Synthesis and fluorescence of 6-(4-detiethylaminophenyl)-and 6-[2-(4-N,N-disubstituted aminophenyl)vinyl]-4-methylthio-2-oxo-2h-pyran-3-carbonitriles in solution and in the solid states

Article abstract of DOI:10.3987/COM-06-10741

Fluorescent dyes, 6(4-dimethylaminophenyl)-4-methylthio- and 6-[2-(4-N,N-disubstituted aminophenyl)vinyl]-4-methylthio-2-oxo-2H-pyran-3-carbonitriles (3a-d) were synthesized by the reaction of 4-dimethylaminoacetophenone (1a) and 4-aminobenzalacetone deri

Full text of DOI:10.3987/COM-06-10741

HETEROCYCLES, Vol. 68, No. 6, 2006
1105
HETEROCYCLES, Vol. 68, No. 6, 2006, pp. 1105 - 1108. © The Japan Institute of Heterocyclic Chemistry
Received, 17th March, 2006, Accepted, 25th April, 2006, Published online, 28th April, 2006. COM-06-10741
SYNTHESIS AND FLUORESCENCE OF 6-(4-DIMETHYLAMINOPHENYL)-
AND 6-[2-(4-N,N-DISUBSTITUTED AMINOPHENYL)VINYL]-4-METHYLTHIO-
2-OXO-2H-PYRAN-3-CARBONITRILES IN SOLUTION AND IN THE SOLID
STATES
Naoko Mizuyama,a Yuka Murakami,a Junko Nagaoka,b Shinya Kohra,a Kazuo Ueda,a
Kyoko Hiraoka,a Yasuhiro Shigemitsu,c and Yoshinori Tominaga,a*
aFaculty of Enviromental Studies andbFaculty of Engineering of Nagasaki University, 1-14,
Bunkyo-machi, Nagasaki 852-8521, Japan; cTechnology Center of Nagasaki, 2-1308-8 Ikeda,
Omura, Nagasaki 856-0026, Japan
ae-mail: ytomi@net.nagasaki-u.ac.jp
Abstract—Fluorescent dyes, 6-(4-dimethylaminophenyl)-4-methylthio- and 6-[2-(4-N,N-
disubstituted aminophenyl)vinyl]-4-methylthio-2-oxo-2H-pyran-3-carbonitriles (3a-d) were
synthesized by the reaction of 4-dimethylaminoacetophenone (1a) and 4-aminobenzalacetone
derivatives (1b-d) with ketene dithioacetal (2) in the presence of sodium hydroxide in dimethyl-
sulfoxide at room temperature. These 2-pyrone derivatives (3a-d) showed orange and red
fluoresecence (Fmax: 607, 699, 705, 645 nm) in dichloromethane solution. The preparation and
fluorescence 4-amino-2H-pyrone derivatives is also described.
.
Fluorecent dyes which show fluorescence in the solid state are useful as materials such as emitters for electro-luminescence
(EL) devices for use in various fields.1 Several 4H-pyran derivatives, for instance 4-(dicyanomethylene)-2-methyl-6-(4-
dimethylaminostyryl)-4H-pyran (DCM), are interesting organic EL compounds.2 This suggests that 2H-pyrans might also
have useful EL, and may be red colored, one of the most important in the field of EL chemistry. Komatsu et al. reported
fluorescence for 3,4,6-triphenyl-2-pyrone derivatives in which the phenyl group at position 6 is important for fluorescent
expression.3 Here, interest was first directed at 6-(4-dimethylaminophenyl)-2H-pyran-2-one (3a), which showed interesting
fluorescence in the solid state, and it was hoped that 6-styryl-2H-pyran-2-ones (3b-d) would have superior red fluorescence.
Fluorescence was not detected in the 2-pyrone derivatives due to the vulnerability of the fluorescence in solution as noted in
previous study.4 The synthesis and fluorescent properties of the novel functional fluorophores, 6-(4-dimethylaminophenyl)-
4-methylthio- and 6-[2-(4-N,N-disubstituted aminophenyl)vinyl]-4-methylthio-2-oxo-2H-pyran-3-carbonitriles are reported
here. The reaction of 4-dimethylaminoacetophenone (1a) with 2-cyano-3,3-bis(methylthio)acrylonitrile (2) was carried out
in the presence of sodium hydroxide to give the desired product, 6-(4-dimethylaminophenyl)-4-methylthio-2-oxo-2H-pyran-

1106
HETEROCYCLES, Vol. 68, No. 6, 2006
3-carbonitrile (3a)6 in 43% yield, as described in Scheme 1. Benzalacetone derivatives, 4-(N,N-disubstituted
aminophenyl)but-3-en-2-ones (1b-d), also reacted with 2 in a manner similar to that described for the preparation of 3a
giving the corresponding 6-[2-(4-N,N-disubstituted aminophenyl)vinyl]-4-methylthio-2-oxo-2H-pyran-3-carbonitriles (3b-
d)7-9 in 32, 26, and 29% yields, respectively.
SMe
CN
O
MeS
MeS
CN
NaOH
O
O
n
+
n
R
R
N
R
COOMe
in DMSO
N
R
1a-d
3a-d
2
a: n=0, R=Me
b: n=1, R=Me
c: n=1, R=Et
d: n=1, R=Ph
a: n=0, R=Me
b: n=1, R=Me
c: n=1, R=Et
d: n=1, R=Ph
Scheme 1
4-Methylthio-2-oxo-2H-pyran-3-carbonitriles are very useful in the synthesis of 4-substituted 2H-pyran-2-ones and showed
the activity toward amino compounds or active methylene compounds. The 4-amino-2-oxo-2H-pyrane-3-carbonitriles (4a-
d)10were prepared in 24-64% yields by the reaction of 3a, b with amines (dimethylamine, pyrrolidine, and morpholine) in
refluxing methanol. The reaction of 3a, b with dimethyl malonate in the presence of potassium carbonate in DMSO gave the
corresponding desired products (5a, b)10 in 77 and 84%yields, respectively.
NR2
COOMe
Amines
CH2(COOMe)2
NaOH
CN
O
CH
refluxing
COOMe
CN
3a, b
in MeOH
in DMSO
O
R
O
O
R
4a-d
a: R=C6H4-NMe2(4), NR2=dimethylamino, Yield=64%
b: R=C6H4-NMe2(4), NR2=pyrrolidino, Yield=44%
c: R=C6H4-NMe2(4), NR2=morpholino, Yield=50%
d: R=CH=CH-C6H4-NMe2(4), NR2=morpholino, Yield=24%
5a, b
a: R=C6H4-NMe2(4), Yield=77%
b: R=CH=CH-C6H4-NMe2(4), Yield=84%
Scheme 2
DMC and AlQ3[tris(8-hydroxyquinolinato)aluminum] were used as standards for absorption and fluorescence spectra. The
measurements of both absorption and fluorescence spectra was carried out in dichloromethane solution at room temperature.
The spectroscopic properties, absorption maxima (λmax), molar absorptivities (ε), fluorescence maxima(Emmax), and relative
fluorescent intensities (RI) are listed in Table 1. The aryl and styryl bearing N,N-disubstituted amino group at the position 6
of the 2-pyrone derivatives fulfils the important effect of fluorescent expression, and are much simpler to prepared than
compounds produced following Komatsu’s procedure.3 Compounds (3a-d) showed longer wavelength shifts in comparison
with the most basic 2-pyrone, 6-phenyl-4-methylthio-2-oxo-2H-pyran.11 However, their relative fluorescence intensities
have a tendency to decrease, while the ε values increases in the absorption spectra. On the other hand, 4-substituted
compounds (5a, b) showed only a small bathochromic shift andfluorescence as compared to 3a and b. In comparisonwith
the 4-methylthio compounds (3a, b), the 4-amino compounds (4a-d) demonstrate hypsochromic shifts of the λmax and ε
value in the absorption spectra. The fluorescent properties of these 2-pyrone derivatives show a dependence on solvent
polarity. For example, the emission of 3a (541 nm), 3b (625 nm) and 4a (515 nm) in ethanol shifts to longer wavelength

HETEROCYCLES, Vol. 68, No. 6, 2006
1107
with an increase in the polarity of the solvent. This behavior is indicative of polar character in the exited state, presumably
associated with a contribution from the betaine form. Fluorescence in the solid state is very important for functional
fluorescent materials. The fluorescence of these 2-pyrone derivatives in the solid state was not particularly strong except for
4a-c. However, even compounds (3a, b, 5a, and b) showed stronger fluorescence than DCM, which has a typical red-
orange fluorescence in the solid state. The ΔF value, indicating the difference in Em from solid state to solution, varied
widely from 25 nm for dye (3d) to 109 nm for dye (4c). Only dye (5b) demonstrated a negative ΔF. The dimethylamino
group at position 6 and the dimethylamino group at position 4 are almost plane due to their small torsion angles (15°). This
phenomenon has caused strong molecular stacking which is one of the causes of solid state fluorescence from result of the
X-Ray crystallographic analysis (See ORTEP Representation and Molecular Paking Diagram of 4a showing in Figures 1
and 2).10 The molecular packing diagram of 4a clearly displays short intermolecular distances as shown in Figure 2. The
interplane distance between molecules is ca 3.12 Å.
Table 1. UV and fluorescence spectra of 6-aryl- and 6-vinyl-2H-pyran-2-ones in solution and in the solid states
λmax(logε)a
Mp
Ex(nm)
Em(nm)
Ex(nm)
Em(nm)
ΔFd
No.
SSb
RIc
RIe
℃
nm
(CH2Cl2)
466
541
554
573
391
391
407
460
CH2Cl2
531
610
612
620
465
464
497
582
542
629
577
Solid
301
300
346
349
294
373
322
300
296
558
342
Solid
607
699
705
645
517
537
606
645
610
620
645
3a
3b
3c
3d
4a
4b
4c
4d
5a
249-251
280-284
187-190
210-216
265-267
270-271
272-274
245-255
194-198
200-202
217-219
465(4.72)
513(4.67)
529(4.69)
498(3.78)
399(4.57)
395(4.60)
412(4.68)
459(4.58)
484(4.78)
528(4.47)
466(4.63)
66
97
83
122
93
73
85
122
58
101
111
8.54
2.36
0.93
0.01>
5.57
7.9
2.69
0.69
4.95
0.63
1
76
89
93
25
32
57
109
63
68
-9
0.15
0.01>
0.01>
0.01>
9.90
3.86
1.08
0.10
0.70
493
570
480
5b
DCM
0.40
0.01
68
aMeasurementinCH2Cl2.
bStoke'sShift,Em-Exinsolution.
cRelative intensityoffluorescence inthesolution,usingDCMasa standardcompound.
dΔF=Em(solid)-Em(solution).
eRelative intensityoffluorescence inthesolidstates,usingAlQ3as astandardcompound.
Figure 1. ORTEP of Asymmeteric Unit of 4a.
Figure 2. Molecular Packing Diadram of4a.
In conclusion, 6-aryl- and 6-styryl-2-oxo-2H-pyran-3-carbonitriles are valuable as new fluorescent chromophores having

1108
HETEROCYCLES, Vol. 68, No. 6, 2006
large εmax values and long wavelength absorption and emission. The presence of an amino group at the para-position of the
aryl group shifts the emission to longer wavelength. The 2-pyrone derivatives bearing an electron-donating group at the 4-
position and an electron-withdrawing group at the 3-position of the 2-pyronefluoresce in solution and in the solidstate.
REFERENCES AND NOTES
1.
a) C. W. Tang and S. A. Van Slyke, Appl. Phys. Lett., 1987, 51, 913. b) C. W. Tang, S. A. Van Slyke, and C. H. Chen, J. Appl.
Phy., 1989, 65, 3610. c) M. Matsuoka, J. Soc. Dyers and Colourists, 1989, 105, 167. d) K. Shirai, A. Yanagisawa, H. Takahashi,
K. Fukunishi, and M. Matsuoka, Dyes and Pigments, 1998, 39, 49. e) K. Shirai, M. Matsuoka, and K. Fukunishi, Dyes and
Pigments, 2000, 47, 107.
2.
3.
a) J. H. Burroghed, Nature, 1990, 347, 539. b) M. A. Baldo, M. E. Thompson, and S. R. Forrest, Nature, 2000, 403, 750.
a) K. Hirano, S. Minakata, and M. Komatsu, Chem. Lett., 2001, 8. b) K. Hirano, S. Minakata, and M. Komatsu, Bull. Chem. Soc.
Jpn., 2001, 74, 1567.
4.
a) Y. Tominaga, Y. Matsuda, and G. Kobayashi, Heterocycles, 1976, 4, 1493. b) Y. Tominaga, A. Ushirogouchi, Y. Matsuda,
and G. Kobayashi, Heterocycles, 1977, 8, 193. c) Y. Tominaga, Y. Matsuda, and G. Kobayashi, Chem. Pharm. Bull., 1984, 32,
1665. d) Y. Tominaga, A. Ushirogouchi, Y. Matsuda, and G. Kobayashi, Chem. Pharm. Bull., 1984, 32, 3384. e) Y. Tominaga,
A. Ushirogouchi, and Y. Matsuda, J. Heterocycl. Chem., 1987, 24, 1557. f) Y. Tominaga, J. Org. Synth. Chem., 1989, 47, 413.
5.
6.
7.
3a: red prisms (MeOH-toluene). 1H-NMR (CDCl3)δ 2.66 (3H, s, SMe), 3.11 (6H, s, 2xNMe2), 6.47 (1H, s, 5-H), 6.69(2H,
d, J=9.0 Hz, 3', 4'-H), 7.75 (2H, d, J=9.0 Hz, 2', 6'-H).
3b: black violet leaflets(MeOH-toluene). 1H-NMR(CDCl3) δ: 2.65(3H, s, SMe), 3.10(6H, s, 2xNMe2), 12(1H, s, 6-H),
6.44 (1H, d, J=15.7 Hz, =CH), 6.72 (2H, J=9.1 Hz, 3’, 5’-H), 7.48 (2H, d, J=9.1 Hz, 2’, 6’-H), 7.68 (2H, d, J=15.7 Hz, =CH).
3c: black violet leaflets (MeOH-toluene). 1H-NMR(CDCl3) δ: 1.21(6H, t, J=7.1 Hz, N-CH2-CH3), 2.61(3H, s, SMe),
3.43 (4H, q , J=7.1 Hz, N-CH2-), 6.07 (1H, s, 5-H), 6.37(1H, d, J=15.7 Hz, =CH), 6.65 (2H, d, J=9.1 Hz, 3’, 5’-H), 7.42(2H,
d, J=9.1 Hz, 2’, 6’-H), 7.63 (1H, d, J=15.7 Hz, =CH).
8.
9.
3d: red brown leaflets (MeOH-toluene). 1H-NMR(CDCl3) δ: 2.62(3H, s, SMe), 6.18(1H, s, 5-H), 6.48(1H, d, J=15.1 Hz,
=CH), 6.75-7.40 (14H, m, phenyl-H), 7.61(1H, d, J=15.1 Hz, =CH).
4a: lemon yellowneedles (MeOH). 4b: lemon yellowneedles (MeOH). 4c: yellowneedles (MeOH). 4d: orange needles
(MeOH). 5a: orange needles (MeOH). 5b: red needles (MeOH).
10. Crystal data of 4a: lemon yellowneedles (C16H17N3O2=283.33, 0.40 x 0.12 x 0.08 mm3), orthorhombic, space group=P212121,
Z=8, a=7.5938Å, b=14.0254Å, c=27.4606Å, V=2924.72 Å3, D(calcd)=1.28g/cm3, µ(Mo-Kα)=0.90 cm-1, F(000)=1200,
Reflection=11603, Residuals=0.044(R1), 0.106(wR2).
11. In the 6-phenyl-2-pyrone derivatives, the fluorescent intensity in which the derivatives on the phenyl group with an electron
donating group is stronger than other compounds was clarified.
12. These 2-oxo-2H-pyran-3-carbonitriles (3a-d, 4a-d) can use as a fluorescence reagent in an oxalate chemiluminscence system.