2-[2-(1-benzoyl-4-methyldibenzo- thienyl-2)benzo[b]thienyl-3]phenyl- 1-ethanone - A new product of the reaction of 1-methyl-3-phenylbenzo- thieno[2,3-c]pyrilium perchlorate with nucleophilic reagents

Article abstract of DOI:10.1007/s10593-009-0380-x

On the interaction of 1-methyl-3-phenylbenzothieno[2,3-c]pyrilium perchlorate with primary and secondary amines and alkalis in aqueous media a product of cyclocondensation of 2-acetyl-3-phenacyl-benzo[b]thiophene - 2-[2-(1-benzoyl-4-methyldibenzothienyl-2

Full text of DOI:10.1007/s10593-009-0380-x

Chemistry of Heterocyclic Compounds, Vol. 45, No. 8, 2009
2-[2-(1-BENZOYL-4-METHYLDIBENZO-
THIENYL-2)BENZO[b]THIENYL-3]PHENYL-
1-ETHANONE – A NEW PRODUCT OF THE
REACTION OF 1-METHYL-3-PHENYLBENZO-
THIENO[2,3-c]PYRILIUM PERCHLORATE
WITH NUCLEOPHILIC REAGENTS
S. V. Tolkunov1*, M. A. Kryuchkov1, R. I. Zubatyuk2, and O. V. Shishkin2
On the interaction of 1-methyl-3-phenylbenzothieno[2,3-c]pyrilium perchlorate with primary and
secondary amines and alkalis in aqueous media a product of cyclocondensation of 2-acetyl-3-phenacyl-
benzo[b]thiophene – 2-[2-(1-benzoyl-4-methyldibenzothienyl-2)benzo[b]thienyl-3]phenyl-1-ethanone –
was isolated in addition to the classical objects of recyclization.
Keywords: 2-[2-(1-benzoyl-4-methyldibenzothienyl-2)benzo(b)thienyl-3]phenyl-1-ethanone, benzothieno-
[2,3-c]pyrilium, recyclization, X-ray crystallography.
Recyclization of benzo[c]pyrylium salts with primary and secondary amines and alkalis is widely used
in preparative chemistry to prepare derivatives of naphthalene [1,2]. Analogous recyclization of benzofuro-
[2,3-c]pyrylium and benzothieno[2,3-c]pyrylium salts with primary and secondary amines allowed the
preparation of large series of 4-R-aminodibenzothiophenes and dibenzofurans [3-6]. It is considered that these
conversions proceed via the ANRORC scheme.
However along with the addition of nucleophiles to pyrylium salts concurrent reactions can occur,
linked with 1,1'- and 4,1'-dimerization of pyrylium salts which was first shown by Rostov chemists with the
example of the reaction of 1,3-disubstituted benzo[c]pyrylium salts with alkalis [7, 8].
The mechanism of 1,1'-dimerization of 1,3-dimethylbenzo[c]pyrylium perchlorate is connected with
deprotonation of 1-alkyl group with the formation of anhydro base which cannot take part in the formation of
classical products of recyclization and tend to dimerize with further conversion into substituted chrysenes. At
the same time hydrolysis of pyrylium salts to 1,5-dicarbonyl compounds and their conversion into naphthols
also occurs [7].
_______
* To whom correspondence should be addressed, e-mail: s_tolkunov@yahoo.com.
1L. M. Litvinenko Institute of Physical Organic and Coal Chemistry National Academy of Sciences of Ukraine,
Donetsk 83114, Ukraine.
2Institute for Single Crystals, National Academy of Sciences of Ukraine, Kharkiv 61001, Ukraine.
__________________________________________________________________________________________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, 1244-1252, August, 2009. Original
article submitted March 11, 2008.
990
0009-3122/09/4508-0990©2009 Springer Science+Business Media, Inc.

In studying the interaction of 1-methyl-3-phenylbenzothieno[2,3-c]pyrylium perchlorate (1) with
ammonium acetate, primary and secondary amines, we observed that along with the normal products of
recyclization which contain in their structure the nucleophile used – 4-morpholino-2-phenyldibenzothiophene
(2), 1-methyl-3-phenylbenzothieno[2,3-c]pyridine (4) [9], and 4-benzylamino-2-phenyldibenzothiophene (5)
[6] – a by-product was formed, the structure of which was not connected with the nucleophile used and which
contained no nitrogen according to elemental analysis.
O
Ph
Ph
O
Ph
HN
H2O
O
Ph
S
+
O
+
_
S
ClO4
S
S
Me
1
N
O
Me
2
3
Ph
Ph
AcONH4
PhCH2NH2
EtOH/H2O
1
3
1
+
3
+
N
AcOH/H2O
S
S
Me
Ph
HN
4
5
X-ray structural analysis of the compound showed that it was 2-[2-(1-benzoyl-4-methyldibenzothienyl-2)-
benzo[b]thienyl-3]phenyl-1-ethanone (3). In the molecule studied (Fig. 1) the dibenzothiophene unit is not
planar, the angle between the benzene rings C(1)···C(6) and C(7)···C(12) is 6°. This is probably explained by
intermolecular stacking interactions of base molecule and molecule connected by the symmetry operation (1-x,
-y, 3-z) in which only two of the three condensed rings take part (X(1)···X(2)' 3.851, X(2)···X(1)' 3.851, where
X(1) and X(2) are centers of the rings C(7)···C(12) and C(1),C(6),S(1)C(7), C(12) respectively, the planes of the
Fig. 1. Structure of the molecule 2-[2-(1-benzoyl-4-methylbenzothienyl-2)-
benzo(b)thienyl-3]phenyl-1-ethanone (3) based on X-ray structural data.
991

rings are strictly parallel, Fig. 2). The carbon atom of the methyl group C(36) lies practically in the plane of the
benzene ring C(7)···C(12) (torsion angle C(36)–C(8)–C(9) 177.8(2)°) while the atom C(29) is lightly deflected
from this (torsion angle C(29)–C(11)–C(12)–C(7) 172.2(2)°).The benzothiophene unit is planar with a precision
of 0.004 Å.
Fig. 2. Dimers in the crystals of compound 3 formed by intermolecular stacking
interactions of a molecule with a second molecule connected by the symmetry
operation (1-x, -y, 3-z).
The bicyclic and tricyclic fragments are strongly rotated relatively to one another (torsional angle C(9)–
C(10)–C(13)–S(2) 59.2(3)°) which results in some lengthening of the C(10)–C(13) bond to 1.476(3) Å (mean
bond length 1.455 Å [10]). The oxo groups are somewhat deflected from the planes of the corresponding phenyl
substituents (torsion angles O(1)–C(22)–C(23)–C(28) 8.4(4)° and O(2)–C(29)–C(30)–C(35) 18.6(4) Å). The
aromatic rings C(30)···C(35) and C(23)···C(28) are practically perpendicular relative to the tricyclic and bicyclic
units (angles between the planes are 82.3 and 74.7° respectively) despite the fact that this orientation leads to the
shortening of the intermolecular contacts H(24)···H(18) to 2.18 (sum of the van der Waals radii 2.32 [11]) and
H(31)···C(11) to 2.59 Å (2.87 Å). In the crystal the molecules of compound 3 form ribbons as a result of very
weak hydrogen bonds C(5)–H(5)···O(1)' (1-x, -y, 3-z) (H···O 2.51 Å, C–H···O 153°) and C(17)–H(17)···O(2)'
(1-x, 1-y, 2-z) (H···O 2.53 Å, C–H···O 160°).
We consider that the factor which determines the formation of compound 3 is the presence of traces of
water in the reaction medium. In fact recyclization of perchlorate 1 in excess of dry morpholine led to
4-morpholino-2-phenylbenzothiophene (4) with minimal impurities of compound 3. In contrast reaction of
perchlorate 1 with morpholine in aqueous alcohol led to preferential formation of compound 3. We observed
analogous behavior on the interaction of perchlorate 1 with a primary amines (benzylamine) in ethanol when the
yield of compound 3 varied from 10 to 15%. Similarly recyclization of perchlorate 1 with ammonium acetate in
80% acetic acid gave 30% of compound 3.
There are no reports in the literature on the formation of compounds of type 3 in reactions of pyrylium
salts with nitrogen nucleophiles. In papers on the recyclization of 1,3-dimethylbenzo[c]pyrylium perchlorate
with alkali the following sequence was described for the formation of chrysenes: pyrylium → dimer →
chrysene; and the side process: pyrylium → 1,5-dicarbonyl compound →naphthol. So the authors considered the
formation of chrysene from 1,5-dicarbonyl compounds was impossible [7].
992

Assuming that the mechanism of formation of compound 3 may be analogous to the formation of chrysenes
from 1,3-dimethylbenzo[c]pyrylium perchlorate, we proposed to obtain dimers of analogous structure from
perchlorate 1 under conditions of hydrolysis (sodium acetate–water) as described in [7]. However we isolated a
mixture of 2-acetyl-3-phenacylbenzo[b]thiophene (6) (42% yield), 4-hydroxy-3-phenyldibenzothiophene (7) (21%
yield), and 2-[2-(1-benzoyl-4-methyldibenzothienyl-2)benzo[b]thienyl-3]phenyl-1-ethanone (17% yield).
Ph
Ph
AcONa
+
O
O
1
+
3
EtOH/H2O
S
S
Me
OH
7
6
Further study of the reaction of 2-acetyl-3-phenacylbenzo[b]thiophene (6) with alkalis, primary and
secondary amines showed that just this compound was the precursor of dibenzothiophene 3. For example,
heating compound 6 with aqueous alcoholic KOH gave a mixture of 4-hydroxy-2-phenyldibenzothiophene (7) and
2-[2-(1-benzoyl-4-methyldibenzothienyl-2)benzo[b]phenyl-1-ethanone (3) (44 and 33% yields respectively), and
interaction of compound 6 with benzylamine gave a mixture of compound 7 (43), 5 (32), and 3 (11%).
O
Ph
Ph
p-MeC6H4SO3H
S
3
S
Me
8
Table 1. Bond Lengths (l) in the Molecule of Compound 3
Bond
S(1)–C(7)
l, Å
Bond
l, Å
1.741(2)
1.742(3)
1.736(3)
1.744(3)
1.210(3)
1.220(3)
1.397(3)
1.406(3)
1.461(3)
1.361(4)
1.394(4)
1.360(4)
1.398(4)
1.403(3)
1.403(3)
1.374(3)
1.497(3)
1.402(3)
1.394(3)
1.476(3)
1.410(3)
1.508(3)
1.366(3)
C(14)–C(15)
C(14)–C(21)
C(15)–C(20)
C(15)–C(16)
C(16)–C(17)
C(17)–C(18)
C(18)–C(19)
C(19)–C(20)
C(21)–C(22)
C(22)–C(23)
C(23)–C(24)
C(23)–C(28)
C(24)–C(25)
C(25)–C(26)
C(26)–C(27)
C(27)–C(28)
C(29)–C(30)
C(30)–C(31)
C(30)–C(35)
C(31)–C(32)
C(32)–C(33)
C(33)–C(34)
C(34)–C(35)
1.440(3)
1.491(3)
1.398(4)
1.404(3)
1.372(4)
1.375(4)
1.382(4)
1.392(4)
1.514(4)
1.493(4)
1.387(4)
1.389(4)
1.380(4)
1.368(5)
1.360(5)
1.382(4)
1.481(4)
1.374(4)
1.392(4)
1.391(4)
1.356(6)
1.367(6)
1.360(5)
S(1)–C(6)
S(2)–C(20)
S(2)–C(13)
O(1)–C(22)
O(2)–C(29)
C(1)–C(2)
C(1)–C(6)
C(1)–C(12)
C(2)–C(3)
C(3)–C(4)
C(4)–C(5)
C(5)–C(6)
C(7)–C(12)
C(7)–C(8)
C(8)–C(9)
C(8)–C(36)
C(9)–C(10)
C(10)–C(11)
C(10)–C(13)
C(11)–C(12)
C(11)–C(29)
C(13)–C(14)
993

Table 2. Bond Angles (ω) in the Structure of Compound 3
Angle
ω, deg
Angle
ω, deg
C(7)–S(1)–C(6)
91.1(1)
91.7(1)
C(20)–C(15)–C(16)
C(20)–C(15)–C(14)
C(16)–C(15)–C(14)
C(17)–C(16)–C(15)
C(16)–C(17)–C(18)
C(17)–C(18)–C(19)
C(17)–C(18)–C(19)
C(18)–C(19)–C(20)
C(19)–C(20)–C(15)
C(19)–C(20)–S(2)
C(15)–C(20)–S(2)
C(14)–C(21)–C(22)
O(1)–C(22)–C(23)
O(1)–C(22)–C(21)
C(23)–C(22)–C(21)
C(24)–C(23)–C(28)
C(24)–C(23)–C(22)
C(28)–C(23)–C(22)
C(25)–C(24)–C(23)
C(26)–C(25)–C(24)
C(27)–C(26)–C(25)
C(26)–C(27)–C(28)
C(27)–C(28)–C(23)
O(2)–C(29)–C(30)
O(2)–C(29)–C(11)
C(30)–C(29)–C(11)
C(31)–C(30)–C(35)
C(31)–C(30)–C(29)
C(35)–C(30)–C(29)
C(30)–C(31)–C(32)
C(33)–C(32)–C(31)
C(32)–C(33)–C(34)
C(35)–C(34)–C(33)
C(34)–C(35)–C(30)
118.2(2)
112.8(2)
129.0(2)
119.5(3)
121.2(3)
121.3(3)
121.3(3)
117.6(3)
122.2(2)
126.9(2)
110.9(2)
113.1(2)
120.1(3)
120.6(2)
119.3(2)
117.9(3)
123.1(2)
119.0(2)
121.0(3)
120.0(3)
119.9(3)
120.9(3)
120.3(3)
121.8(2)
120.8(2)
117.4(2)
118.4(3)
121.8(2)
119.8(3)
120.3(3)
120.0(4)
120.2(4)
120.5(4)
120.6(4)
C(20)–S(2)–C(13)
C(2)–C(1)–C(6)
C(2)–C(1)–C(12)
C(6)–C(1)–C(12)
C(3)–C(2)–C(1)
C(3)–C(2)–C(1)
C(2)–C(3)–C(4)
C(5)–C(4)–C(3)
C(4)–C(5)–C(6)
C(5)–C(6)–C(1)
C(5)–C(6)–S(1)
117.8(2)
130.9(2)
111.3(2)
120.4(3)
120.4(3)
120.8(3)
121.0(3)
118.3(3)
121.7(2)
125.2(2)
113.0(2)
123.0(2)
113.0(2)
124.0(2)
116.6(2)
121.3(2)
122.0(2)
122.6(2)
120.1(2)
120.7(2)
119.2(2)
119.2(2)
118.5(2)
122.2(2)
118.4(2)
111.6(2)
130.0(2)
129.8(2)
112.5(2)
117.7(2)
112.1(2)
126.2(2)
121.6(2)
C(1)–C(6)–S(1)
C(12)–C(7)–C(8)
C(12)–C(7)–S(1)
C(8)–C(7)–S(1)
C(9)-C(8)–C(7)
C(9)–C(8)–C(36)
C(7)–C(8)–C(36)
C(8)–C(9)–C(10)
C(11)–C(10)–C(9)
C(11)–C(10)–C(13)
C(9)–C(10)–C(13)
C(10)–C(11)–C(12)
C(10)–C(11)–C(29)
C(12)–C(11)–C(29)
C(7)–C(12)–C(11)
C(7)–C(12)–C(1)
C(11)–C(12)–C(1)
C(14)–C(13)–C(10)
C(14)–C(13)–S(2)
C(10)–C(13)–S(2)
C(13)–C(14)–C(15)
C(13)–C(14)–C(21)
C(15)–C(14)–C(21)
Apparently the formation of structure 3 occurs as a result of intermolecular crotonic condensation of two
molecules of compound 6.
Subsequent intramolecular cyclization of compound 3, in contrast to its benzoid analogs [7], occurs
exclusively in acid media, for example, on boiling compound 3 in toluene in the presence of p-toluenesulfonic acid.
The results obtained show that the formation of polycondensed compounds on recyclization pyrylium
salts with nucleophiles may also occur via intermolecular crotonic condensation of two molecules of 1,5-di-
carboxylic compounds formed as the result of hydrolysis of the initial pyrylium salts.
EXPERIMENTAL
1H NMR spectra of DMSO-d6 solutions with TMS as internal standard were recorded on a Gemini-200
(200 MHz) and Bruker DRX500 (500 MHz) spectrometers. The course of reactions and purity of products were
monitored by TLC on Silufol UV-254 plates and preparative chromatography on Merck 60 silica gel with
chloroform as eluent.
994

X-ray Crystallographic Study. Triclinic crystals of compound 3, grown from DMF, C36H24O2S2, at
20°C: a = 9.843(3), b = 10.968(3), c = 13.349(3) Å, α = 79.88(2)°, β = 79.11(2)°, γ = 81.26(2)°, V = 1383(1) Å3,
–
Mr = 552.67, Z = 2, space group P , dcalc = 1.328 g/cm3, µ(MoKα) = 0.225 mm-1, F(000) = 576. Parameters of
1
the unit cell and intensities of 5191 reflections (4888 independent, Rint = 0.035) were measured on a Siemens
P3/PC automatic four circle diffractometer (MoKα, graphite monochromator, 2θ/θ scanning, 2θmax = 50°).
The structure was solved by direct methods using the SHELXTL program [12]. Positions of the
hydrogen atoms were revealed by an electron density difference synthesis and refined by the "riding" method
with Uiso = nUeq for the non-hydrogen atom bonded to the hydrogen atom (n = 1.5 for a methyl group and n = 1.2
for the other hydrogen atoms). The structure was refined with respect to F2 by full matrix least squares analysis
in the anisotropic approximation for non-hydrogen atoms to wR2 = 0.118 for 4829 reflections (R1 = -0.044 for
2927 reflections with F > 4σ(F), S = 1.019). Final atomic coordinates have been deposited in the Cambridge
Bank of Structural Data (CCDC 736226). Bond lengths and bond angles are cited in Tables 1 and 2.
Interaction of 1-Methyl-3-phenylbenzothieno[2,3-c]pyrylium Perchlorate (1) with Morpholine
(General Method). A. A mixture of pyrylium salt 1 (0.8 g, 2.1 mmol) and dry morpholine (4 ml) was boiled for
5 h. The morpholine was removed in vacuum. The residue was triturated with water, filtered, and washed with
water to give 4-morpholino-2-phenyldibenzothiophene (2) (0.65 g, 90%); mp 122-123°C (ethanol), Rf 0.15
1
(eluent chloroform). H NMR spectrum, δ, ppm (J, Hz): 3.23 (4H, m, CH2–morpholine); 3.87 (4H, m,
CH2-morpholine); 7.35-7.50 (7H, m, H-7,8, H-C6H5); 7.78 (1H, s, H-2); 7.97 (1H, dd, J = 8.4, J = 1.9, H-9);
8.27 (1H, s, H-1); 8.40 (1H, dd, J = 8.4, J = 1.9, H-6). Found, %: C 76.71; H 5.39; N 4.15; S 9.39. C22H19NOS.
Calculated, %: C 76.49; H 5.54; N 4.05; S 9.28.
B. A solution of pyrylium salt 1 (0.8 g, 2.1 mmol) in ethanol (20 ml) containing morpholine (1 ml) was
boiled for 5 h. The solvent was evaporated in vacuum. The residue was triturated with water, filtered, and
washed with water. It was purified by column chromatography (silica gel 60, 3×16 cm column, eluent
chloroform) to give compounds 2, 3, and 7.
2-[2-(1-Benzoyl-4-methyldibenzothienyl-2)benzo[b]thienyl-3]phenyl-1-ethanone (3). Yield 0.35 g
1
(30%); Rf 0.8, mp 198-199°C (DMF). H NMR spectrum, δ, ppm: 2.63 (3H, s, CH3); 4.29-4.41 (2H, m, CH2);
7.18-7.96 (19H, m, H-arom). Found, %: C 78.49; H 4.47; S 11.42. C36H24O2S2. Calculated, %: C 78.23; H 4.38;
S 11.60.
4-Morpholino-2-phenyldibenzothiophene (2). Yield 0.03 g (4%). Compound 2 was identical
spectroscopically and by Rf with the substance obtained by method A and a mixed melting point showed no
depression.
1
4-Hydroxy-2-phenyldibenzothiophene (7). Yield 0.21 g (36%); Rf 0.26, mp 180-181°C. H NMR
spectrum, δ, ppm: 5.45 (1H, s, OH); 7.1 (1H, s, H-2); 7.33-7.55 (5H, m, Ar); 7.60-7.70 (2H, m, H-5,8);
7.81-7.93 (1H, m, H-5); 7.97 (1H, s, H-4); 8.12-8.24 (1H, s, H-8). Found, %: C 78.45; H 4.52; S 11.39.
C18H12OS. Calculated, %: C 78.23; H 4.38; S 11.60.
Interaction of 1-Methyl-3-phenylbenzothieno[2,3-c]pyrylium Perchlorate (1) with benzylamine and
ammonium acetate was carried out by a known method [6, 9].
Interaction of 1-Methyl-3-phenylbenzothieno[2,3-c]pyrylium Perchlorate (1) with Sodium Acetate
(General Method). A suspension of pyrylium salt 1 (0.8 g, 2.1 mmol) in a solution of AcONa (0.5 g) in 50%
2-propanol was stirred for 24 h at room temperature. The residue was filtered off, washed with water, 50%
2-propanol, and dried. It was purified by column chromatography (silica gel 60, 3×16 cm column, chloroform
eluent). Three fractions were collected, the solvent removed at low pressure, to give compounds 3, 6, and 7.
2-[2-(1-Benzoyl-4-methyldibenzothienyl-2)benzo[b]thienyl-3]phenyl-1-ethanone (3). Yield 0.1 g
(17%); Rf 0.8, mp 198-199°C (DMF).
1
2-Acetyl-3-phenacylbenzo[b]thiophene (6). Yield 0.25 g (42%); Rf 0.52, mp 150-151°C (ethanol). H
NMR spectrum, δ, ppm: 2.58 (3H, s, CH3); 5.04 (2H, s, CH2); 7.19-7.79 (5H, m, H-Ar); 7.81-8.02 (2H, m,
H-6,7); 8.02-8.28 (2H, m, H-5,8). Found, %: C 73.59; H 4.61; S 10.57. C18H14O2S. Calculated, %: C 73.44;
H 4.79; S 10.89.
995

1-Hydroxy-3-phenyldibenzothiophene (7). Yield 0.12 g (21%); Rf 0.26, mp 180-181°C.
Compounds 3 and 7 were identical spectroscopically and by Rf with those obtained by interaction of
compound 1 with morpholine by method B, and mixed melting points gave no depression.
Interaction of 2-Acetyl-3-phenacylbenzothiophene (6) with Potassium Hydroxide (General
Method). A solution of KOH (0.1 g, 1.8 mmol) in water (1 ml) was added to a solution of compound 2 (0.2 g,
0.7 mmol) in methanol (5 ml) and the reaction mixture was boiled for 3 h. It was cooled, diluted with water
(50 ml) and acidified with 10% hydrochloric acid until acid. The precipitate was filtered off, washed with water,
and dried. The mixture was separated by column chromatography (silica gel 60, column 3×16 cm, eluent
chloroform) to give compounds 3, 7, and 8.
2-[2-(1-Benzoyl-4-methyldibenzothienyl-2)benzo[b]thienyl-3]phenyl-1-ethanone (3). Yield 0.06 g
(33%); mp 198-199°C (DMF).
1-Hydroxy-3-phenyldibenzothiophene (7). Yield 0.08 g (44%); mp 180-181°C. Compounds 3 and 7
were identical spectroscopically and by Rf to compounds obtained by interaction of compound 1 with
morpholine by method B and mixed melting points gave no depression.
14-Benzoyl-7-methyl-13-phenylbisbenzo[b]thieno[1,2:6,5]naphthalene (8). A solution of compound
3 (0.55 g, 10 mmol) in toluene (10 ml) and p-toluenesulfonic acid (10 mg) was boiled for 10 h until complete
disappearance (TLC) of the starting compound 3. The toluene was removed in vacuum. The residue was washed
with water and crystallized from a mixture of toluene and hexane. Yield 0.41 g (77%); mp 257-258°C. 1H NMR
spectrum, δ, ppm: 2.60 (3H, s, CH3); 7.18-7.96 (19H, m, H arom). Found, %: C 80.61; H 4.27; S 11.71.
C36H22OS2. Calculated, %: C 80.87; H 4.15; S 11.90.
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