Synthesis and photochromic properties of N 2-alkyl-5-furyl-4- thienylpyridazinones

Article abstract of DOI:10.1007/s11172-011-0025-y

New dihetarylethenes containing the six-membered bridging moiety, viz., N ²-alkyl-5-furyl-4-thienylpyridazinones, were synthesized. These compounds have photochromic properties in solution. The hindered rotation of the thiophene and furan rings around the single bonds that link these rings to the double bond of the pyridazinone moiety results in the formation of mixtures of chiral diastereomers in solution, the lifetimes of the diastereomers being no longer than 0.2 s. The photochromic rearrangement of pyridazinones is characterized by the highly efficient photocoloration and the photobleaching, which is an order of magnitude less efficient, in the absence of thermal relaxation processes.

Full text of DOI:10.1007/s11172-011-0025-y

Russian Chemical Bulletin, International Edition, Vol. 60, No. 1, pp. 168—174, January, 2011
168
Synthesis and photochromic properties of
N2ꢀalkylꢀ5ꢀfurylꢀ4ꢀthienylpyridazinones
O. G. Karamov,a V. P. Rybalkin,b N. I. Makarova,a A. V. Metelitsa,a V. S. Kozyrev,a
G. S. Borodkin,a L. L. Popova,a V. A. Bren´,a and V. I. Minkina,b
aInstitute of Physical and Organic Chemistry, Southern Federal University,
194/2 prosp. Stachki, 344090 RostovꢀonꢀDon, Russian Federation.
Eꢀmail: dubon@ipoc.rsu.ru
bSouthern Scientific Center of Russian Academy of Sciences,
41 ul. Chekhova, 344006 RostovꢀonꢀDon, Russian Federation
New dihetarylethenes containing the sixꢀmembered bridging moiety, viz., N2ꢀalkylꢀ5ꢀfurꢀ
ylꢀ4ꢀthienylpyridazinones, were synthesized. These compounds have photochromic properties
in solution. The hindered rotation of the thiophene and furan rings around the single bonds that
link these rings to the double bond of the pyridazinone moiety results in the formation of
mixtures of chiral diastereomers in solution, the lifetimes of the diastereomers being no longer
than 0.2 s. The photochromic rearrangement of pyridazinones is characterized by the highly
efficient photocoloration and the photobleaching, which is an order of magnitude less efficient,
in the absence of thermal relaxation processes.
Key words: pyridazinꢀ3ꢀones dihetarylethenes, synthesis, photochromism, fluorescence,
photocolorability, molecular switches.
Due to the high thermal stability of isomeric forms and
Results and Discussion
resistance to photodegradation, photochromic dihetꢀ
arylethenes belong to one of the most promising classes
of molecular structures for the design of elements for
optical information recording devices and optical switchꢀ
es.1—5 The structure of the bridging ring with a douꢀ
ble bond can have a substantial effect on the photoꢀ
chromic properties of dihetarylethenes. Most of photoꢀ
chromic dihetarylethenes were synthesized based on
fiveꢀmembered bridging moieties. 4,5ꢀDithienylpyridꢀ
azinones studied earlier6 are rare examples of photoꢀ
chromic ethenes containing the sixꢀmembered cyclic
bridging moiety. A few dihetarylethenes containing variꢀ
ous substituents at the molecular bridge are known. Derivꢀ
atives containing at least one thiophene moiety conjugated
to the C=C bond have particularly useful photochromic
properties.7 In our opinion, systems belonging to this class
of ethenes and containing both the thiophene and furan
moieties at the ethylene bond of pyridazinone may be
of interest.
Pyridazinones were synthesized according to the scheme
reported in the study.6 Acid 1 was prepared according to
a known procedure8 from 3ꢀacetylꢀ2,5ꢀdimethylthiophene
by the Willgerodt—Kindler reaction followed by the hyꢀ
drolysis. Ketone 2 was synthesized from 2,5ꢀdimethylꢀ
furan and chloroacetyl chloride in the presence of AlCl3.
The reaction of thienylacetic acid 1 with compound 2
affords furanone 3. The latter reacts with benzaldehyde in
the presence of piperidine to form benzylidenefuranone 4,
which reacts with hydrazine hydrate to give 6ꢀbenzylꢀ5ꢀ
(2,5ꢀdimethylꢀ3ꢀfuryl)ꢀ4ꢀ(2,5ꢀdimethylꢀ3ꢀthienyl)ꢀ3(2H)ꢀ
pyridazinꢀ2ꢀone (5). The reaction of compound 5 with
alkyl halides gives the corresponding 2ꢀalkylꢀ6ꢀbenzylꢀ5ꢀ
(2,5ꢀdimethylꢀ3ꢀfuryl)ꢀ4ꢀ(2,5ꢀdimethylꢀ3ꢀthienyl)ꢀ3(2H)ꢀ
pyridazinꢀ2ꢀones 6a—d (Scheme 1).
The structures of the compounds were confirmed by
IR and 1H NMR spectroscopy.
1
In the H NMR spectra of compounds 5 and 6a—d,
The aim of the present study was to synthesize new
pyridazinones containing the thienyl and furyl moieties at
positions 4 and 5, respectively, as well as N2ꢀalkyl substitꢀ
uents, and to investigate their photochromic and spectralꢀ
luminescent properties for the purpose of examining the
influence of structural factors on the aboveꢀmentioned
properties of dihetarylpyridazinones.
the singlets for protons of the heterocyclic moieties and
singlets for protons of particular methyl and methylene
groups are split with the integrated intensity ratio of ~9 : 10,
which is evidence that there are two diastereomers in
solutions (Fig. 1). In addition, the signals of the benzylic
methylene groups at the nitrogen atom and at position 6 of
the pyridazinone ring appear as an AB system for both
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 161—166, January, 2011.
1066ꢀ5285/11/6001ꢀ168 © 2011 Springer Science+Business Media, Inc.

Photochromism of 5ꢀfurylꢀ4ꢀthienylpyridazinones
Russ.Chem.Bull., Int.Ed., Vol. 60, No. 1, January, 2011
169
Scheme 1
R = Me (a), Et (b), 4ꢀClC6H4CH2 (c), 4ꢀCNC6H4CH2 (d); X = I, Br
diastereomers, which is indicative of the presence of two
pairs of enantiomers in solutions.
of enantiomers diastereomeric to each other, to be more
precise, the presence of two pairs of rotamers with the
parallel (p1 and p2) and antiparallel (a1 and a2) arrangeꢀ
ment of the furan and thiophene rings (see Scheme 2).
Moreover, the rotation of the thiophene and furan rings
can be completely hindered, which will result in the existꢀ
ence of stable atropisomers and will have a substantial
effect on the photochromic process, because the photoꢀ
induced electrocyclic reaction of ethenes occurs only in
Actually, the molecular structures of pyridazinones show
that these compounds can exist as rotamers9 (Scheme 2).
Due to the hindered rotation around two single bonds
in dihetarylpyridazinones, there are two chiral axes along
the single bonds of each heterocycle with a double bond.
In turn, the presence of two such sources of chirality in the
molecules may be manifested in the presence of two pairs
I
1.0
3 Me
0.9
0.8
0.7
0.6
0.5
0.4
0.3
CH2
Me
0.2
CHfuran
0.1
0
NCH2
CHthiophene
4.13 2.98 1.87
1.01
0.96
2.15
2.00
9.10
3.02
7.5
7.0
6.5
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
δ
Fig. 1. 1H NMR spectrum of compound 6c in CDCl3.

170
Russ.Chem.Bull., Int.Ed., Vol. 60, No. 1, January, 2011
Karamov et al.
Scheme 2
required. Hence, the rate of this process is limited by the
hindered rotation of the heterocycle with the highest enerꢀ
gy barrier (in the case under consideration, of the furan
ring). The lifetime of the diastereomers of compound 6c
1
calculated from the line shapes10 in the H NMR spectra
was 0.2 s at 20 °C (see Fig. 2).
Since the rate of rotamerization was sufficiently high
to maintain the constant ratio of the rotamers during
steadyꢀstate UV irradiation at room temperature, the obꢀ
served formation of a mixture of relatively stable rotamers
of pyridazinones 5 and 6a—d cannot have a substantial
effect on the photochromic properties of the compounds
under these conditions.
The results of the spectroscopic and photochemical
studies of 5ꢀfurylꢀ4ꢀthienylꢀ3(2H)ꢀpyridazinones are givꢀ
en in Tables 1 and 2.
The electronic absorption spectra of dihetarylethenꢀ
es 5 and 6a—d (Scheme 3, form A) are characterized
by longꢀwavelength absorption bands with maxima at
320—326 nm and the molar extinction coefficients of
6450—8100 L mol–1 cm–1 (see Table 1).
the case of the conformer containing heterocycles in the
antiparallel orientation.9 We studied this intramolecular
process by dynamic NMR spectroscopy.
Scheme 3
1
The temperature changes in the H NMR spectra in
DMSOꢀd6 (Fig. 2) are indicative of interconversions of
these four isomers (rotamerization). The rate of the interꢀ
←
←
a ) is
→
2
conversion of the diastereomers (p1
a and p
→
1
2
much higher than the rate of the enantiomerization
←
←
a ). Actually, the rotation of one hetꢀ
→
2
(p1
p and a
→
2
1
erocycle is sufficient for the interconversion of diastereoꢀ
mers. Hence, the rate of this process is limited by the
hindered rotation of one ring with the lower energy barrier
(in the case under consideration, of the thiophene ring).
For the enantiomerization, the rotation of both rings is
The introduction of alkyl substituents at position 2 of
the pyridazinone ring leads to small (~5—6 nm) bathoꢀ
140 °C
95 °C
75 °C
45 °C
40 °C
20 °C
δ
6.5 6.0 5.5 5.0
4.5 4.0 3.5
δ
2.2
2.0
1.8
1.6
1.4
Fig. 2. 1H NMR spectra of compound 6c in DMSOꢀd6 at different temperatures.

Photochromism of 5ꢀfurylꢀ4ꢀthienylpyridazinones
Russ.Chem.Bull., Int.Ed., Vol. 60, No. 1, January, 2011
171
Table 1. Spectralꢀabsorption and fluorescence characteristics of isomeric forms of dihetarylethenes 5
and 6a—d in toluene at 293 K
Comꢀ
pound
Form A
Form B
Absorption,
Absorption
max/L mol–1 cm–1
Fluorescence, λmax/nm
λ
max/nm
λmax/nm
ε
Excitation
Emission
5
320
325
326
325
325
6450
7220
7680
8100
7030
324
326
328
326
327
428
420
420
425
423
552
557
557
557
557
6a
6b
6c
6d
chromic shifts of the maxima of the longꢀwavelength abꢀ
sorption bands of compounds 6a—d compared to unsubꢀ
stituted dihetarylethene
5. It should be noted
that the absorption of
the unsymmetrical diꢀ
hetarylethenes is shifted
by ~10 nm to longer
wavelengths compared
As in the case of the starting forms A, the substitution
at position 2 of the pyridazinone ring in the closed isomers
B of dihetarylethenes 6a—d leads to the bathochromic
shift of the longꢀwavelength maxima by 5 nm compared to
unsubstituted compound 5 (see Table 1). A comparison of
compound 6a with the symmetrical analog, viz., 6ꢀbenzꢀ
ylꢀ4,5ꢀbis(2,5ꢀdimethylꢀ3ꢀthienyl)ꢀ2ꢀmethylꢀ2Hꢀpyridꢀ
azinꢀ3ꢀone (7), shows a considerable shortꢀwavelength
shift (~21 nm) of the absorption band maximum of its
closed isomer B.6
to the symmetrical anaꢀ
log, viz., 6ꢀbenzylꢀ4,5ꢀ
bis(2,5ꢀdimethylꢀ3ꢀthienyl)ꢀ2ꢀmethylꢀ2Hꢀpyridazinꢀ3ꢀ
one (7), studied earlier.6
The closed isomers B of compounds 5 and 6a—d are
characterized by high thermal stability. Once the UV irraꢀ
diation treatment is terminated, the backward dark reacꢀ
tion B → A in toluene is not observed at 293 K for 48 h. By
contrast, the irradiation at longꢀwavelength absorption
bands of the photoproducts B results in the bleaching of
solutions associated with the backward ringꢀopening
photoreactions B → A.
The spectral changes observed at the absorption bands
of the open isomers A are worthy of note. Instead of
a decrease in the intensity of the absorption bands correꢀ
sponding to the forms A (due to the photoreaction A → B)
The open isomers A of 4,5ꢀdihetarylpyridazinones exꢀ
hibit fluorescence properties. The fluorescence maxima of
compounds 5 and 6a—d in toluene at 293 K are observed
at 420—428 nm (see Table 1, Fig. 3). The fluorescence
excitation spectra of dihetarylethenes 5 and 6a—d coinꢀ
cide well with their longꢀwavelength absorption bands (see
Table 1). The efficiency of fluorescence is low, and the
quantum yields are lower than 10–4
.
The UV irradiation of solutions of 4,5ꢀdihetarylpyꢀ
ridazinones 5 and 6a—d at longꢀwavelength absorption
bands leads to their coloration accompanied by the apꢀ
pearance of absorption bands with maxima at 552—557 nm
in the electronic absorption bands (see Table 1, Fig. 4).
These spectral changes are characteristic1 of the cyclizaꢀ
tion photoreactions of dihetarylethenes A → B.
Ifl (rel. units)
6
2
1
5
4
3
2
1
B
Table 2. Characteristics of the photocoloration (Φ
and photobleaching (Φ
ethenes 5 and 6a—d in toluene at 293 K
ε
)
AB max
ε
B) reactions of dihetarylꢀ
BA max
B
Comꢀ
pound
Φ
ε
•102
Φ
ε
•102
B
Φ
AB/Φ
BA
AB max
BA max
L mol–1 cm–1
5
47.8
5.2
9.2
13.0
12.7
13.6
14.4
6a
6b
6c
6d
55.9
52.2
57.2
59.0
4.3
4.1
4.2
4.1
300
350
400
450
500
550
λ/nm
Fig. 3. Fluorescence spectra (λex = 320 nm) (1) and fluorescence
excitation spectra (λobs = 450 nm) (2) of a solution of compound
5 in toluene (T = 293 K).

172
Russ.Chem.Bull., Int.Ed., Vol. 60, No. 1, January, 2011
Karamov et al.
A
To sum up, we synthesized substituted 5ꢀfurylꢀ4ꢀthiꢀ
enylꢀ3(2H)ꢀpyridazinones 5 and 6a—d exhibiting photoꢀ
chromic properties. New unsymmetrical dihetarylethenes
are characterized by the high efficiency of photocoloraꢀ
tion, which is an order of magnitude higher than the effiꢀ
ciency of photobleaching, and by the thermal stability of
the photoinduced closed forms.
0.5
0.4
0.3
0.2
0.1
0
12
1
Experimental
The UVꢀVis spectra were recorded on a Cary 100 spectroꢀ
photometer (Varian). The fluorescence measurements were carꢀ
ried out on a Cary Eclipse spectrofluorimeter (Varian). The soluꢀ
tions were irradiated in a quartz cell (l = 1 cm) with a DRShꢀ250
mercury lamp equipped with a kit of interference light filters to
select lines of the mercury spectrum.
300
400
500
600
λ/nm
Fig. 4. Electronic absorption spectra of compound 5 in toluene
before (1) and after the successive irradiation at λ = 313 nm
recorded at 60 s intervals (2—12) (C = 4•10–5 mol L–1, T = 293 K).
The kinetic curves for the photocoloration of solutions of
dihetarylethenes were measured directly during irradiation on
a Cary 50 spectrophotometer equipped with a temperatureꢀconꢀ
trolled cell holder. A xenon lamp with a monochromator to
produce narrow spectral lines (Newport) was used as a radiation
source. The intensity of optical radiation was determined with
the use of a Newport 2935 power meter. The intensity of optical
radiation at the wavelengths used (313 and 546 nm) was 3.18•1014
and 7.32•1015 photon s–1, respectively. To determine the paꢀ
expected upon exposure to UV light, an increase in the
intensity of these bands is observed (see Fig. 4). Evidently,
this effect is associated with the overlap of the higherꢀ
intensity bands corresponding to S0→S2 transitions of the
closed forms B with lowerꢀintensity bands belonging to
S0→S1 transitions of the forms A of 4,5ꢀdihetarylpyridꢀ
azinones 5 and 6a—d. The overlap of the absorption bands
of the isomeric forms is responsible also for the absence of
the complete photoinduced conversion of the starting diꢀ
hetarylethenes A into the closed derivatives B. Upon
the exposure to UV light, the photostationary state is
achieved. In this state, the ratio of the forms is determined
by a number of factors, such as (in the case under conꢀ
sideration) the quantum yields of the photocoloration
and photobleaching and the ratio of the molar extincꢀ
tion coefficients of the isomeric forms at the radiation
wavelength.
rameters Φ
ε
B and Φ
ε
B, the slope of the tangent line at
AB max
BA max
the initial instant was calculated from the kinetic curves for the
photocoloration and photobleaching; the absorbance of soluꢀ
tions of dihetarylethenes at wavelengths of radiation was chosen
to be identical.
The IR spectra were recorded on a Varian Excalibur 3100
FTꢀIR instrument. The 1H NMR spectra were measured on
a Varian Unityꢀ300 instrument (300 MHz) in CDCl3 with the
use of HMDS as the external standard. The dynamic NMR
spectra were recorded on an Avance Brukerꢀ600 instrument
(600 MHz) in DMSOꢀd6.
(2,5ꢀDimethylꢀ3ꢀthienyl)acetic acid (1) was synthesized acꢀ
cording to a known procedure8 from 3ꢀacetylꢀ2,5ꢀdimethylꢀ
thiophene (15.95 g, 0.1 mol). The yield was 8.74 g (50%), colorꢀ
less crystals, m.p. 67.5—68 °C (from aqueous ethanol).
2ꢀChloroꢀ1ꢀ(2,5ꢀdimethylꢀ3ꢀfuryl)ethanone (2). Dry dichloroꢀ
ethane (25 mL) and chloroacetyl chloride (4.2 mL, 52 mmol)
were placed in a 50 mL fourꢀnecked flask equipped with a therꢀ
mometer, a stirrer, a reflux condenser, and a dropping funnel,
and then AlCl3 (7 g, 52 mmol) was added with stirring and coolꢀ
ing to 5 °C for 10 min. Then 2,5ꢀdimethylfuran (5.0 g, 52 mmol)
was added dropwise to the reaction solution. The cooling was
stopped. The reaction mixture was stirred at room temperature
for 0.5 h and then poured onto ice. The organic layer was sepaꢀ
rated, successively washed with water, 10% Na2CO3, water, and
dried over CaCl2. The solvent was distilled off, and chloroꢀ
ethanone 2 was recrystallized. The yield was 2.62 g (29%), colorꢀ
less long prisms, m.p. 86—87 °C (MeOH). IR, ν/cm–1: 1683
(C=O). 1H NMR, δ: 2.25 and 2.55 (both s, 3 H each, Me); 4.32
(s, 2 H, CH2); 6.17 (s, 1 H, HHet). Found (%): C, 55.86; H, 5.15;
Cl, 20.41. C8H9ClO2. Calculated (%): C, 55.67; H, 5.26;
Cl, 20.54.
The developed dynamics of the growth of absorption
bands of the photoproducts B in the conditions of the
aboveꢀmentioned overlap of the absorption bands of difꢀ
ferent forms at the excitation wavelength of the photoreꢀ
action may be indicative of a substantially lower efficiency
of the photobleaching reaction compared to the photocolꢀ
oration reaction. To estimate the efficiencies of the forꢀ
ward and backward photoreactions, we determined the
products of ΦAB max
B (the soꢀcalled photocolorability) and
ε
ΦBAεmaxB (see Table 2). The ratios of the quantum yield of
photocolorations to the quantum yield of photobleaching
(ΦAB/ΦBA) determined from these data clearly show
that the efficiency of the photocyclization of dihetarylꢀ
ethenes 5 and 6a—d is an order of magnitude higher than
the efficiency of their ringꢀopening photoreactions. The
estimation of the quantum yields of the photocyclization
ΦAB for the average molecular extinction coefficient
4ꢀ(2,5ꢀDimethylꢀ3ꢀfuranyl)ꢀ3ꢀ(2,5ꢀdimethylꢀ3ꢀthienyl)furanꢀ
2(5H)ꢀone (3). A mixture of acid 1 (0.19 g, 1.1 mmol), ketone 2
(0.17 g, 1.1 mmol), K2CO3 (0.35 g, 2.5 mmol), and dry DMF
εmax = 10000 L mol–1 cm–1 taken from the published
B
data11—16 gives high values (up to 0.5—0.6).

Photochromism of 5ꢀfurylꢀ4ꢀthienylpyridazinones
Russ.Chem.Bull., Int.Ed., Vol. 60, No. 1, January, 2011
173
(1.2 mL) was heated with stirring at 78—82 °C for 3 h. After
cooling, water (6 mL) was added to the reaction mixture, and the
oil that formed was extracted with diethyl ether (3×3 mL). The
ethereal solution was washed with water (2×2 mL) and brine and
dried over anhydrous Na2SO4. The diethyl ether was removed,
and the residue was triturated with ethanol (0.5 mL). Solid prodꢀ
uct 3 was filtered off, washed with ethanol, and dried in air. The
yield was 135 mg (47%), colorless needles (from ethanol), m.p.
Ar). Found (%): 71.59; H, 6.17; N, 6.49. C25H26N2O2S. Calcuꢀ
lated (%): C, 71.74; H, 6.26; N, 6.69.
6ꢀBenzylꢀ2ꢀ(4ꢀchlorobenzyl)ꢀ5ꢀ(2,5ꢀdimethylꢀ3ꢀfuryl)ꢀ4ꢀ
(2,5ꢀdimethylꢀ3ꢀthienyl)ꢀ3(2H)ꢀpyridazinꢀ2ꢀone (6c) was syntheꢀ
sized analogously to compound 6a from pyridazinone 5 (100 mg,
0.26 mmol) and pꢀchlorobenzyl bromide (56 mg, 0.27 mmol).
The yield was 69 mg (52%), colorless crystals, m.p. 131—132 °C
1
(from methanol). IR, ν/cm–1: 1640 (C=O). H NMR, δ: 1.34
1
94 °C. H NMR, δ: 2.11, 2.14, 2.19, and 2.44 (all s, 3 H each,
and 1.38 (both br.s, a total of 3 H, Me); 1.90—2.32 (br.m, 9 H,
Me); 3.78—3.91 (m, 2 H, CH2); 5.14—5.54 (br.m, 2 H, CH2);
5.68 and 5.74 (both br.s, a total of 1 H, HHet); 5.96 and 6.90
(both br.s, a total of 1 H, HHet); 6.88 (br.m, 2 H, Ar); 7.11—7.23
(m, 3 H, Ar); 7.29—7.49 (m, 4 H, Ar). Found (%): C, 69.80;
H, 5.15; N, 5.34. C30H27ClN2O2S. Calculated (%): C, 69.96;
H, 5.28; N, 5.44.
6ꢀBenzylꢀ(4ꢀcyanobenzyl)ꢀ5ꢀ(2,5ꢀdimethylꢀ3ꢀfuryl)ꢀ4ꢀ(2,5ꢀ
dimethylꢀ3ꢀthienyl)ꢀ23(2H)ꢀpyridazinꢀ2ꢀone (6d) was synthesized
analogously to compound 6a from pyridazinone 5 (100 mg,
0.26 mmol) and 4ꢀcyanobenzyl bromide (53 mg, 0.27 mmol). The
yield was 50 mg (39%), colorless crystals, m.p. 130—130.5 °C
(from MeOH). IR, ν/cm–1: 1639 (C=O), 2229 (C≡N). 1H NMR,
δ: 1.38 (br.m, 3 H, Me); 1.91—2.32 (br.m, 9 H, Me); 3.80—3.91
(m, 2 H, CH2); 5.22—5.60 (br.m, 2 H, CH2); 5.71 and 5.76
(both br.s, a total of 1 H, HHet); 6.00 and 6.45 (both br.s, a total
of 1 H, HHet); 6.88 (br.m, 2 H, Ar); 7.00—7.22 (m, 3 H, Ar);
7.36—7.70 (m, 4 H, Ar). Found (%): C, 73.81; H, 5.49; N, 8.19.
C31H27N3O2S. Calculated (%): C, 73.64; H, 5.38; N, 8.31.
Me); 5.07 (s, 2 H, CH2); 5.74 and 6.57 (both s, 1 H each, HHet).
Found (%): C, 66.47; H, 5.65; S, 11.32. C16H16O3S. Calculatꢀ
ed (%): C, 66.64; H, 5.59; S, 11.12.
5ꢀBenzylideneꢀ4ꢀ(2,5ꢀdimethylꢀ3ꢀfuranyl)ꢀ3ꢀ(2,5ꢀdimethylꢀ
3ꢀthienyl)furanꢀ2(5H)ꢀone (4) was synthesized by analogy with
the known procedure17 from bifuranone 3 (0.29 g, 1 mmol) and
benzaldehyde (0.15 g, 1.4 mmol). The yield was 0.28 g (74%),
greenishꢀyellow crystals, m.p. 128—130 °C. IR, ν/cm–1: 1763
1
(C=O). H NMR, δ: 1.85, 2.04, 2.32, and 2.40 (all s, 3 H each,
Me); 6.03 and 6.16 (both s, 1 H each, HHet); 6.30 (s, 1 H, CH);
7.28—7.46 (m, 3 H, Ar); 7.78—7.87 (m, 2 H, Ar). Found (%):
C, 78.53; H, 5.47; S, 8.39. C23H20O3S. Calculated (%): C, 78.38;
H, 5.35; S, 8.52.
6ꢀBenzylꢀ5ꢀ(2,5ꢀdimethylꢀ3ꢀfuryl)ꢀ4ꢀ(2,5ꢀdimethylꢀ3ꢀthiꢀ
enyl)ꢀ3(2H)ꢀpyridazinꢀ2ꢀone (5) was synthesized by analogy with
the known procedure6 from compound 4 (200 mg, 0.53 mmol)
and hydrazine hydrate (0.05 mL). The yield was 190 mg (92%),
colorless crystals, m.p. 224—226 °C. IR, ν/cm–1: 2874 (NH).
1H NMR, δ: 1.37 (s, 3 H, Me); 1.98—2.40 (br.m, 9 H, Me);
3.85 (m, 2 H, CH2); 5.75 (s, 1 H, HHet); 6.01 and 6.48 (both br.s,
a total of 1 H, HHet); 6.85—6.95 (m, 2 H, Ar); 7.10—7.25
(m, 3 H, Ar); 10.62 (br.s, 1 H, NH). Found (%): C, 70.57;
H, 5.81; N, 7.32. C23H22N2O2S. Calculated (%): C, 70.74;
H, 5.68; N, 7.17.
6ꢀBenzylꢀ5ꢀ(2,5ꢀdimethylꢀ3ꢀfuryl)ꢀ4ꢀ(2,5ꢀdimethylꢀ3ꢀthiꢀ
enyl)ꢀ2ꢀmethylꢀ3(2H)ꢀpyridazinꢀ2ꢀone (6a). A mixture of pyridꢀ
azinone 5 (100 mg, 0.26 mmol) and 60% sodium hydride (15 mg,
0.39 mmol) in dry DMF (3 mL) was heated with stirring in
a water bath for 2 h. Then CH3I (0.03 mL, 0.5 mmol) was added.
The reaction mixture was heated for 8 h, cooled, and diluted
with H2O (15 mL). The reaction product was extracted with
CH2Cl2. The extract was successively washed with water and
brine and dried with anhydrous Na2SO4. The solvent was
distilled off, and the crude product was recrystallized. The
yield was 60 mg (58%), m.p. 120.5—122 °C (from MeOH).
IR, ν/cm–1: 1638 (C=O). 1H NMR, δ: 1.34 and 1.37 (both br.s,
a total of 3 H, Me); 1.90—2.35 (br.m, 9 H, Me); 3.70—3.90
(m, 5 H, CH2 + Me); 5.70 and 5.73 (both br.s, a total of 1 H,
HHet); 6.01 and 6.48 (both br.s, a total of 1 H, HHet); 6.85—6.95
(m, 2 H, Ar); 7.15—7.22 (m, 3 H, Ar). Found (%): C, 71.06;
H, 6.11; N, 6.72. C24H24N2O2S. Calculated (%): C, 71.26;
H, 5.98; N, 6.92.
This study was financially supported by the Federal
Agency for Science and Innovation (Federal Target Proꢀ
gram "Scientific and ScientificꢀPedagogical Personnel of
the Innovative Russia in 2009ꢀ2013," Government Conꢀ
tract 02.740.11.0456) and the Russian Foundation for Baꢀ
sic Research (Project No. 09ꢀ03ꢀ00813).
References
1. M. Irie, Chem. Rev., 2000, 100, 1685.
2. V. I. Minkin, Chem. Rev., 2004, 104, 2751.
3. M. M. Krayushkin, Khim. Geterotsikl. Soedin., 2001, 19
[Chem. Heterocycl. Compd. (Engl. Transl.), 2001].
4. K. Matsuda, M. Irie, J. Photochem. Photobiol. C: Photochem.
Rev., 2004, 5, 169.
5. V. A. Barachevsky, V. P. Strokach, V. A. Puankov, O. T.
Kovaleva, T. M. Valova, K. S. Zavchenko, M. M. Krayushꢀ
kin, ARKIVOC, 2009, 9, 70.
6. M. M. Krayushkin, D. V. Pashchenko, B. V. Lichitskii, B. V.
Nabatov, A. N. Komogortsev, L. G. Vorontsova, Z. A. Starikꢀ
ova, Izv. Akad. Nauk, Ser. Khim., 2008, 2126 [Russ. Chem.
Bull., Int. Ed., 2008, 57, 2168].
6ꢀBenzylꢀ2ꢀethylꢀ5ꢀ(2,5ꢀdimethylꢀ3ꢀfuryl)ꢀ4ꢀ(2,5ꢀdimethylꢀ
3ꢀthienyl)ꢀ3(2H)ꢀpyridazinꢀ2ꢀone (6b) was synthesized analoꢀ
gously to compound 6a from pyridazinone 5 (100 mg, 0.26 mmol)
and EtI (0.04 mg, 0.5 mmol). The yield was 65 mg (61%), colorꢀ
less crystals (from aqueous MeOH), m.p. 114—114.5 °C. IR,
7. A. Yu. Bochkov, V. N. Yarovenko, V. A. Barachevskii, B. V.
Nabatov, M. M. Krayushkin, S. M. Dolotov, V. F. Traven´,
I. P. Beletskaya, Izv. Akad. Nauk, Ser. Khim., 2009, 162 [Russ.
Chem. Bull., Int. Ed., 2009, 58, 162].
8. Organikum Organischꢀchemischen Grundpraktikum, VEB
Deutscher Verlag der Wissenschaften, Berlin, 1976.
9. M. Irie, Chem. Rev., 2000, 100, 1697.
10. B. I. Ionin, B. A. Ershov, YaMRꢀspektroskopiya v organiꢀ
cheskoi khimii [NMR Spectroscopy in Organic Chemistry],
Khimiya, Leningrad, 1967, 286 (in Russian).
1
ν/cm–1: 1640 (C=O). H NMR, δ: 1.36 (br.m, 3 H, Me); 1.46
(t, 3 H, Me, J = 7.2 Hz); 1.90—2.40 (br.m, 9 H, Me); 3.80—3.93
(m, 2 H, CH2); 4.07—4.25 (br.m, 2 H, CH2); 5.71 and 5.74
(both br.s, a total of 1 H, HHet); 6.00 and 6.47 (both br.s, a total
of 1 H, HHet); 6.85—6.92 (br.m, 2 H, Ar); 7.10—7.22 (m, 3 H,

174
Russ.Chem.Bull., Int.Ed., Vol. 60, No. 1, January, 2011
Karamov et al.
11. S. Pu, M. Li, C. Fan, G. Liu, L. Shen, J. Mol. Struct., 2009,
919, 100.
16. M. Takeshita, M. Ogava, K. Miyata, T. Yamato, J. Phys.
Org. Chem., 2003, 16, 148.
12. Y.ꢀC. Jeong, D. G. Park, I. S. Lee, S. I. Yang, K.ꢀH. Ahn,
J. Mater. Chem., 2009, 19, 97.
13. M. Ohsumi, T. Fukaminato, M. Irie, Chem. Commun.,
2005, 3921.
17. M. M. Krayushkin, D. V. Pashchenko, B. V. Lichitskii, T. M.
Valova, Yu. P. Strokach, V. A. Barachevskii, Zh. Org. Khim.,
2006, 42, 1827 [Russ. J. Org. Chem. (Engl. Transl.), 2006,
42, 1816].
14. C. Fan, S. Pu, G. Liu, T. Yang, J. Photochem. Photobiol. A:
Chem., 2008, 194, 333.
15. C. Fan, S. Pu, G. Liu, T. Yang, J. Photochem. Photobiol. A:
Chem., 2008, 197, 415.
Received July 8, 2010;
in revised form October 27, 2010