Aldol Condensations on Solid Catalysts: A Cooperative Effect between Weak Acid and Base Sites

Article abstract of DOI:10.1002/1615-4169(200212)344:10<1090::AID-ADSC1090>3.0.CO;2-X

An amorphous aluminophosphate (ALPO) catalyst containing weak acid and base centers can carry out the aldol condensation of heptanal with benzaldehyde at much higher rates and selectivities than conventional solid acid (amorphous or crystalline aluminosil

Full text of DOI:10.1002/1615-4169(200212)344:10<1090::AID-ADSC1090>3.0.CO;2-X

FULL PAPERS
Aldol Condensations on Solid Catalysts: A Cooperative Effect
between Weak Acid and Base Sites
¬
M. J. Climent, A. Corma,* V. Fornes, R. Guil-Lopez, S. Iborra
¬
Instituto de TecnologÌa Quimica (UPV-CSIC), Universidad Politecnica de Valencia, Avda. de los Naranjos s/n,
46022 Valencia, Spain
Phone: (+34)-96-3877-800, Fax: (+34)-96-3877-809, e-mail: acorma@itq.upv.es
Received: April 30, 2002; Accepted: September 9, 2002
Dedicated to Prof. R. A. Sheldon on the occasion of his 60th birthday.
Abstract: An amorphous aluminophosphate (ALPO) attack of the enolate heptanal intermediate generated
catalyst containing weak acid and base centers can on the basic sites. With this type of bifunctional acid-
carry out the aldol condensation of heptanal with base catalyst, compounds with weak basicities are
benzaldehyde at much higher rates and selectivities already able to undergo the reaction with a much
than conventional solid acid (amorphous or crystal- higher selectivity than those obtained on stronger
line aluminosilicates) or base catalysts (MgO, hydro- acid or base catalysts.
talcites, KF/Al2O3, nitrurated ALPO). With the weak
acid-base catalyst, the reaction occurs through a
bifunctional acid-base mechanism that involves the Keywords: aldol condensation; aluminophosphates;
activation of benzaldehyde, by protonation-polariza- bifunctional acid-base catalysts; MgO; solid catalysts
tion of the carbonyl group on the acid sites, and the for fine chemicals; synthesis of jasminaldehyde
Introduction
by using a high benzaldehyde/heptanal molar ratio or/
and by adding slowly the heptanal into the reaction
Jasminaldehyde, a-n-amylcinnamaldehyde (3), is a tra- mixture.
ditional perfumery product with a violet scent which can
The tendency in recent years is to develop environ-
be obtained by the aldol condensation of heptanal with mentally friendly solid catalysts for the production of
benzaldehyde (Scheme 1). Its synthesis is traditionally fine chemicals. The use of insoluble catalysts in organic
carried out using sodium or potassium hydroxide as synthesis allows the recycling and handling of the
basic catalyst, heptanal being added slowly to the catalyst, so that the overall process is more efficient.[2]
reaction mixture at moderate temperatures.[1]
Different solid base catalysts have been reported for
During the synthesis of 3, different by-products which the synthesis of jasminaldehyde. Among them, the most
reduce the yield of amylcinnamic aldehyde can be interesting are anionic exchange resins,[3] potassium
formed. The most important undesired product comes carbonate in the presence of a solid-liquid phase transfer
from the self-condensation of heptanal to form 2-n- catalyst,[4] and solid-liquid phase transfer catalyst in dry
pentyl-2-n-nonenal (4) (Scheme 1). The formation of media under microwave irradiation.[5] It is known that
4 can be inhibited, to some extent, by maintaining a the condensation of heptanal and benzaldehyde can also
very low concentration of heptanal relative to benzal- be carried out in the presence of solid acid catalysts.
dehyde in the reaction mixture. This can be achieved Indeed, in a previous work[6] we have tested the activity
and selectivity of different acid molecular sieve cata-
lysts, and found that mesoporous (MCM-41) material
gave better results than microporous aluminosilicates.
O
Ph-CHO
+
H
These results were attributed to the confinement effects
of the reactants and products inside the voids of the
microporous materials, which lead to the preferential
formation of the self-condensation product as well as to
a fast deactivation of the catalyst.
Here, we show that it is possible to carry out very
effectively this reaction with solid catalysts containing
both weak acid and weak basic sites [aluminum
2
1
Ph
O
CHO
H
4
3
Scheme 1. Condensation of benzaldehyde with heptanal.
1090
¹ 2002 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1615-4150/02/34410-1090 1096 $ 17.50-.50/0
Adv. Synth. Catal. 2002, 344, No. 10

Aldol Condensations on Solid Catalysts
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phosphate (ALPO)]. It will be shown that, when the and yields of 3 after 8 h reaction time are summarized.
number of acid sites of the aluminum phosphate is As can be observed there, the order of activity of the
systematically reduced while increasing the number and catalysts is KF-Al2O3 > MgO > NaCsX which follows
strength of the basic ones (nitrurated aluminum the order of the basicity of the solids. It appears then that
phosphate, ALPON),[7,8] both activity and selectivity on these catalysts the basic sites are responsible for the
decrease. It will be shown that the bifunctional system is reaction to occur, following the mechanism described
able to perform the synthesis of jasminaldehyde at much above. However, these catalysts do not exhibit high
higher rates than either acid (silicates) or basic (MgO, selectivities to jasminaldehyde (3), the selectivity to this
KF/Al2O3, ALPON) catalysts. The results show the compound being especially low in the case of MgO. With
possibility for designing bifunctional acid-base catalysts this catalyst the self-condensation of heptanal (4) is
which can replace the use of stronger solid bases, highly favored, while the Michael addition reaction (5)
avoiding the associated problems of stability towards also takes place albeit to a much lower extent (Figure 1
water and CO2.
and Table 1).
When comparing the selectivity results obtained with
MgO and NaCsX zeolite one can think, in a first
approximation, that the higher selectivity of MgO to 4
and 5 should be due to the stronger basicity of MgO
Results and Discussion
In a previous work, it was found[6] that AlPO which is able to carry out the more difficult heptanal
(amorphous aluminophosphate) was more active and self-condensation and Michael addition.[7] In our opin-
selective than other more acidic solids, such as zeolites ion, while this is a realistic assumption and basic strength
and mesoporous aluminosilicates, for producing jasmin- certainly has an important influence on the selectivities
aldehyde from the condensation of benzaldehyde and
heptanal. Since these results were difficult to explain
from the point of view of an acid mechanism, the
following hypothesis was introduced: the superior
behavior of amorphous aluminum phosphate over
other more acid catalysts could be due to a combined
acid-base catalyzed condensation where the weak acid
sites of ALPO are interacting with the carbonyl group of
benzaldehyde producing a polarization of this group,
and as a consequence increasing the positive charge on
the corresponding carbon atom. This should favor the
attack of the enolate heptanal intermediate formed on
the relatively weak Lewis basic sites associated to
bridged oxygens. This hypothesis would be consistent
with the observation that in homogeneous base-cata-
lyzed condensations of alkanals with benzaldehyde, the
selectivity to a-alkylcinnamaldehydes can be increased
by the presence of a small amount of an acid.[9]
Figure 1. Conversion versus time plot for reaction of benzal-
dehyde (50 mmol) and heptanal (10 mmol) in the presence of
&
*
MgO (10 wt %) at 398 K: 2 (Â), 3 ( ),4 (o), 5 ( ).
In order to verify or reject this hypothesis we have
worked here from another starting point. Indeed, the
condensation of benzaldehyde with heptanal can also be
catalyzed by bases since the commercial process uses
NaOH or KOH as catalyst. The mechanism of the
reaction catalyzed by basic sites would involve the
formation of the anion of heptanal followed by its attack
to the carbonyl group of benzaldehyde.
Thus a series of basic catalysts with increasing
basicities, i.e., NaCsX zeolite <MgO <KF-Al2O3 was
tested here and in all cases (E)-amylcinnamaldehyde (3)
and (E)-2-n-pentyl-2-n-nonenal (4) were produced.
Moreover, with the most basic catalysts (KF-alumina
and MgO) a by-product (5) was detected in the reaction
mixture, the structure of which was assigned by mass
spectroscopy to a compound coming from the Michael
addition of heptanal to 4. In Table 1 the initial rates for
the disappearance of heptanal as well as the selectivity,
Table 1. Results of the condensation of benzaldehyde with
heptanal in the presence of different solid base catalysts.
Catalysts
ro 103 [mol
minÀ1 gÀ1]
Selectiv-
Yield [%][b]
ity[a] to 3
3
4
5
NaCsX[c]
MgO[d]
KF/Al2O3
ALPO
0.1
3.3
3.9
3.2
60
52
66
85
27
50
5
43
25
13
5
3
50
83[e]
[a]
Selectivity at 90% of conversion of heptanal.
8 h reaction time, using 10 wt % of catalyst at 398 K.
[b]
[c]
The maximum conversion achieved was 45% and 13% of
heptanoic acid was detected.
MgO was activated before reaction by heating the solid at
723 K under nitrogen atmosphere during 9 h.
3 h reaction time.
[d]
[e]
Adv. Synth. Catal. 2002, 344, 1090 1096
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M. J. Climent et al.
(1)
–PNH2 + H2O
FULL PAPERS
obtained, this cannot be the only variable and some
other factors should also play an important role for
controlling the selectivity of these catalysts. Indeed,
–POH + NH3
while KF/Al2O3 has stronger basicity than MgO, it gives Indeed, by IR spectroscopy we can see (Figure 2) that
nevertheless a higher selectivity to a-n-amylcinnamal- the intensity of the hydroxy band at 3670 cmÀ1 which is
dehyde (3) and lower selectivities to products 4 and 5 associated to P-OH groups decreases upon NH3 treat-
than MgO. It appears to us that adsorption effects may ment while the intensity of an IR band at 1559 cmÀ1
also play an important role on selectivities by favoring associated to the presence of P-NH2 groups increases
the relative adsorption of heptanal in the case of MgO. (Table 2). This observation clearly indicates that we are
In any case, it can be seen that the selectivity to 3 progressively reducing the number of weak Brˆnsted
obtained with any of these basic catalysts is much lower acid sites (P-OH), while increasing the number of the
than with ALPO (Table 1). Thus, we have to conclude basic sites (P-NH2). The acidity and basicity of these
that neither purely acidic or basic catalysts are more samples were studied by means of two test reactions, i.e.,
active and selective than ALPO.
acetalization of benzaldehyde with trimethyl orthofor-
At this point, we thought of starting from ALPO and mate (TMOF) and Knoevenagel condensation of
by a high temperature treatment in the presence of NH3, benzaldehyde with ethyl cyanoacetate, which are
to react hydroxy groups bonded to phosphorus (P-OH) exclusively catalyzed by acid and base sites, respective-
with NH3. This reaction should convert the acid P-OH ly. Furthermore, these two reactions can already take
into basic P-NH2 groups as indicated in Equation 1, place on weak acid and base sites.
leading to an amorphous aluminophosphate oxynitride
(ALPON).
The results for the acid-catalyzed acetalization
showed that, as was predicted from the IR results, the
Figure 2. IR spectra of ALPON samples with different nitrogen contents after vacuum treatment at 473 K for 2 h. (a) ALPO;
(b) ALPON-1; (c) ALPON-2; (d) ALPON-4.
Table 2. Intensity of the IR bands assigned to ÀPOH and ÀNH2 groups as function of N content of the sample and initial
rates obtained in the test reactions.
Catalysts
N (wt %)
ÀNH2
ÀPOH
Acetalization[a] ro
Knoevenagel[b] ro
[mmol minÀ1 gÀ1] 104
[mmol minÀ1 gÀ1] 104
ALPO
0.29
0.18
0.06
0.04
0.01
18.00
2.75
2.20
1.70
0.82
2.00
2.50
5.61
11.00
10.10
ALPON-1
ALPON-2
ALPON-3
ALPON-4
1.3
6
9.4
13.7
0.11
0.28
0.60
0.50
Reaction conditions:
[a]
Benzaldehyde (10 mmol), TMOF (25 mmol), catalyst (360 mg) at reflux temperature of tetrachloromethane (15 mL).
Benzaldehyde (10 mmol), ethyl cyanoacetate (10 mmol), 5 wt % of catalyst at 333 K.
[b]
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Aldol Condensations on Solid Catalysts
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Table 4. Condensation of benzaldehyde with heptanal on
acidity of the samples decreases when increasing the N
content of the catalyst, and consequently when decreas-
ing the number of P-OH groups. Meanwhile, the activity
for the base-catalyzed reaction (Knoevenagel conden-
sation) increases when increasing the nitrogen content
and consequently when increasing the number of basic
sites ( NH2). It should be remarked that ALPO also
shows activity as base catalyst through weak basic sites
(bridged oxygens).
In other words, the characterization and catalytic
results of these samples indicate that by the NH3
treatment we are converting a bifunctional catalyst
such asALPO, containing both weak acid and basic sites,
into a more and more basic catalyst.
different catalyst.[a]
Catalysts
Yield of
3 [%]
Yield of
4 [%]
Others
[%][b]
Selectiv-
ity to 3 [%]
ALPO
SAPO
SAM
83
70
52
13
18
32
86
74
55
6
10
[a]
Reaction conditions: 3 h reaction time, molar ratio benzal-
dehyde/heptanal ˆ 5, 10 wt % of catalysts at 398 K.
Phenylheptene and heptanoic acid were detected.
[b]
Thus, when the above samples were used for produc-
The nitrurated ALPO samples were tested for the ing jasminaldehyde (Table 4), we can see that SAPO are
production of jasminaldehyde and the results are given active since they are acid catalysts but, nevertheless,
in Table 3. It can be seen there that a reduction of the neither their activity nor their selectivity is higher than
acid sites of ALPO by NH3 treatment causes first a that of the amorphous aluminum phosphate in which
decrease of activity, followed by an increase of activity weak acid and base sites coexist.
for samples with nitrogen content ꢀ 9.4 wt %. Never-
From all the above, we have to conclude that
theless, it is evident that the selectivity to the desired jasminaldehyde can be formed via three different
product (3) decreases, while the n-heptanal self-con- mechanisms.
densation increases when decreasing the number of acid
POH groups, and at the same time as the number of
purely basic sites is increased. These results strongly Catalysis by Acid Sites
support the hypothesis that catalysts with weak acid and
base sites are better than catalysts containing only acid In this mechanism the carbonyl group of the benzalde-
or base sites irrespective of whether they are weak or hyde should be preferentially protonated and the enolic
strong.
form of the heptanal attacks the activated benzalde-
It would also be interesting to proceed now from the hyde.
amorphous aluminum phosphate to silicon aluminum
When benzaldehyde is adsorbed on ALPO and SAM
phosphates (SAPO) with different Si:Al:P ratios. In this samples, we can detectby IRspectroscopy (Figure 3) the
case, by increasing the silicon content we should presence of a band ꢁ 1690 cmÀ1 corresponding to the
increase the acidity of the material while decreasing its carbonylgroup ofthe free aldehyde (adsorbed in excess)
basicity, the amorphous silica alumina (SAM) being the while a second band appearing at 1654 cmÀ1 in ALPO
most acid material. Indeed, the results obtained with the and 1634 cmÀ1 in SAM must be assigned to the carbonyl
acid (acetalization) and base (Knoevenagel condensa- groups interacting with acid centers. The observed shift
tion) test reactions showed that the order of catalyst towards low wavenumbers indicates that SAM possess
acidity was: SAM > SAPO > ALPO, whereas the order stronger acid sites than ALPO.
of basicity was: ALPO > SAPO > SAM.
Heptanal can also be protonated by Brˆnsted acid
sites, however taking into account that the protonated
species formed are less stable than in the case of
benzaldehyde, and that benzaldehyde is used in excess
with respect to heptanal (benzaldehyde/heptanal molar
ratio ˆ 5), we have to expect that the surface population
of activated benzaldehyde was larger than that of
heptanal. This leads to a lower selectivity to the self-
condensation of heptanal when using acid than when
using base catalysts (see Tables 5 and 1).
Table 3. Results obtained in the condensation of benzalde-
hyde with heptanal in the presence of aluminophosphates
with different percentages of nitrogen content.
Catalysts
N
ro (103) [mol Selectiv- Yield[b] [%]
[%] minÀ1 gÀ1]
ity to 3[a]
3
4
5
ALPO
0
3.2
85
83
78
74
70
85
75
76
74
70
13
15
13
17
23
ALPON-1 1.3 2.8
ALPON-2 6.0 2.7
ALPON-3 9.4 3.9
ALPON-4 13.7 3.0
1
8
8
6
Catalysis by Basic Sites
In this case proton extraction from the a-carbon of the
heptanal by the basic sites occurs generating a carbanion
species which will attack the carbonyl group of the
benzaldehyde.
[a]
Selectivity at 90% of heptanal conversion.
At 8 h reaction time, using 10 wt % of catalyst at 398 K.
[b]
Adv. Synth. Catal. 2002, 344, 1090 1096
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M. J. Climent et al.
FULL PAPERS
Figure 3. IR spectra of benzaldehyde adsorbed on ALPO and SAM.
Table 5. Results obtained in the condensation of benzaldehyde and heptanal (molar ratio 5: 1) with different acid catalysts
(10 wt %) at 398 K.
Catalysts
Reaction
Time [h]
Conversion
of 2 [%]
Poison in the
Catalyst [%][a]
Selecti-
vity to 3
Yields [%]
3
4
Others[b]
H-Beta
6
16
10
3
93[b]
53
99
5.1
7.4
À
21
52
56
86
20
28
56
83
40
15
35
13
28
3
8
À
HY-100
AlMCM-41
ALPO
96
1.5
[a]
Determined by TG analysis and based on mole of heptanal retained.
Phenylheptene and heptanoic acid were also detected.
[b]
Catalysis by Cooperative Acid and Base Sites
carbon-oxygen bond and increasing the density of
positive charge on the carbon supporting the carbonyl
A third mechanism which involves acid and base sites is group. This makes this carbon more susceptible to be
consistent with the results obtained in this work, and is attacked by the carbanion of the heptanal formed by
operative in the case of amorphous ALPO (Scheme 2). interaction of this molecule with the basic oxygen sites
In this mechanism a weak Brˆnsted acid site (P-OH) of the ALPO. This bifunctional mechanism is effective
will interact with the carbonyl group polarizing the from a conversion point of view showing that it should
Scheme 2. Acid-base catalyzed condensation mechanism of benzaldehyde with heptanal.
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Aldol Condensations on Solid Catalysts
FULL PAPERS
zeolite (13X) at room temperature using an aqueous solution
of CsCl (0.5 M). The BET surface area of the resultant catalyst
was 650 m2 gÀ1. An MgO sample was prepared following the
procedure previously reported[11] and its BETsurface area was
246 m2 gÀ1.
be possible, in some cases, to replace stronger bases by
other catalysts which have lower basicities and acid sites
strong enough to activate one of the reactants. Whenthis
mechanism works, it gives good selectivities to the cross-
condensation, specially in those cases in where the
molecule to be attacked by the carbanion can be
preferentially activated by the acid sites of the catalyst,
as it occurs in the case of jasminaldehyde.
The KF/Al2O3 sample with 40 wt % of KF was purchased
from Aldrich.
Beta zeolite (Si/Al ˆ 13) was supplied by PQ corporation in
the acidic form.
The HY-100 zeolite (where the number indicates the
‡
‡
percentage of Na to NH4 exchange) was prepared by
stirring a commercial NaY sample (SK-40, Union Carbide,
Si/Al ˆ 2.5) with different aqueous solutions of ammonium
acetate followed by calcination at 823 K.[12] Al-MCM-41 (Si/
Al ˆ 15) with a pore diameter of 3.5 nm, was prepared
following the procedure given in ref.[13]
Amorphous SAPO sample with an SiO2 content of 10% was
prepared starting from an aqueous solution of H3PO4, AlCl3
and tetraethyl orthosilicate (TEOS) acidified with nitric acid at
pH <0. A hydrogel with of typical composition: 1.0 P2O5: 1.0
Al2O3: 0.6 SiO2, was then formed by adding concentrated
ammonia solution until a pH of 6. After 1 h the solvent was
filtered off and the hydrogel washed with distilled water. The
solid was dried at 393 K for 16 h and calcined at 773 K. The
BETsurface was 210 m 2 gÀ1.
Conclusions
It has been shown that the use of purely acid or purely
basic catalysts for the condensation of benzaldehyde
and heptanal leads to lower selectivities to jasminalde-
hyde than solid catalysts bearing an acid-base bifunc-
tional character, such as the exhibited by the amorphous
aluminum phosphate (ALPO).
The role of the weak acid sites is the activation of
benzaldehyde by interaction with the carbonyl group
favoring then the attack of the enolate heptanal
intermediate generated on the relatively weak basic
sites of ALPO. Indeed, it has been shown that by a high
temperature treatment of the ALPO in the presence of
NH3 acid sites are systematically reduced while increas-
ing the number and strength of the basic ones. This
change in the nature and distribution of active sites of
the catalyst causes a decrease in the selectivity to
jasminaldehyde. In an analogous way, introduction of Si
in the aluminum phosphate produces silico-alumino-
phosphates in which the acid-base character is shifted
towards higher acidities causing again a decrease in the
selectivity to jasminaldehyde.
Amorphous silica alumina (SAM) with a Si/Al ratio of 50,
with a very narrow pore distribution at ꢁ 1.5 nm, and with a
surface area of 719 m2 gÀ1 was prepared according to the
procedure reported by Bellusi et al.[14]
Elemental analyses of the pure as-synthesized ALPON's
were carried out by using a CHNS analyzer (Fisons EA 1108).
Infrared measurements were performed with a Nicolet 710
FTspectrophotometer using self-supporting wafers of
10 mg cmÀ2 and a Pyrex vacuum IR cell. Prior to the collection
of spectra the samples were heated in the cell for 2 h at
increasing temperatures, after which the spectra were obtained
at room temperature. IR spectra of the adsorbed benzaldehyde
were obtained by the following procedure: catalyst samples
were prepared as thin self-supported wafers and they were
heated for 16 h at 673 K under vacuum (10À5 torr) to remove
any adsorbed water. Benzaldehyde was then admitted at room
temperature and, after saturation, the aldehyde excess was
removed from the samples at 10À5 torr, and the IR-spectra
were recorded at room temperature.
Experimental Section
Materials
The amorphous aluminum phosphate (ALPO) with a P/Al
ratio of 1.0 and surface area of 211 m2 gÀ1 was prepared
following the method proposed by Lindblad et al.[10] To reduce
the acid sites while increasing the basicity, nitridation of the
aluminophosphate was performed under an ammonia flow at
the conditions indicated in Table 6.
N2 and Ar adsorption/desorption isotherms were performed
at 77 and 87.3 K, respectively, in an ASAP 2010 apparatus from
Micromeritics, after pre-treating the samples under vacuum at
673 K overnight and the specific surface area were obtained
using the BETmethodology.
The following materials have been used as basic catalysts.
The XNaCs zeolite was prepared by repeated exchange of NaX
Table 6. Main characteristics of the oxynitride samples.
Catalysts
N
[wt %]
Nitridation
Time [h]
NH3 flow rate
[ml minÀ1]
Nitridation
Temperature [K]
SBET
[m2 gÀ1]
ALPO
210
210
205
207
141
ALPON-1
ALPON-2
ALPON-3
ALPON-4
1.3
6.0
9.4
24
16
16
16
150
50
150
150
773
1073
1073
1123
13.7
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M. J. Climent et al.
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ˆ
ˆ
-CH2-CCHO CH-), 2.21 (m, 2H, -CH2-CH CCHO-); MS:
m/z ˆ 210 (M , 98), 153 (30), 139 (34), 125 (41), 41 (100).
Reaction Procedure: Condensation of Benzaldehyde
and Heptanal
‡
3-Hexyl-2,5-dipentylpentanedial (5): MS: m/z ˆ 324
‡
All reactions were carried out under nitrogen atmosphere, in a
flask that was fitted with a reflux condenser. The flask was
immersed in a thermostatted silicone oil bath and the reaction
mixture was magnetically stirred. A mixture of previously
distilled benzaldehyde (50 mmol) and heptanal (10 mmol) was
placed in the flask. Once the mixture reached a temperature of
398 K, a specific calculated quantity of the catalyst was added
such that the final wt/wt ratio of catalyst versus the total sum of
reagents was 10%. Zeolites (HY and HBeta) and AlMCM-41
catalysts were activatedbefore reaction at323 Kunder vacuum
(1 torr) for 3 h. Samples of the reaction mixture were periodi-
cally withdrawn with a filtering syringe and analyzed by gas
chromatography (GC) (Hewlett-Packard 5990A spectrometer
provided with a 25-m capillary column of cross-linked 5%
phenylmethylsilicone).
(M , 5), 295 (43), 266 (10), 252 (100), 177 (10), 41 (35).
Acknowledgements
¬
The authors acknowledged financial support by the Direccion
General de Investigacion CientÌfica y Tecnica of Spain (Project
MAT2000-1392).
¬
¬
References
[1] a) Farbenindustrie, I. G., D. R. P. 284,458, 1927; b) L. S.
Payne, E. P. 0 392 579 A2, 1990.
Quantitative determinations were based on the measured
response factors of the reactants and reaction products.
Reaction products were identified by H NMR spectroscopy
(Varian VXR À 400 S, 400 MHz) and GC-mass spectrometry
(Hewlett-Packard 5988A mass spectrometer connected with a
25-m capillary column of phenylmethylsilicone).
[2] H. Hattori, Chem. Rev. 1995, 95, 537.
[3] P. Mastagli, G. Durr, Bull. Soc. Chim. France 1955, 268.
[4] A. Sarkar, P. K. Dey, K. Datta, Indian J. Chem. 1986,
25B, 656.
[5] D. Abenhaim, C. P. Ngoc Son, A. Loupy, N. Ba Hiep,
Synthetic Commun. 1994, 24, 1199.
1
Yield for jasminaldehyde (3) was defined as the mmole
formed of this product divided by the initial mmole of the
limiting reactant (heptanal). Yield for 2-pentyl-2-nonenal (4)
was defined as the mmole formed of this product multiplied by
two (according the 2:1 stoichiometry for formation of 4) and
then divided by the initial mmole of heptanal. Selectivity to
jasminaldehyde (3) was defined as the mmole of this
compound divided by the total mmole of heptanal converted.
[6] M. J. Climent, A. Corma, H. Garcia, R. Guil-Lopez, S.
¬
Iborra, V. Fornes, J. Catal. 2001, 197, 385.
¬
[7] M. J. Climent, A. Corma, V. Fornes, A. Frau, R. Guil-
Lopez, S. Iborra, J. Primo, J. Catal. 1996, 163, 392.
[8] M. J. Climent, A. Corma, R. Guil-Lopez, S. Iborra, J.
Primo, Catalysis Lett. 1999, 59, 33.
[9] A. Kuiterman, A. M. C. F. Castelijns, H. J. A. Dielemans,
R. Green, EP 0771 780 A1, 1997.
[10] T. Lindblad, B. Rebenstorf, Y. Zhi-Guang, S. Lars, T.
Anderson, Appl. Catal. A 1994, 112, 187.
[11] P. Putanov, E. Kis, G. Boskovic, Appl. Catal. 1991, 73, 17.
[12] A. Corma, M. J. Climent, H. GarcÌa, J. Primo, Appl.
Catal. 1989, 51, 113.
[13] C. T. Kresge, M. E. Leonowicz, W. J. Roth, J. C. Vartulli,
J. S. Beck, Nature 1992, 359, 710.
[14] G. Bellusi, C. Perego, A. Carati, S. Peratello, E. Previde
Massara, G. Perego, Stud. Surf. Sci. Catal. 1994, 84, 85.
Spectroscopic Data of the Reaction Products
(E)-a-Amylcinnamaldehyde (3): 1H-NMR: d ˆ 9.54 (s, 1H,
ˆ
-CHO), 7.20 (s, 1H, Ph-CH CCHO-), 2.52 (tt, 2H, -CH2-
C CH-Ph), 1.50 [m, 2H, -CH2-CH2-(CH2)2-CH3], 1.34 [m, 4H,
ˆ
‡
-CH2-(CH2)2-CH3], 0.89 (m, 3H, -CH3); MS: m/z ˆ 202 (M ,
12), 145 (9), 129 (48), 115 (100), 105 (28), 91 (14).
(E)-2-Pentyl-2-nonenaldehyde (4): 1H-NMR: d ˆ 9.36 (s,
ˆ
1H, -CHO), 6.44 (t, 1H, -CH2-CH CCHO-), 2.34 (m, 2H,
1096
Adv. Synth. Catal. 2002, 344, 1090 1096