Oxidized forms of a tripyrrane: α-Tripyrrinone, β-tripyrrinone and a C2 symmetric hexapyrrole

Article abstract of DOI:10.1039/b901171b

α- and β-tripyrrinone isomers (3-6), and a C₂ symmetric hexapyrrole (7) were isolated from the oxidation of meso-perfluorophenyl tripyrrane 1 (and meso-2,6-dichlorophenyl tripyrrane 2) with DDQ under aerobic conditions, and the structure of 3 w

Full text of DOI:10.1039/b901171b

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Oxidized forms of a tripyrrane: a-tripyrrinone, b-tripyrrinone
and a C2 symmetric hexapyrrolew
Ji-Young Shin, Steven S. Hepperle, Brian O. Patrick and David Dolphin*
Received (in Austin, TX, USA) 19th January 2009, Accepted 24th February 2009
First published as an Advance Article on the web 25th March 2009
DOI: 10.1039/b901171b
a- and b-tripyrrinone isomers (3–6), and a C2 symmetric
hexapyrrole (7) were isolated from the oxidation of
meso-perfluorophenyl tripyrrane 1 (and meso-2,6-dichlorophenyl
tripyrrane 2) with DDQ under aerobic conditions, and the
structure of 3 was determined by X-ray crystallographic analysis.
(Fig. 1). The interior C–N–C angles on each pyrrole unit
reveal both amino-type (111.41 for C(1)–N(1)–C(4) and
110.71 for C(11)–N(3)–C(14)) and imino-type nitrogen atoms
(105.11 for C(6)–N(2)–C(9)). As a result of the steric hindrance
between the hydrogens on N(1) and N(3), the mean plane of
the tripyrrinone is slightly twisted (the dihedral angle between
the dipyrrolyl plane containing the N(1) and N(2) atoms and
the pyrrole plane containing the N(3) atom is 25.81). Each
amino-H atom forms hydrogen-bonds with an imino-N atom
[bond lengths(A): 2.19; 2.25].
Porphyrins and larger related macrocycles, particularly
expanded porphyrins, have been widely studied since these
molecules have shown unique chemical and physical
properties.1 Included in the continuing efforts to prepare these
macrocycles has been the exploration of improved or new
reaction conditions.2,3 Recently, Osuka et al. reported that
acid-catalyzed conjugation followed by oxidation, under
anaerobic conditions, of a CH2Cl2 solution of a meso-
perfluorophenyl substituted tripyrrane under refluxing conditions
formed a rubyrin and a nonaphyrin (1.1.0.1.1.0.1.1.0).4 Our
recent research on DDQ-oxidation of tripyrranes under
aerobic conditions resulted in the formation of the tripyrrinone
compounds 3–6 and a DDQ adduct,z the tripyrrin dimer 7.
The structure of tripyrrinone 3 was determined by X-ray
crystallography (Fig. 1).y
The 1H NMR spectrum of 3 in CD2Cl2 shows downfield
shifts for the two amino-H peaks resulting from hydrogen-
bonding effects (Fig. 2(a)). Two broad singlets at 11.58 and
10.01 ppm were assigned to the amino-Hs. In comparison to
1
compound 3, the H NMR spectrum of 5 showed two broad
singlets for the amino-H atoms with significantly different
chemical shifts of 12.03 and 8.00 ppm (Fig. 2(b)). This results
from the greater distance between the amino-Hs for this
compound preventing the formation of intramolecular
hydrogen-bonds. Two sets of doublets (a set at 6.85 and
6.35 ppm and the other set at 6.75 and 6.28 ppm, see
Fig. 3(a)) in the spectrum of 3 were assigned to the peaks of
the two pyrrole units having substituted a-positions and the
peaks at 7.51 and 6.43 ppm were assigned as the peaks for the
a and b-Hs on the terminal pyrroles having unsubstituted
a-positions. These sets of peaks are distinguishable from those
of 5 which resonate over a relatively wider range between
When tripyrrane 1 was briefly oxidized by DDQ under
aerobic conditions tripyrranone 3 and its isomer 5 were
formed. The X-ray crystallographic data of 3 describes a
structure having intermolecular N–Hꢀ ꢀ ꢀN hydrogen-bonds
Department of Chemistry, University of British Columbia,
2036 Main Mall, Vancouver, BC, V6T 1Z1, Canada.
E-mail: david.dolphin@ubc.ca; Fax: +1 604 822 9678;
Tel: +1 604 822 4571
w Electronic supplementary information (ESI) available: Experimental
and spectral data for compounds 3 and 7, crystallographic data for
compound 3 and the structural proof for compounds 3 (CIF) and 7.
CCDC 693823. For ESI and crystallographic data in CIF or other
electronic format see DOI: 10.1039/b901171b
Fig. 1 Crystal structure of 3; the dashed line indicates the intra-
molecular hydrogen-bonds: (a) top view and (b) side view. Thermal
ellipsoids are scaled to the 50% probability level.
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Fig. 5 1H NMR spectra of 7 in CD2Cl2; (a) before and (b) after
adding D2O.
as far as 37.51, 2y (Mo radiation). Although the data were
weak an initial structure was obtained and isotropic refinements
could be carried out. Subsequent anisotropic refinements were,
predictably, unreliable, resulting in unreasonable geometries
and anisotropic displacement parameters. The isotropic
model is, however, sufficient to unambiguously determine the
three-dimensional connectivity of the compound (see ESIw). A
related structure, having similar connectivity to DDQ, has
recently been obtained from the oxidation of a simple
dipyrromethane.5 The optical spectral data suggested that 7
contained an extended p-conjugated chromophore and the
1H NMR requires a symmetrical configuration.
Fig. 2 1H NMR spectra of 3 (a) and 5 (b) in CD2Cl2.
Since the diffraction data only confirmed the configuration
we have carried out Kohn–Sham density functional theory
(DFT) calculations on compound 7. Both the observed and
calculated 1H NMR data show very similar chemical shifts
(ESIw). The 1H NMR spectrum of 7 (Fig. 5) supports the
assigned structure where one set of a-H is absent (from the
original tripyrrane) confirming connection to the DDQ adduct
and showing that compound 7 has a symmetric structure in
solution. Two sets of two doublets for the b-Hs on the inner
pyrroles and one set of three broad peaks for the a- and b-Hs
on the terminal pyrroles appear in the 1H NMR and
HHCOSY spectra (Fig. 5 and Fig. S19, ESIw). Similar to the
observations for 3, the amino-H peaks of 7 are hydrogen-
bonded to the imino-N and the carbonyl-O resulting in
pronounced downfield shifts (12.84 and 12.35 ppm). The
energy minimized structure has C2 symmetry and hydrogen-
bonds as shown in Fig. 6. In CH2Cl2, 7 showed a major
absorption band at 397 nm, which shifted to 423 nm upon
protonation.w A broad absorption band around 700 nm
indicates that the molecule is more extensively conjugated
Fig. 3 HHCOSY spectra of 3 (a) and 5 (b) in CD2Cl2 after adding
D2O.
8.1 and 6.5 ppm, in the absence of hydrogen-bonding
(Fig. 3(b)). The a- and b-Hs on the oxo-pyrrole of 5 were
observed as singlets at 7.35 and 6.39 ppm (red dots in
Fig. 2(b)). As a result of the oxo-group at the b-position direct
coupling between the a-H and the remaining b-H was
not detected in the HHCOSY NMR spectrum (Fig. 3(b)).
Correspondingly, differences in the two isomers can also be
found in the 19F NMR spectra (Fig. 4). The peaks for each set
of o-, m-, and p-F atoms further establish the fact the two
perfluorophenyl rings of 5 have markedly different orientations
from those of 3.
Compound 7 was isolated from a similar oxidation reaction
with tripyrrane 2 having 2,6-dichlorophenyl substituents on
the meso-positions. The mass spectrum showed a parent
peak in which two tripyrrines are bound to a dichloro-
dicyano-diquinolate moiety. Single crystal X-ray data were
collected from a sample of the material. The crystal was a
particularly weak diffractor, with recognizable data out only
Fig. 6 Energy minimized structure of compound 7 (B3LYP/6-31G(d,p),
Gaussian6); (a) top view and (b) side view. Hydrogen-bonds are indicated
with dashed lines.
Fig. 4 19F NMR (282.4 MHz) spectra of 3 (a) and 5 (b).
2324 | Chem. Commun., 2009, 2323–2325
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(m, 2H, bH), 6.29 (m, 2H, bH), 6.05 (d, J = 4.4, 2H, bH); 13C NMR
(100 MHz, CD2Cl2) d = 183.02, 163.12, 162.38, 151.55, 143.38,
138.86, 138.57, 136.80, 136.09, 135.94, 134.87, 134.73, 134.16,
134.07, 132.71, 131.53, 131.11, 128.86, 128.57, 127.72, 127.03,
126.09, 124.47, 117.68, 114.82, 83.03; m/z found 1248.1, calc. 1247.9
for C60H32Cl10N8O2 (M+).
y Crystal data for 3: C26H9F10N3Oꢀ1/2CH2Cl2, m = 611.83, mono-
clinic, a = 29.240(1) A, b = 23.151(9) A, c = 7.016(2) A, b =
93.06(1)1, V = 4743(3) A3, T = 173 K, space group C2/c (no. 15), z =
8, l(Mo-Ka) = 2.69 cmꢂ1, 16 039 reflections measured, 8018 unique
which were used in all calculations. The data were corrected for
Lorentz and polarization effects and absorption (multi-scan including
decay and scaling relative correction factors 0.681–0.987). The struc-
ture was solved by direct methods (SIR92). The final refinement
converged at R1 [F, 7238 reflections having I 4 2.00s(I)] = 0.084
and wR2(F2, all 13 171 unique reflections) = 0.246. All refinements
were performed using the SHELXTL crystallographic software pack-
age of Bruker-AXS. This particular structure was twinned, and the
data set used to refine the structure had reflections from both
components. This makes it look as though there are more reflections
than are necessary.
Fig. 7 Observed (a) and calculated (b) optical spectra of compound 7
in CH2Cl2.
than the tripyrrin; the calculated optical spectrum also
supports this extended conjugation. Both the observed and
calculated electronic spectra are congruent (Fig. 7).w
An understanding of the mechanism for the formation of
these compounds remains an important issue and further
research is continuing.
1 (a) The Porphyrins, ed. D. Dolphin, Academic Press, New York,
1978, vol. III–V; (b) Porphyrins and Metalloporphyrins, ed.
K. M. Smith, Elsevier, New York, 1976; (c) Expanded, Contracted
& Isomeric Porphyrins, ed. J. L. Sessler and S. J. Weghorn,
Pergamon, Oxford, 1997; (d) A. Jasat and D. Dolphin, Expanded
Porphyrins and their Heterologs, Chem. Rev., 1997, 97, 2267–2340.
2 (a) D. A. Lee and K. M. Smith, J. Chem. Soc., Perkin Trans. 1, 1997,
1215–1227; (b) D. K. Dogutan, S. H. H. Zaidai, P. Thamyongkit
and J. S. Lindsey, J. Org. Chem., 2007, 72, 7701–7714; (c) W. Jiao
and T. D. Lash, J. Org. Chem., 2003, 68, 3896–3901;
(d) D. T. Richter and T. D. Lash, J. Org. Chem., 2004, 68,
8842–8850.
This work was supported by the Natural Sciences and
Engineering Research Council (NSERC) of Canada.
Notes and references
z Selected data for 3: 23% yield, lmax (CH2Cl2)/nm 339.0, 541.1; 1H
NMR (600 MHz, CD2Cl2) d = 11.58 (br s, 1H, NH), 10.01 (br s, 1H,
NH), 7.51 (s, 1H, aH), 6.85 (d, J = 5.7, 1H, bH), 6.75 (d, J = 4.7, 1H,
aH), 6.43 (s, 1H, bH), 6.42 (d, J = 3.8, 1H, bH), 6.35 (d, J = 5.7, 1H,
bH), 6.28 (d, J = 4.8, 1H, bH); 19F NMR (282.4 MHz, CD2Cl2) d =
3 (a) M. G. P. M. S. Neves, R. M. Martins, A. C. Tome, A. J.
D. Silvestre, A. M. S. Silva, V. Felix, M. G. B. Drew and J. A.
S. Cavaleiro, Chem. Commun., 1999, 385–386; (b) Z. Gross,
N. Galili, L. Simkhovich, I. Saltsman, M. Botoshansky,
ꢂ139.13 (dd, J = 8.6, ddJ = 23.6, 2F, o-F), ꢂ139.61 (dd, J = 6.5, dd
J
= 19.3, 2F, o-F), ꢂ153.07 (t, J = 21.5, 1F, p-F), ꢂ153.25 (t, J = 21.5,
1F, p-F), ꢂ161.88 (m, 4F, m-F); 13C NMR (150.96 MHz, CD2Cl2) d =
171.77, 167.13, 151.14, 144.53, 147–137, 136.76, 135.23, 132.15,
131.95, 129.13, 127.73, 126.62, 124.41, 122.96, 113.98, 112.5–110.5
(the peaks are broadened by the multiple 13C–19F couplings of the
perfluorophenyl rings), 101.71; m/z EIMS found 570.0674, calc.
¨
D. Blaser, R. Boese and I. Goldberg, Org. Lett., 1999, 1, 599–602;
(c) J.-Y. Shin, H. Furuta, K. Yoza, S. Igarashi and A. Osuka, J. Am.
Chem. Soc., 2001, 123, 7190–7191; (d) R. Taniguchi, S. Shimizu,
J.-Y. Shin, H. Furuta and A. Osuka, Tetrahedron Lett., 2003, 44,
2505–2507; (e) Y. Tanaka, J.-Y. Shin and A. Osuka, Eur. J. Org.
Chem., 2008, 1341.
570.0664 for C26H10N3OF10 ([M + H+ +
] ). Selected data for 4: 5%
yield, 1H NMR (400 MHz, CD2Cl2) d = 11.43 (br s, 1H, NH), 9.91
(br, 1H, NH), 7.45 (m, 5H, aryl-H and aH), 7.39 (dt, J = 7.0, dtJ =
9.0, aryl-H), 6.71 (d, J = 5.5, 1H, bH), 6.57 (d, J = 4.3, 1H, bH), 6.37
(dd, J = 3.9, ddJ = 1.6, bH), 6.28 (dd, J = 4.5, ddJ = 1.0, bH), 6.26
(d, J = 5.9, bH), 6.08 (d, J = 4.7, bH); m/z ESIMS found 526.0045,
calc. 526.0047 for C26H16N3OCl4 ([M + H]+). Spectral data for 5:
4 S. Shimizu, R. Taniguchi and A. Osuka, Angew. Chem., Int. Ed.,
2005, 44, 2225–2229.
5 Unpublished results, J.-Y. Shin, B. O. Patrick and D. Dolphin, Org.
Biomol. Chem., submitted.
6 M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, J. A. Montgomery, Jr, T. Vreven,
K. N. Kudin, J. C. Burant, J. M. Millam, S. S. Iyengar, J. Tomasi,
V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega,
G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota,
R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda,
O. Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox,
H. P. Hratchian, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo,
R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi,
C. Pomelli, J. W. Ochterski, P. Y. Ayala, K. Morokuma,
G. A. Voth, P. Salvador, J. J. Dannenberg, V. G. Zakrzewski,
S. Dapprich, A. D. Daniels, M. C. Strain, O. Farkas, D. K. Malick,
A. D. Rabuck, K. Raghavachari, J. B. Foresman, J. V. Ortiz,
Q. Cui, A. G. Baboul, S. Clifford, J. Cioslowski, B. B. Stefanov,
G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. L. Martin,
D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A. Nanayakkara,
M. Challacombe, P. M. W. Gill, B. Johnson, W. Chen,
M. W. Wong, C. Gonzalez and J. A. Pople, GAUSSIAN 03.
(Revision E.01), Gaussian, Inc, Wallingford, CT, 2007.
1
10% yield, H NMR (300 MHz, CD2Cl2) d = 12.03 (br s, 1H, NH),
8.06 (dd, J = 5.8, ddJ = 1.4, 1H, aH), 8.00 (br s, 1H, NH), 7.35 (s, 1H,
aH), 6.74 (d, J = 4.7, 1H, bH), 6.50 (d, J = 4.7, 1H, bH), 6.39 (dd, J
= 6.0, ddJ = 1.7, 1H, bH), 6.37 (m, 1H, bH), 6.36 (s, 1H, bH); 19F
NMR (282.4 MHz, CD2Cl2) d = ꢂ138.40 (d, J = 17.2, 2F, o-F),
ꢂ139.67 (dd, J = 4.1, ddJ = 8.9, 2F, o-F), ꢂ153.24 (t, J = 20.6, 1F, p-
F), ꢂ153.25 (t, J = 21.5, 1F, p-F), ꢂ161.51 (m, 2F, m-F), ꢂ161.98 (m,
2F, m-F); 13C NMR (75.48 MHz, CD2Cl2) d = 171.64, 164.64, 150.01,
144.02, 147–137 (the peaks are broadened by the multiple 13C–19
F
couplings of the perfluorophenyl rings), 137.27, 134.54, 132.88, 132.27,
127.96, 126.14, 122.68, 119.57, 113.96; m/z ESIMS (+ev) found 570.0,
calc. 570.1 for C26H10N3OF10 ([M + H+ +
]
), (ꢂev) found 567.9, calcd.
568.1 for C26H8N3OF10 ([M ꢂ H+]ꢂ). Selected data for 6: o0.5%
yield, m/z ESIMS found 526.0052, calc. 526.0047 for C26H16N3OCl4
([M + H+ +). Selected data for 7: 30% yield, 1H NMR (300 MHz,
]
CD2Cl2) d = 12.84 (br s, 2H, NH), 12.35 (br s, 2H, NH), 7.88 (s, 2H,
aH), 749–7.36 (m, 12H, aryl-H), 6.95 (dd, J = 5.5, ddJ = 1.7, 2H, bH),
6.60 (d, J = 5.5, ddJ = 1.7, 2H, bH), 6.47 (d, J = 4.4, 2H, bH), 6.33
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Chem. Commun., 2009, 2323–2325 | 2325