DOI: 10.17344/acsi.2016.2634
Acta Chim. Slov. 2016, 63, 781-789
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Scientific paper
Nano-Rb2HPW12O40 as an Efficient and Novel Catalyst for One-Pot Synthesis of P-Amino Ketones
Fatemeh Moradgholi,* Jalil Lari, Mahnaz Vahidi Parsa and Mehran Mirkharrazi
Chemistry Department, Payame Noor University, 19395-4697 Tehran, I. R. of Iran.
* Corresponding author: E-mail: fateme.moradgholi@ gmail.com Tel.: 009154413623
Received: 28-05-2016
Abstract
The aim of the research described was to study Rb2HPW12O40 as a green and heterogeneous catalyst for the Mannich reaction. One-pot multi-component condensation of an aldehyde, an amine and a ketone at ambient temperature affords the corresponding P-amino ketones using novel nano-sized Rb2HPW12O40. Simple purification, short reaction time and high yield are some of the advantages of this reaction. Also, the catalyst can be readily isolated. The nano catalyst Rb2HPW12O40 has been characterized by Fourier transform infrared spectroscopy, X-ray powder diffraction and scanning electron microscopy.
Keywords: Mannich reaction, P-amino ketones, hetero poly acid, one-pot reaction
1. Introduction
Mannich reactions are one of the most important carbon-carbon bond forming reactions in synthetic organic chemistry1'2 because they provide synthetically and biologically important P-amino ketones that are important intermediates. These products can be used for the synthesis of amino alcohols' peptides and lactams' amino acids and various natural products.3 P-Amino ketones are generally obtained by the condensation of a carbonyl compound with an aldehyde and an amine using various Lewis or Br0nsted acid catalysts, such as HClO4-SiO2'4 CAN,5 CeCl3-7H2O'6 BiCl3,7 AuCl3-PPh3'8 nano-TiO2,2 ionic liquids,10'11 sulphamic acid,12'13 Fe(Cp)2PF6,14 Cu-nanopar-ticles,15 [Re(PFO)3],16 PEG-SO3H17 and ZSM-5-SO3H,18 etc.
However, many of these methods have some drawbacks, such as low yields, long reaction times, harsh reaction conditions, toxicity, and difficulties in work-up as well as the problem of catalysts moisture sensitivity. Therefore, there is a further need to find appropriate mild and efficient methods for the preparation of P-amino ketones.
In the recent years, heterogeneous solid catalysts have been used in various organic reactions, as they possess a number of advantages.19 20 Among the heterogeneous solid acids, heteropoly acids (HPAs) due to their stronger
acidity, have been extensively studied as acid catalysts for many reactions, such as the synthesis of trioxanes,21 alkylation of benzene with olefins,22 and gas-phase selective oxidation of various organic substrates. Heteropoly acids have many advantages over other acid catalysts, including being non-corrosive, environmentally benign and possessing superacidic properties.
Thus, in this research we have introduced a novel nano-sized Rb2HPW12O40 of the Keggin series which is stable and efficient heterogeneous catalyst in organic synthesis, for example for the described one-pot, three-component reaction of an aldehyde, an amine and a ketone for the preparation of P-amino carbonyl compounds.
2. Experimental
2. 1. General
Chemicals were purchased from Merck and Fluka chemical companies. IR spectra were run on a Shimadzu model 8300 FT-IR spectrophotometer. NMR spectra were recorded on a Bruker Avance DPX-250. The purity of the products and the progress of the reactions were determined by TLC on silica-gel polygram SILG/UV254 plates. Elemental analysis was performed on a Thermo Finnigan (San Jose, CA, USA) Flash EA micro analyzer.
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2. 2. Preparation of Rb2HPW12O40
To a solution of H3PW12O40 (1 eq, 5 mmol) in H2O (20 mL) was added dropwise RbCl2 (2 eq, 10 mmol) in H2O (20 mL) during stirring for 20 min at room temperature. After completion of the addition, the mixture was stirred for additional 2 h. Finally, the precipitate was filtered, washed with distilled water, and dried to afford nano-sized Rb2HPW12O40.
2. 3. General Procedure for the Synthesis of P-Amino Ketones
To the mixture of the aromatic aldehyde (2 mmol), aromatic amines (2 mmol), and cyclohexanone (2.2 mmol, 0.21 g) was added nano-Rb2HPW12O40 (0.2 g). The reaction mixture was stirred at room temperature for the appropriate time (Table 2). After completion of the reaction, the mixture was diluted with hot ethanol (15 mL) and the catalyst was separated by filtration. Evaporation of the solvent under reduced pressure gave the product.
3. Results and Discussion
As it was already mentioned, the nano-sized Rb2HPW12O40 is a new, highly efficient Lewis acid catalyst which can be used for the Mannich reaction.
3. 1. Catalyst Characterization
Rb2HPW12O40 was prepared by using the co-precipitation technique. In order to evaluate the incorporation of RbCl2 and H3PW12O40, the prepared nano-sized Rb2HPW12O40 was characterized by powder X-ray diffraction (XRD), FT-IR spectra and SEM technique. Studies have shown that the absorption bands of Kegging structural type appear in the 700-1000 cm1. The characteristic absorption bands in the catalyst spectrum appeared at 1080, 985, 890, and 810 cm-1 that are assigned to P-O; (i: internal), W = Ot (t: terminal), interoctahedral W-Oe-W (e: edge-sharing), and W-Oc-W (c: corner-sharing) bands, respectively. The appearance of these vibrational bands in the catalyst confirms Keggin structure of Rb2HPW12O40. In addition, the replacement of the proton with rubidium ions reduced the intensity of the absorption band at 1620 cm-1. These results support the successful preparation of the catalyst.
The XRD spectrum of the Rb2HPW12O40 is shown in Fig. 2. The patterns show the presence of a broad peak around 26 = 22°. Also, the crystal size of the nano-Rb2HPW12O40 was determined from the X-ray patterns using the Debye-Scherrer formula given as t = 0.9X/B1/2 cos 6, where t is the average crystal size, X the X-ray wavelength used (1.54 À), B1/2 the angular line width at a half maximum intensity and 6 the Bragg's angle. The average crystal size of the nano-Rb2HPW12O40 for 26 = 26.24° is calculated to be around 31.94 nm.
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Fig. 2. The XRD of nano-Rb2HPW12O40
Fig. 3. The SEM image of nano-Rb2HPW12O40
Scanning electron microscopy (SEM) image of the nano-Rb2HPW12O40 catalyst is shown in Fig. 3. SEM analysis of the catalyst reveals the spherical nano-Rb2HPW12O40 with an average size 30-60 nm.
3. 2. Catalytic Studies
In this work, nano-Rb2HPW12O40 has been successfully used as the catalyst for one-pot reaction of substituted anilines and benzaldehydes with cyclohexanone. In order to optimize the reaction conditions, initially we chose the reaction of aniline (2 mmol, 0.18 mL) and benzaldehyde (2 mmol, 0.2 mL) with cyclohexanone (2.2 mmol,
0.23	mL) as a reaction model (Scheme 1). Reaction was screened in different solvents such as CH3CN, CH2Cl2, CH3Cl and EtOH as well as under solvent-free conditions at room temperature. The results are summarized in Table
1.	As shown in Table 1, EtOH provided excellent yield in short time, whereas CH3CN, CH3Cl and CH2Cl2 afforded lower yields.
Furthermore, the reaction was carried out in the presence of various amounts of catalyst (Table 1, entries 5-8). The condensation reaction did not proceed in the absence of the catalyst. However, in the presence of nano-si-zed Rb2HPW12O40 the reaction is occurring towards the desired product. As the results show, the best outcome was obtained with the use of 0.1 g Rb2HPW12O40 in ethanol at room temperature. Lower amount of the catalyst decreased the yield and increase of the anount of nano-Rb2HPW12O40 did not improve remarkably the results of the reaction.
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Table 1. Optimization of the reaction conditions'3'
fl 9	O vjO
ô^c^-Arifo
Entry	Solvent	Catalyst (g)	Time [h]	Yield [%]
1	ch3cn	Rb2HPW12O40 (0.1)	1:10	75
2	ch2cl2	Rb2HPW12O40 (0.1)	1:15	70
3	CH3Cl	R^HPW^O^ (0.1)	1	80
4	solvent-free	R^HPW^O^ (0.1)	0.25	90
5	EtOH	R^HPW^O^ (0.1)	0.25	97
6	EtOH	Rb2HPW12O40 (0.05)	0.42	95
7	EtOH	Rb2HPW12O40 (0.025)	0.84	90
8	EtOH	Rb2HPW12O40 (0.15)	0.23	97
[a] Reaction conditions: solvent (1 mL), room temperature, benzaldehyde (1 mmol), aniline (1 mmol), cyclohe-xanone (1.1 mmol).
In order to evaluate the generality of this new protocol, the reactions of different aromatic aldehydes, anilines and cyclohexanone were carried out at room temperature in ethanol as the solvent. The results are summarized in Table 2. In all cases P-amino ketone derivatives were obtained in good yields. Under the optimized reaction conditions the electron-donating groups were observed to accelerate the reaction compared to electron-withdrawing groups (Scheme 1).
The syn/anti ratio was determined by NMR spectroscopy and by comparing our data with that of known compounds reported in the literature,23'24 by using the coupling constants of the vicinal protons adjacent to C=O and NH. In general, the coupling constant of the anti isomer is higher than that of the syn isomer. Data showed that the Mannich reaction exhibited excellent anti selectivity in the presence of nano-Rb2HPW12O40 except for the reactions of 4-nitroben-zaldehyde with m-toluidin, p-toluidin and 4-chloroanilin.
1	2	3
X: H, 4-OH, 4-CI, 4-N02
Y: H, 4-Me, 4-CI, 3-Me
Scheme 1
3. 2. 1. Physical and spectroscopic data of selected compounds
2-(Phenyl(phenylamino)methyl)cyclohexanone (Table 2, 4a): Yield: 97%, white solid, syn/anti:1/99, FT-IR: vmax (KBr): 3329 (NH stretch), 1701 (C=O stretch) cm1, 1H NMR (250 MHz, CDCl3): 5 1.55-1.92 (m, 6H, 3CH2), 2.25-2.44 (m, 2H, 2-CH), 2.7-2.8 (m, 1H, 6-CH), 4.67 (d, J = 7.0 Hz, 0.99H, 8-CH), 4.81 (d, J = 4.38 Hz, 0.01H, 8-CH), 7.07-7.21 (m, 5H, CH Ar), 7.23-7.55 (m, 5H, CH Ar) ppm; 13C NMR (CDCl3): 5 23.67, 27.92,31.31, 41.79 (2-C), 57.5 (8-C), 57.97 (6-C), 113.63, 117.51, 127.18,
128.49, 129.08, 130.41, 141.76, 141.29, 212.83 (1-C) ppm. Anal. Calcd for C19H21NO (279.36): C, 81.68; H, 7.58; N, 5.01. Found: C, 881.49; H, 7.69; N, 4.95.
2-((p-Toluidino)(phenyl)methyl)cyclohexanone (Table 2, 4b): Yield: 92%, white solid, syn/anti: 7/93, FT-IR: vmax (KBr): 3332 (NH stretch), 1708 (C=O stretch) cm1, 1H NMR (250 MHz, CDCl3): 5 1.62-1.90 (m, 6H, 3CH2), 2.23-2.41 (m, 2H, 2-CH2), 2.45 (s, 3H, CH3), 2.7-2.8 (m, 1H, 6-CH), 4.63 (d, J = 5.0 Hz, 0.93H, 8-CH), 4.79 (d, J = 3.5 Hz, 0.07 H, 8-CH), 6.40-6.53 (m, 2H, 12,16-CH Ar),
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Table 2: Synthesis of p-amino carbonyl derivatives with nano-Rb2HPW12O40
Entry	X
Y
Product
Time (min)	Yield (%)	m.p. (ref.)
H
H
15
97
126-128 [18]
H
4-Me
XT" 6^0
O KN
90
92
119-120 [25]
H
3-Me
O HN-^^-Me
(Yo
4c
10
93
125-127 [27]
H
4-Cl
XX
<yo
O HN
10
94
134-136 [18]
H
3-Cl
o hm'C^CI
6^0
4e
50
91
129-131 [18]
6	4-OH
4-Cl
XT'
O HN-
c^a
4Í
105
90
195-197
7	4-OH	4-Me

O HN
45
89
200-201
8	4-OH
H
,X)
cYa
0 UN
4h
105
88
177-179
9	4-OH	3-Me
O HN-^^Me
cra„u
105
90
181-183
1
2
3
4
5
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Entry
X
Y
Product
Time (min)	Yield (%)
m.p. (ref.)
10
4-Cl
H
JO
0 HN
50
95
133-135 [28]
11
4-Cl
3-Me
XX
360
96
125-127 [29]
12
4-Cl
4-Cl
90
90
135-137 [30]
13
4-Cl
4-Me
• JCr'
<ya
4m
60
93
122-124 [4]
14	4-NO2	3-Me
O hnXXMe
30
70
165-167 [29]
15
4-NO
4-Cl
6*a
O HN
4o
75
75
165-167 [26]
16	4-NO2	4-Me
£r
0 HN
4p
100
71
165-167 [30]
6.82-6.97 (m, 2H, 13,15-CH Ar), 7.18-7.45 (m, 5H, CH Ar) ppm. Anal. Calcd for C20H23NO: C, 81.87; H, 7.90; N, 4.77. Found: C, 81.33; H, 8.13; N, 4.61.
2-((m-Toluidino)(phenyl)methyl)cyclohexanone (Table 2, entry 4c): Yield: 93%, Cream solid; syn/anti: 0/100, FT-IR: vmax (KBr): 3382 (NH stretch), 1693 (C=O stretch) cm-1, 1H NMR (300 MHz, CDCl3): 5 1.61-2.08 (m, 6H, 3CH2), 2.21 (s, 3H, CH3), 2.23-32.48 (m, 2H, 2-CH2), 2.79-2.86 (m, 1H, 6-CH), 4.84 (d, J = 6.0 Hz, 1H, 8-CH), 6.36-6.52 (m, 3H, CH Ar), 6.97-7.02 (m, 1H, 13-CH Ar), 7.21-7.40 (m, 5H, CH Ar) ppm. Anal. Calcd for C20H23NO: C, 81.87; H, 7.90; N, 4.77. Found: C, 80.98; H, 8.19; N, 4.52. MS (EI) m/z 293 (M+).
2-((4-Chlorophenylamino)(phenyl)methyl)cyclohexanone (Table 2, 4d): Yield: 94%, White solid; syn/anti: 0/100, FT-IR: vmax (KBr): 3379 (NH stretch), 1705 (C=O stretch) cm-1, 1H NMR (300 MHz, CDCl3): 1.71-1.96 (m, 6H, 3CH2), 2.36-2.40 (m, 1H, 2-CH2), 2.54-2.58 (m, 1H, 2-CH2), 2.84-2.88 (m, 1H, 6-CH), 3.86 (br, NH), 4.23 (m, 1H, 8-CH), 6.93 (d, J = 8.4 Hz, 2H, 12,16-CH Ar), 7.16-7.17 (m, 5H, CH Ar), 7.36 (d, J = 8.4 Hz, 2H, 13,15-CH Ar) ppm. Anal. Calcd for C19H20NOCl: C, 72.72; H, 6.42; N, 4.46. Found: C, 73.98; H, 6.74; N, 4.01.
2-((3-Chlorophenylamino)(phenyl)methyl)cyclohexa-none (Table 2, 4e): Yield: 91%, Cream solid; syn/anti: 0/100, FT-IR: vmax (KBr): 3340 (NH stretch), 1701 (C=O
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stretch) cm-1, 1H NMR (300 MHz, CDCl3): 1.69-2.01 (m, 6H, 3CH2), 2.31-2.47 (m, 2H, 2-CH2), 2.76-2.82 (m, 1H, 6-CH2), 41.58 (d, J = 6.6 Hz, 1H, 8-CH), 4.92 (br, NH), 6.41-6.45 (m, 1H, 12-CH Ar), 6.53-6.56 (m, 1H, 16-CH Ar), 6.53-6.56 (m, 1H, 14-CH Ar), 6.59-6.63 (m, 1H, 13-CH Ar), 6.96-7.01 (m, 1H, 20-CH Ar), 7.24-7.40 (m, 4H, CH Ar) ppm. Anal. Calcd for C19H20NOCl: C, 72.72; H, 6.42; N, 4.46. Found: C, 72.65; H, 634; N, 4.65.
2-((p-Chlorophenylamino)(4-hydroxyphenyl)methyl) cyclohexanone (Table 2, 4f): Yield: 90%, Yellowish solid; syn/anti: 0/100, FT-IR: vmax (KBr): 3328 (NH, OH stretch), 1654 (C=O stretch) cm-1, 1H NMR (300 MHz, CDCl3): 1.69-1.99 (m, 6H, 3CH2), 2.49-2.58 (m, 2H, 2-CH2), 2.84-2.95 (m, 1H, 6-CH), 3.68 (br, NH), 4.24 (s, 1H, 8-CH), 6.64 (d, J = 8.7 Hz, 2H, CH Ar), 7.13-7.17 (m, 2H, CH Ar), 7.36 (d, J = 8.4 Hz, 2H, CH Ar), 7.80 (d, J = 8.4 Hz, 2H, CH Ar), 8.37 (s, OH) ppm. Anal. Calcd for C19H20NOCl: C, 69.19; H, 6.11; N, 4.25. Found: C, 68.93;
H,	6.33; N, 4.29. MS (EI) m/z 329 (M+).
2-((p-Toluidino)(4-hydroxyphenyl)methyl)cyclohexa-none (Table 2, 4g): Yield: 89%, Yellow solid; syn/anti: 0/100, FT-IR: vmax (KBr): 3200 (NH, OH stretch), 1705 (C=O stretch) cm-1, 1H NMR (300 MHz, CDCl3):
I.79-1.98	(m, 6H, 3CH2), 2.37 (s, 3H, CH3), 2.48-2.57 (m, 2H, 2-CH), 2.83-2.88 (m, 1H, 6-CH), 4.24 (s, 1H, 8-CH), 6.63 (d, J = 8.7 Hz, 2H, 12,16-C H Ar), 6.95 (d, J = 8.7 Hz, 2H, 19,21-C H Ar), 7.11-7.16 (m, 2H, 13,15-C H Ar), 7.11-7.16 (m, 2H, 18,22-C H Ar), 8.39 (s, OH) ppm. Anal. Calcd for C20H23NO2: C, 77.64; H, 7.49; N, 4.53. Found: C, 77.18; H, 7.31; N, 4.26. MS (EI) m/z 309 (M+).
2-((m-Toluidino)(4-hydroxyphenyl)methyl)cyclohexa-none (Table 2, 4i): Yield: 90%, orange solid, syn/anti: 0/100, FT-IR: vmax (KBr): 3200 (NH and OH stretch), 1654 (C=O stretch) cm-1; 1H NMR (CDCl3): 5 1.74-1.79 (m, 2H, CH2), 1.87-1.91 (m, 2H, CH2), 2.12-2.67 (m, 2H, CH2), 2.37 (s, 3H, CH3), 2.54 (t, J = 6.75 Hz, 2H, 2-CH), 2.892-2.85 (m, 1H, 6-CH), 4.21 (s, 1H, 8-CH), 6.83-6.89 (m, 2H, 12,16-CH Ar), 7.01-7.05 (m, 1H, 14-CH Ar), 7.20-7.38 (m, 3H, 19,21,13-CH), 7.75 (d, J = 8.5 Hz, 2H, 18,21-CH), 8.37 (s, OH) ppm. 13C NMR (CDCl3): 5 21.39, 23.15, 23.74, 28.93, 40.07 (2-C), 55.3 (8-C), 56.7 (6-C), 115.52, 115.99, 117.97, 121.63, 126.64, 129.03, 130.98, 132.58, 136.52, 160.65 (20-C), 220 (1-C) ppm. Anal. Calcd for C^H^NO^ C, 77.64; H, 7.48; N, 10.34. Found: C, 77.85; H, 7.62; N, 4.52. MS (EI) m/z 309 (M+).
2-((p-Toluidino)(4-chlorophenyl)methyl)cyclohexano-
ne (Table 2, 4m): Yield: 93%, orange solid, syn/anti: 63/37, FT-IR: vmax (KBr): 3367 (NH stretch), 1697 (C=O stretch) cm-1,1H NMR (250 MHz, CDCl3): 1.59-1.92 (m, 3H, CH2), 1.94-2.05 (m, 3H, CH2), 2.17 (s, 3H, CH3), 2.26 (m, 2H, 2-CH), 2.81-2.85 (m, 1H, 6-CH), 4.68 (^ J
= 4.25 Hz, 0.63H, 8-CH), 4.82 (d, J = 5.25 Hz, 0.37H, 8-CH), 6.41 (d, J = 8.25 Hz, 2H, 12,16-CH Ar), 6.89 (d, J = 8.25 Hz, 2H, 13,15-CH Ar), 7.55 (d, J1 = 8.75 Hz, J2 = 4.75 Hz, 18,22-CH Ar), 8.14 (d, J = 8.75 Hz, 2H, 10,21-CH Ar) ppm. Anal. Calcd for C20H22ClNO2: C, 73.27; H, 6.76; N, 4.27. Found: C, 73.48; H, 643; N, 4.21.
2-((4-Chlorophenyl)(4-chlorophenylamino)methyl) cyclohexanone (Table 2, 4l): Yield: 90%, White solid, syn/anti: 0/100, FT-IR: vmax (KBr): 3409.9 (NH stretch), 1701.1 (C=O stretch) cm-1; 1H NMR (CDCl3): 5 1.70-1.96 (m, 6H, 3CH2), 2.31-2.43 (m, 2H, 2-CH), 2.73 (m, 1H, 6-CH), 4.51 (d, J = 6.0 Hz, 1H, 8-CH), 6.41 (d, J = 8.0 Hz, 2H, 12,16-CH Ar), 7.0 (d, J =7.75 Hz, 2H, 18,22-CH Ar), 7.27-7.33 (m, 4H, CH Ar) ppm. Anal. Calcd for C19H19Cl2ON: C, 65.53; H, 5.50; N, 4.02. Found: C, 65.777; H, 5.64; N, 4.13. MS (EI) m/z 347 (M+).
2-((m-Toluidino)(4-chlorophenyl)methyl)cyclohe-xanone (Table 2, 4k): Yield: 96%, beige solid, syn/anti: 0/100, FT-IR: vmax (KBr): 3348 (NH stretch), 1701 (C=O stretch) cm-1; 1H NMR (CDCl3): 5 1.71-1.92 (m, 6H, 3CH2), 2.19 (S, 3H, CH3), 2.31-2.54 (m, 2H, 2-CH), 2.87-2.89 (m, 1H, 6-CH), 4.59 (d, J = 6.25 Hz, 1H, 8-CH), 6.28-6.36 (m, 2H, 12,16-CH Ar), 6.47 (d, J = 7.25 Hz, 1H, 14-CH Ar), 6.95 (t, J = 7.75 Hz, 1H, 13-CH Ar), 7.25-7.38 (m, 4H, CH Ar) ppm; 13C NMR (CDCl3): 5 21.56, 23.92, 27.82, 31.44 (2-C), 41.98 (8-C), 57.33 (6-C),
110.47,	114.50, 118.70, 128.58, 128.99, 132.0, 138.86,
140.48,	146.99 (10-C), 212.43 (1-C) ppm. Anal. Calcd for C20H22ClNO (327.85): C, 73.27; H, 6.76; N, 4.27. Found: C 73.01; H, 6.81; N, 4.39. MS (EI) m/z 327 (M+).
2-((m-Toluidino)(4-nitrophenyl)methyl)cyclohexanone (Table 2, 4n): Yield: 70%, Yellow solid, syn/anti: 36/64, FT-IR: vmax (KBr): 3382.9 (NH stretch), 1693.2 (C=O stretch) cm-1; 1H NMR (CDCl3): 5 1.57-1.75 (m, 3H, CH2), 1.85-2.06 (m, 3H, CH2), 2.19 (s, 3H), 2.31-2.41 (m, 2H, 2-CH), 2.81-2.85 (m, 1H, 6-CH), 4.69 (d, J = 5.0 Hz, 0.64H, 8-CH), 4.84 (d, J = 4.25 Hz, 0.36H, 8-CH), 6.27 (d, J = 8.0 Hz, 2H, 12,16-CH Ar), 6.49 (d, J = 6.5 Hz, 1H, 14-CH Ar), 6.96 (t, J = 7.75 Hz, 1H, 13-CH Ar), 7.53-7.58 (m, 2H, 18,22-CH Ar), 8.15 (d, J = 8.75 Hz, 2H, 19,21-CH Ar) ppm; 13C NMR (CDCl3): 5 21.54, 24.46, 24.93, 27.03, 27.75, 32.0, 42.39, 42.44, 56.23, 57.06, 57.17, 57.75, 110.37, 110.95, 114.38, 114.96,
119.08,	119.37, 123.66, 128.19, 128.59, 129.03, 129.13,
139.9,	146.65, 150.0, 160.38, 160.48, 211.08 (1-C), 212.36 (1-C) ppm. Anal. Calcd for C^H^N^: C, 71.41; H, 5.98; N, 8.32. Found: C, 71.24; H 5.87; N, 8.04.
2-((4-Chlorophenylamino)(4-nitrophenyl)methyl) cyclohexanone (Table 2, 4o): Yield: 75%, white solid, syn/anti: 42/58, FT-IR: vmax (KBr): 3200 (NH stretch), 1654 (C=O stretch) cm1; mH NMR (CDCl3): 5 1.58-1.74 (m, 3H, CH2), 1.92-2.05 (m, 3H, CH2), 2.26-2.47 (m, 2H,
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2-CH), 2.81-2.85 (m, 1H, 6-CH), 4.62 (d, J = 4.75 Hz, 0.58H, 8-CH), 4.79 (d, J = 3.5 Hz, 0.42H, 8-CH), 6.41 (d, J = 8.75 Hz, 2H, 12,16-CH Ar), 7.02 (d, J = 8.75 Hz, 2H, 13,15-CH Ar), 7.53 (dd, J1 = 8.75 Hz, J2 = 3.5 Hz, 2H, 18.22-CH Ar), 8.15 (d, J = 8.75 Hz, 2H, 19,21-CH Ar) ppm. Anal. Calcd for C19H19ClN2O3: C, 63.60; H, 5.34; N, 7.81. Found: C, 63.98; H, 5.84; N, 7.54.
2-((p-Toluidino)(4-nitrophenyl)methyl)cyclohexanone
(Table 2, 4p): Yield: 71%, Yellow solid, syn/anti: 37/63, FT-IR: vmax (KBr): 3367 (NH stretch), 1697 (C=O stretch) cm-1; 1H NMR (CDCl3): 1.59-1.92 (m, 3H, CH2), 1.94-2.05 (m, 3H, CH2), 2.17 (s, 3H, CH3), 2.26 (m, 2H, 2-CH), 2.81-2.85 (m, 1H, 6-CH), 4.68 (d, J = 5.25 Hz, 0.63H, 8-CH), 4.82 (d, J = 4.25 Hz, 0.37H, 8-CH), 6.41 (d, J = 8.25 Hz, 2H, 12,16-CH Ar), 6.89 (d, J = 8.25 Hz, 2H, 13,15-CH Ar), 7.55 (d, J1 = 8.75 Hz, J2 = 4.75 Hz, 2H, 18,22-CH Ar), 8.14 (d, J = 8.75 Hz, 2H, 19,21-CH Ar) ppm. Anal. Calcd for C20H22N2O3: C, 70.99; H, 6.55; N, 8.28. Found: C, 71.34; H, 6.81; N, 8.59.
4. Conclusion
In conclusion, we have reported a simple and new catalytic method for the synthesis of P-amino carbonyl compounds by one-pot three-component Mannich reaction of cyclohexanone, aromatic aldehydes, and anilines using nano-Rb2HPW12O40 as an efficient and green heterogeneous catalyst. The significant advantages of this method are high yields, simple work-up and easy preparation and handling of the catalyst.
5. Acknowledgement
The authors are thankful to the Research Council of Payame Noor University for their support.
6. References
1.	M. Arend, B. Westermann, N. Risch, Angew. Chem. Int. Ed. 1998, 57, 1044-1070.
https://doi.org/10.1002/(SICI)1521-3773(19980504)37:8 <1044::AID-ANIE1044>3.0.CO;2-E
2.	S. Kobayashi, H. Ishitani, Chem. Rev. 1999, 99, 1069-1094. https://doi.org/10.1021/cr980414z
3.	R. Muller, H. Goesmann, H. N. Waldmann, Angew. Chem. Int. Ed. 1999, 38, 184-187.
https://doi.org/10.1002/(SICI)1521-3773(19990115)38:1/2 <184::AID-ANIE184>3.0.C0;2-E
4.	M. A. Bigdeli, F. Nemati, G. H. Mahdavinia, Tetrahedron Lett. 2007, 48, 6801-6804. https://doi.org/10.1016Zj.tetlet.2007.07.088
5.	M. Kidwai, D. Bhatnagar, N. K. Mishra, Catal. Commun.
2008, 9, 2547-2549.
https://doi.Org/10.1016/j.catcom.2008.07.010
6.	Y. Dai, B. D. Li, H. D. Quan, C. X. Lu, Chin. Chem. Lett. 2010, 21, 31-34.
https://doi.Org/10.1016/j.cclet.2009.08.011
7.	H. Li, H. Zeng, H. Shao, Tetrahedron Lett. 2009, 50, 6858-6860. https://doi.org/10.1016Zj.tetlet.2009.09.131
8.	L. W. Xu, C. G. Xia, L. Li, J. Org. Chem. 2004, 69, 84828484. https://doi.org/10.1021/jo048778g
9.	M. Z. Kassaee, R. Mohammadi, H. Masrouri, F. Movahedi, Chinese Chem. Lett. 2011, 22, 1203-1206.
10.	F. Dong, F. Zhenghao, L. Zuliang, Catal. Commun. 2009, 10, 1267-1270. https://doi.org/10.1016/j.catcom.2009.02.003
11.	C. Yue, Synthetic Commun. 2010, 40, 3640-3647. https://doi.org/10.1080/00397910903470509
12.	H. Zeng, H. Li, H. Shao, Ultrason. Sonochem. 2009, 16, 758-762. https://doi.org/10.1016/j.ultsonch.2009.03.008
13.	H. T. Luo, Y. R. Kang, H. Y. Nie, M. Yang, J. Chin. Chem. Soc. 2009, 56, 186-195. https://doi.org/10.1002/jccs.200900027
14.	R. I. Kureshy, S. Agrawal, S. Saravanan, Tetrahedron Lett. 2010, 51, 489-494.
https://doi.org/10.1016/j.tetlet.2009.11.022
15.	M. Kidwai, N. K. Mishra, V. Bansal, Tetrahedron Lett. 2009, 50, 1355-1358. https://doi.org/10.1016/j.tetlet.2009.01.031
16.	L. Wang, J. Han, J. Sheng, H. Tian, Z. Fan, Catal. Commun. 2005, 6, 201-204.
https://doi.org/10.1016/jxatcom.2004.12.009
17.	X. C. Wang, L. J. Zhang, Z. Zhang, Z. J. Quan, Chin. Chem. Lett. 2012, 23, 423-426. https://doi.org/10.1016/j.cclet.2012.01.016
18.	A. R. Massah, R. J. Kalbasi, N. Samah, Bull. Korean Chem. Soc. 2011, 32, 1703-1708. https://doi.org/10.5012/bkcs.2011.32.5.1703
19.	M. Genelot, V. Dufaud, L. Djakovitch, Tetrahedron 2011, 67, 976-981. https://doi.org/10.1016/j.tet.2010.11.112
20.	N. T. S. Phan, T. T. Nguyen, Q. H. Luo, L. T. L. Nguyen, J. Mol. Catal. A: Chem. 2012, 363, 178-184. https://doi.org/10.1016/j.molcata.2012.06.007
21.	P. Dhanashri, S. Sawant, B. Halligudi, J. Mol. Catal. A: Chem. 2005, 237, 137-145. https://doi.org/10.1016/j.molcata.2005.04.042
22.	E. Tsukuda, S. Sato, R. Takahashi, T. Sodesawa, Catal. Commun. 2007, 8, 1349-1353. https://doi.org/10.1016/jxatcom.2006.12.006
23.	N. Azizi, L. Torkiyan, M. R.Saidi, Org. Let. 2006, 8, 20792082. https://doi.org/10.1021/ol060498v
24.	B. Eftekhari-Sis, A. Abdollahifar, M. M. Hashemi, M. Zirak, Eur. J. Org. Chem. 2006, 5152-5157. https://doi.org/10.1002/ejoc.200600493
25.	W.-B. Yi, C. Cai, J. Fluorine Chem. 2006, 127, 1515-1521. https://doi.org/10.1016/jjfluchem.2006.07.009
26.	W. Shen, L.-M. Wang, H. Tian, J. Fluorine Chem. 2008, 129, 267-273. https://doi.org/10.1016/jjfluchem.2007.12.002
27.	N. S. Kozlov, G. V. Vorobeva, Vestsi Akad Navuk BSSR. Ser Khim Navuk 1968, 4,107.
Moradgholi et al.: Nano-Rb2HPW12O40 as an Efficient and Novel Catalyst ...
Acta Chim. Slov. 2016, 63, 781-
789	789
28.	Y. Y. Yang, W. G. Shou, Y. G. Wang, Tetrahedron 2006, 62,	30. K. Gong, D. Fang, H. Wang, Z. Liu, Monatsh. Chem. 2007, 10079-10086. https://doi.Org/10.1016/j.tet.2006.08.063	138, 1195-1198.
29.	H. Eshghi, M. Rahimizadeh, M. Hosseini, A. Javadian-Saraf,	https://doi.org/10.1007/s00706-007-0767-2 Monatsh. Chem. 2013, 144, 197-203.
https://doi.org/10.1007/s00706-012-0800-y
Povzetek
Namen naših raziskav je bil ugotoviti učinkovitost Rb2HPW12O40 kot heterogenega zelenega katalizatorja pri Mannichovi reakciji. Večkomponentna kondenzacija aldehidov, amina in ketona, ki poteka v eni sami posodi pri sobni temperaturi, omogoča ob uporabi ustreznega novega nano-Rb2HPW12O40 kot katalizatorja pripravo ustreznih P-aminoketonov. Enostavno čiščenje, kratki reakcijski časi in visoki izkoristki so le nekatere izmed prednosti tega postopka. Poleg tega lahko katalizator tudi enostavno ponovno izoliramo. Nano-katalizator Rb2HPW12O40 smo karakterizirali z infrardečo spektroskopijo s Fourierjevo transformacijo, rentgensko praškovno difrakcijo in vrstično elektronsko mikroskopijo.
Moradgholi et al.: Nano-Rb2HPW12O40 as an Efficient and Novel Catalyst ...