(E)-3-(Benzo[b]thiophen-2-yl)-2-(3,4,5-trimethoxyphenyl)acrylonitrile and (Z)-3-(benzo[b]thiophen-2-yl)-2-(3,4-dimethoxyphenyl)acrylonitrile

Article abstract of DOI:10.1107/S0108270107054959

The title compounds, C20H17NO3S, (I), and C19H15NO2S, (II), were prepared by the reaction of benzo[b]thio-phene-2-carbaldehyde with (3,4,5-trimethoxy- phenyl)-acetonitrile and (3,4-dimethoxy-phenyl)-acetonitrile, respectively, in the presence of methanoli

Full text of DOI:10.1107/S0108270107054959

organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
series of novel substituted aryl/heteroarylacrylonitriles.
Compounds (I) and (II) were prepared by the reaction of
benzo[b]thiophene-2-carboxaldehyde with (3,4,5-trimethoxy-
phenyl)acetonitrile and (3,4-dimethoxyphenyl)acetonitrile in
the presence of methanolic potassium hydroxide under re¯ux.
In order to obtain detailed information on the structural
conformation of these molecules and to con®rm the geometry,
their X-ray structure determination has been carried out.
Recrystallization from ethyl acetate afforded yellow needles
of (I) that were suitable for X-ray analysis, but (II) afforded
yellow silky needles that were not suitable for X-ray analysis.
Furthermore, when (II) was crystallized from a mixture of
ethyl acetate and chloroform by slow evaporation at room
temperature over a period of one week, a mixture of yellow
crystals (®ne silky crystals as well as crystalline hexagons) was
obtained.
ISSN 0108-2701
(E)-3-(Benzo[b]thiophen-2-yl)-2-
(3,4,5-trimethoxyphenyl)acrylonitrile
and (Z)-3-(benzo[b]thiophen-2-yl)-2-
(3,4-dimethoxyphenyl)acrylonitrile
Vijayakumar N. Sonar,a Sean Parkinb and Peter A.
Crooksa*
aDepartment of Pharmaceutical Sciences, College of Pharmacy, University of
Kentucky, Lexington, KY 40536, USA, and bDepartment of Chemistry, University of
Kentucky, Lexington, KY 40506, USA
Correspondence e-mail: pcrooks@email.uky.edu
Received 8 October 2007
Accepted 31 October 2007
Online 24 November 2007
The title compounds, C20H17NO3S, (I), and C19H15NO2S, (II),
were prepared by the reaction of benzo[b]thiophene-2-
carbaldehyde with (3,4,5-trimethoxyphenyl)acetonitrile and
(3,4-dimethoxyphenyl)acetonitrile, respectively, in the
presence of methanolic potassium hydroxide. In (I), the
C
C bond linking the benzo[b]thiophene and the 3,4,5-
The molecular structure and the atom-numbering scheme of
(I) are shown in Fig. 1; selected bond lengths and angles are
listed in Table 1. In (I), the ole®nic bond connecting the 3,4,5-
trimethoxyphenyl and benzo[b]thiophene ring systems has E
geometry. Signi®cant deviations from the ideal bond-angle
geometry around the Csp2 atoms of the double bond are
observed. The C11ÐC10ÐC17, C10 C9ÐC1, and C9ÐC1Ð
S1 bond angles [115.92 (16), 130.57 (17), and 125.51 (14)ꢀ,
respectively] are distorted owing to steric hindrance of the
double bond linking the two ring systems. Neither the
benzo[b]thiophene ring nor the benzene ring of the 3,4,5-tri-
methoxyphenyl group is coplanar with the vinyl double bond,
trimethoxyphenyl units has E geometry, with dihedral angles
between the plane of the bridging unit and the planes of the
two adjacent ring systems of 5.2 (3) and 13.1 (2)ꢀ, respectively.
However, in (II), the C C bond has Z geometry, with
dihedral angles between the plane of the bridging unit and the
planes of the adjacent benzo[b]thiophene and 3,4-dimethoxy-
phenyl units of 4.84 (17) and 76.09 (7)ꢀ, respectively. There are
no signi®cant intermolecular hydrogen-bonding interactions
in the packing of (I) and (II). The packing is essentially
stabilized via van der Waals forces.
Comment
2,3-Diarylacrylonitriles are very important synthons for the
synthesis of a wide spectrum of biologically active molecules
(Loupy et al., 2005). These compounds have been shown to
possess spasmolytic, estrogenic, hypotensive, antioxidative,
tuberculostatic, antitrichomonal, insecticidal and cytotoxic
activities (Saczewski et al., 2004). Compounds of general
structure 1 (see scheme) undergo interconversion to the
corresponding E isomer in solution under certain conditions;
the behavior of such compounds is dependent on the nature of
the two groups linked across the double bond carrying the
nitrile group, i.e. whether ꢀ-excessive (donating) or ꢀ-de®cient
(accepting). Normally, base-catalyzed condensation of aryl/
heteroarylaldehydes with aryl/heteroarylacetonitriles leads to
the formation of the Z isomer, but isomerism to the E form
can be readily monitored by NMR studies. In connection with
our ongoing research, we have undertaken the synthesis of a
Figure 1
A view of the asymmetric unit of (I), with displacement ellipsoids drawn
at the 50% probability level and H atoms shown as small spheres of
arbitrary radii.
Acta Cryst. (2007). C63, o743±o745
DOI: 10.1107/S0108270107054959
# 2007 International Union of Crystallography o743

organic compounds
making dihedral angles of 5.2 (3) and 13.1 (2)ꢀ, respectively.
Ê
The C9 C10 double bond [1.366 (2) A] in (I) is slightly
longer than that observed in the disubstituted ole®nic group of
dimethoxyphenyl ring is twisted with respect to the plane of
the benzo[b]thiophene ring system. The 3,4-dimethoxyphenyl
and benzo[b]thiophene planes make dihedral angles of
76.09 (7) and 4.84 (17)ꢀ, respectively, with the plane of the
central vinyl unit. In (II), the bridging unit C9 C10
Ê
2-styrylbenzimidazole [1.304 (4) A; Bacelo et al., 1997],
suggesting some delocalization in the unsaturated bridging
units. This fact is further supported by the C1ÐC9 bond length
Ê
Ê
[1.346 (3) A] is slightly longer than reported [1.304 (4) A;
Bacelo et al., 1997]. However, the C1ÐC9 bond length
2
[1.443 (2) A], which is slightly shorter than a CarÐCsp single
Ê
2
[1.443 (2) A] is slightly shorter than a typical CarÐCsp single
Ê
bond (Wilson, 1992), suggesting extensive conjugation
between the ꢀ-electron system of the benzo[b]thiophene
system and the central double bond.
bond (Wilson, 1992), suggesting extensive conjugation
between the ꢀ-electron system of the benzo[b]thiophene
system and the central double bond.
The observed OÐC bond lengths are in agreement with
values found for the aromatic methoxy group. There is an
asymmetry of the exocyclic angles at atoms C13 and C15
[O1ÐC13ÐC12/C14 = 124.09 (16)/115.20 (15)ꢀ and O3Ð
C15ÐC16/C14 = 124.20 (16)/115.42 (15)ꢀ]. This is caused by
the tendency of the methoxy group to be coplanar with the
benzene ring, owing to conjugation of the O1 and O3 lone
pairs with the benzene ring (Domiano et al., 1979). However,
The observed OÐC bond lengths are in agreement with
values found for anisoles. There is an asymmetry of the
exocyclic angles at C13 and C14 [O1ÐC13ÐC12/O1ÐC13Ð
C14 = 124.98 (18)/115.58 (17)ꢀ and O2ÐC14ÐC15/O2Ð
C14ÐC13 = 124.73 (19)/115.23 (18)ꢀ]. This is caused by the
tendency of the methoxy group to be coplanar with the
benzene ring, owing to conjugation of the O1 and O2 lone
pairs with the benzene ring (Domiano et al., 1979).
the exocyclic angles [C15ÐC14ÐO2/C13ÐC14ÐO2
=
120.21 (16)/120.61 (16)ꢀ] at atom C14 are symmetric because
of the in¯uence of the adjacent methoxy groups; these force
the OÐC bond of the central methoxy group out of the plane
of the aromatic ring at an angle that is approximately
perpendicular to the plane of the aromatic ring, affording an
almost symmetrical structure. This is contrary to what is
observed with a single methoxy substituent at this position on
the aromatic ring (Sonar et al., 2006), where the OÐC bond of
the methoxy group is coplanar with the aromatic ring,
resulting in asymmetry in the aromatic ring and a consequent
difference in the exocyclic angles adjacent to the methoxy
group.
Fig. 2 shows an ellipsoid plot of (II), and selected geometric
parameters are presented in Table 2. The ole®nic bond
connecting the 3,4-dimethoxyphenyl and benzo[b]thiophene
ring systems in compound (II) has Z geometry. The bond
angles around the Csp2 atoms are distorted from the standard
value (120ꢀ). The C11ÐC10ÐC17, C10 C9ÐC1, and C9Ð
C10ÐC11 bond angles [116.69 (18), 129.9 (2), and 125.2 (2)ꢀ
respectively] are distorted owing to steric hindrance of the
double bond linking the two ring systems. The plane of the 3,4-
There are no signi®cant intermolecular hydrogen-bonding
interactions in the packing of (I) and (II). The packing is
essentially stabilized via van der Waals forces.
Experimental
The title compounds were prepared according to the previously
reported procedure of Sonar et al. (2004). Recrystallization from
ethyl acetate afforded yellow needles of (I), which were suitable for
X-ray analysis; compound (II) was crystallized from a mixture of
ethyl acetate and chloroform by slow evaporation over a period of
1
one week affording pale-yellow crystals. For (I): H NMR (DMSO-
d6): ꢁ 3.72 (s, 3H), 3.88 (s, 6H), 7.04 (s, 2H), 7.43±7.52 (m, 2H), 7.99
(dd, 1H), 8.03 (s, 1H), 8.09 (dd, 1H), 8.40 (s, 1H); 13C NMR (DMSO-
d6): ꢁ 56.12, 60.18, 103.25, 108.75, 117.66, 122.67, 124.69, 125.18,
126.70, 128.67, 131.48, 135.52, 137.30, 138.01, 138.42, 140.17, 153.11.
For (II): 1H NMR (DMSO-d6): ꢁ 3.76 (s, 3H), 3.85 (s, 3H), 7.02±7.13
(m, 3H), 7.33±7.39 (sextet, 2H), 7.82±7.89 (m, 3H), 8.01 (s, 1H); 13C
NMR (DMSO-d6): ꢁ 55.53, 55.62, 110.87, 112.16, 119.97, 121.84,
122.31, 123.43, 124.48, 124.86, 126.52, 132.27, 136.55, 137.28, 138.01,
140.85, 149.02, 150.00.
Compound (I)
Crystal data
3
Ê
C20H17NO3S
Mr = 351.41
V = 1695.90 (5) A
Z = 4
Monoclinic, P21=c
Mo Kꢃ radiation
ꢄ = 0.21 mm
T = 90.0 (2) K
0.40 Â 0.15 Â 0.15 mm
1
Ê
a = 7.4136 (1) A
b = 23.4782 (3) A
Ê
Ê
c = 10.3932 (2) A
ꢂ = 110.3689 (6)ꢀ
Data collection
Nonius KappaCCD diffractometer
Absorption correction: multi-scan
(SCALEPACK; Otwinowski &
Minor, 1997)
7649 measured re¯ections
3894 independent re¯ections
2800 re¯ections with I > 2ꢅ(I)
Rint = 0.037
Tmin = 0.921, Tmax = 0.969
Re®nement
R[F2 > 2ꢅ(F2)] = 0.045
wR(F2) = 0.127
S = 1.07
229 parameters
H-atom parameters constrained
Figure 2
A view of the asymmetric unit of (II), with displacement ellipsoids drawn
at the 50% probability level and H atoms shown as small spheres of
arbitrary radii.
3
Ê
Áꢆmax = 0.65 e A
3
Ê
0.29 e A
3894 re¯ections
Áꢆmin
=
ꢁ
o744 Sonar et al. C20H17NO3S and C19H15NO2S
Acta Cryst. (2007). C63, o743±o745

organic compounds
Table 1
Selected geometric parameters (A, ) for (I).
Table 2
Selected geometric parameters (A, ) for (II).
ꢀ
ꢀ
Ê
Ê
C1ÐS1
C8ÐS1
C10ÐC17
C10ÐC11
C14ÐO2
1.7519 (18)
1.7328 (19)
1.437 (2)
1.480 (2)
1.376 (2)
C15ÐO3
C17ÐN1
C19ÐO2
C20ÐO3
1.368 (2)
1.149 (2)
1.426 (2)
1.431 (2)
S1ÐC2
S1ÐC1
C10ÐC17
C10ÐC11
1.737 (2)
1.756 (2)
1.441 (3)
1.490 (3)
C14ÐO2
C17ÐN1
O2ÐC19
1.366 (2)
1.153 (3)
1.432 (2)
C2ÐS1ÐC1
C9ÐC10ÐC17
N1ÐC17ÐC10
91.18 (10)
118.05 (19)
179.2 (2)
C13ÐO1ÐC18
C14ÐO2ÐC19
116.63 (15)
117.29 (16)
C9ÐC10ÐC17
O2ÐC14ÐC13
N1ÐC17ÐC10
119.79 (16)
120.61 (16)
177.9 (2)
C14ÐO2ÐC19
C15ÐO3ÐC20
C8ÐS1ÐC1
113.83 (14)
116.82 (14)
91.12 (9)
C8ÐC1ÐC9ÐC10
S1ÐC1ÐC9ÐC10
176.5 (2)
3.3 (3)
C1ÐC9ÐC10ÐC17
C1ÐC9ÐC10ÐC11
178.7 (2)
0.5 (4)
C2ÐC1ÐC9ÐC10
S1ÐC1ÐC9ÐC10
175.25 (18)
2.3 (3)
C1ÐC9ÐC10ÐC17
C1ÐC9ÐC10ÐC11
2.2 (3)
174.59 (18)
SHELXS97 (Sheldrick, 1997); program(s) used to re®ne structure:
SHELXL97 (Sheldrick, 1997); molecular graphics: XP in SHELXTL/
PC (Sheldrick, 1995); software used to prepare material for publi-
cation: SHELXL97 and local procedures.
Compound (II)
Crystal data
3
Ê
V = 1541.25 (6) A
C19H15NO2S
Mr = 321.38
Z = 4
Mo Kꢃ radiation
Monoclinic, P21=n
This investigation was supported by the National Institute
of Alcohol Abuse and Alcoholism (grant No. AA12600).
1
Ê
a = 9.2958 (2) A
ꢄ = 0.22 mm
T = 90.0 (2) K
Ê
b = 6.0830 (1) A
Ê
c = 27.2763 (7) A
0.27 Â 0.22 Â 0.06 mm
ꢂ = 92.1871 (10)ꢀ
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: HJ3056). Services for accessing these data are
described at the back of the journal.
Data collection
Nonius KappaCCD diffractometer
Absorption correction: multi-scan
(SCALEPACK; Otwinowski &
Minor, 1997)
6626 measured re¯ections
3528 independent re¯ections
2288 re¯ections with I > 2ꢅ(I)
Rint = 0.052
References
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Tmin = 0.943, Tmax = 0.987
Re®nement
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R[F2 > 2ꢅ(F2)] = 0.047
wR(F2) = 0.127
S = 1.00
210 parameters
H-atom parameters constrained
3
Ê
Áꢆmax = 0.42 e A
3
Ê
0.31 e A
3528 re¯ections
Áꢆmin
=
H atoms were found in difference Fourier maps and subsequently
placed in idealized positions, with constrained CÐH distances of
Ê
Ê
0.98 A for methyl H atoms and 0.95 A for all other H atoms. Uiso(H)
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and SCALEPACK (Otwinowski & Minor, 1997) for (II); data
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ꢁ
Acta Cryst. (2007). C63, o743±o745
Sonar et al. C20H17NO3S and C19H15NO2S o745