Highly efficient and selective synthesis of (E)-α,β-unsaturated ketones by crossed condensation of ketones and aldehydes catalyzed by an air-stable cationic organobismuth perfluorooctanesulfonate

Article abstract of DOI:10.1002/adsc.200900679

An air-stable cationic organobismuth perfluorooctanesulfonate possessing both acidic and basic characters was synthesized, and showed high catalytic activity, diastereoselectivity, stability, and reusability in the one-pot synthesis of (E)-α,β-unsaturated ketones through highly selective crossed condensation of ketones and aldehydes in water.

Full text of DOI:10.1002/adsc.200900679

FULL PAPERS
DOI: 10.1002/adsc.200900679
Highly Efficient and Selective Synthesis of (E)-a,b-Unsaturated
Ketones by Crossed Condensation of Ketones and Aldehydes
Catalyzed by an Air-Stable Cationic Organobismuth
Perfluorooctanesulfonate
Renhua Qiu,a Yimiao Qiu,a Shuangfeng Yin,a,* Xinhua Xu,a Shenglian Luo,a
Chak-Tong Au,a,b Wai-Yeung Wong,c and Shigeru Shimadad,*
a
College of Chemistry and Chemical Engineering, Hunan University, Changsha 410081, Peopleꢀs Republic of China
Fax : (+86)-731-8882-1310; e-mail: sfyin73@yahoo.com.cn
Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong, Peopleꢀs Republic of China
Department of Chemistry and Centre for Advanced Luminescence Materials, Hong Kong Baptist University, Kowloon
b
c
Tong, Hong Kong, Peopleꢀs Republic of China
National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi Tsukuba,
d
Ibaraki 305-8565, Japan
Fax : (+81) 29-861-4588; e-mail: s-shimada@aist.go.jp
Received: September 29, 2009; Published online: December 30, 2009
Abstract: An air-stable cationic organobismuth per- turated ketones through highly selective crossed con-
fluorooctanesulfonate possessing both acidic and densation of ketones and aldehydes in water.
basic characters was synthesized, and showed high
catalytic activity, diastereoselectivity, stability, and Keywords: crossed condensation; diastereoselectiv-
reusability in the one-pot synthesis of (E)-a,b-unsa- ity; organobismuth compounds; perfluorooctanesul-
fonates; (E)-a,b-unsaturated ketones
Introduction
synthesis, the compounds can be applied in biochem-
istry as well.[10] The aldol condensation reaction of
It is known that bismuth is a stable heavy element carbonyl compounds is the most common process for
that is free of toxicity.[1] The utilization of bismuth the synthesis of a,b-unsaturated carbonyl compounds
compounds in the field of catalysis and organic syn- (Scheme 1).[11] The Claisen–Schmidt condensation, a
thesis has been studied intensively in recent years.[1,2] crossed aldol condensation of an aromatic aldehyde
Simple bismuth Lewis acids such as bismuth halides and an aliphatic ketone or aldehyde under basic con-
and triflates are highly efficient catalysts in a number ditions, is the traditionally used process. In this reac-
of reactions.[2] The use of designed cationic organobis- tion, a relatively strong base (such as metal hydroxide
muth compounds in catalysis, however, is rarely re- or metal alkoxide) is employed, and selective mono-
À
ported partly due to the instability of the Bi C condensation is often difficult due to side reactions
bond.[3] We have been working on the synthesis of bis- such as bis-condensation and aliphatic aldehyde dime-
muth compounds and their applications in organic rization. Application of the method is further limited
synthesis.[4] Very recently, we reported an organobis- because substrates with base-sensitive functional
muth perchlorate that shows high catalytic efficiency groups are not suitable. A better approach is by
in the direct diastereoselective Mannich reaction.[4d] means of the Mukaiyama-aldol reaction followed by
Herein we report the excellent catalytic activity of an- subsequent dehydration catalyzed by a Lewis acid.[12]
other novel related air-stable cationic organobis
(III) compound for the stereoselective synthesis of lective synthesis of a,b-unsaturated ketones from al-
(E)-a,b-unsaturated ketones in water. kenyl trichloroacetates and aldehydes; in this ap-
ACHTUNGTRENmNUGN uth- Recently, Yanagisawa et al. reported the one-pot se-
ACHTUNGTRENNUNG
a,b-Unsaturated carbonyl compounds are widely proach, ketones have to be converted to alkenyl tri-
used as substrates for a number of reactions such as chloroacetates before the condensation reaction.[13]
hydrogenation,[5] epoxidation,[6] peroxidation,[7] cyclo-
The catalytic direct crossed condensation of ke-
addition,[8] and conjugate addition.[9] Besides organic tones and aldehydes would be an ideal process for the
Adv. Synth. Catal. 2010, 352, 153 – 162
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Renhua Qiu et al.
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Scheme 1. A comparison between a common process and an ideal process for the selective synthesis of a,b-unsaturated ke-
tones.
synthesis of a,b-unsaturated carbonyl compounds, be- atom of the coordinating water occupies a vacant site
cause there is no need to prepare reactive intermedi- of the cationic bismuth center, making the coordina-
ates (e.g., silyl enol ethers) and only H2O is generated tion geometry an equatorially distorted, vacant trigo-
as a side-product (Scheme 1). Such a process is signifi- nal bipyramid with the sulfur and the oxygen atoms
cantly “energy efficient” and “atom economic” since in the apical positions and the two carbon atoms in
À
multistep transformations and separation of product the equatorial positions. The Bi S(1) distance [2.704
(from by-products) are not necessary. Recently, the (2) ꢂ] is shorter than that (2.845 ꢂ) of precursor
use of organocatalysts for direct crossed condensation 2,[15b] clearly showing the stronger sulfur-to-bismuth
À
reactions was reported, whereby a high catalyst load- coordination in 1. The Bi O(1) distance [2.445 (7) ꢂ]
ing is necessary (20 mol%).[14] In this paper, we de- is longer than that of covalent Bi O bonds (e.g., Bi
scribe an alternative, highly efficient catalyst system O bond distances of monomeric diorganobismuth alk-
À
À
using the organobismuth compound [S
(CH2C6H4)2Bi- oxides range 2.15–2.20 ꢂ),[4b,17] indicating that the
ACHTUNGTRENNUNG
A
weakly coordinated water molecule can be replaced
by another substrate.
The thermal behaviour of compound 1 was investi-
gated by TG-DSC in an N2 atmosphere (Figure 2).
The TG-DSC curves show three stages of weight loss.
Results and Discussion
Shown in Scheme 2 is the synthetic route for the The endothermic step below 1508C can be assigned
organobismuth compound 1. Treatment of to the removal of H2O molecules. The material is
(CH2C6H4)2BiCl (2)[15] with AgOSO2C8F17 in THF stable up to about 2508C. The weight loss of an exo-
[16]
SACHTUNGTRENNUNG
afforded the organobismuth perfluorooctanesulfonate thermic nature at 2508C is plausibly due to the oxida-
1 quantitatively. 1H NMR and elemental analyses tion of organic entities. It is estimated from the TG
show that the sample freshly obtained after recrystal- analysis result that the empirical formula of the com-
(OH2)]+
lization contains one water molecule. We found that plex can be written as [SACHTUNTRGENNUG(CH2C6H4)2BiACHUTNGTRENNUGN
compound 1 is air-stable; it remained under ambient [C8F17SO3]À (1).
environment as dry colorless crystals or white powder
We employed the Hammett indicator method to
for more than one year. The crystal structure of 1 was determine the acidity and basicity of 1, and found
confirmed by X-ray analysis. An ORTEP representa- that it has relatively weak acidity with strength of
tion of 1, and selected bond lengths and angles are 3.3<Ho ꢀ4.8 and weak basicity with a strength of
shown in Figure 1. It is clear that the organobismuth 7.2ꢀH- <8.9.[16] With the accessible bismuth center
component in compound 1 is a cation. The oxygen acting as a Lewis acid site and the uncoordinated
Scheme 2. Synthesis of cationic organobismuth compound 1.
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Highly Efficient and Selective Synthesis of (E)-a,b-Unsaturated Ketones
À
À
Figure 1. ORTEP view (50% probability level) of 1. Selected bond lengths (ꢂ) and angles (deg): Bi C(1), 2.240(8); Bi
C(8), 2.236(8); Bi O(1), 2.445(7); Bi S(1), 2.704(2); S(1) C(7), 1.787(10); S(1) C(14), 1.795(10); C(1) Bi C(8), 100.6(3);
À
À
À
À
À À
À
À
À
À
À
À
À
À
À
À
C(8) Bi O(1), 84.7(3); C(1) Bi O(1), 89.4(3); C(8) Bi S(1), 77.3(3); O(1) Bi S(1), 155.42(19); C(7) S(1) C(14),
100.9(5).
Figure 2. TG-DSC curves of compound 1.
Figure 3. ORTEP view of crystal structure of (S*)-2-[(R*)-
lone-pair electrons of sulfur as a Lewis base, it is ex-
phenyl(phenylamino)methyl]cyclohexanone.
pected that 1 can act as a bifunctional Lewis acid/base
catalyst.[18]
We first investigated the catalytic performance of 1
Table 1 shows the structural effect of amines on this
towards the direct three-component Mannich reaction reaction. Primary amines with n-alkyl groups are
of benzaldehyde, cyclohexanone and aniline in water, highly active (Table 1, entries 1–4, 85–95%), with the
and observed the formation of Mannich adducts bulkier primary amines showing lower efficiency
{(S*)-2-[(R*)-phenyl(phenylamino)methyl]cyclohexa-
(Table 1, entries 5 and 6). In the cases of secondary
none} with high diastereoselectivity (anti/syn> 99/1) and tertiary amines (Table 1, entries 7 and 8) or in the
(Figure 3).[4d] However, when propylamine was used absence of amine (Table 1, entry 9), there is no de-
instead of aniline, a completely different product, the tectable reactivity whatsoever. It is clear that the
(E)-a,b-unsaturated ketone, was obtained. Since this presence of a primary amine is indispensable for the
process was efficient under mild conditions, we fur- occurrence of the reaction.
ther evaluated the catalytic performance of 1 towards
the synthesis of a,b-unsaturated ketones.
The reaction occurs smoothly in CH2Cl2 and
MeOH, but rather slowly in THF, Et2O, and hexane
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Table 1. Synthesis of a,b-unsaturated ketones using various
To show the uniqueness of 1, we compared the cat-
aliphatic amines.[a]
alytic activity of 1 with those of S
the cationic organobismuth compounds [t-BuN-
(CH2C6H4)2Bi]+[B(C6F5)4]À (3),[3] [S
(CH2C6H4)2Bi-
(OH2)] (OSO2CF3)3 (5), Bu2Sn-
+A[ClO4]À (4),[4d] Bi
ACHTUNGNERT(NGNU CH2C6H4)2BiCl (2),
G
R
A
ACHTUNGTRENNUNG
C
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
(OMe)2 (6),[13a] DIMCARB (N,N-dimethylammonium
N’’,N’’-dimethylcarbamate) (7),[19] NaOH (8), NaOMe
(9), and C8F17SO3H (10). As shown in Table 3, catalyst
1 is superior to the other nine catalysts in terms of
product yield and stereoselectivity.
Various aromatic aldehydes with electron-donating
and electron-withdrawing groups as well as enolizable
aliphatic aldehydes were employed to test the versa-
tility of the catalytic system (Table 4). In all cases of
benzaldehydes, the desired products were obtained in
high yields. One can also see that the aldehydes with
an electron-withdrawing group on the phenyl ring ex-
hibit higher activity than the aldehydes with an elec-
tron-donating group (Table 4, entries 2–5). The reac-
tion of cinnamaldehyde can occur at 08C (Table 4,
entry 6), while the E-selectivity for cinnamaldehyde is
the lowest. It is worth noting that the reaction of eno-
lizable aliphatic aldehydes selectively produces (E)-
a,b-unsaturated ketones in quantitative yields without
Entry
RNH2
Yield [%][b]
E/Z[c]
1
2
3
4
5
6
7
8
9
EtNH2
88
95
93
85
71
21
>99/1
>99/1
>99/1
>99/1
>99/1
>99/1
–
n-PrNH2
n-BuNH2
n-HexNH2
CyNH2
t-BuNH2
Et2NH
NR[d]
NR[d]
NR[d]
Et3N
No amine
–
–
[a]
PhCHO, 1.0 mmol; aliphatic amine, 1.0 mmol; cyclohexa-
none, 1.2 mmol; 1, 0.02 mmol; H2O, 2.0 mL; room tem-
perature, 3 h.
Isolated yield.
Determined by H NMR.
[b]
[c]
[d]
1
No reaction.
Table 3. Synthesis of a,b-unsaturated ketones over different
catalysts.[a]
Table 2. Synthesis of a,b-unsaturated ketones in various sol-
vents.[a]
Entry Cat.
Yield E/Z[c]
[%][b]
Entry
Solvent
Time [h]
Yield [%][b]
E/Z[c]
1
[S
(1)
(CH2C6H4)2BiCl (2)
[t-BuN
(CH2C6H4)2Bi]+[B
[S(CH2C6H4)2Bi(OH2)]
+A[ClO4]À (4)
Bi(OSO2CF3)3 (5)
Bu2Sn(OMe)2 (6)
DIMCARB (7)
NaOH (8)
NaOMe (9)
G
G
>99/
1
1
2
3
4
5
6
7
n-Hexane
CH2Cl2
Et2O
CH3CN
THF
12
6
8
7
8
67
85
78
85
76
93
95
>99/1
>99/1
>99/1
>99/1
>99/1
>99/1
>99/1
2
3
4
5
6
7
S
A
G
43/57
64/36
93/7
86/14
78/22
79/21
81/19
82/18
–
CH3OH
H2O
6
3
8[d]
9[d]
10
[a]
PhCHO, 1.0 mmol; n-PrNH2, 1.0 mmol; cyclohexanone,
1.2 mmol; 1, 0.02 mmol; solvent, 2.0 mL; room tempera-
C8F17SO3H (10)
ture.
Isolated yield.
Determined by H NMR.
[b]
[c]
[a]
PhCHO, 1.0 mmol; n-PrNH2, 1.0 mmol; cyclohexanone,
1.2 mmol; Cat., 0.02 mmol; H2O, 2.0 mL; room tempera-
1
ture, 3 h.
Isolated yield.
Determined by H NMR.
[b]
[c]
[d]
1
(Table 2). Especially, the efficiency is high when
water is used as a solvent (yield, 95%, E/Z>99/1). It
is apparent that the E-selectivity is independent of
the employed solvents.
Side
product
is
2-[hydroxyACHTNGUTERNNU(G phenyl)methyl]cyclo-
AHCTUNGTRENNhGUN exanone.
GC yield.
[e]
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Highly Efficient and Selective Synthesis of (E)-a,b-Unsaturated Ketones
Table 4. Synthesis of a,b-unsaturated ketones using various
Table 5. Synthesis of a,b-unsaturated ketones using various
aldehydes.[a]
ketones and malonates.[a]
Entry Ketone
Product
(E)
Yield E/Z[c]
[%][b]
1
95
97
96
84
>99/1
>99/1
>99/1
>99/1
2
Entry
RCHO
Yield [%][b]
E/Z[c]
1
2
3
4
5
6
7
8
PhCHO
95
90
88
96
99
83
97
99
>99/1
97/3
97/3
98/2
99/1
93/7
99/1
99/1
3[d]
p-CH3C6H4CHO
p-CH3OC6H4CHO
p-ClC6H4CHO
p-CF3C6H4CHO
(E)-Ph-CH=CHCHO
PhCH2CH2CHO
nC7H15CHO
4[e]
d)
5
6
96
95
94
–
–
–
[a]
RCHO, 1.0 mmol; n-PrNH2, 1.0 mmol; cyclohexanone,
1.2 mmol; 1, 0.02 mmol; H2O, 2.0 mL; room temperature,
3 h.
[b]
[c]
[d]
Isolated yield.
Determined by H NMR.
1
08C.
7
the formation of aldehyde self-condensation products
or any other side-products (Table 4, entries 7 and 8).
Table 5 summarizes the results of the reaction be-
tween benzaldehyde and various ketones or malo-
nates. Both the cyclic and acyclic ketones selectively
produce (E)-a,b-unsaturated ketones in high yields
(Table 5, entries 1–4); the active methylene com-
pounds are efficient substrates as well. Using the
adopted method, we obtained almost quantitative
yields of the desired products when pentane-2,4-
[a]
PhCHO, 1.0 mmol; n-PrNH2, 1.0 mmol; ketone,
1.2 mmol; 1, 0.02 mmol; H2O, 2.0 mL; room temperature,
3 h.
[b]
[c]
[d]
[e]
Isolated yield.
Determined by H NMR.
1
08C to room temperature.
24 h.
dione, dimethyl and diethyl malonates were used can efficiently proceed with only 10 mol% of amine
(Table 5, entries 5–7). (Scheme 3). Although further study is necessary to
To test the reusability of 1, the catalyst was subject clarify the reaction mechanism, the results mentioned
to cycles of benzaldehyde, propylamine or cyclohexa- so far suggest that the reaction probably takes place
none reaction (Table 6). We observed that within a through a Mannich-type mechanism as shown in
test of 7 cycles, there was almost no change in product Scheme 4. The formation of imines from an aldehyde
yield (94–95%) and stereoselectivity (E/Z>99/1). and an amine can proceed without a catalyst, while
Moreover, we have analyzed the structural integrity compound 1 probably has a positive effect on the
of the recycled catalyst by NMR techniques and imine formation. It is worth noting that the E/Z-selec-
found that the structure of the recycled catalyst is tivity of the current reaction very well corresponds to
consistent with that of the freshly prepared catalyst. the anti/syn-selectivity of the Mannich reaction using
In other words, the catalyst is very stable and suitable PhNH2 instead of n-PrNH2, which we recently report-
for reuse.
ed (for 1, >99:1 vs. >99:1; for 2, 43:57 vs. 57:43; for
The fact that the reaction only proceeds with pri- 3, 64:36 vs. 64:36; for 4, 93:7 vs. 95:5; for 5, 86:14 vs.
mary amines suggests that the formation of imine (its 86:14).[4d] This result strongly suggests that the change
presence in the reaction mixture was confirmed) is es- of amines does not affect the diastereoselectivity of
sential. We envisaged that the amine is regenerated in the Mannich adducts, and that the final product is
the final step, and only a catalytic amount of amine formed through stereospecific syn-elimination from
would be enough. Indeed we found that the reaction the intermediate Mannich adduct, as shown in (I).
Adv. Synth. Catal. 2010, 352, 153 – 162
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FULL PAPERS
Table 6. The reusability of catalyst 1 in the synthesis of a,b-
unsaturated ketones.[a]
Cycle
Yield of recovered
Cat. [%]
Yield of product
[%][b]
E/Z[c]
1
2
3
4
5
6
7
99
96
97
96
95
94
92
95
95
94
95
94
95
94
>99/1
>99/1
>99/1
>99/1
>99/1
>99/1
>99/1
[a]
PhCHO, 1.0 mmol; n-PrNH2, 1.0 mmol; cyclohexanone,
1.2 mmol; Cat., 0.02 mmol; H2O 2.0 mL; room tempera-
ture, 3 h.
Isolated yield.
Determined by H NMR.
Scheme 4. A plausible catalytic cycle for the crossed-con-
densation reaction of ketones and aldehydes catalyzed by 1
in the presence of n-PrNH2.
[b]
[c]
1
The structures of the cationic parts of catalysts 1 (and teristics. The compound shows high catalytic activity,
4) and 3 are relatively similar. However, the stereose- stereoselectivity, stability, and reusability for the syn-
lectivity of the reaction was very different. This result thesis of (E)-a,b-unsaturated ketones by the direct
would suggest the importance of the sulfur atom in 1. crossed condensation of aldehydes and ketones. We
As mentioned above, the sulfur atom in 1 can act as a found that the new procedure works effectively with
weak Lewis base, and the high stereoselectivity may aromatic as well as enolizable aliphatic aldehydes. It
be explained if the addition reaction step proceeds is expected that the compound 1 will find broad appli-
through a transition state like (II) in which both the cations in organic synthesis.
Lewis acid and the Lewis base parts of 1 act simulta-
neously to gather two reacting substrates in a chair-
type cyclohexane arrangement with less steric repul-
sion.
Experimental Section
General
All chemicals were purchased from Aldrich. Co., Ltd. as
well as other chemical providers and used as received unless
Conclusions
otherwise indicated. [S
ACHTUNGTRENNUNG
[C8F17SO3]À (1), was prepared ac-
In conclusion, we have synthesized and characterized
an organobismuth perfluorooctanesulfonate 1, which
is air-stable and exhibits both acidic and basic charac-
[S(CH2C6H4)2Bi(OH2)] CHTUNGTRENNNUG
A
U
cording to the procedure described in the literature.[15] The
catalytic reactions were carried out under air in water. The
NMR spectra were recorded at 258C over an INOVA-400M
Scheme 3. Effect of the amount of n-PrNH2 on product yield.
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Highly Efficient and Selective Synthesis of (E)-a,b-Unsaturated Ketones
(Varian) instrument calibrated using tetramethylsilane
(TMS) as an internal standard. Elemental analysis was per-
formed with a VARIO EL III (Elementar). The single-crys-
tal X-ray diffraction analysis on 1 was performed in Shang-
hai Institute of Organic Chemistry, Chinese Academy of Sci-
ences with a SMART-APEX instrument. The TG-DSC anal-
ysis was performed on a NETZSCH-STA-449C (operation
conditions: N2, 58C/min heating rate). Melting points were
determined with an XT-4 micro melting point apparatus
(Beijing Tech Instrument Co., Ltd.). The acidity was mea-
sured by the Hammett indicator method.[16] The employed
indicators included crystal violet (pKa =0.8), dimethyl
yellow (pKa =3.3), methyl red (pKa =4.8), neutral red
(pKa =6.8), bromothymol blue (pKa =7.2), and thymol blue
(pKa =8.9). Acid/base strength was expressed by the Ham-
mett acidity function (H0) and the Hammett basicity func-
tion (HÀ), respectively, which was scaled by the pKa value of
the indicators.
H2O (2.0 mL). Then the mixture was stirred for 3 h as moni-
tored by TLC analysis until PhCHO as well as the inter-
mediate imine obtained from PhCHO and n-PrNH2 were
consumed completely. Then the mixture was extracted with
Et2O (10 mLꢃ3), and the combined organic layer was
evaporated under vacuum. The resulting residue was subject
to column chromatography on silica gel (200–300 meshes)
(petroleum ether/ethyl acetate=5/1, v/v); yield: 177 mg
(95% based on PhCHO). All the products were character-
1
ized by comparison of H and 13C NMR spectral data as re-
ported.[20]
(E)-2-Benzylidenecyclohexanone
(Table 4,
entry 1):
1H NMR (400 MHz, CDCl3, 258C, TMS): d=1.77–1.78 (m,
2H, CH2), 1.92–1.94 (m, 2H, CH2), 2.54 (t, 3JH,H =6.8 Hz,
2H, CH2), 2.84–2.85 (m, 2H), 7.32–7.35 (m, 1H, ArH),
4
7.36–7.40 (m, 4H, ArH), 7.50 (t, JH,H =2.4 Hz, 1H, ArCH);
13C NMR (100 MHz, CDCl3, 258C, TMS): d=23.40, 23.87,
28.92, 40.33, 128.31, 128.50, 130.27, 135.56, 136.66, 201.78.
(E)-2-(4-Methylbenzylidene)cyclohexanone
(Table 4,
1
entry 2): H NMR (400 MHz, CDCl3, 258, TMS): d=1.75–
1.78 (m, 2H, CH2), 1.91–1.94 (m, 2H, CH2), 2.37 (s, 3H,
CH3), 2.51–2.55 (t, 3JH,H =6.8 Hz, 2H, CH2), 2.82–2.86 (m,
Preparation of [S
(1)
(OH2)]+ [C8F17SO3]À
ACHTUNGTRENNUNG(CH2C6H4)2BiACHUTNGTRENNUGN
3
2H, CH2), 7.18–7.20 (d, JH,H =8.0 Hz, 2H, ArH), 7.30–7.33
To a solution of S
THF (20 mL), a solution of AgOSO2C8F17
ACHTUGNTERNN(NUG CH2C6H4)2BiCl (0.456 g, 1.0 mmol) in
[16a]
3
(d, JH,H =8.4 Hz, 2H, ArH), 7.49 (1H, s, ArCH); 13C NMR
(0.607 g,
(100 MHz, CDCl3, 258C, TMS): d=21.38, 23.36, 23.89,
29.00, 40.28, 129.11, 130.45, 132.82, 135.83, 138.81, 159.98,
202.11.
1.0 mmol) in THF (10 mL) was added. After the mixture
had been stirred in the dark at room temperature for 3 h, it
was subject to filtration under air. The filtrate was then
mixed with hexane (1.0 mL), and after 24 h, colorless crys-
tals formed; yield: 927 mg (99%); mp 188–1898C. Crystals
suitable for X-ray diffraction analysis were obtained by re-
(E)-2-(4-Methoxybenzylidene)cyclohexanone
entry 3): H NMR (400 MHz, CDCl3, 258C, TMS): d=1.65–
1.73 (m, 2H, CH2), 1.79–1.87 (m, 2H, CH2), 2.44 (t, JH,H
(Table 4,
1
3
=
crystallization of 1 from THF/hexane solution. 1H NMR
6.7 Hz, 2H, CH2), 2.76 (m, 2H, CH2), 3.75 (s, 3H, -OCH3),
3
3
3
(400 MHz, acetone-d6, 258C, TMS): d=8.29 (d, 2H, JH,H
=
6.83 (d, JH,H =8.8 Hz, 2H, ArH), 7.31 (d, JH,H =8.8 Hz, 2H,
ArH), 7.41 (t, 4JH,H =2.1 Hz, 1H, Ar-CH=C); 13C NMR
(100 MHz, CDCl3, 258C, TMS): d=23.20, 23.92, 28.68,
40.31, 55.46, 114.09, 128.9, 132.40, 134.51, 136.64, 160.11,
201.92.
3
7.6 Hz, ArH), 7.86 (d, 2H, JH,H =8.0 Hz, ArH), 7.58 (t, 2H,
3JH,H =6.8, 7.2 Hz, ArH), 7.46 (t, 2H, 3JH,H =6.8, 7.2 Hz,
ArH), 5.15 (d, 2H, 2JH,H =15.6 Hz, ArCH2), 4.85 (d, 2H,
2JH,H =16.4 Hz, ArCH2), 2.99 (s, 2H, H2O); 13C NMR
(100 MHz, acetone-d6, 258C, TMS): d=45.53, 128.72,
130.98, 132.64 (2C), 138.19, 153.62, 206.06 (C8F17SO3);
19F NMR (376 MHz, acetone-d6, 258C): d=À121.18 (b, 2F,
3JF,F =15.79 Hz, -CF2-), À117.72 (s, 2F, -CF2-), À116.88 [s,
4F, -(CF2)2-], À116.56 (s, 2F, -CF2-), À115.32 (s, 2F, -CF2-),
(E)-2-(4-Chlorobenzylidene)cyclohexanone
entry 4): H NMR (400 MHz, CDCl3, 258C, TMS): d=1.61–
1.69 (m, 2H, CH2), 1.77–1.85 (m, 2H, CH2); 2.42 (t, JH,H
(Table 4,
1
3
=
6.8 Hz, 2H, CH2), 2.68 (m, 2H, CH2), 7.19–7.25 (m, 4H,
ArH), 7.32 (t, 4JH,H =2.2 Hz, 1H, Ar-CH=C); 13C NMR
(100 MHz, CDCl3, 258C, TMS): d=23.23, 23.74, 28.85,
40.20, 128.53, 131.47, 134.02, 134.34, 137.07, 201.08.
3
3
À109.15 (t, 2F, JF,F =14.29 Hz, -CF2-), À76.04 (t, 3F, JF,F
=
10.90 Hz, CF3-); elemental analysis calcd. (%) for
C22H14BiF17O4S2: C 28.16, H 1.50, S 6.83; found: C 28.19, H
1.49, S 6.82.
(E)-2-[4-(Trifluoromethyl)benzylidene]cyclohexanone
1
(Table 4, entry 5): H NMR (400 MHz, CDCl3, 258C, TMS):
3
3
Crystal data for 1: C22H14BiF17O4S2; M=938.43; monoclin-
ic; space group P21/c; a=24.7673 (17) ꢂ, b=11.7803 (8) ꢂ,
c=10.0588 (7) ꢂ; b=97.8420(10) deg; V=2907.4 (3) ꢂ3;
T=293(2) K; Z=4; reflections collected/unique, 15666/
5693, Rint =0.089; final R indices [I>2s(I)], R1 =0.0518,
wR2 =0.1352; R indices (all data), R1 =0.0693, wR2 =0.1287.
GOF=0.940. CCDC 733233 (1) contains the supplementary
crystallographic data for this paper. These data can be ob-
tained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
d=1.80 (t, JH,H =6.8 Hz, 2H, CH2), 1.96 (t, JH,H =9.6 Hz,
2H, CH2), 2.56 (t, 3JH,H =6.8 Hz, 2H, CH2), 2.82 (t, 2H,
3JH,H =6.4 Hz, CH2), 7.52 (d, JH,H =8.0 Hz, 2H, ArH), 7.64
3
(d, 3JH,H =8.0 Hz, 2H, ArH), 7.88 (s, 1H, ArCH=);
13C NMR (100 MHz, CDCl3, 258C, TMS): d=23.30, 23.87,
28.93, 40.32, 124.09, 129.11, 130.45, 132.92, 135.73, 138.82,
161.13, 200.98.
(E)-2-[(E)-3-Phenylallylidene]cyclohexanone
(Table 4,
1
entry 6): H NMR (400 MHz, CDCl3, 258C, TMS): d=1.77–
1.91 (m, 4H, CH2), 2.48 (t, 2H, 3JH,H =6.8 Hz), 2.74 (t,
3JH,H =6.0 Hz, 2H, CH2), 6.90–7.04 (m, 2H, ArH), 7.24–7.48
(m, 6H, ArH and olefinic-H); 13C NMR (100 MHz, CDCl3,
258C, TMS): d=23.20, 23.52, 27.12, 40.19, 123.24, 127.32,
128.88, 129.09, 135.12, 135.63, 136.77, 141.05, 200.92.
Typical Procedure for the Synthesis of (E)-a,b-Un-
saturated Ketones in Water Catalyzed by Catalyst 1
(E)-2-(3-Phenylpropylidene)cyclohexanone
entry 7): H NMR (400 MHz, CDCl3, 258C, TMS): d=1.68–
1.62 (m, 2H, CH2), 1.84–1.77 (m, 2H, CH2), 2.44–2.36 (m,
(Table 4,
To a 25-mL round-bottomed flask were added catalyst 1
(18 mg, 0.02 mmol), PhCHO (106 mg, 1.0 mmol), n-PrNH2
(59 mg, 1.0 mmol), cyclohexanone (117 mg, 1.2 mmol) and
1
Adv. Synth. Catal. 2010, 352, 153 – 162
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
159

Renhua Qiu et al.
FULL PAPERS
6H, -CH2-CH2Ph, CH2), 2.75 (t, 3JH,H =8.0 Hz, 2H, CH2),
mediate (E)-N-benzylidenepropan-1-amine obtained from
PhCHO and n-PrNH2 were consumed completely. The mix-
ture was extracted with CH2Cl2 and subject to evaporation
under vacuum. Then the residue was suspended in diethyl
ether, followed by filtration. After the filter cake of the cat-
alyst had been washed twice with ethyl ether, it was used for
catalyzing the next reaction cycle (Table 6). The combined
filtrate was evaporated under vacuum, and the product was
purified by column chromatography on silica gel (200–300
mesh) (petroleum ether/ethyl acetate=5/1, v/v).
3
6.65 (t, JH,H =2.8 Hz, 1H, CH=C), 7.21–7.16 (m, 3H, ArH),
7.28 (t, 3JH,H =7.2 Hz, 2H, ArH); 13C NMR (100 MHz,
CDCl3, 258C, TMS): d=23.51, 23.64, 26.82, 29.90, 34.83,
40.29, 126.26, 128.61, 137.04, 138.13, 138.06, 141.47, 201.42.
(E)-2-Octylidenecyclohexanone
1H NMR (400 MHz, CDCl3, 258C, TMS): d=0.88 (t, JH,H
6.0 Hz, 3H, CH3), 1.25–1.38 (m, 12H), 1.76–1.83 (m, 2H,
(Table 4,
entry 8):
3
=
3
CH2), 2.36–2.42 (m, 4H, C=CH-CH2, CH2), 2.76 (t, JH,H
=
8.4 Hz, 2H, CH2), 6.55 (t, 3JH,H =2.8 Hz, 1H, CH=C);
13C NMR (100 MHz, CDCl3, 25 8C, TMS): d=14.02, 22.68,
23.33, 23.64, 25.17, 26.68, 27.82, 28.5, 29.14, 31.81, 40.02,
135.93, 139.67, 200.79.
Crystal Data Refinements
Refinement of F2 against all reflections: the weighted R-
factor wR and goodness of fit S are based on F2, convention-
al R-factors R are based on F, with F set to zero for negative
F2. The threshold expression of F2 >2s(F2) is used only for
calculating R-factors(gt), etc. and is not relevant to the
choice of reflections for refinement. R-factors based on F2
are statistically about twice as large as those based on F, and
R-factors based on all data will be even larger. Hydrogen
site location: inferred from neighbouring sites, H atoms
treated by a mixture of independent and constrained refine-
ment. Data collection: Bruker SMART; cell refinement:
Bruker SMART; data reduction: Bruker SHELXTL; pro-
gram(s) used to solve structure: SHELXS97 (Sheldrick,
1990); program(s) used to refine structure: SHELXL97
(Sheldrick, 1997); molecular graphics: Bruker SHELXTL;
software used to prepare material for publication: Bruker
SHELXTL.
Crystal data for (S*)-2-[(R*)-phenyl(propylamino)me-
thyl]cyclohexanone: C19H21NO; M=279.37; monoclinic;
space group P21/n; a=24.7673(17) ꢂ, b=10.2965(7) ꢂ, b=
10.6213(7) ꢂ, c=14.1700(10) ꢂ; b=95.4070(10) deg; V=
1542.77(18) ꢂ3; T=293(2) K; Z=4; reflections collected/
unique, 3730/3235, Rint =0.016; final R indices [I>2s(I)],
R1 =0.0470, wR2 =0.1330; R indices (all data), R1 =0.0537,
wR2 =0.1420. GOF=0.940. CCDC 734040 contains the sup-
plementary crystallographic data for this compound. These
data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif.
(E)-2-Benzylidenecyclopentanone
(Table 5,
entry 2):
3
1H NMR (400 MHz, CDCl3, 258C, TMS): d=2.06 (t, JH,H
=
3
7.6 Hz, 2H, CH2), 2.44 (t, JH,H =8.0 Hz, 2H, CH2), 3.00 (t,
3JH,H =7.2 Hz, 2H, CH2), 7.30–7.48 (m, 4H, ArCH and
ArCH=C), 7.56–7.59 (m, 2H, ArH); 13C NMR (100 MHz,
CDCl3, 258C, TMS): d=20.20, 29.36, 37.79, 128.73, 128.36,
130.55, 132.42, 135.57, 136.12, 208.24.
(E)-4-Phenylbut-3-en-2-one (Table 5, entry 3): 1H NMR
(400 MHz, CDCl3, 258C, TMS): d=2.35 (s, 3H, CH3), 6.70
(d, 3JH,H =16.9 Hz, 1H, =CH-C=O), 7.39–7.35 (m, 3H,
ArH), 7.54–7.47 (m, 3H, ArH and Ar-CH=C); 13C NMR
(100 MHz, CDCl3, 258C, TMS): d=26.81, 128.70, 129.46,
130.62, 132.48, 139.31, 142.75, 197.72.
(E)-Chalcone (Table 5, entry 4): 1H NMR (400 MHz,
CDCl3, 258, TMS): d=7.40 (d, 3JH,H =6.8 Hz, 3H, ArH),
7.52 (t, 3JH,H =16.0 Hz, 1H, -CH-C=O), 7.55–7.60 (m, 2H,
1
ArH), 7.63–7.65 (m, 2H, ArH, ArH), 7.79 (d, JH,H
=
16.0 Hz, 1H, ArCH=C), 8.02 (d, 3J=7.0 Hz, 2H, ArH);
13C NMR (100 MHz, CDCl3, 258C, TMS): d=122.09, 128.45,
128.49, 128.60, 128.94, 130.51, 132.75, 134.90, 138.22, 144.73,
190.42.
3-Benzylidenepentane-2,4-dione
(Table 5,
entry 5):
1H NMR (400 MHz, CDCl3, 258C, TMS): d=2.24 (s, 3H,
CH3), 2.38 (s, 3H, CH3), 7.36 (m, 5H, ArH), 7.44 (s, 1H,
ArCH=C); 13C NMR (100 MHz, CDCl3, 258C, TMS): d=
26.22, 31.33, 128.71, 129.39, 130.41, 132.68, 139.62, 142.51,
196.47, 205.31.
Dimethyl 2-benzylidenemalonate (Table 5, entry 6):
1H NMR (400 MHz, CDCl3, 258C, TMS): d=3.84 (s, 3H,
CH3), 3.87 (s, 3H, CH3), 7.38–7.40 (m, 3H, ArH), 7.45 (t,
3
2H, JH,H =5.0 Hz, ArH), 7.77 (s, 1H, ArCH=C); 13C NMR
(100 MHz, CDCl3, 258C, TMS): d=60.92, 60.97, 126.32,
128.77, 129.41, 130.47, 132.89, 142.12, 164.12, 166.69.
Acknowledgements
Diethyl
2-benzylidenemalonate
(Table 5,
entry 7):
This work was financially supported by the National Science
Foundation of China (NSFC) (Grant Nos. 20873038 and
20973056), the National Outstanding Youth Foundation of
China (Grant No. E50725825), and the National 863 Pro-
gram of China (2009AA05Z319). C. T. Au thanks the Hunan
University for an adjunct professorship and the Hong Kong
Baptist University for a Faculty Research Grant (FRG/08-09/
II-09).
1H NMR (400 MHz, CDCl3, 258C, TMS): d=1.27–1.35 (m,
6H, 2CH3), 4.30 (m, 4H, 2CH2), 7.37–7.40 (m, 3H, ArH),
7.44–7.47(t, 2H, 3JH,H =4.8 Hz, ArH), 7.74 (s, 1H, CH);
13C NMR (100 MHz, CDCl3, 258C, TMS): d=13.86, 14.12,
61.62, 61.67, 126.30, 128.75, 129.42, 130.49, 132.88, 142.11,
164.11, 166.66.
Typical Procedure for the Synthesis of (E)-a,b-Un-
saturated Ketones Catalyzed by Recovered Catalyst 1
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