Inverted meso-aryl porphyrins with heteroatoms; characterization of thia, selena, and oxa N-confused porphyrins

Article abstract of DOI:10.1021/jo001209y

Synthesis and characterization of inverted porphyrins containing S, Se, and O are reported. A simple 3 + 1 MacDonald-type condensation using modified tripyrrane containing the N-confused ring and diols afforded various N-confused porphyrins 6a-f in 19-30% yield. The single-crystal X-ray structure of 6b shows a ruffled conformation with tilt angles of 21.11° and 31.23° for the N-confused ring and the adjacent pyrrole ring III, respectively, revealing its severe nonplanarity. Significant changes in C_α-_Cβ, C_β-C_β, and C_α-X bond lengths are observed in 6b relative to free thiophene and pyrrole, suggesting the altered delocalization pathway in the modified N-confused porphyrins. The two molecules in the unit cell show a cyclophane-type noncovalent dimer with a face to face orientation of two N-confused pyrrole rings as a result of the presence of weak N-H···N and C-H···N intermolecular hydrogen bonds involving pyrrole-NH, the N atom of the N-confused ring, and the C atom of the pyrrole ring. A detailed ¹H and ¹³C NMR study by 1D and 2D methods allowed assignments of all the peaks in the free base and protonated forms. NMR studies reveal the presence of three different tautomeric forms in solution for 6c in CDCl₃ at low temperature. UV-visible studies reveal absorption band shifts upon heteroatom substitution, and the magnitudes of these shifts are dependent on the nature of the heteroatom. In all cases both monoprotonated and diprotonated species have been identified, and on addition of acid, the first proton goes to the outer N2 atom of the N-confused ring.

Full text of DOI:10.1021/jo001209y

J . Org. Chem. 2001, 66, 153-161
153
In ver ted m eso-Ar yl P or p h yr in s w ith Heter oa tom s;
Ch a r a cter iza tion of Th ia , Selen a , a n d Oxa N-Con fu sed P or p h yr in s†
Simi K. Pushpan,‡ Alagar Srinivasan,‡ Venkataramana Rao G. Anand,‡
Tavarekere K. Chandrashekar,*,‡ Arunachalam Subramanian,§ Raja Roy,§
Ken-ichi Sugiura,| and Yoshiteru Sakata|
Department of Chemistry, Indian Institute of Technology, Kanpur-208-016, India, NMR Division,
Central Drug Research Institute, Lucknow, India, and Institute of Scientific and Industrial Research,
Osaka University, Osaka 567, J apan.
tkc@iitk.ac.in
Received August 7, 2000
Synthesis and characterization of inverted porphyrins containing S, Se, and O are reported. A simple
3 + 1 MacDonald-type condensation using modified tripyrrane containing the N-confused ring and
diols afforded various N-confused porphyrins 6a -f in 19-30% yield. The single-crystal X-ray
structure of 6b shows a ruffled conformation with tilt angles of 21.11° and 31.23° for the N-confused
ring and the adjacent pyrrole ring III, respectively, revealing its severe nonplanarity. Significant
changes in CR-Câ, Câ-Câ, and CR-X bond lengths are observed in 6b relative to free thiophene
and pyrrole, suggesting the altered delocalization pathway in the modified N-confused porphyrins.
The two molecules in the unit cell show a cyclophane-type noncovalent dimer with a face to face
orientation of two N-confused pyrrole rings as a result of the presence of weak N-H‚‚‚N and C-H‚
‚‚N intermolecular hydrogen bonds involving pyrrole-NH, the N atom of the N-confused ring, and
1
the C atom of the pyrrole ring. A detailed H and 13C NMR study by 1D and 2D methods allowed
assignments of all the peaks in the free base and protonated forms. NMR studies reveal the presence
of three different tautomeric forms in solution for 6c in CDCl3 at low temperature. UV-visible
studies reveal absorption band shifts upon heteroatom substitution, and the magnitudes of these
shifts are dependent on the nature of the heteroatom. In all cases both monoprotonated and
diprotonated species have been identified, and on addition of acid, the first proton goes to the outer
N2 atom of the N-confused ring
Ch a r t 1. Molecu la r Str u ctu r es of N-Con fu sed ,
Dou bly N-Con fu sed , a n d N-F u sed P or p h yr in s
In tr od u ction
The successful synthesis of N-confused porphyrin 1a
in 1994 independently by two groups across the globe has
generated a lot of curiosity for the possible existence of
new porphyrin isomers with unique properties.1,2 More
recently Furuta and co-workers have succeeded in syn-
thesizing “doubly N-confused porphyrins”3 1b and “N-
fused porphyrin”4 1c by appropriate synthetic modifica-
tions (Chart 1). Many research groups have recently
exploited some of the unique properties exhibited by the
N-confused porphyrins. Their remarkable ability to act
as tetra coordinate ligands to form transition metal
complexes involving a metal-carbon bond inside the
porphyrin cavity has resulted in the formation of divalent
simple and organometallic Ni(II) complexes,1,5-6 trivalent
Cu(III),3 and Ag(III)3,7 complexes with metal-carbon
bonds. The surprising ease of formation of the metal-
carbon bond is attributed to the presence of an Arduengo-
type aromatic carbene-like structure.8 The possible sta-
bilization of higher oxidation states of metals by doubly
N-confused porphyrin has been discussed recently by
Furuta et al.3
Core modification of N-confused porphyrin by replacing
one or two pyrrole nitrogens by other heteroatoms such
as O, S, and Se results in the formation of modified
N-confused porphyrins with altered electronic structure.9
The interest in such molecules lies in the fact that they
form unusual metal complexes involving weak metal-
heteroatom interactions leading to the isolation of some
† Dedicated to Professor Samaresh Mitra on the occasion of his 60th
birthday.
* Fax: 91(512) 597436/590260/590007.
‡ Indian Institute of Technology.
§ Central Drug Research Institute.
| Osaka University.
(1) Chemielewski, P. J .; Latos-Grazynski, L.; Rachlewicz, K.; Glow-
iak, T. Angew. Chem. 1994, 106, 805; Angew. Chem., Int. Ed. Engl.
1994, 33, 779.
(2) Furuta, H.; Asano, T.; Ogawa, T. J . Am. Chem. Soc. 1994, 116,
767.
(3) Furuta, H.; Maeda, H.; Osuka, A. J . Am. Chem. Soc. 2000, 122,
803.
(4) Furuta, H.; Ishizuka, T.; Osuka, A.; Ogawa, T. J . Am. Chem.
Soc. 1999, 121, 2045.
(5) Szterenberg, L.; Latos-Grazynski, L. Inorg. Chem. 1997, 36, 6287.
(6) Chemielewski, P. J .; Latos-Grazynski, L.; Glowiak, T. J . Am.
Chem. Soc. 1996, 118, 5690.
(7) Furuta, H.; Ogawa, T.; Uwatoko, Y.; Araki, K. Inorg. Chem. 1999,
38, 2676.
(8) Ghosh, A. Angew. Chem. 1995, 107, 1117; Angew. Chem., Int.
Ed. Engl. 1995, 34, 1028.
10.1021/jo001209y CCC: $20.00 © 2001 American Chemical Society
Published on Web 12/06/2000

154 J . Org. Chem., Vol. 66, No. 1, 2001
Pushpan et al.
unusual complexes. Latos-Grazynski and co-workers5,6,10
have recently isolated paramagnetic organometallic com-
plexes of Ni(II) with an axially σ-coordinated phenyl ring
using a monothiaporphyrin, a reactive Ni(II) complex
having a Ni(II)-carbon equatorial bond using 21-carba
porphyrin and two rare paramagnetic Ni(II) species using
a methylated 21-carba porphyrin.
Resu lts a n d Discu ssion
Syn th eses. Most of the synthetic methods available
in the literature for the synthesis of N-confused porphy-
rins are based on original Rothemund reaction of benz-
aldehyde and pyrrole under Lewis acid catalysis.13 For
example, both Latos-Grazynski and co-workers1 and
Furuta and co-workers,2 who independently reported the
first synthesis of N-confused porphyrin, made use of the
reaction of benzaldehyde and pyrrole under different
conditions. Latos-Grazysnki and co-workers used CH2-
Cl2/BF3‚OEt2 while Furuta made use of t-BuOH/CH2Cl2
(1:1) in the presence of 1 equiv of concentrated HBr. Later
Dolphin and co-workers14 came up with a rational
synthesis by a 2 + 2 MacDonald-type condensation using
R,R-dipyrromethane dialdehyde and R,â-dipyrromethane
in an overall yield of 7%. Very recently, Lindsey and co-
workers15 studied the aldehyde-pyrrole reaction under
a variety of conditions and concluded that use of BF3‚
OEt2 as catalyst produced more of N-confused porphyrin,
while use of TFA as the catalyst gave more of ring
expanded sapphyrin. Lash and co-workers also reported
the synthesis of hexa- and heptaalkyl substituted in-
verted porphyrins by a 3 + 1 condensation of pyrrole-
2,4-dicarboxaldehydes and tripyrrane dicarboxylic acid
in 1% TFA/CH2Cl2 followed by oxidation with 0.1%
FeCl3.16 Chang-Hee Lee and co-workers11 were the first
to report the synthesis of core-modified N-confused
porphyrin by a 3 + 1 MacDonald approach using modified
tripyrranes and 2,4-bis(R-hydroxyl methyl) substituted
pyrrole. By this methodology, they were able to isolate
both core-modified porphyrin and core-modified N-con-
fused porphyrin in 3% and 8% yield, respectively. Very
recently, Latos-Grazynski and co-workers11d reported the
synthesis of 2-thia-5,10,15,20-tetraphenyl-21-carbapor-
phyrin (SCTPPH) with an inverted thiophene ring in 4%
yield by 3 + 1 condensation of appropriate precursors.
This compound on oxidation with DDQ or with excess
chloranil gave 2-thia-3-oxo-5,10,15,20-tetraphenyl-21-
carbaporphyrin (SCOTPPH2).
In the present method, we have also followed a similar
3 + 1 approach. However, we have incorporated the
N-confused pyrrole ring as a part of tripyrrane unit and
used core-modified diols using p-toluene sulfonic acid (p-
TsOH) as catalyst in dichloromethane followed by oxida-
tion with chloranil (Scheme 1). Thus 2 on reduction with
LAH in THF at 0 °C gave 3, which on treatment with
pyrrole and TFA gave the key precursor 4; 4 was further
reacted with different diols 5a -d in dichloromethane
using 0.1 equiv of p-TsOH as the catalyst followed by
oxidation with chloranil to afford the desired N-confused
porphyrins 6a -f. It is pertinent to point out here that
the concentration of p-TsOH is crucial for the high yields
of N-confused porphyrin. Use of 0.1 equiv gave maximum
yield and higher concentrations of p-TsOH resulted in
the formation of normal core-modified porphyrin. The
obvious advantages of this method lies in the following
two observations: (a) exclusive formation of the desired
A perusal of literature revealed that there are only few
preliminary reports on the synthesis of core-modified
N-confused porphyrins in about 5-8% yield.11 Easy and
efficient synthetic methods are needed to prepare them
in high yields to further exploit their unique chemistry.
We have been interested in the core modification of
porphyrins and expanded porphyrins and have developed
efficient methods to synthesize them in multigram
quantities.12 In this paper we wish to report a high yield
synthesis of core-modified N-confused porphyrins con-
taining heteroatoms S, Se, and O by a 3 + 1 MacDonald-
type condensation using appropriate precursors. In ad-
dition to synthesis, a detailed characterization of the
modified porphyrins has been done using 1H and 2D
NMR methods, UV-visible and single-crystal X-ray
structure determination. Presence of different tautomers
in solution as revealed by NMR spectroscopy, adaptation
of ruffled conformation in solid state and formation of a
cyclophane-like dimer held by weak N-H‚‚‚N inter-
molecular hydrogen bonds between the pyrrole NH of one
porphyrin and the nitrogen of N-confused pyrrole ring
of other porphyrin in packing diagram are some of the
highlights of the present work.
(9) (a) Berlin, K.; Breitmaier, E. Angew. Chem. 1994, 106, 229;
Angew. Chem., Int. Ed. Engl. 1994, 33, 219. (b) Berlin, K.; Breitmaier,
E. Angew. Chem. 1994, 106, 1356; Angew. Chem., Int. Ed. Engl. 1994,
33, 1246. (c) Berlin, K.; Steinbeck, C.; Breitmaier, E. Synthesis 1996,
336. (d) Lash, T. D. Angew. Chem. 1995, 107, 2703; Angew. Chem.,
Int. Ed. Engl. 1995, 34, 2533. (e) Lash, T. D.; Chaney, S. T. Tetrahedron
Lett. 1996, 37, 8825. (f) Lash, T. D.; Chaney S. T. Angew. Chem. 1997,
109, 867; Angew. Chem., Int. Ed. Engl. 1997, 36, 840. (g) Lash, T. D.;
Chaney, S. T. Angew. Chem. 1996, 108, 1955; Angew. Chem., Int. Ed.
Engl. 1996, 35, 1820. (h) Hayes, M. J .; Lash, T. D. Chem. Eur. J . 1998,
4, 508. (i) Lash, T. D.; Chaney, S. T. Angew. Chem. 1997, 109, 867;
Angew. Chem., Int. Ed. Engl. 1997, 36, 839. (j) Ravikanth, M.;
Chandrashekar T. K. In Structure and Bonding; Clarke, M. D.,
Goodenough, J . B., Ibers, J . A., J orgensen, C. K., Pmingos, D. M.,
Neilands, J . B., Palmer, G. A., Sadler, P. J ., Weiss, R., Williams, R. J .
P., Eds.; Springer-Verlag: Berlin, Heidelberg, 1995; Vol. 82; p 105.
(k) Kumar, M. R.; Chandrashekar, T. K. J . Inclusion Phenom.
Macrocycl. Chem. 1999, 35, 553. (l) Latos-Grazynski, L.; Lisowski, J .;
Olmstead, M. M.; Balch, A. L. J . Am. Chem. Soc. 1987, 109, 4428 and
references therein. (m) Sessler, J . L.; Weghorn, S. J . In Expanded,
Contracted and Isomeric Porphyrins; Elsevier Science: Oxford, 1997.
(10) Latos-Grazynski, L.; Chemielewski, P. J . New J . Chem. 1997,
21, 691 and references therein.
(11) (a) Heo, P.-Y.; Shin, K.; Lee, C.-H. Tetrahedron Lett. 1996, 37,
197. (b) Lee, C.-H.; Kim, H.-J . Tetrahedron Lett. 1997, 38, 3935. (c)
Lee, C.-H.; Kim, H.-J .; Yoon, D.-W. Bull. Korean Chem. Soc. 1999, 20,
276. (d) Sprutta, N.; Latos-Grazynski, L. Tetrahedron Lett. 1999, 40,
8457. (e) Heo, P.-Y.; Shin, K.; Lee, C.-H. Tetrahedron Lett. 1996, 37,
1521.
(12) (a) Srinivasan, A.; Mahajan, S.; Pushpan, S. K.; Kumar, M. R.;
Chandrashekar, T. K. Tetrahedron Lett. 1998, 39, 1961. (b) Narayanan,
S. J .; Sridevi, B.; Chandrashekar, T. K.; Vij, A.; Roy, R. Angew. Chem.
1998, 110, 3582; Angew. Chem., Int. Ed. Engl. 1998, 37, 3394. (c)
Srinivasan, A.; Anand, V. G.; Narayanan, S. J .; Pushpan, S. K.; Kumar,
M. R.; Chandrashekar, T. K. J . Org. Chem. 1999, 64, 8693. (d)
Pushpan, S. K.; Narayanan, S. J .; Srinivasan, A.; Chandrashekar, T.
K.; Roy, R. Tetrahedron Lett. 1998, 39, 9249. (e) Sridevi, B.; Narayanan,
S. J .; Srinivasan, A.; Reddy, M. V.; Chandrashekar, T. K. J . Porphyrins
Phthalocyanines 1998, 2, 69. (f) Srinivasan, A.; Pushpan, S. K.; Kumar,
M. R.; Mahajan, S.; Chandrashekar, T. K.; Roy, R.; Ramamurthy, P.
J . Chem. Soc., Perkin Trans. 2 1998, 969. (g) Narayanan, S. J .; Sridevi,
B.; Chandrashekar, T. K.; Vij, A.; Roy, R. J . Am. Chem. Soc. 1999,
121, 9053. (h) Srinivasan, A.; Reddy, M. V.; Narayanan, S. J .; Sridevi,
B.; Pushpan, S. K.; Kumar, M. R.; Chandrashekar, T. K. Angew. Chem.
1997, 109, 2710; Angew. Chem., Int. Ed. Engl. 1997, 36, 2598. (i)
Srinivasan, A.; Pushpan, S. K.; Kumar, M. R.; Chandrashekar, T. K.;
Roy, R. Tetrahedron 1999, 55, 6671.
(13) (a) Rothemund, P. J . Am. Chem. Soc. 1936, 58, 625. (b)
Rothemund, P. J . Am. Chem. Soc. 1939, 61, 2912.
(14) Liu, B. Y.; Bruckner, C.; Dolphin, D. Chem. Commun. 1996,
2141.
(15) (a) Geier, G. R., III; Lindsey, J . S. J . Org. Chem. 1999, 64, 1596.
(b) Geier, G. R., III; Haynes, D. M.; Lindsey, J . S. Org. Lett. 1999, 1,
1455.
(16) Lash, T. D.; Richter, T. D.; Shiner, C. M. J . Org. Chem. 1999,
64, 7973.

Thia, Selena, and Oxa N-Confused Porphyrins
J . Org. Chem., Vol. 66, No. 1, 2001 155
Sch em e 1. Syn th esis of Cor e-Mod ified
N-Con fu sed P or p h yr in s
related with the free base form of 6c at 298 K, as only
specific shifts of resonances of the core ring protons and
phenyl protons were observed on protonation. Figure 1
1
gives a comparison of H NMR spectra of 6c in its free
base and protonated forms at 298 K and low tempera-
1
tures. The detailed H and 13C peak assignments were
carried out by combined use of homonuclear, hetero-
nuclear one-bond and long-range correlation.17 The num-
bering of the compound along with the correlation
observed is as shown in Figure 2.
The 1H NMR spectrum (at 298 K) of the protonated
6c showed a singlet at -1.76 ppm, a broad resonance at
1.86 ppm (obtained at 243 K), a doublet at 2.64 ppm and
a singlet at 4.03 ppm. In the aromatic region, a doublet
at 7.35 ppm and multiplet between 7.73 and 8.21 ppm,
two well-separated doublets at 8.42 and 8.51 ppm, and a
strongly coupled spin system at 8.95 ppm were observed.
The specific assignments of these protons were based on
1H-1H COSY recorded for 6c in its freebase and proto-
nated forms. The outer 3-CH proton of the N-confused
pyrrole ring was assigned to the peak at 8.21 ppm since
it showed a cross-peak in the COSY spectrum with 2-NH
proton at 12.58 ppm. The peak at -1.76 ppm was
assigned to inner 21-CH proton. This was further con-
firmed by the presence of cross-peak between 2-NH
proton at 12.58 ppm and the 21-CH at -1.76 ppm.
Regarding the assignments of the other two-pyrrole units
and its differentiation with the thiophene spin system,
a combination of homonuclear, heteronuclear one-bond
and long-range correlations were employed. On the basis
of the homonuclear J -correlation experiment done at 243
K, the broad signal at 1.86 ppm gave cross-peaks with
the two doublets at 8.42 and 8.51 ppm, confirming both
the NH's at 1.86 ppm and the two CH protons of the
pyrrole units I and III, respectively. Hence the strongly
coupled spin system centered at 8.95 ppm was ascribed
to both the CH protons of the thiophene ring. The two
pyrrole units showed a typical COSY pattern and they
had one set of protons centered at 8.17 and 8.19 ppm and
the other at 8.42 and 8.51 ppm, respectively. The dif-
ferentiation of the pyrrole units was done based on the
HMBC and HMQC data. The outer 3-CH proton of
N-confused pyrrole at 8.21 ppm showed a long-range
correlation at 152.97 ppm, which further matched the
long-range correlation by the CH proton of the pyrrole
resonating at 8.51 ppm, thus differentiating the remain-
ing two pyrrole units. Similarly, CH proton of the other
pyrrole unit at 8.17 ppm gave a long-range correlation
with CH carbon at 132.66 ppm as well as to the
quaternary carbon at 152.97 ppm. The chemical shift of
the quaternary carbon at 152.97 ppm also showed long-
range correlation with the thiophene CH proton, confirm-
ing once again the assignments of both the pyrrole
protons. This quaternary carbon was identified to be C-15
and hence the protons of the pyrrole unit I were con-
firmed to be the ones that resonate at 8.17 and 8.42 ppm
(attached to C-17 and C-18, respectively). Subsequently,
all the other quaternary carbons were assigned on the
basis of similar such analyses. Further assignments of
the phenyls, methyl, methoxy, and quaternary carbons
were then straightforward.
core-modified N-confused porphyrin with only a trace
amount of normal porphyrin, making the separation on
column very easy and (b) formation of the desired
products in high yields; for example 6a -c were isolated
in 28-32%, 6d in 29%, and 6f in 19%. This is in contrast
to 8% and 5.5% yield reported for 6a and 6f, respectively,
by the earlier method.11a,b
NMR Stu d ies. Detailed H and 13C NMR spectra were
recorded for both free base and protonated forms to arrive
1
at the solution structure of the porphyrins 6a -f. As an
1
example most of the H and 13C NMR assignments were
done on 6c in its protonated form at 298 K; observation
1
of all signals with better resolution were seen in the H
The signal due to 24-NH proton was not observed for
the free base form of 6c at 298 K, suggesting a rapid
NMR spectrum and best spectral dispersion was obtained
in 13C NMR. Wherever difficulties in assignments arose,
help was rendered from spectral information obtained at
243 K and 223 K. These assignments were then cor-
(17) Multinuclear NMR; J .Mason, Ed.; Plenum Press: New York,
1987.

156 J . Org. Chem., Vol. 66, No. 1, 2001
Pushpan et al.
F igu r e 1. 1H NMR spectra of 6c: (a) free base and (b) its diprotonated form at room and low temperature in CDCl3.
Ch a r t 2. P ossible Ta u tom er s for 6a -f
presence of multiple sets of peaks for the NH protons to
the existence of different tautomers in equilibrium in
solution. Three different tautomeric structures (Chart 2)
can be envisaged depending on the location of the proton.
In tautomers II and I, the hydrogen is located on the
either of inner pyrrole nitrogens, whereas in III, the
proton is located on the nitrogen of the N-confused ring.
The observation of three sets of peaks at 223 K suggest
the presence of three tautomers I, II, and III in solution
in equilibrium. J ustification for such a interpretation also
comes from the studies of Chang-Hee Lee and co-
workers11c on the thia derivative. On the basis of the
NMR observations, they have also suggested the presence
of three different tautomers in equilibrium. However, the
protonated form does not show this behavior. The exten-
F igu r e 2. The numbering and J and HMBC correlation
sive NMR studies of 6c were then used for the assign-
ments of peaks in compounds 6a , 6b, 6d , and 6f. However
we should mention here that for compounds 6a , 6d , 6e,
and 6f the inner NH signal in its free base form was not
observed up to 223 K, suggesting the presence of rapid
tautomerism even at such low temperature.
The protonated form of 6e behaved slightly different
from others. Figure 3 shows the temperature-dependent
spectra of 6e in its protonated form. It is clear from the
figure that the two inner-22,24-NH signals and outer
2-NH signal were not observed at room temperature,
However at 243 K, two separate signals for 22,24-NH
protons were observed at 3.09 and 2.99 ppm, suggesting
the nonequivalence of these protons. The outer 2-NH
signal is also clearly seen at 243 K at 13.49 ppm. Also it
is seen from the spectrum that the selenophene protons
observed for 6c.
tautomerism where this proton is exchanging sites
between the two pyrrole nitrogens. However on cooling
the sample to 223 K multiple sets of signal were obtained
(Figure 1a, 223 K). This dynamic behavior was further
probed by recording the NOESY spectrum at 223 K,
which revealed the following: (i) The 21-CH signal at
-3.95 ppm gave a NOE correlation to the 24-NH at 1.02
ppm, thus confirming that these two pyrrole units are
not experiencing any major ring flipping. (ii) Interest-
ingly, three sets of paired resonances assigned to 22-NH
on pyrrole ring III observed at -3.54, -3.21, -2.30,
-1.83, 2.18, and 1.90 ppm showed chemical exchange
phenomena among themselves suggesting the presence
of different tautomers in solution. We attribute the

Thia, Selena, and Oxa N-Confused Porphyrins
J . Org. Chem., Vol. 66, No. 1, 2001 157
Ta ble 1. Selected Bon d Dista n ces for 6b a n d Th eir
Com p a r ison w ith F r ee Th iop h en e a n d P yr r ole Un its.
CR-X#
(Å)
CR-Câ
(Å)
Câ-Câ
(Å)
ring
thiophene
pyrrole I
inv pyrrole II
pyrrole III
1.766(3), 1.759(3) 1.436(4), 1.422(4) 1.366(4)
1.336(4), 1.383(3) 1.454(3), 1.460(4) 1.353(4)
1.336(3), 1.416(4) 1.408(4), 1.415(4) 1.390(3)
1.343(4), 1.381(4) 1.439(4), 1.460(4) 1.357(4)
free thiophene 1.714
free pyrrole 1.370
1.370
1.382
1.423
1.417
a dilute solution of TFA, and (iii) the presence of strong
hydrogen bonding interaction between the inner NH of
one molecule and the outer nitrogen of the other molecule
forming a cyclophane-type dimer in the unit cell of the
single-crystal X-ray structure of 6b. However, at lower
temperature the results are in agreement with that of
Chang-Hee Lee and co-workers, where all the three
tautomers are in equilibrium for 6a .
Str u ctu r a l Ch a r a cter iza tion . Further proof for the
proposed structure came from the single-crystal X-ray
structure of 6b, which is shown in Figure 4. In the
structure, the imino hydrogen atom could not be assigned
unequivocally to either of N1 or N3 as a result of rapid
interconversion of NH tautomers during the time re-
quired for the measurements (supported by 1H NMR
data, vide infra). Our analysis suggests a 50% probability
of occupation on each nitrogen.5
The structure (Figure 4) reveals the nonplanarity of
the macrocycle in a ruffled conformation18 where the
meso carbons are found alternatively above and below
the mean plane defined by four meso carbon atoms. The
specific deviations from the planarity are C5, -0.050(1);
C10, 0.055(1); C15, -0.051(1); and C20, -0.051(1) Å. The
deviation of core heteroatoms S, N1, N3, and C13 are
-0.087(2), -0.069(3), -0.016(3), and 0.21(3) Å, respec-
tively, revealing the maximum deviation for the C-13
atom of N-confused ring. The nonplanarity is also clearly
reflected in the dihedral angles of the planes of individual
pyrrole (heterocyclic) rings with respect to the mean
plane defined by four meso carbon atoms. They are
2.82(6)° for the thiophene ring, 21.11(9)° for the N-
confused pyrrole ring, and 15.77(9)° and 31.23(9)° for the
two opposite pyrrole rings. A comparison of these angles
with that of N-confused porphyrin suggest that in the
N-confused porphyrin, the N-confused pyrrole ring shows
maximum deviation (26.9°),2 while in 6b both N-confused
pyrrole ring and one of the adjacent pyrrole ring show
maximum deviation. This can be understood in terms of
the substitution of the large sulfur atom in the place of
nitrogen increasing the repulsion between the inner N-H
and the sulfur atom, as a result of which the pyrrole ring
is forced to be tilted away from the mean plane.11b
Table 1 lists the relevant bond distances of heterocyclic
rings in the macrocycle 6b and in the free thiophene and
pyrrole rings. Substitution of pyrrole NH by thiophene
sulfur changes the π-delocalization, and the bond dis-
tances are altered accordingly. For example, there is a
significant increase (0.058 Å) in the CR-S distance while
Câ-Câ distance experience a significant decrease (0.057
Å) in 6b relative to the free thiophene revealing that the
π-delocalization through the thiophene ring is altered in
6b. Furthermore, comparison of CR-S, CR-Câ, and Câ-
Câ distances of 6b with that of the 5,10,15,20-tetraphenyl-
F igu r e 3. Temperature-dependent 1H NMR spectra of the
diprotonated form of 6e in CDCl3.
are strongly coupled resulting in the appearance of two
overlapping doublets at 8.95 ppm. From the COSY
spectrum, it was observed that the inner 21-CH is
strongly coupled to outer 3-CH of the confused pyrrole
ring as observed in the case of normal N-confused
porphyrin.1
NH Ta u tom er ism in F r ee Ba se N-Con fu sed P or -
p h yr in s. Chang-Hee Lee and co-workers,11c who reported
the first synthesis of 6a and 6f, have shown the existence
of different tautomers forms for 6a and 6f. Specifically,
6f exhibit only one stable tautomer where the inner
proton is present on the inner pyrrole nitrogen as in I
(Chart 2). However, the thia derivatives 6a exist as two
tautomers at room temperature, the major tautomer
where the proton is located on the outer nitrogen of the
N-confused ring as in III and a minor tautomer where
the proton is on the inner pyrrole nitrogen as in I.
Further, at 223 K, a third tautomer was identified where
the proton is on the other inner pyrrole nitrogen as in II
and the ratio of the three tautomers was found to be 1:1:
10.5/III:I:II.
In the present study, the detailed proton NMR analysis
of the free base derivatives and the protonated deriva-
tives support the conclusions of Chang-Hee Lee, for the
oxa derivative 6f where there is only one dominant
tautomer as in I. However, for the thia derivative 6a ,
results support that the major tautomer is the one in
which the proton is located on the inner pyrrole nitrogen
as in I rather than in III. Strong support for such a
conclusion is based on the following observations: (i) the
inner NH signals are seen in the shielded region, (ii) the
outer NH signal is seen in the region 12-13 ppm at room
temperature only on careful titration of free bases with
(18) Scheidt, W. R., Lee Y. J . In Structure and Bonding; Buchler, J .
W., Ed.; Springer-Verlag: Berlin, Heidelberg, 1987; Vol.64, p 1.

158 J . Org. Chem., Vol. 66, No. 1, 2001
Pushpan et al.
F igu r e 4. ORTEP diagram of 6b: (a) plane view and (b) side view. Phenyl rings are omitted for clarity in side view.
21-thiaporphyrin (1.748(4), 1.408(6), and 1.367(7) Å,
respectively)19 indicate significant increases for CR-S and
CR-Câ distances in 6b, suggesting that the presence of
N-confused ring further alters the delocalization path-
way. The differences in the two types of pyrrole rings (N-
confused and normal) are also reflected in the bond
distances; the CR-Câ and Câ-Câ distances of the N-
confused ring are significantly lower and higher respec-
tively relative to normal pyrrole ring again suggesting
the modified electron delocalization pathway. The aro-
matic nature of 6b is evident from the observation that
CR-Câ distances are higher than the Câ-Câ distances.20
Because of the bigger sulfur atom the core size of 6b is
restricted and this is reflected in the nonbonded dis-
tances: S-Câ ) 3.452 Å and N1-N3 ) 4.599 Å and these
distances compare well with those observed for 5,10,15,-
20-tetraphenyl-21-thiaporphyrin (S-N2 ) 3.546 (8) Å,
N1-N3 ) 4.40(1) Å).19
A close look at the packing diagram (Figure 5) reveals
another interesting aspect of the structure. There are two
molecules in the unit cell and these molecules are linked
to each other through a noncovalent weak N-H‚‚‚N and
C-H‚‚‚N intermolecular hydrogen bonds involving the
pyrrole-NH, the N atom of the N-confused ring and C
atom of pyrrole ring. Four such interactions produce a
cyclophane-like dimeric structure where the two
N-confused rings are almost one above the other. The
N-H‚‚‚N distance of 3.14 (4) Å, bond angle 117.2° and
C-H‚‚‚N distance of 3.24 Å, bond angle 128.25° are in
the range expected for N-H‚‚‚N and C-H‚‚‚N hydrogen
bonds reported in the literature.21 Also, there are two
intramolecular N-H‚‚‚S hydrogen bonds and one
C-H‚‚‚S hydrogen bond in each molecule between pyrrole
N1-H, N3-H, pyrrole C-13, and thiophene sulfur with an
average distance of 2.74 and 3.45 Å for N-H‚‚‚S and
C-H‚‚‚S hydrogen bonds, respectively.
UV-Visible Stu d ies. All the modified porphyrins
6a -f in their free base form exhibit split Soret band in
the region 425-450 nm and Q-bands in the region 500-
750 nm. UV-visible data are tabulated in Table 2. The
effect of heteroatom substitution is seen in the red shift
of absorption bands relative to NCTPP1,2 and the mag-
nitudes of the shifts are dependent on the nature of the
heteroatom. The presence of split Soret reveals lower
symmetry in N-confused porphyrins relative to the parent
meso-tetraphenyl porphyrin (H2TPP). Stepwise protona-
tion results in the further red shifts of Soret and Q-bands,
which is typical of meso-aryl porphyrins.22 However the
magnitude of shifts of Q-bands are much larger (for
example, Q-1 band shifts fall in the range of 80-140 nm)
for the N-confused porphyrins relative to [H4TPP]2+ (the
Q-1 band shifts only 12 nm upon protonation of H2TPP),23
(21) (a) J effrey, G. A.; Saenger, W. In Hydrogen Bonding in
Biological Structure; Springer-Verlag: Berlin, 1994; p 29. (b) Desiraju,
G. R. Angew. Chem. 1995, 107, 2541; Angew. Chem., Int. Ed. Engl.
1995, 34, 2311.
(19) Latos-Grazynski, L.; Lisowski, J .; Szterenberg, L.; Olmstead,
M. M.; Balch, A. L. J . Org. Chem. 1991, 56, 4043.
(20) Sessler, J . L.; Morishima, T.; Lynch, V. Angew. Chem. 1991,
103, 1018; Angew. Chem., Int. Ed. Engl. 1991, 30, 977.
(22) Gouterman, M. In The Porphyrins; Dolphin, D., Ed.; Academic
Press: New York, 1978; Vol. III, p 1.

Thia, Selena, and Oxa N-Confused Porphyrins
J . Org. Chem., Vol. 66, No. 1, 2001 159
F igu r e 5. Packing diagram of 6b showing interactions between the two molecules through intermolecular and intramolecular
hydrogen bonds. The hydrogen bonds are marked with dotted lines.
Ta ble 2. UV-Vis Da ta for N-Con fu sed P or p h yr in s in Th eir F r ee Ba se, Mon o-, a n d Dip r oton a ted Sta te in
Dich lor om eth a n e.
Soret band, λ max
Q-bands, λ max
porphyrin
(nm) (× 10-4) (dm3 cm-1 mol-1
)
(nm) (× 10-3) (dm3 cm-1 mol-1
)
N-CTPP
6a
383(sh), 440(9.68)
431(sh), 446(50.96).
445(42.1), 478(39.17).
471(78.34)
429(sh)(35.72), 446(51.6).
449(40.02), 477(44.97).
472(91.43)
430(sh), 447(36.89)
450(41.65), 477(46.08).
480(51.08)
432(sh), 449(47.21)
440(41.61), 485(54.34).
481(73.84)
506(4.7), 543(7.5), 585(10.9), 672(2.8), 730(9.7).
550(47.73), 586(48.22), 624(57.33), 674(52.11), 729(17.89).
562(74.19), 611(59.31), 687(62.50), 744(84.70).
708(106), 813(111.96).
554(26.670), 591(31.56), 625(44.03), 676(42.43), 733(6.84).
563(47.94), 614(39.56), 740(82.49), 826(37.94).
710(111.19), 816(100.76).
553(28.12), 597(28.0), 630(33.56), 680(31.59), 724(10.31).
562(58.28), 616(48.32), 742(96.76).
741(91.1), 864(80.78).
543(16.36), 579(32.06), 617(55.34), 664(57.01), 742(8.79).
572(53.11), 628(53.05), 745(147.98), 808(61.93).
740(123.42), 836(95.10)
578(47.27), 615(51.18), 664(45.54), 728(18.6).
574(57.92), 670(95.89), 748(59.64).
6a ‚H+
6a ‚2H+
6b
6b‚H+
6b‚H+
6c
6c‚H+
6c‚2H+
6d
6d ‚H+
6d ‚2H+
6e
434(sh), 449(29.0)
441(25.42), 487(26.36).
420(sh), 482(43.11)
428(sh), 440(65.03)
6e‚H+
6e‚2H+
6f
744(109.89), 823(90.63).
476(31.22), 545(10.39), 582(6.78), 651(4.28), 724(4.05).
suggesting a severe distortion from planarity upon pro-
tonation. The observed ruffled structure in the solid state
for the free base also supports such a conclusion. Addition
of first proton to the free base form can either go to inner
N-22 nitrogen or outer N-2 atom to produce a monopro-
tonated species. Careful titration experiments using
Con clu sion s
Syntheses of heteroatom containing N-confused por-
phyrins 6a -f has been achieved in high yields by a 3 +
1 condensation of appropriate precursors using 0.1 equiv
of p-TsOH as the catalyst. Substitution of a heteroatom
into the core of N-confused porphyrins alters the elec-
tronic structure of the ring, and this is reflected in the
altered spectroscopic and structural properties. The X-ray
structure of 6b reported here represents the first single-
crystal structural characterization of a core-modified
N-confused porphyrin. It is hoped that the availability
of multigram quantities of these new core-modified
N-confused porphyrins will allow further exploitation of
their rich chemistry in terms of their coordination
behavior toward transition metals and their use as
catalysts for organic transformations. Studies in this
direction are in progress in this laboratory.
1
dilute TFA solution in the H NMR spectrum results in
the appearance of a peak in the region 12.56-14 ppm
for 6a -f suggesting that site of first proton addition is
outer N-2 atom of the confused pyrrole ring. The second
proton obviously goes to the inner N-22 atom and the
appearance of peaks in the shielded region (1.8-3.1 ppm)
justifies such a conclusion. The protonation shown in
Scheme 2 is essentially same as that observed for the
N-confused porphyrin,1 suggesting that the heteroatom
substitution does not alter the protonation sites.
(23) Ulman, A.; Manassen, J .; Frolow, F.; Rabinovich, D. J . Am.
Chem. Soc. 1975, 97, 6540.

160 J . Org. Chem., Vol. 66, No. 1, 2001
Pushpan et al.
(s, 1H), 7.06-6.78(m, 8H), 6.46(s, 2H), 6.06(s, 1H), 5.97-5.95-
(m, 2H), 5.66(s, 2H), 5.62(s, 1H) 5.14(s, 1H), 5.01(s, 1H), 2.23(s,
3H), 2.18(s, 3H).
Sch em e 2. Step w ise P r oton a tion of
Cor e-Mod ified N-Con fu sed P or p h yr in s
2-Aza -21-ca r ba -23-th ia -5,10,15,20-tetr a p h en yl P or p h y-
r in 6a . 2,5-Bis(phenyl hydroxy methyl) thiophene 5a (0.3 g,
1.01 mmol) and 5,10-diphenyl-8-aza-16-carba-5,10,15,17-tet-
rahydrotripyrrane 4a (0.38 g, 1.01 mmol) were dissolved in
500 mL of dry dichloromethane and stirred in nitrogen
atmosphere for 10 min. p-Toluene sulfonic acid (p-TsOH) (0.02
g, 0.10 mmol) was added into it and allowed to stir for another
90 min under dark at room temperature. Chloranil was added
and the reaction mixture was opened to air and was refluxed
for 90 min. The reaction mixture was cooled, solvent was
removed by distillation, and the compound was purified by
basic alumina column. Column chromatography yielded traces
of 2-aza-21-carba-5,10,15,20-tetraphenyl porphyrin (NCTPP)
and normal monothia porphyrin (STPPH). The desired product
6a was eluted with ethyl acetate and dichloromethane mixture
(1:44) and shiny bluish green crystals of the compound was
obtained from dichloromethane and n-hexane mixture (0.17
g, 26%), which decomposes above 300 °C. At higher concentra-
tion of p-TsOH, the tripyrrane has undergone acidolysis and
gave only STPPH and traces of NCTPP. MS (electro spray):
m/z (%) 632.3 (100) [M] +. Anal. Calcd for C44H29N3S: C 83.65,
H 4.63, N 6.65. Found: C 83.92, H 4.73, N 6.85. 1H NMR (500
MHz, CD2Cl2, 193K): δ 11.23 (br s, 1H), 8.56 (br s, 3H), 8.26
Exp er im en ta l Section
1
All of the chemicals used for the synthesis were reagent
grade unless otherwise specified. Solvents for spectroscopic
measurements were purified and dried according to the
standard methods.1H and 13C NMR spectra were measured
on a 300 or 500 MHz Bruker spectrometer or 400 MHz J EOL
spectrometer in CDCl3 or CD2Cl2 solution. FAB mass spectra
were obtained from a J EOL SX-120/DA6000, and EIMS was
obtained from J EOL D-300 Spectrometer. The electrospray
mass spectra were recorded on a MICROMASS QUANTRO II
triple quadrupole mass spectrometer; C, H, N analyses were
done on a Heraeus Carlo Erba 1108 elemental analyzer. The
UV-vis spectra were recorded on a Perkin-Elmer Lambda 20
UV-vis spectrophotometer. Crystal measurements were made
on a Rigaku AFC7R diffractometer with graphite monochro-
mated Mo KR radiation and a rotating anode generator, and
the crystal was mounted on a glass fiber. The crystal to
detector distance was 235 mm and all calculations were
performed using teXsan24 crystallographic software package
of the Molecular Structure Corporation.
(br s, 7H), 8.0-7.64 (m, 16H). H NMR (500 MHz,CD2Cl2): δ
at 223K 13.62 (s, 1H), 9.14-9.13(d, 2H, J ) 4.5 Hz), 8.68 (s,
1H), 8.57 (s, 1H), 8.49 (s, 1H), 8.34-8.31(m, 6H), 8.02-7.89
(m, 16H), -1.98(s, 1H).
2-Aza -21-ca r b a -23-t h ia -5,20-d i-p -t olyl-10,15-d ip h en yl
P or p h yr in 6b. 2,5-Bis(phenyl hydroxy methyl) thiophene 5a
(0.40 g, 1.35 mmol) and 4a (0.55 g, 1.35 mmol) were dissolved
in 500 mL of dry dichloromethane in the presence of p-TsOH
(0.03 g, 0.14 mmol) and reacted with chloranil (0.50 g, 2.02
mmol) as explained above. The desired product 6b was eluted
with ethyl acetate and dichloromethane mixture (1:99) and
shiny bluish green crystals of the compound were obtained
from dichloromethane and n-hexane mixture (0.25 g, 28%),
which decomposes above 300 °C. FAB mass m/z (%): 660 (50)
[M]+. Anal. Calcd for C46H33N3S: C 83.73, H 5.04, N 6.36.
Found: C 83.56, H 5.32, N 6.21%. 1H NMR (300 MHz, CD2-
Cl2, 298 K): δ 8.55 (br s, 1H), 8.27 (br s, 1H), 7.92-7.87 (m,
8H), 7.68-7.62 (m, 6H), 7.52-7.50 (d, 2H, J ) 7.5 Hz), 7.47-
7.46 (d, 2H, J ) 7 Hz), 2.61 (s, 6H) and at 193 K four broad
peaks as a result of paired resonance at -3.65, -3.15, -2.35,
-1.85 and a broad singlet which appears at 11.19 ppm. 1H
NMR (500 MHz, CD2Cl2/TFA, 298 K): δ 9.05-9.02 (m, 2H),
8.59-8.58 (d, 1H, J ) 4.5 Hz), 8.49-8.48 (d, 1H, J ) 4.5 Hz),
8.24 (s, 1H), 8.23-8.18 (m, 12H), 7.92-7.88 (m, 4H), 7.85-
7.84 (d, 2H, J ) 7.5 Hz), 7. 81-7.8(d, 2H, J ) 7.5 Hz), 2.74 (s,
3H), 2.7 (s, 3H), -1.36 (s, 1H) and 13.41 (s, 1H) at 203 K.
2-Aza -21-ca r ba -23-th ia -5,20-d i-p-tolyl-10,15-d i-p-m eth -
oxy-p h en yl P or p h yr in 6c. Compound 4b (0.36 g, 8.96 mmol)
and 5-bis(p-methoxy-phenyl hydroxy methyl) thiophene 5c
(0.32 g, 8.96 mmol), p-TsOH (0.02 g, 0.90 mmol), and chloranil-
(0.33 g, 1.34 mmol) under similar reaction conditions as
mentioned above gave lustrous bluish green solid identified
as 6c. This was purified by basic alumina column. The desired
product was eluted with ethyl acetate and dichloromethane
(4:96) mixture and was recrystallized from dichloromethane/
n-hexane mixture (0.20 g, 30%), which decomposes above 300
°C. FAB mass m/z (%): 720 (100) [M] +. Anal. Calcd for
C48H37N3O2S: C 80.08, H 5.18, N 5.84. Found: C 80.22, H 5.41,
Syn th eses. Compound 4a was prepared by the method
11a
reported earlier by Chang-Hee Lee et al.
and 5a -d were
prepared using the methodology reported earlier from this
12e,g
laboratory.
5,10-Ditolyl-8-aza-16-car ba-5,10,15,17-tetr ah ydr otr ipyr -
r a n e 4b. This compound was obtained by the Friedel-Craft
reaction. Pyrrole (3.5 g, 0.05mol) by p-methyl-benzoyl chloride
(18 g, 0.12mol) in the presence anhydrous AlCl3 (15.6 g,
0.12mol) for 72 h under reflux gave 2,4-bis(p-methyl)-benzoyl-
pyrrole (6 g, 44%) 2b. One gram of 2b (3.63 mmol) was then
reduced with LiAlH4 (0.55 g, 0.02 mmol) by stirring it in the
N2 atmosphere for 2 h at 0 °C in dry THF, which gave 2,4-
bis(p-methyl-phenyl hydroxy methyl)-pyrrole 3b, which was
extracted with dichloromethane and dried over sodium sulfate.
The solvent removed at room temperature by vacuum and was
immediately reacted with excess pyrrole in the presence of
trifluoro acetic acid (TFA) (0.06 g, 0.5 mmol). The reaction
mixture was quenched with dichloromethane and neutralized
by treating it with 0.1 N NaOH solution. The organic layer
separated was given a water wash for two times and dried
over sodium sulfate. The excess solvent was removed by
vacuum at room temperature and the compound was purified
by silica gel column.The yellow band moving with ethyl acetate
and petroleum ether (11:89) was the desired product 4b (0.6
g, 41%). EI mass: m/z (%) 405(49.2) [M]+. Anal. Calcd for
1
N 5.67. H NMR (300 MHz, CDCl3, 298 K) ppm: as shown in
Table 1.
2-Aza -21-ca r ba -23-selen a -5,10,15,20-tetr a p h en yl P or -
p h yr in 6d . 2,5-Bis(phenyl hydroxy methyl) selenophene 5c
(0.41 g, 1.20 mmol) and 4a (0.38 g, 1.10 mmol), p-TsOH (0.02
g, 0.11 mmol), and chloranil (0.54 g, 2.19 mmol) under similar
reaction conditions explained above gave bluish green solid
identified as 6d on basic alumina column with ethyl acetate
and dichloromethane (4:41) mixture as eluent. The bluish
green lustrous solid was recrystallized in dichloromethane and
n-hexane mixture (0.20 g, 26%), which decomposes above 300
C
28H27N3: C 82.92, H 6.71, N 10.37. Found: C 82.94, H 6.73,
N 10.43. 1H NMR (400 Hz/CDCl3): δ 7.69-7.67 (m, 2H), 7.48-
(24) teXsan: Crystal Structure Analysis Package, Molecular Struc-
ture Corporation (1985 and 1999)

Thia, Selena, and Oxa N-Confused Porphyrins
J . Org. Chem., Vol. 66, No. 1, 2001 161
°C. MS (electro spray) m/z (%): 680 (70) [M + 1]+. Anal. Calcd
for C44H29N3Se: C 77.87, H 4.31, N 6.19. Found: C 77.17, H
4.21, N 6.36. 1H NMR (500 MHz, CDCl3, 223 K): δ 9.79 (s,
1H), 8.63 (s, 2H), 7.99 (s, 1H), 7.97-7.85 (m, 10H), 7.72-7.61-
(m, 15H).1H NMR (500 MHz, CDCl3/TFA, 223 K): δ 13.23 (s,
1H), 9.05-9.01 (m, 2H), 8.65-8.64 (d, 2H, J ) 4 Hz), 8.54-
8.53 (d, 1H, J ) 4 Hz), 8.46-8.45 (d, 1H, J ) 7 Hz), 8.39-8.35
(m, 2H), 8.31-8.3 (d, 1H, J ) 6 Hz), 8.27 (s, 1H), 8.25-8.24
(d, 1H, J ) 3 Hz), 8.12 (s, 2H), 8.02-7.73 (m, 16H), -1.32(s,
1H).
mmol) and 4b (0.40 g, 1.07 mmol), p-toluene sulfonic acid (0.05
g, 0.27 mmol), and chloranil (0.39 g, 1.61 mmol) under similar
reaction conditions explained above gave bluish green solid
identified as 6f on basic alumina column with ethyl acetate
and dichloromethane (12:88) mixture as eluent. The bluish
green lustrous solid was recrystallized in dichloromethane and
n-hexane mixture (0.13 g, 19%), which decomposes above 300
°C. MS (electro spray) m/z (%): 616.2 (100) [M] +. Anal. Calcd
for C44H29N3O: C 85.83, H 4.75, N 6.82. Found: C 85.63, H
1
4.59, N 6.62. H NMR (500 MHz, CDCl3, 298 K): δ 8.74-8.72
2-Aza -21-c a r b a -23-s e le n a -5,20-d i-p -t o ly l-10,15-d i-
p h en yl P or p h yr in 6e. 2,5-Bis(phenyl hydroxy methyl) sele-
nophene 5c (0.3 g, 0.87 mmol), 4b (0.35 g, 0.87 mmol),
p-toluene sulfonic acid (0.02 g, 0.09 mmol), and chloranil (0.32
g, 1.32 mmol) under similar reaction conditions as above gave
a bluish green solid identified as 6e on basic alumina column
with ethyl acetate and dichloromethane (6:94) mixture as
eluent. The bluish green lustrous solid was recrystallized in
dichloromethane and n-hexane mixture (0.18 g, 29%), which
decomposes above 300 °C. FAB mass m/z (%): 706 (70) [M +
1] +. Anal. Calcd for C46H33N3Se: C 78.17, H 4.7, N 5.94.
(m, 2H), 8.69 (s, 1H), 8.53-8.52 (d, 1H, J ) 4.5 Hz), 8.51-
8.50 (d, 1H, J ) 5 Hz), 8.29-8.28 (d, 1H, J ) 7.5 Hz), 8.27-
8.22 (d, 1H, J ) 7 Hz), 8.12-8.09 (m, 6H), 7.79-7.71 (m, 14H),
-2.55 (s, 1H).
Ack n ow led gm en t. This work was supported by a
grant from the Department of Science and Technology
(DST) and Council of Scientific and Industrial research
(CSIR), Government of India to T.K.C.; S.K.P. wishes
to thank CSIR for the senior research fellowship.
1
Found: C 78.36, H 4.81, N 6.09. H NMR (300 MHz, CDCl3,
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data, structure solution and refinement, atomic coordinates,
bond lengths and angles and thermal parameters for com-
298 K): δ 9.38 (br s, 2H), 8.52 (s, 2H), 7.91-7.83 (m, 8H), 7.80
(s, 1H), 7.70-7.54 (m, 8H), 7.5-7.48 (d, 2H, J ) 8.05 Hz),
7.44-7.41 (d, 2H, J ) 8.05 Hz), 2.6 (s, 3H), 2.58 (s, 3H).
1HNMR (300 MHz, CDCl3/TFA, 298 K): 8.95-8.91 (m, 2H, J
) 5.85 Hz), 8.52-8.51(d, 1H, J ) 4.39 Hz), 8.42-8.41(d, 1H,
J ) 4.39 Hz), 8.32 (s, 1H), 8.241-8.162 (m, 10H), 7.91-7.75
(m, 10H), 2.76 (s, 3H), 2.69 (s, 3H), -0.72 (s, 1H) and at 223K
13.49 (s, 1H), 3.09 (s, 1H), 2.99 (s, 1H).
1
pound 6b, H-1H COSY for free base and diprotonated form,
HMBC and HMQC correlation for diprotonated form at 298
K and NOESY spectrum at 223 K, UV-vis spectrum of
freebase, monoprotonated and diprotonated form of 6c and
NMR chemical shift values. This material is available free of
charge via the Internet at http://pubs.acs.org.
2-Aza -21-ca r ba -23-oxa -5,10,15,20-tetr a p h en yl P or p h y-
r in 6f. 2,5-Bis(phenyl hydroxy methyl) furan 5d (0.3 g, 1.07
J O001209Y