Aza-bridged bis-1,10-phenanthroline acyclic derivatives: Synthesis, structure, and regioselective alkylation

Article abstract of DOI:10.1016/j.tetlet.2010.05.039

A family of acyclic aza-bridged bis-1,10-phenanthroline compounds has been synthesized in a convenient way. The resulting compounds 2 and 2.HCl were fully characterized and their solid state structures and NMR spectroscopic properties were investigated to assess how the structural units affect the alkylation reactions. The results reveal the transoid structure for 2. The broadening NMR peak in 2 is shown to be due to an unusual intramolecular CH· hydrogen bond. This unique conformation offers an efficient and regioselective method to prepare the amino-substituted bis-2,2′-1,10-phenanthroline derivatives and 1,10-phenanthrolino-N-alkylated compounds.

Full text of DOI:10.1016/j.tetlet.2010.05.039

Tetrahedron Letters 51 (2010) 3743–3747
Contents lists available at ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Aza-bridged bis-1,10-phenanthroline acyclic derivatives: synthesis, structure,
and regioselective alkylation
*
Hsien-Chang Kao, Chia-Jung Hsu, Che-Wei Hsu, Chien-Ho Lin, Wen-Jwu Wang
Tamkang University, Department of Chemistry, Tamsui, Taipei 25137, Taiwan
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 11 January 2010
Revised 7 May 2010
Accepted 11 May 2010
Available online 31 May 2010
A family of acyclic aza-bridged bis-1,10-phenanthroline compounds has been synthesized in a conve-
nient way. The resulting compounds 2 and 2ꢀHCl were fully characterized and their solid state structures
and NMR spectroscopic properties were investigated to assess how the structural units affect the alkyl-
ation reactions. The results reveal the transoid structure for 2. The broadening NMR peak in 2 is shown to
be due to an unusual intramolecular CHꢀ ꢀ ꢀN hydrogen bond. This unique conformation offers an efficient
and regioselective method to prepare the amino-substituted bis-2,20-1,10-phenanthroline derivatives
and 1,10-phenanthrolino-N-alkylated compounds.
Keywords:
2-Chloro-1,10-phenanthroline
Amino-substituted-2,2’-bis-1,10-
phenanthroline
Ó 2010 Elsevier Ltd. All rights reserved.
1,10-Phenanthrolino-N-alkylated
compounds
Polypyridyl has been known to be an important class of versa-
tile ligands for the chelation of metals. Although so, the 1,10-phe-
nanthroline ligand has the advantage that it can form complexes
with metals more rapidly than the 2,20-bipyridine system.
Important properties of transition metal complexes of 1,10-phe-
nanthroline have been extensively investigated because of their
photochemical,1 electrochemical,2 and biological properties.3 Also,
1,10-phenanthroline complexes have been found to interact with
nucleic acid or protein for the expression of biological activities.
The planar and rigid structure of 1,10-phenanthroline can either
intercalate or bind to the grooves of DNA or RNA.4 Much attention
has, therefore, been focused on the design and synthesis of new
derivatives of 1,10-phenanthroline with extended properties but
only few results were reported in the literature.5 We have previ-
ously reported an alternative strategy to synthesize a series of
macrocyclic and acyclic derivatives of 1,10-phenanthroline ligand.6
We now report on the synthesis of an acyclic aza-bridged bis-1,
10-phenanthroline, together with its reaction, structure, and
spectroscopic properties. We demonstrate here that the acyclic
aza-bridgedbis-1,10-phenanthrolinecanbe site-selective alkylated.
The strategy and reaction conditions we used to synthesize the
desired compounds are shown in Scheme 1 and Table 1. Compound
1 was synthesized using previously described procedure.6a It was
found that compound 1 sublimed readily to preclude carrying
out further reaction at high temperature. This problem was over-
come by using the hydrochloric salt, 1ꢀHCl, for the successive reac-
tion. Treatment of pulverized crystal of 1ꢀHCl in an NH3
atmosphere at 240 °C for 6 h was readily shown to give 2ꢀHCl in
excellent yield.7 The one-pot synthetic route provides a convenient
and efficient method for the preparation of the aza-bridged bis-
1,10-phenanthroline acyclic compound. The corresponding neutral
mono-aza-bridged 1,10-phenanthroline 2 (a brown powder) was
readily obtained in quantitative yield8 by neutralizing the 2ꢀHCl
with NH4OH, and followed by Soxhlet extraction with acetone.
Compound 2 shows a strong electronic coupling between the
NH group and the two 1,10-phenanthroline rings. However, this
type of interaction is likely to be weakened in solution, whereby
the lone electron pair of the NH group is sensitive to its environ-
ment and readily interacts with the surrounding protons.5c In solu-
tion, the free rotation of the two 1,10-phenanthroline rings around
the C–N bonds is expected to induce some impact on the electronic
coupling and reactivity, thus resulting in an intramolecular confor-
mational equilibrium between the near planar and twisted confor-
mations in the ground state. In protic solvents, the interaction
between the solvent protons and the lone electron pair of the NH
group tends to favor the twist-conformation, causing the two
1,10-phenanthroline rings to be out of the plane, disrupting the
conjugation.
One of the interesting features of 2 is its existence in the tauto-
meric form. The consequence of proton-shift imine-enamine tau-
tomerism becomes important in systems of fused aromatic and
heterocyclic rings,9 where the fused three-ring system of 1,10-phe-
nanthroline makes such a process somewhat favorable.5c,6a. From
* Corresponding author. Tel.: +886 2 26215656; fax: +886 2 26209924.
E-mail address: wjw@mail.tku.edu.tw (W.-J. Wang).
0040-4039/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2010.05.039

3744
H.-C. Kao et al. / Tetrahedron Letters 51 (2010) 3743–3747
N
N
N
N
NH3(g)
.HCl
N
HCl
H
N
N
Cl
1·HCl
2·HCl
H+
N
N
N
N
N
N
CH3I / CH2Cl2
C2H5Br, KOH / DMSO
N
C2H5
H
H
N
N
N
N
N
N
CH3
N
N
-
I
H
H
5
3
2
N
N
N
N
N
N
N
N
N
CH3
Picolyl Chloride, KOH / DMSO
CH3I, KOH / DMSO
N
N
6
4
Scheme 1.
Table 1
Reaction conditions of 1ꢀHCl, 2ꢀHCl, and 2
Entry
Substrate
Reagent(s)
Solvent
Temp (°C)
Time (h)
Product
Yield (%)
1
2
1ꢀHCl
2ꢀHCl
2ꢀHCl
2ꢀHCl
2ꢀHCl
2
2
2
2
NH3
NH4OH
2-BrPy/KOH
2-BrPy/KOH/catalystb
2-BrPy/KOH/catalystd
CH3I
CH3I/KOH
C2H5Br/KOH
2-PicCl/KOH
—
H2O
240
rt
190
240
180
rt
rt
rt
110
6
1
2ꢀHCl
76
99
—
—
—
93
53
50
43
2
3a
4a
5a
6
DMSO
ODCBc
DMSO
CH2Cl2
DMSO
DMSO
DMSO
72
72
72
24
48
120
24
—
—
—
3
4
5
7
8e
9
6
a
b
c
No reaction.
Three treatments with different catalysts (CuI, Cu powder, and Cu powder with CuSO4).
ODCB = o-dichlorobenzene.
Two treatments with different catalysts (Cu powder and Cu powder with CuSO4) in solvothermal reactor.
Data were collected in NMR tube reaction without separation.
d
e
the point of view of ligand design, 2 is difficulty to modify because
the lone pair electrons on the nitrogen are integrated into as a part
However, after treatment of 2 with iodomethane in dichloro-
methane and then stirring at room temperature overnight, the ring
nitrogen mono-methylated product 3 in high yields was resulted
(Scheme 1).10 We then turned our attention to the preparation of
methylation of the bridging amino-substituted bis-1,10-phen-
anthrolines. Upon refluxing 2 in dimethyl sulfoxide in the presence
of potassium hydroxide and iodomethane, the corresponding
bridge-amino-substituted bis-1,10-phenanthrolines 411 (Scheme 1)
was readily obtained in good yields. The regioselectivity of methyl-
ation is thus strongly dependent on the reaction conditions, such
as the solvent and base. In aprotic solvent (such as dichlorometh-
ane) and without base, the reaction gives phenanthroline–N-added
product 3, whereas that in aprotic solvent with base gives amino-
substituted product 4. We then chose to use other bromoalkane
of the delocalized
p-system. Many efforts on the preparation of
nitrogen-substituted
bis-1,10-phenanthrolines have been
evaluated.5,6
Initially, we were uncertain as to whether selective alkylation
can be carried out between the bridging and the pyridine N-atom.
Thus, we first attempted the methylation of 2ꢀHCl with iodometh-
ane in dimethyl sulfoxide (or in methanol) in the presence of KOH
(or K2CO3), and those experiments were unsuccessful. Further-
more, we also attempted to couple aryl halide with 2ꢀHCl by Ull-
mann-type reaction under various conditions (CuI, Cu powder, Cu
powder with CuSO4, high temperature, or high pressure) and again
these experiments were unsuccessful.

H.-C. Kao et al. / Tetrahedron Letters 51 (2010) 3743–3747
3745
He
Hd
He
Hd
Hc
Hf
N
Hf
N
Hd
He
Hb'
Hc
Ha'
Hd
He
Hc
Hf
N
Hf
N
Hc
Hb
Hg
Hh
Hc'
Hd'
Hb
Hg
N
N
N
N
N
N
Hb
Hg
Hb
Hg
N
N
N
N
Hi
Ha
Ha
i
CH3
N
N
N
N
N
N
i
Ha
Ha
CH3
He'
Hh
Hh
Hf'
Hg'
2.HCl
3
2
4
Figure 1. Structure of 2ꢀHCl, 2, 3, and 4.
Figure 2. (a) ORTEP representations of the X-ray crystal structures of compound 2 showing 50% probability thermal ellipsoids. Solvent and anion atoms are omitted for
clarity. Selected bond lengths (Å) and angles (°): N(1)–C(1) 1.368(12), N(1)–C(6) 1.352(11), N(2)–C(8) 1.378(10), N(2)–C(12) 1.366(10), N(3)–C(12) 1.386(10), N(3)–C(13)
1.362(10), N(4)–C(13) 1.325(9), N(4)–C(18) 1.371(9), N(5)–C(20) 1.344(10) and N(5)–C(24) 1.334(11) Å; C(13)–N(3)–C(12) 127.4(6). (b) ORTEP representations of the X-ray
crystal structures of the 2ꢀHCl cation showing 50% probability thermal ellipsoids. Solvent and anion atoms are omitted for clarity. Selected bond lengths (Å) and angles (°):
N(1)–C(1) 1.311(15), N(1)–C(6) 1.330(15), N(2)–C(8) 1.361(14), N(2)–C(12) 1.305(16), N(3)–C(12) 1.423(16), N(3)–C(13) 1.374(14), N(4)–C(13) 1.338(14), N(4)–C(18)
1.378(13), N(5)–C(20) 1.385(14), N(5)–C(24) 1.316(18); C(13)–N(3)–C(12) 131.4 (10).
and chloroalkane to investigate the mono-alkylation of the bridg-
ing-N. Using bromoethane and picolyl chloride furnished 5 and 6
(Scheme 1) in moderate to good yields, respectively (see Table 1).
In the 1H NMR spectrum of the symmetric compound 2ꢀHCl
(Fig. 1), seven absorption signals were observed, confirming that
the acyclic 2ꢀHCl has a C2 symmetry structure. The lowest field res-

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H.-C. Kao et al. / Tetrahedron Letters 51 (2010) 3743–3747
onance is the Ha hydrogen (at 9.25 ppm) which is adjacent to the
nitrogen of the side pyridine ring. In the acyclic 2ꢀHCl structure,
the NH proton can be exchanged with solvent so that it was not
observed.
lecular hydrogen bond with nitrogen atom on the opposite 1,10-
phenanthroline ring with a pseudo six-member ring structure.
The hydrogen bonding is one of the driving forces for such an acy-
clic molecule to retain the planar structure in syn-structure. The
interannular bond lengths of N(3)–C(12) and N(3)–C(13) are
1.423(16) and 1.374(14) Å, respectively. The latter one displays a
partial double bond character. The observed bond lengths indicate
that the bridging nitrogen atom prefers to connect the protonated
1,10-phenanthroline ring through a partial C@N imine bond. The
results suggest an electronic coupling between the bridging NH
group and the protonated 1,10-phenanthroline ring system is pre-
sented, where the NH group to the nonprotonated 1,10-phenan-
throline has more amine character.
The 1H NMR spectrum (in DMSO-d6) of compound 2 (Fig. 1) has
a quite different pattern from the protonated 2ꢀHCl. The lowest
field resonance gives
a very sharp peak for the NH (at
10.98 ppm) that bridges the two 1,10-phenanthroline rings. Sur-
prisingly, a broad peak for Hg proton (at 8.88 ppm) was observed
in compound 2, instead of the sharp NH peak observed for com-
pound 2ꢀHCl. Based on the comparison of NMR spectra with 2ꢀHCl,
a
large downfield shift of the Hg proton was observed
(D
d = 0.90 ppm). The large downfield shift for Hg proton implies
that it is further deshielded by the nearby 1,10-phenanthroline
ring in the presumed transoid planar arrangement. It may be ex-
pected that the transoid structure can provide an environment to
generate the interaction of the CHg group with nitrogen atom of
the nearby 1,10-phenanthroline ring, leading to the formation of
CHꢀ ꢀ ꢀN hydrogen bond.
The crystal structure analysis revealed that its central hydrogen
atom is localized on one of the opposite central nitrogen atoms
similar to those of free base porphyrin and H2HAPP.6a Although
there is no significant difference for the C–N bond distances of
the two different inner nitrogen atoms,15 the C–N–C angle of the
protonated N atom (121.5°) is larger than that of nonprotonated
one (116.9°). This angle difference is in agreement with similar
structures reported.16
In conclusion, a family of acyclic bis-1,10-phenanthroline deriv-
atives has been synthesized and characterized by using X-ray crys-
tal structure analysis. These compounds are quite distinctive from
other related macrocycles, where the acyclic compounds show a
transoid structure upon alkylation. We have developed a conve-
nient and efficient method to prepare methylated 1,10-bis-phe-
nanthroline with high regioselectivity. Efforts to prepare other
derivatives are currently being pursued in our laboratory. The unu-
sual intramolecular CHꢀ ꢀ ꢀN hydrogen bond in acyclic derivatives
has shown to cause a broadening in NMR peaks. The free rotation
of the two phenanthroline rings around C–N bond gives the sharp
NH peak. These two unique phenomena confirmed the transoid
structure of compound 2 in solution and solid state, respectively.
We believe that this class of ligands has a great potential for future
research involving analogs of 1,10-phenanthroline with biological
activities.
The 1H NMR spectrum of compound 3 (Fig. 1) in DMSO-d6 at
room temperature shows sixteen absorption signals in the spec-
trum resulting from an asymmetric conformation of 3. The detailed
assignment of these absorption peaks with the assistance of homo-
COSY technique indicated that the methylation takes place on the
outer nitrogen atom of 1,10-phenanthroline.
The 1H NMR spectrum of compound 4 (Fig. 1) in DMSO-d6 at
room temperature displays seven absorption signals that imply
an acyclic C2 symmetry structure, similar in pattern to 2ꢀHCl. The
results of NMR spectral analysis indicate that 4 has an amino-
substituted bis-1,10-phenanthrolines structure.
The ORTEP12 representations of 2 and 2ꢀHCl with atomic number-
ing are given in Figure 2.13 The X-ray crystal structure of 2 (Fig. 2a)
shows that two 1,10-phenanthroline rings are connected by bridg-
ing NH group, confirming the proposed transoid structures. It has a
near planar geometry, and the dihedral angle between the two
1,10-phenanthroline ring planes is only 28.9°. This crystal packing
is quite typical for the aromatic molecules in a pseudo-herringbone
pattern. The molecular packing diagram does not show any short
intermolecular distance (less than 4.0 Å) between the centers of
Acknowledgments
gravity of different rings, indicating no
p–p interactions in the
lattice. In addition, a geometry optimization calculation for the tor-
sional angles was performed with CAChe14 using the PM3-Hamilto-
nian. The calculated minimum (35.8°) is close to the experimental
value observed in the X-ray crystal structure (28.9°). However, the
torsion angle can vary from 90° to 5° with only 0.5 kcal molꢁ1
changes in the heat of formation. These results give support for a
twisted structure also in solution. This twisted structure is further
supported by the presence of a broad peak of CHg proton (at
8.88 ppm) and a sharp singlet peak at 10.98 ppm, as resulted from
the NH proton in its 1H NMR spectrum recorded in DMSO-d6.
The interannular bond lengths of N(3)–C(12) and N(3)–C(13)
are 1.386(10) and 1.362(10) Å, respectively, and have a partially
double bond character. This indicates the presence of electronic
coupling between the NH group and the two 1,10-phenanthroline
ring systems. The C(11)H–N(4) distance is only 2.95 Å, shorter than
the summation of their van der Waal’s radius, suggesting a forma-
tion of hydrogen bond. Indeed, an investigation of their NMR spec-
tra revealed that a broad peak of CHg proton appeared in solution
state. These results indicate the presence of a weak CH–N interac-
tion between the two 1,10-phenanthroline rings in both solid and
solution states.
This work was financially supported by the National Science
Council of Taiwan (NSC 96-2113-M-032-004) and Tamkang Uni-
versity. The authors thank Distinguished Professor C.-T. Lin (North-
ern Illinois University at DeKalb) for reading the Letter.
Supplementary data
Supplementary data (chemical structures, selected 1H, and 13C
NMR data) associated with this article can be found, in the online
version, at doi:10.1016/j.tetlet.2010.05.039.
References and notes
1. Kalyanasundaram, K. Photochemistry of Polypyridine and Porphyrin Complexes;
Academic Press: New York, 1992.
2. Kelly, D. M.; Vos, J. G. In Electroactive Polymer Electrochemistry Part 2; Lyons, M.
E. G., Ed.; Plenum Press: New York, 1994; pp 173–232.
3. Sammes, P. G.; Yahioglu, G. Chem. Soc. Rev. 1994, 327–334.
4. (a) Cheng, C.-C.; Kuo, Y.-N.; Chuang, K.-S.; Luo, C.-F.; Wang, W.-J. Angew. Chem.,
Int. Ed. 1999, 38, 1255–1257; (b) Hirai, M.; Shinozuka, K.; Sawai, H.; Ogawa, S.
Chem. Lett. 1992, 2023–2026; (c) Davis, J. T. Angew. Chem., Int. Ed. 2004, 43,
668–698; (d) Tan, J.-H.; Gu, L.-Q.; Wu, J.-W. Mini-Rev. Med. Chem. 2008, 8,
1163–1178; (e) Reed, J. E.; Neidle, S.; Vilar, R. Chem. Commun. 2007, 4366–
4368.
5. (a) Ogawa, S.; Yamaguchi, T.; Gotoh, N. J. Chem. Soc., Chem. Commun. 1972, 577–
578; (b) Ogawa, S.; Yamaguchi, T.; Gotoh, N. J. Chem. Soc., Perkin Trans. 1 1974,
976–978; (c) Krapcho, A. P.; Sparapani, S.; Leenstra, A.; Seitz, J. D. Tetrahedron
Lett. 2009, 50, 3195–3197; (d) Conecpcin, J.; Just, O.; Leiva, A. M.; Loeb, B.; Rees,
W. S., Jr. Inorg. Chem. 2002, 41, 5937–5939.
Compound 2ꢀHCl (Figure 2.b) was shown to have a planar syn-
structure, contrary to the results of transoid structure of 2. The
dihedral angle between the two 1,10-phenanthroline planes is only
3.4°. Meanwhile, a proton bonded to N(4) atom was found in the
crystal structure analysis that resulted in the formation of intramo-

H.-C. Kao et al. / Tetrahedron Letters 51 (2010) 3743–3747
3747
6. (a) Wang, W.-J.; Chuang, K.-S.; Luo, C.-F.; Liu, H.-Y. Tetrahedron Lett. 2000, 41,
8565–8568; (b) Wang, W.-J.; Sengul, A.; Luo, C.-F.; Kao, H.-C.; Cheng, Y.-H.
Tetrahedron Lett. 2003, 44, 7099–7101.
room temperature for 48 h. It was then diluted with water (100 mL), which
lead to the immediate deposition of a fine yellow precipitate and was collected
by filtration, washed with water (3 ꢂ 20 mL), and the yellow solid was
recrystallized from methanol and dried to yield 4 (55 mg, 53%). 1H NMR
(DMSO-d6) d 9.13(dd, J = 4.2, 3.0 Hz, 2H), 8.54 (dd, J = 9.0, 3.0 Hz, 2H), 8.53(d,
J = 8.8 Hz, 2H), 8.27 (d, J = 8.8 Hz, 2H), 7.97 (d, J = 9.0 Hz, 2H), 7.90 (d, J = 9.0 Hz,
2H), 7.80 (dd, J = 9.0, 4.2 Hz, 2H), 5.25 (s, 3H). ESI-MS (M+H) = 388. Anal. Calcd
for C25H17N5: C, 77.50; H, 4.42; N, 18.08. Found: C, 77.02; H, 4.58; N, 17.83.
12. Johnson, C. K. ORTEP II; Report ORNL-5138; Oak Ridge National Laboratory: Oak
Ridge, TN, 1976.
7. A dichloromethane solution (5 mL) of 1 (0.9 g, 4.2 mmol) was added with
HCl(aq) solution until no white precipitate was generated. The precipitate was
collected and dried under vacuum by heating under N2 at 120 °C (10 min).
During this period of time, the material changed its color from white to yellow,
which was then heated under NH3 atmosphere at 240 °C (6 h) until the
material color turned to deep brown. After washing with dichloromethane and
cold methanol, the brown powder was recrystallized by slow diffusion from
diethyl ether into concentrated methanol solution to afford 2ꢀHCl (1.3 g, 76%).
1H NMR (DMSO-d6) d 9.25 (d, J = 1.8, 4.4 Hz, 1H), 8.85 (d, J = 8.3 Hz, 1H), 8.71
(dd, J = 8.3, 1.8 Hz, 1H), 8.18 (d, J = 8.8 Hz, 1H), 8.15 (d, J = 8.8 Hz, 1H), 7.98 (dd,
J = 8.3, 1.8 Hz, 1H), 7.97 (d, J = 7.97 Hz, 1H). 13C NMR (DMSO-d6) d158.6; 150.9;
150.6; 142.2; 142.1; 138.3; 138.0; 131.0; 127.7; 127.3; 124.9; 124.1; 122.8;
115.0. ESI-MS (M+H) = 374.
13. Crystallographic data and data collection parameters:
(a) Crystallographic data for 2ꢀHCl: C25H16N5O1Cl1, Orthorhombic, space group
Pca21,
yellow,
a = 23.8555(26) Å,
b = 7.1932(8) Å,
R (I >2r(I)), R1 = 0.088, wR2 = 0.171,
c = 24.3363(24) Å,
V = 4176.0(8) Å3, T = 298 K, Z = 8. Final
Final R (all data), R1 = 0.148, wR2 = 0.2030, GOF = 1.117. 10,913 reflections were
measured (5685 unique, Rint_0.088) on a Siemens P4 diffractometer in the
range 1.90 < u < 25.10°, ꢁ25 < h < 25, ꢁ8 < k < 1, ꢁ27 < l < 25, operating in v
8. The crude product of 2ꢀHCl was dissolved in water (280 mL) and then adjusted
to pH 8 by addition of NH4OH solution. The deep brown precipitates were
generated while the pH value changes. The product was collected by filtration
scan mode and using graphite-monochromated Mo-Ka radiation (l_0.71073 Å).
Semi-empirical absorption correction via eight scans was applied. Structure
solution and refinement: The structure was solved by the direct method and
refined anisotropically based on F2 by full-matrix least-squares techniques
using the SHELXTL (Ver 5.10) program. All hydrogen atoms were located by
Fourier synthesis and refined isotropically without any constraints or
restraints. The final refinement gave R1_0.088, wR2_0.171.
and was thoroughly extracted by Soxhlet with acetone to afford
2 in
quantitative yield. 1H NMR (DMSO-d6) d 10.98 (s, 1H), 9.12 (d, J = 1.8, 4.2 Hz,
2H), 8.88 (br d, 2H), 8.46 (d, J = 9.0 Hz, 2H), 8.45 (dd, J = 1.8, 8.4 Hz, 2H), 7.93 (d,
J = 9.0 Hz, 1H), 7.81 (d, J = 9.0, 2H), 7.74 (dd, J = 4.2, 8.4 Hz, 2H). 13C-NMR
(DMSO-d6) d 153.8; 149.7; 144.5; 144.1; 138.2; 136.1; 128.6; 126.3; 124.1;
123.7; 122.9; 115.1. Anal. Calcd for C24H15N5: C, 77.20; H, 4.05; N, 18.76.
Found: C, 77.25; H, 4.20; N, 18.78.
(b) Crystallographic data for 2: C24H15N5, Monoclinic, space group P21/c, red,
a = 13.8168(61) Å, b = 16.7479(73) Å, c = 9.9491(87) Å, b = 108.375(54)°,
V = 2184.86(414) Å3, T = 298 K, Z = 1. Final R (I >2r(I)), R1 = 0.277, wR2 = 0.286,
GOF = 0.848. 4080 reflections were measured (3839 unique, Rint_0.277) on a
Siemens P4 diffractometer in the range 2.0 < u < 25.0°, ꢁ16 < h < 15,
9. March, J. Advanced Organic Chemistry, 3rd ed.; John Wiely & Sons: New York,
1985; pp. 66–70.
10. A dichloromethane solution (10 mL) of 2 (100 mg, 0.27 mmol) was added with
iodomethane dropwise (62
l
L, 0.35 mmol), and the resulting yellow solution
ꢁ19 < k < 1, ꢁ1 < l < 11, operating in
v
scan mode and using graphite-
was stirred at room temperature overnight. The yellow precipitate thus formed
was collected by filtration, washed thoroughly with dichloromethane and n-
hexane, and dried to yield 3 as a light yellow solid (97 mg, 93%). 1H NMR
(DMSO-d6) d 10.85 (s, 1H), 9.58 (d, J = 9.5 Hz, 1H), 9.36 (d, J = 5.7 Hz, 1H), 9.24
(d, J = 8.6 Hz, 1H), 9.13(dd, J = 3.8, 1.9 Hz, 1H), 8.76 (d, J = 9.5 Hz, 1H), 8.47 (dd,
J = 7.6, 1.9 Hz, 1H), 8.44 (d, J = 8.6 Hz, 1H), 8.31 (d, J = 8.6 Hz, 1H), 8.24 (dd,
J = 8.6, 5.7 Hz, 1H), 8.12 (d, J = 8.6, 1H), 7.94 (d, J = 8.6 Hz, 1H), 7.85 (d,
J = 8.6 Hz, 1H), 7.72 (d, J = 8.6 Hz, 1H), 7.70 (dd, J = 7.6, 3.8 Hz, 1H), 5.30 (s, 3H).
13C NMR (DMSO-d6) d 152.8; 150.6; 149.9; 146.5; 144.7; 144.4; 139.5; 139.4;
138.3; 136.3; 136.1; 132.4; 130.2; 129.0; 127.8; 126.4; 124.3; 124.0; 123.6;
123.3; 123.2; 117.0; 114.9; 52.2. Anal. Calcd for C25H18N5I: C, 58.26; H, 3.52; N,
13.59. Found: C, 58.09; H, 3.66; N, 13.55.
monochromated Mo-K
a radiation (l_0.71073 Å). Semi-empirical absorption
correction via eight scans was applied. Structure solution and refinement: The
structure was solved by the direct method and refined anisotropically based on
F2 by full-matrix least-squares techniques using the SHELXTL (Ver 5.10) program.
All hydrogen atoms were located by Fourier synthesis and refined isotropically
without any constraints or restraints. The final refinement gave R1_0.099,
wR2_0.229.
The crystallographic data in CIF format have been deposited with the
Cambridge Crystallographic Data Centre as supplementary publication
numbers CCDC reference number 750240 and 750265. Copies of the data can
be obtained, free of charge, on application to CCDC, 12 Union Road, Cambridge
CB2 1EZ, UK [fax: +44(0) 1223 336033 or email: deposit@ccdc.cam.ac.uk].
14. CACheÒ 4.4 Windows, Fujitsu Limited, Japan, 2000.
11. Into dimethyl sulfoxide (20 mL) were successively added potassium hydroxide
(85 mg, 1.5 mmol) and 2 (100 mg, 0.27 mmol). The resulting deep-orange-
colored solution was stirred at room temperature for 30 min. Iodomethane
15. Nishigaki, S.; Yoshioka, H.; Nakatsu, K. Acta Crystallogr., Sect. B 1978, 34, 875–
879.
(62
lL, 0.35 mmol) was then added and the orange solution was stirred at
16. Hensen, K.; Kettner, M.; Bolte, M. Acta Crystallogr., Sect. C 1998, 54, 359–361.