Synthesis and fluorescence properties of α,α'-bis(substituted- benzylidene)cycloalkanones catalyzed by 1-methyl-3(2-(sulfooxy)ethyl)-1h- imidazol-3-ium chloride

Article abstract of DOI:10.1080/00397910903243781

-Bis(substituted-benzylidene)cycloalkanones were synthesized via a solvent-free cross-aldol condensation of aromatic aldehydes with cycloalkanones in the presence of a catalytic amount 1-methyl-3(2-(sulfooxy)ethyl)-1H-imidazol- 3-ium chloride at room temperature with excellent yields. The screening for optical properties indicated that the size of cycloalkanone has an influence on the fluorescence emission of products. Products coming from cyclohexanone have stronger fluorescence emission than those from cyclopentanone. Copyrigh

Full text of DOI:10.1080/00397910903243781

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Synthesis and Fluorescence
Properties of α,α′-Bis(substituted-
benzylidene)cycloalkanones Catalyzed
by 1-Methyl-3(2-(sulfooxy)ethyl)-1H-
imidazol-3-ium Chloride
Yu Wan a b , Xiu-Mei Chen a , Li-Ling Pang a , Rui Ma a , Cai-Hui Yue a
, Rui Yuan a , Wei Lin a , Wei Yin a , Rong-Cheng Bo a & Hui Wu a b
a School of Chemistry and Chemical Engineering, Xuzhou Normal
University , Xuzhou, China
b Key Laboratory of Biotechnology on Medical Plant of Jiangsu
Province , Jiangsu, China
Published online: 07 Jul 2010.
To cite this article: Yu Wan , Xiu-Mei Chen , Li-Ling Pang , Rui Ma , Cai-Hui Yue , Rui Yuan , Wei
Lin , Wei Yin , Rong-Cheng Bo & Hui Wu (2010) Synthesis and Fluorescence Properties of α,α′-
Bis(substituted-benzylidene)cycloalkanones Catalyzed by 1-Methyl-3(2-(sulfooxy)ethyl)-1H-imidazol-3-
ium Chloride, Synthetic Communications: An International Journal for Rapid Communication of
Synthetic Organic Chemistry, 40:15, 2320-2328, DOI: 10.1080/00397910903243781
To link to this article: http://dx.doi.org/10.1080/00397910903243781
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Synthetic Communications1, 40: 2320–2328, 2010
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397910903243781
SYNTHESIS AND FLUORESCENCE PROPERTIES
OF a,a’-BIS(SUBSTITUTED-BENZYLIDENE)-
CYCLOALKANONES CATALYZED BY 1-METHYL-
3(2-(SULFOOXY)ETHYL)-1H-IMIDAZOL-3-IUM
CHLORIDE
Yu Wan,1,2 Xiu-Mei Chen,1 Li-Ling Pang,1 Rui Ma,1
Cai-Hui Yue,1 Rui Yuan,1 Wei Lin,1 Wei Yin,1
Rong-Cheng Bo,1 and Hui Wu1,2
1School of Chemistry and Chemical Engineering, Xuzhou Normal University,
Xuzhou, China
2Key Laboratory of Biotechnology on Medical Plant of Jiangsu Province,
Jiangsu, China
a,a0-Bis(substituted-benzylidene)cycloalkanones were synthesized via a solvent-free cross-
aldol condensation of aromatic aldehydes with cycloalkanones in the presence of a catalytic
amount 1-methyl-3(2-(sulfooxy)ethyl)-1H-imidazol-3-ium chloride at room temperature
with excellent yields. The screening for optical properties indicated that the size of cycloalk-
anone has an influence on the fluorescence emission of products. Products coming from
cyclohexanone have stronger fluorescence emission than those from cyclopentanone.
Keywords: a,a0-Bis(substituted-benzylidene)cycloalkanones; cross-aldol condensation; fluorescence;
synthesis
INTRODUCTION
Cross-aldol condensation of aromatic aldehydes with cyclic ketones is an
important method for the preparation of a,a0-bis(substituted-benzylidene)cycloalka-
nones. The resulting benzylidene derivatives, which have many conjugated unsatu-
rated linkages, are versatile building blocks for many compounds such as
pharmaceuticals, agrochemicals and perfumes, new organic materials for nonlinear
optical application,[1] cytotoxic analogs,[2] and the units of liquid-crystalline poly-
mers.[3] Moreover, they can be used to synthesize some multifunctional group com-
pounds with special structures via Diels–Alder reaction, Michael addition,[4] and so
on. Therefore, it is important to research its synthetic process.
Cross-aldol condensation is classically catalyzed by a strong acid or base.
However, these processes suffer from reverse and side reactions, resulting in poor
Received April 16, 2009.
Address correspondence to Hui Wu, Key Laboratory of Biotechnology on Medical Plant of
Jiangsu Province, Jiangsu 221116, China. E-mail: wuhui72@yahoo.com.cn
2320

a,a0-BIS(SUBSTITUTED-BENZYLIDENE)CYCLOALKANONES
2321
Scheme 1. Synthesis of a,a0-bis(substituted-benzylidene) cycloalkanones.
yields of the products.[5] Different complexes of metal(II) ions have also been used as
catalysts, but the yields were less than 38%.[6] In other cases, Cp2TiPh2,[7] BOMPTO
[bis(p-ehtoxyphenyl)telluroxide],[8] RuCl3,[9] SmI3,[10] Cp2ZrH2,[11] TiCl3(SO3CF3),[12]
KFꢀAl2O3,[13] FeCl3,[14] BF3ꢀOEt2,[15] InCl3,[16] TMSCl=NaI,[17] Yb(OTf)3,[18] I2
,
[19]
TCT[20], NaOAc=HOAc,[21] and NKC-9 (polymer-supported sulfonic acid)[22] have also
been used to promote the reaction. However, these methods have some drawbacks such
as use of costly catalysts and toxic reagents and special catalyst preparation.
Ionic liquids have generated a great amount of interest in organic chemistry as
reaction solvents and catalysts[23–28] in recent years and are emerging as ‘‘green reac-
tion media.’’ Product isolation is very easy in ionic liquids, and in many cases rate
accelerations or selectivity improvements are also observed.
In this article, we report the catalytic potential of 1-methyl-3(2-(sulfoox-
y)ethyl)-1H-imidazol-3-ium chloride (I), which was prepared simply in our labora-
tory from the condensations of aromatic aldehydes and cyclicketones as both
green solvent and catalyst (Scheme 1).
RESULTS AND DISCUSSION
Initially, six Brønsted or Lewis acid were tested in the reaction of 4-methoxyl-
benzaldehyde (4.2 mmol) and cyclohexanone (2.0 mmol) at room temperature
(Scheme 2, Table 1). No product was detected in the control reaction (Table 1, entry
1), and weak acids dodecyl sulfate sodium (SDS) and HOAc (Table 1, entries 5 and
6) did not catalyze this reaction. Silica sulfuric acid, TsOH, HCl, and I (Table 1,
entries 2–4 and 7) promoted the reaction, and I was the most potent catalyst of this
reaction with 96% yield (Table 1, entry 7). Increasing the catalytic load of I from
0.06 mol% to 0.10 mol% improved the yield from 82% to 96%, which showed that
the catalyst concentration plays a major role in the reaction. However, the yield
decreased unexpectedly when the amount of catalyst was more than 0.10 mol%. A
possible explanation for the decrease of yield is that the reaction could drive the
Scheme 2. Six catalysts were tested in the reaction of 4-methoxylbenzaldehyde and cyclohexanone at room
temperature.

2322
Y. WAN ET AL.
Table 1. Control reaction with added amounts of catalyst
Entry
Catalyst
X (mol%)
Time (h)
Yielda (%)
1
2
—
Silica sulfuric acid
—
24
12
10
5
Nrc
60
0.10
0.10
0.10
0.10
0.10
0.10
0.06
0.08
0.12
3
TsOH
HCl
SDSb
HOAc
78
4
73
5
24
24
1
Nrc
Nrc
96
6
7
I
I
I
I
8
1
82
85
9
10
1
1
89
aYield of isolated product.
bSodium dodecyl sulfate (SDS).
cNo reaction.
equilibrium toward reactants when an excess amount (0.12 mol%) of I was added,
and thus 0.10 mol% of I is suitable choice for optimum yield of 2,6-bis(4-
methoxybenzylidene)cyclohexanone (Table 1, entries 7–10).
Table 2. Cross-aldol reaction of aromatic aldehydes and cyclicketonesa
Mp (ꢁC)
Yieldb
(%)
Entry
Ar
n
Time (h)
Product
Found
Reported
1
2
4-OCH3C6H4
4-FC6H4
3-FC6H4
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
2
2
2
2.5
2
2
2
2
1
3
2
3
2
1
1
2
2
1
2
1
3
1
3
1
1
3a
3b
3c
3d
3e
3f
92
92
91
93
91
94
88
90
86
90
96
94
91
91
93
88
95
89
92
89
94
96
210–211
236–237
88–89
211–212[18]
237–239[19]
3
4
4-BrC6H4
3-BrC6H4
251–253
179–181
257–259
>300
5
6
3,4-OCH2OC6H3
4-CNC6H4
3-ClC6H4
7
3g
3h
3i
8
228–229
226–227
115–116
156–157
157–159
87–88
228–229[18]
9
3-NO2C6H4
C6H5
10
11
12
13
14
15
16
17
18
19
20
21
22
3j
117–118[18]
161–163[18]
156–158[17]
4-OCH3C6H4
4-FC6H4
3-FC6H4
3k
3l
3m
3n
3o
3p
3q
3r
3s
3t
3-BrC6H4
4-BrC6H4
2-BrC6H4
118–119
164–165
111–112
182–183
229–230
146–147
198–200
143–144
205–206
119–121[22]
165–168[21]
3,4-OCH2OC6H3
4-CNC6H4
4-ClC6H4
147–148[9]
200–202[19]
3-NO2C6H4
3,4-OCH3C6H3
3,4,5-OCH3C6H2
3u
3v
aReaction conditions: aromatic aldehyde (4.2 mmol) and cyclic ketone (2.0 mmol) were stirred at room
temperature in the presence of I (0.10 mol%) for the given time.
bYield of isolated product.

a,a0-BIS(SUBSTITUTED-BENZYLIDENE)CYCLOALKANONES
2323
Figure 1. Fluorescent emission spectrum of a,a0-bis(substituted-benzylidene)cycloalkanones (1–22: 3a, 3c,
3b, 3d, 3h, 3g, 3f, 3e, 3u, 3l, 3s, 3k, 3r, 3i, 3o, 3j, 3m, 3n, 3v, 3p, 3q, 3t).
Table 3. Luminescence of products
E
max(abs)
kmax(ex)
(nm)
kmax(em)
(nm)
Stokes
(nm)
(Mꢂ1 cmꢂ1
)
RFIa
UF
b
Compound
9,10-Diphe nylanthracene
2.448
2.462
2.377
2.468
2.452
2.472
2.479
2.460
2.528
2.441
2.333
2.379
2.484
2.438
2.413
2.466
2.408
2.406
2.490
2.394
2.523
2.487
2.368
260
256
254
259
257
258
261
258
258
253
253
253
253
252
252
254
252
253
253
253
255
252
252
408
308
308
309
308
310
311
308
309
307
307
307
308
307
307
308
308
307
307
308
308
307
307
2793
588
148
52
54
50
51
52
50
50
51
54
54
54
55
55
55
54
56
54
54
55
53
55
55
0.660
0.140
0.138
0.140
0.145
0.164
0.163
0.161
0.149
0.398
0.382
0.383
0.397
0.401
0.397
0.403
0.401
0.412
0.405
0.385
0.442
0.392
0.390
3a
3b
3c
3d
3e
3f
602
589
611
688
680
678
3g
3h
3i
612
1688
1697
1669
1655
1703
1704
1694
1727
1774
1685
1668
1816
1631
1706
3j
3k
3l
3m
3n
3o
3p
3q
3r
3s
3t
3u
3v
aRelative fluorescence intensity.
bRelative fluorescence quantum yield.

2324
Y. WAN ET AL.
Having optimized the cross-aldol condensation in the presence of I, we decided
to screen a series of aromatic aldehydes (2) and cyclopentanone=cyclohexanone (1)
to evaluate the scope of this reaction. The results summarized in Table 2 show that
excellent yields were achieved for most of the substrates. It appeared that the elec-
tronic nature of the substituted group in aromatic aldehyde has little influence on
yields; both the electron-donating (Me, MeO) and electron-withdrawing (NO2, Cl)
groups worked well with little distinction.
The fluorescence properties of products are shown in Fig. 1 and Table 3 with
better fluorescence efficiency. The following conclusions are clear: (i) All products
have similar fluorescence spectra, and the electro- and steric effects of the substituted
group on aromatic aldehydes have little influence on the fluorescence properties,
which clearly showed that the luminescence of products come from their framework
directly. (ii) The size of cycloalkanone has an effect on the fluorescence emission of
products. Products coming from cyclohexanone have stronger fluorescence emission
than those from cyclopentanone (Fig. 1). Interestingly, in these two series, com-
pounds 3i and 3t (which both derive from 3-nitrobenzaldehyde) have the strongest
fluorescence emission. The possible reason could be due to the different conforma-
tional preferences and the different levels of coplanarity of the extended p systems.
(iii) Besides 3a–h, other products exhibited stronger fluorescence in EtOH on the
presence of 9,10-diphenylanthracence (AF ¼ 0.660, EtOH), which showed their
potential application as new fluorescent probes or luminescence materials.
EXPERIMENTAL
All reagents were purchased from commercial sources and used without further
purification. Thin-layer chromatography (TLC) was performed with glass-backed
plates precoated with silica gel and examined under ultraviolet (UV) light
(254 nm). NMR spectra were measured in CDCl3 with Me4Si as the internal stan-
dards on a Bruker Advance DPX-400 instrument at room temperature. Infrared
(IR) spectra were recorded on Bruker Fourier transform (FT)–IR spectrometer,
and absorbances were reported in centimetersꢂ1. Fluorescence properties were
reported on a F-4500 fluorescence spectrophotometer (Hitachi, Japan). The absorp-
tion spectrum was measured with a Tu-1201 UV spectrophotometer (Shimadzu).
Mass spectra (MS) were determined by using a Bruker MicroTOF-QII high-
resolution mass spectrometer.
General Procedure for the Preparation of
1-Methyl-3(2-(sulfooxy)ethyl)-1H-imidazol-3-ium Chloride
A mixture of 1-methylimidazole (0.3 mol), chloroethanol (0.3 mol), and 10 mL
of CHCl3 was refluxed for 8 h, and then CHCl3 was removed under vacuum. Extrac-
tion of the unreacted 1-methylimidazole with ether gave 1-methyl-3-(2-hydroxylethy-
l)imidazolium chloride. Then chlorosulfonic acid was added dropwise at 0–5 ꢁC;
when the mixture became solid, a suitable single crystal was obtained after 3 days
by recrystallization with dimethylformamide (DMF). This solid inner salt reacted
with chlorosulfonic acid continuously until it became a ropy liquid, 1-methyl-
3(2-(sulfooxy)ethyl)-1H-imidazol-3-ium chloride.

a,a0-BIS(SUBSTITUTED-BENZYLIDENE)CYCLOALKANONES
2325
General Procedure for Preparation of Compounds 3
A mixture of aromatic aldehyde (4.2 mmol), cycloalkanone (2.0 mmol), and I
(0.10 mol%) was stirred at room temperature for 1–3 h (if solid aldehyde was used,
5 drops of anhydrous ethanol were added to the mixture to make it dissolve com-
pletely). Upon completion (monitored by TLC), water was added and the catalyst
was removed by filtration. The product was purified by recrystallization with EtOH.
The analytical data for representative compounds are shown.
Ultraviolet and Fluorescence Measurement of Compounds 3
The EtOH solutions of 3a–v (1.0 ꢃ 10ꢂ6 mol=L) were measured on UV and
fluorescence spectrophotometers to give their absorption and emission spectra,
respectively.
Spectral Data of New Products
2,5-Bis(3-fluorobenzylidene)cyclopentanone (3c). 1H NMR (400 MHz,
CDCl3) d: 3.10 (s, 4H), 7.07 (t, J ¼ 8.0 Hz, 2H), 7.22 (dd, J ¼ 7.2 Hz, J ¼ 10.0 Hz,
4H), 7.37–7.43 (m, 2H); 13C NMR (100 MHz, CDCl3) d: 195.53, 163.84, 161.39,
137.87, 137.57, 132.48, 130.05, 126.46, 116.31, 26.15; IR (KBr, n, cmꢂ1): 3024,
1705, 1619, 1608, 1556; MS (ESI) for C19H14F2O [M þ H] found (expected):
297.1080 (297.1091).
2,5-Bis(4-bromobenzylidene)cyclopentanone (3d). 1H NMR (400 MHz,
CDCl3) d: 3.11 (s, 4H), 7.48 (d, J ¼ 8.0 Hz, 4H), 7.55 (s, 2H), 7.60 (d, J ¼ 8.0 Hz,
2H); 13C NMR (100 MHz, CDCl3) d: 189.73, 137.92, 137.08, 135.53, 132.81,
131.53, 129.94, 128.93, 122.51, 28.33; IR (KBr, n, cmꢂ1): 3069, 1865, 1688, 1625,
1605; MS (ESI) for C19H14Br2O [M þ H] found (expected): 416.9511 (416.9490).
2,5-Bis(3-bromobenzylidene)cyclopentanone (3e). 1H NMR (400 MHz,
CDCl3) d: 3.12 (s, 4H), 7.14–7.18 (m, 4H), 7.59–7.63 (m, 6H); 13C NMR
(100 MHz, CDCl3) d: 195.76, 138.22, 137.76, 133.14, 132.51, 132.31, 130.30,
129.32, 122.93, 26.41; IR (KBr, n, cmꢂ1): 3055, 1854, 1649, 1605, 1588; MS (ESI)
for C19H14Br2O [M þ H] found (expected): 416.9509 (416.9490).
2,5-Bis((benzo[d][1,3]dioxol-5-yl)methylene) cyclopentanone (3f). 1H
NMR (400 MHz, CDCl3) d: 3.09 (s, 4H), 6.05 (s, 4H), 6.91 (d, J ¼ 8.0 Hz, 2H),
7.13–7.17 (m, 4H), 7.53 (s, 2H); 13C NMR (100 MHz, CDCl3) d: 195.20, 148.73,
148.12, 135.54, 133.59, 130.35, 126.75, 109.77, 108.79, 101.57, 26.51; IR (KBr, n,
cmꢂ1): 3056, 1706, 1660, 1600; MS (ESI) for C21H16O5 [M þ H] found (expected):
349.1116 (349.1076).
2,5-Bis(4-cyanobenzylidene)cyclopentanone (3g). 1H NMR (400 MHz,
CDCl3) d: 3.26 (s, 4H), 7.65–7.69 (m, 4H), 7.91 (d, J ¼ 8.0 Hz, 2H), 8.27–8.29 (m,
2H), 8.49 (s, 2H); 13C NMR (100 MHz, CDCl3) d: 194.71, 154.62, 150.65, 149.11,
148.02, 134.45, 130.56, 26.54; IR (KBr, n, cmꢂ1): 3106, 2256, 1706, 1649, 1608,
1522; MS (ESI) for C21H14N2O [M þ H] found (expected): 311.1164 (311.1184).

2326
Y. WAN ET AL.
2,5-Bis(3-nitrobenzylidene)cyclopentanone (3i). 1H NMR (400 MHz,
CDCl3) d 3.13 (s, 4H), 7.32–7.36 (m, 2H), 7.52–7.54 (m, 6H), 7.74 (s, 2H); 13C
NMR (100 MHz, CDCl3) d: 195.33, 148.63, 139.24, 137.15, 136.42, 131.73, 129.91,
124.51, 123.93, 26.40; IR (KBr, n, cmꢂ1): 3069, 1728, 1640, 1606, 1524; MS (ESI)
for C19H14N2O5 [M þ H] found (expected): 351.0995 (351.0981).
2,6-Bis(3-fluorobenzylidene)cyclohexanone (3m). 1H NMR (400 MHz,
CDCl3) d: 1.78–1.85 (m, 2H), 2.88–2.94 (m, 4H), 6.97–7.10 (m, 2H), 7.13–7.27 (m,
4H), 7.35–7.50 (m, 2H), 7.74 (s, 2H); 13C NMR (100 MHz, CDCl3) d: 189.91,
163.83, 161.39, 138.03, 136.97, 135.81, 129.99, 126.30, 116.83, 115.68, 28.38, 22.78;
IR (KBr, n, cmꢂ1): 3023, 1705, 1619, 1608, 1556; MS (ESI) for C20H16F2O
[M þ H] found (expected): 311.1356 (311.1247).
2,6-Bis(2-bromobenzylidene)cyclohexanone (3p). 1H NMR (400 MHz,
CDCl3) d 1.77–1.80 (m, 2H), 2.76–2.79 (m, 4H), 7.20–7.24 (m, 2H), 7.34–7.36 (m,
4H), 7.66 (d, J ¼ 7.6 Hz, 2H), 7.87 (s, 2H); 13C NMR (100 MHz, CDCl3) d:
189.67, 137.44, 136.42, 136.29, 132.98, 130.55, 129.74, 126.90, 125.17, 28.32, 23.15;
IR (KBr, n, cmꢂ1): 3067, 1845, 1625, 1589, 1558; MS (ESI) for C20H16Br2O
[M þ H] found (expected): 430.9647 (430.9646).
2,6-Bis((benzo[d][1,3]dioxol-5-yl)methylene)cyclohexanone
(3q). 1H
NMR (400 MHz, CDCl3) d 1.81–1.84 (m, 2H); 2.92 (t, J ¼ 5.2 Hz, 4H), 6.03 (s,
4H), 6.87 (d, J ¼ 8.0 Hz, 2H), 7.01–7.04 (m, 4H), 7.73 (s, 2H); 13C NMR
(100 MHz, CDCl3) d: 190.06, 148.02, 147.71, 136.73, 134.65, 130.20, 125.86,
110.06, 108.44, 101.39, 28.54, 22.96; IR (KBr, n, cmꢂ1): 3058, 1706, 1660, 1600;
MS (ESI) for C22H18O5 [M þ H] found (expected): 363.1313 (363.1232).
2,6-Bis(4-cyanobenzylidene)cyclohexanone (3r). 1H NMR (400 MHz,
CDCl3) d: 1.85–1.86 (m, 2H), 2.94 (t, J ¼ 5.2 Hz, 4H), 7.56 (d, J ¼ 8.0 Hz, 4H),
7.72–7.78 (m, 6H); 13C NMR (100 MHz, CDCl3) d: 189.01, 140.02, 138.07, 134.92,
131.90, 130.34, 130.62, 118.24, 111.81, 28.07, 22.35; IR (KBr, n, cmꢂ1): 3104,
2256, 1706, 1649, 1608, 1522; MS (ESI) for C22H16N2O [M þ H] found (expected):
325.1344 (325.1341).
2,6-Bis(3,4-dimethoxybenzylidene) cyclohexanone (3u). 1H NMR
(400 MHz, CDCl3) d: 1.84–1.86 (m, 2H), 2.97 (t, J ¼ 5.2 Hz, 4H), 3.94 (d, J ¼ 4.0 Hz,
Hz, 12H), 6.93 (d, J ¼ 8.4 Hz, 2H), 7.05 (s, 2H), 7.14 (d, J ¼ 8.4 Hz, 2H), 7.78 (s, 2H);
13C NMR (100 MHz, CDCl3) d: 190.05, 149.63, 148.68, 136.83, 134.52, 129.01,
123.94, 113.74, 110.91, 55.96 (ꢃ2), 28.55, 23.06; IR (KBr, n, cmꢂ1): 3013, 1703,
1661, 1595, 1505, 1248; MS (ESI) for C24H26O5 [M þ H] found (expected):
395.1912 (395.1858).
2,6-Bis(3,4,5-trimethoxybenzylidene)cyclohexanone (3v). 1H NMR
(400 MHz, CDCl3) d: 1.85–1.87 (m, 2H), 2.98 (t, J ¼ 5.2 Hz, 4H), 3.89–3.92 (m,
18H), 6.73–6.75 (m, 4H), 7.75 (s, 2H); 13C NMR (100 MHz, CDCl3) d: 189.98,
153.01, 138.78, 137.15, 135.40, 131.46, 107.88, 61.02, 56.73, 28.48, 23.02; IR (KBr,
n, cmꢂ1): 3025, 1708, 1665, 1585, 1505, 1345; MS (ESI) for C26H30O7 [M þ H] found
(expected): 455.2114 (455.2070).

a,a0-BIS(SUBSTITUTED-BENZYLIDENE)CYCLOALKANONES
2327
CONCLUSION
In conclusion, we have developed a simple and efficient cross-aldol conden-
sation of aromatic aldehydes with cyclic ketones to form a,a0-bis(substituted-benzy-
lidene) cycloalkanones using 1-methyl-3(2-(sulfooxy)ethyl)-1H-imidazol-3-ium
chloride as catalyst at room temperature. Because of its benefits, the protocol may
be used to synthesize a variety of multifunctional compounds. Some products have
potential application as new fluorescent probes, luminescence materials, or ligands.
Future effort to explore the coordination function of products is under way.
ACKNOWLEDGMENTS
We are grateful to the National Natural Sciences Foundation of China (No.
20772103), the Natural Science Foundation in Jiangsu Province (No. BK2007028),
and the Surpassing Project in Jiangsu Province (Nos. QL200607 and 08QLT001)
for financial support.
REFERENCES
1. Kawamata, J.; Inoue, K.; Inabe, T.; Kiguchi, M.; Kato, M.; Taniguchi, Y. Large
second-harmonic generation coefficients of bis(benzylidene)cycloalkanones estimated by
the second-harmonic wave generated with the evanescent wave technique. Chem. Phys.
Lett. 1996, 249, 29–34.
2. Dimmock, J. R. A.; Padmanilayam, M. P.; Zello, G. A.; Nienaber, K. H.; Allen, T. M.;
Santos, C. L.; De Clercq, E.; Balzarini, J.; Manavathu, E. K.; Stables, J. P. Cytotoxic ana-
logues of 2,6-bis (arylidene)cyclohexanones. Eur. J. Med. Chem. 2003, 38, 169–177.
3. Gangadhara; Kaushal, K. Synthesis and characterization of photo-crosslinkable main-
chain liquid-crystalline polymers containing bis(benzylidene)cycloalkanone units. Polymer
1995, 36, 1903–1910.
4. Warela, M. C.; Dixon, S. M.; Larn, K. S.; Schore, N. E. Asymmetric epoxidation, Michael
addition, and triple cascade reaction using polymer-supported, prolinol-based auxiliaries.
Tetrahedron 2008, 64, 10087–10090.
5. Hathaway, B. A. An aldol condensation experiment using a number of aldehydes and
ketones. J. Chem. Educ. 1987, 64, 367–368.
6. Irie, K.; Watanabe, K. Aldol condensations with metal(II) complex catalysts. Bull. Chem.
Soc. Jpn. 1980, 53, 1366–1371.
7. Nakano, T.; Migita, T. A convenient synthesis of a,a0-bis(substituted-benzylidene)
cycloalkanones. Chem. Lett. 1993, 2157–2158.
8. Zheng, M.; Wang, L.; Shao, J.; Zhong, Q. A facile synthesis of a,a0-bis(substituted benzy-
lidene)cycloalkanones catalyzed by bis(p-ethoxyphenyl)telluroxide (BMPTO) under
microwave irradiation. Synth. Commun. 1997, 27, 351–354.
9. Iranpoor, N.; Kazemi, F. RuCl3-catalyzed aldol condensation of aldehydes and ketones.
Tetrahedron 1998, 54, 9475–9480.
10. Bao, W. L.; Zhang, Y. M. Convenient preparation of a,a0-bis(substituted-benzylidene)
cycloalkanones promoted by SmI3. Chin. Org. Chem. 1998, 18, 272–274.
11. Nakano, T.; Irfune, S.; Umano, S.; Inada, A.; Ishii, Y.; Ogawa, M. Cross-condensation
reactions of cycloalkanones with aldehydes and primary alcohols under the influence of
zirconocene complexes. J. Org. Chem. 1987, 52, 2239–2244.

2328
Y. WAN ET AL.
12. Iranpoor, N.; Zeynizadeh, B.; Aghapour, B. Aldol condensation of cycloalkanones with
aromatic aldehydes catalyzed with TiCl3(OTf). J. Chem. Res. 1999, 554–555.
13. Yaday, J. S.; Reddy, B. V. S.; Nagaraju, A.; Sarma, J. A. R. P. Microwave-assisted syn-
thesis of a,a0-bis(benzylidene)ketones in dry media. Synth. Commun. 2002, 32, 893–896.
14. Zhang, X. Y.; Fan, X. S.; Niu, H. Y.; Wang, J. J. Ionic liquid as a recyclable medium for
the green preparation of a,a0-bis(substituted benzylidene)cycloalkanones catalyzed by
FeCl3 ꢀ 6H2O. Green Chem. 2003, 5, 267–269.
15. Huang, D. F.; Wang, J. X.; Hu, Y. L.
A new solvent-free synthesis of
a,a0-dibenzylidenecycloalkanones from acetals with cycloalkanones under microwave
irradiation. Chin. Chem. Lett. 2003, 14, 333–334.
16. Deng, G.; Ren, T. Indium trichloride catalyzes aldol condensations of aldehydes and
ketones. Synth. Commun. 2003, 33, 2995–3001.
17. Sabitha, G.; Reddy, G. S. K.; Reddy, K. B.; Yaday, J. S. Iodotrimethylsilane-mediated
cross-aldol condensation: A facile synthesis of a,a0-bis(substituted-benzylidene)cycloalka-
nones. Synthesis 2004, 263–266.
18. Wang, L.; Sheng, J.; Tian, H.; Han, J.; Fan, Z.; Qian, C. A convenient synthesis of
a,a0-bis(substituted-benzylidene)cycloalkanones catalyzed by Yb(OTf)3 under solvent-free
conditions. Synthesis 2004, 3060–3064.
19. Biswanath, D.; Ponnaboina, T.; Ibram, M.; Kongara, R. R. Convenient and facile
cross-aldol condensation catalyzed by molecular iodine: An efficient synthesis of
a,a0-bis(substituted-benzylidene)cycloalkanones. J. Mol. Cat. A: Chem. 2006, 247,
182–185.
20. Mohammad, A. B.; Gholam, H. M.; Saeed, J.; Hassan, H. Wet 2,4,6-trichloro[1,3,5]tria-
zine (TCT), an efficient catalyst for synthesis of a,a0-bis(substituted-benzylidene)cycloalk-
anones under solvent-free conditions. Cat. Commun. 2007, 8, 2228–2230.
21. Rahman, M. A. F. M.; Jeong, B.-S.; Kim, D. H.; Park, J. K.; Lee, E. S.; Jahng, Y. A facile
synthesis of a,a0-bis(substituted-benzylidene)cycloalkanones and substituted-benzylidene
heteroaromatics: Utility of NaOAc as catalyst for aldol-type reaction. Tetrahedron
2007, 63, 2426–2431.
22. An, L. T.; Zou, J. P.; Zhang, L. L. Polymer-supported sulphonic acid–catalyzed
cross-aldol condensation: An expeditious synthesis of a,a0-bis(substituted-benzylidene)cy-
cloalkanones. Catal. Commun. 2008, 9, 349–354.
23. Parvulescu, V. I.; Hardacre, C. Catalysis in ionic liquids. Chem. Rev. 2007, 107,
2615–2665.
24. Dupont, J.; de Souza, R. F.; Suarez, P. A. Z. Ionic liquid (molten salt) phase organome-
tallic catalysis. Chem. Rev. 2002, 102, 3667–3692.
25. Wasserscheid, P.; Welton, T. Ionic Liquids in Synthesis; Wiley-VCH: New York, 2002.
26. Welton, T. Room-temperature ionic liquids solvents for synthesis and catalysis. Chem.
Rev. 1999, 8, 2071–2084.
27. Wasserschied, P.; Keim, W. Ionic liquids—New ‘‘solutions’’ for transition metal catalysis.
Angew. Chem. Int. Ed. 2000, 39, 3772–3789.
28. Davis, J. H.; Fox, P. A. From curiosities to commodities: Ionic liquids begin the tran-
sition. Chem. Commun. 2003, 11, 1209–1212.