7-Nitro- and 7-aminosubstituted spiropyrans of 1-benzothieno[3,2-b]pyrrole

Article abstract of DOI:10.1016/j.dyepig.2009.06.007

Amino and nitro derivatives of spiropyrans based on 1-benzothieno[3,2-b]pyrrole were synthesized employing an efficient method for the reduction of nitro group in thienopyrroles and spiropyrans. Novel bi-functional compounds, containing salicylideneanilin

Full text of DOI:10.1016/j.dyepig.2009.06.007

Dyes and Pigments 84 (2010) 19–24
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7-Nitro- and 7-aminosubstituted spiropyrans of 1-benzothieno[3,2-b]pyrrole
,
a
a
a
Valerii Z. Shirinian a , Alexey A. Shimkin , Arthur K. Mailian , Dmitry V. Tsyganov ,
*
Leonid D. Popov b, Mikhail M. Krayushkin a
a N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky prosp., 47, 119991 Moscow, Russian Federation
b Southern Federal University, 344104, Rostov-on-Don, str. B. Sadovaya 105, Russian Federation
a r t i c l e i n f o
a b s t r a c t
Article history:
Amino and nitro derivatives of spiropyrans based on 1-benzothieno[3,2-b]pyrrole were synthesized
employing an efficient method for the reduction of nitro group in thienopyrroles and spiropyrans. Novel
bi-functional compounds, containing salicylideneaniline and dithienylethene fragments, along with
spiropyran were prepared from the aminospiropyran derivative.
Received 5 May 2009
Received in revised form
16 June 2009
Accepted 18 June 2009
Available online 27 June 2009
Ó 2009 Elsevier Ltd. All rights reserved.
Keywords:
Spiropyrans
Benzothienopyrroles
Bi-functional compounds
Salicylideneanilines
Dithienylethenes
1. Introduction
studied their spectral properties [8,9]. In this work, we present the
synthesis of nitro-substituted spiropyrans of benzothienopyrrole
The design and synthesis of organic photochromic compounds
is an intense research area because of their potential applications
for optoelectronic devices, including photoswitching materials and
optical storage elements [1–4], that make the development of
synthetic methods of photochromic compounds and the investi-
gation of influence of their structure on spectral, physical and
applied properties urgently needed.
series and the development of regioselective method for the
reduction of nitro- to amino group in spiropyran and thieno-
pyrroline systems. Early unknown hybrid photochromic
compounds are synthesized by the reaction of aminospiropyran
with salicylic aldehydes or dithienylmaleic anhydride.
2. Results and discussion
One of promising classes of photochromic organic dyes are
spiropyran derivatives which undergo photo-transformation under
UV-light irradiation leading to formation of metastable mero-
cyanine dyes. The most known photochromic spiropyrans belong to
indole derivatives.
For the preparation of nitrospiropyrans 5a–c early described
method of synthesis of thienopyrrolinespiropyrans was used
[10,11]. As starting material benzothienone
1 was utilized
(Scheme 1). The only difference of this synthesis is the using of
ethyl acetate as solvent in hydrazone hydrochloride preparation
stage because of very low solubility of hydrazone 2 in benzene.
When in this reaction 3,5-dinitrosalicylic aldehyde was used the
open form of spiropyran, the merocyanine 5d was isolated that is in
agreement with published data [12] (Scheme 2). The 1H NMR
spectrum of this compound showed signals of the CMe2 group as
a singlet, thus confirming the existence of a non-cyclic structure.
Aminospiropyrans have attracted much attention not only for
the elucidation of the influence of amino group on the photo- and
thermochromic properties but also as potential intermediates for
the preparation of various derivatives. To prepare amino-
spiropyrans, two synthetic routes were explored; firstly, the nitro
O
+
hν1
N
N
R
O
R
Δ
hν2 or
colorless
colored
Recently, we have developed an efficient method for the
synthesis of photochromic spiro compounds [5,6] and merocyanine
dyes [7] based on close analogues of indole – thienopyrroles, and
* Corresponding author. fax: þ7 495 1376939.
E-mail address: shir@ioc.ac.ru (V.Z. Shirinian).
group in thienopyrrolenine
3 was reduced and subsequent
0143-7208/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.dyepig.2009.06.007

20
V.Z. Shirinian et al. / Dyes and Pigments 84 (2010) 19–24
O2N
O2N
O2N
O
N NH2
N
i
iii
ii
S
S
S
1
2
3
TfO-
R1
O2N
N+
O2N
R2
N
S
iv
O
R3
S
4
5a-c
5a, R1 = R3 = H, R2 = NO2; 5b, R1, R2 = (CH)4,
R3 = H; 5c, R1 = R2 = H, R3 = OMe
i, NH2NH2*H2O, EtOH; ii, 1. HClg, EtOAc; 2. CH3C(O)CH(CH3)2, C6H6;
iii, MeOTf, CH3CN; iv, aldehyde, piperidine, EtOH
Scheme 1.
This convinced us to use route B (Scheme 3). However, there is
no published literature concerning the reduction of the nitro group
in the indole part of photochromic spiropyrans although, two
methods for the reduction of nitro group in the pyran fragment of
spiropyran have been reported using hydrogen [13] or hydrazine
hydrate [14] on Raney nickel, and tin chloride dihydrate
(SnCl2$2H2O) [15] in acidic medium.
TfO-
NO2
O
N+
N
O2
i
O2N
N+
NO2
S
S
4
5d
The first method is not acceptable for benzothienopyrrole
derivatives since the thiophene ring is too sensitive to Raney nickel,
and the desulfurization of thiophene ring occurs. Actually, we have
found that the reaction of compound 10 with Raney nickel under
mild conditions leads to desulfurized and reduced spiro compound
11 (Scheme 4). Therefore, Raney nickel could not be applied for the
reduction of thienopyrrole derivatives.
When nitrospiropyran 5b was treated with tin (II) chloride
dihydrate, unexpected results were obtained: azomethine 12a
instead of aminospiropyran 8 was isolated. The structure of
compound 12a was proved both by spectral methods and inde-
pendent synthesis. Apparently, the mechanism of the hybrid
i, 2-hydroxy-3.5-dinitrobenzaldehyde,
piperidine, EtOH
Scheme 2.
alkylation enabled the preparation of the spiropyran derivative
(Scheme 3, route A). The second route involved the synthesis of
nitrospiropyran 5b followed by reduction (Route B).
7-Amino-3H-benzothienopyrrole
6 was synthesised using
various reducing agents (tin dichloride in methanolic solution of
hydrochloric acid, zinc dust in acetic acid, sodium hydrosulfide in
ethanol); optimum results were achieved using an excess of NaHS
in boiling EtOH. Benzothienopyrrole 6 was found to be labile and
decomposed at room temperature, partially being oxidized by
atmospheric oxygen to the starting compound 3.
NiRa
Ph
O
N
N
However, attempts to prepare the methylated salt 7 by meth-
ylation of the aminobenzothienopyrrole 6 with methyltriflate or
methyl iodide in acetonitrile under an argon atmosphere failed,
insofar as it produce an inseparable complex mixture. Obviously,
the reaction proceeds non-regioselectively and leads to the mixture
of products with different degrees of alkylation.
O
S
11
10
Scheme 4.
TfO-
O2N
H2N
N+
Me
2N
N
N
A
S
S
S
7
3
6
B
H2N
Me2
N
O
2N
N
N
N
O
O
O
S
S
S
8
9
5b
Scheme 3.

V.Z. Shirinian et al. / Dyes and Pigments 84 (2010) 19–24
21
H2N
O2N
O2N
H2N
SnCl2
O
O
N
N
i
O
O
N
N
HCl, MeOH
S
S
S
S
5b
8
5b
8
H+
HO
O2N
i, NaSH, EtOH
N+
Scheme 7.
S
OH
N
N+
O2N
method for the reduction of nitro group in thienopyrrole and spi-
ropyran systems has been developed. Novel bi-functional
compounds, containing salicylideneaniline and dithienylethene
fragments, along with spiropyran system, have been prepared
starting from aminospiropyran derivative.
O
S
N
S
12a
Scheme 5.
3. Experimental
compound 12 formation includes Michael-type reaction of amine 8
with second spiropyran molecule activated by acid with subse-
quent elimination of thienopyrrolium salt (Scheme 5).
To test this proposed reaction pathway we have carried out the
reaction of spiropyran 10 with aniline, and the expected product 13
has actually been isolated (Scheme 6). It is significant that in the
literature there is no similar substitution of methylene base in
spiropyran molecule by another nucleophiles.
To exclude the formation of azomethine 12a the reduction
reaction of compound 5b was carried out by sodium hydrosulfide
under basic conditions, and the target aminospiropyran 8 was
obtained in good yield (Scheme 7).
The attempt of alkylation of aminospiropyran 8 with methyl
triflate or methyl iodide led to inseparable salt-like products
instead of dimethylamino derivative 9 (Scheme 3).
3.1. General
1H and 13C NMR spectra were performed on Bruker AM-300 or
WM-250 spectrometers. Mass spectra were obtained on a Kratos
mass spectrometer (70 eV) with direct sample injection into the ion
source. Melting points were measured on a Boetius hot stage and
were not corrected. Column chromatography was performed using
silica gel 60 (70–230 mesh), TLC analysis was conducted on silica
gel 60 F254 plates. Commercially available (Acros, Merck) reagents
and solvents were used. Chromatography products were purchased
from Merck. 5-Nitro-1-benzothiophen-3(2H)-one 1 [18], spiro-
pyran 10 [10] and anhydride 14 [19] were prepared by known
procedures.
To synthesize the hybrid photochromic compounds bearing
spiropyran and salicylideneaniline fragments the aminospiropyran
8 was condensed with different salicylic aldehydes (Scheme 8). The
reaction proceeds in the mixture of ethanol and acetic acid, and the
Schiff’s bases 12a–d were obtained in 35–64% yields.
The formation of diimine 12d was already observed at room
temperature, and therefore the monocondensation product
couldn’t be obtained.
Compound 15 containing the spiropyran and dithienylethene
fragments has been prepared by the reaction of aminospiropyran 8
with dithienylmaleic anhydride 14 under basic conditions. The
anion of compound 8 generated in the first stage by lithium hexa-
methyldisilazide reacts with maleic anhydride 14 giving the hybrid
product 15 in 57% yield (Scheme 9).
The prepared compounds 12a–d and 15 contain two and more
functional groups, and they are of interest for the design of novel
smart materials for optoelectronic application since the salicyli-
denaniline [16], diarylethene [17], and spiropyran [1] fragments are
potential photochromic systems.
3.2. Synthesis of starting compounds
3.2.1. 5-Nitro-1-benzo[b]thiophen-3(2H)-one hydrazone 2
p-Toluenesulfonic acid (0.86 g, 5 mmol) and hydrazine hydrate
(15 mL, 0.3 mol) were added to a stirred solution of benzothiophen-
3-one 1 (9.75 g, 0.05 mol) in ethanol (15 mL). The solution
immediately became dark. The mixture was refluxed for 5 h,
maintained for 10–12 h at room temperature, and the ensuing
precipitate was filtered off and dried in air.
Yellow powder; yield 79%; mp. dec. 160–163 ꢀC (ethanol); 1H
NMR (250 MHz, CDCl3):
d
¼ 4.13 (s, 2H, CH2), 6.88 (br. s, 2H, NH2),
7.52 (d, J ¼ 8.6 Hz, 1H, Harom), 8.00 (dd, J ¼ 2.4, 8.6 Hz, 1H, Harom),
8.08 (d, J ¼ 2.4 Hz, 1H, Harom). MS: m/z (%) ¼ 209 (100) [M]þ, 192
(88) [M ꢁ NH3]þ. Anal. Calcd. (%) for C8H7N3O2S: C, 45.92; H, 3.37;
N, 20.08. Found: C, 46.17; H, 3.71; N, 19.70.
3.2.2. 2,3,3-Trimethyl-7-nitro-3H-[1]benzothieno[3,2-b]pyrrole 3
Hydrogen chloride gas was passed through a cooled to 0 ꢀC
solution of 5-nitro-1-benzo[b]thiophen-3(2H)-one hydrazone 2
(2.0 g, 12 mmol) in ethyl acetate (15 mL) with stirring. The solution
darkened, and a solid precipitated. The precipitate was filtered off,
In summary, early unknown nitrospiropyrans of 1-benzo-
thieno[3,2-b]pyrrole series have been synthesized. An efficient
H2N
N+
[H+]
O
N
N
HCl, EtOH
S
S
HO
O
H
10
13
Scheme 6.

22
V.Z. Shirinian et al. / Dyes and Pigments 84 (2010) 19–24
R
3.3.1. 1,3,3-Trimethyl-60,7-dinitrospiro[2,3-dihydro-1H-
[1]benzothieno[3,2-b]pyrrole-2,20-2H-chromene] 5a
O
Orange powder; yield 74%; mp. 231–232 ꢀC (petrol. ether/
HO
R
H2N
N
HO
benzene). 1H NMR (250 MHz, CDCl3):
d
¼ 1.30 (s, 3H, ½CMe2), 1.36
O
N
O
N
(s, 3H, ½CMe2), 3.11 (s, 3H, NCH3), 5.95 (d, J ¼ 10.5 Hz, 1H, CH), 6.86
(d, J ¼ 8.5 Hz, 1H, Harom), 6.98 (d, J ¼ 10.5 Hz, 1H, CH), 7.89 (d,
J ¼ 8.5 Hz, 1H, Harom), 8.02–8.15 (m, 3H, Harom), 8.67 (d, J ¼ 2.0 Hz,
1H, Harom). MS: m/z (%) ¼ 423 (90) [M]þ, 408 (100) [M–Me]þ. Anal.
Calcd. (%) for C21H17N3O5S: C, 59.57; H, 4.05; N, 9.92. Found: C,
59.37; H, 4.42; N, 9.74.
AcOH, EtOH,
Δ
S
S
8
12a-c
R = 5,6-benzo (a), 5-O2N (b), 4-Et2N (c)
O
O
3.3.2. 1,3,3-Trimethyl-7-nitrospiro[2,3-dihydro-1H-
N
N
[1]benzothieno[3,2-b]pyrrole-2,30-3H-benzo[f]chromene] 5b
N
N
OH
Red powder; yield 53%; mp. 204–205 ꢀC (petrol. ether). 1H NMR
S
S
(250 MHz, CDCl3):
d
¼ 1.34 (s, 3H, ½CMe2), 1.42 (s, 3H, ½CMe2), 3.12
12d
(s, 3H, NMe), 5.89 (d, J ¼ 10.5 Hz, 1H, CH), 7.06 (d, J ¼ 9.2 Hz, 1H,
arom), 7.37 (t, J ¼ 7.9 Hz, 1H, Harom), 7.55 (t, J ¼ 7.9 Hz, 1H, Harom),
Scheme 8.
H
7.61–7.72 (m, 2H, Harom), 7.76 (d, J ¼ 8.5 Hz, 1H, Harom), 7.87 (d,
J ¼ 9.2 Hz, 1H, Harom), 8.03–8.13 (m, 2H, Harom), 8.70 (d, J ¼ 2.0 Hz,
1H, Harom). MS: m/z (%) ¼ 428 (100) [M]þ, 413 (99) [M ꢁ CH3]þ, 398
(99) [M–2CH3]þ, 383 (78) [M – 3 CH3]þ. Anal. Calcd. (%) for
C25H20N2O3S: C, 70.07; H, 4.70; N, 6.54. Found: C, 70.12; H, 4.81; N,
6.69.
washed with cooled ethyl acetate, and dried in air to yield 2.2 g of
hydrazone 2 hydrochloride as pale yellow solid. The product was
used on the next stage without additional purification. 3-Methyl-
butan-2-one (ed. Note: flammable; irritant) (1.54 mL,14 mmol) was
added to a suspension of hydrochloride of benzothiophen-3-one
hydrazone (2.2 g, 11 mmol) in anhydrous benzene (30 mL). The
reaction mixture was refluxed for 2 h during which the precipitate
dissolved. The reaction mixture was cooled, poured into 200 mL of
water and extracted with ethyl acetate (3 ꢂ 50 mL). The organic
fractions were combined, washed with water, and concentrated
under reduced pressure. After solvent evaporation, the residue was
purified by chromatography on silica gel using a 3:1 petroleum
ether/ethyl acetate mixture as the eluent.
3.3.3. 1,3,3-Trimethyl-80-methoxy-7-nitrospiro[2,3-dihydro-1H-
[1]benzothieno[3,2-b]pyrrole-2,20-2H-chromene] 5c
Red powder; yield 71%; mp. 223–225 ꢀC (petrol. ether/benzene).
1H NMR (250 MHz, CDCl3):
d
¼ 1.27 (s, 3H, ½CMe2), 1.39 (s, 3H,
½CMe2), 3.11 (s, 3H, NMe), 3.73 (s, 3H, OMe), 5.77 (d, J ¼ 10.5 Hz,1H,
CH), 6.69–6.75 (M, 1H, Harom), 6.77–6.83 (M, 2H, Harom), 6.86 (d,
J ¼ 10.5 Hz, 1H, CH), 7.85 (d, J ¼ 8.5 Hz, 1H, Harom), 8.07 (dd, J ¼ 2.0,
8.5 Hz, 1H, Harom), 8.66 (d, J ¼ 2.0 Hz, 1H, Harom). MS: m/z (%) ¼ 408
(100) [M]þ, 393 (50) [M–Me]þ. Anal. Calcd. (%) for C22H20N2O4S: C,
64.69; H, 4.94; N, 6.86. Found: C, 64.41; H, 4.75; N, 6.87.
Brown powder; yield 64%. mp. 122–124 ꢀC (ethanol). 1H NMR
(250 MHz, CDCl3):
d
¼ 1.45 (s, 6H, CMe2), 2.37 (s, 3H, CH3), 7.91 (d,
1H, J ¼ 8.8 Hz, Harom), 8.15 (d, 1H, J ¼ 8.8 Hz, Harom), 8.94 (s, 1H,
3.3.4. 2,4-Dinitro-6-[2-(1,3,3-trimethyl-7-nitro-1,3-dihydro-2H-
[1]benzothieno[3,2-b]pyrrol-2-yliden)ethyliden]-2,4-
cyclohexadien-1-one 5d
H
arom). MS: m/z (%) ¼ 260 (100) [M]þ, 245 (22) [M–Me]þ, 219 (80)
[M–MeCN]þ. Anal. Calcd. (%) for C13H12N2O2S: C, 59.98; H, 4.65; N,
10.76. Found: C, 59.80; H, 4.83; N, 10.66.
Dark purple powder; yield 78%; mp. > 350 ꢀC (ethanol). 1H NMR
(300 MHz, DMSO-d6):
d
¼ 1.92 (s, 6H, CMe2), 4.35 (s, 3H, NMe),
8.02–8.71 (m, 5H, Harom), 8.89 (s, 1H, Harom), 9.00 (s, 1H, Harom). MS:
m/z (%) ¼ 468 (25) [M]þ, 453 (42) [M–Me]þ, 274 (38), 259 (100).
Anal. Calcd. (%) for C21H16N4O7S: calc. C, 53.84; H, 3.44; N, 11.96.
Found: C, 53.34; H, 3.50; N, 11.70.
3.3. Preparation of spiropyrans 5a–d (total procedure)
To a solution of 3H-benzothienopyrrole 3 (0.26 g, 1 mmol) in
absolute acetonitrile (5 mL) methyl trifluoromethanesulfonate
(methyltriflate; ed note: Flammable liquid and vapour; moisture
sensitive; severe irritant; incompatible materials with strong acids,
strong oxidants, bases) (0.12 mL, 1.1 mmol) was added. The reaction
mixture was refluxed for 1.5 h and cooled. After evaporation of
solvent absolute ethanol (5 mL), corresponding o-hydroxyaldehyde
(1.0 mmol) and piperidine (0.1 mL, 1.0 mmol) were added to the
residue, and the reaction mixture was refluxed for 3–12 h.
Completion of the reaction was monitored by TLC (eluent petrol.
ether/ethyl acetate 5:1). The products were purified by column
chromatography or recrystallization.
3.4. Synthesis of 7-amino-2,3,3-trimethyl-3H-[1]benzothieno
[3,2-b]pyrrole 6
A
suspension of 7-nitro-3H-benzothienopyrrole 3 (0.26 g,
1 mmol) and sodium hydrosulfide (purity 70%, 0.8 g, 10 mmol) in
ethanol (10 mL) was refluxed for 3 h. The reaction mixture was
cooled, poured into water (100 mL), and extracted with ethyl
acetate (3 ꢂ 20 mL). The extract was filtered through thin layer of
silica gel, and the solvent was evaporated. Yellow viscous oil; yield
S
1. LiN(TMS)2
2. AcOH
O
O
S
O
S
H2N
O
N
S
N
+
N
O
O
3. imidazole,
THF
S
O
S
8
14
15, 57%
Scheme 9.

V.Z. Shirinian et al. / Dyes and Pigments 84 (2010) 19–24
23
78%; 1H NMR (250 MHz, CDCl3):
d
¼ 1.39 (s, 6H, CMe2), 2.31 (s, 3H,
3.11–3.39 (m, 2H, CH2), 4.19–4.31 (m, 1H, CH), 7.17 (d, J ¼ 8.8 Hz, 1H,
Me), 3.77 (br. s, 2H, NH2), 6.72 (dd,1H, J ¼ 2.2, 8.6 Hz, Harom), 7.34 (d,
J ¼ 2.2 Hz, 1H, Harom), 7.55 (d, J ¼ 8.6 Hz, 1H, Harom). MS: m/z
(%) ¼ 230 (100) [M]þ, 215 (30) [M–Me]þ, 189 (27) [M–MeCN]þ.
Anal. Calcd. (%) for C13H14N2S: C, 67.79; H, 6.13; N, 12.16. Found: C,
66.98; H, 6.05; N, 12.32.
H
arom), 7.23–7.56 (m, 7H, Harom), 7.68 (d, J ¼ 8.8 Hz, 1H, Harom), 7.79
(d, J ¼ 8.1 Hz, 1H, Harom), 7.85 (d, J ¼ 8.8 Hz, 1H, Harom). MS: m/z (%)
357 (14) [M]þ, 201 (100), 186 (56), 156 (47). Anal. Calcd. (%) for
C25H27NO: C, 83.99; H, 7.61; N, 3.92. Found: C, 83.34; H, 7.40; N,
3.58.
3.5. The reduction of nitrospiropyran 5b
3.7. The reaction of spiropyran 10 with aniline
A. To a suspension of nitrospiropyran 5b (0.3 g, 0.7 mmol) and
SnCl2$2H2O (1.1 g, 4.9 mmol) in absolute methanol (15 mL)
concentrated hydrochloric acid (0.5 mL) was added. The reaction
mixture was refluxed for 5 h, cooled, poured into water (100 mL),
and to this mixture 5% solution of KOH in water (100 mL) was added.
The obtained blue suspension was extracted with ethyl acetate
(3 ꢂ 50 mL), and combined organic layers were washed with water.
Solvent evaporation gave yellow residue that was purified by
column chromatography (eluent petrol. ether/ethyl acetate4:1), and
0.106 g of 7-{[(2-hydroxy-1-naphthyl)methyliden]amino}-1,3,3-
trimethylspiro[2,3-dihydro-1H-[1]benzothieno[3,2-b]pyrrole-2,30-
3H-benzo[f]chromene] 12a was obtained.
To a solution of spiropyran 10 (50 mg, 0.13 mmol) in ethanol
(3 mL) aniline (0.5 mL, 5.5 mmol) and concentrated hydrochloric
acid (0.1 mL, 1.0 mmol) were added. The reaction mixture was
refluxed for 1 h, cooled, poured into water (50 mL) and extracted
with ethyl acetate (3 ꢂ 10 mL). The extract was washed with water,
and solvent was evaporated. The product 13 was purified by column
chromatography (eluent: petrol. ether/ethyl acetate – 10:1).
Yellow crystals; yield 62%; mp. 91–93 ꢀC (lit. 92 ꢀC [20]). 1H NMR
(250 MHz, CDCl3):
d
¼ 7.09 (d, J ¼ 9.2 Hz, 1H, Harom), 7.28–7.43 (m,
4H, 3HPh þ Harom), 7.46 (d, J ¼ 7.9 Hz, 2H, HPh), 7.53 (t, J ¼ 7.9 Hz, 1H,
H
arom), 7.72 (d, J ¼ 7.9 Hz, 1H, Harom), 7.81 (d, J ¼ 9.2 Hz, 1H, Harom),
8.10 (d, J ¼ 8.5 Hz, 1H, Harom), 9.33 (s, 1H, CH ¼ N), 15.49 (br. s, 1H,
OH). MS: m/z (%) 247 (18) [M]þ, 84 (100).
Yellow powder; yield 55%; mp. 189–191 ꢀC (ethanol). 1H NMR
(250 MHz, CDCl3):
d
¼ 1.35 (s, 3H, ½CMe2), 1.42 (s, 3H, ½CMe2), 3.12
(s, 3H, NMe), 5.92 (d, J ¼ 10.6 Hz, 1H, CH), 7.06–7.16 (m, 2H, Harom),
7.29–7.40 (m, 3H, Harom), 7.48–7.58 (m, 2H, Harom), 7.64 (d,
J ¼ 10.6 Hz, 1H, CH), 7.69 (d, J ¼ 8.8 Hz, 1H, Harom), 7.71–7.79 (m, 3H,
3.8. Preparation of azomethines 12a–d
To a hot solution of aminospiropyran 8 (0.13 g, 0.33 mmol) in
abs. ethanol (2 mL) 0.33 mmol (0.16 mmol for compound 12d) of
corresponding o-hydroxybenzaldehyde and glacial acetic acid (3
drops) were added. The reaction mixture was refluxed until
complete disappearance of starting compounds. The progress of
reaction was monitored by TLC. After completion of reaction, the
reaction mixture was cooled and the precipitate was filtered off,
washed with ethanol and dried in air. The additional amount of
product could be isolated from mother waters by column
chromatography.
H
arom), 7.82 (d, J ¼ 9.2 Hz, 1H, Harom), 7.86 (d, J ¼ 8.4 Hz, 1H, Harom),
8.06 (d, J ¼ 8.8 Hz, 1H, Harom), 8.12 (d, J ¼ 8.4 Hz, 1H, Harom), 9.41 (s,
1H, CH), 15.65 (br. s, 1H, OH). IR (KBr):
n
(cmꢁ1) ¼ 3410 (OH), 2960,
1624, 1464. MS: m/z (%) ¼ 552 (100) [M]þ, 537 (59) [M–Me]þ, 394
(83), 169 (42). Anal. Calcd. (%) for C36H28N2O2S$½H2O: C, 76.98; H,
5.20; N, 4.99. Found: C, 76.87; H, 5.50; N, 5.02.
B. A suspension of nitrospiropyran 5b (1.0 g, 2.3 mmol) and
sodium hydrosulfide (purity 70%,1.9 g, 23 mmol) in ethanol (50 mL)
was refluxed for 3 h. The reaction mixture was cooled, poured into
water (200 mL), and extracted with ethyl acetate (3 ꢂ 20 mL). The
extract was washed with water, filtered through thin layer of silica
gel, and the solvent was evaporated. After purification by column
chromatography (eluent petrol. ether/ethyl acetate 2:1) 0.59 g of 7-
amino-1,3,3-trimethylspiro[2,3-dihydro-1H-[1]benzothieno[3,2-b]
pyrrole-2,30-3H-benzo[f]chromene] 8 was obtained.
3.8.1. 7-{[(2-Hydroxy-1-naphthyl)methyliden]amino}-1,3,
3-trimethylspiro[2,3-dihydro-1H-[1]benzothieno[3,2-b]
pyrrole-2,30-3H-benzo[f]chromene] 12a
The spectral data for this sample agree with same data for the
compound obtained by method 2.5.A. Yield 64%; mp. 190–193 ꢀC
(ethanol).
Light green powder; yield 63%; mp. 93–95 ꢀC (petrol. ether). 1H
NMR (250 MHz, CDCl3):
d
¼ 1.31 (s, 3H, ½CMe2), 1.38 (s, 3H,
½CMe2), 3.02 (s, 3H, NMe), 3.65 (br. s, 2H, NH2), 5.89 (d, J ¼ 10.5 Hz,
3.8.2. 7-{[(2-Hydroxy-5-nitrophenyl)methyliden]amino]-1,3,
3-trimethylspiro}2,3-dihydro-1H-[1]benzothieno[3,2-b]
pyrrole-2,30-3H-benzo[f]chromene] 12b
1H, CH), 6.68 (dd, J ¼ 2.0, 8.5 Hz, 1H, Harom), 7.04–7.16 (m, 2H,
H
arom), 7.35 (t, J ¼ 7.9 Hz, 1H, Harom), 7.47–7.63 (m, 3H, Harom), 7.67
(d, J ¼ 8.9 Hz, 1H), 7.76 (d, J ¼ 7.9 Hz, 1H, Harom), 8.06 (d, J ¼ 8.5 Hz,
Yellow powder; yield 56%; mp. 247–249 ꢀC (ethanol). 1H NMR
1H, Harom). IR (KBr):
n
(cmꢁ1) ¼ 3376, 3452 (NH2). MS: m/z (%) 398
(250 MHz, CDCl3):
d
¼ 1.34 (s, 3H, ½CMe2), 1.41 (s, 3H, ½CMe2), 3.10
(36) [M]þ, 383 (83) [M–Me]þ, 246 (31), 229 (100). Anal. Calcd. (%)
for C25H22N2OS$1½H2O: C, 70.56; H, 5.92; N, 6.58. Found: C, 70.24;
H, 6.11; N, 6.46.
(s, 3H, NMe), 5.90 (d, J ¼ 10.5 Hz, 1H, CH), 7.04–7.13 (m, 2H, Harom),
7.26 (dd, J ¼ 2.0, 8.5 Hz,1H, Harom), 7.36 (t, J ¼ 7.9 Hz,1H, Harom), 7.54
(t, J ¼ 7.9 Hz, 1H, Harom), 7.60–7.79 (m, 4H, Harom), 7.86 (d, J ¼ 8.5 Hz,
1H, Harom), 8.06 (d, J ¼ 8.5 Hz, 1H, Harom), 8.26 (dd, J ¼ 2.6, 9.2 Hz,
1H, Harom), 8.41 (d, J ¼ 2.6 Hz, 1H, Harom), 8.77 (s, 1H, CH), 14.57 (s,
3.6. Reducing desulfuration of spiropyran 10
1H, OH). IR (KBr):
n
(cmꢁ1) ¼ 3450 (OH), 2964, 1620, 1336. MS: m/z
To a suspension of spiropyran 10 (0.2 g, 0.5 mmol) in ethanol
(5 mL) a Raney nickel suspension in ethanol (5 mL, 5 fold excess)
was added, and the reaction mixture was stirred at room temper-
ature for 16 h. The reaction mixture was poured into water (50 mL)
and extracted with ethyl acetate (3 ꢂ 10 mL). The extract was
washed with water and solvent was evaporated. The purification of
the residue by column chromatography (eluent: petrol. ether/ethyl
acetate – 4:1) gave 40 mg of compound 11.
(%) ¼ 547 (100) [M]þ, 532 (63) [M – Me]þ, 502 (27), 398 (29). Anal.
Calcd. (%) for C32H25N3O4S: C, 70.18; H, 4.60; N, 7.67. Found: C,
69.43; H, 4.79; N, 7.54.
3.8.3. 7-{[(2-Hydroxy-4-diethylaminophenyl)methyliden]amino}-
1,3,3-trimethylspiro[2,3-dihydro-1H-[1]benzothieno[3,2-b]pyrrole-
2,30-3H-benzo[f]chromene] 12c
Light brown powder; yield 35%; mp. 132–135 ꢀC (ethanol). 1H
Pinkish powder; yield 21%; mp. 118–121 ꢀC (petrol. ether). 1H
NMR (250 MHz, CDCl3):
½CMe2), 1.40 (s, 3H, ½CMe2), 3.09 (s, 3H, NMe), 3.41 (q, J ¼ 7.2 Hz,
d
¼ 1.22 (t, J ¼ 7.2 Hz, CH2CH3), 1.32 (s, 3H,
NMR (300 MHz, CDCl3):
d
¼ 1.02 (s, 3H, ½CMe2), 1.29 (s, 3H,
½CMe2), 1.56–1.79 (m, 2H, CH2), 2.27–2.41 (m, 5H, NMe þ CH2),
2H, CH2CH3), 5.90 (d, J ¼ 10.5 Hz, 1H, CH), 6.18–6.30 (m, 2H, Harom),

24
V.Z. Shirinian et al. / Dyes and Pigments 84 (2010) 19–24
7.07 (d, J ¼ 8.5 Hz, 1H, Harom), 7.15–7.22 (m, 2H, Harom), 7.35
(t, J ¼ 7.9 Hz, 1H, Harom), 7.54 (t, J ¼ 7.9 Hz, 1H, Harom), 7.58–7.71 (m,
3H, Harom), 7.73–7.80 (m, 2H, Harom), 8.06 (d, J ¼ 8.5 Hz, 1H, Harom),
Calcd. (%) for C41H34N2O3S3: C, 70.46; H, 4.90; N, 4.01. Found: C,
70.79; H, 5.03; N, 3.85.
8.46 (s, 1H, CH). IR (KBr):
n
(cmꢁ1) ¼ 3450 (OH), 2968, 1628, 1584,
4. Conclusions
1520. MS: m/z (%) ¼ 573 (10) [M]þ, 558 (19) [M – Me]þ, 57 (100).
Anal. Calcd. (%) for C36H35N3O2S: C, 75.36; H, 6.15; N, 7.32. Found C,
74.78; H, 5.99; N, 6.72.
Early unknown nitro-substituted spiropyrans of benzothieno-
pyrrole series have been synthesized. It was shown that the
reduction of nitro group in spiropyran system depends strongly on
the reaction conditions: the reduction by tin (II) chloride in acidic
medium leads to bi-functional compound containing salicyliden-
aniline group along with spiropyran system, and the using of
sodium hydrosulfide under basic conditions results in formation
of aminospiropyran, which was utilized for the preparation of
different hybrid compounds.
3.8.4. 2,6-Bis{[(1,3,3-trimethylspiro[2,3-dihydro-1H-
[1]benzothieno[3,2-b]pyrrole-2,30-3H-benzo[f]chromen-7-
ylimino)methyl]-4-methylphenol 12d
Brown powder; yield 46%; mp. 199–202 ꢀC (ethanol). 1H NMR
(250 MHz, CDCl3):
d
¼ 1.33 (s, 6H, ½CMe2), 1.41 (s, 6H, ½CMe2), 2.39
(s, 3H, Me), 3.09 (s, 6H, NMe), 5.90 (d, J ¼ 10.5 Hz, 2H, CH), 7.08 (d,
J ¼ 8.5 Hz, 2H, Harom), 7.24 (dd, J ¼ 2.0, 8.5 Hz, 2H, Harom), 7.36 (t,
J ¼ 7.9 Hz, 2H, Harom), 7.53 (t, J ¼ 7.9 Hz, 2H, Harom), 7.58–7.84 (m,
12H, Harom), 8.06 (d, J ¼ 8.5 Hz, 2H, Harom), 8.91 (br. s, 2H, CH), 14.00
Acknowledgements
(br. s, 1H, OH). IR (KBr):
n
(cmꢁ1) ¼ 3450 (OH), 2960, 1580, 1464.
ESI-MS: m/z (%) 925 (100) [M þ H]þ, 947 (19) [M þ Na]þ, 1872 (14)
[2M þ Na þ H]þ. Anal. Calcd. (%) for C59H48N4O3S2$3H2O: C, 72.37;
H, 5.56; N, 5.72. Found: C, 72.24; H, 5.60; N, 5.57.
This work was supported by the Russian Foundation for Basic
Research (grant No. 08-03-00865-a).
3.9. Synthesis of 3,4-Bis(2,5-dimethyl-3-thienyl)-1-{10,30,30-
trimethyl-10,30-dihydrospiro(benzo [f]chromene-3,20-
[1]benzothieno[3,2-b]pyrrol)-70-yl}-1H-pyrrol-2,5-dione 15
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To a solution of aminospiropyran 8 (51 mg, 0.128 mmol) in abs.
tetrahydrofuran (30 mL) 1 M solution of lithium hexamethyldisi-
lazide in tetrahydrofuran (ed. Note: reacts vigorously and
exothermally with water, moist air, acids, or alcohols liberating
flammable vapors which can ignite; extremely flammable liquid
and vapor; may form explosive peroxides. causes severe burns;
severely corrosive) (0.4 mL, 0.384 mmol) was added. After stirring
the reaction mixture for 15 min a solution of anhydride 14 (41 mg,
0.128 mmol) in THF (8 mL) was added. The reaction mixture was
refluxed for 2 h, cooled to room temperature, and glacial acetic acid
(2 mL) was added. The mix was refluxed for 1 h, and imidazole
(90 mg, 1.28 mmol) was added, and the refluxing was continued for
1 h. After cooling the reaction mixture was poured into 3% solution
of hydrochloric acid (70 mL) and extracted with ethyl acetate
(3 ꢂ 20 mL). The extract was washed with water, and solvent was
evaporated. The product 15 was purified by column chromatog-
raphy (eluent: petrol. ether/ethyl acetate – 15:1).
Yellow powder; yield 57%; mp. 203–205 ꢀC (ethanol). 1H NMR
(250 MHz, CDCl3):
d
¼ 1.33 (s, 3H, ½CMe2), 1.43 (s, 3H, ½CMe2), 1.91
(s, 6H, Me), 2.45 (s, 6H, Me), 3.09 (s, 3H, NMe), 5.91 (d, J ¼ 10.5 Hz,
1H, CH), 6.70 (s, 2H, Hthioph), 7.00–7.10 (m, 2H, CH þ Harom), 7.15–
7.34 (m, 2H, Harom), 7.43–7.79 (m, 5H, Harom), 8.05 (d, J ¼ 8.3 Hz, 1H,
H
arom). MS: m/z (%) ¼ 698 (36) [M]þ, 683 (100) [M–Me]þ. Anal.