Synthesis and x-ray crystal structure of 1- and 2-cinnamoyaloxy acetonaphthones

Article abstract of DOI:10.1007/s10870-010-9923-3

The synthesis of titled compounds were achieved in one step using hydroxyl naphthones and substituted cinnamic acids in the presence of a catalytic amount of phosphorus oxychloride. X-ray crystal studies were undertaken for three compounds and the results are presented. Compounds 1 (C₂₂H ₁₅F₃O₃) and 3 (C₂₁H ₁₅BrO₃) formed a monoclinic crystals while compound 2 (C₂₂H₁₅F₃O₃) formed a triclinic crystals. The observed space group of these compounds is P2₁/c and PI respectively. The 2-substituted compounds showed identical space group and showed a perpendicular arrangements of each of the substituents to the plane of the naphthyl ring. On the contrary, the 1-substituted cinnamoyal compound showed an orthogonal arrangement to naphthyl ring but the acetyl group was almost planar relative to the naphthyl moiety. The characterization of the structures of the compounds was also accomplished using high-resolution NMR spectroscopic techniques. Springer Science+Business Media, LLC 2010.

Full text of DOI:10.1007/s10870-010-9923-3

J Chem Crystallogr (2011) 41:563–569
DOI 10.1007/s10870-010-9923-3
ORIGINAL PAPER
Synthesis and X-Ray Crystal Structure
of 1- and 2-Cinnamoyaloxy Acetonaphthones
•
T. K. Venkatachalam Gregory K. Pierens
•
•
Paul V. Bernhardt D. C. Reutens
Received: 30 July 2010 / Accepted: 28 November 2010 / Published online: 16 December 2010
Ó Springer Science+Business Media, LLC 2010
Abstract The synthesis of titled compounds were achieved
in one step using hydroxyl naphthones and substituted
cinnamic acids in the presence of a catalytic amount of
phosphorus oxychloride. X-ray crystal studies were under-
taken for three compounds and the results are presented.
Compounds 1 (C22H15F3O3) and 3 (C21H15BrO3) formed a
monoclinic crystals while compound 2 (C22H15F3O3) formed
a triclinic crystals. The observed space group of these com-
for preparation of chromones [1, 2]. The protective group
on the hydroxyl functionality of these 2-hydroxy aceto-
naphthones is essential for further functionalization of the
methyl group associated with the acetyl moiety [3–7]. The
original procedure for the preparation of cinnamoyaloxy
acetonpahthones involves the condensation of the hydroxy
acetonaphthone with substituted cinnamic acids using a
mineral acid as catalyst [1, 2]. Using this traditional
method, Pallaniandavar et al. [8] have prepared certain
20-chalcones and utilized them for preparation of cobalt,
nickel and copper complexes. The authors have also
reported that these chalcones formed square-planar com-
plexes, which was in contrast to the metal chelates obtained
from b-diketones, salicylaldehyde and hydroxy ketones.
Graddon et al. [9] also reported the synthesis and charac-
terization of cobalt complexes of o-hydroxy aryl aldehydes
and ketones and found that these complexes showed an
octahedral, cobalt (II) configuration in the complexes.
Diketones were able to form various metal complexes but
not with copper. Subsequently, Athappan et al. [10, 11]
introduced extensive conjugation in the structure of the
diketones that enhanced their in-plane binding capacity and
the ability to complex copper. To date, the structural
characterization of the ligands has not been reported. We
describe the structural characterization of the ester deriv-
atives including their X-ray crystal structure.
ꢀ
pounds is P21/c and P1 respectively. The 2-substituted
compounds showed identical space group and showed a
perpendicular arrangements of each of the substituents to the
plane of the naphthyl ring. On the contrary, the 1-substituted
cinnamoyal compound showed an orthogonal arrangement to
naphthyl ring but the acetyl group was almost planar relative
to the naphthyl moiety. The characterization of the structures
of the compounds was also accomplished using high-reso-
lution NMR spectroscopic techniques.
Keywords Cinnamoyaloxy ꢀ Acetonaphthones ꢀ NMR ꢀ
X-ray ꢀ Crystallography
Introduction
Cinnamoyaloxy acetonaphthones are building blocks for
the synthesis of b-diketones, which are versatile synthons
T. K. Venkatachalam ꢀ G. K. Pierens (&) ꢀ D. C. Reutens
Centre for Advanced Imaging, The University of Queensland,
St. Lucia, Brisbane 4072, Australia
Results and discussion
e-mail: g.pierens@uq.edu.au
The synthesis of cinnamoyaloxy acetonaphthone was
achieved following Scheme 1. In brief, 1- and 2-hydroxy
substituted naphthone was condensed with substituted
cinnamic acid in pyridine in the presence of a catalytic
amount of phosphorus oxychloride to furnish the titled
T. K. Venkatachalam
e-mail: t.venkatachalam@uq.edu.au
P. V. Bernhardt
School of Chemistry, The University of Queensland, St. Lucia,
Brisbane 4072, Australia
123

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J Chem Crystallogr (2011) 41:563–569
Scheme 1 Synthetic scheme
showing the preparation of
cinnamoyaloxy naphthones
COMe
OH
COMe
O
Pyridine/RT
COOH
CF3
+
Cat POCl3
8-10h
O
(1)
CF3
O
O
OH
COMe
Pyridine/RT
COMe
CF3
COOH
+
Cat POCl3
8-10h
(2)
CF3
Br
COMe
COMe
O
OH
COOH
Pyridine/RT
+
Br
Cat POCl3
8-10h
O
(3)
compounds as crystalline solids in good yield. The com-
pounds were further purified by recrystallization from
methanol. Both 1-substituted and 2-substituted acetonaph-
thone derivatives were prepared using appropriate hydroxyl
acetonaphthones. Cinnamic acids containing electron
withdrawing and donating groups were used for the syn-
thesis of various cinnamoyal-substituted compounds. The
structural characterization of a variety of these compounds
using high-resolution NMR techniques has been reported
elsewhere [12]. In the present study, we focused on the
X-ray crystal structure characteristics of three different
ester derivatives.
considerably affected the chemical shifts of its protons,
consistent with the notion that electron-donating and
withdrawing groups should show an opposite trend [12].
Figure 1 shows the X-ray crystal structure of 2-(2-tri-
fluoromethyl cinnamoyal)-oxo-1-naphthone (compound 1).
The crystal data are presented in Table 1. Compound 1 was
a monoclinic crystal with a space group of P21/c. The
selected bond lengths and angles observed for this com-
pound are presented in Table 2. The bond lengths and
angles were as expected and no close intermolecular
contacts were apparent. In compound 1, the conformation
of the molecule indicates that the naphthyl and cinna-
moyal groups approaching an orthogonal disposition
(C3–C2–O2–C13 angle 73.7(2)). Similarly the acetyl
group is rotated out of the plane of the naphthyl group
The compounds were characterized using routine ana-
lytical techniques and the structural assignments were
made using COSY, TOCSY and HMBC NMR experi-
ments. The UV spectra of compound 1 showed main
absorption peak at 286 with a shoulder at 333 nm while
compound 2 showed the main absorption peak at 283 with
a shoulder at 283 nm. Compound 3 showed a higher
wavelength of absorption at 303 nm with a shoulder at
330 nm. These absorption peaks are arising due to the
presence of conjugated aromatic moiety in the molecule.
The infrared spectra showed strong absorption at
1712 cm-1 as well as at 1654 cm-1 indicative of the
presence of a C=O group. All other infrared spectral
stretching frequencies were consistent with the structure of
the compounds. The structural confirmation of each of the
C20
C19
C12
C21
C18
O1
C16
C11
C14
C17
C22
C15
O2
F3
C9
C1
C13
C2
C10
C5
F1
F2
C8
C7
C3
O3
C4
C6
1
compounds was achieved using H/13C, COSY, TOCSY,
HSQC and HMBC methods. However, the electron with-
drawing groups in the phenyl ring of the molecule
Fig. 1 X-ray crystal structure of 2-(2-trifluoromethyl cinnamoyal)-
oxo-1-naphthone (compound 1) (30% ellipsoid probability)
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565
Table 1 Crystal structure data for the compounds 1–3
Details
Compound 1
Compound 2
Compound 3
Empirical formula
MW
C22H15F3O3
384.3
C22H15F3O3
384.3
C21H15BrO3
395.24
Temperature
Wavelength
293 K
293 K
293(2) K
˚
0.71073 A
˚
0.71073 A
˚
0.71073 A
Crystal system
Space group
Unit cell dimensions
Monoclinic
P21/c
Triclinic
Monoclinic
P21/c
ꢀ
P1
˚
a = 9.5217(4) A
˚
a = 8.1872(7) A
˚
a = 15.527(1) A
˚
b = 14.1360(5) A
˚
b = 10.1608(9) A
˚
b = 14.576(1) A
˚
c = 14.1140(6) A
˚
˚
c = 6.9958(5) A
c = 12.5393(14) A
a = 67.243(9)°
b = 77.077(9)°
c = 67.986 (8)°
a = 90°
a = 90°
b = 103.016(5)°
c = 90°
b = 95.783(7)°
c = 90°
3
3
˚
3
˚
˚
1850.92(13) A
Volume
888.01(15) A
1778.2(2) A
Z
4
2
4
Density
1.379 g/cm3
0.111 mm-1
0.4 9 0.4 9 0.3 mm3
1.437 g/cm3
0.116 mm-1
0.6 9 0.6 9 0.3 mm3
1.476 g/cm3
2.328 mm-1
0.2 9 0.2 9 0.1 mm3
3.03–25.00°
6532
Absorption coefficient
Crystal size
Theta range
2.88–25°
6768
3.08–24.99°
5473
Reflections collected
Independent reflections
Completeness to h = 25°
Final R indices [I [ 2r(I)]
R indices (all data)
Largest diff peak and hole
3253 [R(int) = 0.0214]
99.90%
3130 [R(int) = 0.0227]
99.80%
3133 [R(int) = 0.0455]
99.80%
R1 = 0.0399, wR2 = 0.0924
R1 = 0.0801, wR2 = 0.1005
0.181 and
R1 = 0.0385, wR2 = 0.0743
R1 = 0.0864, wR2 = 0.0821
0.115 and
R1 = 0.0334, wR2 = 0.0395
R1 = 0.1338, wR2 = 0.0461
0.246 and
-3
-3
-3
˚
-0.131 e A
˚
-0.144 e A
˚
-0.250 e A
Data/restrains/parameters
Goodness-of-fit on F2
CCDC number
3253/0/254
0.86
3130/0/253
0.795
3133/0/226
0.606
785032
785031
785030
(C2–C1–C11–C12 79.6(2)°). Additionally we observed the
cinnamoyal moiety is showing planarity due to extended
conjugation in the molecule, which allows a stable 3D
arrangement. The COMe group is also forced to remain in
orthogonal position. Furthermore, a trans configuration is
seen between the cinnamoyal and the COMe group of the
molecule. This type of crystallographic structure of com-
pound 1 is due to the steric effects of the groups in the
1- and 2-positions on the naphthalene ring system. The
E-isomer of the cinnamic acid parent is retained, which is
significant conformational changes. Most notably the
acetyl group is essentially coplanar with the naphthalene
ring system (C3–C2–C11–C12 9.9(3)°). The cinnamoyal
ester group is again twisted close to orthogonal relative to
the naphthyl moiety (C2–C1–O2–C13 77.9(2)°; see
Table 3). The co planarity of the acetyl group is enabled by
the less crowded 2-(b) position while in compound 1,
interactions with the peri-proton on C9, force its rotation
out of the plane of the naphthyl group. Additionally we
observed that the cinnamoyal group in the molecule adopts
a planar configuration and the group is perpendicular to the
naphthyl group due to steric hindrance and the presence of
extended conjugation in the molecule. The remaining bond
lengths and angles are consistent with the assigned struc-
ture of the molecule.
1
consistent with the H NMR results (J = 15 Hz) [12].
Compound 2 [1-(2-trifluoromethyl-cinnamoyal oxo)-
2-naphthone] formed a triclinic crystal with a space group
of P1. The crystal structure of compound 2 (isomeric with
1) is shown in Fig. 2. Additionally Table 3 provides the
selected bond lengths and angles for various atoms in the
molecule. We conclude that the bond lengths and angles
are consistent with the expected trend for compounds
possessing similar structural features. However, inter-
change of the acetyl and cinnamoyal ester group’s leads to
Compound 3 [2-(4-bromocinnamoyal)-oxo-1-naphth-
one] formed a monoclinic crystal with a space group of
P21/c (Fig. 3). The selected bond lengths and angles are
shown in Table 4. All bond lengths and angles are con-
sistent with the structure of the molecule. Unlike the ortho
123

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J Chem Crystallogr (2011) 41:563–569
Table 2 Selected bond lengths and angles for compound 1
Table 3 Selected bond lengths and angles for compound 2
˚
Bond lengths (A)
˚
Bond lengths (A)
Bond designation
Bond designation
C(1)–C(2)
C(1)–C(10)
C(1)–C(11)
C(2)–C(3)
C(2)–O(2)
C(3)–C(4)
C(4)–C(5)
C(5)–C(10)
1.353(2)
1.422(2)
1.503(3)
1.399(3)
1.412(2)
1.352(3)
1.410(3)
1.414(2)
C(1)–C(2)
C(1)–O(2)
C(1)–C(10)
C(2)–C(3)
C(2)–C(11)
C(3)–C(4)
C(4)–C(5)
C(5)–C(10)
1.370(3)
1.399(2)
1.415(2)
1.416(2)
1.499(3)
1.360(3)
1.403(3)
1.419(3)
Angle designation
Bond angles (°)
Bond designation
Bond angles (°)
C(2)–C(1)–C(10)
C(2)–C(1)–C(11)
C(10)–C(1)–C(11)
C(1)–C(2)–C(3)
C(1)–C(2)–O(2)
C(3)–C(2)–O(2)
C(4)–C(3)–C(2)
C(4)–C(5)–C(10)
118.89(17)
120.29(18)
120.76(17)
122.69(18)
118.20(18)
119.07(18)
119.11(19)
118.88(18)
C(2)–C(1)–O(2)
C(2)–C(1)–C(10)
O(2)–C(1)–C(10)
C(1)–C(2)–C(3)
C(1)–C(2)–C(11)
C(3)–C(2)–C(11)
C(4)–C(3)–C(2)
C(4)–C(5)–C(10)
121.05(17)
123.42(19)
115.11(19)
117.11(18)
122.17(19)
120.7(2)
121.7(2)
119.06(19)
Table 4 Selected bond lengths and angles for compound 3
C7
C6
C8
˚
Bond lengths (A)
Bond designation
C9
C(1)–C(2)
C(1)–C(10)
C(1)–C(11)
C(2)–C(3)
C(3)–C(4)
C(4)–C(5)
C(5)–C(6)
C(5)–C(10)
1.356(4)
1.411(4)
1.508(4)
1.405(4)
1.352(4)
1.415(4)
1.407(4)
1.416(4)
C5
C4
C10
C18
O2
C1
C19
C17
C13
C16
F1
C15
C3
C2
C14
C21
C22
C20
O3
C11
O1
F3
F2
C12
Bond designation
Bond angles (°)
Fig. 2 X-ray crystal structure of 1-(2-trifluoromethyl-cinnamoyal
oxo)-2-naphthone (compound 2) (30% ellipsoid probability)
C(2)–C(1)–C(10)
C(2)–C(1)–C(11)
C(10)–C(1)–C(11)
C(1)–C(2)–O(2)
C(1)–C(2)–C(3)
C(3)–C(2)–C(11)
O(2)–C(2)–C(3)
C(4)–C(3)–C(2)
119.5(3)
119.7(3)
120.8(3)
118.8(3)
122.1(3)
120.7(2)
118.9(3)
119.2(3)
CF3 groups in compounds 1 and 2, the para bromo sub-
stituent in compound 3, has no significant structural influ-
ence on the conformation of the phenyl group. As in
compound 1, the 1-acetyl group is twisted out of the plane
of the naphthalene (C2–C1–C11–C12 87.9(4)°). The cin-
namoyal ester is orthogonal to the naphthyl ring system
(C3–C2–O2–C13 76.4(4)) (Table 4). Additionally we
observed that the phenyl group of the cinnamoyal moiety is
out of plane by approximately 15°. A trans configuration
for the two protons on the cinnamoyal group was obtained
in the crystal structure consistent with the results obtained
by NMR [12].
torsion angles between compounds 1 and 3 was compared
since both these compounds posses the COMe group in
position 1 of the naphthyl moiety in their structures. The
observed torsion angle for C(2)–C(1)–C(11)–C(12) was
-79.60° and 87.92° for compounds 1 and 3 respectively.
The observed O(2)–C(2)–C(11)–O(1) torsion angle values
were 87.07° and -71.60° and the C(3)–C(2)–O(2)–C(13)
Table 5 shows the important torsion angles observed for
all three compounds described in the present study. The
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J Chem Crystallogr (2011) 41:563–569
567
C6
C7
C4
C5
C3
C8
C10
C9
C2
C1
O3
O2
C13
C14
C11
O1
C12
C15
C16
C18
C21
C20
C17
C19
Br1
Fig. 3 X-ray crystal structure of 2-(4-bromocinnamoyal)-oxo-
1-naphthone (compound 3) (30% ellipsoid probability)
angle did not differ significantly between these two com-
pounds. In the case of compound 2 we could only compare
the torsion angle for C(14)–C(15)–C(16)–C(21) with that
of compound 3 and the values were 171.6° and 165.7°.
We next compared the observed bond lengths for similar
atoms in the crystal structure of each compound (Table 5).
The C15–C16 bond length is longer in compound 2 than in
compounds 1 and 3. The C14–C15 bond length is shorter
in compound 2 than in compounds 1 and 3. There was
no significant difference between the compounds in the
C13–C14 bond length. The presence of CF3 or bromo
groups in the phenyl moiety affects C15–C16 bond length.
The shorter bond length observed for the CF3 substituted
compound 2 can be explained by the high electron with-
drawing nature of this group and the steric influence due to
its size.
Fig. 4 Cell packing diagram of compound 1 (viewed down the a axis,
i.e. the b/c plane)
factor can mean a good model or over-fit refinement [13,
14]. The over fitting can occur due to two reasons, one is not
an excess data much greater than the number of model
parameters or worse if given too much freedom to model.
This is either due to insufficient weight on standard ste-
reochemistry or inappropriate model parameters. However
we emphasize that several other authors have observed such
a low goodness-of-fit values in the range of 0.60–0.61 [15].
The packing diagram for compound 1 is shown in
Fig. 4. The packing is viewed down ‘a’ axis looking down
onto the b/c plane. The molecules showed a tilted
arrangement between each of the molecules in which the
phenyl groups are slightly tilted each other in the crystal
packing. The C17 carbon is overlaid in a head to tail
fashion with CF3 groups displayed in opposite direction.
The distance between the phenyl rings of two molecules in
In comparing the goodness-of-fit on F2 (Table 1) for all
the compounds used in the present study, compounds 1 and
2 showed the following values: 0.86 and 0.795 while
compound 3 showed a lower value of 0.606. The ‘low’ R
Table 5 Important torsion
angles observed for the
compounds
˚
Bond length (A)
Compound
1
Bond designation
Torsion angle (°)
Bond designation
C(2)–C(1)–C(11)–C(12)
O(2)–C(2)–C(11)–O(1)
C(3)–C(2)–O(2)–C(13)
C(14)–C(15)–C(16)–(17)
C(3)–C(2)–C(11)–C(12)
O(2)–C(1)–C(11)–O(1)
C(10)–C(1)–O(2)–C(13)
C(14)–C(15)–C(16)–(21)
C(2)–C(1)–C(11)–C(12)
O(2)–C(2)–C(11)–O(1)
C(3)–C(2)–O(2)–C(13)
C(14)–C(15)–C(16)–(21)
-79.6
87.07
73.65
173.57
9.86
C(15)–C(16)
C(14)–C(15)
C(13)–C(14)
1.468
1.311
1.461
2
3
C(15)–C(16)
C(14)–C(15)
C(13)–C(14)
1.473
1.299
1.463
15.55
109.2
171.6
87.92
-71.6
76.37
165.67
C(15)–C(16)
C(14)–C(15)
C(13)–C(14)
1.445
1.323
1.458
123

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J Chem Crystallogr (2011) 41:563–569
In general, the packing arrangement of 1 and 2 showed
marked difference perhaps due to the interchange of sub-
stitutions in both the 1 and 2 positions of the naphthyl ring.
In compound 1 the cinnamoyal oxy group was opposite to
that of the keto group in the structure of the molecule.
Compound 2 showed a zig-zag crystal packing arrange-
ment while compound 3 showed a tight packing of the
crystals, similar to that observed in compound 2. The
crystal packing did not show any inter-molecular hydrogen
bonds, as expected from the absence of free polar groups in
the structures.
In summary, we have synthesized cinnamoyaloxy-sub-
stituted acetonaphthones and examined their structures
using various analytical techniques. Substitution of the
phenyl ring in the cinnamoyal moiety in the structure
showed a marginal change in the chemical shifts in
accordance with the electron donating/withdrawing group’s
character. The double bond in the molecule showed a
coupling constant value of 15 Hz implying an E configu-
ration for the olefinic group. X-ray crystal structures of the
compounds also confirmed this configuration. The crystal
structures revealed that the conformations of compounds 1
and 2 are quite different, driven by rotation of the naphthyl
substituents to minimize non-bonded interactions.
Fig. 5 Cell packing diagram of compound 2 (viewed down the b
axis, i.e. the a/c plane)
Experimental
Fig. 6 Cell packing diagram of compound 3 (viewed down the a axis,
i.e. the b/c plane)
All the chemicals were obtained from Aldrich Sigma and
were used without further purification. NMR spectra were
recorded in dimethyl sulfoxide and the chemical shifts are
reported relative to residual DMSO at 2.54 ppm. The NMR
data was acquired on a Bruker 900 MHz NMR spectrom-
eter equipped with a cryoprobe. The proton spectra where
acquired with a sweep width of 18 ppm centred at 7 ppm.
The carbon spectra were acquired with a sweep width of
220 ppm centered at 110 ppm. The DQCOSY and TOCSY
experiments were also acquired with a sweep width of
18 ppm using a 90° pulse of 9 ls with 256 and 350
increments respectively. The raw data was usually multi-
plied by an exponential or shifted sine squared function
before performing the Fourier transform [12]. UV/vis
spectra were obtained from a Lambda UV spectrometer
using either methanol or chloroform as solvent. Infra Red
spectra were taken as KBr disc on a Lambda FTIR
spectrometer.
˚
the packing diagram was 3.628 A. The angle between the
phenyl and the naphthyl ring was 142.08°.
In compound 2, the packing diagram (Fig. 5) displays
the arrangement in the crystal viewed down the ‘b’ axis
looking down onto the a/c plane. The molecules showed a
tessellated arrangement. The naphthyl rings showed a tes-
˚
sellated pattern with a distance of 3.480 A, while the CF3
group stood itself in the structure. Furthermore the angle
between the phenyl group relative to the naphthyl group
was 124°.
We examined the crystal packing arrangement of the
compounds and Fig. 6 shows the crystal packing arrange-
ment of compound 3. The packing diagram shows the
arrangement viewed down the ‘a’ axis, looking down onto
the b/c plane. There was no pi- stacking arrangement in the
crystal and the distances between each of the representative
atoms are as follows: the distances between two bromine
˚
atom of each molecule was 4.603 A and the distances
˚
between the phenyl rings are 3.687 and 4.293 A which
Crystallographic data (MoKa, 2hmax = 50°) were col-
lected on an Oxford Diffraction Gemini S Ultra CCD dif-
fractometer at 293 K. Data reduction and empirical
absorption corrections were carried out with the CrysAlis
Pro program (Oxford Diffraction vers. 171.33.42). The
structure was solved by direct methods with SHELXS86
and refined with SHELXL97 [16]. The thermal ellipsoid
demonstrates that the rings are not stacked one over the
other. The naphthyl moiety was perpendicular each other.
In other words, they face to edge of each of the molecule in
the crystal-packing diagram. The CO–CO distances
˚
between two molecules were 3.506 A.
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J Chem Crystallogr (2011) 41:563–569
569
7. Mehrota RC, Bohra R, Gaur DP (1978) Metal diketonates and
allied derivatives. Academic press, New York
diagrams were generated with ORTEP3 [17]. All crystal-
lographic calculations were carried out within the WinGX
graphical user interface [18]. The crystal data are presented
in Table 1 including the CCDC numbers.
8. Palaniandavar M, Natarajan C (1980) Aust J Chem 33:737
9. Graddon DP, Mockler GM (1968) Aust J Chem 21:1487
10. Athappan P, Rajagopal G (1997) Transit Met Chem 22:84
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12. Venkatachalam TK, Pierens GK, Reutens DC (2010) Magn
Reson Chem (in press)
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