Nano α-Al2O3 supported ammonium dihydrogen phosphate (NH4H2PO4/Al2O3): Preparation, characterization and its application as a novel and heterogeneous catalyst for the one-pot synthesis of tetrahydrobenzo[b]pyran and pyrano[2,3-c]pyrazole derivatives

Article abstract of DOI:10.1039/c4ra07813f

A simple, efficient, and environmentally benign route was developed for the preparation of 2-amino-3-cyano-4-aryl-7,7-dimethyl-5,6,7,8-tetrahydrobenzo[b]pyrans and 6-amino-5-cyano-4-aryl-1,4-dihydropyrano[2,3-c]pyrazoles from the condensation of various aldehydes, malononitrile, and 1,3-dicarbonyl compounds (1,3-cyclohexanedione or 5,5-dimethyl-1,3-cyclohexanedione) or 3-methyl-1-phenyl-2-pyrazoline-5-one, using NH₄H₂PO₄/Al₂O₃ with good yields. The use of easily available catalyst, shorter reaction times, better yields, the simplicity of the reaction, the heterogeneous system, and the easy work up are the advantages of the present method. Characterization of the catalyst was performed by FT-IR spectroscopy, X-ray diffraction (XRD) techniques, thermal analysis (TG/DTG) and Transmission electron microscopy (TEM).

Full text of DOI:10.1039/c4ra07813f

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PAPER
Nano a-Al O supported ammonium dihydrogen
2
3
phosphate (NH H PO /Al O ): preparation,
4
2
4
2 3
Cite this: RSC Adv., 2014, 4, 42873
characterization and its application as a novel and
heterogeneous catalyst for the one-pot synthesis
of tetrahydrobenzo[b]pyran and pyrano[2,3-c]
pyrazole derivatives
Behrooz Maleki* and Samaneh Sedigh Ashrafi
A simple, efficient, and environmentally benign route was developed for the preparation of 2-amino-3-
cyano-4-aryl-7,7-dimethyl-5,6,7,8-tetrahydrobenzo[b]pyrans
and
6-amino-5-cyano-4-aryl-1,4-
dihydropyrano[2,3-c]pyrazoles from the condensation of various aldehydes, malononitrile, and 1,3-
dicarbonyl compounds (1,3-cyclohexanedione or 5,5-dimethyl-1,3-cyclohexanedione) or 3-methyl-1-
4 2 4 2 3
phenyl-2-pyrazoline-5-one, using NH H PO /Al O with good yields. The use of easily available catalyst,
Received 30th July 2014
Accepted 3rd September 2014
shorter reaction times, better yields, the simplicity of the reaction, the heterogeneous system, and the
easy work up are the advantages of the present method. Characterization of the catalyst was performed
by FT-IR spectroscopy, X-ray diffraction (XRD) techniques, thermal analysis (TG/DTG) and Transmission
electron microscopy (TEM).
DOI: 10.1039/c4ra07813f
www.rsc.org/advances
cyano-4-aryl-7,7-dimethyl-5,6,7,8-tetrahydrobenzo[b]pyrans
and 6-amino-5-cyano-4-aryl-1,4-dihydropyrano[2,3-c]pyrazoles,
Introduction
In recent years, synthetic chemists have shown tremendous which include bicomponent condensation of 1,3-dicarbonyl
interest in developing highly efficient transformations for the compounds (1,3-cyclohexanedione or 5,5-dimethyl-1,3-
5
synthesis of 4H-pyrans and pyranopyrazoles and their deriva- cyclohexanedione) with a-cyanocinnamonitrile, or through
tives due to their potential applications in the pharmaceutical one-pot reaction three-component of aldehydes, malononitrile,
and agrochemical industries and synthetic chemistry. These and 1,3-dicarbonyl compounds (1,3-cyclohexanedione or 5,5-
compounds have a wide range of biological and pharmalogical dimethyl-1,3-cyclohexanedione)
or
3-methyl-1-phenyl-2-
6
properties, such as anti-allergic, anti-ammatory, anti-tumor, pyrazoline-5-one, in the presence of various catalysts. Also, a
spasmolytic, diuretic, anti-cancer, anti-coagulant and anti- highly efficient synthesis of 4H-pyrano[2,3-c]pyrazole has been
1
anaphylactic activities. Polyfunctionalized 4H-pyrans are a reported using four component cyclocondensation of hydrazine
2
common structural unit in a number of natural products. 4H- hydrate or phenylhydrazine, ethylacetoacetate, aldehydes and
Pyrans ring can be transformed to pyridine systems, which malononitrile in the presence of L-proline and [Bimim]BF
at 50
4
ꢀ
7
relate to pharmacologically important calcium antagonist of the
C. Generally, these compounds have been prepared through
3
dihydropyridine type. Also, 4H-benzo[b]pyrans can be used as one-pot reaction three-component in the presence several
8
cognitive enhancers, for the treatment of neurodegenerative catalyst such as, piperidine, hexadecyltrimethyl ammonium
9
10
11
disease, including Alzheimer's disease, amyotrophic lateral bromide (HTMAB), sodium bromide, ionic liquids, tetra-
12
sclerosis, AIDS-associated dementia, and Down syndrome, as methyl ammonium hydroxide, diammunium hydrogen phos-
well as for the treatment of Schizophrenia and Huntington's phate, organocatalysts, sodium selenate, tetrabutylammo-
13
14
15
4
16
17
diseases.
Because of their extensive range of pharmacological activity [KAl(SO
and also their industrial and synthetic applications, several caro's acid, amine or amino acid, potassium phosphate,
nium bromide (TBAB),
polyaniline/silicagel,
O], rare earth peruorooctanoate [Re(PFO) ,
3
alum
18
19
)
2
$12H
20
4
2
21
22
2
3
24
25
methods have been reported for the synthesis of 2-amino-3- PPA/SiO
Pd(OAc)
2
,
3 2
the use of microwave irradiation, BF $OEt ,
26
27
2
, PPh
3
29
, Na
2
CO
3
,
3
NEt , toluene/EtOH, DABCO,
28
30
EtOH, TPPA, t-BuOK/t-BuOH and L-proline under ultra-
3
1
Department of Chemistry, Hakim Sabzevari University, Sabzevar 96179-76487, Iran. sound irradiation. Many of these methods suffer from one or
E-mail: b.maleki@hsu.ac.ir; malekibehrooz@gmail.com; Fax: +98-571-4410300; Tel:
more limitations such as low yields, use of expensive reagents,
+
98-571-4002643
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4 2 4 2 3
Scheme 1 Synthesis of tetrahydrobenzo[b]pyrans and pyrano[2,3-c]pyrazoles using NH H PO /Al O as catalyst.
long reaction times, tedious work-up procedures, and it continued to optimize the model reaction by detecting the
co-occurrence of several side reactions. In recent decade, many efficiency of polar (CH CN, MeOH, H O) and nonpolar (CH Cl
heterogeneous organic reactions have been performed using CCl ) solvents (entry 17–21). Ethanol was found to be the best in
3
2
2
2
,
4
32
various reagents supported on solid materials. NH H PO / terms of yield and time (entry 9). The effect of temperature was
4
2
4
Al O is an inexpensive, easily available, non-toxic, low toxicity, also studied by carrying out the model reaction in the presence
2
3
ꢀ
ꢀ
heterogeneous, low cost and environmentally benign of NH
compound that is used in various organic transformations.
4
H
2
PO
4
/Al
ꢀ
2
O
3
(0.03 g) at room temperature (25 C), 50 C,
ꢀ
60 C, and 70 C (entry 22–25). It was observed that the yield
MCRs involve three or more starting materials reacting in a increased was as the reaction temperature rose. Additionally,
33
single ask to form a new product. One example of an MCRs is this reaction took place in the absence of solvent using 0.03 g of
ꢀ
a three-component, one-pot synthesis of tetrahydrobenzo[b]- catalyst at 80 C, interestingly; the same yield was achieved
pyrans and pyrano[2,3-c]pyrazoles.
(entry 26). Also, the effect of the reaction parameters such as
As part of our work on one-pot multi-component reactions amount of catalyst and temperature were studied in detail. The
ꢀ
(
MCRs) for the synthesis of various heterocyclic compounds of best result was obtained with 0.03 g of catalyst at 80 C (entry
34
biological importance and in continuation of our previous 27–30).
work on the development of new synthetic methodologies, we
35
Aer optimization of the reaction conditions, we studied the
now wish to report here a highly efficient procedure for the generality of these conditions to other substrates. By using this
preparation of tetrahydrobenzo[b]pyrans and pyrano[2,3-c]pyr- method, different kinds of aldehydes reacted with 1,3-dicar-
azoles via
a one-pot three-component reactions using bonyl compounds (1,3-cyclohexanedione or 5,5-dimethyl-1,3-
NH H PO /Al O as catalyst (Scheme 1).
cyclohexanedione) and malononitrile to produce the corre-
sponding 2-amino-3-cyano-4-aryl-7,7-dimethyl-5,6,7,8-tetra-
hydrobenzo[b]pyrans under both heterogeneous (in reuxing
EtOH) and also solvent free conditions (Table 2). The property
of substituent on the aromatic ring showed strongly obvious
effects in terms of yields and time under this reaction condi-
tion. Aldehydes containing electron-withdrawing groups (such
as nitro, halide) reacted better to give the corresponding prod-
ucts in higher yields than aromatic aldehydes containing
electron-donating groups (such as alkyl, alkoxy, hydroxyl).
Encouraged by these results, we replaced the cyclic 1,3-
dicarbonyl compounds (1,3-cyclohexanedione or 5,5-dimethyl-
4
2
4
2 3
Result and discussion
Our preliminary investigations were focused on systematic
evaluation of different catalysts for the model reaction of
benzaldehyde 1a (1 mmol), dimedone (1 mmol), and malono-
ꢀ
nitrile (1.2 mmol) in EtOH aer reacting for 15 min at 80 C
(Table 1, entry 1). It was found that the conventional Lewis acids
such as NH Cl, NH F, KH PO , K HPO , and H PO as well as
4
4
2
4
2
4
3
4
the condition of no catalyst showed poor effect to the yield of
the product (entry 2–7). Even when large amount of catalyst was
used, the result was still unsatisfactory (entry 8). With the use of
NH H PO /Al O , the results seemed to be better (entry 9–14).
1
,3-cyclohexanedione) with 3-methyl-1-phenyl-2-pyrazoline-5-
one in same conditions (Scheme 1). Initially, we optimized
amount of NH PO /Al for condensation of the reaction
between 5,5-dimethyl-1,3-cyclohexanedione, benzldehyde
1 mmol), and malononitrile (1.2 mmol). The best result was
4
2
4
2 3
4
H
2
4
2 3
O
On the optimized of amount catalyst (entry 15 and 16), we found
that 0.03 g of NH PO /Al could effectively catalyze the
reaction for the synthesis of the desired product (entry 9). Then
4
H
2
4
2 3
O
(
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Table
1
Optimization of reaction conditions for the synthesis of 2-amino-3-cyano-4-(phenyl)-7,7-dimethyl-5-oxo-4H-5,6,7,8-tetra-
hydrobenzo[b]pyran (5a)
a
Entry
Catalyst
Conditions
Time (min)
Yield (%)
1
2
3
4
5
6
7
8
9
NH
NH
NH
4
4
4
H
2
PO
4
(30 mol%)
EtOH/reux
EtOH/reux
EtOH/reux
EtOH/reux
EtOH/reux
EtOH/reux
EtOH/reux
EtOH/reux
EtOH/reux
EtOH/reux
EtOH/reux
EtOH/reux
EtOH/reux
EtOH/reux
EtOH/reux
EtOH/reux
20
40
40
40
50
20
20
20
15
30
30
30
40
30
20
15
15
15
15
60
60
60
40
40
30
20
30
20
20
30
71
52
50
64
60
48
28
72
86
61
59
72
66
75
77
85
60
79
46
38
34
Impure
60
64
80
84
76
83
85
80
Cl (30 mol%)
F (30 mol%)
PO
KH
HPO
PO
2
4
(30 mol%)
(30 mol%)
K
2
4
H
3
4
(5 drop)
—
NH
NH
NH
NH
4
4
4
4
H
H
Cl/Al
F/Al
PO
2
2
PO
PO
4
(40 mol%)
/Al (0.03 gr)
(0.03 gr)
(0.03 gr)
4
2 3
O
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
2 3
O
2
O
3
KH
HPO
PO
2
4
/Al
/Al
2
O
3
(0.03 gr)
(0.03 gr)
K
2
4
2
O
3
H
3
4
/Al
2
O
3
(0.03 gr)
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
NH
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
H
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
PO
PO
PO
PO
PO
PO
PO
PO
PO
PO
PO
PO
PO
PO
PO
PO
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
/Al
2
/Al
2
/Al
2
/Al
2
/Al
2
/Al
2
/Al
2
/Al
2
/Al
2
/Al
2
/Al
2
/Al
2
/Al
2
/Al
2
/Al
2
/Al
2
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
(0.02 gr)
(0.04 gr)
(0.03 gr)
(0.03 gr)
(0.03 gr)
(0.03 gr)
(0.03 gr)
(0.03 gr)
(0.03 gr)
(0.03 gr)
(0.03 gr)
(0.03 gr)
(0.02 gr)
(0.04 gr)
(0.03 gr)
(0.03 gr)
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
CH
CH
3
CN/reux
OH/reux
3
H
2
O/reux
CH Cl /reux
CCl
2
2
4
/reux
ꢀ
EtOH/25 C
EtOH/50 C
EtOH/60 C
EtOH/70 C
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Solvent-free/80 C
Solvent-free/80 C
Solvent-free/80 C
Solvent-free/90 C
ꢀ
Solvent-free/70 C
a
Isolated yields.
obtained with 0.03 gr of NH H PO /Al O . To investigate the mmol) and ethylacetoacetate (1.2 mmol) in the presence of
4
2
4
2 3
4 2 4 2 3
versatility of the catalyst, the reaction of cyclic 1,3-dicarbonyl NH H PO /Al O were selected as a model reaction and the
compounds was carried out with various aldehydes and malo- effects of the reaction parameters such as amount of the catalyst
nonitrile for synthesis of 6-amino-5-cyano-4-aryl-1,4-dihydro- and temperature were studied in detail. The best result was
4 2 4 2 3
pyrano[2,3-c]pyrazoles derivatives under solvent-free conditions obtained with 0.03 gr of NH H PO /Al O under thermal
ꢀ
ꢀ
at 80 C and in reuxing EtOH (Table 3). All reactions proceeded conditions in EtOH at 80 C. Several structurally diverse alde-
ꢀ
efficiently within 15–40 minutes at 80 C to provide the corre- hydes (Scheme 2, Table 2) were subjected to condensation with
sponding pyrano[2,3-c]pyrazoles derivatives in good yields phenylhydrazine, malononitrile and ethylacetoacetate under
ranging from 74–94%.
the catalytic inuence of NH H PO /Al O (0.03 g).
4 2 4 2 3
In order to broaden the scope of the present method, the
Aer successfully synthesizing of a series of 6-amino-5-
replacement of malononitrile with ethyl cyanoacetate was cyano-4-aryl-1,4-dihydropyrano[2,3-c]pyrazoles in good yields,
examined. To our delight, the reaction underwent successful we replaced phenyl hydrazine with hydrazine hydrate in same
condensation under similar reaction conditions, to afford the conditions (Scheme 3). We began this study by subjecting 4-
corresponding tetrahydrobenzo[b]pyran and pyrano[2,3-c]pyr- methoxybenzaldehyde (1 mmol), hydrazine hydrate (1.2 mmol),
azole derivatives in high yields (Table 2, product 5p–q). It was and ethylacetoacetate (1.2 mmol) to reactions with malononi-
observed that with ethyl cyanoacetate a slightly longer reaction trile (1.2 mmol) in the presence of NH H PO /Al O under
4
2
4
2 3
ꢀ
time was needed for reasonably high yields.
thermal conditions in EtOH at 80 C. Unfortunately, complex
Finally, we have developed this synthetic method for one-pot mixtures were observed. To minimize the formation of
efficient synthesis of 6-amino-5-cyano-4-aryl-1,4-dihydropyrano byproducts, the hydrazine hydrate (1.2 mmol) and ethyl-
ꢀ
[
2,3-c]pyrazoles by polycondensation aldehydes with phenyl- acetoacetate (1.2 mmol) were rst stirred in EtOH at 80 C for 10
hydrazine, malononitrile and ethylacetoacetate. To achieve the min. Next 4-methoxybenzaldehyde (1 mmol), and malononitrile
optimal reaction condition, the reaction of benzaldehyde 1a (1 (1.2 mmol) were added and the mixture was heated for 75 min
ꢀ
mmol) with phenylhydrazine (1.2 mmol), malononitrile (1.2 in EtOH at 80 C. The desired product was obtained in 72%
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Table
catalyst
2
4 2 4 2 3
Preparation of 2-amino-3-cyano-4-aryl-7,7-dimethyl-5,6,7,8-tetrahydrobenzo[b]pyrans derivatives using NH H PO /Al O as
a
ꢀ
Mp ( C)
1
b
Product (5)
Ar
X
R
Time (min)
15 (20)
Yield (%)
Found
Reported
C
6
H
5
CN
CH
3
86 (84)
228–230
227–239 (ref. 9)
4-ClC
6
H
4
CN
CH
3
15 (30)
92 (89)
209–211
206–207 (ref. 9)
4-CH
3
6
C H
4
CN
CH
3
15 (15)
94 (88)
212–214
214–216 (ref. 9)
3
3
2
-ClC
6
H
4
CN
CN
CN
CH
CH
CH
3
3
3
35 (35)
20 (25)
30 (25)
91 (87)
90 (90)
80 (80)
229–230
196–198
210–212
233–234 (ref. 9)
-MeOC
6
H
4
—
-MeC
6
H
4
212–214 (ref. 14)
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Table 2 (Contd.)
ꢀ
Mp ( C)
1
b
Product (5)
Ar
X
R
Time (min)
Yield (%)
Found
Reported
4
-CNC
6
H
4
CN
CH
3
15 (25)
97 (89)
225–228
225–228 (ref. 14)
4
3
4
-NO
2
C
6
H
4
CN
CN
CN
CH
CH
CH
3
3
3
15 (30)
15 (30)
15 (30)
98 (92)
90 (82)
94 (89)
180–182
213–215
197–199
177–179 (ref. 14)
210–212 (ref. 14)
196–198 (ref. 18)
2 6 4
-NO C H
6 4
-BrC H
4-FC
6
H
4
CN
CH
3
20 (40)
90 (84)
190–191
191–193 (ref. 18)
2-ClC
6
H
4
CN
CH
3
20 (30)
90 (84)
214–216
215–216 (ref. 18)
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Table 2 (Contd.)
ꢀ
Mp ( C)
1
b
Product (5)
Ar
X
R
Time (min)
Yield (%)
Found
Reported
2
,4-ClC
6
H
4
CN
CH
3
20 (20)
94 (90)
190–192
189–191 (ref. 18)
c
6
3-HOC H
5
CN
CH
3
60 (60)
82 (74)
236–238
236–238 (ref. 18)
2
-MeOC
6
H
4
CN
CH
3
30 (25)
84 (82)
210–212
212–214 (ref. 21)
c
C
6
H
5
CO
2
Et
CH
3
10 (10)
62 (45)
155–157
158–160 (ref. 13)
c
4-ClC
6
H
4
CO
2
Et
CH
3
6 (5)
70 (68)
149–150
153–155 (ref. 13)
4-NO
2
6
C H
4
CN
H
15 (15)
92 (90)
230–232
234–235 (ref. 24)
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Table 2 (Contd.)
ꢀ
Mp ( C)
1
b
Product (5)
Ar
X
R
Time (min)
Yield (%)
Found
Reported
4
-CNC
6
H
4
CN
H
15 (15)
90 (90)
229–232
234–236 (ref. 24)
4-ClC
6
H
4
CN
H
25 (35)
84 (80)
224–226
226–228 (ref. 24)
a
b
c
The reaction times and yields obtained under solvent-free conditions are given in parentheses. Isolated yields. The reaction time is hour.
yield. This two-step procedure allows the one-pot four compo-
nent reaction to be controlled, avoiding the separation of performed at the temperature range 0 to 1000 C. Thermal
Thermal analysis of initial powder of ADP/nano a-Al O was
2 3
ꢀ
intermediates, as well as time-consuming and costly purica- gravimetric (TGA) and differential thermal gravimetry (DTG)
tion processed. Subsequently, this study was used to develop a analysis of the ADP/nano a-Al O was investigated by raising its
2 3
ꢀ
À1
ꢀ
four-component synthesis of diverse pyranopyrazoles (Table 4). temperature at the rate of 5 C min in air up to 1000 C to
Reusability of the catalyst was also investigated. For this analyze its thermal decomposition behavior. According to the
purpose, the same model reaction was again studied under TGA curve and its derivative (DTG), two peak weight loss have
ꢀ
optimized conditions. Aer completion of the reaction, the been specied at temperatures 501 and 875 C. Weight loss at
reaction mixture was ltered in hot condition to separate the 875 C is possibly due to decomposition of ADP. Weight loss at
catalyst, dried at 120 C for 4 h, and reused for similar reaction. 501 C is due to decomposition of nano a-Al
The catalyst could be reused at least three times without tures above 600 C, the phase diagram became Constant for the
ꢀ
ꢀ
ꢀ
2
O
3
. At tempera-
ꢀ
signicant loss of activity (Fig. 1).
The catalyst NH PO /Al
nano-alumina support by NH
formation of the phase of ADP/nano a-Al
prepared by impregnation of tures above 900 C the phase diagram became Constant for the
2
O
3
. Also, at tempera-
ꢀ
4
H
2
4
2
O
3
4
H
2
PO
4
was characterized by FT-IR formation of the phase II of ADP/nano a-Al
2
O
3
(Fig. 4).
spectroscopy, X-ray diffraction (XRD), thermal analysis (TGA/
The supported catalyst was consisted with TEM results
DTG) and Transmission electron microscopy (TEM).
(Fig. 5). As shown in Fig. 5, the NH H PO /nano a-Al O powder
4
2
4
2 3
The infrared spectra's of Al O and catalyst, before and aer indicated strong agglomeration of particles with varied spher-
2
3
using it, were shown in Fig. 2. Frequency comparison of IR ical sizes showed that the particles were of irregular shape with
spectra shows the appearance of absorption in region 1442 a wide size distribution. This is quite reasonable because of the
À1
cm . This absorption is due to the P]O stretching vibrations varying particle size of the powder, as shown in XRD patterns.
of OPO
3
H
2
groups presence that were shown in Scheme 4.
A plausible mechanism for one-pot synthesis of 2-amino-3-
The XRD pattern of the NH
4
H
2
PO /nano a-Al is also cyano-4-aryl-7,7-dimethyl-5,6,7,8-tetrahydrobenzo[b]pyrans and
4
2 3
O
presented in Fig. 3. Marked peaks are attributed to nano- 6-amino-5-cyano-4-aryl-1,4-dihydropyrano[2,3-c]pyrazoles were
alumina support. Additional weak peaks are probably related given in Scheme 5.
36–41
to the formation of NH H PO /nano-Al O .
4
2
4
2 3
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a
4 2 4 2 3
Table 3 Preparation of 6-amino-5-cyano-4-aryl-1,4-dihydropyrano[2,3-c]pyrazoles derivatives using NH H PO /Al O as catalyst
ꢀ
Mp ( C)
b
Product (6)
Ar
X
Time (min)
Yield (%)
Found
Reported
C
6
H
5
CN
15 (15)
84 (80)
165–166
168–170 (ref. 7)
4
4
4
-ClC
6
H
4
CN
CN
CN
20 (20)
40 (20)
30 (20)
94 (85)
94 (85)
89 (85)
182–184
186–187 (ref. 7)
183–184 (ref. 7)
174–175 (ref. 7)
-BrC
6
H
4
185–186
-CH
3
C
6
H
4
176–178
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Table 3 (Contd.)
ꢀ
Mp ( C)
b
Product (6)
Ar
X
Time (min)
Yield (%)
Found
Reported
4
-MeOC
6
H
4
CN
20 (20)
82 (80)
170–172
171–172 (ref. 7)
3-NO
2
6
C H
4
CN
20 (15)
74 (86)
190–192
188–190 (ref. 7)
2-ClC
6
H
4
CN
20 (15)
82 (80)
147–149
144–146 (ref. 7)
2,4-Cl
2
C
6
H
4
CN
20 (15)
90 (86)
180–182
182–184 (ref. 7)
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Table 3 (Contd.)
ꢀ
Mp ( C)
b
Product (6)
Ar
X
Time (min)
Yield (%)
Found
Reported
4-NO
2
6
C H
4
CN
20 (20)
82 (80)
199–197
194–196 (ref. 7)
6
4-HOC H
4
CN
15 (15)
90 (80)
208–210
206–207 (ref. 7)
3-ClC
6
H
4
CN
20 (15)
91 (82)
152–154
148–150 (ref. 7)
a
b
The reaction times and yields obtained under solvent-free conditions are given in parentheses. Isolated yields.
Scheme 2 Four-component synthesis of 6-amino-5-cyano-4-aryl-1,4-dihydropyrano[2,3-c]pyrazoles.
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Scheme 3 Preparation of 6-amino-5-cyano-4-aryl-1,4-dihydropyrano[2,3-c]pyrazoles by condensation of four-component.
2
-Amino-3-cyano-4-(phenyl)-7,7-dimethyl-5-oxo-4H-5,6,7,8-
Experimental
1
tetrahydrobenzo[b]pyran (5a). H NMR (300 MHz, CDCl , ppm)
3
IR spectra were recorded on a Shimadzu 435-U-04 spectropho- d 1.04 (s, 3H), 1.13 (s, 3H), 2.11–2.21 (m, 2H), 2.42 (s, 2H), 4.67
1
13
tometer (KBr pellets). H NMR spectra were obtained using a (s, 1H), 6.52 (brs, 2H, D O exchangeable), 7.14–7.42 (m, 5H);
C
2
Bruker 300 MHz spectrometer in DMSO-d or CDCl using TMS NMR (75 MHz, CDCl , ppm) d 26.32, 27.65, 31.24, 35.09, 39.08,
6
3
3
as an internal reference. Melting points were determined in 49.98, 59.74, 113.09, 118.42, 125.86, 126.63, 127.54, 142.68,
À1
open capillary tubes in a Stuart BI Branstead Electrothermal Cat 158.54, 162.32, 194.24; IR (KBr disc, cm ): 3314, 3202, 2214,
no.:IA9200 apparatus and uncorrected. TEM micrograph were 1688, 1624, 1507, 1482, 1370.
characterized by Philips CM10, TGA and DTG curves were
characterized by Shimadzu 50.
2-Amino-3-cyano-4-(4-chloro phenyl)-7,7-dimethyl-5-oxo-4H-
5,6,7,8-tetrahydrobenzo[b]pyran (5b). H NMR (300 MHz,
1
CDCl , ppm) d 0.98 (s, 3H), 1.03 (s, 3H), 2.13–2.24 (m, 2H), 2.47
3
General procedure for the synthesis of 2-amino-3-cyano-4-aryl-
(s, 2H), 4.16 (s, 1H), 6.62 (brs, 2H, D
2H), 7.42 (d, 2H); C NMR (75 MHz, CDCl , ppm) d 25.63, 27.44,
31.68, 34.69, 39.98, 50.28, 60.54, 114.87, 119.62, 124.74, 127.89,
2
O exchangeable), 7.16 (d,
1
3
7
5
,7-dimethyl-5,6,7,8-tetrahydrobenzo[b]pyrans and 6-amino-
-cyano-4-aryl-1,4-dihydropyrano[2,3-c]pyrazoles
3
À1
1
3
28.32, 141.76, 159.54, 161.56, 196.76; IR (KBr disc, cm ): 3370,
178, 2198, 1678, 1620, 1507, 1490, 1384.
A mixture of aldehyde (1, 1 mmol), malononitrile (2, 2 mmol),
,3-dicarbonyl compounds [1,3-cyclohexanedione or 5,5-
1
2-Amino-3-cyano-4-(4-methyl phenyl)-7,7-dimethyl-5-oxo-4H-
dimethyl-1,3-cyclohexanedione] (3, 1 mmol) or 3-methyl-1-
phenyl-2-pyrazoline-5-one (4, 1 mmol) and NH H PO /Al O
2 3
1
5,6,7,8-tetrahydrobenzo[b]pyran (5c). H NMR (300 MHz,
4
2
4
CDCl , ppm) d 0.97 (s, 3H), 1.05 (s, 3H), 2.14 (d, 1H), 2.21 (d,
3
(0.03 g) in EtOH (96%, 3 ml) was stirred on an oil bath under
1H), 2.47–2.76 (m, 2H), 4.45 (s, 1H), 6.92 (brs, 2H, D O
2
reux condition for a suitable time (Table 1). The reaction was
monitored by TLC. Aer completion of the reaction, the reac-
tion mixture was ltered in hot condition to separate the cata-
lyst, poured into crushed ice and the solid product, which was
separated, ltered and recrystallized from ethanol to get pure
crystalline 2-amino-3-cyano-4-aryl-7,7-dimethyl-5,6,7,8-tetrahy-
drobenzo[b]pyrans and 6-amino-5-cyano-4-aryl-1,4-dihydropyr-
ano[2,3-c]pyrazoles. In separated positions, this reaction carried
1
3
exchangeable), 7.04 (d, 2H), 7.09 (d, 2H); C NMR (75 MHz,
CDCl , ppm) d 26.98, 28.34, 30.65, 33.98, 36.67, 39.08, 51.61,
1.54, 112.93, 118.82, 125.44, 126.61, 126.96, 142.64, 153.67,
3
6
1
1
À1
62.32, 194.72; IR (KBr disc, cm ): 3392, 3205, 2190, 1670,
630, 1598, 1486, 1410.
2-Amino-3-cyano-4-(3-chloro phenyl)-7,7-dimethyl-5-oxo-4H-
1
5,6,7,8-tetrahydrobenzo[b]pyran (5d). H NMR (300 MHz,
CDCl , ppm) d 0.98 (s, 3H), 1.06 (s, 3H), 2.09 (d, 2H), 2.26 (d,
ꢀ
3
out under solvent-free at 80 C.
2
7
2
1
H), 4.78 (s, 1H), 6.64 (brs, 2H, NH
.16 (m, 3H), 7.24 (s, 1H); C NMR (75 MHz, CDCl
6.30, 27.62, 31.33, 35.98, 39.43, 51.98, 59.96, 113.44, 118.19,
2
, D
2
O exchangeable), 7.09–
, ppm) d
1
3
3
Preparation of the catalyst NH
The catalyst was prepared by mixing nano a-Al
solution of NH PO
The resulting mixture was stirred for 30 min to absorb
4
H
2
PO
4
/nano a-Al
2
O
3
2
O
3
(2.5 g) with a
27.21, 129.89, 130.76, 142.76, 157.08, 162.61, 196.009; IR (KBr
À1
4
H
2
4
(0.6 g, 5 mmol) in distilled water (10 ml).
disc, cm ): 3398, 3201, 2196, 1676, 1622, 1506, 1482, 1370.
2
-Amino-3-cyano-4-(3-methoxyphenyl)-7,7-dimethyl-5-oxo-
1
NH
4
H
2
PO
4
on surface of nano alumina. Aer removal of water
4H-5,6,7,8-tetrahydrobenzo[b]pyran (5e). H NMR (300 MHz,
ꢀ
in a rotary evaporator, the solid powder was dried at 120 C for
DMSO-d , ppm) d 0.92 (s, 3H), 1.01 (s, 3H), 2.05 (d, 2H), 2.66 (d,
6
2–3 h under reduced pressure. The drying temperature was
2
7
H), 3.45 (s, 3H), 4.17 (s, 1H), 7.06 (brs, 2H, D
.13–7.26 (m, 3H), 7.34 (s, 1H); C NMR (75 MHz, DMSO-d
2
O exchangeable),
1
3
maintained below the decomposition temperatures of the salts.
6
,
+
The amount of H in the NH
4
H
2
PO
4
/nano a-Al
2
O
3
determined
ppm) d 27.30, 28.78, 32.33, 35.52, 35.58, 38.43, 50.44, 58.41,
À1
by acid base titration was 0.5 mmol g
.
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Table 4 Preparation of 6-amino-5-cyano-4-aryl-1,4-dihydropyrano[2,3-c]pyrazoles derivatives by four component reaction using NH
4 2 4
H PO /
Al as catalyst
2 3
O
ꢀ
Mp ( C)
a
Products (5 or 7)
Ar
X
Time (min)
Yield (%)
Found
Reported
6
C H
5
CN
160
78
165–166
168–170 (ref. 9)
4-ClC
6
H
4
CN
80
80
174–175
174–175 (ref. 9)
4-CH OC
3 6
H
4
CN
120
80
174–175
170–172 (ref. 9)
4
3
4
-BrC
6
H
4
CN
CN
CN
80
82
86
73
184–186
188–190
217–219
183–184 (ref. 9)
188–190 (ref. 9)
214–216 (ref. 9)
-NO
2
C
6
H
4
80
-CH
3
C
6
H
4
180
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Table 4 (Contd.)
ꢀ
Mp ( C)
a
Products (5 or 7)
Ar
X
Time (min)
Yield (%)
Found
Reported
6
4-MeOC H
4
CN
75
72
213–215
212–213 (ref. 7)
4-ClC
6
H
4
CN
80
74
236–238
234–235 (ref. 7)
4-BrC
6
H
4
CN
80
78
244–246
249–250 (ref. 7)
a
Isolated yields.
1
1
1
12.74, 120.19, 128.91, 129.63, 131.80, 144.16, 158.98, 163.61, DMSO-d
97.00; IR (KBr disc, cm ): 3370, 3180, 2185, 1660, 1624, 1509, 1H), 2.37–2.56 (m, 2H), 2.78 (s, 3H), 4.41 (s, 1H), 6.06 (brs, 2H,
6
, ppm) d 0.95 (s, 3H), 1.08 (s, 3H), 2.12 (d, 1H), 2.21 (d,
À1
1
3
492, 1380.
2
D O exchangeable), 7.35–7.58 (m, 4H); C NMR (75 MHz,
2
-Amino-3-cyano-4-(2-methyl phenyl)-7,7-dimethyl-5-oxo-4H- DMSO-d , ppm) d 25.30, 26.32, 32.33, 34.12, 36.08, 39.93, 51.64,
6
1
5
,6,7,8-tetrahydrobenzo[b]pyran (5f).
H
NMR (300 MHz, 59.96, 113.65, 121.89, 124.76, 129.03, 132.09, 142.56, 156.06,
À1
161.61, 193.64; IR (KBr disc, cm ): 3390, 3280, 2197, 1690,
623, 1595, 1472, 1389.
1
2
-Amino-3-cyano-4-(4-cyano phenyl)-7,7-dimethyl-5-oxo-4H-
1
5
,6,7,8-tetrahydrobenzo[b]pyran (5g). H NMR (300 MHz,
, ppm) d 1.02 (s, 3H), 1.08 (s, 3H), 2.28–2.32 (m, 2H), 2.46
s, 2H), 5.16 (s, 1H), 5.67 (brs, 2H, D O exchangeable), 7.43 (d,
CDCl
3
(
2
1
3
2
3
1
H), 7.77 (d, 2H); C NMR (75 MHz, CDCl , ppm) d 25.63, 26.44,
0.68, 35.69, 39.08, 51.68, 61.54, 114.87, 119.62, 121.78, 126.74,
3
27.09, 128.02, 143.56, 160.91, 162.76, 197.06; IR (KBr disc,
À1
cm ): 3470, 3278, 2198, 1670, 1620, 1509, 1498, 1381.
2
-Amino-3-cyano-4-(4-nitrophenyl)-7,7-dimethyl-5-oxo-4H-
1
5
,6,7,8-tetrahydrobenzo[b]pyran (5h). H NMR (300 MHz,
CDCl , ppm) d 1.04 (s, 3H), 1.18 (s, 3H), 2.26–2.51 (m, 2H), 2.59
s, 2H), 5.26 (s, 1H), 6.12 (brs, 2H, D O exchangeable), 7.56
3
(
2
4 2 4 2 3
Fig. 1 Reuse of the NH H PO /Al O for synthesis of 5a.
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2 3 4 2 4 2 3 4 2 4 2 3
Fig. 2 FT-IR Spectra of (a) Al O , (b) fresh NH H PO /Al O , (c) recovered NH H PO /Al O .
2
-Amino-3-cyano-4-(4-bromophenyl)-7,7-dimethyl-5-oxo-4H-
1
5
,6,7,8-tetrahydrobenzo[b]pyran (5j). H NMR (300 MHz, CDCl
ppm) d 0.96 (s, 3H), 1.01 (s, 3H), 2.12–2.21 (m, 2H), 2.37 (s, 2H),
.15 (s, 1H), 6.02 (brs, 2H, D O exchangeable), 7.46 (d, 2H), 7.78
3
,
4
2
1
3
Scheme 4 Preparation of NH
4 2
H PO
4
/Al
2
O .
3
(d, 2H); C NMR (75 MHz, CDCl , ppm) d 25.13, 27.44, 31.08,
3
3
5.76, 39.12, 50.74, 60.04, 113.45, 118.02, 123.12, 126.09,
À1
1
3
128.13, 140.76, 157.34, 160.14, 193.97; IR (KBr disc, cm ): 3325,
(
d, 2H), 8.09 (d, 2H); C NMR (75 MHz, CDCl
3
, ppm) d 26.98,
3
187, 2194, 1675, 1604, 1545, 1468, 1386.
2
1
7.44, 31.08, 35.87, 40.18, 51.88, 62.54, 113.67, 119.02, 127.74,
2
-Amino-3-cyano-4-(4-ouro phenyl)-7,7-dimethyl-5-oxo-4H-
27.97, 129.02, 144.32, 161.61, 165.78, 197.24; IR (KBr disc,
1
À1
5,6,7,8-tetrahydrobenzo[b]pyran (5k). H NMR (300 MHz,
CDCl , ppm) d 1.00 (s, 3H), 1.08 (s, 3H), 2.20–2.22 (m, 2H), 2.40
(s, 2H), 4.24 (s, 1H), 5.78 (brs, 2H, D O exchangeable), 7.17 (d,
2
2
3
cm ): 3401, 3307, 2200, 1690, 1598, 1498, 1468, 1375.
3
2
-Amino-3-cyano-4-(3-nitro phenyl)-7,7-dimethyl-5-oxo-4H-
1
5
,6,7,8-tetrahydrobenzo[b]pyran (5i). H NMR (300 MHz, CDCl
ppm) d 1.02 (s, 3H), 1.06 (s, 3H), 2.16–2.24 (m, 2H), 2.39 (s, 2H),
.84 (s, 1H), 6.09 (brs, 2H, NH , D O exchangeable), 7.19–7.32
m, 3H), 7.44 (s, 1H); C NMR (75 MHz, CDCl , ppm) d 26.32,
7.98, 31.53, 35.05, 39.73, 51.24, 59.74, 113.04, 118.19, 126.21,
3
,
1
3
H), 7.28 (d, 2H); C NMR (75 MHz, CDCl , ppm) d 26.14, 27.78,
3
0.89, 35.78, 38.12, 49.82, 61.54, 113.89, 118.98, 122.12, 127.56,
4
(
2
1
2
2
À1
1
3
129.53, 141.86, 158.54, 160.05, 195.04; IR (KBr disc, cm ): 3376,
3
3200, 2201, 1678, 1624, 1589, 1466, 1380.
2
-Amino-3-cyano-4-(2-chloro phenyl)-7,7-dimethyl-5-oxo-4H-
26.89, 130.65, 141.76, 156.08, 161.91, 193.65; IR (KBr disc,
1
À1
3
5,6,7,8-tetrahydrobenzo[b]pyran (5l). H NMR (300 MHz, CDCl ,
cm ): 3346, 3297, 2189, 1680, 1588, 1498, 1478, 1389.
4 2 4 2 3
Fig. 3 XRD patterns of NH H PO /nano-Al O .
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4 2 4 2 3
Fig. 4 TGA and DTG curves of NH H PO /nano a-Al O .
1
3
exchangeable), 7.24–7.61 (m, 4H); C NMR (75 MHz, DMSO-d6,
ppm) d 25.42, 26.41, 29.87, 31.65, 36.08, 40.03, 51.04, 60.43,
1
1
1
13.12, 120.06, 123.76, 129.03, 133.09, 140.06, 154.06, 160.32,
94.04; IR (KBr disc, cm ): 3384, 3288, 2199, 1680, 1620, 1590,
470, 1372.
À1
2
-Amino-3-ethylacetato-4-(phenyl)-7,7-dimethyl-5-oxo-4H-5,6,
1
7
,8-tetrahydrobenzo[b]pyran (5p). H NMR (300 MHz, CDCl3,
ppm) d 1.01 (s, 3H), 1.08 (s, 3H), 1.24 (t, 3H), 2.16–2.25 (m, 2H),
2
.34 (s, 2H), 4.24 (q, 2H), 4.37 (s, 1H), 5.52 (brs, 2H, D O
2
Fig. 5 TEM micrograph of NH
4
2
H PO
4
/nano a-Al
2
O .
3
13
3
exchangeable), 7.12–7.42 (m, 5H); C NMR (75 MHz, CDCl ,
ppm) d 19.12, 26.52, 27.65, 31.44, 35.56, 39.68, 50.15, 60.63,
7
1
1.47, 113.09, 126.42, 126.86, 127.03, 142.54, 156.68, 161.87,
72.42, 196.01; IR (KBr disc, cm ): 3423, 3265, 3020, 2980,
À1
ppm) d 0.97 (s, 3H), 1.02 (s, 3H), 2.08–2.22 (m, 2H), 2.42 (s, 2H),
4
4
3
1
3
.56 (s, 1H), 5.96 (brs, 2H, D O exchangeable), 7.45–7.78 (m,
2
1667, 1614, 1520, 1462, 1378.
1
3
H); C NMR (75 MHz, CDCl , ppm) d 25.56, 26.02, 32.67,
3
2-Amino-3-ethylacetato-4-(phenyl)-7,7-dimethyl-5-oxo-4H-
1
6.08, 40.65, 50.65, 60.78, 113.56, 119.87, 123.46, 129.03,
5
,6,7,8-tetrahydrobenzo[b]pyran (5q). H NMR (300 MHz,
À1
31.09, 143.12, 156.06, 160.13, 195.67; IR (KBr disc, cm ): 3382,
CDCl , ppm) d 1.04 (s, 3H), 1.09 (s, 3H), 1.12 (t, 3H), 2.26–2.35
3
312, 2191, 1664, 1617, 1585, 1470, 1389.
2
(m, 2H), 2.62 (s, 2H), 4.05 (q, 2H), 4.26 (s, 1H), 5.98 (brs, 2H, D O
1
3
2
-Amino-3-cyano-4-(2,4-dichloro phenyl)-7,7-dimethyl-5-oxo-
exchangeable), 7.32 (d, 2H), 7.56 (d, 2H); C NMR (75 MHz,
CDCl , ppm) d 19.43, 26.56, 26.94, 31.78, 36.01, 40.04, 51.25,
61.42, 70.97, 113.24, 127.42, 127.96, 128.57, 143.54, 159.68,
161.05, 171.32, 195.62; IR (KBr disc, cm ): 3412, 3258, 3020,
2986, 1664, 1612, 1568, 1489, 1389.
1
4
H-5,6,7,8-tetrahydrobenzo[b]pyran (5m). H NMR (300 MHz,
3
CDCl , ppm) d 1.01 (s, 3H), 1.12 (s, 3H), 2.13–2.22 (m, 2H), 2.47
3
À1
(
(
s, 2H), 4.45 (s, 1H), 5.85 (brs, 2H, D O exchangeable), 7.15–7.38
2
1
3
m, 3H); C NMR (75 MHz, CDCl , ppm) d 26.06, 26.42, 33.67,
3
3
1
3
5.12, 40.79, 51.45, 60.23, 113.12, 118.47, 122.12, 129.13,
30.18, 142.12, 155.45, 160.78, 193.14; IR (KBr disc, cm ): 3388,
289, 2187, 1698, 1624, 1595, 1489, 1379.
2
-Amino-3-cyano-4-(4-nitro phenyl)-5-oxo-4H-5,6,7,8-tetra-
À1
1
hydrobenzo[b]pyran (5r). H NMR (300 MHz, CDCl , ppm) d
3
2
3
(
.10–2.20 (m, 2H), 2.41–2.55 (m, 2H), 2.80–2.88 (m, 1H), 2.93–
.00 (m, 1H), 5.68 (s, 1H), 6.09 (brs, 2H, D O exchangeable), 7.32
, ppm) d 20.87,
2
-Amino-3-cyano-4-(3-hydroxy phenyl)-7,7-dimethyl-5-oxo-
2
1
1
3
4H-5,6,7,8-tetrahydrobenzo[b]pyran (5n). H NMR (300 MHz,
d, 2H), 7.84 (d, 2H); C NMR (75 MHz, CDCl
3
CDCl , ppm) d 1.05 (s, 3H), 1.14 (s, 3H), 2.12–2.23 (m, 2H), 2.44
3
27.98, 35.43, 37.61, 50.43, 61.21, 114.32, 118.76, 126.03, 126.68,
130.02, 142.02, 160.45, 163.18, 198.23; IR (KBr disc, cm ): 3388,
3345, 2219, 1687, 1598, 1490, 1468, 1389.
À1
(
(
s, 2H), 4.34 (s, 1H), 5.58 (brs, 2H, D O exchangeable), 7.01–7.33
2
m, 3H), 8.14 (brs, 1H, D O exchangeable); C NMR (75 MHz,
1
3
2
CDCl
3
, ppm) d 26.35, 26.98, 31.03, 35.67, 39.54, 51.63, 59.24,
2
-Amino-3-cyano-4-(4-cyano phenyl)-5-oxo-4H-5,6,7,8-tetra-
1
1
1
1
13.78, 118.98, 126.45, 127.76, 130.78, 140.79, 155.09, 164.13,
94.89; IR (KBr disc, cm ): 3650, 3325, 3120, 2195, 1679, 1645,
586, 1478, 1382.
hydrobenzo[b]pyran (5s). H NMR (300 MHz, CDCl , ppm) d
3
À1
2
2
(
2
.08–2.10 (m, 2H), 2.45–2.48 (m, 2H), 2.81–2.89 (m, 1H), 2.92–
.99 (m, 1H), 5.48 (s, 1H), 6.31 (brs, 2H, D O exchangeable), 7.32
, ppm) d 20.46,
7.67, 35.00, 37.19, 51.44, 60.56, 113.78, 118.09, 126.34, 126.96,
2
1
3
2-Amino-3-cyano-4-(2-methoxy phenyl)-7,7-dimethyl-5-oxo-
d, 2H), 7.74 (d, 2H); C NMR (75 MHz, CDCl
3
1
4H-5,6,7,8-tetrahydrobenzo[b]pyran (5o). H NMR (300 MHz,
À1
DMSO-d , ppm) d 0.98 (s, 3H), 1.12 (s, 3H), 2.12–2.23 (m, 2H),
6
131.34, 141.45, 161.05, 164.78, 196.01; IR (KBr disc, cm ): 3324,
3189, 2198, 1667, 1616, 1583, 1478, 1391.
2.34 (s, 2H), 3.87 (s, 3H), 4.68 (s, 1H), 6.64 (brs, 2H, D O
2
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Scheme 5 Proposed mechanisms.
À1
2
-Amino-3-cyano-4-(4-chloro phenyl)-5-oxo-4H-5,6,7,8-tetra- 129.14, 130.14, 140.05, 154.05, 162.34; IR (KBr disc, cm ): 3425,
1
hydrobenzo[b]pyran (5t). H NMR (300 MHz, CDCl
3
, ppm) d 3332, 2200, 1620, 1590, 1484, 1386.
.09–2.21 (m, 2H), 2.41–2.54 (m, 2H), 2.80–2.88 (m, 1H), 2.93–
6-Amino-3-methyl-5-cyano-4-(4-chlorophenyl)1,4-dihydro-
.00 (m, 1H), 5.58 (s, 1H), 6.09 (brs, 2H, D O exchangeable), 7.15 pyrano[2,3-c]pyrazole (6b). H NMR (300 MHz, DMSO-d
2
3
(
2
1
3
1
, ppm):
2
6
1
3
3
2
d, 2H), 7.44 (d, 2H); C NMR (75 MHz, CDCl , ppm) d 20.50, d 1.98 (s, 3H), 5.32 (s, 1H), 7.08–7.57 (m, 9H), 6.50 (brs, 2H, D O
1
3
7.55, 33.15, 37.09, 50.45, 59.13, 113.24, 118.67, 126.45, 126.06, exchangeable); C NMR (75 MHz, DMSO-d
6
, ppm) d 26.32,
À1
30.14, 140.05, 159.05, 162.34, 192.46; IR (KBr disc, cm ): 3320, 40.02, 51.35, 60.72, 113.05, 118.24, 125.09, 126.67, 126.98,
192, 2193, 1680, 1619, 1576, 1462, 1376.
128.78, 129.09, 130.65, 131.43, 141.31, 152.54, 160.01; IR (KBr
-Amino-3-methyl-5-cyano-4-(phenyl)1,4-dihydropyrano[2,3- disc, cm ): 3432, 3298, 2194, 1612, 1594, 1459, 1367.
À1
6
1
c]pyrazole (6a). H NMR (300 MHz, DMSO-d
6
): d 1.77 (s, 3H),
O exchange- pyrano[2,3-c]pyrazole (6c). H NMR (300 MHz, DMSO-d
able); C NMR (75 MHz, CDCl , ppm) d 25.02, 40.43, 50.45, d 2.01 (s, 3H), 4.89 (s, 1H), 6.05 (brs, 2H, D O exchangeable),
9.13, 113.24, 118.67, 126.45, 126.06, 127.67, 128.03, 128.98, 6.96–7.47 (m, 9H); C NMR (75 MHz, DMSO-d , ppm) d 25.01,
6-Amino-3-methyl-5-cyano-4-(4-bromophenyl)1,4-dihydro-
1
5
.16 (s, 1H), 7.28–7.48 (m, 10H), 7.78 (brs, 2H, D
2
6
, ppm):
1
3
3
2
1
3
5
6
40.76, 51.05, 61.63, 113.96, 119.04, 125.46, 126.09, 126.42,
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28.01, 129.76, 130.05, 131.57, 142.42, 151.52, 161.43; IR (KBr
6-Amino-3-methyl-5-cyano-4-(3-chlorophenyl)1,4-dihydro-
À1
1
disc, cm ): 3392, 3278, 2221, 1610, 1568, 1445, 1346.
pyrano[2,3-c]pyrazole (6k). H NMR (300 MHz, DMSO-d , ppm): d
6
6
-Amino-3-methyl-5-cyano-4-(4-methylphenyl)1,4-dihydro- 1.65 (s, 3H), 4.89 (s, 1H), 6.76 (brs, 2H, D O exchangeable), 7.43–
2
1
13
pyrano[2,3-c]pyrazole (6d). H NMR (300 MHz, DMSO-d , ppm): 7.84 (m, 8H), 8.65 (s, 1H); C NMR (75 MHz, DMSO-d , ppm) d
6
6
d 1.01 (s, 3H), 2.46 (s, 3H), 5.12 (s, 1H), 5.98 (brs, 2H, D
exchangeable), 7.11–7.79 (m, 9H); C NMR (75 MHz, DMSO-d
ppm) d 25.18, 26.56, 41.04, 50.25, 60.63, 113.24, 118.04, 125.13, 160.21; IR (KBr disc, cm ): 3421, 3318, 2211, 1605, 1576, 1492,
2
O
26.07, 39.14, 50.24, 60.23, 113.08, 118.14, 125.79, 126.54, 126.08,
1
3
6
,
127.12, 128.02, 128.67, 129.89, 130.78, 131.75, 140.67, 152.67,
À1
1
1
1
26.45, 127.52, 128.18, 129.89, 130.68, 131.43, 141.67, 153.69, 1393.
À1
60.11; IR (KBr disc, cm ): 3413, 3321, 2196, 1620, 1589, 1448,
6-Amino-3-methyl-4-(4-methoxyphenyl)-1,4-dihydro-pyrano
1
381.
6
[2,3-c]pyrazole-5-carbonitrile (7a). H NMR (300 MHz, DMSO-d ,
6
-Amino-3-methyl-5-cyano-4-(4-methoxyphenyl)1,4-dihydro- ppm): d 1.79 (s, 3H), 3.45 (s, 3H), 4.56 (s, 1H), 6.88 (brs, 2H, D O
2
1
pyrano[2,3-c]pyrazole (6e). H NMR (300 MHz, DMSO-d , ppm): exchangeable), 7.10 (d, 2H), 7.19 (d, 2H), 12.01 (s, 1H, D O
d 1.68 (s, 3H), 3.89 (s, 3H), 5.76 (s, 1H), 6.45 (brs, 2H, D
exchangeable), 7.09–7.98 (m, 9H); C NMR (75 MHz, DMSO-d
ppm) d 25.32, 36.12, 40.04, 51.05, 59.61, 113.78, 119.14, 125.79, 136.07, 141.64, 155.22, 161.35; IR (KBr disc, cm ): 3483, 3254,
6
2
1
3
2
O
exchangeable); C NMR (75 MHz, DMSO-d , ppm) d) d 10.22,
6
1
3
6
,
35.17, 36.01, 57.64, 97.82, 121.31, 126.04, 128.64, 136.19,
À1
1
1
1
26.54, 127.02, 128.38, 129.11, 130.18, 131.67, 140.67, 151.67, 2191, 1641, 1608, 1492, 1390.
À1
58.52; IR (KBr disc, cm ): 3389, 3292, 2197, 1618, 1576, 1454,
372.
6-Amino-3-methyl-4-(4-chloroxyphenyl)-1,4-dihydro-pyrano
[2,3-c]pyrazole-5-carbonitrile (7b). H NMR (300 MHz, DMSO-
1
6
-Amino-3-methyl-5-cyano-4-(3-nitrophenyl)1,4-dihydro- d , ppm): d 1.78 (s, 3H), 4.86 (s, 1H), 6.78 (brs, 2H, D O
6
2
1
pyrano[2,3-c]pyrazole (6f). H NMR (300 MHz, DMSO-d , ppm): exchangeable), 7.18 (d, 2H), 7.45 (d, 2H), 12.22 (s, 1H, D O
d 1.79 (s, 3H), 5.16 (s, 1H), 6.05 (brs, 2H, D O exchangeable), exchangeable); C NMR (75 MHz, DMSO-d , ppm) d 10.02,
2
6
.19–7.68 (m, 8H), 8.01 (s, 1H); C NMR (75 MHz, DMSO-d
ppm) d 25.67, 41.12, 51.61, 61.05, 113.78, 119.14, 125.79, 126.54, 135.19, 140.64, 155.64, 161.08; IR (KBr disc, cm ): 3481, 3252,
6
2
1
3
1
3
7
6
,
33.62, 55.17, 96.38, 120.71, 128.05, 129.36, 132.68, 133.30,
À1
1
1
1
26.98, 127.32, 128.12, 128.67, 129.34, 130.78, 131.05, 140.67, 2187, 1643, 1593, 1492, 1410.
À1
54.67, 159.89; IR (KBr disc, cm ): 3420, 3310, 2198, 1618,
598, 1568, 1490, 1386.
6-Amino-3-methyl-4-(4-bromophenyl)-1,4-dihydro-pyrano
[2,3-c]pyrazole-5-carbonitrile (7c). H NMR (300 MHz, DMSO-
1
6
-Amino-3-methyl-5-cyano-4-(2-chlorophenyl)1,4-dihydro- d , ppm): d 1.75 (s, 3H), 4.81 (s, 1H), 6.48 (brs, 2H, D O
6
2
1
pyrano[2,3-c]pyrazole (6g). H NMR (300 MHz, DMSO-d , ppm): exchangeable), 7.09 (d, 2H), 7.32 (d, 2H), 12.12 (s, 1H, D O
d 1.09 (s, 3H), 5.01 (s, 1H), 6.65 (brs, 2H, D O exchangeable), exchangeable); C NMR (75 MHz, DMSO-d , ppm) d 10.12, 33.62,
2
6
.01–7.78 (m, 9H); C NMR (75 MHz, DMSO-d
9.46, 49.01, 60.14, 113.08, 118.14, 125.09, 126.78, 127.08, 155.89, 161.98; IR (KBr disc, cm ): 3444, 3238, 2195, 1637, 1600,
27.32, 128.45, 128.98, 129.89, 131.12, 131.95, 139.07, 156.04, 1491, 1394.
6
2
13
1
3
7
3
1
1
1
6
, ppm) d 25.12, 55.69, 96.23, 120.01, 128.45, 129.79, 132.54, 133.30, 135.21, 140.54,
À1
À1
60.34; IR (KBr disc, cm ): 3422, 3318, 2195, 1617, 1568, 1494,
375.
6
-Amino-3-methyl-5-cyano-4-(2,4-dichlorophenyl)1,4-dihydro-
1
Conclusion
pyrano[2,3-c]pyrazole (6h). H NMR (300 MHz, DMSO-d , ppm):
d 1.78 (s, 3H), 5.16 (s, 1H), 7.32–7.42 (m, 5H), 7.50 (brs, 2H, D O
2
6
In conclusion, we have reported a simple new catalytic
method for the synthesis of 2-amino-3-cyano-4-aryl-7,7-
dimethyl-5,6,7,8-tetrahydrobenzo[b]pyrans and 6-amino-5-
cyano-4-aryl-1,4-dihydropyrano[2,3-c]pyrazoles
condensation reaction of aldehydes, malononitrile, and 1,3-
dicarbonyl compounds (1,3-cyclohexanedione or 5,5-dimethyl-
1
3
exchangeable), 7.63 (s, 1H), 7.78–7.80 (d, 2H); C NMR (75 MHz,
DMSO-d , ppm) d 25.07, 40.34, 50.43, 60.01, 113.45, 118.64,
25.12, 126.14, 126.78, 127.42, 128.11, 128.67, 129.89, 130.43,
31.45, 141.67, 153.43, 160.32; IR (KBr disc, cm ): 3450, 3320,
200, 1614, 1590, 1482, 1390.
6
1
1
2
by
one-pot
À1
6
-Amino-3-methyl-5-cyano-4-(4-nitrophenyl)1,4-dihydropyr-
1
,3-cyclohexanedione) or 3-methyl-1-phenyl-2-pyrazoline-5-one,
respectively, using NH PO /Al as an reusable, safe and
green heterogeneous catalyst. The notable advantages of this
methodology are operational simplicity, generality,
1
ano[2,3-c]pyrazole (6i). H NMR (300 MHz, DMSO-d , ppm): d
.03 (s, 3H), 5.87 (s, 1H), 6.45 (brs, 2H, D
.98 (m, 9H); C NMR (75 MHz, DMSO-d , ppm) d 25.01, 41.56,
1.65, 61.78, 113.76, 119.67, 125.76, 126.49, 126.89, 128.69,
6
4
H
2
4
2 3
O
2
7
5
1
2
O exchangeable), 7.43–
1
3
6
inexpensive, availability of reactants, short reaction times and
easy work-up.
29.06, 130.71, 131.07, 141.42, 153.64, 160.02; IR (KBr disc,
À1
cm ): 3410, 3317, 2193, 1620, 1586, 1570, 1493, 1393.
6
-Amino-3-methyl-5-cyano-4-(4-hydroxyphenyl)1,4-dihydro-
1
pyrano[2,3-c]pyrazole (6j). H NMR (300 MHz, DMSO-d , ppm):
6
d 1.89 (s, 3H), 5.17 (s, 1H), 6.15 (brs, 2H, D O exchangeable),
2
Acknowledgements
1
3
7.13–7.87 (m, 9H), 8.24 (brs, 1H, D
2
O exchangeable); C NMR
(
75 MHz, DMSO-d , ppm) d 25.78, 41.96, 51.02, 60.08, 113.54, Authors wish to dedicate the present work to Professor M.A.
6
1
1
2
18.43, 125.92, 126.09, 126.59, 128.44, 129.32, 130.32, 131.49, Zolgol, of Bu-Ali Sina University, Hamadan, Iran, for his
40.42, 152.21, 160.22; IR (KBr disc, cm ): 3654, 3379, 3289, remarkable lifetime contributions to research in chemistry and
À1
198, 1610, 1576, 1471, 1382.
his constant inspirations given to his students.
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1
9 I. M. Wang, J. H. Shao, H. Tian, Y. H. Wang and B. Liu, J.
Fluorine Chem., 2006, 127, 97.
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