Synthesis and photophysical studies of a series of quinazoline chromophores

Article abstract of DOI:10.1021/jo501305h

The synthesis of a series of push-pull arylvinyl (styryl), aryl, and arylethynyl quinazoline derivatives by means of different straightforward protocols is reported. The photophysical properties of the compounds are described. The preparation of arylvinyl

Full text of DOI:10.1021/jo501305h

Article
pubs.acs.org/joc
Synthesis and Photophysical Studies of a Series of Quinazoline
Chromophores
,†
,‡
Sylvain Achelle,* Julian Rodrıguez-Lopez,* and Franco̧
ise Robin-le Guen†
́
́
́
†Institut des Sciences Chimiques de Rennes UMR CNRS 6226, IUT de Lannion, rue Edouard Branly, BP 30219, F22302 Lannion
Cedex, France
‡
́
́
Facultad de Ciencias y Tecnologıas Quımicas, Universidad de Castilla-La Mancha, 13071 Ciudad Real, Spain
S
* Supporting Information
ABSTRACT: The synthesis of a series of push−pull arylvinyl
(styryl), aryl, and arylethynyl quinazoline derivatives by means
of different straightforward protocols is reported. The
photophysical properties of the compounds are described.
The preparation of arylvinylquinazolines was performed by
aldol condensation of the appropriate methylquinazoline and
functionalized benzaldehyde. Suzuki and Sonogashira cross-
coupling reactions were used to prepare the aryl and
arylethynyl compounds, respectively, starting from chloroqui-
nazolines. Optical studies revealed that all of the compounds
reported here behave in a way similar to that of their
pyrimidine counterparts, with absorption bands in the UV or
visible region and the emission of green light upon irradiation.
Large red shifts were observed in the fluorescence emission maxima upon increasing the solvent polarity. This strong emission
solvatochromism suggests the formation of an intramolecular charge-separated emitting state. The materials can be easily and
reversibly protonated at the nitrogen atoms of the heterocyclic ring, and this causes dramatic color changes. This phenomenon
opens up the possibility of developing colorimetric pH sensors that can be efficiently modified a posteriori for specific
applications.
known for their strong emission properties.8 Similar photo-
INTRODUCTION
■
physical behavior was observed with 4,6-bis(arylethynyl)-
pyrimidines and 2,4,6-tris(arylethynyl)pyrimidines.9 In addition
to intense fluorescence,10 electron-donor-substituted 4-
(arylvinyl)pyrimidines and 4,6-bis(arylvinyl)pyrimidines are
known to exhibit second-11 and third-order NLO properties.12
In particular, 4,6-bis(arylvinyl)pyrimidines are now well-
established two-photon absorption (TPA) chromophores.
Recently, some of us compared the photophysical properties
of 2-(arylvinyl)pyrimidines and 4-(arylvinyl)pyrimidines13 and
carried out a statistical study to predict the photophysical
properties of pyrimidine derivatives.14
During the past decade, there has been strong interest in the
synthesis of pyrimidine (1,3-diazine) chromophores.1 The
pyrimidine ring is a highly π deficient aromatic heterocycle
that can be used as the electron-withdrawing unit in push−pull
structures for intramolecular charge transfer (ICT). In general,
ICT along the scaffold of the molecule has a significant impact
on the luminescence properties and is also required for
nonlinear optical (NLO) processes. Moreover, a significant
decrease in the HOMO−LUMO energy band gap is observed
upon incorporation of pyrimidines in the backbone of π-
conjugated structures.2 Protonation, hydrogen bond formation,
and chelation of the nitrogen atoms of the pyrimidine ring are
also of great importance. Indeed, such derivatives have been
used in the formation of supramolecular assemblies3 and
sensors.4 In addition, it should be noted that the pyrimidine
ring is also an excellent building block for the synthesis of liquid
crystals;5 the combination of the optical and thermal
advantages that the pyrimidine provides can lead to completely
new applications. Pyrimidine fragments have recently been
incorporated into the scaffold of dyes for solar cells, either as π-
conjugated linkers between donor and acceptor groups6 or as
electron-accepting TiO2 anchoring groups.7
In a previous study11c we observed a strong enhancement of
the fluorescence intensity and the second-order NLO response
when comparing quinoxaline (benzopyrazine) and pyrazine
derivatives. Taking into account the fact that the pyrimidine
ring is better than the pyrazine ring in terms of second-order
NLO response, due to its higher electron-donating character,11c
it seemed of interest to study the photophysical properties of
quinazoline (benzopyrimidine) derivatives. Amazingly, this
heterocycle has rarely been used in materials chemistry.15
Only recently have Liu and co-workers described 2,4-diary-
4,6-Diarylpyrimidines and 2,4,6-triarylpyrimidines, when
judiciously substituted with an electron-donating group, are
Received: June 11, 2014
Published: July 15, 2014
© 2014 American Chemical Society
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c
Table 1. Synthesis of Arylvinylquinazolines by Aldol Condensation of Methylquinazolines with Aromatic Aldehydes
a
b
c
Unoptimized isolated yields. Obtained from 4d. Reagents and conditions: p-Ph2N-C6H4-B(OH)2, Pd(PPh3)4, Na2CO3, toluene/H2O/EtOH, Δ,
15 h.
lquinazoline derivatives that showed white photoluminescence
and electroluminescence through controllable acidic protona-
tion.16
The aim of the work described here was to synthesize a series
of amino-substituted π-conjugated quinazoline derivatives. The
photophysical properties, including solvatochromism and pH
sensitivity, are reported, and the results are compared with
those obtained for their pyrimidine counterparts.
iently, this synthetic protocol led to the selective formation of
E-configured vinylene bridges. The yields obtained were usually
moderate to good, although in certain cases they were poor due
to difficulties in the purification, in particular for 2,4-
diarylvinylpyrimidines 6a,b. Biphenyl derivative 4e was
obtained in good yield by a palladium-catalyzed Suzuki cross-
coupling reaction18 from the bromo derivative 4d. Never-
theless, the analogous 4-substituted compound 5e was prepared
directly by condensation of the corresponding biphenyl
aldehyde, taking into account that we were unable to obtain
4-(p-bromophenylvinyl)quinazoline (5d).
Different aryl- and arylethynylquinazolines could be accessed
starting from 4-chloroquinazoline (7) and 2,4-dichloroquinazo-
line (8) (Table 2). Whereas 4-arylquinazoline and 2,4-
diarylquinazoline derivatives 9 and 10 were obtained by Suzuki
cross-coupling reactions using Pd(PPh3)4 as catalyst, 4-
arylethynylquinazoline derivatives 11 and 12 were prepared
by copper/palladium-cocatalyzed Sonogashira reactions. It
should be noted that the π-electron-deficient character of the
quinazoline ring makes the oxidative addition of palladium to a
RESULTS AND DISCUSSION
■
Preparation of Substituted Quinazolines. Different
well-established methodologies were used for the preparation
of 2-, 4-, and 2,4-(di)substituted quinazolines. Thus,
arylvinylquinazoline (styrylquinazoline) derivatives could be
easily obtained from the corresponding methylquinazolines by
aldol condensation with the appropriate benzaldehyde in
boiling aqueous 5 M NaOH using Aliquat 336 as a phase-
transfer catalyst, according to the method initially described by
Vanden Eynde17 for methylpyrimidine (Table 1). Conven-
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Table 2. Synthesis of Aryl- and Arylethynylquinazolines by Catalyzed Cross-Coupling Reactions from Chloroquinazolines
a
b
c
Unoptimized isolated yields. Reagents and conditions: p-R-C6H4-B(OH)2, Pd(PPh3)4, Na2CO3, toluene/H2O/EtOH, Δ. Reagents and
conditions: p-R-C6H4-CCH, Pd(PPh3)2Cl2, CuI, Pri2NH, 70 °C, sealed tube, 15 h.
chloride−carbon bond easier without the use of specialized and
expensive ligands.19 Nevertheless, it was not possible to prepare
2,4-arylethynylquinazolines from 8. Even when 2.5 equiv of p-
dimethylphenylacetylene was used, the monosubstituted
compound 12 was the only product obtained. A similar
difference in reactivity between the 2- and 4-positions of the
pyrimidine ring has been reported, with the 2-position known
to be less reactive to oxidative addition of palladium than the 4-
position.8,20 Compound 12 was used as the starting material for
the synthesis of the differently disubstituted derivative 13,
which was obtained in excellent yield under standard Suzuki
conditions.
Table 3 (see also Figure 1 for spectra of compounds 5a, 9a, and
11a).
All compounds showed absorption maxima in the range λmax
370−433 nm (UV or visible region), usually accompanied by a
second band at higher energy. With respect to the fluorescence
features, typical emission maxima were obtained in the green
region. Moreover, the Stokes shifts are rather large, which is a
clear indication of the high polarizability of the π-conjugated
systems. It is well established that donor−acceptor function-
alized molecules can lead to ICT processes, and this would
explain the large Stokes shifts.
Both the absorption and emission maxima of 2-arylvinylqui-
nazolines 4 were found to be blue-shifted with respect to those
of 4-arylvinylquinazolines 5 with larger fluorescence quantum
yields and Stokes shifts. A similar trend was also observed for
pyrimidine derivatives.13,14 Nevertheless, in general, the
absorption and emission wavelengths of all the arylvinylquina-
zolines 4−6 are red-shifted in comparison with their previously
reported pyrimidine counterparts.11c,13
4-Arylquinazolines 9 exhibited the strongest fluorescence
response, with quantum yields of up to 0.93. On the other
hand, as expected, the absorption and emission of these
compounds are blue-shifted in comparison to those of the
phenylenevinylene analogues 4−5 due to the reduction in the
length of the π-conjugated backbone. 2,4-Disubstituted
quinazolines 6 and 10 presented absorption and emission
bands similar to those of the 4-substituted derivatives 5 and 9,
albeit with higher molar absorption coefficients. The
All of the new materials exhibited good solubility in a variety
of solvents, especially in THF and chlorinated solvents. The 1H
and 13C NMR and HRMS data were consistent with the
expected structures. As far as the arylvinylquinazolines 4−6 are
3
concerned, the J(H,H) coupling constants of ∼16 Hz for the
vinylic protons clearly support the selective formation of E-
configured double bonds. All compounds were perfectly stable
in the solid state and could be stored without special
precautions. However, it should be noted that some samples
underwent partial trans−cis isomerization when allowed to
stand in solution at room temperature for several days.
UV−Vis and Fluorescence Spectroscopy. The photo-
physical properties of several quinazoline derivatives were
examined by UV−vis and fluorescence spectroscopy in
dichloromethane (DCM) at 25 °C. The results are given in
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Supporting Information).21 This solvatochromic behavior,
which results from the stabilization of the highly polar emitting
state by polar solvents, is typical for compounds that exhibit an
internal charge transfer upon excitation and has been fully
documented with donor−acceptor fluorophores.22
Table 4 shows that 2-arylvinylquinazoline derivatives 4a,b
present a larger emission solvatochromism than the 4-
substituted compounds 5a,b. As expected, the biphenyl
derivatives 4e and 5e exhibit a more significant charge transfer
than their analogues with only one phenyl ring (4b and 5b).
Meanwhile, the 2,4-disubstituted derivative 6a shows an even
smaller fluorosolvatochromism than its 4-substituted analogue
Table 3. Optical Spectroscopy Data for Quinazoline
Derivatives
a
b
compd
λabs, nm (ε, mM−1 cm−1
)
λem, nm
ΦF
Stokes shift, cm−1
4a
4b
4c
255 (17.1), 395 (26.6)
300 (26.0), 400 (33.4)
256 (17.3), 385 (31.8)
308 (30.5), 382 (34.2)
433 (18.0)
536
520
545
544
548
571
558
610
545
557
490
528
530
534
560
565
551
0.21
0.61
0.21
0.65
0.07
0.25
0.12
0.23
0.02
0.09
0.93
0.80
0.30
0.34
0.03
0.41
0.06
6660
5769
7625
7796
4847
5797
5608
8482
5864
6085
5908
7102
8159
6474
6474
6455
6064
4e
5a
5b
5c
302 (21.8), 429 (16.9)
425 (24.9)
5e
309 (28.5), 402 (21.1)
413 (23.1)
6a
5a. Comparison of compounds 5a (Δλem = 97 nm, Δνem
=
3398 cm−1), 9a (Δλem = 122 nm, Δνem = 5337 cm−1), and 11a
(Δλem = 139 nm, Δνem = 5370 cm−1) shows that the aryl (9a)
and arylethynyl (11a) derivatives exhibit stronger internal
charge transfer than the arylvinyl derivative (5a). However, it is
worth noting that, according to the data reported previously by
some of us for arylvinylquinoxaline and arylvinylpyrimidine
derivatives,11c,13 a clear trend cannot be observed for each
substituent. Moreover, in contrast to the result that one might
expect, the fluorosolvatochromism is not always larger for
quinazoline derivatives.
6b
9a
299 (31.3), 416 (35.8)
264 (13.8), 380 (16.4)
293 (16.7), 384 (16.6)
341 (36.3), 370 (33.3)
296 (34.7), 384 (37.0)
282 (18.1), 411 (27.5)
295 (20.6), 414 (29.2)
269 (43.1), 413 (30.3)
9b
10a
10b
11a
11b
13
a
All spectra were recorded in DCM solutions at room temperature at c
= (1.0−6.0) × 10−5 M for absorption and c = (1.0−6.0) × 10−6 M for
emission. Fluorescence quantum yield ( 10%) determined relative to
b
It has been demonstrated previously that diazine derivatives
can function as colorimetric and luminescent pH sensors due to
the basic character of the nitrogen atoms of the hetero-
cycles.4b,10b,c,11c,13,16,23 The quinazolines described in this paper
were not an exception, as evidenced by the significant color
change experienced by their DCM solutions upon the addition
of TFA (Figure 4), a change that was fully reversible by
neutralization with base (Et3N or KButO).
quinine sulfate in 0.1 M H2SO4 (ΦF = 0.54) and 9,10-
diphenylanthracene in cyclohexane (ΦF = 0.90) as standards.
The changes observed in the UV−vis spectra of 4a upon
addition of acid are illustrated in Figure 5. The increase in the
concentration of TFA led to the progressive attenuation of the
absorption band for the neutral compound and the appearance
of a new, more intense red-shifted band corresponding to the
protonated species (see th eSupporting Information for spectra
of compounds 5a, 9a, and 11a). This bathochromic shift of the
absorption can be explained by an increased charge transfer
from the donors to the quinazoline moiety. Similarly to the
pyrimidine derivatives,11c,13 the electron-donating character of
the chain at position 2 increases the basicity of the heterocyclic
ring, which should be selectively protonated over the aromatic
amine. Nonetheless, although the nitrogen at position 3 is
initially the most basic center of the quinazoline unit, it is
difficult to predict which nitrogen atom is likely protonated (or
both). As far as the fluorescence response is concerned, the
emission is totally quenched after protonation, as is generally
observed for amino electron donor substituted diazines.11c
Even though these experiments were carried out in an organic
solvent (DCM), we recently showed that pyrimidine
chromophores can be incorporated into pluronic nanoparticles
and used as pH sensors in aqueous media.24
Figure 1. Normalized UV/vis (solid lines) and emission spectra
(dashed lines) of compounds 5a, 9a, and 11a.
fluorescence quantum yields, however, were appreciably lower.
The most red-shifted emission of the series corresponded to
arylethynyl derivatives 11.
In an effort to gain further insights into the photophysical
process within these push−pull molecules, the absorption and
emission behavior of the prepared compounds was studied in a
variety of different aprotic solvents. While the absorption
maxima were not significantly shifted, an increase in solvent
polarity led to bathochromic shifts of the emission maxima
along with a successive decrease in the fluorescence intensity
(Table 4). As an example, the spectra registered for compound
4a are shown in Figure 2, where the emission wavelength
maximum at λem 443 nm in the least polar solvent
(cyclohexane) is red-shifted by about Δλem = 151 nm (Δνem
5738 cm−1) on using DMSO as solvent (λem 594 nm). The
change in the emission color can be easily seen by the naked
eye, as shown in Figure 3 for compounds 4e, 9b, and 10b. In
general, a strong solvatochromism effect can be observed for
the emission features, with a regular trend according to the
ET(30) Dimroth−Reichardt polarity parameters (see the
CONCLUSIONS
■
In summary, we have successfully synthesized and characterized
a series of push−pull quinazoline derivatives by different, well-
established, and straightforward methodologies. Arylvinylqui-
nazolines were prepared by aldol condensation of the
appropriate methylquinazoline and aromatic aldehyde, while
aryl- and arylethynylquinazolines were accessed by catalyzed
cross-coupling reactions from the corresponding chloroquina-
zoline. All of the molecules displayed optical features that were
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Table 4. Emission Solvatochromism of Quinazoline Derivatives in Various Aprotic Solvents
λem, nm
a
a
a
a
a
b
cyclohexane, ET(30) = 30.9 THF, ET(30) = 37.4 DCM, ΔET(30) = 40.7 acetonitrile, ΔET(30) = 45.6 DMSO, ΔET(30) = 45.1 Δνem
,
cm−1
4a
443
520
498
522
516
537
540
540
572
540
483
508
528
518
540
535
549
536
520
545
544
548
571
558
610
545
490
528
530
534
560
565
551
582
543
592
579
572
598
579
642
570
529
559
571
565
573
610
570
594
547
600
585
585
600
589
641
580
543
563
575
568
583
616
584
5738
3990
5408
4884
3398
3700
3224
4808
2639
5337
4710
5544
4765
5370
5841
5501
4b
4c
449
453
4e
455
5a
465, 488
463, 491
480, 495
461, 490
503
5b
5c
5e
6a
9a
421
9b
10a
10b
11a
11b
13
445
436
447
444
433, 453 (sh)
423, 442
a
b
Dimroth−Reichardt polarity parameter, in kcal mol−1. Δνem = ν(cyclohexane) − ν(DMSO).
Figure 4. Color change of DCM solutions of several quinazoline
derivatives in the presence of TFA.
Figure 2. Normalized emission of compound 4a in different aprotic
solvents.
Figure 5. Changes in the absorption of 4a (c = 4.1 × 10−5 M in DCM)
with increasing concentration of TFA.
nonpolar solvents, a finding that supports the formation of very
polar excited ICT states when terminal electron-donating
groups are present in the molecule and suggests the potential of
the quinazoline structures for NLO studies. Moreover, as one
would expect, the materials underwent a dramatic and
reversible color change upon addition of acid as a result of
the protonation of the nitrogen atoms of the quinazoline ring.
This phenomenon should enable the development of
colorimetric pH sensors after suitable design of the molecules.
Figure 3. Fluorescence color changes experienced by 4e, 9b, and 10b
in various solvents. Squares are trimmed parts of photographs taken in
the dark upon irradiation with a hand-held UV lamp (λem 366 nm).
similar to those of their pyrimidine counterparts. In general,
absorption wavelengths were located in the UV or visible
region, with typical emission maxima in the green region that
led to large Stokes shifts. In particular, the arylquinazoline
derivatives exhibited high fluorescence quantum yields. Strong
emission solvatochromism was also observed in a variety of
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127.2 (CH), 123.4 (C), 123.1 (C). HRMS (ESI/ASAP, TOF): m/z
calculated for C16H12N279Br [M + H]+ 311.0184, found 311.0179.
(E)-2-[4-(4-Diphenylaminophenyl)styryl]quinazoline (4e). A
stirred mixture of 4d (41 mg, 0.13 mmol), 4-diphenylaminophenylbor-
onic acid (58 mg, 0.20 mmol), and Pd(PPh3)4 (15 mg, 0.013 mmol) in
degassed aqueous 1 M sodium carbonate (0.5 mmol, 0.5 mL)/ethanol
(0.5 mL)/toluene (5 mL) was heated under reflux for 15 h under a
nitrogen atmosphere. The reaction mixture was cooled and filtered,
and EtAcO/water 1/1 (20 mL) was added. The organic layer was
separated, and the aqueous layer was extracted with additional EtAcO
(2 × 10 mL). The combined organic extracts were dried over MgSO4,
and the solvents were evaporated under reduced pressure. The crude
product was purified by column chromatography (SiO2, petroleum
ether/EtAcO, 1/1). Orange solid. Yield: 85% (52 mg). Mp: 221−222
EXPERIMENTAL SECTION
■
General Considerations. 4-Chloroquinazoline and 2,4-dichlor-
oquinazoline were purchased from Interchim. 2-Methylquinazoline (1)
was obtained from 2-bromobenzaldehyde and acetamidine hydro-
chloride as described previously.25 4-Methylquinazoline (2) and 2,4-
dimethylquinazoline (3) were obtained from the corresponding chloro
derivatives according to a reported procedure.26 For air- and moisture-
sensitive reactions, all glassware was flame-dried and cooled under
nitrogen. NMR spectra were acquired at room temperature. Chemical
shifts are given in parts per million relative to TMS (1H, 0.0 ppm) and
CDCl3 (13C, 77.0 ppm). Acidic impurities in CDCl3 were removed by
treatment with anhydrous K2CO3. UV−vis and fluorescence spectra
were recorded using standard 1 cm quartz cells. Compounds were
excited at their absorption maxima (band of lowest energy) to record
the emission spectra. The ΦF values were calculated using a well-
known procedure with two different standards: quinine sulfate in 0.1
M H2SO4 and 9,10-diphenylanthracene in cyclohexane.27 Stokes shifts
were calculated by considering the lowest energetic absorption band.
General Procedure for the Synthesis of Arylvinylquinazo-
lines (Styrylquinazolines). A stirred mixture of the corresponding
methylquinazoline (0.5 mmol) and the appropriate aldehyde (0.5
mmol, 1 mmol for 2,4-dimethylquinazoline) in aqueous sodium
hydroxide (5 M, 10 mL) containing Aliquat 336 (22 mg, 0.05 mmol)
was heated under reflux for 2 h. The mixture was cooled. The
precipitate was filtered off, washed with water, and purified by column
chromatography.
1
°C. H NMR (300 MHz, CDCl3): δ 7.08−7.03 (m, 2H), 7.17−7.14
(m, 6H), 7.43−7.29 (m, 4H), 7.45 (d, 1H, J = 15.9 Hz), 7.50 (d, 2H, J
= 8.7 Hz) 7.66−7.60 (m, 3H), 7.74 (d, 2H, J = 8.1 Hz), 7.93−7.88 (m,
2H), 8.02 (d, 1H, J = 9.0 Hz), 8.20 (d, 1H, J = 15.9 Hz), 9.40 (s, 1H).
13C NMR and JMOD (75 MHz, CDCl3): δ 161.4 (C), 160.2 (CH),
150.7 (C), 147.6 (C), 147.5 (C), 141.2 (C), 138.2 (CH), 134.7 (C),
134.23 (CH), 134.15 (C), 129.3 (CH), 128.2 (CH), 128.1 (CH),
127.6 (2 × CH), 127.2 (CH), 127.1 (CH), 126.9 (CH), 124.6 (CH),
123.7 (C), 123.4 (C), 123.1 (CH). HRMS (ESI/ASAP, TOF): m/z
calculated for C34H26N3 [M + H]+ 476.2127, found 476.2130.
(E)-4-(4-Dimethylaminostyryl)quinazoline (5a). Purified by
column chromatography (SiO2, petroleum ether/EtAcO, 1/1). Orange
1
solid. Yield: 88% (120 mg). Mp: 139−140 °C. H NMR (300 MHz,
(E)-2-(4-Dimethylaminostyryl)quinazoline (4a). Purified by
column chromatography (SiO2, petroleum ether/EtAcO, 1/1). Yellow
solid. Yield: 74% (101 mg). Mp: 142−143 °C. H NMR (300 MHz,
CDCl3): δ 3.03 (s, 6H), 6.72 (d, 2H, J = 8.7 Hz), 7.63−7.59 (m, 3H),
7.68 (d, 1H, J = 15.3 Hz), 7.84 (dt, 1H J1 = 8.1 Hz, J2 = 1.2 Hz), 7.98
(d, 1H, J = 8.4 Hz), 8.24 (d, 1H, J = 15.9 Hz), 8.29 (d, 1H, J = 8.4
Hz), 9.20 (s, 1H). 13C NMR and JMOD (75 MHz, CDCl3): δ 162.8
(C), 154.8 (CH), 151.5 (C), 150.9 (C), 140.5 (CH), 133.2 (CH),
129.8 (CH), 128.8 (CH), 127.0 (CH), 124.0 (CH), 123.8 (C), 123.0
(C), 114.9 (CH), 112.0 (CH), 40.2 (CH3). HRMS (ESI/ASAP,
TOF): m/z calculated for C18H18N3 [M + H]+ 276.1501, found
276.1500.
1
CDCl3): δ 3.02 (s, 6H), 6.73 (d, 2H, J = 8.7 Hz), 7.21 (d, 1H, J = 15.6
Hz), 7.59−7.53 (m, 3H), 7.86−7.82 (m, 2H), 7.94 (d, 1H, J = 8.7 Hz),
8.09 (d, 1H, J = 15.9 Hz), 9.32 (s, 1H). 13C NMR and JMOD (75
MHz, CDCl3): δ 162.2 (C), 160.1 (CH), 151.1 (C), 150.8 (C), 139.1
(CH), 134.0 (CH), 129.2 (CH), 127.9 (CH), 127.2 (CH), 126.5
(CH), 124.3 (C), 123.12 (C), 123.06 (CH), 112.1 (CH), 40.3 (CH3).
HRMS (ESI/ASAP, TOF): m/z calculated for C18H18N3 [M + H]+
276.1501, found 276.1501.
(E)-4-(4-Diphenylaminostyryl)quinazoline (5b). Purified by
column chromatography (SiO2, petroleum ether/EtAcO, 7/3). Orange
1
solid. Yield: 35% (69 mg). Mp: 118−119 °C. H NMR (300 MHz,
(E)-2-(4-Diphenylaminostyryl)quinazoline (4b). Purified by
column chromatography (SiO2, petroleum ether/EtAcO, 7/3). Yellow
solid. Yield: 71% (141 mg). Mp: 154−155 °C. H NMR (300 MHz,
CDCl3): δ 7.12−7.06 (m, 4H), 7.17−7.13 (m, 4H), 7.35−7.28 (m,
4H), 7.58 (d, 2H, J = 8.7 Hz), 7.67−7.62 (m, 1H), 7.78 (d, 1H, J =
15.3 Hz), 7.90−7.85 (m, 1H), 8.02 (d, 1H, J = 8.4 Hz), 8.24 (d, 1H, J
= 15.3 Hz), 8.29 (d, 1H, J = 8.4 Hz), 9.24 (s, 1H). 13C NMR and
JMOD (75 MHz, CDCl3): δ 162.4 (C), 154.8 (CH), 151.1 (C), 149.5
(C), 147.0 (C), 139.5 (CH), 133.4 (CH), 129.5 (CH), 129.2 (CH),
129.1 (C), 129.0 (CH), 127.3 (CH), 125.3 (CH), 124.2 (CH), 123.9
(CH), 123.0 (C), 122.0 (CH), 117.8 (CH). HRMS (ESI/ASAP,
TOF): m/z calculated for C28H22N3 [M + H]+ 400.1813, found
400.1818.
1
CDCl3): δ 7.06−7.03 (m, 4H), 7.13−7.10 (m, 4H), 7.29−7.23 (m,
5H), 7.55−7.50 (m, 3H), 7.85−7.81 (m, 2H), 7.94 (d, 1H, J = 8.7
Hz), 8.09 (d, 1H, J = 15.9 Hz), 9.32 (s, 1H). 13C NMR and JMOD (75
MHz, CDCl3): δ 161.7 (C), 160.2 (CH), 150.7 (C), 148.8 (C), 147.3
(C), 138.2 (CH), 134.2 (CH), 129.7 (C), 129.4 (CH), 128.7 (CH),
128.0 (CH), 127.2 (CH), 126.9 (CH), 125.7 (CH), 125.1 (CH),
123.6 (CH), 123.2 (C), 122.5 (CH). HRMS (ESI/ASAP, TOF): m/z
calculated for C28H22N3 [M + H]+ 400.1813, found 400.1820.
(E)-2-(4-Piperidin-1-ylstyryl)quinazoline (4c). Purified by col-
umn chromatography (SiO2, petroleum ether/EtAcO, 7/3). Yellow
(E)-4-(4-Piperidin-1-ylstyryl)quinazoline (5c). Purified by col-
umn chromatography (SiO2, petroleum ether/EtAcO, 7/3). Yellow
1
solid. Yield: 53% (83 mg). Mp: 96−100 °C. H NMR (300 MHz,
1
solid. Yield: 53% (83 mg). Mp: 154−155 °C. H NMR (300 MHz,
CDCl3): δ 1.70−1.63 (m, 6H), 3.33−3.29 (m, 4H), 6.94 (d, 2H, J =
8.7 Hz), 7.66−7.61 (m, 3H), 7.74 (d, 1H, J = 15.9 Hz), 7.87 (dt, 1H J1
= 8.1 Hz, J2 = 1.2 Hz), 8.00 (d, 1H, J = 8.4 Hz), 8.24 (d, 1H, J = 15.9
Hz), 8.31 (d, 1H, J = 8.4 Hz), 9.21 (s, 1H). 13C NMR and JMOD (75
MHz, CDCl3): δ 162.7 (C), 154.9 (CH), 152.8 (C), 151.0 (C), 140.1
(CH), 133.3 (CH), 129.7 (CH), 128.9 (CH), 127.1 (CH), 126.4 (C),
124.0 (CH), 123.0 (C), 116.0 (CH), 115.1 (CH), 49.3 (CH2), 25.5
(CH2), 24.3 (CH2). HRMS (ESI/ASAP, TOF): m/z calculated for
C21H22N3 [M + H]+ 316.1814, found 316.1815.
CDCl3): δ 1.72−1.66 (m, 6H), 3.31−3.27 (m, 4H), 6.95 (d, 2H, J =
9.0 Hz), 7.25 (d, 1H, J = 15.9 Hz), 7.60−7.54 (m, 3H), 7.90−7.85 (m,
2H), 7.97 (d, 1H, J = 8.7 Hz), 8.11 (d, 1H, J = 15.9 Hz), 9.36 (s, 1H).
13C NMR and JMOD (75 MHz, CDCl3): δ 162.0 (C), 160.1 (CH),
152.4 (C), 150.8 (C), 138.8 (CH), 134.1 (CH), 129.0 (CH), 127.9
(CH), 127.2 (CH), 126.6 (CH), 126.2 (C), 124.1 (CH), 123.2 (C),
115.4 (CH), 49.6 (CH2), 25.6 (CH2), 24.4 (CH2). HRMS (ESI/
ASAP, TOF): m/z calculated for C21H22N3 [M + H]+ 316.1814, found
316.1819.
(E)-4-[4-(4-Diphenylaminophenyl)styryl]quinazoline (5e).
(E)-2-(4-Bromostyryl)quinazoline (4d). Purified by column
chromatography (SiO2, petroleum ether/EtAcO, 7/3). Colorless
solid. Yield: 61% (95 mg). Mp: 179−180 °C. H NMR (300 MHz,
CDCl3): δ 7.40 (d, 1H, J = 15.9 Hz), 7.54 (s, 4H), 7.64−7.59 (m, 1H),
7.93−7.88 (m, 2H), 8.01 (d, 1H, J = 9.0 Hz), 8.09 (d, 1H, J = 15.9
Hz), 9.38 (s, 1H). 13C NMR and JMOD (75 MHz, CDCl3): δ 161.0
(C), 160.3 (CH), 150.6 (C), 137.2 (CH), 135.2 (C), 134.3 (CH),
132.0 (CH), 129.1 (CH), 128.6 (CH), 128.2 (CH), 127.3 (CH),
Purified by column chromatography (SiO2, petroleum Ether/EtAcO,
1
1/1). Yellow solid. Yield: 23% (55 mg). Mp: 151−154 °C. H NMR
1
(300 MHz, CDCl3): δ 7.08−7.03 (m, 2H), 7.17−7.12 (m, 6H), 7.31−
7.24 (m, 4H), 7.53 (d, 2H, J = 8.7 Hz,), 7.70−7.65 (m, 3H), 7.79 (d,
2H, J = 8.7 Hz), 7.93−7.88 (m, 1H), 7.96 (d, 1H, J = 15.9 Hz), 8.06
(d, 1H, J = 8.1 Hz), 8.33 (d, 1H, J = 15.9 Hz), 8.35 (d, 1H, J = 8.1
Hz), 9.30 (s, 1H). 13C NMR and JMOD (75 MHz, CDCl3): δ 162.1
(C), 154.8 (CH), 151.1 (C), 147.8 (C), 147.5 (C), 142.0 (C), 139.5
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1
(CH), 134.3 (C), 133.8 (C), 133.6 (CH), 129.3 (CH), 129.2 (CH),
128.6 (CH), 127.7 (CH), 127.5 (CH), 127.0 (CH), 124.7 (CH),
124.5 (CH), 123.6 (CH), 123.2 (CH), 123.1 (C), 119.9 (CH). HRMS
(ESI/ASAP, TOF): m/z calculated for C34H26N3 [M + H]+ 476.2127,
found 476.2125.
1). Yellow solid. Yield: 51% (93 mg). Mp: 169−170 °C. H NMR
(300 MHz, CDCl3): δ 3.06 (s, 6H), 3.09 (s, 6H), 6.82 (d, 2H, J = 9.0
Hz), 6.88 (d, 2H, J = 9.0 Hz), 7.43 (dt, 1H, J1 = 7.2 Hz, J2 = 0.9 Hz),
7.78 (dt, 1H, J1 = 7.2 Hz, J2 = 0.9 Hz), 7.89 (d, 2H, J = 8.7 Hz), 8.02
(d, 1H, J = 8.4 Hz), 8.19 (d, 1H, J = 8.4 Hz), 8.59 (d, 2H, J = 9.0 Hz).
13C NMR and JMOD (75 MHz, CDCl3): δ 167.5 (C), 160.5 (C),
(E,E)-2,4-Bis(4-dimethylaminostyryl)quinazoline (6a). Purified
by column chromatography (SiO2, petroleum ether/EtAcO, 1/1).
Orange solid. Yield: 31% (65 mg). Mp: 110−112 °C. H NMR (300
152.4 (C), 152.0 (C), 151.7 (C), 132.8 (CH), 131.7 (CH), 129.9
(CH), 128.6 (CH), 127.3 (CH), 126.5 (C), 125.7 (C), 125.3 (CH),
121.2 (C), 111.73 (CH), 111.70 (CH), 40.3 (2 × CH3). HRMS (ESI/
ASAP, TOF): m/z calculated for C24H25N4 [M + H]+ 369.2079, found
369.2077.
1
MHz, CDCl3): δ 3.05 (s, 6H), 3.08 (s, 6H), 6.77 (d, 2H, J = 8.7 Hz),
6.78 (d, 2H, J = 8.7 Hz), 7.25 (d, 1H, J = 15.9 Hz), 7.55 (dt,1H, J1 =
8.1 Hz, J2 = 1.2 Hz), 7.65 (d, 2H, J = 8.7 Hz), 7.70 (d, 2H, J = 8.7 Hz),
7.78 (d, 1H, J = 15.9 Hz), 7.81 (dt,1H, J1 = 8.1 Hz, J2 = 1.2 Hz), 7.94
(d, 1H, J = 8.4 Hz), 8.20 (d, 1H, J = 15.9 Hz), 8.26 (d, 1H, J = 8.4
Hz), 8.33 (d, 1H, J = 15.9 Hz). 13C NMR and JMOD (75 MHz,
CDCl3): δ 162.3 (C), 161.3 (C), 151.8 (C), 151.4 (C), 150.9 (C),
139.8 (CH), 138.2 (CH), 133.1 (CH), 129.7 (CH), 129.0 (CH),
128.4 (CH), 125.7 (CH), 124.9 (C), 124.3 (C), 124.2 (CH), 124.0
(CH), 121.3 (C), 115.8 (CH), 112.2 (CH), 112.0 (CH), 40.3 (CH3),
40.2 (CH3). HRMS (ESI/ASAP, TOF): m/z calculated for C28H29N4
[M + H]+ 421.2392, found 421.2390.
(E,E)-2,4-Bis(4-diphenylaminophenyl)quinazoline (10b). Pu-
rified by column chromatography (SiO2, petroleum ether/EtAcO, 7/
3) followed by crystallization from DCM/n-heptane. Yellow solid.
Yield: 36% (110 mg). Mp: 84−88 °C. 1H NMR (300 MHz, CDCl3): δ
7.11−7.05 (m, 4H), 7.23−7.16 (m, 12H), 7.36−7.29 (m, 8H), 7.41
(dt, 1H, J1 = 7.2 Hz, J2 = 0.9 Hz), 7.71 (d, 2H, J = 8.7 Hz), 7.74 (dt,
1H, J1 = 7.2 Hz, J2 = 0.9 Hz), 7.99(d, 1H, J = 8.4 Hz), 8.12 (d, 1H, J =
8.4 Hz), 8.42 (d, 2H, J = 8.7 Hz). 13C NMR and JMOD (75 MHz,
CDCl3): δ 167.4 (C), 160.1 (C), 152.3 (C), 149.9 (C), 149.7 (C),
147.4 (C), 147.2 (C), 133.3 (CH), 132.0 (C), 131.4 (CH), 130.8 (C),
129.7 (CH), 129.5 (CH), 129.3 (CH), 129.0 (CH), 127.1 (CH),
126.3 (CH), 125.3 (CH), 125.0 (CH), 123.8 (CH), 123.4 (CH),
122.5 (CH), 121.9 (CH), 121.3 (C). HRMS (ESI/ASAP, TOF): m/z
calculated for C44H33N4 [M + H]+ 617.2700, found 617.2700.
General Procedure for the Synthesis of Arylethynylquinazo-
lines. A suspension of the corresponding chloroquinazoline (1.0
mmol), [Pd(PPh3)2Cl2] (70 mg, 0.1 mmol), and CuI (10 mg 0.05
mol) in diisopropylamine (10 mL) was degassed three times in a
pressure tube. The acetylene derivative (1.2 mmol) was then added.
The mixture was heated at 70 °C for 15 h and then filtered, and the
residue was washed with DCM. The filtrate was washed with saturated
aqueous ammonium chloride (2 × 25 mL) and water (2 × 25 mL) and
dried over anhydrous MgSO4. The solvent was removed under
reduced pressure.
(E,E)-2,4-Bis(4-diphenylaminostyryl)quinazoline (6b). Purified
by column chromatography (SiO2, petroleum ether/EtAcO, 7/3).
1
Yellow solid. Yield: 16% (54 mg). Mp: 124−125 °C. H NMR (300
MHz, CDCl3): δ 7.18−7.06 (m, 16H), 7.34−7.28 (m, 8H), 7.51−7.69
(m, 6H), 7.78 (d, 1H, J = 15.9 Hz), 7.82 (dt,1H, J1 = 8.1 Hz, J2 = 1.2
Hz), 7.95 (d, 1H, J = 8.4 Hz), 8.17 (d, 1H, J = 15.9 Hz), 8.23 (d, 1H, J
= 8.4 Hz), 8.32 (d, 1H, J = 15.9 Hz). 13C NMR and JMOD (75 MHz,
CDCl3): δ 162.0 (C), 160.8 (C), 151.8 (C), 149.3 (C), 148.5 (C),
147.4 (C), 147.1 (C), 139.1 (CH), 137.5 (CH), 131.3 (CH), 130.2
(C), 129.7 (CH), 129.5 (CH), 129.4 (CH), 129.1 (CH), 128.6 (CH),
126.3 (CH), 125.2 (CH), 125.1 (CH), 125.0 (CH), 123.8 (CH),
123.4 (CH), 122.7 (CH), 122.2 (CH), 121.5 (C), 119.4 (CH), 118.5
(CH). HRMS (ESI/ASAP, TOF): m/z calculated for C48H37N4 [M +
H]+ 669.3013, found 669.3011.
General Procedure for the Synthesis of Arylquinazolines. A
stirred mixture of the corresponding chloroquinazoline (0.5 mmol),
the appropriate arylboronic acid (1 mmol, 1.5 mmol for 2,4-
dichloroquinazoline), and Pd(PPh3)4 (0.005 mmol) in degassed
aqueous 2 M sodium carbonate (2 mmol, 1 mL)/ethanol (1 mL)/
toluene (15 mL) was heated under reflux for 24 h under a nitrogen
atmosphere (48 h for 2,4-dichloroquinazoline). The reaction mixture
was cooled and filtered, and EtAcO/water 1/1 (20 mL) was added.
The organic layer was separated and the aqueous layer extracted with
additional EtAcO (2 × 10 mL). The combined organic extracts were
dried over MgSO4 and the solvents evaporated under reduced
pressure.
4-(4-Dimethylaminophenylethynyl)quinazoline (11a). Puri-
fied by column chromatography (SiO2, petroleum ether/EtAcO, 1/1).
Orange solid. Yield: 68% (185 mg). Mp: 115−116 °C. 1H NMR (300
MHz, CDCl3): δ 3.05 (s, 6H), 6.69 (d, 2H, J = 8.7 Hz), 7.63 (d, 2H, J
= 8.7 Hz), 7.69 (dt, 1H J1 = 8.1 Hz, J2 = 1.2 Hz), 7.90 (dt, 1H J1 = 8.1
Hz, J2 = 1.2 Hz), 8.02 (d, 1H, J = 8.4 Hz), 8.41 (d, 1H, J = 8.4 Hz),
9.24 (s, 1H). 13C NMR and JMOD (75 MHz, CDCl3): δ 155.1 (CH),
153.3 (C), 151.4 (C), 150.0 (C), 134.3 (CH), 134.0 (CH), 128.6
(CH), 127.9 (CH), 126.7 (CH), 125.2 (C), 111.7 (CH), 107.1 (C),
102.4 (C), 85.0 (C), 40.1 (CH3). HRMS (ESI/ASAP, TOF): m/z
calculated for C18H16N3 [M + H]+ 274.1339, found 274.1341.
4-(4-Diphenylaminophenylethynyl)quinazoline (11b). Puri-
fied by column chromatography (SiO2, petroleum ether/EtAcO, 7/3).
(E)-4-(4-Dimethylaminophenyl)quinazoline (9a). Purified by
column chromatography (SiO2, petroleum ether/EtAcO, 1/1). Yellow
1
1
solid. Yield: 75% (93 mg). Mp: 114−115 °C. H NMR (300 MHz,
Yellow solid. Yield: 76% (302 mg). Mp: 155−156 °C. H NMR (300
CDCl3): δ 2.99 (s, 6H), 6.76 (d, 2H, J = 8.7 Hz), 7.51−7.46 (m, 1H),
7.70 (d, 2H, J = 8.7 Hz), 7.77 (dt, 1H, J1 = 8.1 Hz, J2 = 1.2 Hz), 7.97
(d, 1H, J = 8.1 Hz), 8.18 (d, 1H, J = 8.1 Hz), 9.20 (s, 1H). 13C NMR
and JMOD (75 MHz, CDCl3): δ 168.0 (C), 154.7 (CH), 151.8 (C),
151.2 (C), 133.1 (CH), 131.7 (CH), 128.7 (CH), 127.5 (CH), 127.1
(CH), 124.5 (C), 123.1 (C), 111.7 (CH), 40.2 (CH3). HRMS (ESI/
ASAP, TOF): m/z calculated for C16H15N3Na [M + Na]+ 272.1164,
found 272.1163.
MHz, CDCl3): δ 7.05−7.03 (m, 2H), 7.18−7.10 (m, 6H), 7.34−7.29
(m, 4H), 7.57 (d, 2H, J = 8.7 Hz), 7.69 (dt, 1H J1 = 8.1 Hz, J2 = 1.2
Hz), 7.91 (dt, 1H J1 = 8.1 Hz, J2 = 1.2 Hz), 8.03 (d, 1H, J = 8.4 Hz),
8.39 (d, 1H, J = 8.4 Hz), 9.28 (s, 1H). 13C NMR and JMOD (75 MHz,
CDCl3): δ 155.0 (CH), 152.9 (C), 150.1 (C), 149.9 (C), 146.6 (C),
134.2 (CH), 133.8 (CH), 129.6 (CH), 128.7 (CH), 128.1 (CH),
126.6 (CH), 125.7 (CH), 125.3 (C), 124.4 (CH), 120.9 (CH), 112.7
(C), 100.4 (C), 85.2 (C). HRMS (ESI/ASAP, TOF): m/z calculated
for C28H20N3 [M + H]+ 398.1642, found 398.1644.
2-Chloro-4-(4-dimethylaminophenylethynyl)quinazoline
(12). Purified by column chromatography (SiO2, petroleum ether/
EtAcO, 7/3) followed by crystallization from DCM/n-heptane.
Orange solid. Yield: 70% (215 mg). Mp: 198−199 °C. 1H NMR
(300 MHz, CDCl3): δ 3.08 (s, 6H), 6.70 (d, 2H, J = 8.7 Hz), 7.63 (d,
2H, J = 8.7 Hz), 7.70 (dt, 1H J1 = 8.1 Hz, J2 = 1.2 Hz), 7.94−7.92 (m,
2H), 8.39 (d, 1H, J = 8.4 Hz). 13C NMR and JMOD (75 MHz,
CDCl3): δ 157.2 (C), 155.7 (C), 151.75 (C), 151.69 (C), 135.0 (CH),
134.7 (CH), 128.1 (CH), 127.8 (CH), 127.0 (CH), 123.6 (C), 111.6
(CH), 106.4 (C), 105.2 (C), 85.0 (C), 40.0 (CH3). HRMS (ESI/
ASAP, TOF): m/z calculated for C18H1535ClN3 [M + H]+ 308.0954,
found 308.0950.
(E)-4-(4-Diphenylaminophenyl)quinazoline (9b). Purified by
column chromatography (SiO2, petroleum ether/EtAcO, 7/3). Yellow
1
solid. Yield: 81% (151 mg). Mp: 141−142 °C. H NMR (300 MHz,
CDCl3): δ 7.13−7.08 (m, 2H), 7.29−7.19 (m, 6H), 7.35−7.29 (m,
4H), 7.61 (dt, 1H, J1 = 8.1 Hz, J2 = 1.2 Hz), 7.70 (d, 2H, J = 8.7 Hz),
7.90 (dt, 1H, J1 = 8.1 Hz, J2 = 1.2 Hz), 8.10 (d, 1H, J = 8.1 Hz), 8.26
(d, 1H, J = 8.1 Hz), 9.32 (s, 1H). 13C NMR and JMOD (75 MHz,
CDCl3): δ 168.0 (C), 154.7 (CH), 151.8 (C), 151.2 (C), 133.1 (CH),
131.7 (CH), 128.7 (CH), 127.5 (CH), 127.1 (CH), 124.5 (C), 123.1
(C), 111.7 (CH), 40.2 (CH3). HRMS (ESI/ASAP, TOF): m/z
calculated for C26H20N3 [M + H]+ 374.1657, found 374.1658.
(E,E)-2,4-Bis(4-dimethylaminophenyl)quinazoline (10a). Pu-
rified by column chromatography (SiO2, petroleum ether/EtAcO, 1/
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4-(4-Dimethylaminophenylethynyl)-2-phenylquinazoline
(13). Obtained according to the general procedure described above for
the synthesis of arylquinazolines. Purified by column chromatography
(SiO2, petroleum ether/EtAcO, 7/3). Yellow solid. Yield: 93% (162
mg). Mp: 144−145 °C. 1H NMR (300 MHz, CDCl3): δ 3.06 (s, 6H),
6.72 (d, 2H, J = 8.7 Hz), 7.54−7.51 (m, 3H), 7.68−7.63 (m, 3H), 7.88
(dt, 1H J1 = 8.1 Hz, J2 = 1.2 Hz), 8.07 (d, 1H, J = 8.4 Hz), 8.41 (d, 1H,
J = 8.4 Hz), 8.64 (d, 2H, J = 8.1 Hz). 13C NMR and JMOD (75 MHz,
CDCl3): δ 160.9 (C), 153.6 (C), 151.3 (C), 150.8 (C), 138.1 (C),
134.2 (CH), 133.9 (CH), 130.4 (CH), 128.9 (CH), 128.7 (CH),
128.5 (CH), 127.3 (CH), 126.7 (CH), 123.8 (C), 111.7 (CH), 107.5
(C), 101.3 (C), 85.3 (C), 40.1 (CH3). HRMS (ESI/ASAP, TOF): m/
z calculated for C24H20N3 [M + H]+ 350.1652, found 350.1656.
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ASSOCIATED CONTENT
* Supporting Information
́
Bredas, J.-L. J. Phys. Chem. B 2002, 106, 6442−6450.
■
(11) (a) Castet, F.; Pic, A.; Champagne, B. Dyes Pigm. 2014, 110,
256−260. (b) Achelle, S.; Kahlal, S.; Saillard, J.-Y.; Cabon, N.; Caro,
B.; Robin-le Guen, F. Tetrahedron 2014, 70, 2804−2815. (c) Achelle,
S.; Barsella, A.; Baudequin, C.; Caro, B.; Robin-le Guen, F. J. Org.
Chem. 2012, 77, 4087−4096. (d) Akdas-Kilig, H.; Roisnel, T.; Ledoux,
I.; Le Bozec, H. New J. Chem. 2009, 33, 1470−1473.
S
Figures giving 1H NMR and 13C NMR spectra for all
compounds, plots of emission maxima versus ET(30), and
changes in the absorption spectra of 5a, 9a, and 11a with
increasing concentrations of TFA. This material is available free
of charge via the Internet at http://pubs.acs.org.
(12) See for example: (a) Savel, P.; Akdas-Kilig, H.; Malval, J.-P.;
Spangenberg, A.; Roisnel, T.; Fillaut, J.-L. J. Mater. Chem. C 2014, 2,
295−305. (b) Achelle, S.; Malval, J.-P.; Aloise, S.; Barsella, A.;
Spangenberg, A.; Mager, L.; Akdas-Kilig, H.; Fillaut, J.-L.; Caro, B.;
Robin-le Guen, F. ChemPhysChem 2013, 14, 2725−2736. (c) Wang,
A.; Long, L.; Meng, S.; Li, X.; Zhao, W.; Song, Y.; Cifuentes, M. P.;
Humphrey, M. G.; Zhang, C. Org. Biomol. Chem. 2013, 11, 4250−
4257. (d) Chen, D.; Zhong, C.; Dong, X.; Liu, Z.; Qin, J. J. Mater.
Chem. 2012, 22, 4343−4348. (e) Li, L.; Ge, J.; Wu, H.; Xu, Q.-H.; Yao,
S. Q. J. Am. Chem. Soc. 2012, 134, 12157−12167.
AUTHOR INFORMATION
Corresponding Authors
*E-mail for S.A.: sylvain.achelle@univ-rennes1.fr.
*E-mail for J.R.-L.: julian.rodriguez@uclm.es.
Notes
■
The authors declare no competing financial interest.
(13) Achelle, S.; Robin-le Guen, F. Tetrahedron Lett. 2013, 54, 4491−
4496.
ACKNOWLEDGMENTS
■
We thank Julien Pelle
́
and Mael L’Hostis for some preliminary
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