Isomerization of 3H- to 2H-[1]benzothieno[3,2-b]pyrroles and synthesis of the first merocyanine dyes based on them

Article abstract of DOI:10.1002/ejoc.200500912

New 2H-[1]benzothieno[3,2-b]pyrroles were synthesized by a [1,5]-sigmatropic shift of 3H-benzothienopyrroles. The dependence of the rearrangement on solvent and temperature was studied. The first merocyanine dyes based on both 3H-and 2H-benzothienopyrrole

Full text of DOI:10.1002/ejoc.200500912

FULL PAPER
DOI: 10.1002/ejoc.200500912
Isomerization of 3H- to 2H-[1]Benzothieno[3,2-b]pyrroles and Synthesis of the
First Merocyanine Dyes Based on Them
[
a]
[a]
[a]
[a]
Alexey A. Shimkin, Valerii Z. Shirinian,* Denis M. Nikalin, Mikhail M. Krayushkin,
[a]
[a]
[a]
Tatiana S. Pivina, Nikolay A. Troitsky, Ludmila G. Vorontsova, and
Zoya A. Starikova[
b]
Keywords: Rearrangement / 3H-Thieno[3,2-b]pyrrole / 2H-Thieno[3,2-b]pyrrole / Merocyanine dyes / 1-Benzothieno[3,2-b]-
pyrrole / Benzothienopyrroleninium salts
New 2H-[1]benzothieno[3,2-b]pyrroles were synthesized by
a [1,5]-sigmatropic shift of 3H-benzothienopyrroles. The de-
pendence of the rearrangement on solvent and temperature
was studied. The first merocyanine dyes based on both 3H-
and 2H-benzothienopyrroles were synthesized and charac-
terized by NMR- and UV/Vis spectroscopy, mass spectrome-
try, and X-ray crystallography.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2006)
Introduction
While the merocyanine 5 is red, its isomer 6 is blue (in etha-
nol solution, the absorption maxima are 553 and 677 nm,
respectively). The 124-nm red shift is explained by an extra
double bond between the nitrogen atom and the carbonyl
group in merocyanine 6.
Merocyanine dyes have attracted much attention as non-
linear optical chromophores for photorefractive (PR) mate-
[
1]
rials. The potential applications of PR materials include
optical filters, holographic data storage, image processing,
and phase conjugation. Recently, we developed a conve-
nient method for the synthesis of 3H-thieno[3,2-b]pyrrole
and 3H-[1]benzothieno[3,2-b]pyrrole derivatives under
Fisher reaction conditions and prepared the first spiropy-
rans and spirooxazines based on them.[2] As a continuation
of our studies, we were interested in the preparation of
novel merocyanine dyes of the 1-benzothieno[3,2-b]pyrrole
series that could be considered as open forms of the spi-
ropyrans.
The structure of the blue isomer 6 was proved by X-ray
crystallography (Figure 1). The merocyanine molecule has
a planar structure with Z,Z configuration of the double
bonds. The C3–C12 (1.392 Å), C12–C13 (1.394 Å), and
C13–C2Ј (1.409 Å) bond lengths are almost equal, which
means that molecule 6 has a high degree of double-bond
conjugation.
The structure of compound 5 was proved by H-, 13C-,
NOE-, COSY-, and HMBC NMR spectroscopy and mass
spectrometry, and it was confirmed by elemental analysis.
Cross peaks of a methine proton at δ = 8.50 ppm with C-
1
3
Ј (δ = 167.54 ppm) and C-2 (δ = 178.78 ppm), and cross
peaks of another methine proton at δ = 6.44 ppm with C-
Ј (δ = 117.18 ppm) and C-3 (δ = 51.35 ppm) were observed
Results and Discussion
2
It was expected that the reaction of the pyrrolenine 1a[2a]
with methyl triflate followed by condensation with aldehyde
in the 2D HMBC spectrum (Figure 2). Thus the lower-field
signal (δ = 8.50 ppm) was assigned to 13-H, whilst the
higher-field signal at δ = 6.44 ppm was assigned to 12-H.
This conclusion corresponds perfectly with literature
4
(
would lead to merocyanine dye 5 as a single product
Scheme 1). However, along with compound 5 we have iso-
lated its structural isomer 6. It might be supposed that salt
, which results from the alkylation of pyrrolenine, re-
arranges to compound 3 by a [1,5]-sigmatropic shift of a
methyl group. In a manner similar to 2, salt 3 condenses
with aldehyde 4 to give the isomeric merocyanine dye 6.
[
3]
data, where the structure of the merocyanine form of spi-
robenzothiopyran was independently proved by using deu-
terium labeling. In the NOE spectrum, cross peaks of 13-H
2
with CMe and 12-H with NMe are observed (Figure 3).
2
This allows one to conclude that the double bond of the
pyrrole moiety possesses an E configuration.
Using HMBC and COSY spectra, we determined the po-
sitions of all the aromatic protons for merocyanines 5 and
[
a] N. D. Zelinsky Institute of Organic Chemistry,
4
7, Leninsky prosp., 119991, Moscow, Russian Federation
Fax: +7-095-1355328
E-mail: shir@ioc.ac.ru
6. There are two ABCD proton systems in 1-benzothi-
[
b] Institute of Organoelement Compounds,
2
8, Vavilova str., 119991, Moscow, Russian Federation
eno[3,2-b]pyrrole and 1-benzothiophen-3-one with equal
Eur. J. Org. Chem. 2006, 2087–2092
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2087

V. Z. Shirinian et al.
FULL PAPER
Scheme 1.
coupling constants JAB = 7.9, JBC = 7.3, JCD = 7.9 Hz.[4]
The extensive NMR studies enabled us to prove the config-
uration of the double bond near the pyrrole cycle and thus
to decrease the possible number of isomers of 5 to two (E,Z
and E,E, Figure 4).
MNDO calculations that were carried out for the four
possible isomers of 5 showed that the E,Z form is the most
stable, while the second possible isomer (E,E) has the sec-
ond highest enthalpy (Table 1). The calculated results corre-
spond to the gas phase, but because of the high dipole mo-
ment (6.20 D) of the E,Z isomer, it might be expected that
this isomer would be more stable in polar solvents as well.
The stability of the E,Z form of the merocyanine 5 agrees
with literature data from the calculation for the merocyan-
Figure 1. Molecular structure of the cyanine dye 6. Ellipsoids are
drawn at the 20% probability level.
[
5]
ine form of spiropyrans, though the existence of both E,Z
[
6]
and E,E isomers was proved experimentally. In spite of
the lack of direct proof it could be asserted that the double
bonds of the cyanine 5 have E,Z configuration.
Figure 2. HMBC interactions in cyanine 5.
Table 1. MNDO quantum calculations for cyanine 5.
E,Z
E,E
Z,Z
Z,E
∆
µ, [D]
H
f
° [kJ/mol]
300.91
6.20
313.80
2.17
305.59
2.24
315.77
5.55
This conclusion corresponds to the comparison of the
Figure 3. NOESY interactions in cyanine 5.
structure of dye 5 with that of its indoline analog 8 prepared
Figure 4. Possible isomers of cyanine 5.
2088
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© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2006, 2087–2092

Isomerization of 3H- to 2H-[1]Benzothieno[3,2-b]pyrroles
FULL PAPER
by a similar method from 1,3,3-trimethyl-2-methyleneindo-
line (7) and aldehyde 4 (Scheme 2).
We supposed that, not only the quaternary salt 2, but
also 3H-thienopyrroles could undergo rearrangement in the
presence of Lewis acids. In fact, the use of boron trifluo-
ride–diethyl ether as catalyst allowed us to obtain the iso-
meric 2H-thienopyrroles 9a–c as free bases (Scheme 4). The
starting 3H-pyrroles 1a–c were synthesized from 1-benzo-
thiophen-3-one hydrazone by a method developed earlier in
[
2a]
our group.
Scheme 2.
X-ray analysis of the red-colored dye 8 shows that the
molecule has an almost planar structure (the dihedral angle
between the indole and the benzothiophenone fragments is
8.73°) and that the double bonds have E,Z geometry (Fig-
ure 5). The distribution of the double bonds is close to qui-
noidal.
Scheme 4.
It was found that, of all the 3H-benzothienopyrroles syn-
thesized, the diphenyl derivative 1b was the most reactive
because of both electronic and steric effects. The rearrange-
ment occurs in benzene or THF in the presence of
BF ·OEt at 25 °C, leading to 9b in high yield. The reaction
3
2
time is significantly shorter in THF than in benzene. To
eliminate possible ionic pathways for the rearrangement, we
heated 2-methyl-3,3-diphenyl-3H-pyrrole 1b in p-xylene
Figure 5. Molecular structure of the cyanine dye 8. Ellipsoids are
drawn at the 20% probability level.
Our further investigations were connected with the study (138–140 °C) without catalyst. The reaction progressed in-
of the rearrangement reaction. We have found that the deed, but took more time to complete than in the presence
yields of the merocyanine dyes 5 and 6 are critically depend- of catalyst and was accompanied by significant resinifi-
ent on the alkylation reaction time. Heating of the pyr- cation.
rolenine 1a with methyl triflate in acetonitrile for 2–3 h led
The structure of the rearranged product 9b was proved
substantially to the formation of the red dye 5 (53%), by X-ray crystallography (Figure 6). The phenyl ring in po-
whereas the yield of the blue isomer 6 was only 2–3%. sition 3 is rotated by 12.63° relative to the benzothienopyr-
When the reaction time was increased to 23 h, the yields of role plane. The N1–C8b (1.288 Å) and C3–C3a (1.351 Å)
the dyes 5 and 6 were 18% and 29%, respectively. Finally,
when the reaction mixture was refluxed for 32 h, the yield
of the blue-colored cyanine 6 reached 50%, with only a
trace of dye 5. Thus both red and blue merocyanines could
be obtained by varying the reaction time.
Then, we have studied the rearrangement of salt 2
(Scheme 3). The heating of the latter in benzene for 30–35 h
led to the isomeric compound 3, which was characterized
1
by H NMR spectroscopy and elemental analysis. We have
found that the increase in temperature reduces the reaction
time, and the transformation of salt 2 into compound 3 is
complete within 2.5 h when the reactant is refluxed in p-
xylene (138–140 °C).
Figure 6. Molecular structure and atom labeling of the 2H-benzo-
thienopyrrole 9b. Ellipsoids are drawn at the 20% probability level.
Scheme 3.
Eur. J. Org. Chem. 2006, 2087–2092
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
2089

V. Z. Shirinian et al.
FULL PAPER
Scheme 5.
bond lengths in the pyrrole ring are close to the length of but not indole derivatives (∆H3H–2H = –80.21 kJ/mol). This
a classical double bond, and the C3a–C8b (1.460 Å) bond is also confirmed by literature data: the reaction of trialk-
length corresponds to that of an ordinary single bond. This oxy-3H-indole with methyllithium leads to 2,2-dimethyl-3-
implies that the thiophene ring is not aromatic.
methyleneindoline instead of 2,2,3-trimethyl-2H-indole,
Trimethylthienopyrrole 1a does not undergo the re- which shows the instability of the quinoidal 2H-indole
[
8]
arrangement at ambient temperature. However, the reaction form. The calculated energy differences between 3H- and
proceeds when refluxed in benzene for 28–30 h, and the re- 2H-(benzo)thienopyrroles are negative but relatively small;
action time is reduced to 1 h in p-xylene at 138–140 °C. An therefore, the 3H-isomers should be more stable, but the
interesting result was observed for tetrahydroindole 1c un- rearrangement is possible.
der similar conditions. It was found that 1c rearranges to
Both 2H- and 3H-thienopyrrole derivatives should be
give the spiro product 9c in 1 h at 80 °C. Increasing the stored at low temperature (–5 to –10 °C), except diphenyl-
reaction time or raising the temperature up to 138–140 °C substituted 1b and 9b that are quite stable at normal condi-
leads to 1-benzothieno[3,2-b]indole 9d through the mi- tions. For all the rearranged products 9a–c the signals of
1
gration of a methyl group (Scheme 5). Apparently, spiro the alkyl protons in the H NMR spectra are shifted upfield
compound 9c is a kinetic, and tetrahydroindole 9d is a relative to those of the starting 3H-pyrrole derivatives. The
thermodynamic product. The structures of the compounds main difference in the 13C NMR spectra of 3H- and 2H-
1
13
9
c and 9d were proved by H- and C NMR spectroscopy pyrroles is an expected large downfield shift of the quater-
and mass spectrometry, and they were confirmed by ele- nary carbon atom signal due to bonding with the nitrogen
mental analysis of their picrate salts. atom. For instance, the rearrangement of pyrrolenine 1a to
This reaction belongs to the Wagner–Meerwein type re- 9a leads to a shift of the signal of the CMe carbon atom
2
arrangement and proceeds through a [1,5]-sigmatropic shift from 49.60 to 87.29 ppm. The same is true for merocyanines
to the 3H-[1]benzothieno[3,2-b]pyrrole system. In the litera- 5 and 6 (the CMe2 signal is shifted from 51.35 to
ture, there are several examples of such rearrangements of 84.68 ppm).
3
H-pyrroles having alkyl, aryl, and carboxylic ester groups
[
7]
at C-3; however, there is no information on the rearrange-
ment of 3H-indole derivatives. Our attempts to carry out Conclusion
the rearrangement of 2,3,3-trimethyl-3H-indole under sim-
In conclusion, we have observed the Wagner–Meerwein
ilar conditions failed, and prolonged refluxing in p-xylene
in the presence of boron trifluoride–diethyl ether led to the
starting compound only. In order to clarify this observa-
tion, we performed the DFT quantum calculations of the
standard enthalpy of formation of different condensed and
uncondensed 2H- and 3H-pyrrole systems (Table 2). The
calculated results show that this rearrangement should be
possible in the case of pyrrole (∆H3H–2H = +15.62 kJ/mol)
type rearrangement in benzothienopyrrole derivatives and
shown that this reaction depends on both solvent and tem-
perature. Novel 2H-[1]benzothieno[3,2-b]pyrrole derivatives
and the first merocyanine dyes of the 2H- and 3H-benzothi-
enopyrrole series have been synthesized.
Experimental Section
Table 2. Quantum calculations for 3H- and 2H- pyrrole derivatives NMR spectra ( H-, 13C-, and 2D experiments) were recorded with
1
(DFT B3LYP/6-31G**).
Bruker DRX-500, AM-300, WM-250, or AC-200 spectrometers.
Mass spectra were obtained with 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 cor-
rected. Electronic absorption spectra were recorded on a LOMO
SF-256UVI spectrophotometer. Column chromatography was per-
formed by 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. 3-Hydroxy-1-benzothio-
[
9]
phene-2-carbaldehyde (4) was prepared by a known procedure.
3
H-[1]Benzothieno[3,2-b]pyrroles were synthesized by a method de-
[2a]
veloped earlier
from 1-benzothiophen-3-one hydrazone (1 g,
6
(
(
.1 mmol) and a suitable ketone (6.1 mmol) in anhydrous benzene
30 mL). The products were purified by column chromatography
CHCl /ethyl acetate, 3:1) or by recrystallization from ethanol.
3
2090
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© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2006, 2087–2092

Isomerization of 3H- to 2H-[1]Benzothieno[3,2-b]pyrroles
FULL PAPER
12-H), 7.42 (t, JHH = 7.3 Hz, 3JHH = 7.9 Hz, 1 H, 6Ј-H), 7.49 (t,
3
2
0
2
-Methyl-3,3-diphenyl-3H-[1]benzothieno[3,2-b]pyrrole (1b): Yield
.56 g (27%). M.p. 181–183 °C. 1H NMR (300 MHz, CDCl
4 °C): δ = 2.41 (s, 3 H, Me), 7.18–7.25 (m, 4 H, Ph), 7.29–7.37
3
3
3
3
,
JHH = 7.3 Hz, JHH = 7.9 Hz, 1 H, 6-H), 7.57 (t, JHH = 7.9 Hz,
3JHH = 7.3 Hz, 1 H, 7-H), 7.60 (t, JHH = 7.3 Hz, JHH = 7.9 Hz,
3
3
3
3
3
3
(m, 7 H, Ph + H-arom.), 7.47 (t, JHH = 7.4 Hz, JHH = 8.1 Hz, 1
1 H, 5Ј-H), 7.86 (d, JHH = 7.9 Hz, 1 H, 4Ј-H), 7.92 (d, JHH =
3
3
3
3
H, H-arom.), 7.79 (d, JHH = 8.1 Hz, 1 H, H-arom.), 8.14 (d, JHH
8.1 Hz, 1 H, H-arom.) ppm. 13C NMR (62.9 MHz, CDCl
,
3
7.9 Hz, 1 H, 7Ј-H), 8.14 (d, JHH = 7.9 Hz, 1 H, 5-H), 8.26 (d, JHH
= 7.9 Hz, 1 H, 8-H), 8.50 (d, JHH = 15.3 Hz, 1 H, 13-H) ppm. 13C
3
=
2
1
1
4 °C): δ = 18.51 (Me), 72.99 (C-3), 121.59, 123.91, 124.30, 125.01,
6 3
NMR (125 MHz, [D ]DMSO + CF COOH, 24 °C): δ = 27.34 (C-
10, C-11), 35.19 (C-9), 51.35 (C-3), 103.41 (C-12), 117.18 (C-2Ј),
120.91, 123.74, 124.16, 125.05, 125.10, 125.31, 125.58, 125.73,
27.79, 127.99, 129.02, 130.30, 140.15, 144.08, 144.60, 151.87,
+
87.81 (C-2) ppm. MS: m/z = 339 [M ]. C23
H17NS (339.45): calcd.
C 81.38, H 5.05, N 4.13; found C 80.76, H 5.04, N 4.16.
128.21, 131.32, 132.44, 137.41 (C-13), 138.10, 140.46, 142.67,
+
167.54 (C-3Ј), 178.78 (C-2) ppm. MS: m/z = 389 [M ]. C23
H19NOS
2
4
a-Methyl-2,3,4,4a-tetrahydro-1H-[1]benzothieno[3,2-b]indole (1c):
(
389.54): calcd. C 70.92, H 4.92, N 3.60; found C 70.51, H 5.17, N
1
Yield 0.59 g (40%). M.p. 103–104 °C. H NMR (250 MHz, CDCl
4 °C): δ = 1.15–1.28 (m, 1 H, CH), 1.30 (s, 3 H, Me), 1.32–1.49
m, 1 H, CH), 1.52–1.71 (m, 2 H, CH ), 2.02–2.16 (m, 1 H, CH),
3
,
3.87.
2
(
2
-[2-(1,2,2-Trimethyl-1,2-dihydro-3H-[1]benzothieno[3,2-b]pyrrol-3-
2
2
3
yliden)ethylidene]-1-benzothiophen-3-one (6): A solution of 3H-pyr-
role 1a (0.5 g, 2.3 mmol) and methyl trifluoromethanesulfonate
(0.26 mL, 2.3 mmol) in acetonitrile (5 mL) was refluxed for 32 h.
The solvent was evaporated, and to the brownish solid were added
ethanol (5 mL), aldehyde 4 (0.41 g, 2.3 mmol) and piperidine
2
1
7
.16–2.28 (m, 1 H, CH), 2.51 (td, JHH = 13.8 Hz, JHH = 5.9 Hz,
H, CH), 2.81–2.93 (m, 1 H, CH), 7.24 (t, JHH = 7.3 Hz, 3JHH
3
=
3
3
.9 Hz, 1 H, H-arom.), 7.38 (t, JHH = 7.3 Hz, JHH = 7.9 Hz, 1 H,
3
3
H-arom.), 7.76 (d, JHH = 7.9 Hz, 1 H, H-arom.), 8.08 (d, JHH
7
=
.9 Hz, 1 H, H-arom.) ppm. 1 C NMR (62.9 MHz, CDCl
3
3
, 24 °C):
(
1
0.23 mL, 2.3 mmol). The reaction mixture was heated to reflux for
h, cooled and filtered to give the blue solid 6 (0.16 g, 18%). Etha-
nol was evaporated from the solution, and the crude product was
purified by column chromatography (eluent CHCl /ethyl acetate,
:1). Total yield 0.45 g (50%). M.p. 233–235 °C (ethanol). UV/Vis:
max, nm (log ε) = 640 (4.56), 677 (4.62) in ethanol, 621 (4.44), 656
δ = 20.23, 21.36, 29.70, 30.41, 39.66, 55.21 (C-3), 121.14, 123.85,
23.90, 124.79, 130.50, 143.51, 144.51, 151.42, 192.32 (C-2) ppm.
1
+
MS: m/z = 241 [M ]. C15
H15NS (241.35): calcd. C 74.65, H 6.26,
N 5.80; found C 74.29, H 6.59, N 5.88.
3
3
λ
(
1,2,3,3-Tetramethyl-3H-[1]benzothieno[3,2-b]pyrrol-1-ium Trifluoro-
methanesulfonate (2): A solution of 3H-pyrrole 1a (0.3 g, 1.4 mmol)
and methyl trifluoromethanesulfonate (0.16 mL, 1.4 mmol) in ace-
tonitrile (3 mL) was refluxed for 20 min, then cooled, and the sol-
1
4.43) in acetonitrile. H NMR (250 MHz, [D
6
]DMSO +
CF
3
COOH, 24 °C): δ = 1.70 (s, 6 H, CMe
2
), 3.90 (s, 3 H, NMe),
3
3
3
6.75 (d, JHH = 15.3 Hz, 1 H, 12-H), 7.42 (t, JHH = 7.3 Hz, JHH
vent was evaporated. The crude solid was washed with THF and
3
3
=
7.9 Hz, 1 H, 5Ј-H), 7.50 (t, JHH = 7.3 Hz, JHH = 7.9 Hz, 1 H,
1
dried. Yield 0.4 g (75%). H NMR (250 MHz, [D
6
]DMSO, 24 °C):
3
3
6
J
7
5
Ј-H), 7.64 (t, JHH = 7.9 Hz, JHH = 7.3 Hz, 1 H, 7-H), 7.84 (d,
δ = 1.64 (s, 6 H, CMe
2
3
), 2.78 (s, 3 H, Me), 4.27 (s, 3 H, NMe),
3
HH = 15.3 Hz, 1 H, 13-H), 7.84–7.94 (m, 2 H, 6-H and 7Ј-H),
3
3
7
=
1
.55 (t, JHH = 7.9 Hz, JHH = 7.3 Hz, 1 H, H-arom.), 7.63 (t, JHH
.99 (d, 3JHH = 7.9 Hz, 1 H, 4Ј-H), 8.16 (d, JHH = 7.9 Hz, 1 H,
3
3
3
7.9 Hz, JHH = 7.3 Hz, 1 H, H-arom.), 8.21 (d, JHH = 7.9 Hz,
H, H-arom.), 8.27 (d, 3
HH = 7.9 Hz, 1 H, H-arom.) ppm.
NO (379.42): calcd. C 47.48, H 4.25, N 3.69; found C
3
13
-H), 8.49 (d, JHH = 7.9 Hz, 1 H, 8-H) ppm. C NMR (125 MHz,
]DMSO + CF COOH, 24 °C): δ = 21.34 (C-10, C-11), 31.93 (C-
J
[D
6
3
C
15
H
16
F
3
3 2
S
9
1
1
1
7
), 84.68 (C-2), 113.44 (C-12), 116.22 (C-2Ј), 122.39, 122.86, 123.38,
24.88, 125.73, 126.08, 126.97, 128.63, 129.17, 132.24, 134.00 (C-
47.25, H 4.39, N 3.47.
3), 135.74, 137.90, 152.71, 155.06 (C-3Ј), 161.28 (C-3),
1,2,2,3-Tetramethyl-2H-[1]benzothieno[3,2-b]pyrrol-1-ium Trifluoro-
+
69.27 ppm. MS: m/z = 389 [M ]. C23
H19NOS
2
(389.54): calcd. C
methanesulfonate (3): A suspension of salt 2 (0.2 g, 0.53 mmol) in
p-xylene (2 mL) was refluxed for 2.5 h. After cooling, the solid was
0.92, H 4.92, N 3.60; found C 70.53, H 5.23, N 3.56.
filtered off, washed with benzene, and dried in vacuo. Yield 0.12 g
2-[2-(1,3,3-Trimethyl-1,3-dihydro-2H-indol-2-yliden)ethylidene]-1-
benzothiophen-3-one (8): A solution of 1,3,3-trimethyl-2-methyl-
eneindoline (1 mL, 5.5 mmol) and aldehyde 4 (1 g, 5.6 mmol) in
ethanol (10 mL) was refluxed for 1.5 h. After cooling, the greenish
1
(
60%). H NMR (250 MHz, [D
6
]DMSO, 24 °C): δ = 1.56 (s, 6 H,
3
CMe
7
2
), 2.38 (s, 3 H, Me), 3.90 (s, 3 H, NMe), 7.64 (t,
J
HH
3
=
.9 Hz, 3JHH = 7.3 Hz, 1 H, H-arom.), 7.92 (t, JHH = 7.9 Hz, JHH
3
3
=
8
(
7.3 Hz, 1 H, H-arom.), 8.09 (d, JHH = 7.9 Hz, 1 H, H-arom.),
HH = 7.9 Hz, 1 H, H-arom.) ppm. C15 NO
379.42): calcd. C 47.48, H 4.25, N 3.69; found C 47.23, H 4.41, N
yellow crystals were filtered off, washed with ethanol and dried.
.49 (d, 3
J
H
16
F
3
S
2
[10]
3
Yield 1.37 g (73%). M.p. 203–205 °C (ref. 201 °C). UV/Vis: λmax,
1
nm (log ε) = 520 (4.76) in acetonitrile. H NMR (300 MHz, CDCl ,
3
3
3.44.
24 °C): δ = 1.70 (s, 6 H, CMe ), 3.33 (s, 3 H, NMe), 5.48 (d, J
13.2 Hz, 1 H, 11-H), 6.82 (d, JHH = 7.4 Hz, 1 H, H-arom.), 7.03
t, JHH = 7.4 Hz, 1 H, H-arom.), 7.20–7.30 (m, 3 H, H-arom.),
2
HH
3
=
(
2
-[2-(1,3,3-Trimethyl-1,3-dihydro-2H-[1]benzothieno[3,2-b]pyrrol-2-
3
yliden)ethylidene]-1-benzothiophen-3-one (5): Methyl trifluorometh-
anesulfonate (0.26 mL, 2.3 mmol) was added to a stirred solution
of pyrrolenine 1a (0.5 g, 2.3 mmol) in MeCN (5 mL). The reaction
mixture was refluxed for 3 h, then cooled, and the solvent was re-
moved under vacuum. The brownish solid was dissolved without
purification in EtOH (5 mL), and after aldehyde 4 (0.41 g,
3
7
.46–7.54 (m, 2 H, H-arom.), 7.93 (d,
J
HH = 7.4 Hz, 1 H, H-
arom.), 8.25 (d, JHH = 13.2 Hz, 1 H, 12-H) ppm.
H-[1]Benzothieno[3,2-b]pyrroles (General Procedure): Boron trifluo-
ride–diethyl ether (0.39 mmol) was added to a stirred solution of
H-pyrrole 1 (0.3 mmol) in benzene or xylene (3 mL). The reaction
3
2
3
mixture was refluxed until the starting material disappeared. The
solution was poured into water (30 mL), and the aqueous layer was
extracted with ethyl acetate (3×10 mL). After evaporation of the
solvent in vacuo, the crude product was purified by column
2
.3 mmol) and piperidine (0.23 mL, 2.3 mmol) were added, the
solution was refluxed for 1 h. The reaction mixture was cooled, and
the solid precipitated was filtered off, washed with EtOH and dried.
The filtrate was evaporated, and the crude product was purified by
chromatography (CHCl
picrate salts were prepared by the reactions of 2H-pyrroles 9 with
,4,6-trinitrophenol in ethanol.
2,2,3-Trimethyl-2H-[1]benzothieno[3,2-b]pyrrole (9a): Yield 26 mg
3
/ethyl acetate, 3:1). For analytical purposes
column chromatography, by being eluted with CHCl
3
/ethyl acetate,
:1. Total yield 0.48 g (53%). M.p. 239–241 °C (ethanol). UV/Vis:
max, nm (log ε) = 553 (4.74) in ethanol, 540 (4.67) in acetonitrile.
3
λ
1
2
H NMR (250 MHz, [D
6 3
]DMSO + CF COOH, 24 °C): δ = 1.84
3
1
(s, 6 H, CMe
2
), 4.14 (s, 3 H, NMe), 6.44 (d, JHH = 15.3 Hz, 1 H,
(40%). Brownish oil. H NMR (250 MHz, CDCl
3
, 24 °C): δ = 1.38
Eur. J. Org. Chem. 2006, 2087–2092
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org 2091

V. Z. Shirinian et al.
FULL PAPER
), 2.08 (s, 3 H, Me), 7.28 (t, JHH = 7.9 Hz, 3JHH
3
=
=
can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
(
s, 6 H, CMe
2
3
3
7
.3 Hz, 1 H, H-arom.), 7.42 (t, JHH = 7.9 Hz, JHH = 7.3 Hz, 1 H,
3
3
H-arom.), 7.48 (d, JHH = 7.9 Hz, 1 H, H-arom.), 8.04 (d, JHH
.9 Hz, 1 H, H-arom.) ppm. 13C NMR (62.9 MHz, CDCl
δ = 12.13 (Me), 22.77 (CMe
25.32, 126.58, 131.60, 150.32, 157.74, 174.15 ppm. MS: m/z = 215
Crystal Data for 6: C23
2 r
H19NOS , M = 389.51, rhombic, space
7
3
, 24 °C):
), 87.19 (C-2), 124.41, 124.61, 125.00,
group Pbca, a = 11.866(6), b = 16.114(6), c = 20.058(7) Å, V =
2
3
3
3
835(3) Å , T = 100(2) K, Z = 8, Dcalcd. = 1.349 g/cm , 2950 unique
1
reflections in the 2.36 Յ θ Յ 24.00° range. The final R factors: R
0.074, wR = 0.115 (all data).
1
+
[M ]. Picrate: m.p. 227–229 °C (ethanol). C19
16 4 7
H N O S (444.42):
=
2
calcd. C 51.35, H 3.63, N 12.61; found C 50.93, H 3.84, N 12.40.
Crystal Data for 8: C21 19NOS, M
group P2
02.22(3)°, V = 1728.5 Å , T = 100(2) K, Z = 4, Dcalcd. = 1.281 g/
H
r
= 333.43, monoclinic, space
3
-Methyl-2,3-diphenyl-2H-[1]benzothieno[3,2-b]pyrrole (9b): Yield
1
/c, a = 8.286(3), b = 12.582(4), c = 16.963(6) Å, β =
1
9
2 mg (90%). M.p. 135–137 °C (ethanol). H NMR (250 MHz,
3
1
CDCl
3
, 24 °C): δ = 2.03 (s, 3 H, Me), 7.20–7.40 (m, 11 H, 2Ph +
3
cm , 3051 unique reflections in the 2.94 Յ θ Յ 25.04° range. The
final R factors: R = 0.067, wR = 0.170 (all data).
3
3
H-arom.), 7.50 (t, JHH = 7.9 Hz, JHH = 7.3 Hz, 1 H, H-arom.),
1
2
3
3
7.58 (d, JHH = 7.9 Hz, 1 H, H-arom.), 8.14 (d, JHH = 7.9 Hz, 1
13
Crystal Data for 9b: C23 17NS, M = 339.45, rhombic, space group
H
r
H, H-arom.) ppm. C NMR (62.9 MHz, CDCl
3
, 24 °C): δ = 21.89
3
Pbca, a = 15.241(4), b = 7.996(2), c = 28.454(7) Å, V = 3467.56 Å ,
(Me), 90.98 (C-2), 121.41, 124.18, 125.12, 125.75, 125.94, 127.64,
3
T = 193(2) K, Z = 8, Dcalcd. = 1.300 g/cm , 3960 unique reflections
1
1
27.80, 127.92, 128.01, 128.60, 128.80, 128.86, 131.68, 131.90,
38.70, 156.28, 174.35 ppm. MS: m/z = 339 [M ]. C23
+
in the 2.94 Յ θ Յ 25.04° range. The final R factors: R
1
= 0.076,
H17NS
wR = 0.113 (all data).
2
(339.45): calcd. C 81.38, H 5.05, N 4.13; found C 81.15, H 5.40, N
4.04.
Acknowledgments
3
-Methylspiro[2H-[1]benzothieno[3,2-b]pyrrole-2,1Ј-cyclopentane]
1
(
(
(
(
9c): Yield 21 mg (29%). M.p. 113–115 °C (ethanol). H NMR
This work was supported by the Russian Foundation for Basic Re-
search (grant No. 05–03–33191-a).
250 MHz, CDCl
m, 4 H, CH
3 2
, 24 °C): δ = 1.67–1.84 (m, 2 H, CH ), 1.85–2.02
2
), 2.07 (s, 3 H, Me), 2.13–2.34 (m, 2 H, CH
2
3
), 7.26
t, JHH = 7.9 Hz, 3JHH = 7.3 Hz, 1 H, H-arom.), 7.40 (t, JHH
3
=
.9 Hz, 3JHH = 7.3 Hz, 1 H, H-arom.), 7.46 (d, JHH = 7.9 Hz, 1
3
7
[1] a) O. Ostroverkhova, W. E. Moerner, Chem. Rev. 2004, 104,
3267–3314; b) A. J. Kay, A. D. Woolhouse, Y. Zhaob, K. Clays,
J. Mater. Chem. 2004, 14, 1321–1330; c) L. V. Khokhlova,
G. K. Lebedeva, V. A. Lukoshin, L. M. Bykova, Russ. J. Gen.
Chem. (Translation Zhurnal Obsh. Khim.) 2004, 74, 271–275.
3
13
H, H-arom.), 8.11 (d,
NMR (62.9 MHz, CDCl
JHH = 7.9 Hz, 1 H, H-arom.) ppm.
C
3
, 24 °C): δ = 12.17, 26.38, 34.09, 97.93 (C-
2
1
), 124.42, 125.16, 125.30, 127.99, 129.50, 131.50, 150.25, 154.44,
+
74.05 ppm. MS: m/z = 241 [M ]. Picrate: m.p. 183–185 °C (etha-
S (470.46): calcd. C 53.61, H 3.86, N 11.91; found
C 53.55, H 4.05, N 11.99.
[
2] a) V. Z. Shirinian, M. M. Krayushkin, D. M. Nikalin, A. A.
Shimkin, Russ. Chem. Bull., Int. Ed. 2005, 54, 738–742; b)
M. M. Krayushkin, V. Z. Shirinian, D. M. Nikalin, Russ.
Chem. Bull., Int. Ed. 2004, 53, 720–721; c) V. Z. Shirinian,
M. M. Krayushkin, D. M. Nikalin, A. A. Shimkin, L. G. Vo-
rontsova, Z. A. Starikova, Arkivoc 2005, vii, 72–81.
18 4 7
nol). C21H N O
1
0a-Methyl-2,3,4,10a-tetrahydro-1H-[1]benzothieno[3,2-b]indole
1
(9d): Yield 49 mg (67%). M.p. 121–123 °C (ethanol). H NMR
2
3
(
4
300 MHz, CDCl
3
, 24 °C): δ = 1.01 (td, JHH = 13.2 Hz, JHH =
[
3] M. Hirano, K. Osakada, H. Nohira, A. Miyashita, J. Org.
Chem. 2002, 67, 533–540.
.4 Hz, 1 H, CH), 1.14 (qt, 2JHH = 13.2 Hz, JHH = 4.4 Hz, 1 H,
3
2
3
CH), 1.34 (s, 3 H, Me), 1.62 (qt, JHH = 13.2 Hz, JHH = 3.7 Hz,
H, CH), 1.72–1.82 (m, 1 H, CH), 1.99–2.10 (m, 1 H, CH), 2.32
[
4] a) D. F. Ewing, R. M. Scrowston, Org. Magn. Res. 1971, 3,
1
405–416; b) K. D. Bartle, D. W. Jones, R. S. Matthews, Tetrahe-
2
3
(td, JHH = 13.2 Hz, JHH = 5.5 Hz, 1 H, CH), 2.46–2.56 (m, 1 H,
dron 1971, 27, 5177–5189.
[5] Y. Abe, R. Nakao, T. Horii, S. Okada, M. Irie, J. Photochem.
Photobiol. A: Chem. 1996, 95, 209–214.
[6] a) J. Hobley, V. Malatesta, Phys. Chem. Chem. Phys. 2000, 2,
57–59; b) T. Suzuki, F.-T. Lin, S. Priyadashy, S. G. Weber,
Chem. Commun. 1998, 2685–2686; c) S. M. Aldoshin, Russ.
Chem. Rev. 1990, 59, 663–684.
3
3
CH), 2.83–2.92 (m, 1 H, CH), 7.29 (t,
J
HH = 7.5 Hz,
J
HH
=
3
3
7.8 Hz, 1 H, H-arom.), 7.43 (t, JHH = 7.5 Hz, JHH = 7.8 Hz, 1 H,
3
3
H-arom.), 7.49 (d, JHH = 7.9 Hz, 1 H, H-arom.), 8.07 (d, JHH
=
.9 Hz, 1 H, H-arom.) ppm. 1 C NMR (50 MHz, CDCl
3
7
3
, 24 °C): δ
=
1
19.93, 22.24, 26.77, 27.89, 39.22, 86.60 (C-2), 124.48, 124.96,
25.31, 125.73, 127.90, 131.52, 150.44, 160.73, 174.66 ppm. MS:
[
7] a) K.-H. Lui, M. P. Sammes, J. Chem. Soc., Perkin Trans. 1
+
m/z = 241 [M ]. Picrate: m.p. 213–214 °C (ethanol). C21
470.46): calcd. C 53.61, H 3.86, N 11.91; found C 53.10, H 4.04,
N 11.83.
18 4 7
H N O S
1
990, 457–468; b) P.-K. Chiu, M. P. Sammes, Tetrahedron 1990,
(
4
6, 3439–3456; c) J. L. Wong, M. H. Ritchie, C. M. Gladstone,
J. Chem. Soc., Chem. Commun. 1971, 1093–1094.
8] E. Wenkert, T. Hudlický, Synth. Commun. 1977, 7, 541–547.
9] V. M. Rodionov, B. M. Bogoslovskii, Z. S. Kazakova, Izv.
Akad. Nauk SSSR, Otd. Khim. Nauk 1948, 5, 536–547; Chem.
Abstr. 1949, 43, 2200d.
[
[
X-ray Crystallography: X-ray diffraction data were collected with
a Syntex P2 diffractometer with graphite-monochromated Mo-K
1
α
radiation in the θ/2θ scan mode. The structures were solved by
direct methods and refined by full-matrix least-squares in the an-
isotropic approximation for non-hydrogen atoms. The hydrogen
atoms were located by difference synthesis and refined isotropically
by least-square methods.
[
10] T. Ogata, S. Maruyama, Bull. Inst. Phys. Chem. Res. Tokyo
1937, 16, 614–618; Beilstein 27, IV, 2130.
[11] Siemens P3 and XDISK. Release 4.1. Siemens AXS, Madison,
Wisconsin, USA, 1989.
[
12] G. M. Sheldrick, SHELXTL v. 5.10, Structure Determination
Software Suite, Bruker AXS, Madison, Wisconsin, USA, 1998.
Received: November 22, 2005
Siemens P3/PC[11] and SHELXTL PLUS 5[12] programs were used.
CCDC-290196 (for 6), -290288 (for 8) and -290289 (for 9b) contain
the supplementary crystallographic data for this paper. These data
Published Online: February 24, 2006
2092
www.eurjoc.org
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2006, 2087–2092