Aldol condensations of aldehydes and ketones catalyzed by rare earth(III) perfluorooctane sulfonates in fluorous solvents

Article abstract of DOI:10.1016/j.jfluchem.2005.09.004

Rare earth(III) perfluorooctane sulfonates (RE(OPf)₃) catalyze the efficient aldol condensation of different ketones with various aromatic aldehydes in fluorous solvents without the occurrence of any self-condensations. By simple separation of the fluorous phase containing only catalyst, reaction can be repeated several times.

Full text of DOI:10.1016/j.jfluchem.2005.09.004

Journal of Fluorine Chemistry 126 (2005) 1553–1558
www.elsevier.com/locate/fluor
Aldol condensations of aldehydes and ketones catalyzed by rare
earth(III) perfluorooctane sulfonates in fluorous solvents
*
Wen-Bin Yi, Chun Cai
Chemical Engineering College, Nanjing University of Science and Technology, Nanjing 210094, China
Received 8 September 2005; accepted 8 September 2005
Available online 20 October 2005
Abstract
Rare earth(III) perfluorooctane sulfonates (RE(OPf)3) catalyze the efficient aldol condensation of different ketones with various aromatic
aldehydes in fluorous solvents without the occurrence of any self-condensations. By simple separation of the fluorous phase containing only
catalyst, reaction can be repeated several times.
# 2005 Elsevier B.V. All rights reserved.
Keywords: Aldol condensations; Fluorous biphasic catalysis; Rare earth(III) perfluorooctanesulfonates; Perfluorocarbon
1. Introduction
reusing of these catalysts required tedious work up procedures
such as filtration, purification and drying. Therefore, we believe
that the application of fluorous phase separation techniques in
catalysis can be used to the aldol condensation catalyzed by
RE(OPf)3 which has stronger Lewis acidity than RE(OTf)3. In
this paper, a green process of aldol condensations of aldehydes
and ketones catalyzed by rare earth(III) perfluorooctane
sulfonates in fluorous solvents was studied.
Aldol condensation reactions are important synthetic
reactions and in classical methods, they were performed in
the presence of strong acids or bases [1]. In order to do these
reactions under neutral conditions, some metal ions are used as
catalyst or reagent [2]. For example, the use of different
complexes of metal(II) ions, such as Mn(II), Fe(II), Co(II),
Ni(II), Cu(II) and Zn(II) with different ligands have been used
for aldol-condensations [2a]. Recently, a new kind of Lewis
acids of rare earth(III) perfluorooctane sulfonates (RE(O-
SO2C8F17)3, RE(OPf)3, RE = Sc, Y, La–Lu) was of special
interest [3–5]. The characteristic features of the catalyst include
low hygroscopicity, ease of handling, robustness for the
recycling using and high solubility in fluorous solvent [4]. On
the other hand, perfluorocarbon solvents, especially perfluoro-
alkanes have some unique properties which make them
attractive alternatives for conventional organic solvents [6].
The compounds functionalized with perfluorinated groups
often dissolve preferentially in fluorous solvents and this
property can be used to extract fluorous components from
reaction mixtures [7]. Aldol condensations of aldehydes and
ketones catalyzed by rare earth(III) trifluoromethanesulfonates
(RE(OSO2CF3)3, RE(OTf)3) were reported [8]. However,
2. Results and discussion
Due to the importance of methylene structural unit which are
found in many naturally occurring compounds and antibiotics
and the use of a,a0-bis(substituted) benzylidene cycloalk-
anones as precursors for synthesis of bioactive pyrimidine
derivatives, condensation of cyclopentanone and cyclohex-
anone with aldehydes and ketones were of special interest [2f].
Thus, we studied the cross-condensations of cyclopentanone
and cyclohexanone with different aromatic aldehydes such as,
benzaldehyde, p-chlorobenzaldehyde, p-nitrobenzaldehyde, p-
methylbenzaldehyde, p-methoxybenz-aldehyde and cinnamal-
dehyde. Firstly, The reaction of cyclohexanone with benzalde-
hyde was adopted for the evaluation of catalysts (Scheme 1).
The results are summarized in Table 1. Among these catalysts,
Sc(OPf)3 and Yb(OPf)3 are the most efficient catalysts for the
condensation. This would be ascribed to the higher Lewis
acidity of Sc(OPf)3 and Yb(OPf)3 than those of other RE(OPf)3
[9]. The control experiment elucidates that no product of cross-
* Corresponding author. Fax: +86 25 84315030.
E-mail address: yiwenbin5@163.com (C. Cai).
0022-1139/$ – see front matter # 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2005.09.004

1554
W.-B. Yi, C. Cai / Journal of Fluorine Chemistry 126 (2005) 1553–1558
Scheme 1.
Scheme 2.
condensations could be obtained in the absence of catalyst and
fluorous solvent. In addition, we found that a catalyst loading of
only 0.4 mol% was required when using fluorous phase
technology. Next, the effect of fluorous solvents such as,
perfluorohexane (C6F14), perfluoromethylcyclohexane (C7F14),
perfluorotoluene (C7F8), perfluorooctane (C8F18), perfluorooc-
tyl bromide (C8F17Br) and perfluorodecalin (C10F18, cis and
trans-mixture) was examined for the condensations (Table 1,
entries 16–21). The results showed that yields of the desired
products in perfluorooctane (C8F18) and perfluorooctyl bromide
(C8F17Br) were lower than other solvents. The fluorous solvents
perfluorohexane (C6F14) and perfluorotoluene (C7F8) are in fact
miscible with reaction substrates such as cyclohexanone at
room temperature. Thus, it is impossible to recover fluorous
phase by phase-separation. At the same time, we found that
during repeated condensation reactions the loss of fluorous
solvent is very serious when using perfluoromethylcyclohexane
(C7F14) as a fluorous solvent because it is very volatile (bp
76 8C). Therefore, perfluorodecalin (C10F18, cis and trans-
mixture) is the best fluorous solvent for the condensation.
Heptadecafluorooctane-sulfonic acid (C8F17SO3H, PfOH)
itself can promote the reaction, but it was found to be less
effective than RE(OPf)3.
Table 2
Condensation of cyclopentanone and cyclohexanone with various aromatic
aldehydesa
Entry
N
Ar
Temperature (8C)
Time (h)
Yield (%)b
1
2
1
1
1
1
1
1
0
0
0
0
0
4-ClPh
120
120
120
120
120
120
120
120
120
120
120
12
4
95
92
94
97
96
89
92
91
95
93
86
4-CH3Ph
4-CH3OPh
4-NO2Ph
Cinnamyl
Furfuryl
Ph
3
18
24
16
24
8
4
5
6
7
8
4-CH3OPh
4-NO2Ph
Cinnamyl
Furfuryl
18
24
8
9
10
11
24
a
The mole ratio of ketone to aromatic aldehyde in all cases is 5:3.
Isolated yields based on the benzaldehyde.
b
In order to seek out a practical, useful aldol condensation
process, we decided to use the relatively cheap and similarly
active catalyst Yb(OPf)3 and perfluorodecalin (C10F18, cis and
trans-mixture) as a fluorous solvent for condensations of
cyclopentanone and cyclohexanone with various aromatic
aldehydes (Scheme 2). The results are shown in Table 2. The
reactions were finished within 4–24 h and excellent yields (86–
97%) of a,a0-bis(substituted) benzylidene cyclopentanones and
cyclohexanones were obtained, regardless of the kind of
substituent group on benzaldehyde. Under the conditions
described in Table 2, Yb(OPf)3 catalyzed the efficient cross
aldol condensations without the occurrence of any self-
condensations.
Table 1
Condensation of cyclohexanone with benzaldehydea
Entry
Catalyst
Fluorous
solvent
Yield (%)b
c
1
2
Sc(OPf)3
Y(OPf)3
C10F18
96
78
69
80
60
88
73
66
77
72
84
86
90
79
78
95
89
97
96
82
81
53
C10F18
3
La(OPf)3
Ce(OPf)3
Pr(OPf)3
Nd(OPf)3
Sm(OPf)3
Eu(OPf)3
Gd(OPf)3
Tb(OPf)3
Dy(OPf)3
Ho(OPf)3
Er(OPf)3
Tm(OPf)3
Lu(OPf)3
Yb(OPf)3
Yb(OPf)3
Yb(OPf)3
Yb(OPf)3
Yb(OPf)3
Yb(OPf)3
PfOH
C10F18
In order to ascertain the scope and limitation of this
catalyzed condensation, the use of the catalytic systems was
extend to condensation of aliphatic and aromatic ketones with
various aldehydes (Scheme 3, Table 3). The reaction products
were isolated and identified as a,b-unsaturated ketones, and no
side reactions were observed. Based on 1H NMR and GC–MS
data, the reaction was found to give E-stereoisomer as sole
product. The purity of the products thus obtained was
consistently high, probably because the perflates-catalyzed
reactions took place under neutral conditions. In general,
reactions between aromatic aldehydes and ketones gave good
results, but not those of aliphatic compounds. The condensa-
tions of p-substituted benzaldehyde with p-substituted acet-
ophenones yielded the corresponding chalcones and the
4
C10F18
5
C10F18
6
C10F18
7
C10F18
8
C10F18
9
C10F18
10
11
12
13
14
15
16
17
18
19
20
21
22
C10F18
C10F18
C10F18
C10F18
C10F18
C10F18
C10F18
CF3(CF2)4CF3
C6F5CF3
C6F13CF3
CF3(CF2)6CF3
CF3(CF2)6CF2Br
C
10F18
a
The mole ratio of cyclohexane to benzaldehyde in all cases is 5:3.
b
c
Isolated yields based on the benzaldehyde.
.
Scheme 3.

W.-B. Yi, C. Cai / Journal of Fluorine Chemistry 126 (2005) 1553–1558
1555
Table 3
Condensation of acyclic ketones with various aromatic aldehydesa
Entry
R1
R2
R3
Temperature
Time
(h)
Yield
(%)b
(8C)
1
2
Ph
H
Ph
120
120
120
120
120
120
120
120
80
24
24
24
24
24
24
24
32
72
48
48
48
48
48
48
72
72
72
72
85
69
95
89
76
65
96
41
32
77
75
58
51
46
37
7
4-CH3OPh
4-NO2Ph
Ph
H
Ph
3
H
Ph
4
H
4-ClPh
4-CH3Ph
4-CH3OPh
4-NO2Ph
Cinnamyl
(CH3)2CH
Ph
5
Ph
H
6
Ph
H
7
Ph
H
8
Ph
H
9
Ph
H
10
11
12
13
14
15
16
17
18
19
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
H
80
H
4-CH3OPh
Ph
80
CH3
CH3
C2H5
C2H5
H
80
4-CH3OPh
Ph
80
80
4-CH3OPh
C2H5
80
60
H
C3H7
80
4
CH3
CH3
C2H5
60
6
C3H7
80
3
a
The mole ratio of ketone to aromatic aldehyde in all cases is 5:3.
Isolated yields based on the benzaldehyde.
b
product yields were remarkably affected by the subsitituent
groups of either aldehydes of ketones: reactants having
electron-withdrawing substituents gave high yields and those
having electron-donating ones gave low yields. The reactions of
various aromatic aldehydes with acetone gave corresponding
a,b-unsaturated ketones in good yields. It was known that the
base-catalyzed reactions of 2-butanone with benzaldehyde gave
preferentially the condensation product at C1 of ketone, while
the acid catalyzed reaction occurred preferentially at C3. The
obtained results from condensation of 2-butanone and 2-
pentanone with different aromatic aldehydes showed excellent
regioselectivity with the occurrence of condensation from C3.
The catalyst Yb(OPf)3 system appeared to show no catalytic
activity for the condensation of the aliphatic ketones such as
acetone and 2-butanone with the aliphatic aldehydes, propanal
and pentanal.
could be reused for the next reaction without any treatment, and
this workup procedure of recycling was accomplished by
simple phase-separation.
In conclusion, RE(OPf)3 are demonstrated to be new and
highly effective catalysts for condensations of aromatic
aldehyhes and ketones in fluorous solvents. By simple
separation of the fluorous phase containing only catalyst,
reaction can be repeated several times. The simple procedures
as well as easy recovery and reuse of this novel catalytic system
are expected to contribute to the development of more benign
aldol condensation.
3. Experimental
3.1. General
Attempts were made to recycle the catalytic system. The
condensations of cyclohexanone and acetophenone with
benzaldehyde under the conditions as mentioned above were
run for five consecutive cycles, respectively, furnishing the
corresponding a,a0-bis(substituted) benzylidene cyclopenta-
nones with 95, 95, 93, 92, 92% isolated yields and chalcone
with 85, 84, 85, 84, 83% isolated yields. The robustness of the
catalyst for recycling using may partly be attributed to the
water-repellent nature of the perfluoroalkane chain ‘‘(–CF2–
CF2–)n’’ of RE(OPf)3 which refuses the approach of water or
acid molecules to the central metal cation, thus maintaining its
high Lewis acidity [9]. When the reaction was finished, the
reaction mixture was cooled to room temperature.
MPs were obtained with Shimadzu DSC-50 thermal analyzer.
IR spectra were recorded on a Bumem MB154S infrared
1
analyzer. H NMR spectra were measured on Bruke Advance
RX300. Mass spectra were recorded with a Saturn 2000GC/MS
instrument. Inductively coupled plasma (ICP) spectra were
measured on Ultima2C apparatus. Elemental analyses were
performed on a Yanagimoto MT3CHN corder. Commercially
available reagents were used without further purification.
3.2. Typical procedure for preparation of RE(OPf)3
RE(OPf)3 was prepared according to the literatures [4]
(MethodA). Themixture ofPfOHsolution(aq) andYbCl3ꢀ6H2O
solution (aq) was stirred at room temperature (Method B). The
mixture of PfOH solution (aq) and Yb2O3 powder was stirred at
boiling. In both methods, the resulting gelatin-like solid was
collected, washed and dried at 150 8C in vacuo to give a white
The fluorous phase with RE(OPf)3 catalysts can separate
from the organic layer return to the bottom layer. Based on GC–
MS data, no loss of fluorous solvent to the organic phase can be
detected. The separated fluorous phase containing only catalyst

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W.-B. Yi, C. Cai / Journal of Fluorine Chemistry 126 (2005) 1553–1558
solid, which does not have a clear melting point up to 500 8C, but
shrinks around 380 8C and 450 8C. IR (KBr) n (cmꢁ1) 1237
(CF3), 1152 (CF2), 1081 (SO2), 1059 (SO2), 747 (S–O) and 652
(C–S). ICP: Calcd. for C24O9F51S3Yb: Yb, 10.30%. Found: Yb,
9.88%. Anal. Calcd. for C24O9F51S3YbꢀH2O: C, 17.21%; H,
0.10%. Found: C, 17.03%; H, 0.18%.
1546, 1278, 1147, 1010, 764 cmꢁ1. 1H NMR (300 MHz, TMS,
CDCl3) d 2.16–2.54 (m, 2H), 2.95 (d, 4H), 6.20–7.72 (m, 8H).
MS (EI) m/z 253 (M+).
2,6-Dibenzylidenecyclopentanone. A brown solid; mp
188 8C (lit2e 188–189 8C). IR (KBr) n 3100, 2926, 1654,
1
1598, 1460,1260, 760, 674 cmꢁ1. H NMR (300 MHz, TMS,
CDCl3) d 2.76 (t, 4H), 7.26–7.38 (m, 10H), 7.68 (s, 2H). MS
(EI) m/z 259 (M+).
3.3. Typical procedure for condensation of aldehydes with
ketones
2,6-Di(p-methoxybenzylidene)cyclopentanone.
solid; mp 211–212 8C (lit2e 210–211 8C). IR (KBr) n 2962,
2841, 1649, 1595, 1506, 1253, 1020, 834 cmꢁ1 1H NMR
A
green
Benzaldehyde (1.2 ml, 12 mmol) was slowly added into a
mixture of Yb(OPf)3 (80 mg, 0.048 mmol), cyclohexone
(2.1 ml, 20 mmol) and perfluorodecalin (C10F18, cis and
trans-mixture, 1.5 ml). The mixture was stirred at 120 8C for
12 h. Then, the fluorous layer on the bottom was separated for
the next condensation. The reaction mixture (organic phase)
was poured into cold ethanol (20 ml) and stirred for 5 min and
filtered. The crystalline product was further washed subse-
quently with water (10 ml), 10% NaHCO3 solution (10 ml) and
water (10 ml ꢂ 2), cold ethanol (10 ml) and dried to give the
product 2,6-dibenzylidenecyclohexanone (1.56 g, 95%).
2,6-Dibenzylidenecyclohexanone. A yellow solid; mp 116–
118 8C (lit2e 116–117 8C). IR (KBr) n 3020, 2924, 1657, 1604,
.
(300 MHz, TMS, CDCl3) d 3.09 (t, 4H), 3.86 (s, 6H), 6.96–7.56
(m, 8H), 7.58 (s, 2H). MS (EI) m/z 319 (M+)
2,6-Di(p-nitrobenzylidene)cyclopentanone. A russety solid;
mp 230–231 8C (lit2e 230–231 8C). IR (KBr) n 3105, 2847,
1706, 1605, 1521, 1344, 816 cmꢁ1. 1H NMR (300 MHz, TMS,
CDCl3) d 3.07 (t, 4H), 7.62–8.12 (m, 8H), 8.27 (s, 2H). MS (EI)
m/z 349 (M+).
2,6-Dicinnamylidenecyclopentanone. A purple solid; mp
223–224 8C (lit2e 222–224 8C). IR (KBr) n 3024, 2925, 1698,
1625, 1598, 1447, 690 cmꢁ1 1H NMR (300 MHz, TMS,
.
CDCl3) d 2.86 (m, 4H), 6.70 (d, J = 16.2 Hz, 2H), 6.76 (d,
J = 16.2 Hz, 2H), 6.81–7.70 (m, 10H), 7.72 (s, 2H). MS (EI) m/
z 311 (M+).
1
1570, 1271, 1142, 770, 692 cmꢁ1. H NMR (300 MHz, TMS,
CDCl3) d 1.76–1.87 (m, 2H), 2.95 (t, J = 6.4 Hz, 4H), 7.30–7.48
(m, 10H), 7.80 (s, 2H). MS (EI) m/z 273 (M+).
2,6-Difurfurylidenecyclopentanone. A russety solid; mp
161 8C (lit2e 160–162 8C). IR (KBr) n 3130, 2931, 1683, 1625,
2,6-Di(p-chlorobenzylidene)cyclohexanone. A brown solid;
mp 149–151 8C (lit2f 147–148 8C). IR (KBr) n 2930, 1660,
1600, 1287, 1240, 754 cmꢁ1 1H NMR (300 MHz, TMS,
.
CDCl3) d 2.98 (m, 4H), 2.95 (d, 4H), 6.30–7.62 (m, 8H). MS
(EI) m/z 239 (M+).
1606, 1576, 1262, 828 cmꢁ1 1H NMR (300 MHz, TMS,
.
CDCl3) d 1.76–1.84 (m, 2H), 2.90 (t, J = 6.0 Hz, 4H), 7.36–7.43
(m, 8H), 7.73 (s, 2H). MS (EI) m/z 346 (M+ + 4), 344 (M+ + 2),
342 (M+).
Chalcone. A yellowish solid; mp 55–57 8C (lit2b 57–58 8C).
IR (KBr) n 3230, 2934, 1830, 1725, 1650, 1287, 754, 685 cmꢁ1
.
1H NMR (300 MHz, TMS, CDCl3) d 6.12 (d, J = 16.0 Hz, 1H),
7.26 (d, J = 16.0 Hz, 1H), 7.10–7.32 (m, 5H), 7.42–7.92 (m,
5H). MS (EI) m/z 207 (M+).
2,6-Di(p-methylbenzylidene)cyclohexanone. A yellowish
solid; mp 170–171 8C (lit2f 170 8C). IR (KBr) n 2980, 2944,
1666, 1600, 1560, 1268, 1140, 760, 698 cmꢁ1
.
1H NMR
40-Methoxychalcone. A russety solid; mp 109–110 8C (lit2b
109–110 8C). IR (KBr) n 3200, 2886, 1830, 1725, 1660, 1212,
(300 MHz, TMS, CDCl3) d 1.78–1.86 (m, 2H), 2.30 (s, 6H),
2.92 (t, J = 6.2 Hz, 4H), 7.22–7.38 (m, 8H), 7.76 (s, 2H). MS
(EI) m/z 301 (M+).
1
854, 734 cmꢁ1. H NMR (300 MHz, TMS, CDCl3) d 3.78 (s,
3H), 6.10 (d, J = 16.0 Hz, 1H), 7.22 (d, J = 16.0 Hz, 1H), 7.12–
7.62 (m, 9H). MS (EI) m/z 238 (M+).
2,6-Di(p-methoxybenzylidene)cyclohexanone.
A
yellow
solid; mp 203–204 8C (lit2e 203–204 8C). IR (KBr) n 3020,
2924, 1657, 1604, 1570, 1271, 1142, 770, 692 cmꢁ1. 1H NMR
(300 MHz, TMS, CDCl3) d 1.80–1.83 (m, 2H), 2.94 (t,
J = 6.0 Hz, 4H), 3.86 (s, 6H), 6.94–7.40 (m, 8H), 7.77 (s, 2H).
MS (EI) m/z 333 (M+).
40-Nitrochalcone. Ayellow solid; mp 151–153 8C (lit2b 151–
152 8C). IR (KBr) n 3010, 2896, 1705, 1680, 1643, 1470, 921,
845 cmꢁ1 1H NMR (300 MHz, TMS, CDCl3) d 6.32 (d,
.
J = 16.1 Hz, 1H), 7.36 (d, J = 16.1 Hz, 1H), 7.15–7.36 (m, 5H),
7.52–8.26 (m, 4H). MS (EI) m/z 253 (M+).
2,6-Di(p-nitrobenzylidene)cyclohexanone. A russety solid;
mp 158–160 8C (lit2e 159 8C). IR (KBr) n 3082, 2925, 1663,
1606, 1576, 1525, 1346, 807 cmꢁ1. 1H NMR (300 MHz, TMS,
CDCl3) d 1.84–1.90 (m, 2H), 2.97 (t, J = 5.6 Hz, 4H), 7.60–8.22
(m, 8H), 8.32 (s, 2H). MS (EI) m/z 363 (M+).
4-Chlorochalcone. A yellow solid; mp 114–115 8C (lit2b
114–117 8C). IR (KBr) n 3086, 2910, 1780, 1712, 1650, 1207,
1
914, 746 cmꢁ1. H NMR (300 MHz, TMS, CDCl3) d 6.20 (d,
J = 16.0 Hz, 1H), 7.12 (d, J = 16.0 Hz, 1H), 6.22 (d, 2H), 7.10–
7.32 (m, 4H), 7.38–8.01 (m, 5H). MS (EI) m/z 244 (M+ + 2),
242 (M+).
2,6-Dicinnamylidenecyclohexanone. A yellowish solid; mp
179 8C (lit2e 180 8C). IR (KBr) n 3028, 2920, 1653, 1610, 1540,
4-Methylchalcone. Ayellowish solid; mp 98–99 8C (lit2b 97–
98 8C). IR(KBr)n 3213, 2914, 1760, 1698, 1650, 1090, 942, 850,
1
1180,737, 690 cmꢁ1. H NMR (300 MHz, TMS, CDCl3) d
1
1.96–2.16 (m, 2H), 2.86 (t, J = 6.4 Hz, 4H), 6.60 (d,
J = 16.2 Hz, 2H), 6.83 (d, J = 16.2 Hz, 2H), 6.86–7.42 (m,
10H), 7.72 (s, 2H). MS (EI) m/z 325 (M+).
718 cmꢁ1. H NMR (300 MHz, TMS, CDCl3) d 2.33 (s, 3H),
6.01 (d, J = 16.4 Hz, 1H), 7.02 (d, J = 16.4 Hz, 1H), 7.01–7.32
(m, 4H), 7.36–7.82 (m, 5H). MS (EI) m/z 221 (M+).
4-Methoxychalcone. A russety solid; mp 75–76 8C (lit2b 75–
77 8C). IR (KBr) n 3302, 2986, 1830, 1725, 1660, 1187, 934,
2,6-Difurfurylidenecyclohexanone. A purple solid; mp 140–
142 8C (lit2e 140–141 8C). IR (KBr) n 3149, 2940, 1643, 1590,

W.-B. Yi, C. Cai / Journal of Fluorine Chemistry 126 (2005) 1553–1558
1557
1
820 cmꢁ1. H NMR (300 MHz, TMS, CDCl3) n 3.73 (s, 3H),
2.30 (s, 3H), 6.18 (m, J = 15.9 Hz, 1H), 7.16 (d, J = 15.9 Hz,
1H). MS (EI) m/z 111 (M+).
5.93 (d, J = 16.0 Hz, 1H), 6.88 (d, J = 16.0 Hz, 1H), 6.92–7.19
(m, 4H), 7.32–7.99 (m, 5H). MS (EI) m/z 238 (M+).
3-Methyl-3-hexen-2-one. A colorless liquid (lit2b); IR
(CHCl3) n 1789, 1641, 1601, 1472, 1319, 1178, 920, 820,
4-Nitrochalcone. A brown solid; mp 158–160 8C (lit2b 158–
160 8C). IR (KBr) n 3236, 2910, 1870, 1675, 1660, 1470, 918,
1
783 cmꢁ1. H NMR (300 MHz, TMS, CDCl3) d 1.04 (t, 3H),
840 cmꢁ1
.
1H NMR (300 MHz, TMS, CDCl3) d 6.34 (d,
1.93 (s, 3H), 2.04 (m, 2H), 2.35 (s, 3H), 6.5 (m, 2H). MS (EI) m/
z 111 (M+).
J = 16.1 Hz, 1H), 7.39 (d, J = 16.1 Hz, 1H), 7.35–7.66 (m, 3H),
7.72–8.34 (m, 4H). MS (EI) m/z 252 (M+).
3-Methyl-3-hepten-2-one. A colorless liquid (lit2b); IR
(CHCl3) n 1802, 1765, 1641, 1439, 1310, 1238, 918, 823,
763 cmꢁ1. 1H NMR (300 MHz, TMS, CDCl3) d 0.92–1.41 (m,
5H), 1.87 (s, 3H), 1.96 (m, 2H), 2.28 (s, 3H), 6.52 (m, H). MS
(EI) m/z 125 (M+).
Cinnamylideneacetophenone. A yellow solid; mp 103–
104 8C (lit2a 104–105 8C). IR (KBr) n 3112, 3001, 2950, 1875,
1746, 1634, 1180, 940, 829 cmꢁ1. H NMR (300 MHz, TMS,
1
CDCl3) d 6.28 (d, J = 15.9 Hz, 1H), 7.12 (d, J = 15.9 Hz, 1H),
7.05–7.24 (m, 5H), 6.84 (d, J = 15.4 Hz, 1H), 7.76 (d,
J = 15.4 Hz, 1H), 7.45–7.83 (m, 5H). MS (EI) m/z 233
(M+).
Acknowledgements
We thank the National Defence Committee of Science and
Technology (40406020103) for financial support. We also
thank the Zhen-Ya Rare Earth Co. Ltd. for providing several
kinds of rare earth oxides.
1-Phenyl-4-methyl-2-penten-1-one.
A yellowish liquid
(lit2b); IR (CHCl3) n 1780, 1674, 1652, 1480, 927, 840,
1
762 cmꢁ1. H NMR (300 MHz, TMS, CDCl3) d 1.15 (d, 6H),
1.70 (m, 1H), 6.08 (t, J = 15.5 Hz, 1H), 6.76 (d, J = 15.5 Hz,
1H), 7.32–7.86 (m, 5H). MS (EI) m/z 173 (M+).
Benzylideneacetone. A yellowish solid; mp 40–41 8C (lit2b
41–42 8C). IR (KBr) n 3108, 2960, 1835, 1720, 1664, 1180,
References
1
943, 817 cmꢁ1. H NMR (300 MHz, TMS, CDCl3) d 2.39 (s,
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