1) of 3.111(2) Å are in the limits found
for other coordination of chloride anions by porphyrins
or expanded porphyrins cations.54
In the crystal, pairs of molecules are positioned about
the center of symmetry however without any face-to-
face π-π contact. Two molecules of any dimeric units
do not overlay. Their arrangement is best seen in Figure
8. The view is oriented so that one looks upon two nearly
parallel planes of the protruding furan rings and pre-
sents three molecules engaged in interaction with the
same chloride anion. The separation between the mean
plane of protruding rings equals 2.59 Å and the regular
ones 3.22 Å. The chloride-chloride separation is 7.235-
(2) Å. Figure 8 reveals the interesting aspect of the
structure. There are two intermolecular hydrogen bond-
ing interactions: C(52)H‚‚‚Cl(1), (H‚‚‚Cl(1), 2.58 Å; C(52)-
3
3
J ) 4.8 Hz; 6.24 (H(14)), 6.11 (H(11)), J ) 4.8 Hz; 5.87
3
(
H(19)), 5.75 (H(18)), J ) 4.1 Hz). The marked downfield
shift of the NH resonance at 17.71 ppm is convincing in
this matter. Scalar coupling NH to H(18) and H(19),
detected in COSY, is consistent with the prevalence of
the tautomer 6 presented in Scheme 3.
The resonances of 6-phenyl and 16-p-tolyl present,
respectively, as the AA′ BB′ and AA′BB′C spectroscopic
patterns expected for meso-aryls. The ortho and meta
protons of 11-p-tolyl are accidentally isochronous and so
behave as a group of chemically equivalent nuclei,
showing no internal coupling. They present an A
in chloroform-d. Changing the solvent to dichloromethane-
(Figure 6, trace A, inset) or protonation led to changes
4
singlet
d
2
in the chemical shifts, and the normal AA′BB′ spectrum
of p-tolyl was then observed. The H NMR spectroscopic
titration with TFA carried out in chloroform-d at 298 K
takes place at nitrogen atoms, as documented by the
appearance of two NH resonance at 16.63 and 16.53 ppm
1
(Figure 6, trace B).
(54) Stone, A.; Fleischer, E. B. J . Am. Chem. Soc. 1968, 90, 2735.
J . Org. Chem, Vol. 67, No. 16, 2002 5649

Pawlicki, M.
MCl and H-C groups have also been documented for
halide complexes of the early transition metal ions,
nobium, iridium, rhodium and platinium where the
5
7-59
H‚‚‚Cl distance varies over a range of 2.38-2.94 Å.
In the literature, the (C)H‚‚‚Cl distance has been con-
sidered as the criterion of interaction andsat presents
seems to be accepted as a sign of the (C)H‚‚‚Cl hydro-
gen bond. The determined (C)H‚‚‚Cl distances for
(6-H)Cl and for discussed above [(21,23-O
2 2 2
Cor)H) ] -
[
ZnCl ] are in the limit attributed to such interactions.
4
The chloride anion Cl(1) of (6-H)Cl is involved in two
intra- and two intermolecular Cl‚‚‚H interactions that are
classified as a tetrafurcate system.58 A net of hydrogen
bonds (C)H‚‚‚Cl and (N)H‚‚‚Cl is extended on the whole
crystal structure.
Examination of the crystallographic data demonstrated
that the π bonds in the oxatripirryn unit are largely
localized in the manner indicated at the valence structure
F IGURE 8. Views of (6-H )Cl showing the chloride-HC
2
interactions between adjacent molecules in the solid.
6
. The comparison of bond lengths of two furan moieties
is particularly important in the analysis. The “protrud-
ing” furan ring preserves all features of the isolated furan
and the bond lengths are practically unperturbed, i.e.,
C
â
-C
gation on the second furan moiety. Here, the C
distances are longer and the C
â
> C
R
-C
â
. There is an appreciable effect of conju-
-C
distances are shorter
R
â
â
-C
â
than in the free furan.48 These bond changes indicate that
the π delocalization through the furan ring is altered.
A similar influence on the π delocalization pattern in the
furan ring has been observed in the case of aromatic
2
1,23-dioxacorrole as discussed above.
DF T Ca lcu la tion s. 5-Phenyl-10,15-bis(p-tolyl)-21,23-
dioxacorrole and its isomer with the protruding furan
ring contain only one exchangeable proton, and a feasible
tautomeric process may involve two accessible nitrogen
positions (Schemes 1 and 2). Consequently, the experi-
mentally observed tautomeric equilibrium for neutral
forms of 3 and the presence of a single form for 6 have
raised the question of the relative stability of the involved
tautomers. To approach this problem we have applied the
density functional theory (DFT) in the similar way as
previously described for inverted porphyrins, sapphyrin,
diheterosapphyrins or selenaporphyrin.6
0-63
The den-
sity functional theory methods and the high level of ab
initio calculations have been recently applied to porphy-
rins, porphyrin isomers, metalloporphyrins, and related
systems.6
0-66
In order of simplification of all calculations the corre-
sponding phenyl and p-tolyl groups of 3 or 6 have been
(57) J ames, S. L.; Verspui, G.; Spek, A. L.; van Koten, G. Chem.
Commun. 1996, 1309.
F IGURE 9. DFT-optimized structures of tautomers of 3 and
(58) Huang, L.-Y.; Aulwurm, U. R.; Heinemann, F. W.; Knoch, F.;
Kisch, H. Chem. Eur. J . 1998, 4, 1641.
6
. Projections emphasize the conformations of the macrocycle.
(59) Spaniel, T.; G o¨ rls, H.; Scholz, J . Angew. Chem., Int. Ed. Engl.
1
6
3
998, 37, 1862.
H‚‚‚Cl(1), 155.9°; C(2′)H‚‚‚Cl(1), (H‚‚‚Cl(1)), 2.75 Å, C(2)-
H‚‚‚Cl, 156.4°.
The intra and intermolecular C-H‚‚‚Cl interactions are
still quite uncommon.55 The relevant Cl‚‚‚HC distances
in organic compounds are in the 2.57-2.94 Å range and
the majority of these systems contain the chloride anion.56
Intermolecular and intramolecular interactions between
(60) Szterenberg, L.; Latos-Gra z˘ y n´ ski, L. Inorg. Chem. 1997, 36,
287.
(61) Szterenberg, L.; Latos-Gra z˘ y n´ ski, L. THEOCHEM 1999, 490,
3.
(62) Pacholska, E.; Latos-Gra z˘ y n´ ski, L.; Szterenberg, L.; Ciunik, Z.
J . Org. Chem. 2000, 65, 8188.
63) Szterenberg, L.; Latos-Gra z˘ y n´ ski, L. J . Porphyrines Phthalo-
cyanines 2001, 5, 474.
64) Ghosh, A. Quantum Chemical Studies of Molecular Structures
(
(
and Potential Energy Surfaces of Porphyrin and Hemes. In The
Porphyrin Handbook; Kadish, K. M., Smith, K. M., Guilard, R., Eds.;
Academic Press: New York, 2000; pp 1-35.
(
55) Gibb, C. L. D.; Stevens, E. D.; Gibb, B. C. J . Am. Chem. Soc.
001, 123, 5849.
56) Taylor, R.; Kennard, O. J . Am. Chem. Soc. 1982, 104, 5063.
2
(65) Ghosh, A. Angew. Chem., Int. Ed. Engl. 1995, 34, 1028.
(66) Vanber, T.; Ghosh, A. J . Am. Chem. Soc. 1999, 121, 12154.
(
5
650 J . Org. Chem., Vol. 67, No. 16, 2002

5
,10,15-Triaryl-21,23-dioxacorrole
TABLE 2. Ca lcu la ted En er gies
compd
B3LYP/6-31G**//B3LYP/6-31G*a
relative energyb
3
3
6
6
′
′′
′
-991.1672
-991.1649
-991.1368
-991.1346
0
1.44
0
′′
1.38
a
Hartree. b Energies in kilocalories per mole.
replaced by hydrogen atoms. The density functional
theory calculations have been carried out using geometry
determined by X-ray crystallography as a starting point
of the DFT optimization procedure. The optimized struc-
tural parameters are contained in the Supporting Infor-
mation. The optimized bond lengths (Figure 9) resemble
those found by X-ray crystallography. The differences
between the bond lengths between the DFT optimized
and crystal values are in the range of a few hundredths
of an angstrom.
1
II
F IGUR E 10. H NMR spectra: (A) (2,23-O Cor)Ni Cl, (B)
(21,23-O
2
II
2 4 2
Cor-d )Ni Cl in dichloromethane-d at 298 K. Labels:
pyrr, pyrrole; f, furan.
and 6. Previously, we documented that this ion is easily
bound by 21-heteroporphyrins including 21-oxaporphy-
rin.2
1,41
The size of the coordination core of porphyrins
It is apparent that the DFT-optimized skeleton of 3 is
practically planar for each tautomer. The DFT optimized
(heteroporphyrins) was suggested to be instrumental as
the controlling factor of nickel porphyrin and nickel
heteroporphyrin properties.
Insertion of nickel(II) into 5,10,15-triaryl-21,23-diox-
aporphyrin has been readily achieved using the Adler
method, i.e., boiling a mixture of 3 and nickel(II) chloride
+
structure of 6′(N(21)H,N(23)), 6′′(N(21),N(23)H), 6-H are
nearly planar as well. Thus, the strong folding of (6-H)-
Cl observed in the crystal has not been reproduced.
Therefore, the real preference of geometry in the
crystal may be finally determined by other factors, not
directly included into the DFT optimization. For instance,
this structural difference can be related to the marked
overlap within the pair of molecules detected in the
crystal structure. The presence of the bulky aromatic
meso substituents can be of importance. In this case, the
established influence of the methyl substitution on
geometry of sapphyrin is particularly informative.61
Analogously, it was recently demonstrated that softness
of the ruffling deformation of regular porphyrins limits
possibility to accurate reproduce a solid-state structure
by molecular calculation.66
in DMF. The reaction results in the formation of a five-
coordinate (21,23-O
II
2
Cor)Ni Cl complex. The severe crowd-
ing in the core of 6 seems to be responsible for the fact
that this molecule was completely resistant toward
coordination of nickel(II) in conditions probed for 3.
The electronic absorption spectra of 7 is included in
Figure 1. The corrole-like spectrum is present for 7 with
a Soret band and the Q-bands. The complex 7 is para-
magnetic as clearly demonstrated by H NMR spectrum
with well resolved set of downfield shifted eight â-H
resonances consistent with its C
1
1
symmetry in positions
The calculated total energies, using the B3LYP/6-
typical for high-spin, five-coordinate nickel(II) heteropor-
phyrins2
1,41,43
or nickel(II) carbaporphyrinoids.
71,72
3
1G**//B3LYP/6-31G* approach (Table 2) demonstrate
that relative stability of postulated tautomers increases
in the order 3′ > 3′′ and 6′ > 6′′. The 3′ form of (O Cor)H
The detected differentiation of o- and m-phenyl reso-
nances suggests that the phenyl rotation with respect to
the Cmeso-Cphenyl bond is slow. Apparently, two sides of
2
is only slightly more stable as shown by the DFT studies
as the energy difference between 3′ and 3′′ equals 1.4
kcal/mol. At present the appropriate experimentally
determined thermodynamic values to compare quanti-
tatively the calculated relative stability of tautomers are
not accessible. However the small energy difference
between 3′ and 3′′ accounts for their simultaneous
presence in equilibrium as evidenced by VT dependence
of the spectroscopic pattern discussed above. The re-
lated correlation between the DFT determined rela-
tive stability and NMR dynamic behavior have been
discussed for tautomerism of hemiporphycene and
dihetrosapphyrins.5
the corrole macrocycle are not equivalent, as expected
II
for the five-coordinate (21,23-O
2
Cor)Ni Cl complex. The
resonance assignments, which are given above each peak
in Figure 10, have been made on the basis of relative
intensities, line widths, site-specific deuteration, and 2D
COSY experiments.
This particular spectroscopic observation demonstrates
that modification of the corrole macrocyle by virtue of
replacement of NH group(s) by one or two oxygen donors
controls the ground electronic state of the resulting nickel
corrolates. Thus, in addition to low-spin nickel(II) corrole
8,67-70
27
30
π-cation radical and diamagnetic nickel(II) oxacorole,
F or m a tion of a Nick el Com p lex. In preliminary
studies, we have probed the coordination properties of 3
the formation for first time of the high-spin nickel(II)
21,23-dioxacorole has been achieved.
(
67) Wu, Y.-D.; Chna, K. W. K.; Yip, C.-P.; Vogel, E.; Plattner, A.
A.; Houk, K. N. J . Org. Chem. 1997, 62, 9240.
68) Vogel, E.; Br o¨ ring, M.; Weghorn, S. J .; Scholz, P.; Deporte, L.;
Con clu sion
(
The modification of the corrole core by introduction of
an oxygen instead of the NH group deeply modified
Lex, J .; Schmickler, H.; Schaffner, K.; Baslavsky, S. E.; M u¨ ller, M.;
P o¨ rting, S.; Fowler, C. J .; Sessler, J . L. Angew. Chem., Int. Ed. Engl.
1
997, 36, 1651.
69) Rachlewicz, K.; Sprutta, N.; Chmielewski, P. J .; Latos-Gra z˘ y n´ -
ski, L. J . Chem. Soc., Perkin Trans. 2 1998, 969.
70) Szterenberg, L.; Latos-Gra z˘ y n´ ski, L. J . Phys. Chem. A 1999,
03, 3302.
(
(71) Chmielewski, P. J .; Latos-Gra z˘ y n´ ski, L.; Glowiak, T. J . Am.
Chem. Soc. 1996, 118, 5690.
(72) Chmielewski, P. J .; Latos-Gra z˘ y n´ ski, L. Inorg. Chem. 2000, 39,
5639.
(
1
J . Org. Chem, Vol. 67, No. 16, 2002 5651

Pawlicki, M.
macrocyclic coordinating properties. It is important to
notice that this replacement is expected to preserve the
size of the macrocyclic core considering similarity of
oxygen and nitrogen atom radii analogously as demon-
strated for porphyrins and oxaporphyrins. The introduc-
tion of oxygen changes the charge of the resulting ligands
alumina (grade III), and the slow-moving blue fraction was
eluted with dichloromethane and evaporated to dryness.
Recrystallization of 3 as a cation(HCl) from dichloromethane/
+
hexane (1:1 v/v) produced 48 mg of [3-H] (yield 8%).
(
21,23-O
4.88), 495 (3.91), 538 (4.12), 595 (3.93), 637 (4.07).
21,23-O Cor )H
+. UV-vis (λmax (nm) (log ꢀ)): 395 (5.09),
2
Cor )H. UV-vis (λmax (nm) (log ꢀ)): 397 (4.89), 422
(
(
2
2
(-3, corrole; -2; 21-oxacorrole; -1, 21,23-dioxacorrole).
4
21 (4.93), 533 (3.99), 564 (4.06), 601 (4.45).
(
Their potential in control of coordinating properties of
the metal ion has been demonstrated using the selected
case of nickel(II) where for the very first time the high-
spin nickel(II) has been detected in the corrole like
shrunk macrocyclic environment.
1
21,23-O
2
Cor )H. H NMR (500.13 MHz, CDCl
3
): 9.53 (d,
3
3
3
1
)
H, J ) 4.21 Hz), 9.30 (d, 1H, J ) 4.59 Hz), 9.24 (d, 1H, J
3
3
4.21 Hz), 9.14 (d, 1H, J ) 4.21 Hz), 8.96 (d, 1H, J ) 4.59
3 3
Hz), 8.94 (d, 1H, J ) 4.59 Hz), 8.83 (d, 1H, J ) 4.21 Hz),
3
3
8.70 (d, 1H, J ) 4.59 Hz), 8.32 (d, 2H, J ) 6.89 Hz), 8.22 (d,
3
3
3
2
)
H, J ) 7.65 Hz), 8.07 (d, 2H, J ) 8.03 Hz), 7.83 (t, 2H, J
The novel building block 2-furancarbinol has been
introduced to produce diheterocorroles. This methodology
provides the route to family of heterocorroles, which can
act as monoanionic ligands. The formation of the 21,23-
dioxaporphyrin isomer with a protruding furan ring
confirms an ability of the furan molecule to act in acid
or Lewis acid catalyzed condensation as provider of
different structurally building blocks: regular (R-R′),
short (â-â′ or R-â), and eventually inverted (R-â′).
Interestingly, the R-â connectivity was detected in
furochlorphin, which contains an exocyclic furan ring,
albeit this molecule is obtained in the course of aerobic
oxidation of 1,2,3,7,13,17,18,19-octamethyl-8,12-diethyl-
octadehydrocorrinatonickel(II) chloride.73
3
3
6.89 Hz), 7.78 (d,1H, J ) 7.60 Hz), 7.64 (d, 2H, J ) 7.65
3
Hz), 7.58 (d, 2H, J ) 8.03 Hz), 2.72 (s, 3H), 2.71 (s, 3H).
+
13
(
21,23-O
2
Cor )H
2
.
3
C NMR (125.7 MHz, CDCl ); 154.89,
1
1
1
52.62, 148.46, 144.27, 141.32, 139.06, 138.57, 137.77, 137.66,
37.54, 135.61, 135.54, 135.27, 135.09, 135.07, 129.30, 128.97,
28.57, 128.46, 128.34, 127.94, 127.14, 127.03, 126.07, 125.24,
123.28, 118.89, 117.48, 116.99, 115.87, 110.89, 21.53, 21.51.
HRMS (ESI, m/z): 557.2224 (557.2229 calcd for C39
28 2 2
H N O
+
+
H ).
Isom er of 21,23-Dioxa cor r ole, 6. 2,5-Bis(phenylhydroxy-
methyl)furan (392 mg, 1.27 mmol), 3-(phenylhydroxymethyl)-
furan (221 mg, 1.27 mmol), and pyrrole (0.176 mL, 2.54 mmol)
were added to deoxygenated dichloromethane (150 mL). After
addition of boron trifluoride etherate (50.4 µL), the reaction
mixture was stirred in the dark. DDQ (0.721 g, 3.175 mmol)
was added, and the solution was stirred for 20 min. The
resulting mixture was evaporated to dryness under reduced
pressure by rotatory evaporation. The dark residue was
dissolved in dichloromethane and chromatographed on a basic
alumina column. The green fraction was eluted with dichlo-
romethane and evaporated to dryness. Recrystallization from
dichloromethane/hexane (1:1 v/v) of a cationic form (HCl) of 6
gave 31 mg (yield 4%).
Exp er im en ta l Section
P r ep a r a tion of P r ecu r sor s. 2,5-Bis(p-tolylhydroxymeth-
yl)furan was synthesized according to known procedures.74
3
-(P h en ylh yd r oxym et h yl)fu r a n . This compound was
synthesized in a one-pot synthesis by addition of 9 mL of 3 M
solution of phenylmagnesium bromide in diethyl ether to an
THF solution (100 mL) containing 2 mL (23 mmol) of 3-fural-
dehyde. After 30 min 40 mL of 1% sulfuric acid was added.
6. UV-vis (λmax (nm) (log ꢀ)): 375 (4.45), 409 (4.39), 753
(3.61).
Subsequently solid Na
CO ceased. The solution was extracted with diethyl ether
three times). All organic layers were collected and dried with
MgSO . After filtration and evaporation, a crude 3-(phenyl-
2
CO
3
was added until the liberation of
+
6
-H . UV-vis (λmax (nm) (log ꢀ)): 390 (4.51), 468 (4.34), 962
2
(
3.99).
6
(
1
. H NMR (500.13 MHz, CDCl
3
): 17.71 (s, 1H), 7.29 (m,
4
3
3
5
7
H), 7.20 (d, 2H, J ) 8.04 Hz), 7.13 (d, 2H, J ) 8.04 Hz),
hydroxymethyl)furan was obtained quantitatively, as a pale
4
3
.09 (s, 4H), 6.87 (d, 1H, J ) 2.1 Hz), 6.39 (d, 1H, J ) 4.8
1
yellow solid, and used without further purification. H NMR
4
3
Hz), 6.29 (d, 1H, J ) 2.1 Hz), 6.24 (d, 1H, J ) 4.8 Hz), 6.11
(
6
500 MHz, CDCl
.32 (s, 1H), 5.75 (s, 1H), 2.62 (s, 1H).
-(P h en ylh yd r oxym et h yl)fu r a n . This compound was
3
): 7.4 (m, 2H), 7.35 (m, 3H), 7.29 (m, 2H),
3
3
3
(
)
d, 1H, J ) 4.8 Hz), 5.88 (d, 1H, J ) 4.8 Hz), 5.87 (d, 1H, J
3
4.1 Hz), 5.75 (d, 1H, J ) 4.1 Hz), 2.35 (s, 3H), 2.32 (s, 3H).
2
+ 13
6
3
-H . C NMR (125.7 MHz, CDCl ): 168.93, 162.01, 153.44,
synthesized as 3-phenylhydroxymethylfuran using 2-furalde-
hyd instead of the 3-furaldehyde. Expected product was
obtained quantitatively as an orange oil. The compound is
1
1
1
1
51.5, 145.79, 143.52, 142.52, 141.24, 139.09, 138.59, 137.03,
35.12, 133.96, 132.58, 131.95, 130.66, 130.27, 130.06, 130.04,
29.41, 129.4, 127.84, 127.69, 126.67, 123.98, 123.93,122.29,
1
sufficiently pure (>95% by H NMR) for use in subsequent
19.95, 116.02, 107.39, 21.48, 21.24. HRMS (ESI, m/z): 557.2224
1
reactions. H NMR (500 MHz, CDCl
3
): 7.41 (m, 2H), 7.36 (m,
+
(
557.2229 calcd for C39
(21,23-O Cor )H) [Zn Cl
romethane and ZnCl (20 mg) in methanol (10 mL) were mixed
together, stirred for 1 h, and evaporated to dryness. (21,23-
Cor)H) [ZnCl ] was washed out from the solid residue and
H
28
N
2
O
2
+ H ).
3
3
3
H), 7.29 (m, 1H), 6.30 (m, 1H), 6.10 (s, 1H), 5.79 (d, 1H, J )
3
2
2
]
2
4 2
]. (21,23-O Cor)H (2 mg) in dichlo-
.4 Hz), 2.63 (d, 1H, J ) 3.4 Hz).
-P h en yl-10,15-bis(p-tolyl)-21,23-d ioxa cor r ole. 2,5-Bis-
phenylhydroxymethyl)furan (308 mg, 1 mmol), 2-(phenylhy-
2
5
(
O
2
2
]
2
4
droxymethyl)furan (174 mg, 1 mmol), and pyrrole (0.14 mL, 2
mmol) were added to deoxygenated dichloromethane (100 mL).
After addition of boron trifluoride etherate (50.4 µL), the
reaction mixture was stirred in the dark. p-Chloranil (0.6147
g, 2.5 mmol) was added, and the solution was heated under
reflux (1 h) and then evaporated to dryness under reduced
pressure by rotatory evaporation. The dark residue was
dissolved in dichloromethane and chromatographed on a basic
alumina column to remove tarry products. A chloroform
fraction was immediately chromatographed again on basic
recrystallized from dichloromethane/hexane (yield, 4 mg).
II
(
21,23-O
2
Cor )Ni Cl. A 56 mg (0.1 mmol) portion of 3 and
6
00 mg (3 mmol) of NiCl
2
2
‚4H O were dissolved in 50 mL of
DMF. After 2 h of refluxing, the solvent was removed in a
stream of nitrogen. The remaining solid was dissolved in
freshly distilled dichloromethane and filtered to remove inor-
ganic salt. The solution was chromatographed on silica gel
(
mesh 35-70), and the expected product was eluted with
chloroform as a deep green band. Recrystalization from
chloroform/hexane (50/50 v/v) yielded 18 mg (27%) of (21,23-
II
O
2
Cor)Ni Cl.
(
73) Chang, C. K.; Wu, W.; Chern, S. S.; Pen, S. M. Angew. Chem.,
Int. Ed. Engl. 1992, 31, 70.
74) Latos-Gra z˘ y n´ ski, L.; Pacholska, E.; Chmielewski, P. J .; Olm-
stead, M. M.; Balch, A. L. Angew. Chem., Int. Ed. Engl. 1995, 34, 2252.
II
(
2
21,23-O Cor )Ni Cl. UV-vis (λmax (nm)): 400, 439, 529,
(
567, 620. MS (ESI, m/z): 613.14 (613.1426 calcd for [C39
H
27
N
2
O
2
-
+
Ni] ).
5
652 J . Org. Chem., Vol. 67, No. 16, 2002

5
,10,15-Triaryl-21,23-dioxacorrole
P r ep a r a tion of sa m p les. Dichloromethane-d
roform-d used for NMR samples were passed through basic
2
and chlo-
romethene solution contained in a thin tube. Data were
collected at 100 K on a Kuma KM-4 CCD diffractometer. The
data were corrected for Lorentz and polarization effects. No
absorption correction was applied. Crystal data are compiled
in Table S1 (Supporting Information).
alumina before use. The solution of the trifluroacetic acid in
1
dichloromethane-d
2
was added by syringe to the H NMR tube
containing 3 or 6 as a neutral form. The progress of the
1
reaction was followed by H NMR spectroscopy.
The structures were solved by direct methods with SHELXS-
In str u m en ta tion . NMR spectra were recorded on a Bruker
Avance 500 spectrometer. Absorption spectra were recorded
on a diode-array Hewlett-Packard 8453 spectrometer.
Mass spectra were recorded on an AD-604 spectrometer
using the electrospray and liquid matrix secondary ion mass
spectrometry techniques.
9
7 and refined by full-matrix least-squares method using
SHELXL-97 with anisotropic thermal parameters for the
non-H atoms. Scattering factors were those incorporated in
SHELXS-97.
58,79,80
Ack n ow led gm en t. Financial support from the State
Committee for Scientific Research KBN of Poland
(Grant No. 4 T09A 147 22) and the Foundation for
Polish Science is kindly acknowledged. The quantum
calculations have been carried out at the Pozna n´ Su-
percomputer Center (Pozna n´ ) and Wrocław Supercom-
puter Center (Wrocław).
Ca lcu la tion Meth od . The calculations were carried out
7
5
with the GAUSSIAN98 program. All structures were opti-
mized within X-ray geometry of the system using the density
functional theory (DFT) with Becke’s three-parameter ex-
change functionals and the gradient-corrected functionals of
5
8,76-78
Lee, Yang, and Parr (DFT (B3LYP)).
The final estima-
tions of the total energies were performed at the B3LYP level
with the 6-31G** basis set using the B3LYP/6-31G* fully
optimized structures.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data, bond lengths and angles, anisotropic thermal param-
eters, computational results (Cartesian and computational
results (Cartesian coordinates, four tables); additional coor-
dinates, four tables), and additional NMR are included. This
material is available free of charge via the Internet at
http://pubs.acs.org.
X-r a y Da ta Collection a n d Refin em en t. Crystals of 3
and 6 were prepared by diffusion of hexane into the dichlo-
(75) Frisch, M. J .; Trucks, G. W.; Schlegel, H. B.; Gill, P. M. W.;
J ohnson, B. G.; Robb, M. A.; Cheeseman, J . R.; Keith, T.; Petersson,
G. A.; Montgomery, J . A.; Raghavachari, K.; Al-Laham, M. A.;
Zakrzewski, V. G.; Ortiz, J . V.; Foresman, J . B.; Cioslowski, J .;
Stefanov, B. B.; Nanayakkara, A.; Challacombe, M.; Peng, C. Y.; Ayala,
P. Y.; Chen, W.; Wong, M. W.; Andres, J . L.; Replogle, E. S.; Gomperts,
R.; Martin, R. L.; Fox, D. J .; Binkley, J . S.; Defrees, D. J .; Baker, J .;
Stewart, J . P.; Head-Gordon, M.; Gonzales, C.; Pople, J . A. Gaussian,
Inc., Pittsburgh, PA, 1995.
J O025773F
(79) SHELXS-97: Sheldrick, G.M. University of G o¨ ttingen, Ger-
(
(
(
76) Becke, A. D. Phys. Rev. A 1988, 38, 3098.
77) Lee, C.; Yang, W.; Parr, R. G. Phys. Rev. B 1988, 37, 785.
78) J ohnson, B. G.; Pople, J . A. J . Chem. Phys. 1993, 98, 5612.
many, 1997.
(80) SHELXL-97: Sheldrick, G. M. University of G o¨ ttingen, Ger-
many, 1997.
J . Org. Chem, Vol. 67, No. 16, 2002 5653