Toward a chemiluminescent molecular device: Metal ion-enhanced chemiluminescence of benzylidenacridan with 15-monoazacrown-5

Article abstract of DOI:10.1021/jo801556p

The benzylidenacridans (1a-d) with one or more methoxy groups emit light from the excited N-methylacridone (NMA) when treated with a solution of sodium hypochlorite and alkaline hydrogen peroxide, in which a Hammett relationship with a negative ρ value wa

Full text of DOI:10.1021/jo801556p

Toward a Chemiluminescent Molecular Device: Metal Ion-Enhanced
Chemiluminescence of Benzylidenacridan with 15-Monoazacrown-5
Jiro Motoyoshiya,* Toshimitsu Tanaka, Motoki Kuroe, and Yoshinori Nishii
Department of Chemistry, Faculty of Textile Science and Technology, Shinshu UniVersity, Ueda,
Nagano, 386-8567, Japan
jmotoyo@shinshu-u.ac.jp
ReceiVed July 23, 2008
The benzylidenacridans (1a-d) with one or more methoxy groups emit light from the excited
N-methylacridone (NMA) when treated with a solution of sodium hypochlorite and alkaline hydrogen
peroxide, in which a Hammett relationship with a negative F value was applied between the
chemiluminescence quantum yields and the σ values. However, the dimethylamino group drastically
inhibited the chemiluminescence in spite of its low σ value. While the compound (2) with 15-
monoazacrown-5 also showed a very weak chemiluminescence upon treatment with tetrabutylammonium
hydroxide and hydrogen peroxide in acetonitrile, the chemiluminescence was enhanced up to 20 times
in efficiency when divalent metal cations, such as magnesium and calcium ions, were added. The
chemiluminescence inhibition is proved to be due to the shortening of the fluorescence lifetime of NMA
due to energy dissipation by the amino substituents, but the incorporation of calcium ion into the cavity
of the azacrown significantly prolonged the lifetime. Thus, the possibility of metal ion sensing by a
chemiluminescent molecular device is suggested.
Introduction
less attention has been paid to the chemiluminescent systems,
whose greatest advantage is needless of an electric light source
to prevent reduction of the sensitivity due to the background.
To utilize the chemiluminescent reaction for molecular sensing,
there are two categories of methods: Namely, the first is energy
transfer chemiluminescence using suitable fluorescent devices
and chemiluminescent molecules as the energy supplements that
produces excitation of the fluorescent energy acceptors.1 The
second is the chemiluminescence device whose emission is
modulated by the target molecule.4 In this paper, we report the
chemiluminescent system based on the latter concept, that is,
suitable metal cations combine with the chemiluminescent
molecules, resulting in an enhanced chemiluminescence intensity.
Since the early study by McCapra et al.,5 chemiluminescence
from the thermal decomposition of acridan dioxetanes generated
by singlet oxygenation of several benzylidenacridans has been
Chemiluminescence is a phenomenon in which an electroni-
cally excited molecule is generated during the chemical reaction
and emits light as a visual output. Of significance is the
application of chemiluminescence to analytical chemistry1 as
well as in the field of biotechnology if the target chemical
species can be monitored as a light emission signal.2 In spite
of numerous reports of fluorescent devices for these purposes,3
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M. Anal. Chim. Acta 2005, 541, 25–35.
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696. (b) Gokel, G. W.; Leevy, W. M.; Weber, M. E. Chem. ReV. 2004, 104,
2723–2750. (c) Powe, A. M.; Fletcher, K. A.; St, N. N.; Lowry, M.; Neal, S.;
McCarroll, M. E.; Oldham, P. B.; McGown, L. B.; Warner, I. M. Anal. Chem.
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2007, 129, 10322–10323. (e) Koide, Y.; Urano, Y.; Kennmoku, S.; Kojima, H.;
Nagano, T. J. Am. Chem. Soc. 2007, 129, 10324–10325.
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(b) Okamoto, H.; Owari, M.; Kimura, M.; Satake, K. Tetrahedron Lett. 2001,
42, 7453–7455. (c) Okamoto, H.; Kimura, M. Chem. Lett. 2005, 34, 1452–1453.
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J. Chem. Soc., Chem Commun 1977, 944–946.
1014 J. Org. Chem. 2009, 74, 1014–1018
10.1021/jo801556p CCC: $40.75 2009 American Chemical Society
Published on Web 12/22/2008

Toward a Chemiluminescent Molecular DeVice
SCHEME 1. Chemiluminescence Reaction of
9-Benzylidenacridans
CHART 1. Structures of Benzylidenacridans Used in This
Study
occasionally investigated6 and it is suggested that the unstable
1,2-dioxetanes were generated as the intermediates,7 in which
the corresponding aldehydes and the fluorescent N-methylac-
ridone (NMA), the latter of which is the emitter, were formed
as the decomposition products (Scheme 1). In this chemilumi-
nescence reaction, the Hammett relationship with a negative F
value is adopted between the σ values of the substituents on
the benzylidene moieties and the chemiluminescence efficiency;8
namely, the electron-donating substituents efficiently promote
the chemiluminescence process. However, the dimethylamino
group is the exception as it drastically inhibits the chemilumi-
nescence.9 The interesting feature of this chemiluminescence
system encourages us to apply it to a new metal sensing system
using the selective metal incorporating function of the azacrown
ether. In this paper, we report the chemiluminescence behavior
of the 9-benzylidene-10-methylacridans bearing 15-monoaza-
crown-5, in which the azacrown acts as a metal cation
recognition site and the chemiluminescence efficiency is selec-
tively enhanced in the presence of magnesium and calcium
cations.
TABLE 1. Data of the Chemiluminescence Reaction of
Benzylideneacridanes (1)
a
c
R
∑σ
104ΦCL
Φrb
104ΦS
1a
1b
1c
1d
1e
p-OMe
m-OMe
2,4-(OMe)2
3,4,5-(OMe)3
p-NMe2
-0.27
110
0.33
2.7
4.3
0.094
0.91
0.83
1.0
0.99
1.00
130
0.44
3.0
0.12
-0.03
-0.83
4.8
0.1
a Measured by the photon-counting method. b Determined by the UV
spectrum. c Calculated by ΦCL ) ΦrΦSΦF (ΦF: fluorescence quantum
yield of NMA, 0.9 in methanol).
Results and Discussion
The benzylidenacridans used in the present study were
prepared by the Horner-Wadsworth-Emmons reaction of
9-diethylphosphono-10-methylacridan and the corresponding
aromatic aldehydes.8 Their structures are shown in Chart 1.These
benzylidenacridans were subjected to the chemiluminescence
reaction by singlet oxygenation, using a combination of
hydrogen peroxide and sodium hypochlorite in aqueous metha-
nol as a singlet oxygen evolution system.10 When 1a was treated
at a high concentration of the substances under these conditions,
it emits a flash of blue light observable by the naked eye, whose
chemiluminescence spectrum was in agreement with the fluo-
rescence spectrum of NMA, indicating that the excited NMA
FIGURE 1. Hammett relationship of chemiluminescence singlet
quantum yields.
was generated by this oxidation reaction. The total chemilumi-
nescence quantum yield (ΦCL) of 1a under the optimized
reaction conditions was estimated as 0.011 einstein/mol. A few
other compounds with two or three methoxy groups (1b-d)
also emit light, and an approximately linear relationship with
the negative slope exists between the logarithm of their singlet
excitation yields (ΦS) and the sum of the Hammett σ values
(Table 1 and Figure 1). On the contrary, the similar treatment
of 1e bearing a dimethylamino group gave an extremely weak
chemiluminescence in spite of its small σ value, whose ΦS was
only 1/1300 compared to that of 1a.
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To investigate such an effect of the dimethylamino group on
the chemiluminescence inhibition, some spectral studies were
1
carried out. Analysis of the reaction products from 1e by H
J. Org. Chem. Vol. 74, No. 3, 2009 1015

Motoyoshiya et al.
incorporated in the cavity of the crown, the fluorescence maxima
shift, in many cases, to the somewhat shorter wavelengths with
a change in their intensities. Such a spectral change is the basis
for application of the metal ion fluorescence sensing employing
the crown compounds. Therefore, we prepared the benzylide-
nacridan (2) with 15-monoazacrown-5 as the metal ion recogni-
tion site and examined whether it acts as a chemiluminescent
molecular device for a metal ion sensing system. Two ben-
zylidenacridans 2 and 1e as a control compound were reacted
with singlet oxygen generated from a mixed solution of
tetrabutylammonium hydroxide and aqueous hydrogen peroxide
in acetonitrile,14 which is one way to generate singlet oxygen
without metal cations. As expected, only a slight light emission
was observed for 2 and 1e, in which the total chemiluminescence
quantum yields (ΦCL) were estimated to be 4.6 × 10-5 einstein/
mol for 2 and 1.2 × 10-5 einstein/mol for 1e. These chemilu-
minescence reactions can be regarded as almost nonchemilu-
minescent in a sense. The stronger chemiluminescence inhibition
of the dimethylamino group compared to the azacrown seems
to reflect the larger free rotation of the dimethylamino group
than the azacrown.13a Upon the addition of the alkaline metal
perchlorites, enhancement of the chemiluminescence efficiency
with increasing metal ion concentration was detected, while no
significant change was observed for 1e even in the presence of
a large excess amount of the metal cations. Among the alkaline
metal cations, the sodium cation was the most effective, but
the ΦCL increased by only ca. 7 times compared to the case
without the sodium cation. A much larger effect was observed
when the divalent cations, magnesium or calcium ions, were
added instead, and the ΦCL values increased by almost 20 times
compared to that without those cations. Unfortunately, the effect
of barium ion at high concentration was not known because of
insolubility of its perchlorite in this solvent system. A large
excess amount of the cations is needed to obtain this emission
intensity probably because of the decreased metal ion binding
ability of the crown in the aqueous media. All the results are
shown in Figure 3. Consequently, this azacrown compound was
revealed to work as a tentative, chemiluminescent device
providing information about coexisting metal cations.
To explore the chelation effect of 2, a spectral study was
carried out. Since the fluorescence intensity increased with the
increasing calcium ion concentration as shown in Figure 4, 2
might be one of the fluorescence sensors that is also chemilu-
minescent. The gradual change in the fluorescence spectrum
allowed us to estimate the stability constants assuming that 1:1
complexes are formed.15 These values are presented in Table
2, and those for the divalent metal cations are greater than those
for alkaline metals. As the cavity size of the 15-monoazacrown-5
is between 1.7 and 2.2 Å, sodium and calcium cations fit its
cavity.16 A slightly larger effect of the sodium cation among
the alkaline metals and a much larger effect of the calcium ion
agree with the adaptation, although the stability constants for
the alkaline metals do not agree with this adaptation. It is
suggested that the lithium cation is solvated with solvent
molecules that gives the higher stability constants than expected
for the ionic diameter of the free lithium cation.17 The
enhancement of calcium ion is the most satisfactory from the
FIGURE 2. The change in the fluorescence spectral intensity with the
addition of the quenchers: (a) 4-(dimethylamino)benzaldehyde as a
quencher and (b) N,N-dimethylaniline as a quencher. The ratios of
[quencher]/[NMA] are 0 shown by trace 1 (black), 0.1 bytrace 2 (pink),
1 by trace 3 (yellow), 10 by trace 4 (blue), 100 by trace 5 (green), and
1000 by trace 6 (red), respectively.
NMR revealed that two fragments, NMA and 4-(dimethylami-
no)benzaldehyde, were formed as a 1:1 mixture, which suggests
that the singlet oxygenation proceeded to form the dioxetane
intermediate even in this almost nonchemiluminescent reaction.
Additionally, the oxidation of 1a emits light even in the presence
of a large excess amount of two amino compounds as quenchers,
i.e., 4-(dimethylamino)benzaldehyde and N,N-dimethylaniline.
Thus, the chemiluminescence inhibition due to deactivation of
the singlet oxygen11 is ruled out. On the other hand, only a
slight change in the fluorescence intensity of NMA was observed
when a large excess amount of 4-(dimethylamino)benzaldehyde
was added to the NMA solution, but N,N-dimethylaniline
showed a much stronger fluorescence quenching effect than the
aldehyde (Figure 2). Thus, the fluorescence quenching effect
of the dimethylamino group was established12 and the effect is
considered to arise from photoinduced electron transfer (PET)
or the dissipation of the excitation energy of NMA due to
rotation of the dimethylamino group if the fluorescence quench-
ing is caused in a similar manner to the benzoxazinone derivative
with dimethylamino group.13a Attachment of the formyl group
electronically conjugating with the dimethylamino group in
4-(dimethylamino)benzaldehyde might reduce both the electron
density of the nitrogen atom and the free rotation of the
dimethylamino group, resulting in decreasing quenching ability.
Although the fluorescence quenching by these quenchers is weak
in the intermolecular system, it would be strong enough to
quench the emitter, the excited NMA, if such an interaction
would work in a solvent cage and even in an intermolecular
fashion.
The remarkable effect of the amino group prompted us to
apply it to the possibility of a molecular device, that is, the
chemiluminescence could be controlled by the coexisting metal
cations, if the quenching ability is modulated by metal chelation.
Some fluorescent devices bearing the azacrowns as the iono-
phores are known to change their fluorescence spectra in the
presence of suitable metal cations.13 When the metal cation is
(11) Darmanyan, A. P.; Jenks, W. S. J. Phys. Chem. A 1998, 102, 7420–
7426.
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Acta, Part A 2008, 69, 167–173.
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Chem. 1988, 92, 6233–6237. (b) Bourson, J.; Pouget, J.; Valeur, B. J. Phys.
Chem. 1993, 97, 4552–4557. (c) Dumon, P.; Jonusauskas, G.; Dupuy, F.; Pee,
P.; Rulliere, C.; Letard, J.- F.; Lapouyade, R. J. Phys. Chem. 1994, 98, 10391–
10396. (d) Mathevet, R.; Jonusauskas, G.; Rulliere, C.; Letard, J.-F.; Lapouyade,
R. J. Phys. Chem. 1995, 99, 15709–15713. (e) Crochet, P.; Malval, J.-P.;
Lapouyade, R. Chem. Commun. 2000, 289–290.
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E. A.; Miyamoto, S.; Martinez, G. R.; Medeiros, M. H. G.; Mascio, P. D. Anal.
Chim. Acta 2003, 482, 99–104.
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1709–1910.
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Frendsdorf, H. K. Angew. Chem., Int. Ed. Engl. 1972, 11, 16–25.
1016 J. Org. Chem. Vol. 74, No. 3, 2009

Toward a Chemiluminescent Molecular DeVice
FIGURE 3. Metal cation effect on the chemiluminescence quantum yield (a) for azacrowned compound 2 and (b) for dimethylamino derivative 1e.
[2] ) [1e] ) 1 × 10-6 M.
TABLE 3. The Change in the Fluorescence Lifetime (τ) of NMAa
aldehyde
(M)
Ca(ClO4)2
(M)
order
lifetime t (ns)
none
10-6
none
none
10-6
10-5
10-4
10-3
10-2
1
1
1
1
1
1
2
7.607
6.716
7.489
7.607
7.607
9.118
9.522 (51%), 18.279 (49%)
a [NMA] ) 10-6 M in acetonitrile.
FIGURE 4. Fluorescence spectral change of 2 in the presence of
calcium perchlorite in acetonitrile, [2] ) 1.0 × 10-5 M: (1) no addition
of Ca(ClO4)2, (2) [Ca(ClO4)2] ) 1 × 10-5 M, (3) 1 × 10-4 M, (4) 1 ×
10-3 M, (5) 1 × 10-2 M, (6) 1 × 10-1 M.
there are two fluorescent species with the lifetimes of 9.52 and
18.28 ns, the latter of which is almost 2.7 times longer than the
case without the calcium ion. Although we cannot identify what
kind of complexes are formed between the azacrown and
calcium ions for such a prolongation of the lifetime, the
interaction obviously prevents the dissipation of the energy of
the excited emitter. At present this is one of the explanations
why the incorporation of metal cations to the crown enhances
the chemiluminescence.
TABLE 2. Stability Constants and Ionic Diametersa
Li+
Na+
K+
Mg2+
Ca2+
Ba2+
ionic diameter (Å)
log K
1.16
1.98
1.94
1.17
2.66
2.03
1.32
3.01
1.98
2.71
2.68
3.3
a From ref 18.
In conclusion, we applied the chemiluminescence inhibition
of the amino-substituted benzylidenacridans to a metal ion
recognizing system using the azacrowned compound that
modulates the chemiluminescence in the presence of suitable
metal ions such as magnesium and calcium ions. While there
are some points to be improved, for instance, the quenching
system with the interaction by an intramolecular manner would
be much better, we present a chemiluminescent reaction that is
potentially interesting for developing a molecular device for
metal ion sensing. Well-refined chemiluminescent molecules can
be developed for sensing various important target molecules
and this is currently underway in our laboratory.
viewpoints of both the ionic diameter and the stability constant.
Considering the enhancement of the ΦCL by magnesium ion as
well as calcium ion, in spite of the absence of the data for barium
ion, it might be probable that the divalent cations with the higher
charge densities are more effective in binding to the azacrown
than the monovalent cations.
Since the change in the fluorescence lifetime of the emitter
is thought to be an important factor in the present system, the
measurements were carried out under various conditions in the
presence of the quencher and calcium ions (Table 3). The
lifetime of the free NMA in acetonitrile is about 7.5 ns.
Shortening of the fluorescence lifetime by about 1 ns was found
after the addition of an equimolar amount of the azacrowned
benzaldehyde, another fragment of the chemiluminescent reac-
tion. On the other hand, when 1 equiv of calcium ion to the
crown was added to the solution of both compounds, the lifetime
was recovered to that of free NMA. A remarkable prolongation
of the lifetime was observed at the higher concentration. It is
noteworthy that when a 104 times larger excess amount of
calcium ion compared to the azacrown benzaldehyde is added,
Experimental Section
General methods are provided as Supporting Information.
9-(4′-Methoxybenzylidene)-1-methyacridan (1a). To a solution
of 9-diethylphosphono-10-methylacridan (1.0 g, 3.02 mmol) in
tetrahydrofuran (THF) (10 mL) was added a solution of t-BuOK
(0.51 g, 4.53 mmol) in THF (5 mL) and a solution of p-
methoxybenzaldehyde (0.36 mL, 3.02 mmol) in sequence. After
the mixture was stirred for 8 h at room temperature, the solvent
was removed under reduced pressure. The residue was dissolved
in ethyl acetate and washed with saturated ammonium chloride
solution and brine. After the organic layer was dried over anhydrous
Na2SO4 and the solvent was removed under reduced pressure, the
(17) Pacey, G. E.; Wu, Y. P. Talanta 1984, 31, 165–168.
(18) Handbook of Chemistry and Physics, 66th ed.; CRC Press: Boca Ratan,
FL, 1995.
J. Org. Chem. Vol. 74, No. 3, 2009 1017

Motoyoshiya et al.
crude product was purified by column chromatography on silica
gel with ethyl acetate and hexane as the eluants to give a yellow
crystal (0.26 g, 28%). Mp 143 °C. H NMR δ 3.48 (s, 3H), 3.80
mmol), and 4-(13′-aza-1′,4′,7′,10′-tetraoxacyclopentadecan-13′′-
yl)benzaldehyde (0.35 g, 1.08 mmol) gave a yellow crystal (0.54
g, 93%). Mp 69 °C. 1H NMR δ 3.47 (s, 3H), 3.56-3.77 (m, 20H),
6.59 (s, 1H), 6.57-7.63 (m, 12H). 13C NMR δ 33.8, 52.9, 69.1,
70.5, 70.6, 71.7, 111.4, 112.5, 113.5, 120.3, 121.6, 121.7, 123.6,
123.9, 125.8, 127.7, 128.2, 128.3, 128.9, 130.0, 134.2, 142.0,
143.8,146.6. MS (m/z) 500 (M+). HRMS calcd for C31H36O4N2
500.2647, found 500.2645.
Chemiluminescence Quantum Yields (ΦCL). The measure-
ments were carried out by a photon-counting method with a
Hamamatsu Photonics R464 photomultiplier connected to a photon-
counting unit (C3866) and a photon-counting board M8784
according to a previously reported procedure,19 and the luminal
chemiluminescence was used as the standard in DMSO for
calibration of the photomultiplier tube. For a typical run, an aqueous
solution of hydrogen peroxide (1.0 × 10-5 M) (0.5 mL) and an
aqueous solution of tetrabutylammonium hydroxide (1.0 × 10-2
M) were added to a solution of 2 in acetonitrile (MeCN) (1.0 ×
10-6 M) (1 mL) in a quartz cell placed in front of the photomul-
tiplier at 25 °C and the photons generated for a 5 min period were
counted. The average of the values obtained by a few measurements
was used for the calculation of ΦCL. For the measurement in the
presence of the metal salt, a solution containing a certain concentra-
tion of metal perchlorites in MeCN was added to the solution of 2
in MeCN and left to stand for 2 h before being mixed with the
solution of alkaline hydrogen peroxide.
1
(s, 3H), 6.62 (s, 1H), 6.72-7.69 (m, 12H). 13C NMR δ 33.9, 55.6,
106.9, 112.7, 113.5, 114.0, 120.3,121.6, 122.9, 123.8, 128.1, 128.6,
129.0, 134.1. MS (m/z) 313 (M+). Anal. Calcd for C22H19NO: C,
84.31; H, 6.11; N, 4.47. Found: C, 84.35; H, 6.20; N, 4.45.
9-(3′-Methoxybenzylidene)-1-methyacridan (1b). A similar
procedure to the above with phosphonoacridan (0.51 g, 1.51 mmol),
t-BuOK (0.25 g, 2.26 mmol), and m-methoxybenzaldehyde (0.18
mL, 1.51 mmol) gave a viscous oil (0.26 g, 28%), which was
unstable and decomposed gradually. 1H NMR δ 3.48 (s, 3H), 3.67
(s, 3H), 6.63 (s, 1H), 6.69-7.71 (m, 12H). 13C NMR δ 33.9, 56.5,
112.8, 113.0, 113.6, 113.8, 120.3,121.7, 121.7, 122.9, 124.0, 128.4,
129.0, 129.4, 129.6. MS (m/z) 313 (M+).
9-(2′,4′-Dimethoxybenzylidene)-10-methylacridan (1c). A simi-
lar procedure to the above with phosphonoacridan (0.51 g, 1.51
mmol), t-BuOK (0.51 g, 4.53 mmol), and 2,4-dimethoxybenzal-
dehyde (0.25 g, 1.51 mmol) gave a yellow crystal, which was
1
recrystallized from benzene (0.24 g, 46%). Mp 142 °C. H NMR
δ 3.43 (s, 3H), 3.76 (s, 3H), 3.80 (s, 3H) 6.29 (m, 1H), 6.45-7.76
(m, 12H). 13C NMR δ 33.4, 55.4, 55.9, 98.8, 104.8, 112.6, 113.3,
118.7, 120.3, 121.5, 124.1, 128.0, 128.3, 128.9, 130.1. MS (m/z)
343 (M+). Anal.Calcd for C23H21NO2: C, 80.44; H, 6.16; N, 4.08.
Found: C, 80.80; H, 6.29; N, 4.11.
9-(3′,4′,5′-Trimethoxybenzylidene)-10-methylacridan (1d). A
similar procedure to the above with phosphonoacridan (0.51 g, 1.51
mmol), t-BuOK (0.51 g, 4.53 mmol), and 3,4,5-trimethoxybenzal-
dehyde (0.30 g, 1.51 mmol) gave a yellow crystal (0.09 g, 16%).
Acknowledgement. One of the authors (J.M.) is thankful for
the financial support by a Grant-in-Aid (19550137 and the
Grobal COE program), from the Ministry of Education, Culture,
Sports, Science and Technology of Japan.
1
Mp 137 °C. H NMR δ 3.50 (s, 3H), 3.71 (s, 6H), 3.85 (s, 3H),
6.57-7.71 (m, 11H). 13C NMR δ 33.9, 56.1, 61.3, 106.1, 112.8,
113.6, 120.2, 121.7, 122.9, 123.8, 128.3, 128.9, 129.5, 134.0, 153.3.
MS (m/z) 373 (M+). Anal. Calcd for C24H23NO3: C, 77.19; H, 6.21;
N, 3.75. Found: C, 77.09; H, 6.30; N, 3.73.
Note Added after ASAP Publication. Reference 19 was
added in the version published on January 13, 2009.
9-(4′-Dimethylaminobenzylidene)-10-methylacridan (1e). A
similar procedure to the above with phosphonoacridan (0.51 g, 1.51
mmol), t-BuOK (0.51 g, 4.53 mmol), and 4-(dimethylamino)ben-
zaldehyde (0.23 g, 1.51 mmol) gave a yellow crystal (0.18 g, 38%).
Supporting Information Available: General method for the
Experimental Section, the typical fluorescence decays of NMA,
1H NMR spectra of 1c, 1d, and 2, and 13C NMR spectrum of 2.
This material is available free of charge via the Internet at
http://pubs.acs.org.
1
Mp 116 °C. H NMR δ 2.93 (s, 3H), 3.42 (s, 3H), 6.59 (s, 1H),
6.61-7.68 (m, 12H). 13C NMR δ 33.9, 40.9, 112.6, 112.7, 113.6,
120.4, 121.7, 123.7,124.0, 127.9, 128.5, 129.1, 130.0. MS (m/z)
326 (M+). Anal.Calcd for C23H22N2: C, 84.63; H, 6.79; N, 8.58.
Found: C, 84.75; H, 6.87; N, 8.38.
JO801556P
(19) (a) Motoyoshiya, J.; Sakai, N.; Imai, M.; Yamaguchi, Y.; Koike, R.;
Takaguchi, Y.; Aoyama, H. J. Org. Chem. 2002, 67, 7314–7318. (b) Mo-
toyoshiya, J.; Ikeda, T.; Tsuboi, S.; Kusaura, T.; Takeuchi, Y.; Hayashi, S.;
Yoshioka, S.; Takaguchi, Y.; Aoyama, H. J. Org. Chem. 2003, 68, 5950–5955.
9-[4′-(13′′-Aza-1′′,4′′,7′′,10′′-tetraoxacyclopentadecan-13′′-yl)ben-
zylidene]-10-methylacridan (2). A similare procedure to the above
with phosphonoacridan (0.72 g, 2.16 mmol), t-BuOK (0.49 g, 4.32
1018 J. Org. Chem. Vol. 74, No. 3, 2009