Synthesis and photochromic properties of fulgides and fulgimides, 5-alkoxybenzo[b]furan derivatives

Article abstract of DOI:10.1007/s11172-014-0667-7

New heterocyclic fulgides, 3-[1-(5-alkoxy-2-methylbenzo[b]furan-3-yl)ethylidene]-4-(2-propylidene)dihydro-2,5-furandiones, and fulgimides, 1-(2-dimethylaminoethyl)-3-[(5-methoxy-2-methylbenzo[b]furan-3-yl)ethylidene]-4-(2-propylidene)dihydro-2,5-pyrroledi

Full text of DOI:10.1007/s11172-014-0667-7

Russian Chemical Bulletin, International Edition, Vol. 63, No. 8, pp. 1780—1784, August, 2014
1780
Synthesis and photochromic properties of fulgides and fulgimides,
5ꢀalkoxybenzo[b]furan derivatives*
V. P. Rybalkin,a N. I. Makarova,b S. Yu. Pluzhnikova,b L. L. Popova,b A. V. Metelitsa,b
V. A. Bren´,b and V. I. Minkina,b
a Southern Research Center, Russian Academy of Sciences,
41 ul. Chekhova, 344006 Rostov on Don, Russian Federation
bResearch Institute of Physical and Organic Chemistry, Southern Federal University,
194/2 prosp. Stachki, 344090 Rostov on Don, Russian Federation.
Eꢀmail: dubon@ipoc.rsu.ru
New heterocyclic fulgides, 3ꢀ[1ꢀ(5ꢀalkoxyꢀ2ꢀmethylbenzo[b]furanꢀ3ꢀyl)ethylidene]ꢀ4ꢀ(2ꢀ
propylidene)dihydroꢀ2,5ꢀfurandiones, and fulgimides, 1ꢀ(2ꢀdimethylaminoethyl)ꢀ3ꢀ[(5ꢀmethꢀ
oxyꢀ2ꢀmethylbenzo[b]furanꢀ3ꢀyl)ethylidene]ꢀ4ꢀ(2ꢀpropylidene)dihydroꢀ2,5ꢀpyrroledione and
1ꢀbenzylꢀ3ꢀ[(5ꢀmethoxyꢀ2ꢀmethylbenzo[b]furanꢀ3ꢀyl)ethylidene]ꢀ4ꢀ(2ꢀpropylidene)dihydroꢀ
2,5ꢀpyrroledione, were synthesized. Electron spectroscopy and 1H NMR spectroscopy were
used to establish that all the compounds obtained have Zꢀconfiguration and exhibit photoꢀ
chromic properties with high stability to photodegradation in solutions. Cyclic photoisomers of
fulgides possess fluorescent properties and thermal stability.
Key words: benzo[b]furan, fulgide, fulgimide, synthesis, photochromism.
Scheme 1
Bistable photochromic compounds, among which hetꢀ
erocyclic fulgides and fulgimides are the most promising,
attract attention as materials for molecular electronics deꢀ
vices,1 since they are characterized by thermal stability of
both the initial and the photoinduced forms and high reꢀ
sistance to photodegradation.2—6
The practical use of these molecular switches is broadꢀ
ened due to the presence of additional properties, such as
fluorescence of the initial7 or the photo form.8,9 A possiꢀ
bility to form magnetoactive10 or supramolecular strucꢀ
tures,11 including nanoaggregates and Langmuir—Blodgett
films, is also important.12
In the present work, we synthesized new (5ꢀalkoxyꢀ
benzo[b]furanꢀ3ꢀyl)fulgides and (5ꢀmethoxybenzo[b]ꢀ
furanꢀ3ꢀyl)fulgimides in order to search for molecular
switches with the fluorescent colored form.
R = Me (a), C6H13 (b), C16H33 (c)
The Stobbe condensation of acetylbenzofurans 2a—c
with diethyl isopropylidenesuccinate in THF in the presꢀ
ence of sodium hydride led to the corresponding monoꢀ
esters of substituted diethylidenesuccinic acids 3a—c, hyꢀ
drolysis of which with alcoholic alkali and subsequent cyꢀ
clization of diacids 4a—c assisted by acetic anhydride leads
to fulgides 5a—c (Scheme 2).
Fulgimides 6a,b were synthesized by the reaction of
fulgide 5a with amines and subsequent cyclization using
hexamethyldisilazane with zinc chloride13 (Scheme 3).
The structures of fulgides 5a—c and fulgimides 6a,b were
established by IR spectroscopy and 1H NMR spectroscopy.
Results and Discussion
The condensation of 1,4ꢀbenzoquinone and acetylacꢀ
etone leads to 3ꢀacetylꢀ5ꢀhydroxyꢀ2ꢀmethylbenzo[b]furan
(1). The alkylation of the sodium salt of the latter with
alkyl halides in ethanol or dimethyl sulfate in dioxane
gives 3ꢀacetylꢀ5ꢀalkoxyꢀ2ꢀmethylbenzo[b]furans 2a—c
(Scheme 1).
* Based on the materials of the XI International Seminar on
Magnetic Resonance (Spectroscopy, Tomography, and Ecology)
(September 9—14, 2013, Rostov on Don).
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1780—1784, August, 2014.
1066ꢀ5285/14/6308ꢀ1780 © 2014 Springer Science+Business Media, Inc.

Photochromism of the fulgides and fulgimides
Russ.Chem.Bull., Int.Ed., Vol. 63, No. 8, August, 2014
1781
Scheme 2
Scheme 3
The IR spectra of fulgides 5a—c exhibit characteristic
vibration bands of two exocyclic carbonyl groups at
1786—1749 and 1818—1799 cm–1 attributable to the subꢀ
1
stituted diethylidenesuccinic anhydride. Their H NMR
spectra contain highꢀfield signals of the alkoxy group and
four alkyl groups and lowꢀfield signals of three aromatic
hydrogen atoms. The absence in the 1H NMR spectrum of
the signals of one of the methyls of the isopropylidene
fragment in the region  1 indicates the Zꢀconfiguration
of fulgides 5a—c with respect to the heterylethylidene douꢀ
ble bond structurally unprepared to the photoꢀinitiated
electrocyclic reaction.4
The IR spectra of fulgimides 6a and 6b exhibit characꢀ
teristic vibration bands of the atoms of the C=O valent
bonds of the pyrroleꢀ2,5ꢀdione ring in the regions 1700,
1691 cm–1 and 1750, 1747 cm–1, respectively, that conꢀ
firms the presence of substituted diethylidenesuccinylimꢀ
ide fragment.
The 1H NMR spectra of solutions of fulgimides of the
benzo[b]furan series 6a,b in deuterochloroform exhibit the
highꢀfield four threeꢀproton singlets (two isopropylidene
methyls and two methyl groups of the benzofuranylethꢀ
ylidene fragment), a threeꢀproton singlet of the methoxy
group ( ~3.8.), and multiplets of substituents at the nitroꢀ
gen atom of the pyrroledione fragment: for fulgimide 6a,
these are two threeꢀproton multiplets and a sixꢀproton
singlet of the dimethylamino group; for fulgimide 6b, two
doublets (ABꢀsystem) of the benzyl methylene group are
observed in the region  4.6. Signals of three aromatic
protons of the benzofuran fragment are found in the lowꢀ
field of these spectra in the region  6.7—7.3. The absence
of the signals for the methyl group of the isopropylidene
fragment in the region  1, like in the case of fulgides,
indicates the Zꢀconfiguration of the synthesized fulgꢀ
R´ = CH2CH2NMe2 (a), CH2Ph (b)
imides 6a,b. The presence of the ABꢀsystem of the benzyl
methylene protons indicates chirality of these molecules
with a high barrier of racemization.
The electron absorption spectra (EAS) of solutions of
fulgides 5a—c and fulgimides 6a,b in toluene (Zꢀisomer,
Scheme 4) are characterized by the presence of the longꢀ
wavelength absorption bands with the maxima at 344 (5a),
346 (5b,c), 326 (6a), 330 nm (6b) and the molar extincꢀ
tion coefficients in the maxima of 9300, 9200, 9150, 7170,
and 8230 L mol–1 cm–1, respectively. These compounds
do not possess fluorescent properties at ~20 C.
When irradiated with UV light (365 nm), solutions of
fulgides 5a—c and fulgimides 6a,b acquire color, which is

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Rybalkin et al.
Scheme 4
5: X = O, R = Me (a), C6H13 (b), C16H33 (c)
6: X = NR´, R = Me, R´= CH2CH2NMe2 (a), CH2Ph (b)
accompanied by the appearance of the bands with the
maxima at 500 (5a—c), 488 (6a), or 494 nm (6b) in the
visible region of the EAS characteristic of cyclic isomers C
(see Scheme 4).5,9,14 A typical transformation of EAS of
fulgides 5 and fulgimides 6 upon exposure to UV light is
shown in Fig. 1 for fulgide 5c as an example.
The cyclic forms C of fulgides 5 and fulgimides 6 posꢀ
sess high thermal stability: at ~20 C, the reverse dark
reaction C  E was not observed over 48 h.
Unlike fulgimides 6, cyclic isomers C of fulgides under
study in solutions in toluene possess a weak fluorescence
with the maxima at 603 (5a) and 608 nm (5b,c) (see Fig. 1).
The exposure of the colored solutions to visible light
(546 nm) causes their bleaching as a result of the reverse
ring opening photoreaction C  E.
A prolonged UV irradiation of fulgides and fulgimides
does not lead to a complete conversion to the colored
form because of the overlap of absorption bands S0  S2 of
cyclic isomers C with absorption bands of the S0  S1
transition of the open Eꢀ and Zꢀisomers.5,14 Since there
are a reverse recyclization photoreaction C  E and
Z/Eꢀphotoisomerization characteristic of fulgides and
fulgimides, a photostationary state is reached after UV
irradiation, which includes Eꢀ, Zꢀ, and Cꢀisomeric forms.
A subsequent full photobleaching of the solution with visꢀ
ible light leads to a mixture of only Eꢀ and Zꢀisomers, and
the initial spectrum (Zꢀisomer) is not restored after the
bleaching.
Fulgides 5a—c and fulgimides 6a,b are characterized
by stability to photodegradation. Upon repetition of ten
cycles photocoloring—photobleaching of the toluene soluꢀ
tions of these compounds, for example, compound 6b
(Fig. 2), no decrease of optical density in the maximum of
the longꢀwavelength absorption band of cyclic Cꢀform in
the photostationary state was observed.
In conclusion, we synthesized new photochromic
(5ꢀalkoxybenzo[b]furanꢀ3ꢀyl)fulgides and (5ꢀmethoxyꢀ2ꢀ
methylbenzo[b]furanꢀ3ꢀyl)fulgimides, which are characꢀ
terized by thermal stability of photoinduced cyclic forms.
Fulgides, as compared to fulgimides, possess more longꢀ
wavelength absorption by both the initial (Z) and the
photoinduced cyclic (C) isomeric forms. Variation of alkyl
A (arb. units)

2
0.20
A (arb. units)
0.5
Ifl (arb. units)
0.15
0.10
0.05
0
0.8
0.6
0.4
0.2
0.4
0.3
0.2
0.1
0
15
1
16

1
0
2
4
6
8
10
n
0
Fig. 2. Changes in the optical density of a toluene solution
(c = 4.5•10–5 mol L–1, l = 1 cm, T = 293 K) of fulgimide 6b in
the absorption maximum of the Cꢀform (494 nm) upon repetiꢀ
300
400
500
600
700 /nm
Fig. 1. Electron absorption spectra (1—15) of a solution of fulgide
5c in toluene (c = 4.5•10–5 mol L–1, l = 1 cm, T = 293 K) upon
exposure to the light with  = 365 nm recorded every 1 min and
fluorescence spectrum (ex = 500 nm) (16) of the cyclic Cꢀisomer.
tion of the coloring (exposure to the light with  = 365 nm for
1
18 min)—bleaching (exposure to the light with  = 546 nm for
2
24 min) cycles; n is the number cycles.

Photochromism of the fulgides and fulgimides
Russ.Chem.Bull., Int.Ed., Vol. 63, No. 8, August, 2014
1783
3ꢀAcetylꢀ5ꢀhexadecyloxyꢀ2ꢀmethylbenzo[b]furan (2c) was
obtained similarly to 2b from compound 1 and 1ꢀbromohexaꢀ
decane. The yield was 55%, m.p. 85 C (from ethanol). Found (%):
C, 78.33; H, 10.17. C27H42O3. Calculated (%): C, 78.21; H, 10.21.
IR, /cm–1: 1665 (C=O). 1H NMR (CDCl3), : 0.85—0.95
(m, 3 H, Me); 1.10—1.85 (m, 28 H, CH2); 2.59, 2.74 (both s,
3 H each, Me); 3.99 (t, 2 H, CH2, J = 6.6 Hz); 6.86 (dd, 1 H,
CH arom., J1 = 8,7 Hz, J2 = 2.4 Hz); 7.29 (d, 1 H, CH arom.,
J = 8.7 Hz); 7.43 (d, 1 H, CH arom., J = 2.4 Hz).
substituent in the 5ꢀalkoxy group virtually has no effect
on the photochromic and fluorescent properties of fulꢀ
gides synthesized. Thermal stability and luminescent propꢀ
erties of the colored form of fulgides allow us to considꢀ
er them as molecular switches with fluorescent signal
function.
Experimental
(2Z)ꢀ2ꢀ[1ꢀ(5ꢀMethoxyꢀ2ꢀmethylbenzo[b]furanꢀ3ꢀyl)ethylꢀ
idene]ꢀ3ꢀ(2ꢀpropylidene)butanedioic acid (4a). A solution of
benzofuran 2a (2.04 g, 0.01 mol) and diethyl isopropylidenesucꢀ
cinate (2.8 g, 0.013 mol) in THF (20 mL) was added to a suspenꢀ
sion of NaH (0.7 g, 0.03 mol) in THF (10 mL). After a drop of
methanol was added, a characteristic crimson color appeared
and evolution of hydrogen began. The reaction mixture was alꢀ
lowed to stand until hydrogen stopped to evolve and then for
additional 15 h. The solution, which acquired a brown color, was
diluted with water (170 mL), impurities were extracted with diꢀ
ethyl ether. The aqueous layer was acidified with 10% aqueous
HCl to pH 1. An oil formed was extracted with diethyl ether.
The ether was evaporated on a rotary evaporator. Monoethyl
ester 3a, obtained as an oil, was refluxed for 4 h with 10% КOH
in methanol (20 mL). After evaporation of methanol, the reacꢀ
tion mixture was diluted with water to the volume of 200 mL and
acidified with 10% aq. HCl to pH 1. A precipitate of diacid 4a
was filtered off, washed with methanol, and recrystallized from
toluene. The yield was 1.6 g (46.5%), m.p. 240 C (with decomp.).
Found (%): C, 66.39; H, 5.66. C19H20O6. Calculated (%): C, 66.27;
IR spectra were recorded on a Varian Excalibur 3100 FTꢀIR
spectrometer, 1H NMR spectra were recorded on a Varian Uniꢀ
tyꢀ300 spectrometer (300 MHz) in CDCl3, using residual signals
of CHCl3 ( 7.25) as the reference. Electron absorption spectra
were obtained on a Cary 100 spectrophotometer (Varian), fluoꢀ
rescence spectra were obtained on a Varian Eclipse spectrofluoriꢀ
meter. Solutions under study were exposed to the radiation of
a DRShꢀ250 mercury lamp with a kit of interference light filters
for selection of the mercury spectrum lines in a quartz cell (l = 1 cm).
3ꢀAcetylꢀ5ꢀhydroxyꢀ2ꢀmethylbenzo[b]furan (1). Anhydrous
ZnCl2 (45 g, 0.33 mol), anhydrous ethanol (57 mL), and acetylꢀ
acetone (100 mL, 1 mol) were placed into a 250ꢀmL threeꢀneck
flask equipped with a thermometer, a reflux condenser with
a calcium chloride drying tube, and a stirrer. The mixture was
heated with stirring using a boiling water bath until the salt was
dissolved, followed by addition (at the same temperature) in
portions of 1,4ꢀbenzoquinone (35.5 g, 0.33 mol) and heating in
the water bath for 40 min. Then, the mixture was cooled,
a precipitate formed was filtered off, washed with cold ethanol,
dried in air, and recrystallized from ethanol. The yield was 61%,
m.p. 240 C with decomp. (cf. Ref. 14: m.p. 234—235 C).
3ꢀAcetylꢀ5ꢀmethoxyꢀ2ꢀmethylbenzo[b]furan (2a). A mixture
of compound 1 (19.02 g, 0.1 mol), 2 M solution of NaOH (100 mL),
dioxane (50 mL), and dimethyl sulfate (20.8 mL, 0.22 mol) was
stirred for 2 h at ~20 C. Then, the reaction mixture was poured
into iceꢀcold water (150 mL) and was allowed to stand for 12 h in
a refrigerator. A precipitate formed was filtered off, washed with
cold water until neutrality, dried in air, and recrystallized from
butanol. The yield was 17.3 g (81%), m.p. 90 C (cf. Ref. 15: m.p.
44—45 C). IR, /cm–1: 1651 (C=O). 1H NMR (CDCl3), : 2.59,
2.74 (both s, 3 H each, Me); 3.86 (s, 3 H, OMe); 6.86 (dd, 1 H,
CH arom., J1 = 9.0 Hz, J2 = 2.7 Hz); 7.30 (d, 1 H, CH arom.,
J = 9.0 Hz); 7.43 (d, 1 H, CH arom., J = 2.7 Hz).
3ꢀAcetylꢀ5ꢀhexyloxyꢀ2ꢀmethylbenzo[b]furan (2b). Comꢀ
pound 1 (3.8 g, 0.02 mol) and nꢀhexyl iodide (3.24 mL, 0.022 mol)
were sequentially added to a solution of sodium ethylate preꢀ
pared from Na (0.58 g, 0.025 mol) and anhydrous ethanol
(15 mL). The reaction mixture was refluxed for 30 min (a preꢀ
cipitate partially dissolved), cooled, and diluted with water
(250 mL). An oil formed was extracted with diethyl ether, the
ether was evaporated, and the residue was purified by column
chromatography (silica gel, chloroform). A colorless oil of hexylꢀ
oxybenzofuran 2b obtained after evaporation of the solvent was
crystallized by treatment with light petroleum. The yield was
3.83 g (70%), colorless crystals (from butanol), m.p. 52—53 C.
Found (%): C, 74.23; H, 8.14. C17H22O3. Calculated (%):
C, 74.42; H, 8.08. IR, /cm–1: 1664 (C=O). 1H NMR (CDCl3),
: 0.85—0.95 (m, 3 H, Me); 1.25—1.85 (m, 8 H, CH2); 2.59,
2.74 (both s, 3 H each, Me); 3.99 (t, 2 H, CH2, J = 6.6 Hz); 6.86
(dd, 1 H, CH arom., J1 = 8.7 Hz, J2 = 2.4 Hz); 7.29 (d, 1 H,
CH arom., J = 8.7 Hz); 7.43 (d, 1 H, CH arom., J = 2.4 Hz).
1
H, 5.8. IR, /cm–1: 3300—2400 (OH), 1685 (C=O). H NMR
(CDCl3), : 1.93, 1.97, 2.23, 2.33 (all s, 3 H each, Me); 3.99 (s, 3 H,
OMe); 6.74 (m, 2 H, CH arom.); 7.20 (m, 1 H, CH arom.).
(3Z)ꢀ3ꢀ[1ꢀ(5ꢀMethoxyꢀ2ꢀmethylbenzo[b]furanꢀ3ꢀyl)ethylꢀ
idene]ꢀ4ꢀ(2ꢀpropylidene)dihydroꢀ2,5ꢀfurandione (5a). A solution
of diacid 4a (1.6 g, 4.7 mmol) in acetic anhydride (1 mL) was
refluxed for 5 min and cooled. Crystals of 5a were filtered off,
washed with methanol, and recrystallized. The yield was 63%,
m.p. 164 C, colorless crystals (from butanol). Found (%):
C, 69.70; H, 5.37. C19H18O5. Calculated (%): C, 69.93; H, 5.56.
IR, /cm–1: 1810, 1756 (C=O). 1H NMR (CDCl3), : 2.04,
2.28, 2.36, 2.46 (all s, 3 H each, Me); 3.78 (s, 3 H, OMe); 6.77—6.85
(m, 2 H, CH arom.); 7.32 (m, 1 H, CH arom.).
(2Z)ꢀ2ꢀ[1ꢀ(5ꢀHexyloxyꢀ2ꢀmethylbenzo[b]furanꢀ3ꢀyl)ethylꢀ
idene]ꢀ3ꢀ(2ꢀpropylidene)butanedioic acid (4b) was obtained simiꢀ
larly to acid 4a. The yield was 11.4%, m.p. 205 C (from toluꢀ
ene). Found (%): C, 69.41; H, 7.18. C24H30O6. Calculated (%):
C, 69.55; H, 7.30. IR, /cm–1: 3300—2400 (OH), 1685 (C=O).
1H NMR (CDCl3), : 0.80—1.00 (m, 3 H, Me); 1.20—2.00 (m, 8 H,
CH2); 1.93, 1.97, 2.23, 2.33 (all s, 3 H each, Me); 3.90 (t, 2 H,
OCH2, J = 6.0 Hz); 6.64—6.80 (m, 2 H, CH arom.); 7.20 (m, 1 H,
CH arom.); 11.5—12.1 (br.s, 2 H, OH).
(3Z)ꢀ3ꢀ[1ꢀ(5ꢀHexyloxyꢀ2ꢀmethylbenzo[b]furanꢀ3ꢀyl)ethylꢀ
idene]ꢀ4ꢀ(2ꢀpropylidene)dihydroꢀ2,5ꢀfurandione (5b) was obꢀ
tained similarly to compound 5a. The yield was 82%, colorless
crystals, m.p. 103 C (from butanol). Found (%): C, 72.89; H, 6.91.
C24H28O5. Calculated (%): C, 72.71; H, 7.12. IR, /cm–1
:
3300—2400 (OH), 1818—1763 (C=O). 1H NMR (CDCl3),
: 0.85—0.94 (m, 3 H, Me); 1.28—1.50 (m, 6 H, CH2); 1.68—1.81
(m, 2 H, CH2); 2.04, 2.27, 2.35, 2.46 (all s, 3 H each, Me); 3.93
(t, 2 H, OCH2, J = 6.6 Hz); 6.78—6.86 (m, 2 H, CH arom.);
7.30 (m, 1 H, CH arom.).

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Rybalkin et al.
(2Z)ꢀ2ꢀ[1ꢀ(5ꢀHexadecyloxyꢀ2ꢀmethylbenzo[b]furanꢀ3ꢀyl)ꢀ
ethylidene]ꢀ3ꢀ(2ꢀpropylidene)butanedioic acid (4c) was obtained
similarly to acid 4a from benzofuran 2c. The yield was 25%,
colorless crystals, m.p. 174 C (from toluene). Found (%): C, 73.44;
H, 8.90. C34H50O6. Calculated (%): C, 73.61; H, 9.08. IR,
/cm–1: 3300—2400 (OH), 1685 (C=O). 1H NMR (CDCl3),
: 0.85—0.95 (m, 3 H, Me); 1.10—1.80 (m, 28 H, CH2); 1.92, 1.96,
2.23, 2.33 (all s, 3 H each, Me); 3.89 (t, 2 H, OCH2, J = 6.3 Hz);
6.60—6.80 (m, 2 H, CH arom.); 7.20 (m, 1 H, CH arom.);
11.5—12.1 (br.s, 2 H, OH).
Specialists of the Innovative Russia in 2009—2013 (Agreeꢀ
ment No. 14.A18.21.0796) and the Ministry of Education
and Science of the Russian Federation (the Basic Part of
the State Assignment in the Academic Area for the Reꢀ
search Institute of Physical and Organic Chemistry of the
Southern Federal University).
References
(3Z)ꢀ3ꢀ[1ꢀ(5ꢀHexadecyloxyꢀ2ꢀmethylbenzo[b]furanꢀ3ꢀyl)ꢀ
ethylidene]ꢀ4ꢀ(2ꢀpropylidene)dihydroꢀ2,5ꢀfurandione (5c) was
obtained similarly to compound 5a. The yield was 73%, colorꢀ
less crystals, m.p. 80 C (from butanol). Found (%): C, 75.91;
H, 8.90. C34H48O5. Calculated (%): C, 76.08; H, 9.01. IR,
/cm–1: 1818, 1785, 1761 (C=O). 1H NMR (CDCl3), : 0.83—0.88
(m, 3 H, Me); 1.10—1.80 (m, 28 H, CH2); 2.04, 2.27, 2.35, 2.46
(all s, 3 H each, Me); 3.92 (t, 2 H, OCH2, J = 6.6 Hz); 6.77—6.86
(m, 2 H, CH arom.); 7.31 (m, 1 H, CH arom.).
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(Engl. Transl.), 2006, 42, 1861 [Zh. Org. Khim., 2006, 1869].
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4645—4653.
(3Z)ꢀ1ꢀ(2ꢀDimethylaminoethyl)ꢀ3ꢀ[(5ꢀmethoxyꢀ2ꢀmethylꢀ
benzo[b]furanꢀ3ꢀyl)methylidene]ꢀ4ꢀ(2ꢀpropylidene)dihydroꢀ2,5ꢀ
pyrroledione (6a). 1,1ꢀDimethylethylenediamine (0.184 mL,
1.7 mmol) in benzene (2 mL) was added dropwise to a solution
of fulgide 5a (0.55 g, 1.7 mmol) in benzene (8 mL) with stirring
and the mixture was stirred for 1 h at ~20 C. Then, anhydrous
zinc chloride (0.235 g, 1.7 mmol) was added to the reaction
mixture in one portion; the mixture was heated to 80 C and
hexamethyldisilazane (0.55 mL, 3.5 mmol) in benzene (3.5 mL)
was added dropwise over 10 min with stirring. The reaction mixꢀ
ture was refluxed with stirring for another 6 h and cooled, folꢀ
lowed by addition of water (20 mL) and aqueous ammonium to
рH 8, then the mixture was thoroughly shaken and the organic
layer was separated. The solvent was evaporated on a rotary
evaporator, residual water was removed by azeotropic drying
with benzene. A brown oil obtained was purified by chromatoꢀ
graphy on silica gel (eluent methanol). After evaporation of the
solvent, the yield of fulgimide 6a was 0.36 g (53.9%), colorless
crystals, m.p. 99—100 C (from methanol). Found (%): C, 69.53;
H, 7.27; N, 6.89. C23H28N2O4. Calculated (%): C, 69.68; H, 7.12;
N, 7.07. IR, /cm–1: 1750, 1700 (C=O). 1H NMR (CDCl3),
: 2.00, 2.20, 2.36, 2.45 (all s, 3 H each, Me), 2.23 (s, 6 H, NMe2),
2.40—2.47 (m, 2 H, NCH2); 3.55—3.63 (m, 2 H, NCH2);
3.81 (s, 3 H, OMe); 6.77—6.84 (m, 2 H arom.); 7.18—7.34
(m, 1 H arom.).
8. Y .C. Liang, A. S. Dvornikov, P. M. Rentzepis, Macroꢀ
molecules, 2002, 35, 9377.
9. A. V. Metelitsa, O. T. Lyashik, S. M. Aldoshin, O. A. Kosiꢀ
na, N. V. Volbushko, E. A. Medyantseva, M. I. Knyazhanꢀ
sky, V. I. Minkin, A. J. Atovmyan, Chem. Heterocycl. Compd.
(Engl. Transl.), 1990, 36, 28 [Khim. Geterotsikl. Soedin.,
1990, 33].
10. M. A. Halcrow, Chem. Soc. Rev., 2008, 37, 278
11. S. M. Aldoshin, Russ. Chem. Bull. (Int. Ed.), 2008, 57, 718
[Izv. Akad. Nauk, Ser. Khim., 2008, 704].
12. E. V. Korobkova, O. A. Raitman, O. A. Fedorova, V. V.
Arslanov, Struktura i dinamika molekulyarnykh sistem [Strucꢀ
ture and Dynamics of Molecular Systems], 2007, 1, 432
(in Russian).
13. Y. C. Liang, A. S. Dvornikov, P. M. Rentzepis, J. Mater.
Chem., 2000, 33, 2477.
(3Z)ꢀ1ꢀBenzylꢀ3ꢀ[(5ꢀmethoxyꢀ2ꢀmethylbenzo[b]furanꢀ3ꢀ
yl)methylidene]ꢀ4ꢀ(2ꢀpropylidene)dihydroꢀ2,5ꢀpyrroledione (6b)
was obtained similarly to compound 6a from fulgide 5b and
benzylamine. The yield was 29%, colorless crystals, m.p. 95—96 C
(from benzene). Found (%): C, 74.93; H, 5.87; N, 3.49. C26H25NO4.
Calculated (%): C, 75.16; H, 6.06; N, 3.37. IR, /cm–1: 1747,
14. S. K. Balenko, N. I. Makarova, V. P. Rybalkin, E. N. Shepeꢀ
lenko, L. L. Popova, V. V. Tkachov, S. M. Aldoshin, A. V.
Metelitsa, V. A. Bren´, V. I. Minkin, Russ. Chem. Bull.
(Int. Ed.), 2010, 59, 954 [Izv. Akad. Nauk, Ser. Khim.,
2010, 932].
15. G. S. Gadaginamath, R. R. Kavali, S. R. Pujar, Synth. Comꢀ
mun., 2003, 33, 2285.
1
1691 (C=O). H NMR (CDCl3), : 1.96, 2.18, 2.31, 2.43 (all s,
3 H each, Me); 3.77 (s, 3 H, OMe); 4.57, 4.65 (both d, 1 H each,
NCH2, J = 14.1 Hz); 6.76—6.90 (m, 2 H arom.); 7.18—7.37
(m, 6 H arom.).
This work was financially supported by the Federal
Target Program "Scientific and ScientificꢀPedagogical
Received November 27, 2013;
in revised form March 25, 2014