Indi an Journal of Chemistry
Vol. 38B, July 1999, pp. 857-858
Note
-
An efficient Knoevenagel condensation using
HZSM-5 zeolite as a catalyst
Majid M Heravi"* ', Mahmood Tajbakhsh",
acids employable without prior thermal and chemica l
treatment.
Preliminary experiments with HZSM-5 zeolite
[acid type zeolite with 40 SiO l / AI 20 1 molar rati o,
P f
pore sIze average 20A surface area (200± I m-/g] - or
the condensation of benzaldehyde with malononitrile
(Eqn X=H, R=CN, entry I) produced the desi red
olefin in 80% yield .
•
Bagher Moh ajerani' & Mitra Ghassemzadeh"
"Chemist ry & Chemical Engineering Research Center of Iran
P,O.Box 14335-186, Tehran, Iran
hDepartment of Chemistry, Mazandaran Uni versity, Babolsar, Iran
"Research Institute of Petroleum Industry of Iran
Received 10 December 1998; accepted (revised) 6 May 1999
Knoevenagel co ndensation is assisted by HZSM-5 zeolite
wherein variou s aromatic aldehydes react readily with
malononitril e and eth yl cyanoacetate to produce co rresponding
olefinic products.
The last few years have witnessed considerable
resurgence of interest in the area of zeolite induced
organic tran sformation ' . We have exploited the
catalytic potential of zeolites for various organic
synthetic tranformations such as, regioselecti ve
alkylation of heterocyc les 2" , preparation of carbonyl
compounds as acetals 4 , [n continuati on we wish to
report a mild, convenient and heterogeneous catalytic
methodology assisted Knoevenagel condensati on
using HZSM-S zeolite.
Knoeven age l
condensation
was
originally
performed in the presence of amines using other
bases 5, Lewi s ac ids ZnCh6, TiCIJ base?, solid support
catalysts such as A1 20 ,8, AIPO~-AI 20,9, clayslO and
modified Mg-All'.
HSZM-S zeolites are produced on large-scale by
Tosoh cooperation for the refinery and petrochemical
industry and thi s represents easily accessi ble so lid
Ent ry
2
3
4
5
6
7
8
0
.,
HZSM-S zeolite
--------.
CH,Q" rellux
g-'
c.../CN
C~
R
X
Subsequently, a systematic study of this reacti on to
establish the generality of the method has been
undertaken with various aldehydes and acti ve
methylene compounds utilizing HZSM-5 zeolite.
Aliphatic aldehydes did not give good res ults but
aromatic aldehydes bearing a va ri ety of functi onal
groups,
namely,
p-bromobenzaldehyde,
pnitrobenzaldehyde are reacted wit h meth ylene
compounds such as malononitril e and ethy l
cyanoacetate in the presence of HZSM-5 zeo lite.
These reactions lead to comp leti on in 5-6 hr in
refluxing CH2Cl 2 to produce the olefini c products in
70-80% yield (Table I) . The reaction conditi ons are
particularly mild and the work-up procedure is
exceed ingly simple and reduced to mere filtrat ion.
Moreover, we recycled the zeo lite for a furth er five
experiments obtaining the corresponding olefin ic
compounds with similar high yields. This result
indicated that HZSM-5 zeo lite is activated after th e
first cycle and can be therefore reused several ti mes
without losing activity .
Experimental Section
All products were known compounds and
Table I-The HZSM-5 zeolite ass isted Knoevenagel condensation
Yi eld
R
Period
(hr)
(%)
Benzaldehyde
CN
5
80
-doCOEt
6
75
p- B romobenzaldehyde
CN
70
5
-do6
71
C0 2 Et
p-Nitrobenzaldehyde
CN
6
70
' -do7
68
C0 2Et
Vanillin
CN
10
62
-do12
60
C02 Et
Aldehyde
Reactions carri ed ou t in di cho loromet hane under dry co ndition . Yields are based on isolated prod ucts.
mp
°C
tn ')
51 '1
164
12
%1 2
I Y/
1M;')
13 1('
IU
h
858
INDIAN J. CHEM. SEC S, JULY 1999
identified by comparison with authentic samp les (JR,
NMR , mp) .
A typical procedure. Benzaldehyde ( 1.06 g, 10
mmoles), malononitrile (0.66 g, 10 mmoles) and
HZSM-5 zeolite (0.52 g) were refluxed in dry
dichloromethane (20 mL) for 5hr. The reaction
mixture was filtered off and washed with CH 2Cb (10
mL) . The filtrate was evaporated to dryness and the
resulting crude product was directly subjected to
co lumn chromatography (hexane: EtOAc, 7:3) to
afford the pure olefinic product in 80% yield (mp
82-83 o C)12.
Acknowledgement
We thank Dr A R Garakani , Research Institute of
Petroleum Industry of Iran, for the supp ly of HZSM-5
zeolite. Research supported by the National Research
Council of Iran (NRCI) as a National Research
Proj ect under the grant
number 3708
IS
acknowledged.
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