Synthesis of annulated oligothiophenes

Article abstract of DOI:10.1007/s11172-012-0188-1

Reactions of 1,1-di(2-naphthyl)-2,2-dichloroethene and 1,1-di(2- benzothienyl)-2,2-dichloroethene with sulfur at 220-225 C resulted in hitherto unknown oligothiophenes. Tetrathio[6]helicene was synthesized from 1,1-di(3-benzothienyl)-2,2-dichloroethene. Preparative pathway to helicene involving intramolecular ring closure of dithiol derived from 1,1-di-(3-benzothienyl)-2,2-dichloroethene was developed as an alternative to high temperature synthesis.

Full text of DOI:10.1007/s11172-012-0188-1

1
456
Russian Chemical Bulletin, International Edition, Vol. 61, No. 7, pp. 1456—1462, July, 2012
Synthesis of annulated oligothiophenes*
V. G. Nenajdenko, E. S. Balenkova, K. Y. Chernichenko, and S. S. Vshivenko
Department of Chemistry, M. V. Lomonosov Moscow State University,
1
Leninskie Gory, 119992 Moscow, Russian Federation.
Fax: +7 (495) 932 8846. Eꢀmail: nen@acylium.chem.msu.ru
Reactions of 1,1ꢀdi(2ꢀnaphthyl)ꢀ2,2ꢀdichloroethene and 1,1ꢀdi(2ꢀbenzothienyl)ꢀ2,2ꢀ
dichloroethene with sulfur at 220—225 C resulted in hitherto unknown oligothiophenes.
Tetrathio[6]helicene was synthesized from 1,1ꢀdi(3ꢀbenzothienyl)ꢀ2,2ꢀdichloroethene. Preparꢀ
ative pathway to helicene involving intramolecular ring closure of dithiol derived from 1,1ꢀdiꢀ
(
3ꢀbenzothienyl)ꢀ2,2ꢀdichloroethene was developed as an alternative to high temperature
synthesis.
Key words: 1,1ꢀdiarylꢀ2,2ꢀdichloroethenes, sulfur, diaryl ketones, helicenes, oligoꢀ
thiophenes.
Annulated oligothiophenes are important building
Scheme 1
blocks toward materials for a wide variety of applications,
1
2
e.g., electroluminescence, fluorescence, photochromism,
3
nonꢀlinear optics. Several thin film transistors based on
oligothiophenes exhibit high fieldꢀeffect charge mobility
and on/off ratios. Oligothiophenes were also used for the
4
5
synthesis of conducting polymers. Recently, in our group
the first derivatives of hitherto unknown class of organic
compounds, heterocyclic circulenes contaning thiophene
or selenophene rings, were synthesized and their potential
X = H (1, 4), Br (2, 5), Cl (3, 6)
6
applications as novel materials were studied. Heterocyclic
Reagent and conditions: S, 1,2ꢀdichlorobenzene, 260—270 C.
helicenes with ꢀdonating thiophene rings are of essential
interest.7
Reaction of halogenated aromatic compounds with sulꢀ
fur is one of the simplest methods to access fused thiophene
compounds. Thus, heating 1,1ꢀdiphenylꢀ2,2,2ꢀtrichloroꢀ
Scheme 2
8
ethane (1) and its chlorinated (2) and brominated (3) deꢀ
rivatives with sulfur at 260—270 C resulted in benzoꢀ
thiopheno[2,3ꢀb]benzothiophenes 4—6 in 40—50% yields
(
Scheme 1).
The mechanism of this reaction is unclear, however, it
was assumed that the initial step of the reaction involved
thermal removal of hydrogen chloride to give the correꢀ
sponding dichloroalkene 7; the intermediate 2ꢀchloroꢀ3ꢀ
phenylbenzothiophene formed on the initial step of the
ring closure was also isolated (Scheme 2).
This versatile and effective approach attracted our atꢀ
tention; therefore, we decided to explore the synthetic
scope and potential of the reaction. With the aim to synꢀ
thesize other fused oligothiophenes, we studied the reacꢀ
tion of various naphthylꢀ and benzothienylꢀsubstituted
*
Based on the Materials of the International Congress on Orꢀ
1
,1ꢀdichloroethenes with sulfur. We improved the reacꢀ
ganic Chemistry dedicated to the 150th anniversary of the
Butlerov´s Theory of Chemical Structure of Organic Compounds
tion conditions. It was found that the reactions with the
(
September 19—23, 2011, Kazan, Russia).
corresponding dichloroalkene 7 can be performed at temꢀ
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1441—1447, July, 2012.
066ꢀ5285/12/6107ꢀ1456 © 2012 Springer Science+Business Media, Inc.
1

Synthesis of annulated oligothiophenes
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 7, July, 2012
1457
peratures lower by 30—40 C than earlier described giving
the target product in the yields higher by 5—10%; howevꢀ
er, 2—3ꢀfold longer reaction times were required. To reꢀ
duce resinification and avoid overheating, 1,2,4ꢀtrichloroꢀ
benzene boiling at 214 C was used as a solvent. All these
improvements allowed us to increase the yield of benzoꢀ
thiopheno[2,3ꢀb]benzothiophene (4) to 70%, and its
Scheme 4
3
,8ꢀdichloroꢀ (5) and 3,8ꢀdibromoꢀsubstituted derivatives
(
6) to 53 and 50%, respectively. The yields achieved by us
8
a
were by 10—20% higher than these reported earlier.
Naphthyl derivatives of 2,2,2ꢀtrichloroethanes 8—10
were synthesized under conditions used for the synthesis
of 1,1,1ꢀtrichloroꢀ2,2ꢀbis(4ꢀchlorophenyl)ethane (DDT),
namely, by the reaction or arenes with chloral. Refluxing
trichlorides with KOH in isopropyl alcohol was found to
be the optimal for removal of hydrogen chloride to yield
dichloroethanes 11—13 (Scheme 3).
Scheme 3
Reagents: i. 1) BuLi, 2) Me NCOCl, 3) 1 M HCl.
2
A low yield synthesis of di(3ꢀbenzothienyl) ketone (17)
from benzothiopheneꢀ3ꢀcarbonyl chloride and 3ꢀbenzoꢀ
1
1
thienylmagnesuim chloride have been described. We
modified this procedure and converted 3ꢀbenzothiophene
carboxylic acid into the corresponding Weinreb amide 18.
The use of amide 18 makes it possible to add only one
equivalent of organometallic compound to the carbonyl
group. Thus modified procedure allows the synthesis of
di(3ꢀbenzothienyl) ketone (17) from benzothiophene in
4
0% total yield (Scheme 5).
,1ꢀDi(2ꢀbenzothienyl)ꢀ2,2ꢀdichloroethene (19) was
synthesized in 85% yield by the Wittig reaction used previꢀ
1
1
2
ously for the similar aliphatic substrates. However, reacꢀ
tions involving di(3ꢀbenzothienyl) ketone (17) and dinaphꢀ
thyl ketones 14 and 15 are more complicated. In the case
of di(3ꢀbenzothienyl) ketone (17), the yield of the target
dichloride did not exceed 15—20%. Carrying out the reacꢀ
tion with excesses of triphenylphosphine and CCl did not
4
X = OMe (8, 11), Cl (9, 12), F (10, 13)
improve the yield of dichloroalkene. In the case of ketone
14, no formation of dichloroalkene virtually occurs, which
is due apparently to the sensitivity of this reaction to steric
demands (the protons in the peri position caused signifiꢀ
cant steric strain). Therefore, 1,1ꢀdi(1ꢀnaphthyl)ꢀ2,2ꢀ
dichloroethene (20), 1,1ꢀdi(2ꢀnaphthyl)ꢀ2,2ꢀdichloroꢀ
ethene (21), and 1,1ꢀdi(3ꢀbenzothienyl)ꢀ2,2ꢀdichloroetꢀ
hene (22) were synthesized by the reaction of diethyl
dichloromethylphosphonate with ketones in the presence
of lithium hexamethyldisilazide in the yields of 17, 68, and
75%, respectively. This approach is less sensitive to the
steric strains and serves for the synthesis of hindered
i
Reagents: i. CCl CHO, H SO ; ii. KOH, Pr OH.
3
2
4
Attempts to synthesize the corresponding 1,1ꢀdiarylꢀ
,2,2ꢀtrichloroethanes by the reactions of unsubstituted
naphthalene with chloral gave the inseparable mixtures of
the isomers. Therefore, the target compounds of this group
were accessed from symmetric ketones 14—16 (Scheme 4)
by transformation of 14—16 into the corresponding orgaꢀ
nometallic derivatives and subsequent olefination of the
latter into dichloroethenes.
However, di(3ꢀbenzothienyl) ketone (17) cannot be
accessed from 3ꢀbromobenzothiopehe via this procedure.
2
9
10
1
3
dichloroalkenes (Scheme 6).

1458
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 7, July, 2012
Nenajdenko et al.
Scheme 5
+
Reagent and conditions: i. Br ; ii. 1) BuLi, 2) CO , 3) H O ; iii. 1) 1,1ꢀcarbonyldiimidazole (CDI), 2) HN(Me)OMe•HCl;
iv. Pr MgCl•LiCl, THF, diethyl ether.
2
2
3
i
Scheme 6
pheno[2,3:4´,5´]thieno[3´,2´:4,5]thieno[3,2ꢀb]benzoꢀ
thiophene (24) in the yield of 47% (Scheme 7).
Scheme 7
Ar = 1ꢀnaphthyl (14, 20), 2ꢀnaphthyl(15, 21), 3ꢀbenzothienyl(17, 22)
Reagents: i. Ph P, CCl , THF; ii. LiN(TMS) .
3
4
2
Heating either 1,1ꢀdi(1ꢀnaphthyl)ꢀ2,2ꢀdichloroethꢀ
ene (20) or substituted 1,1ꢀdi(1ꢀnaphthyl)ꢀ2,2ꢀdichloroꢀ
ethenes 11—13 with sulfur at 220—225 C led to signifiꢀ
cant resinification of the reaction mixtures and isolation
of the target products failed. In contrast to ꢀnaphthylꢀ
substituted dichloroalkenes 11—13, reaction of 1,1ꢀdi(2ꢀ
naphthyl)ꢀ2,2ꢀdichloroethene (21) with sulfur afforded
hitherto unknown naphtho[1,2ꢀb]naphtho[2´,1´:4,5]ꢀ
thieno[3,2ꢀd]thiophene (23) in 27% yield. Similarly, the
reaction of 1,1ꢀdi(2ꢀbenzothienyl)ꢀ2,2ꢀdichloroethene
Reagents and conditions: i. S, 1,2,4ꢀtrichlorobenzene, 220—225 C.
Reaction of 1,1ꢀdi(3ꢀbenzothienyl)ꢀ2,2ꢀdichloroethꢀ
ene (22) with sulfur afforded target hitherto unknown
thiophenic helicene, benzothiopheno[3,2:4´,5´]thienoꢀ
[3´,2´:4,5]thieno[2,3ꢀb]benzothiophene (25) in 25% yield
(Scheme 8).
Low yield of helicene 25 motivated us to elaborate
alternative procedure for heterocyclization of dichloroꢀ
alkenes. We suggested that benzothiophenes could be
transformed into target compounds by deprotonation,
(
19) with sulfur gave previously unknown benzothioꢀ

Synthesis of annulated oligothiophenes
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 7, July, 2012
1459
Scheme 8
A (rel. units)
2
2
1
1
5
0
5
0
5
0
2
3
2
4
Reagents and conditions: S, 1,2,4ꢀtrichlorobenzene, 220—225 C.
which benzotiophenes are especially prone, followed by
treatment of the resulting lithium salts to give the correꢀ
sponding thiolates and subsequent ring closure of the latꢀ
ter involving nucleophilic replacement of the chlorine atꢀ
oms. By this approach, helicene 25 was synthesized from
2
5
1
,1ꢀdi(3ꢀbenzothienyl)ꢀ2,2ꢀdichloroethene (22) in 50%
yield (Scheme 9), which is double the yield afforded by
heating dichloroalkene with sulfur.
360
320
280
240
200 /nm
Fig. 1. UV spectra of compounds 23, 24, and 25.
Scheme 9
compounds, they are simple straightforward procedures
serving for the synthesis of hitherto unknown oligoꢀ
thiophenes.
Experimental
1H and 13C NMR spectra were run on a Bruker Avance 400
spectrometer (working frequencies of 400 and 100 MHz, respecꢀ
tively) in CDCl with Me Si as internal standard. Mass spectra
Reagents and conditions: i. 1) LDA, 2) S ; ii. DMF, 80 C, 6 h.
8
3
4
(
70 eV) were recorded on a Shimadzu GCMSꢀQP5050A instruꢀ
The structures of oligothiophenes synthesized were
ment. UV spectra were obtained on a Agilent 8453 instrument.
TLC was performed on Merck 60 plates; for visualization of the
spots, acidified KMnO solution, concentrated sulfuric acid or
1
13
evaluated by H and C NMR spectroscopy, UV specꢀ
troscopy, and elemental analysis. Considerable difference
in chemical shifts of the C(11) protons for helicene 25
4
iodine vapors were used. Preparative column chromatography
was performed on silica gel (63—200 mesh, Merck). Melting
points were determined on a Electrothermal 9100 apparatus.
Compounds sensitive to moisture and oxygen were handled under
argon. Commercially available reagents (Fluka, Aldrich) were
used as purchased, the solvents were distilled prior to use.
Synthesis of 1,1ꢀdiarylꢀ2,2,2ꢀtrichloroethanes 8—10 (generꢀ
al procedure). To a vigorously stirred mixture of arene (100 mmol)
and chloral (55 mmol), concentrated sulfuric acid (100 mL) was
added dropwise maintaining the temperature at 10—15 C. The
mixture was stirred at ambient temperature for 24 h. If after 24 h
the reaction did not achieve completion (TLC monitoring), the
mixture was heated at 50—60 C (water bath) for 5—7 h. After
completion of the reaction, the mixture was poured into ice
(
C 8.60) and its linear isomer 24 (C 7.96) is of note.
Apparently, this difference is due to that the C(11) proꢀ
tons in helicene are deviated from the molecular plane
and are in close spatial proximity. UV spectra of comꢀ
pounds 23—25 also exhibit noticeable difference (Fig. 1).
Lower extinction coefficient of helicene 25 as compared
with oligothiophene 24 can be explained by decrease in
conjugation caused by nonꢀplanarity of compound 25. In
the case of compound 23 with more fused benzene rings,
the extinction coefficient was higher.
In summary, we studied possibility to synthesize polyꢀ
aromatic compounds with thienothiophenic moiety by
the reactions of symmetric 2,2ꢀdiarylꢀ1,1ꢀdichloroethenes
with sulfur. This approach allow synthesis of oligoꢀ
thiophenes of both linear and helicene structures. As an
alternative to high temperature synthesis, the reaction
sequence involving lithiation of benzothienyldichloroꢀ
alkenes, treatment of the latter with sulfur and subsequent
ring closure can be employed. Despite the fact that these
approaches can be used to synthesize limited scope of
water. The organic products were extracted with CH Cl, the
organic layer was washed with 10% aqueous NaHCO (50 mL),
brine (50 mL), dried with Na SO , filtered through a thin layer
of silica gel, and concentrated in vacuo. The residue was recrysꢀ
3
3
2
4
tallized from toluene.
2
,2,2ꢀTrichloroꢀ1,1ꢀdi(4ꢀmethoxynaphthyl)ethane (8). Yield
3
5%, m.p. 255—256 C (cf. Ref. 14: m.p. 257 C).
2,2,2ꢀTrichloroꢀ1,1ꢀdi(4ꢀchloronaphthyl)ethane (9). Yield
40%, m.p. 222—223 C (cf. Ref. 15: m.p. 224 C).

1
460
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 7, July, 2012
Nenajdenko et al.
2
,2,2ꢀTrichloroꢀ1,1ꢀdi(4ꢀfluoronaphthyl)ethane (10). Yield
Di(2ꢀbenzothienyl) ketone (16). To a solution of benzoꢀ
thiophene (10 g, 75 mmol) in anhydrous diethyl ether (150 mL)
cooled to –20 C, 2.5 M BuLi in hexane (30 mL, 75 mmol) was
added over a period of 30 min. The mixture was warmed to 0 C
and kept for 1.5 h. Then, the mixture was reꢀcooled to –55 C
and a solution of N,Nꢀdimethylcarbamoyl chloride (4 g, 37 mmol)
in anhydrous diethyl ether (20 mL) was added within 2—3 min.
The mixture was allowed to warm to 0 C over 3.5—4 h and
quenched with 1 M HCl (70 mL). The organic layer was separatꢀ
ed, the aqueous layer was extracted with diethyl ether. The comꢀ
bined organics were dried with Na SO , the solvent was reꢀ
6
5%, m.p. 179—180 C. Found (%): C, 62.72; H, 3.22. C H Cl F .
Calculated (%): C, 62.66; H, 3.11. H NMR, : 6.79 (s, 1 H,
CH); 7.18 (t, 2 H, H(3), J = 9.6 Hz); 7.58 (m, 4 H, H(2), H(6));
.12 (q, 2 H, H(7), J = 1.0 Hz); 8.19 (d, 2 H, H(5), J = 8.0 Hz);
.36 (d, 2 H, H(8), J = 8.2 Hz). MS, m/z (I (%)): 420 [M] (6),
03 [M – CCl3] (100), 302 [M – CCl3 – H] (8), 286
M – CCl – H – F] (14).
Synthesis of 1,1ꢀdiarylꢀ2,2ꢀdichloroethenes 11—13 (general
procedure). To a solution of 1,1ꢀdiarylꢀ2,2,2ꢀtrichloroethane
22 13 3 2
1
8
8
3
+
rel
+
+
+
[
3
i
(
30 mmol) in Pr OH (0.5 L), a solution of KOH (60 mmol) in
2
4
anhydrous MeOH (10 mL) was added. The resulting mixture
was refluxed until completion of the reaction (TLC monitoring)
and poured into water (1 L). The precipitate formed was filtered
off, washed with water, dried, and recrystallized from toluene.
moved in vacuo. Recrystallization of the residue from toluene
afforded 7.72 g (70%) of di(2ꢀbenzothienyl) ketone 16, m.p.
170.5—171 C (cf. Ref. 18: m.p. 172—174 C).
Benzothiopheneꢀ3ꢀcarboxylic acid. To a solution of 3ꢀbromoꢀ
1
9
2
,2ꢀDichloroꢀ1,1ꢀdi(4ꢀmethoxynaphthyl)ethene (11). Yield
5%, m.p. 176—178 C (cf. Ref. 14: m.p. 180 C).
,2ꢀDichloroꢀ1,1ꢀdi(4ꢀchloronaphthyl)ethene (12). Yield
7%, m.p. 188—189 C (cf. Ref. 15: m.p. 190 C).
,2ꢀDichloroꢀ1,1ꢀdi(4ꢀfluoronaphthyl)ethene (13). Yield 95%,
m.p. 177—178 C. Found (%): C, 68.50; H, 3.30. C H Cl F .
benzothiophene (21.3 g, 100 mmol) in anhydrous diethyl ether
(250 mL) cooled to –70 C, 2.5 M BuLi in hexane (40 mL,
100 mmol) was added over a period of 5 min and the mixture was
stirred at –70 C for 30 min. The resulting suspension of
3ꢀbenzothienyllithium was added to a mixture of excess crashed
8
8
2
2
CO in anhydrous diethyl ether (250 mL) and then the reaction
2
2
12
2
2
2
1
Calculated (%): C, 68.59; H, 3.14. H NMR, : 7.07 (br.s, 2 H,
mixture was poured into 2 M HCl (400 mL). The organic layer
was separated, the aqueous phase was extracted with diethyl
ether (150 mL). The combined organics were washed with 2 M
KOH (3×150 mL). The basic solution was acidified with diluted
HCl. Crystals were collected and recrystallized from toluene to
give 15.2 g (85%) of benzothiopheneꢀ3ꢀcarboxylic acid, m.p.
175—176 C (cf. Ref. 20: m.p. 178—178.5 C).
H(3)); 7.31 (br.s, 2 H, H(4)); 7.65—7.78 (m, 4 H, H(6), H(7));
8
.20—8.34 (m, 2 H, H(5), H(8)). 13C NMR, : 109.2 (d, C(3),
J = 20.5 Hz); 121.4 (d, C(5), J = 5.1 Hz); 124.2 (d, C(4a),
J = 16.1 Hz); 125.3 (C(2), C(8)); 126.5 (C(6), C(7)); 128.0 (C(1),
C(8a)); 131.2 (CCl ); 133.6 (C=CCl ); 158.6 (d, C(4), J =
2
2
+
=
–
[
249.6 Hz). MS, m/z (I (%)): 384 [M] (61), 351 [M – CF –
rel
2 H] (20), 349 [M – Cl] (47), 348 [M – HCl] (13), 313
M – 2 Cl] (100), 310 [M – C H + 2 H] (19).
+
+
+
NꢀMethoxyꢀNꢀmethylbenzothiopheneꢀ3ꢀcarboxamide (18).
To a stirred solution of benzothiopheneꢀ3ꢀcarboxylic acid (7.13 g,
+
+
6 4
Di(1ꢀnaphthyl) ketone (14). To an iceꢀcold solution of
40 mmol) in CHCl (50 mL), 1,1ꢀcarbonyldiimidazole (7.78 g,
3
1
ꢀbromonaphthalene (20.7 g, 100 mmol) in anhydrous diethyl
48 mmol) was added portionwise. After gas evolution ceased, the
mixture was stirred for 15 min and N,Oꢀdimethylhydroxylamine
(4.68 g, 48 mmol) was slowly added. The reaction mixture was
stirred for 18 h, then water (50 mL) was added and stirring was
continued for 15 min. The organic layer was separated, washed
with 10% HCl, 10% aqueous NaOH, water, dried with Na SO ,
ether (300 mL), 2.5 M BuLi in hexane (40 mL, 100 mmol) was
added, the mixture was warmed to 15—20 C, and kept at this
temperature for 2 h. Then, the mixture was cooled to –50 C and
a solution of N,Nꢀdimethylcarbamoyl chloride (5.5 g, 51 mmol)
in anhydrous diethyl ether (30 mL) was added over a period of
2
4
2
—3 min. The reaction mixture was warmed to –30 C over 3 h
and filtered through a short layer of silica gel. Removal of the
solvent in vacuo afforded 5.9 g (66.7%) of NꢀmethoxyꢀNꢀmethylꢀ
benzothiopheneꢀ3ꢀcarboxamide 18, yellowish oil. Found (%):
C, 59.23; H, 5.22. C H NO S. Calculated (%): C, 59.71; H, 5.01.
and kept at this temperature for 2 h. Then, the mixture was
allowed to warm to 0 C and 1 M HCl (100 mL) was added. The
organic layer was separated, the aqueous phase was extracted
with dichloromethane (3×30 mL). The combined organics were
dried with Na SO , the solvent was removed in vacuo. Recrysꢀ
tallization of the residue from benzene afforded 17.8 g (63%) of
di(1ꢀnaphthyl) ketone 14, m.p. 104—104.5 C (cf. Ref. 16: m.p.
11
11
2
1
H NMR, : 3.41 (s, 3 H, NCH ); 3.58 (s, 3 H, OCH ); 7.38
3
3
(t, 1 H, H(6), J = 8.0 Hz); 7.44 (t, 1 H, H(5), J = 8.0 Hz); 7.87
(d, 1 H, H(7), J = 8.0 Hz); 8.05 (s, 1 H, H(2)); 8.25 (d, 1 H,
H(4), J = 8.0 Hz).
2
4
1
03 C).
Di(2ꢀnaphthyl) ketone (15). To an iceꢀcold solution of
ꢀbromonaphthalene (15.4 g, 74.4 mmol) in anhydrous diethyl
Di(3ꢀbenzothienyl) ketone (17). To a solution of 3ꢀbromobenzoꢀ
thiophene (9.62 g, 45 mmol) in anhydrous THF (30 mL), 2.25 M
2
suspension of Me CHMgCl•LiCl (21.2 mL, 48 mmol) in diꢀ
2
ether (200 mL), 2.5 M BuLi in hexane (30 mL, 75 mmol) was
added, the mixture was warmed to 15—20 C and kept at this
temperature for 3 h. Then the reaction mixture was cooled to
ethyl ether was added under argon and the mixture was stirred
for 18 h. Then NꢀmethoxyꢀNꢀmethylbenzothiopheneꢀ3ꢀcarboxꢀ
amide 18 (5 g, 23 mmol) in anhydrous THF (10 mL) was added
and stirring was continued for 24 h. The reaction mixture was
–
50 C and a solution of N,Nꢀdimethylcarbamoyl chloride
(
4.08 g, 37.9 mmol) in anhydrous diethyl ether (30 mL) was
diluted with saturated aqueous NH Cl (5 mL) and water (40 mL)
4
added over a period of 2—3 min. The temperature was allowed
to rise to ambient and the mixture was stirred for 16 h. Then 1 M
HCl (100 mL) was added, the organic layer was separated, the
aqueous phase was extracted with AcOEt (3×50 mL). The comꢀ
bined organics were dried with Na SO , the solvent was reꢀ
and extracted with CH Cl (3×30 mL). The combined organics
2
2
were dried with Na SO and the solvent was removed in vacuo.
2
4
Recrystallization of the residue from toluene afforded 5.3 g
(79.7%) of di(3ꢀbenzothienyl) ketone 17, m.p. 166—168 C
(cf. Ref. 14: 167—167.5 C).
2
4
moved in vacuo. Recrystallization of the residue from hexꢀ
ane—ethyl acetate afforded 3.8 g (36.6%) of di(2ꢀnaphthyl) keꢀ
tone 15, m.p. 160—161.5 C (cf. Ref. 17: m.p. 163 C).
Synthesis of 1,1ꢀdiarylꢀ2,2ꢀdichloroethenes 20—22 from diꢀ
aryl ketones (general procedure). To 2.5 M BuLi in hexane
(8.8 mL, 2.2 mmol) cooled to –78 C, a solution of hexamethylꢀ

Synthesis of annulated oligothiophenes
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 7, July, 2012
1461
disilazane (3.9 g, 2.4 mmol) in THF (20 mL) was slowly added.
The reaction mixture was slowly warmed to 0 C and reꢀcooled
to –78 C, subsequently a mixture of diethyl dichloromethylꢀ
phosphonate (4.42 g, 2 mmol) and diaryl ketone (2 mmol) in
THF (50 mL) was added dropwise. The mixture was stirred at
Benzothiopheno[3,2:4´,5´]thieno[3´,2´:4,5]thieno[2,3ꢀb]ꢀ
benzothiophene (25). Yield 25%, m.p. 244.5—245 C. Found (%):
C, 61.52; H, 2.27. C H S . Calculated (%): C, 61.33; H, 2.29.
18
8 4
1
UV (CHCl ),  /nm (): 245. H NMR, : 7.44 (t, 2 H, H(3),
3
max
H(10), J = 7.7 Hz); 7.57 (t, 2 H, H(5), H(9), J = 7.7 Hz); 7.94
–
78 C for 10 min and at ambient temperature for 16 h.
(d, 2 H, H(5), H(8), J = 8.0 Hz); 8.60 (d, 2 H, H(2), H(11),
13
The reaction was quenched with saturated aqueous NH Cl
and the mixture was extracted with diethyl ether (3×30 mL).
The organic layer was washed with water, dried with Na SO ,
the solvent was removed in vacuo, the residue was passed
through a short layer of silica gel (elution with hexane—dichloroꢀ
methane, 1 : 1).
J = 8.0 Hz). C NMR, : 123.4 (C(5), C(11)); 123.9 (C(2),
C(14)); 124.0 (C(3), C(13)); 124.4 (C(4), C(12)); 130.8 (C(1),
C(15)); 132.7 (C(6), C(8)); 133.0 (C(7), C(9)); 139.5 (C(16),
C(18)); 140.1 (C(8)); 143.2 (C(17)).
4
2
4
Benzothiopheno[3,2:4´,5´]thieno[3´,2´:4,5]thieno[2,3ꢀb]ꢀ
benzothiophene (25). To a solution of diisopropylamine (0.408 g,
4.02 mmol) in anhydrous THF (40 mL) cooled to –30 C, 2.5 M
BuLi in hexane (1.6 mL, 4 mmol) was added dropwise. The
mixture was stirred until temperature raised to 0 C and reꢀ
cooled to –78 C, then powdered sulfur (0.128 g, 4 mmol) was
added followed by slow addition of a solution of 2,2ꢀdichloroꢀ
1,1ꢀdi(3ꢀbenzothienyl)ethene 22 (0.722 g, 2 mmol) in anhyꢀ
drous THF (5 mL). The mixture was stirred at –78 C for 1 h and
at ambient temperature for 16 h. The reaction mixture was conꢀ
centrated in vacuo. To the residue, anhydrous DMF (50 mL) was
added and the mixture was heated at 80 C for 6 h with stirring.
2
,2ꢀDichloroꢀ1,1ꢀdi(1ꢀnaphthyl)ethene (20). Yield 17%.
1
H NMR, : 7.41 (m, 2 H, H(2)); 7.60 (m, 2 H, H(3)); 7.73 (m, 2 H,
H(7)); 7.83 (d, 2 H, H(5), J = 7.7 Hz); 7.92 (d, 2 H, H(6),
J = 7.7 Hz); 8.40 (m, 2 H, H(8)).14
2
,2ꢀDichloroꢀ1,1ꢀdi(2ꢀnaphthyl)ethene (21). Yield 68%.
1
H NMR, : 7.44 (dd, 2 H, H(7), H(8), J = 6.8 Hz, J = 1.8 Hz);
7
.49—7.54 (m, 4 H, H(6), H(9)); 7.82—7.88 (m, 8 H, H(1),
1
4
H(5), H(10), H(12)).
2
,2ꢀDichloroꢀ1,1ꢀdi(3ꢀbenzothienyl)ethene (22). Yield 75%,
m.p. 128.5—129 C. Found (%): C, 59.60; H, 3.00. C H Cl S .
Calculated (%): C, 59.84; H, 2.79. H NMR, : 7.35—7.40 (m, 4 H,
18
10
2 2
1
The reaction was quenched with saturated aqueous NH Cl
4
H(5), H(6)); 7.53 (s, 2 H, H(2)); 7.67—7.71 (m, 2 H, H(4));
(50 mL) and the mixture was extracted with CH Cl (3×100 mL).
The organic layer was dried with Na SO , the solvent was reꢀ
2 4
2
2
7
.87—7.91 (m, 2 H, H(7)). 13C NMR, : 122.9 (CCl ); 123.1
2
(
C(2)); 124.6 (C(7)); 124.6 (C(5)); 126.2 (C=CCl ); 126.8 (C(6));
moved in vacuo. Column chromatography of the residue (SiO2,
2
1
29.4 (C(4)); 133.7 (C(3a)); 136.9 (C(3)); 147.0 (C(7a)). MS, m/z
elution with hexane—CH Cl , 1 : 1) afforded 0.351 g (50%)
2
2
+
+
+
(
(
Irel (%)): 360 [M] (61), 326 [M – S – H] (8), 325 [M – Cl]
20), 324 [M – HCl] (12), 289 [M – 2 Cl]+ (100), 288 [M –
of benzothiopheno[3,2:4´,5´]thieno[3´,2´:4,5]thieno[2,3ꢀb]ꢀ
benzothiophene (25). Physicochemical parameters and spectral
properties of compound 25 are in agreement with that of the
sample synthesized by the general procedure (see above).
+
+
–
2 Cl – H] (24).
Synthesis of benzothiopheno[2,3ꢀb]benzothiophenes 4—6 and
2
3—25 (general procedure). A mixture of 1,1ꢀdiarylꢀ2,2ꢀdichloroꢀ
ethene (1 mmol) and sulfur (2 mmol) in 1,2,4ꢀtrichlorobenzene
0.6—0.8 mL) was heated at 220—225 C for 8—48 h. The reacꢀ
References
(
tion mixture was cooled down, pounded and dissolved in refluxꢀ
ing toluene (100—200 mL). The solution was cooled, the crystals
formed were filtered off and recrystallized from toluene.
Benzothiopheno[2,3ꢀb]benzothiophene (4). Yield 70%, m.p.
1. O. K. Kim, H. Y. Woo, K. S. Lee, K. S. Kim, K. S. Shim,
C. Y. Kim, Synth. Met., 2001, 121, 1607.
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34, 1119.
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J. Am. Chem. Soc., 1998, 120, 2206.
1
5
5
40—141 C (cf. Ref. 8: m.p. 138—139 C).
,8ꢀDibromobenzothiopheno[2,3ꢀb]benzothiophene (5). Yield
0%, m.p. 280—282 C (cf. Ref. 8: m.p. 283—284 C).
,8ꢀDichlorobenzothiopheno[2,3ꢀb]benzothiophene (6). Yield
3
3
3%, m.p. 265—266 C (cf. Ref. 8: m.p. 268 C).
Naphtho[1,2ꢀb]naphtho[2´,1´:4,5]thieno[3,2ꢀd]thiophene
(
2
23). Yield 27%, m.p. 355—356.5 C. UV (CHCl ), max/nm ():
60, 280. H NMR, : 7.53 (t, 2 H, J = 6.0 Hz); 7.61 (t, 2 H,
5. M. Fujitsuka, T. Sato, A. Watanabe, O. Ito, T. Shimidzu,
Chem. Lett., 1996, 285.
3
1
J = 6.0 Hz); 7.95 (d, 2 H, J = 10.0 Hz); 8.00 (d, 2 H, J = 8.0 Hz);
6. (a) K. Yu. Chernichenko, V. V. Sumerin, R. V. Shpanchenko,
E. S. Balenkova, V. G. Nenajdenko, Angew. Chem., Int. Ed.,
2006, 45, 7367; (b) K. Yu. Chernichenko, E. S. Balenkova,
V. G. Nenajdenko, Mendeleev Commun., 2008, 18, 171;
(c) A. Dadvand, F. Cicoira, K. Yu. Chernichenko, E. S.
Balenkova, R. M. Osuna, V. H. Jolin, F. Rosei, V. G. Nenajꢀ
denko, D. F. Perepichka, Chem. Commun., 2008, 5354;
(d) O. Ivasenko, J. M. MacLeod, K. Chernichenko, E. Balenꢀ
kova, R. V. Shpanchenko, V. G. Nenajdenko, F. Rosei,
D. F. Perepichka, Chem. Commun., 2009, 1192; (e) S. S. Buꢀ
kalov, L. A. Leites, K. A. Lyssenko, R. R. Aysin, A. A. Korꢀ
lyukov, J. V. Zubavichus, K. Chernichenko, E. S. Balenkoꢀ
va, V. G. Nenajdenko, M. Yu. Antipin, J. Phys. Chem. A.,
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I. Gridnev, V. G. Nenajdenko, Tetrahedron, 2011, 67, 6812.
13
8
.08 (d, 2 H, J = 10.0 Hz); 8.50 (d, 2 H, J = 8.0 Hz). C NMR
spectrum of compound 23 was not recorded because of its low
+
2+
solubility. MS, m/z (Irel (%)): 340 [M] (100), 170 [M] (40).
Benzothiopheno[2,3:4´,5´]thieno[3´,2´:4,5]thieno[3,2ꢀb]ꢀ
benzothiophene (24). Yield 47%, m.p. 313—314.5 C. Found (%):
C, 61.38; H, 2.48. C H S . Calculated (%): C, 61.33; H, 2.29.
1
8
8 4
1
UV (CHCl ),  /nm (): 257, 304. H NMR, : 7.42 (t, 2 H,
3
max
H(3), H(10), J = 8.0 Hz); 7.50 (t, 2 H, H(4), H(9), J = 8.0 Hz);
7
.90 (d, 2 H, H(5), H(8), J = 8.0 Hz); 7.96 (d, 2 H, H(2), H(11),
13
J = 8.0 Hz). C NMR, : 120.6 (C(5), C(11)); 124.2 (C(2),
C(14)); 124.6 (C(3), C(13)); 125.1 (C(4), C(12)); 127.7 (C(1),
C(15)); 128.5 (C(6), C(8)); 133.2 (C(7), C(9)); 136.1 (C(16),
C(18)); 136.3 (C(8)); 141.8 (C(17)). MS, m/z (I (%)): 352
rel
+
2+
[
M] (100), 176 [M] (63).

1
462
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(
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(
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2
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1
9
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0. (a) V. N. Korotchenko, V. G. Nenajdenko, A. V. Shastin,
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2
004, 73, 1039]; (b) V. G. Nenajdenko, V. N. Korotchenko,
in revised form June 27, 2012