Dolomite (CaMg(CO3)2) as a recyclable natural catalyst in Henry, Knoevenagel, and Michael reactions

Article abstract of DOI:10.1016/j.molcata.2012.08.027

Iranian dolomite (CaMg(CO₃)₂) which consists of double-layered carbonates with Ca²⁺ and Mg²⁺ ions was utilized as a heterogeneous base catalyst in the CC, CN, and CS bond forming reactions via the Henry, Knoevenagel, aza-Michael, and thia-Michael transformations under mild conditions in water. Iranian dolomite has been characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Brunauer Emmett Teller (BET) and XRF chemical analysis, while its basic strength was evaluated by following the Hammett indicators procedure. This water-insoluble natural catalyst demonstrated high activity and was reusable.

Full text of DOI:10.1016/j.molcata.2012.08.027

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Dolomite (CaMg(CO3)2) as a recyclable natural catalyst in Henry, Knoevenagel,
and Michael reactions
Fatemeh Tamaddon∗, Mohammad Tayefi, Elaheh Hosseini, Elham Zare
Department of Chemistry, Yazd University, Yazd 89195-741, Iran
a r t i c l e i n f o
a b s t r a c t
Iranian dolomite (CaMg(CO3)2) which consists of double-layered carbonates with Ca2+ and Mg2+ ions was
utilized as a heterogeneous base catalyst in the C C, C N, and C S bond forming reactions via the Henry,
Knoevenagel, aza-Michael, and thia-Michael transformations under mild conditions in water. Iranian
dolomite has been characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy
(FT-IR), Brunauer Emmett Teller (BET) and XRF chemical analysis, while its basic strength was evaluated
by following the Hammett indicators procedure. This water-insoluble natural catalyst demonstrated high
activity and was reusable.
Article history:
Received 3 April 2012
Received in revised form 28 August 2012
Accepted 29 August 2012
Available online xxx
Keywords:
Iranian dolomite
Natural catalyst
Heterogeneous base
Knoevenagel condensation
Henry reaction
© 2012 Published by Elsevier B.V.
Michael addition
1. Introduction
have considered this natural base catalyst for promotion of the C C,
C
N, and C S bond forming reactions in aqueous media.
Organic transformations can be made more profitable by use
of recoverable natural catalysts and water as the least hazardous
chemicals [1]. Therefore, catalytic researches have been recently
focused on the use of heterogeneous mineral catalysts such as
bentonite, kaolin, apatite, clays, and metal oxides [2–16]. These nat-
urally occurring catalysts efficiently catalyze the organic reactions
via adsorption of the starting materials and enhancement of their
reactivity. The extra advantages of these catalysts which make them
good candidates for green processes are availability, non-volatility,
stability, non-toxicity, reusability, and low cost.
Henry and Knoevenagel condensations [20–23] are two impor-
tant C C bond forming reactions that produce Michael acceptors
as key synthetic intermediates. Both reactions are routinely per-
formed via the base-catalyzed aldol-type addition of CH active to
carbonyl compounds along with the production of nitroalkanols
and electron-deficient alkenes [22–24]. Due to the serious com-
petition of aldol-condensation, Canizzaro and Nef-type reactions,
polymerization, and dehydration of nitroalkanols with Henry and
Knoevenagel reactions, several modifications have been developed
to increase their chemo- or regio-selectivity [24–29].
Dolomite (CaMg(CO3)2) is a very cheap water insoluble sedi-
mentary carbonate rock which consists of the Ca2+ and Mg2+ ions
with double-layered carbonates [17–19]. Although dolomite has
various structural characteristics, it is best known for its saddle-
shaped crystals that help to its high stability at ∼350 ◦C [18].
However, MgCO3 part of dolomite decomposes to CO2 and MgO at
350–545 ◦C, while decomposition of the CaCO3 fraction of dolomite
occurs at 825 ◦C. Thus calcined dolomite can be considered as a
composite mixture of MgO and CaO with higher base strength than
uncalcined dolomite with carbonate base. This heterogeneous cat-
alyst has been recently used in the production of biodiesels via
transesterification reaction of canola oil with methanol [19]. We
Aza- and thia-Michael additions are known synthetic tools for
the creation of C N and C S bonds via nucleophilic reaction of
amines and thiols with electron-deficient alkenes as Michael accep-
tors [30–35].
Due to the benefits of dolomite as a naturally occurring het-
erogeneous base catalyst, in continuation of our recent researches
[36–40], herein we report the use of dolomite as a new natural recy-
clable catalyst in the Henry, Knoevenagel, and Michael reactions in
water (Scheme 1).
2. Experimental
2.1. General
∗
Chemicals were commercially available and used without fur-
ther purification unless otherwise stated. The Iranian dolomite
Corresponding author. Tel.: +98 3518122666; fax: +98 3518210644.
E-mail address: ftamaddon@yazduni.ac.ir (F. Tamaddon).
1381-1169/$ – see front matter © 2012 Published by Elsevier B.V.
http://dx.doi.org/10.1016/j.molcata.2012.08.027
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O
completion of the reaction (TLC monitoring), ethyl acetate (10 mL)
was added and dolomite was removed by filtration. The product
was isolated after evaporation of the solvent.
The obtained nitroalkanols, alkenes, and Michael reaction prod-
ucts were known and characterized by comparison of their physical
or spectral data with the authentic samples or with those of
reported earlier.
OH
Dolomite, 40 oC
H2O/ PEG
CHR1NO2
H
CH2R1NO2
+
+
R
H
R
H
O
EWG
EWG
EWG
Dolomite
Ar
H
+
H2O, 40 oC
Ar
R1
EWG
Dolomite
H2O, r.t.
R1XR2
EWG
N
EWG
R2
2.6. Reusability of catalyst
R1, R2= H, alkyl, Ar
X = S, NH
EWG = NO2, COR, CN, COOR, CONH2
Dolomite was recovered from the reaction of nitromethane and
benzaldehyde after washing with ethyl acetate. Elemental anal-
ysis of the used catalyst was the same as preliminary dolomite
that show the stability of dolomite structure under reaction con-
ditions. Despite of the absorption of water by recycled dolomite
(very broad OH stretching of hydrated carbonate of dolomite at
2600–3600 cm−1 in the FT-IR spectrum), it was reused three times
in the same Henry reaction in water and no decreasing of the yields
was observed.
Similarly, the recycled dolomite from the Knoevenagel conden-
sation of malononitrile and benzaldehyde in water was used in
the second run of the reaction and no significant loss of activity
for the reused catalyst was observed. The filtered dolomite from
Michael-addition of aniline to nitrostyrene was also washed with
ethyl acetate and EtOH. After drying at ∼300 ◦C, the recycled cat-
alyst was used in the further runs but the yield of product was
reduced (>10% than the original catalyst) in the third run of reaction.
Scheme 1. Dolomite-catalyzed Henry, Knoevenagel, and Michael reactions.
with purity >98.5% was extracted from Tabas mine, by Kansaran
Binaloud Co., Ltd, located in Mashhad, Iran. 1H NMR and 13C NMR
spectra were recorded at 250 or 500 MHz and 62.9 or 125 MHz,
respectively. Chemical shifts are given in ppm with respect to inter-
nal TMS. IR measurements were performed on a Brucker FT-IR
spectrometer. Melting points are uncorrected. All products showed
the same physical, analytical, and spectral data with those reported
in the literature.
2.2. Characterization of catalyst
The extracted Iranian dolomite was finely grinded in an agate
mortar as a gray-white powder, washed with hot water, and
calcined at 300 ◦C for 3 h. The chemical composition of Iranian
dolomite was determined by XRF analysis and its structure was
confirmed by FT-IR spectroscopy and X-ray diffraction analysis
(purity > 98.5%). Basic strength and the surface area of the Iranian
dolomite was evaluated by following the Hammett indicator pro-
cedure and BET method, respectively.
2.7. Representative data for the selected compounds
2.7.1. 1-(2,4-Dichloro-phenyl)-2-nitro-ethanol (Table 3, entry
15)
Thick oil, 91% yield, FT-IR: ꢀmax (KBr) 3502, 1555 and 1381 cm−1
.
2.3. General experimental procedure for the Henry reaction
1H NMR (250 MHz, CDCl3) ı: 3.26 (br s, 1H, OH), 4.42 (dd, 1H,
J1 = 13.6, J2 = 9.4 Hz, CH2), 4.67 (dd, 1H, J1 = 13.6, J2 = 2.4 Hz, CH2),
5.79 (d, 1H, J = 9.4 Hz, CHOH), 7.24–7.48 (m, 2H), and 7.61 (d, 1H,
J = 8 Hz) ppm. 13C NMR (62.9 MHz, CDCl3) ı: 67.8, 79.4, 128.4, 129,
129.9, 132.5, 134.5, and 135.6 ppm. EIMS (probe) 70 eV, m/z: 235,
217, 188, 175, 147, 145, 46, 30, and 29.
A mixture of aldehyde (5 mmol), nitroalkane (10 mmol), and
dolomite (0.5 g, ∼2.5 mmol) in 50% polyethyleneglycol and water
(PEG-400/H2O (5 mL)) was stirred at ∼40 ◦C for the given times
(Tables 2 (entry 11) and 3). Progress of the reaction was followed
by TLC and after the completion of the reaction, EtOAc (50 mL)
was added and catalyst was filtered off. The filtrate was washed
with saturated aqueous NaHSO3 (for removing the remained alde-
hyde, if necessary) and dried over Na2SO4. The product was isolated
by evaporation of the solvent and purified in some cases by flash
chromatography (hexane:EtOAc, 80:20) to afford the pure product.
2.7.2. (E)-2-(4-chlorophenyl)-1-nitro-1-cyanoethene (Table 4,
entry 3) [41]
Pale orange powder, Mp = 115–116 ◦C. FT-IR: ꢀmax (KBr) 3053,
2943, 2230, 1615, 1590, 1548, 1426, 1330, 1220, 1067, 933, 947,
819, 771, and 621 cm−1 1H NMR (250 MHz, CDCl3): ı 7.50–8.00
.
2.4. General experimental procedure for the Knoevenagel
condensation
(m, 4H, Haromatic), and 8.64 (s, 1H, Hvinyl) ppm. 13C NMR (62.9 MHz,
CDCl3) ı: 111.0, 123.5, 126.5, 129.5, 133.0, 140.5, and 147.0 ppm.
To a mixture of activated methylene compound (2 mmol) and
dolomite (0.2 g) in H2O (3 mL) was added aldehyde (2 mmol) and
the mixture was stirred at ∼40 ◦C for elevated time (Table 4). After
totally consumption of aldehyde (TLC monitoring), the reaction
mixture was diluted with ethyl acetate and filtered to remove
dolomite. The filtrate was concentrated to give the tri-substituted
alkene products.
2.7.3. (E)-2-furyl-1-nitro-1-cyanoethene (Table 4, entry 12) [41]
Pale brown solid, Mp = 147–149 ◦C. FT-IR: ꢀmax (KBr) 3083, 2953,
2235, 1612, 1595, 1548, 1426, 1335, 1228, 1067, 950, 822, 775, and
651 cm−1. 1H NMR (250 MHz, CDCl3): ı 6.80–7.90 (m, 3H, Haromatic),
and 8.42 (s, 1H, Hvinyl) ppm. 13C NMR (62.5 MHz, CDCl3) ı: 111.5,
116.0, 120.0, 129.5, 133.5, 145.5, and 152.5 ppm.
2.5. General experimental procedure for the Michael-addition
reactions
2.7.4. 1,1-Dicyano-2-(pyridine-4-yl)ethylene (Table 4, entry 13)
White needles (EtOH:H2O), Mp = 100–101 ◦C. FT-IR: ꢀmax (KBr)
3023, 2933, 2233, 1610, 1590, 1548, 1416, 1403, 1236, 1219, 1067,
To a mixture of amine (or thiol) (2 mmol) and dolomite (0.2 g,
∼50 mol%) in water (2 mL) was added Michael-acceptors such as
nitrostyrene, acrylonitrile, methyl vinyl ketone, methyl methacry-
late, cyclohexenone, or acryl amide (2 mmol). The mixture was
stirred at room temperature for the given times (Table 5). After
933, 947, 819, 771, and 621 cm−1 1H NMR (500 MHz, CDCl3): ı 7.69
.
(d, J = 5.3 Hz, 2H, Haromatic), 7.83 (s, 1H, Hvinyl), and 8.88 (d, J = 5.3 Hz,
2H, Haromatic) ppm. 13C NMR (100 MHz, CDCl3) ı: 89.0, 111.7, 112.9,
123.0, 137.4, 151.9, and 158.0 ppm.
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Table 1
Table 2
Chemical analysis of Iranian dolomite.
Optimization of the Henry reaction of benzaldehyde with nitromethane.
O
Entry
Component
Percentage (%)
OH
o
CH2NO2
H
Base, 40 C
Solvent, 20h
1
2
3
4
Mg
Ca
CO3
21.16
30.64
46.71
1.49
CH3NO2
+
Ph
H
Ph
Entry
Base/solventa
Yield (%)b
Other components (Fe2O3,
SiO2, K2O, TiO2, Na2O, MnO,
Al2O3, P2O5)
1
2
ZnO/H2O
CaO/H2O
15
30c
75c
20
3
4
5
6
7
8
9
KF-Alumina/H2O
Amberlyst-A-29/H2O
Molecular sieves/H2O
Amberlyst-R-900/H2O
Et3N-SiO2/H2O
4-PVP/H2O
NaHCO3-Bentonite/H2O
Dolomite/H2O
15
2.7.5. 4-(Methylphenylamino)-butan-2-one (Table 5, entry 9)
[30]
15
75c
15
93% yield. FT-IR: ꢀmax (KBr) 3050, 2920, 1712 (C O) 1590, 1420,
1380, 680, and 750 cm−1 1H NMR (250 MHz, CDCl3): ı 2.30 (s, 3H,
.
75c
70
10
11
12
13
14
15
16
17
18
19
20
MeCO), 2.65 (t, 2H, CH2), 2.88 (s, 3H, MeN), 3.6 (t, 2H), 6.50–6.80
(m, 3H, Haromatic), and 7.12–7.24 (m, 2H, Haromatic) ppm. 13C NMR
(62.5 MHz, CDCl3) ı: 30.6, 38.5, 40.5, 47.3, 112.4, 116.5, 129.3, 148.6,
and 208.0 ppm.
Dolomite/H2O/PEG-400
Dolomite/EtOH
90
30c
15c
15c
60d
Dolomite/CH3CN
Dolomite/MeNO2 (Excess)
Dolomite/H2O/PEG-400
None/H2O/PEG-400
CaCO3/H2O/PEG-400
MgCO3/H2O/PEG-400
CaO/H2O/PEG-400
MgO/H2O/PEG-400
<10
2.7.6. 3-(4-Nitrophenylsulfanyl)-cyclohexanone (Table 5, entry
17) [31]
70c
75c
67c
70c
Yellow needles (EtOH:H2O), Mp = 70–71 ◦C. FT-IR: ꢀmax (KBr)
1715 (C O), 1505 and 1340 (NO2) cm−1 1H NMR (250 MHz,
.
a
CDCl3): ı 1.80–1.90 (m, 2H, CH2), 2.10–2.25 (m, 2H, CH2), 2.40–2.50
(m, 3H), 2.76–2.80 (dd, J1 = 14.4, J2 = 4.5 Hz), 3.70–3.75 (m, 1H), 7.40
A
mixture of benzaldehyde (1 mmol), nitromethane (2 mmol) and base
(∼0.5 mmol) was stirred at ∼40 ◦C.
b
Isolated yield.
(d, J = 8.3 Hz, 2H, Haromatic), and 8.10 (d, J = 8.3 Hz, 2H, Haromatic). 13
C
c
2-Nitro-1-phenylethanol was formed together with the nitrostyrene, benzoic
NMR (62.5 MHz, CDCl3): ı 24.3, 31.20, 41.0, 44.8 47.50, 124.3, 129.2,
144.3, 146.0, and 207.0 ppm.
acid, and 1,3-diniro-2-phenyl-propane.
d
1 mmol of MeNO2.
3. Results and discussion
weakest indicator demonstrates a color change, but weaker than
the strongest indicator shows no color change.
3.1. Identification of dolomite
3.2. Dolomite-catalyzed Henry and Knoevenagel reactions in
water
The purity and chemical composition of the finely grinded Ira-
nian dolomite as a gray-white powder was determined according
to the qualitative and quantitative elemental analysis and mate-
rial characterization by X-ray fluorescence assessment (XRF). The
result of XRF analysis is given in Table 1.
To determine the catalytic efficacy of dolomite, the Henry reac-
tion of nitromethane and benzaldehyde was studied comparatively
with various basic catalysts under various conditions (Table 2).
As results indicate the yield of 2-nitro-1-phenylethanol was
higher in the presence of dolomite in aqueous media (entries
3, 7, 10, 15 and 17–20), especially when PEG-400 was used to
increase the low solubility of organic compounds in the aqueous
media of reaction (Table 2, entry 11). Performing the dolomite-
catalyzed Henry reaction in other solvents led to the formation of
three side products which were isolated by column chromatog-
raphy on silica gel (hexane:EtOAc, 8:1) as nitrostyrene, benzoic
acid, and 1,3-dinitro-2-phenyl-propane. The better reaction yield in
water/PEG-400 mixture can be rationalized by the assistance of PEG
as a phase transfer catalyst, a co-solvent, or a micelle maker with
carbonate part of dolomite in its saddle-shape crystalline structure.
These reasons were supported by the higher observed selectivity of
reaction with dolomite (least side reactions) than simple calcium
and magnesium carbonates or oxides (Table 2, entries 17–20). Thus,
the optimal conditions for dolomite-catalyzed Henry reaction were
0.1 g or ∼0.5 mmol of catalyst in water/PEG-400 mixture.
As results indicate, the purity of the finely powdered mineral
dolomite was higher than 98%.
The characteristic bands in FT-IR spectra of dolomite confirm the
presence of carbonyl of carbonate as a broad band at 1434 cm−1
[17]. The two dolomite diagnostic FT-IR absorption bands at
2626 cm−1 and 730 cm−1 are respected to the non-fundamental
2−
combination frequencies and in plane bending mode of CO3
part of dolomite. A little adsorbed surface water was evidenced
by the presence of the broad OH stretching of hydrated carbonate
at 2500–3500 cm−1 for the Iranian dolomite.
Crystalline structure of the Iranian dolomite was determined by
powder X-ray diffraction (XRD). The peaks positioned at various 2ꢁs
of catalyst were compatible with those in the standard XRD pattern
of CaMg(CO3)2 (1999 JCPDS file No. 36-0426). According to the XRD
pattern, other carbonate phases such as NaHCO3 or Na2CO3 were
not observed together with the dolomite phase [18]. The surface
area of the Iranian dolomite was obtained using the BET method
and was found 12.8 m2/g.
Basic strength (H ) of the Iranian dolomite was evaluated as
7.1 following a previously reported Hammett indicator procedure
in the studies of Ilgen [19]. For this measurement, under nitro-
gen atmosphere, 50 mg of catalyst was stirred with appropriate
volumes of methanol solutions of Hammett indicators including
bromothymol blue (H = 7.2), phenolphthalein (H = 9.8), dinitroani-
line (H = 15.0) and nitroaniline (H = 18.4) and left to equilibrate
for 2 h, after which no further color changes were observed. The
color on the catalyst was then noted. The stronger base than the
The same optimization was made for the Knoevenagel con-
densation of benzaldehyde and malononitrile at various dolomite
loading in water at room temperature and again the 0.1 g
(∼50 mol%) of dolomite was chosen as the best amount of catalyst.
The scope of dolomite-catalyzed Henry reaction and Knoeve-
nagel condensation at the optimized conditions were illustrated in
Tables 3 and 4. The clean reactions with high yields of desired prod-
ucts for a variety of electron-withdrawing and electron-releasing
substituted aldehydes and methylene compounds are advantages
of these reactions.
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Table 3
OH
O
NH
CN
CN
Dolomite (0.1 g)
H2O, 40 oC
Dolomite catalyzed preparation of nitroaldoles.
+
H
OH
o
R1
CN
Dolomite (0.1 g), 40 C
CHR1NO2
H
CHO
RCHO
+
R
NO2
H
H2O/PEG
Scheme 2. Dolomite-catalyzed Knoevenagel reaction of salicylaldehyde.
Entry
R
R1
Time (h)
Yield (%)a
more acidity of the ␣-hydrogens attached to carbon with two
electron-withdrawing groups (CN, NO2, and CO) than carbon
attached to NO2 in Henry’s nitroalkanols. Advantageously, dolomite
is a mild enough base to differentiate between these two kinds
of ␣-hydrogens. As supposed in Scheme 3, dolomite acts as a
dual activator of CH2 and C O groups via chair like intermediates
which carbonate part of dolomite is responsible for the abstrac-
tion of ␣-hydrogens, whereas Mg2+ and Ca2+ are responsible for
the activation of coordinated carbonyl group. This led to the more
susceptibility of the carbonyl group toward the nucleophile attack
of the carbanion preformed by abstraction of ␣-hydrogen with car-
bonate of dolomite.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
n-Propyl
n-Propyl
H
CH3
H
H
CH3
CH3
H
H
CH3
H
10
12
2
2.5
6
18
18
18
18
18
18
20
18
20
90
75
90
95
93b
90b
93
95
90b
86
85
70
68
75
PhCH2CH2
2-O2NC6H4
2-O2NC6H4
3-O2NC6H4
3-O2NC6H4
4-O2NC6H4
4-O2NC6H4
2-ClC6H4
4-ClC6H4
H
H
H
H
4-CH3C6H4
4-MeOC6H4
4-OHC6H4
Dolomite-catalyzed condensation of nitromethane or malonon-
itrile with acetophenone as a less electrophile and more hindered
carbonyl group gave no product under similar conditions and con-
firmed again the chemoselectivity of dolomite in these reactions.
Condensation of malononitrile with acetic anhydride, benzoyl chlo-
ride, and acetyl chloride were also attempted but only acetyl
chloride reacted with malononitrile at ∼40 ◦C to give a mixture of
ˇ-ketonitrile and ˇ-ketoamide.
Cl
Cl
15
H
18
91
a
Isolated yield.
Thero:erythro (100:1).
b
Reaction of 2-hydroxybenzaldehyde with malononitrile yielded
a pale yellow crystalline compound with Mp = 163–165 ◦C and
showed a characteristic NH stretching in its FT-IR spectra. Accord-
ing to the spectral and physical data, sequential Knoevenagel
condensation and internal nucleophilic attack of OH to the CN group
led to 2-imino-2H-1-benzopyran-3-carbonitrile [42] in 82% yield
(Scheme 2).
3.3. Dolomite catalyzed Michael-type addition reactions in water
In order to verify the versatility of dolomite as a natural catalyst,
we examined dolomite-catalyzed aza- and thia-Michael addition
reactions of various N- and S-nucleophiles to Michael-acceptors
prepared from dolomite-catalyzed Henry and Knoevenagel reac-
tions (Table 5).
The results clearly reveal that the presence of dolomite as a
reaction promoter is essential for the efficiency of process. A rea-
sonable account for this promotion is affording a mild basic media
An advanced comparison between the results of dolomite-
catalyzed Henry and Knoevenagel reactions confirm that Henry’s
nitroalkanols did not dehydrate in the presence of dolomite, while
dehydration of Knoevenagel alkanols led to tri-substituted alkenes
under similar conditions. Driving force for this dehydration is
Table 4
Dolomite catalyzed preparation of tri-substituted alkenes.
O
H
EWG
EWG
Dolomite (0.1 g, ~50 mol%)
+
EWG
EWG
Ar
H
H2O, 40 oC
Ar
Entry
Ar
Ph
4-ClC6H4
4-ClC6H4
4-O2NC6H4
4-O2NC6H4
4-MeOC6H4
4-MeOC6H4
4-MeC6H4
2-O2NC6H4
4-HOC6H4
2-Furyl
Substrate
Time (h)
Yield (%)a
Mp (◦C)b [ref.]
1
2
3
4
5
6
7
8
9
10
11
12
13
14
NCCH2CN
1
93
84–86 [29]
91–92 [42]
NCCH2CO2Et
NCCH2NO2
NCCH2CN
NCCH2CO2Et
NCCH2CN
NCCH2CO2Et
NCCH2CN
NCCH2CO2Et
NCCH2CN
2.5
0.5
0.5
2
1.5
2.5
1.5
0.5
1.5
1
91c
96c
94
116–118 [41]
162–163 [43]
169–170 [43]
116–117 [42]
80–81 [42]
129–130 [42]
139–141 [29]
188–189 [42]
72–73 [42]
90c
91
85c
92
95c
90
NCCH2CN
NCCH2NO2
NCCH2CN
92
2-Furyl
4-Pyridyl
2-Pyridyl
0.5
1
0.5
96c
90
125–127 [42]
100–101
d
d
NCCH2CN
–
–
O
HN
NH
O
O
15
Ph
1.2
92
257–259 [42]
a
Isolated yields.
b
c
These values are comparable with those reported in the literature.
Only E-isomer was obtained.
A polymeric product was obtained.
d
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Table 5
Dolomite-catalyzed conjugated addition of amines or thiols to Michael acceptors in water.
Entry
Nucleophile
Michael acceptors
Time (min)
Producta
Isolated yield (%)
NHPh
NO2
NO2
Ph
NH2
Ph
1
30
93
NHCH2Ph
NO2
CH2NH2
NH2
NO2
Ph
Ph
Ph
2
3
20
20
95
95
NH(CH2)3CH3
NO2
NO2
Ph
Ph
N
NO2
Ph
NH
NO2
4
15
98
PhNH
O
NH2
COMe
5
6
7
15
10
30
92
94
93
O
PhCH2NH
CH2NH2
COMe
O
O
Ph(CH2)3NH
NH2
COMe
N
NH
COMe
8
9
5
96
93
Me
O
N
NHMe
Ph
COMe
30
O
N
NH
CONH2
CN
NH2
10
11
20
60
91b
91
PhCH2NH
CH2NH2
CN
CN
N
N
NH
CN
COOMe
O
12
13
30
30
95
93
NH
COOMe
O
N
NH
14
15
30
88
SH
PhS
CN
CN
S
30
30
94
90
O
SH
O
16
a
All products were known and characterized by comparison of their spectral data with those of reported.
A mixture of products contain ˇ-amino carbamide were formed.
b
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F. Tamaddon et al. / Journal of Molecular Catalysis A: Chemical xxx (2012) xxx–xxx
Scheme 3. Proposed mechanism for dolomite-catalyzed condensation reactions.
by dolomite for dual activation of nucleophiles and conjugated
double bonds to C O group. The nucleophilicity of NH- or SH-
bond increases via the hydrogen bonding with carbonate part of
dolomite [44] and the susceptibility of the conjugated double bonds
enhanced by coordination of the C O group to Mg2+ and Ca2+ of
dolomite.
NO2
NO2
Dolomite (0.2 g)
NO2
Ph
Ph
+
CH3NO2
H2O, EtOH, Reflux
Scheme 5. Michael addition of nitromethane to nitrostyrene.
No transamidation or replacement of the ester group by amine
was observed under these mild conditions and the reactivity of
different Michael acceptors were strongly related to the nature
and power of their electron-withdrawing groups. Therefore, the
aza-Michael addition of N-nucleophiles to nitrostyrene occurred in
higher yield than acrylamide (Table 5, entries 1–4).
Moreover, the chemoselectivity of reaction was demonstrated
by the competitive dolomite-catalyzed aza-Michael addition of ani-
line and benzyl amine with nitrostyrene. This led to the formation of
N-benzyl-2-nitro-1-phenylethanamine in 94% yield in water. Reac-
tion of methyl vinyl ketone with a 1:1 mixture of piperidine and
benzylamine was also afforded the 4-(piperidin-1-yl)butane-2-one
in 93% yield (Scheme 4).
condensation of malononitrile with benzaldehyde, and Michael
addition of benzylamine to nitrostyrene in water. In all cases,
the filtered and washed catalyst was dried at room temperature.
The FT-IR spectra and XRF analysis of the recycled and re-dried
dolomites were the same as fresh ones. The regenerated dolomites
were then subjected to the further reaction runs. The yields of the
first Henry and Knoevenagel experiments were similar with three
subsequent reaction runs in the presence of recycled dolomite.
Even in the Michael addition after two runs, catalytic activity of the
recycled dolomite was less than fresh catalyst. The loss of activity
is may be related to the deactivation of catalyst by coke forma-
tion from both nitrostyrene and benzylamine during the Michael
addition reaction at room temperature.
The synthesis of 1,3-dinitro-2-phenyl-propane was also
attempted by addition of large excess of nitromethane to
nitrostyrene in the presence of dolomite (0.2 g, ∼1 mmol) under
reflux conditions (Scheme 5).
The recyclability of dolomite was next examined for the
Henry reaction of benzaldehyde with nitromethane, Knoevenagel
4. Conclusion
In summary, we have developed a green advance to Henry, Kno-
evenagel, and Michael reactions in water for the preparation of
nitroalkanols, tri–substituted alkenes, ˇ-amino and ˇ-thio substi-
tuted carbonyl compounds in the presence of Iranian dolomite as
a new heterogeneous natural catalyst. This catalyst benefits from
the chemoselectivity, non-toxicity, environmental safety, simple
handling, reusability, and versatility for various organic transfor-
mations in a range of substrates.
NHCH2Ph
NO2
Dolomite (0.1 g, ~50 mol%)
NH2
NO2
94%
Ph
+
NHPh
H2O, r.t., 10 min
NH2
NO2
0%
Ph
Ph
O
H
O
NH
Dolomite (0.1 g)
H2O, r.t., 5 min
N
93%
NHCH2Ph
0%
+
Acknowledgment
NH2
H
O
We gratefully acknowledge the Yazd University Council for
financial supports of this research.
Scheme 4. Chemoselectivity of dolomite-catalyzed Michael-reactions.
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Appendix A. Supplementary data
[19] O. Ilgen, Fuel Process. Technol. 92 (2011) 452–455.
[20] L. Henry, Bull. Soc. Chim. Fr. 13 (1895) 999–1002.
[21] J. Bennazha, M. Zahouily, S. Sebti, A. Boukhari, E.M. Holt, Catal. Commun. 2
(2001) 101–104.
[22] A. Kattuboina, G. Li, Tetrahedron Lett. 49 (2008) 1573–1577.
[23] B.V. Subba Reddy, S.M. Reddy, S. Manisha, C. Madan, Tetrahedron Asymm. 22
(2011) 530–535.
Supplementary data associated with this article can be
found, in the online version, at http://dx.doi.org/10.1016/j.molcata.
2012.08.027.
[24] J.M. Rodriguez, M.D. Pujol, Tetrahedron Lett. 52 (2011) 2629–2632.
[25] J. Han, Y. Xu, Y. Su, X. She, X. Pan, Catal. Commun. 9 (2008) 2077–2079.
[26] Y. Hu, Y.H. He, Z. Guan, Catal. Commun. 11 (2010) 656–659.
References
[27] S. Balalaie, M. Sheikh-Ahmadi, M. Bararjanian, Catal. Commun.
1724–1728.
[28] B. Tamami, A. Fadavi, Catal. Commun. 6 (2005) 747–751.
[29] S. Balalaie, M. Bararjanian, Sh Hekmat, P. Salehi, Synth. Commun. 36 (2006)
2549–2557.
8 (2007)
[1] J.J. Bozell, G.R. Petersen, Green Chem. 12 (2010) 539–554.
[2] G. Sartori, R. Maggi, Chem. Rev. 113 (2010) PR1–PR54.
[3] G.A. Meshram, V.D. Patil, Tetrahedron Lett. 50 (2009) 1117–1121.
[4] S. Farhadi, M. Taherimehr, Catal. Commun. 9 (2008) 703–708.
[5] B. Morak-Miodawska, K. Pluta, Heterocycles 78 (2009) 1289–1298.
[6] B. Karimi, J. Maleki, J. Org. Chem. 68 (2003) 4951–4954.
[7] M. Hosseini Sarvari, H. Sharghi, J. Org. Chem. 69 (2004) 2573–2576.
[8] E.K. Goharshadi, Y. Ding, P.J. Nancarrow, Phys. Chem. Solids 69 (2008)
2057–2060.
[9] F. Tamaddon, M.A. Amrollahi, L. Sharafat, Tetrahedron Lett. 46 (2005)
7841–7844.
[10] Y.J. Kim, R.S. Varma, Tetrahedron Lett. 45 (2004) 7205–7208.
[11] K. Akutu, H. Kabashima, T. Seki, H. Hattori, J. Appl. Catal. A 247 (2003) 65–74.
[12] M. Murata, T. Hara, K. Mori, M. Ooe, T. Mizugaki, K. Ebitani, K. Kaneda, Tetrahe-
dron Lett. 44 (2003) 4981–4984.
[13] T. Taniguchi, K. Kadota, A.S. El Azab, K. Ogasawara, Synlett 8 (1999) 1247–1248.
[14] H. Kotsuki, T. Ohishi, T. Araki, K. Arimura, Tetrahedron Lett. 39 (1998)
4869–4870.
[15] K.V.N.S. Srinivas, B. Das, J. Org. Chem. 68 (2003) 1165–1167.
[16] Y. Xi, R.J. Davis, J. Mol. Catal. A: Chem. 341 (2011) 22–27.
[17] J. Ji, Y. Ge, W. Balsam, J.E. Damuth, J. Chen, Mar. Geol. 258 (2009) 60–68.
[18] D.A. Constantinou, J.L.G. Fierro, A.M. Efstathiou, Appl. Catal. B: Environ. 95
(2010) 255–269.
[30] H. Firouzabadi, N. Iranpoor, A.A. Jafari, Synlett (2005) 299–303.
[31] M.K. Chaudhuri, H. Sahid, J. Mol. Catal. A: Chem. 269 (2007) 214–217.
[32] P. Kalita, R. Kumar, Appl. Catal. A: Gen. 398 (2011) 250–258.
[33] B. Das, N. Chowdhury, J. Mol. Catal. A: Chem. 263 (2007) 212–215.
[34] A. Ziyaei-Halimehjani, M.R. Saidi, Tetrahedron Lett. 40 (2008) 1244–1248.
[35] K. Tabatabeian, M. Mamaghani, N.O. Mahmoodi, A. Khorshidi, J. Mol. Catal. A:
Chem. 270 (2007) 112–116.
[36] F. Tamaddon, F. Aboee, A. Nasiri, Catal. Commun. 16 (2011) 194–197.
[37] F. Tamaddon, F. Tavakoli, J. Mol. Catal. A: Chem. 337 (2011) 52–55.
[38] F. Tamaddon, A. Nasiri, S. Farokhi, Catal. Commun. 12 (2011) 1477–1482.
[39] F. Tamaddon, M.R. Sabeti, A.A. Jafari, F. Tirgir, E. Keshavarz, J. Mol. Catal. A:
Chem. 351 (2011) 41–45.
[40] F. Tamaddon, M. Farahi, B. Karami, J. Mol. Catal. A: Chem. 356 (2012) 85–89.
[41] D. Amantini, F. Fringuelli, O. Piermatti, F. Pizzo, L. Vaccaro, Green Chem. 3 (2001)
229–232.
[42] M.L. Deb, P.J. Bhuyan, Tetrahedron Lett. 46 (2005) 6453–6456.
[43] R.M. Kumbhare, M. Sridhar, Catal. Commun. 9 (2008) 403–405.
[44] J.H. Gorvin, D.P. Whalley, J. Chem. Soc., Perkin I 1 (1979) 1364–1370.
Please cite this article in press as: F. Tamaddon, et al., J. Mol. Catal. A: Chem. (2012), http://dx.doi.org/10.1016/j.molcata.2012.08.027