Synthesis, characterization, and crystal structures of α, α'-bis(substituted-benzylidene)cycloalkanone derivatives by nano-TiO2/HOAc

Article abstract of DOI:10.1007/s11164-015-2039-9

A new and economical synthesis of α, α'-bis(substituted-benzylidene)cycloalkanones has been achieved by the reaction of cycloalkanones with different aromatic aldehydes using nano-TiO₂/acetic acid as a catalyst in ethanol under reflux conditions with excellent yields. Five new products and three new single crystal structures are reported.

Full text of DOI:10.1007/s11164-015-2039-9

Res Chem Intermed
DOI 10.1007/s11164-015-2039-9
Synthesis, characterization, and crystal structures of a,
0
a -bis(substituted-benzylidene)cycloalkanone
derivatives by nano-TiO /HOAc
2
1
1
1
•
Elham Tabrizian
Salman Rahmani
•
Ali Amoozadeh
1
2
•
Mehdi Salehi
•
Maciej Kubicki
Received: 13 February 2015 / Accepted: 30 March 2015
Springer Science+Business Media Dordrecht 2015
ꢀ
0
Abstract A new and economical synthesis of a, a -bis(substituted-benzylidene)-
cycloalkanones has been achieved by the reaction of cycloalkanones with different
aromatic aldehydes using nano-TiO /acetic acid as a catalyst in ethanol under reflux
2
conditions with excellent yields. Five new products and three new single crystal
structures are reported.
0
Keywords a, a -bis(substituted-benzylidene)cycloalkanones ꢀ Nano-TiO ꢀ
2
Crystal structure
Introduction
In recent years, transition metal nanoparticles are used as efficient catalysts for
various synthetic organic transformations due to their high surface area-to-volume
ratio and coordination sites, which are mainly responsible for their catalytic activity
[1, 2]. Titanium dioxide nanoparticles (nano-TiO ) are certainly among the most
2
interesting metal oxides that enable organic reactions to occur. It has been proved
that nano-TiO is an efficient catalyst for the synthesis of quinoxalines [3], b-
2
acetamido ketones [4], 1,8-dioxo-octahydroxanthenes [5], dibenzo[a,j]xanthenes
[6], and polyhydroquinolines [7]. Non-toxicity, easy availability, high activity,
strong oxidizing power, reusability, and long-term stability are the main advantages
of nano-TiO [3, 8].
2
0
The a, a -bis(substituted-benzylidene)cycloalkanones, as a, b-unsaturated car-
bonyl compounds are generally synthesized by Claisen–Schmidt condensation. This
&
Ali Amoozadeh
aamozadeh@semnan.ac.ir
1
2
Department of Chemistry, Semnan University, Semnan, 35131-19111, Iran
Department of Chemistry, Adam Mickiewicz University, Umultowska 89b, 61-614 Poznan,
Poland
123

E. Tabrizian et al.
class of compound is known to have a broad spectrum of biological properties such
as antimicrobial [9], anti-inflammatory [10], antimutagenic [11], antitumor [11], and
antipyretic [12] activities. Moreover, they can be used in optics [13], rocket
engineering [14], photolithography [15], and liquid crystalline polymers [16].
0
Generally, the synthetic approach to a, a -bis(substituted-benzylidene)cycloalka-
nones involves Claisen–Schmidt condensation of cyclic ketones with two
equivalents of aromatic aldehyde that is catalyzed by a strong base or an acid.
Various catalysts, such as Lewis or Brønsted acids [17–19] or bases [20, 21],
heterogeneous catalysts [22, 23], and complexes of metal ions [24, 25] under
heating condition or sonication [26] or microwave irradiation [27, 28], have been
reported for their synthesis in the literature which afford variable product yields.
A wide variety of application and considerable interest for crystallographic
0
investigations on the a, a -bis(substituted-benzylidene)cycloalkanones encouraged
us to report new derivatives and also novel single crystal structures in order to
determine the geometry of the cyclohexanone moiety. Herein, we have reported a
new method for their synthesis by using nano-TiO /acetic acid as catalyst in ethanol
2
under reflux conditions (Scheme 1). It is notable that acetic acid is beneficial to the
catalytic activity of nano-TiO , which increases it significantly.
2
Results and discussion
Initially, nano-TiO powder is easily prepared according to the reported procedure
2
[
29]. Figure 1a shows the XRD patterns of prepared nano-TiO powder. As seen in
2
Fig. 1a, the following peak signals from (101), (103), (004), (112), (200), (105),
211), (204), (220), (215), and (224) planes confirm the formation of anatase crystal
phase mostly, which coincides with the JCPD 89-4921 standard. The size of the
(
nano-TiO powder was also determined by X-ray line width using the Scherrer
2
formula given as D = 0.9k/b cosh, where D is the average crystalline size, k is the
X-ray wavelength used, b is the angular line width at half maximum intensity, and h
0
is the Bragg s angle. The average size of the nano-TiO powder for 2h = 25.303ꢁ
2
was estimated to be around 21.88 nm. Transmission electron microscopy (TEM)
analysis was used for characterization of nano-TiO powder (Fig. 1b). The TEM
2
image reveals the spherical nano-TiO powder with an average size of 20–30 nm.
2
The FT-IR spectra of nano-TiO2 powder is shown in Fig. 2. The bending
vibrations of adsorbed water molecules and stretching vibrations of OH are around
-
620–1635 and 3350–3450 cm , respectively [30]. The broad intense band at 520
1
1
0
Scheme 1 New route for the synthesis of a, a -bis(substituted-benzylidene)cycloalkanone derivatives
1
23

Synthesis, characterization, and crystal structures of…
2 2
Fig. 1 a The X-ray diffraction patterns of the nano-TiO , b the TEM image of the nano-TiO
Fig. 2 The FT-IR spectra of the
nano-TiO powder
2
Fig. 3 TGA curve of the nano-
TiO powder
2
-
1
and 689 cm is due to Ti–O–Ti vibration, which is consistent with the reported IR
spectra for nano-TiO [30].
2
Thermo gravimetric analysis (TGA) of nano-TiO is shown in Fig. 3. The TGA
2
curve displays a weight loss (4 wt%) below 100 ꢁC which corresponds to the loss of
the physically adsorbed water. Also, there is a slight weight loss (1 wt%) between
123

E. Tabrizian et al.
1
Also, from the TGA, we understood that nano-TiO has a great thermal stability (up
00 and 800 ꢁC, which possibly corresponds to the dehydroxylation of nano-TiO2.
2
4
00 ꢁC) confirming that it can be safely used in organic reactions at temperatures in
the range of 80–150 ꢁC.
Considering the researches toward evaluating the catalytic activity of nano-TiO2
0
in chemical transformations, we have investigated the synthesis of a, a -
bis(substituted-benzylidene)cycloalkanones in the presence of nano-TiO2 under
heating conditions.
We have employed cyclohexanone (1 mmol) and benzaldehyde (2 mmol) as a
representative model reaction in the presence of 20 mol% of nano-TiO . To choose
2
the most appropriate condition in this condensation reaction and to understand the
influence of different variables in this reaction, several experiments were studied.
The results are summarized in Table 1.
As Table 1 shows, the best yield was obtained in refluxing ethanol (Table 1,
entry 6), while other selected temperatures and solvents did not provide good
condition for this reaction (Table 1, entries 1–5 and 7–9). It is notable that no
product formed within a reasonable time in the absence of catalyst (Table 1, entry
1
0), and the optimum amount of the catalyst was 20 mol%, which is enough to carry
out the reaction efficiently (Table 1, entry 6). Furthermore, the yield of the product
by using bulk TiO was not satisfactory in comparison to nano-TiO (Table 1, entry
2
2
13). The high efficiency of the nano-TiO may be due to its high surface area
2
compared with the bulk TiO2.
Considering the optimized reaction conditions (Table 1, entry 6), we have
investigated the generality of this method with different aldehydes and ketones to
0
prepare a series of a, a -bis(substituted-benzylidene)cycloalkanones (Table 2).
As shown in Table 2, the aldehydes bearing both electron-donating and electron-
withdrawing groups can be used in this reaction to afford desired products with high
yields. Moreover, in the published papers, most attention has been given to five- and
Table 1 Optimum conditions
0
a
Yield (%)
Entry
Catalyst (mol%)
Solvent
Temp. (ꢁC)
for the synthesis of a, a -
bis(benzylidene)cyclohexanone
1
2
3
4
5
6
7
8
9
Nano-TiO
Nano-TiO
Nano-TiO
Nano-TiO
Nano-TiO
Nano-TiO
Nano-TiO
Nano-TiO
Nano-TiO
Nano-TiO
2
2
2
2
2
2
2
2
2
2
(20)
(20)
(20)
(20)
(20)
(20)
(20)
(20)
(20)
(0)
–
R.T
40
60
80
100
80
80
80
80
80
80
80
80
0
0
–
–
35
70
60
93
10
0
–
–
EtOH
2
H O
PEG
CH CN
3
20
0
Reaction conditions:
1
0
EtOH
EtOH
EtOH
EtOH
cyclohexanone (1 mmol),
benzaldehyde (2 mmol), glacial
AcOH 20 drops, reaction time:
11
Nano-TiO (10)
2
65
90
45
1
1
2
3
Nano-TiO
2
(30)
(20)
6
h
Bulk-TiO
2
a
Isolated yields
1
23

Synthesis, characterization, and crystal structures of…
0
Table 2 Synthesis of a, a -bis(substituted-benzylidene)cycloalkanone derivatives under optimized
conditions (new compounds)
c
Entry Product
Time (h:min) Yield (%) M.P. (ꢁC)
Found
Reported
1
O
6:10
6:15
6:00
7:00
5:50
91
94
94
88
97
188–190 188–189 [17]
211–213 209–210 [17]
240–242 239–241 [17]
168–171 Not reported
155–156 160–161 [17]
3
a
2
O
H CO
3
3b
OCH3
CH3
3
4
5
O
H C
3
3c
a
NO2
O
NO2
Cl
3
d
Cl
O
3
e
6
7
O
5:30
5:20
97
94
227–229 230–231 [31]
235–236 237–239 [28]
Cl
F
3f
Cl
F
O
3
g
8
9
O
5:00
6:00
92
94
254–257 254–257 [28]
117–119 113–115 [17]
Br
Br
3h
O
3
i
1
1
1
0
1
2
O
6:40
6:15
7:30
90
92
85
160–162 159–161 [17]
167–169 163–165 [17]
156–158 155–157 [17]
H CO
3
OCH3
3
j
O
H C
3
CH3
3
k
123

E. Tabrizian et al.
Table 2 continued
c
Entry Product
Time (h:min) Yield (%) M.P. (ꢁC)
Found
Reported
NO2
O
NO2
Cl
3
l
1
3
4
Cl
O
6:10
5:45
96
97
101–103 102–106 [17]
148–150 147–148 [31]
3
m
b
1
O
Cl
F
Cl
3
n
1
1
1
1
5
6
7
8
O
5:45
5:30
5:50
6:30
95
89
93
92
157–159 154–156 [28]
161–164 163–165 [17]
209–211 208–211 [17]
138–140 137–138 [32]
F
3
o
O
Br
Br
3
p
O
NC
CN
3
q
b
O
3
r
a
1
9
NO
2
O
NO
2
8:00
6:10
83
92
208–211 Not reported
3
s
a
0
2
Cl
O
Cl
181–183 Not reported
3
t
1
23

Synthesis, characterization, and crystal structures of…
Table 2 continued
c
Entry Product
Time (h:min) Yield (%) M.P. (ꢁC)
Found
Reported
2
1
2
O
7:00
6:50
93
170–172 171–172 [32]
H
3
CO
OCH
3
3
u
2
O
94
157–159 156–157 [32]
H
3
C
CH
3
3
v
23
24
25
O
6:00
6:15
5:50
98
95
87
175–178 177–178 [32]
174–177 Not reported
186–189 Not reported
Cl
Cl
3
w
a,b
O
F
F
3
x
a
O
Br
Br
3
y
Reaction conditions: cycloalkanone (1 mmol), aldehyde (2 mmol), nano-TiO
20 drops, EtOH (5 ml), reflux
2
(20 mol %), glacial AcOH
a
New compounds
b
c
New single crystals
Isolated yields
six-membered carbocyclic ketones, while in this paper 4-(tert-butyl)cyclohexanone
was involved in the reaction too (Table 2, entries 18–25).
All the products are identified by the comparison of their melting point data with
those reported in the literature [17, 28, 31, 32] and some of them are characterized
by FT-IR and NMR. In addition, new single crystals (compounds 3n, 3r, and 3x) are
identified by X-ray crystallography (Fig. 4).
123

E. Tabrizian et al.
Fig. 4 Perspective view of the molecules 3n (a), 3r (b), and 3x (c); ellipsoids are drawn at 33 % (50 %
for 3x) probability level, hydrogen atoms are shown as spheres of arbitrary radii. For 3r, only the more-
occupied molecule is shown
In all the structures, the central ring is close to sofa conformation (as can be
seen by the torsion angles values) with five atoms almost coplanar, and the sixth
˚
one, C4, significantly, by more than 0.7 A out of this plane. Overall
conformation of the molecule, which might be described by the dihedral angles
between the terminal planar rings, is influenced by the presence/absence of the t-
butyl substituent at the C4 atom. For 3n (unsubstituted) the dihedral angles for
the symmetry-independent molecules are over 20ꢁ [29.88(11)ꢁ for molecule A,
2
6.87(12)ꢁ for B], while for substituted 3r and 3x the angles are smaller, 7.5(3)ꢁ
1
23

Synthesis, characterization, and crystal structures of…
Scheme 2 The plausible mechanism for the condensation reaction of cycloalkanones and aryl aldehydes
in the presence of nano-TiO /HOAc
2
for 3r and 10.52(7)ꢁ for 3x. In the crystal structures only weak C–HꢀꢀꢀO and
pꢀꢀꢀp contacts can be identified as specific, and to some extent, directional
intermolecular interactions.
0
The proposed mechanism for the formation of a, a -bis(substituted-benzyli-
dene)cycloalkanones is depicted (Scheme 2). Predominantly, the reaction proceeds
via the enolate pathway, wherein ketone (I) is tautomerized to the enolate form (II)
in the presence of acid. The enolate ion is very nucleophilic and attacks the
electrophilic carbonyl group of aromatic aldehyde (III) which is activated by nano-
TiO as a Lewis acid, to form b-hydroxyketone (IV) followed by a dehydration step
2
(
V). The same nucleophilic addition occurs on the other side of ketone (VI) to
obtain symmetric hydroxyketone (VII), followed by dehydration again to give the
final cross-aldol condensation product (VIII).
123

E. Tabrizian et al.
Table 3 Crystal data, data
collection and structure
refinement
3
n
3r
3x
Formula
C
20
H
2
16Cl O
C
24
H
26
O
24 24 2
C H F O
Formula weight
Crystal system
Space group
343.23
Triclinic
P-1
330.45
Orthorhombic Monoclinic
Pca2 P2 /n
366.43
1
1
˚
a (A)
10.2167(5)
11.6210(5)
14.7202(7)
80.474(4)
76.222(4)
87.184(4)
4
12.3099(6)
20.3859(8)
7.6875(4)
90
5.8770(10)
15.834(2)
20.513(3)
90
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
Z
90
95.960(10)
90
90
4
4
3
˚
V (A )
1673.92(14)
1.36
1929.17(16)
1.14
1898.6(5)
1.28
3
(g/cm )
d
x
F(000)
712
712
776
-
1
l (mm
)
0.39
0.51
0.73
h range (ꢁ)
Reflections
Collected
2.9–25.0
2.2–75.3
3.5–75.7
28095
7463
7974
Unique (Rint
)
5895 (0.039) 3363 (0.028)
3818 (0.022)
3379
With I [ 2r(I)
3891
2817
R (F) [I [ 2r(I)]
0.0515
0.0639
0.1762
0.0731
0.1873
1.06
0.0372
0.0898
0.0425
0.0943
1.05
2
wR (F ) [I [ 2r(I)] 0.1011
R (F) (all data)
2
wR (F ) (all data)
0.0896
0.1163
1.03
Goodness of fit
˚
3
Max/min Dq (e/A ) 0.18/-0.21
0.42/-0.20
0.21/-0.19
Conclusion
0
In summary, a mild route for the synthesis of a, a -bis(substituted-benzylidene)cy-
cloalkanones is reported under green conditions. Operational simplicity, simple work-
upwithout column chromatographic purification, reusability ofthe catalyst, tolerance of
various functional groups, and high yields of products are the main advantages of this
protocol. Moreover, five new products and three new single crystals are reported.
Experimental
Chemicals were purchased from the Merck and Aldrich chemical companies. Thin-
layer chromatography (TLC) on commercial aluminum-backed plates of silica gel
6
characterized by FT-IR spectra, H NMR, C NMR. FT-IR spectra were recorded
0 F254 was used to monitor the progress of reactions. The products were
1
13
1
13
on a Shimadzu FT-IR-8400 instrument. H and C NMR spectra were recorded on
1
23

Synthesis, characterization, and crystal structures of…
a Bruker Advance Spectrometer 300 and 75 MHz, respectively, using CDCl -d as
3
the solvent. The chemical shifts are expressed in parts per million (ppm) and
tetramethylsilane (TMS) was used as an internal reference. Melting points were
recorded on a THERMO SCIENTIFIC 9100 apparatus.
Diffraction data were collected by the x-scan technique on an Agilent
Technologies diffractometer [33] for compounds 3r and 3x at 130(1) K on a
SuperNova system with an Atlas CCD detector, equipped with a Nova
˚
microfocus Cu-Ka radiation source (k = 1.54178 A), while for the compound
3
n, an Xcalibur with an Eos CCD detector and graphite-monochromated Mo-Ka
˚
radiation (k = 0.71073 A) was used. The data were corrected for Lorentz
polarization as well as for absorption effects [33]. Precise unit-cell parameters
were determined by a least-squares fit of 4554 (3n), 2919 (3r), and 5222 (3x)
reflections of the highest intensity, chosen from the whole experiment. The
structures were solved with SIR-92 [34] and refined by the full-matrix method
with SHELX-2013 [35]. All non-hydrogen atoms were refined anisotropically.
Hydrogen atoms in 3r were positioned geometrically and refined as riding on
appropriate carrier atom; their displacement parameters were set at 1.2 or 1.5
(CH ) times U of the carrier atoms. All hydrogen atoms in 3n and 3x were
3 eq
located in the difference Fourier maps and freely refined. In the structure of 3r,
the central ring has been found as disordered over two positions with 0.793(16)/
0
.207(16) occupancies; geometry of the less-occupied fragment was constrained.
Relevant crystal data are listed in Table 3 together with refinement details.
CCDC 1030225 (3n), 1030226 (3r), and 1030227 (3x) contain supplementary
crystallographic data for this paper. These data can be obtained free of charge via
www.ccdc.cam.ac.uk/data_request/cif, by e-mailing data_request@ccdc.cam.ac.uk,
or by contacting the Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK.
X-ray powder diffraction analyses were conducted using a Bruker D8 X-ray
diffractometer (Cu-Ka radiation, k = 1.54) for characterization of the heteroge-
neous catalyst. Transmission electron microscopy (TEM) was carried out with a
Philips CM10 instrument. TGA were conducted on a Du Pont 2000 thermal analysis
apparatus under air atmosphere at a heating rate of 5 ꢁC/min.
Preparation of nano-TiO2
Nano-TiO was prepared by the hydrothermal method. NH ꢀH O was added to
2
3
2
TiCl solution until the pH value was 1.8. After stirring for 2 h at 70 ꢁC, the final
4
pH of the solution was adjusted to 6. The resulting suspension was aged at ambient
temperature for 24 h. The final product was filtered, washed with NH Ac–HOAc
4
-
until no Cl was detected. Then the precipitate was separated using a centrifuge,
was washed with ethanol, and dried in a vacuum. After 2 h treatment at 650 ꢁC,
TiO nanoparticles were obtained [29].
2
123

E. Tabrizian et al.
0
General procedure for the synthesis of a, a -bis(substituted-
benzylidene)cycloalkanone derivatives
A mixture of aldehyde (2 mmol), cycloalkanone (1 mmol), 20 mol% of nano-TiO2
0.016 g), and 20 drops of glacial acetic acid was refluxed in ethanol (5 mL) for an
(
appropriate time. After completion of the reaction (monitored by TLC), the catalyst
was filtered. Yellowish crystals of the products were obtained by slow evaporation
of an ethanol solution under room temperature.
Spectral data of some selected compounds
0
a, a -bis(2-nitrobenzylidene)cyclopentanone (3d)
–
1
Yellow crystal; M.P. 168–171 ꢁC; IR (KBr, cm ): mmax: 3080, 2914, 1691, 1517,
1
1
2
1
473; H NMR (300 MHz, CDCl ): d 2.88 (s, 4H), 7.52–7.86 (m, 8H, ArH), 8.10 (s,
3
13
H); CNMR (75 MHz, CDCl ): d 25.98, 125.03, 129.57, 129.66, 130.59, 131.18,
3
33.11, 140.14, 148.86, 194.33.
0
a, a -bis(4-cyanobenzylidene)cyclohexanone (3q)
–
1
Yellow crystal; M.P. 207–211 ꢁC; IR (KBr, cm ): mmax: 2223, 1666, 1577, 1500,
1
1
8
1
139; H NMR (300 MHz, CDCl ): d 1.83 (m, 2H), 2.91 (m, 4H), 7.52–7.71 (m,
3
13
H, ArH), 7.75 (s, 2H); C NMR (75 MHz, CDCl ): d 22.56, 28.30, 112.00,
18.51, 130.57, 132.14, 135.18, 135.22, 138.23, 140.20, 189.29.
3
0
a, a -bis-benzylidene-4-(tert-butyl)cyclohexanone (3r)
-
1
Yellow crystal; M.P. 137–140 ꢁC; IR (KBr, cm ): mmax: 3083, 2867, 1660, 1490,
1
1
446; H NMR (300 MHz, CDCl ): d 0.96 (m, 9H), 1.5 (m, 1H), 2.47 (m, 2H), 3.18
3
13
(
m, 2H),7.33–7.49 (m, 10H, ArH), 7.78 (s, 2H); C NMR (75 MHz, CDCl ): d
3
2
7.27, 29.51, 32.56, 44.42, 128.45, 128.53, 130.30, 136.04, 136.16, 136.85, 190.64.
0
a, a -bis(2-nitrobenzylidene)-4-(tert-butyl)cyclohexanone (3s)
–
1
Yellow crystal; M.P. 209–212 ꢁC; IR (KBr, cm ): mmax: 3075, 2960, 1674, 1519,
1
1
2
2
1
440; H NMR (300 MHz, CDCl ): d 0.78 (s, 9H), 1.50 (m, 1H), 2.18(m, 2H),
3
13
.75(m, 2H), 7.37–8.15 (m, 8H, ArH), 8.17 (s, 2H); C NMR (75 MHz, CDCl ): d
6.92, 29.02, 32.59, 44.24, 125.00, 129.08, 130.94, 132.05, 133.22, 136.04, 137.28,
48.19, 188.82.
3
0
a, a -bis(2-chlorobenzylidene)-4-(tert-butyl)cyclohexanone (3t)
-
1
Yellow crystal; M.P. 181–183 ꢁC; IR (KBr) (cm ) mmax: 3026, 2960, 2864, 1668,
1
1
467, 1434; H NMR (300 MHz, CDCl ): d 0.86 (s, 9H), 1.51 (tt, J = 12.62 Hz,
3
3
.1 Hz, 1H), 2.32 (m, 2H), 2.97 (dd, J = 15.3 Hz/2.2 Hz, 2H), 7.26–7.46 (m, 8H,
1
23

Synthesis, characterization, and crystal structures of…
1
3
ArH), 7.90 (s, 2H); C NMR (75 MHz, CDCl ): d 27.11, 29.36, 32.60, 44.43,
3
1
26.34, 129.56, 129.80, 130.27, 134.04, 134.37, 134.95, 137.68, 189.88.
0
a, a -bis(4-flurobenzylidene)-4-(tert-butyl)cyclohexanone (3x)
-
1
Yellow crystal; M.P. 174–177 ꢁC; IR (KBr) (cm ) mmax: 2956, 2869, 1664, 1602,
1
1
1
2
1
508, 1155; H NMR (300 MHz, CDCl ): d 0.95 (s, 9H), 1.47 (tt, J = 12.7/2.8 Hz,
3
H), 2.41 (m, 2H), 3.11 (dd, J = 15.6/2.3 Hz, 2H), 7.08–7.47 (m, 8H, ArH), 7.73 (s,
3
H); C NMR (75 MHz, CDCl ): d 27.23, 29.37, 32.49, 44.32, 115.45, 115.73,
32.02, 132.06, 132.11, 132.22, 135.65, 135.68, 135.78, 160.94, 164.26, 190.22.
1
3
0
a, a -bis(4-bromobenzylidene)-4-(tert-butyl)cyclohexanone (3y)
-
1
Yellow crystal; M.P. 161–164 ꢁC; IR (KBr) (cm ) mmax: 2958, 2867, 1662, 1604,
1
1
1
2
1
487, 1074; H NMR (300 MHz, CDCl ): d 0.94 (s, 9H), 1.47 (tt, J = 12.8/3.2 Hz,
3
H), 2.40 (m, 2H), 3.09 (dd, J = 15.5/2.3 Hz, 2H), 7.30–7.56 (m, 8H, ArH), 7.68 (s,
1
H); C NMR (75 MHz, CDCl ): d 27.22, 29.42, 32.51, 44.26, 122.89, 131.71,
34.73, 135.76, 136.48, 190.06.
3
3
Acknowledgments We gratefully thank Semnan University for supporting this study.
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