Friedel-Crafts alkylation of N,N-dialkylanilines with nitroalkenes catalyzed by heteropolyphosphotungstic acid in water

Article abstract of DOI:10.1016/j.molcata.2013.09.037

Michael-type Friedel-Crafts alkylation of N,N-dialkylanilines with nitroalkenes catalyzed by heteropolyphosphotungstic acid (HPW) is investigated in water. The reaction is simple, clean, and affords good to excellent yields of products using small quantit

Full text of DOI:10.1016/j.molcata.2013.09.037

Journal of Molecular Catalysis A: Chemical 381 (2014) 21–25
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Journal of Molecular Catalysis A: Chemical
journal homepage: www.elsevier.com/locate/molcata
Friedel–Crafts alkylation of N,N-dialkylanilines with nitroalkenes
catalyzed by heteropolyphosphotungstic acid in water
∗
Azim Ziyaei Halimehjani , Marziye Vahdati Farvardin, Hamed Pasha Zanussi, Mohammad
Amin Ranjbari, Mehdi Fattahi
Faculty of Chemistry, Kharazmi University, 49 Mofateh Street, Tehran, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 6 July 2013
Received in revised form
Michael-type Friedel–Crafts alkylation of N,N-dialkylanilines with nitroalkenes catalyzed by het-
eropolyphosphotungstic acid (HPW) is investigated in water. The reaction is simple, clean, and affords
good to excellent yields of products using small quantity of catalyst. Also, theoretical study on the nature
of reaction in water is reported.
2
8 September 2013
Accepted 29 September 2013
Available online xxx
©
2013 Elsevier B.V. All rights reserved.
Keywords:
Friedel–Crafts
Nitroalkene
Dialkylaniline
Heteropolyphosphotungstic acid (HPW)
1
. Introduction
The Friedel–Crafts alkylation is an interesting reaction for C C
bond formation in organic chemistry. Arene derivatives such as
substituted anilines, phenols, naphthols and heteroarenes such
as indole, dihydroindole and pyrrole derivatives have been suc-
cessfully used as nucleophiles in Friedel–Crafts reaction in order
to obtain arene’s derivatives [15]. On the other hand, unsatu-
rated electrophiles such as enals, enones, chalcones, nitroalkenes,
␤,␥-unsaturated ␣-ketoesters, and ␣,␣-dicyanoolefins have been
applied extensively in Friedel–Crafts alkylation [16]. Nevertheless,
most reports in this area are focused on relatively more reac-
tive indole or pyrrole derivatives. There are only a few reports
on the Friedel–Crafts reaction of N,N-dialkylaniline derivatives
with unsaturated carbonyl compounds [17]. Friedel–Crafts alkyl-
ation of N,N-dialkylanilines with nitroolefins is rare. The only
report in this area is the Friedel–Crafts alkylation of 3-methoxy-
N,N-dimethylaniline with nitrostyrene, which have been reported
by Takenaka et al. using 7-azaindoliumtetrakis[3,5-bis(trifluoro-
methyl)phenyl]borate (TFPB) as catalyst (Scheme 1) [18]. To the
best of our knowledge, there is not any other report on the
Friedel–Crafts alkylation of N,N-dialkylanilines with nitroalkenes
in the literature. So, there is a need to develop a novel Friedel–Craft
reaction, especially for the electron-rich arenes.
Heteropoly acids (HPAs) are used as homogeneous and het-
erogeneous acid due to their strong acidity, selectivity and safety
in handling in comparison to the conventional mineral acids.
They are also used as catalyst in oxidation reactions and have
the potential of great economic rewards and green benefits [1].
Heteropolyphosphotungstic acid (HPW), the strongest HPA in the
Keggin series, is the common catalyst of choice because of its high
acidic strength, relatively high thermal stability, and lower oxi-
dation potential compared with molybdenum HPAs [2]. Recently,
heteropolyphosphotungstic acid has been used as efficient cata-
lyst in several reactions such as esterification [3], etherification
[
4], Friedel–Crafts alkylation and acylation [5], isomerization [6],
hydrolysis [7], Michael addition [8], protection of carbonyl com-
pounds and alcohols [9], oxidation [10], and etc. [11]. In addition,
Saidi and co-worker have used HPW as efficient catalyst for epoxide
ring opening [12], Mannich reaction [13] and Friedel–Crafts alkyl-
ation of indoles and pyrroles in water [14]. Therefore, using a very
small amount of HPW in water will be an ideal methodology, pro-
viding that the HPW shows higher catalytic activity under these
conditions.
The use of nitroalkenes as electrophiles has attracted significant
interest in recent years. The activating effect of nitro group, as well
as the ease of transforming to other functional groups, makes these
compounds as suitable building blocks for the synthesis of many
interesting pharmaceutical compounds [19].
∗ Corresponding author. Tel.: +98 21 88848949; fax: +98 21 88820992.
E-mail addresses: ziyaei@khu.ac.ir, azimkzn@yahoo.com (A.Z. Halimehjani).
1
381-1169/$ – see front matter © 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molcata.2013.09.037

2
2
A.Z. Halimehjani et al. / Journal of Molecular Catalysis A: Chemical 381 (2014) 21–25
Ph
-
N TFPB
N
NO2
NO2
+
H
H
Me
N
OMe
Me
N
Me
OMe
Me
PhCH , rt, 24h
3
Scheme 1. Previous report on Friedel–Crafts alkylation of N,N-dialkylanilines.
2
. Experimental
s), 5.04–5.13 (2H, m), 5.69 (1H, t, J = 8.1 Hz), 6.67 (2H, d, J = 8.4 Hz),
.17 (2H, d, J = 8.4 Hz), 7.38–7.55 (4H, m), 7.81–7.90 (2H, m), 8.16
7
13
2.1. Reagents and equipments
(1H, d, J = 8.2 Hz). C NMR (75 MHz, CDCl ): ı (ppm) 40.4, 43.8,
3
7
9.4, 112.7, 123.2, 123.8, 125.2, 125.8, 126.2, 126.6, 128.2, 128.6,
All chemicals were purchased from commercial sources and
128.9, 131.2, 134.2, 135.3, 149.8. Anal. Calcd. (%) for C20H20N O :
2
2
used as received. Tap water was used in all experiments. Solvents
were used as received without further purifications and drying.
Melting points were determined with a Branstead Electrother-
mal 9200 apparatus and are uncorrected. 1H NMR and C NMR
spectra were determined with a Brucker AMX 300 spectrometer
in CDCl3 with TMS as internal standard. Elemental analyses were
conducted with a Perkin-Elmer 2004 (II) CHN analyzer.
C, 74.98; H, 6.29; N, 8.74. Found: C, 74.68; H, 6.58; N, 8.95.
N,N-diethyl-4-(1-(naphthalen-7-yl)-2-nitroethyl)benzenamine
(Table 2, entry 5). Yield: 0.660 g (85%); viscous yellow oil. 1
H
13
NMR (300 MHz, CDCl ): ı (ppm) 1.11 (6H, t, J = 7.0 Hz), 3.27 (4H,
3
q, J = 7.0 Hz), 4.98–5.13 (2H, m), 5.60 (1H, t, J = 8.2 Hz), 6.56(2H, d,
J = 8.8 Hz), 7.08 (2H, d, J = 8.8 Hz), 7.38–7.49 (4H, m), 7.76 (1H, d,
J = 8.1 Hz), 7.83 (1H, d, J = 8.1 Hz), 8.13 (1H, d, J = 8.1 Hz). 13C NMR
(
75 MHz, CDCl ): ı (ppm) 12.5, 43.8, 44.2, 79.4, 111.8, 123.2, 123.8,
3
2
.2. Reaction of N,N-dialkylanilines with nitroalkenes: general
125.2, 125.8, 126.6, 128.1 (2C), 128.8, 128.9, 131.2, 134.2, 135.7,
149.7. Anal. Calcd. (%) for C22H24N2O2: C, 75.81; H, 6.94; N, 8.04.
Found: C, 75.83; H, 7.20; N, 8.04.
procedure
In
a
test tube equipped with
a
magnetic stirrer, N,N-
4-(1-(2-chlorophenyl)-2-nitroethyl)-N,N-
dialkylaniline (2.2 mmol), nitroalkene (2 mmol), and water (5 mL)
were added. To this mixture, HPW (0.1 g, 0.035 mmol, 0.0175 mol%)
was added and stirred at reflux temperature. Progress of the
reaction was monitored by TLC. After completion of the reaction
dimethylbenzenamine (Table 2, entry 6). Yield: 0.53 g (87%);
◦
1
yellowish solid; mp 93–95 C. H NMR (300 MHz, CDCl3): ı (ppm)
2.95 (6H, s), 4.89–5.02 (2H, m), 5.35 (1H, t, J = 8.1 Hz), 6.66 (2H,
d, J = 8.8 Hz), 7.11 (2H, d, J = 8.8 Hz), 7.19–7.41 (4H, m). 13C NMR
(75 MHz, CDCl3): ı (ppm) 40.4, 44.4, 78.1, 112.6, 124.8, 127.1,
128.0, 128.5, 128.7, 130.3, 134.1, 137.3, 149.8. Anal. Calcd. (%) for
C16H17ClN2O2: C, 63.05; H, 5.62; N, 9.19. Found: C, 63.12; H, 5.51;
N, 9.03.
(
18 h), the products were collected by filtration or extraction with
ethyl acetate (2 × 10 mL, in the case of oily products). Purifica-
tion was accomplished using column chromatography (silica gel
and gradient of petroleum ether–ethyl acetate). The products were
characterized by their H and C NMR spectra and CHN analyses.
N,N-dimethyl-4-(2-nitro-1-phenylethyl)benzenamine (Table 2,
entry 1). Yield: 0.481 g (89%); viscous yellow oil; H NMR (300 MHz,
1
13
4-(1-(2-chlorophenyl)-2-nitroethyl)-N,N-diethylbenzenamine
(Table 2, entry 7). Yield: 0.564 g (85%); viscous yellow oil; 1
H
1
NMR (300 MHz, CDCl ): ı (ppm) 1.24 (6H, t, J = 7.0 Hz), 3.35 (4H, q,
3
CDCl ): ı (ppm) 3.02 (6H, s), 4.85–4.99 (3H, m), 6.60 (2H, d,
J = 7.1 Hz), 5.00 (2H, m), 5.45 (1H, t, J = 8.1 Hz), 6.65 (2H, d, J = 8.6 Hz),
3
13
7.11–7.73 (6H, m). 13C NMR (75 MHz, CDCl ): ı (ppm) 44.6, 47.4,
J = 8.6 Hz), 7.10 (2H, d, J = 8.7 Hz), 7.22–7.37 (5H, m).
C NMR
3
(
1
75 MHz, CDCl ): ı (ppm) 42.6, 48.2, 79.2, 112.1, 126.0, 127.5, 127.6,
28.5, 128.8, 139.5, 146.5. Anal. Calcd. (%) for C16H18N O : C, 71.09;
2 2
77.6, 112.4, 123.5, 127.5, 127.8, 129.4, 129.8, 130.6, 134.1, 137.4,
149.8. Anal. Calcd. (%) for C18H21ClN2O2: C, 64.96; H, 6.36; N, 8.42.
Found: C, 65.12; H, 6.55; N, 8.33.
3
H, 6.71; N, 10.36. Found: C, 71.12; H, 6.51; N, 10.13.
N,N-diethyl-4-(2-nitro-1-phenylethyl)benzenamine (Table 2,
4-(1-(4-chlorophenyl)-2-nitroethyl)-N,N-
1
dimethylbenzenamine (Table 2, entry 8). Yield: 0.561 g (92%);
entry 2). Yield: 0.554 g (93%); viscous yellow oil; H NMR (300 MHz,
CDCl ): ı (ppm) 1.22 (6H, t, J = 7.1 Hz), 3.41 (4H, q, J = 7.2 Hz),
4
7
4
◦
1
white solid; mp 62–65 C. H NMR (300 MHz, CDCl3): ı (ppm)
3
.87–5.02 (3H, m), 6.70 (2H, d, J = 8.6 Hz), 7.15 (2H, d, J = 8.6),
2.94 (6H, s), 4.77–4.95 (3H, m), 67 (2H, dd, J = 6.8 and 1.9 Hz), 7.06
1
3
(2H, dd, J = 6.8 and 1.9 Hz), 7.18–7.32 (4H, m). 13C NMR (75 MHz,
.28–7.47 (5H, m). C NMR (75 MHz, CDCl ): ı (ppm) 12.3, 44.0,
3
8.0, 79.4, 111.5, 125.2, 127.4, 127.7, 128.3, 128.6, 139.9, 146.8.
CDCl3): ı (ppm) 40.4, 47.6, 79.4, 112.8, 126.1, 128.3, 129.0, 129.1,
133.1, 138.7, 149.9. Anal. Calcd. (%) for C16H17ClN2O2: C, 63.05; H,
5.62; N, 9.19. Found: C, 63.59; H, 5.78; N, 8.90.
Anal. Calcd. (%) for C18H22N O : C, 72.46; H, 7.43; N, 9.39. Found:
C, 72.69; H, 7.58; N, 9.71.
2
2
N,N-dimethyl-4-(1-(naphthalen-3-yl)-2-
4-(1-(4-methoxyphenyl)-2-nitroethyl)-N,N-
nitroethyl)benzenamine (Table 2, entry 4). Yield: 0.576 g (90%);
yellow viscous oil. H NMR (300 MHz, CDCl ): ı (ppm) 2.95 (6H,
dimethylbenzenamine (Table 2, entry 9). Yield: 0.498 g (83%);
1
viscous yellow oil. 1H NMR (300 MHz, CDCl ): ı (ppm) 2.95 (6H, s),
3
3
R
R
N
R
R
N
NO2
HPW(0.0175 mol%)
H O, reflux
X
2
NO2
R=methyl or ethyl
X=EWG or EDG
X
1
2
3
Scheme 2. Friedel–Crafts alkylation of N,N-dialkylanilines with nitroalkenes.

A.Z. Halimehjani et al. / Journal of Molecular Catalysis A: Chemical 381 (2014) 21–25
23
Table 1
Reaction of N,N-dimethyaniline with 4-chloro nitrostyrene in the presence of different water-tolerant catalyst
.
Catalyst
Yield (%)
HPWa
92
PTSA
50
FeCl3·6H2O
H3BO3
35
CuCl
30
␤-CD
ZrOCl2·8H2O
SnCl2
20
CuCl2
Trace
NiCl2·6H2O
SiO2–SO3Hb
Trace
DABCO
Trace
50
33
25
10
a
0
.0175 mol% of HPW was used.
b
The reaction was carried out with 0.2 g of SiO2–SO3H in toluene.
3
.81 (3H, s), 4.81–4.96 (3H, m), 6.70 (2H, d, J = 8.7 Hz), 6.87 (2H, d,
(4H, q, J = 7.1 Hz), 4.85–5.00 (3H, m), 6.69 (2H, d, J = 8.6 Hz), 7.14
13
13
J = 8.7 Hz), 7.10 (2H, d, J = 8.7 Hz), 7.18 (2H, d, J = 8.6 Hz). C NMR
75 MHz, CDCl ): ı (ppm) 40.5, 47.5, 55.2, 79.8, 112.7, 114.2, 128.2,
(2H, d, J = 8.6 Hz), 7.14 (2H, d, J = 8.5 Hz), 7.20–7.36 (4H, m).
C
(
NMR (75 MHz, CDCl ): ı (ppm) 12.4, 20.8, 44.1, 47.7, 79.5, 111.7,
3
3
1
28.6, 129.8, 132.0, 149.7, 158.6. Anal. Calcd. (%) for C17H20N O :
125.5, 127.3, 128.3, 129.1, 136.6, 136.9, 146.8. Anal. Calcd. (%) for
2
3
C, 67.98; H, 6.71; N, 9.33. Found: C, 67.75; H, 6.88; N, 9.43.
C19H24N O : C, 73.05; H, 7.74; N, 8.97. Found: C, 72.69; H, 7.69; N,
2 2
N,N-diethyl-4-(1-(4-methoxyphenyl)-2-
8.78.
nitroethyl)benzenamine (Table 2, entry 10). Yield: 0.591 g (90%);
N,N-diethyl-4-(2-nitro-1-(2-nitrophenyl)ethyl)benzenamine
1
(Table 2, entry 16). Yield: 0.597 g (87%); viscous yellow oil; 1
viscous yellow oil. H NMR (300 MHz, CDCl ): ı (ppm) 1.17 (6H, t,
H
3
J = 7.0 Hz), 3.34 (4H, q, J = 7.1 Hz), 3.83 (3H, s), 4.78 (1H, t, J = 7.7 Hz),
NMR (300 MHz, CDCl ): ı (ppm) 1.16 (6H, t, J = 7.0 Hz), 3.36 (4H, q,
3
4
(
.92–4.96 (2H, m), 6.63 (2H, d, J = 8.5 Hz), 6.87 (2H, d, J = 8.7), 7.06
J = 7.1 Hz), 4.87–5.02 (3H, m), 6.62 (2H, d, J = 8.6 Hz), 7.01 (2H, d,
J = 8.7 Hz), 7.50 (1H, t, J = 7.9 Hz), 7.60 (1H, d, J = 7.8 Hz), 8.04–8.14
2H, d, J = 8.7 Hz), 7.19 (2H, d, J = 8.6 Hz). 13C NMR (75 MHz, CDCl ):
3
ı (ppm) 12.5, 44.3, 47.5, 55.2, 79.9, 111.9, 114.2, 128.4, 128.6,
49.5, 158.6, two quaternary carbons were not observed. Anal.
Calcd. (%) for C19H24N O : C, 69.49; H, 7.37; N, 8.53. Found: C,
(2H, m). 13C NMR (75 MHz, CDCl ): ı (ppm) 12.5, 44.2, 47.8, 78.9,
3
1
111.9, 122.4, 122.5, 128.4, 129.8, 133.7, 135.8, 138.4, 147.2, 148.3.
Anal. Calcd. (%) for C18H21N O : C, 62.96; H, 6.16; N, 12.24. Found:
2
3
3
4
6
9.69; H, 7.68; N, 8.70.
C, 63.13; H, 6.56; N, 12.43.
N,N-dimethyl-4-(2-nitro-1-(thiophen-2-yl)ethyl)benzenamine
N,N-dimethyl-4-(2-nitro-1-(3-nitrophenyl)ethyl)benzenamine
(Table 2, entry 17). Yield: 0.567 g (90%); viscous yellow oil; H NMR
(
(
(
(
Table 2, entry 11). Yield: 0.58 g (92%); viscous yellow oil. 1H NMR
1
300 MHz, CDCl ): ı (ppm) 2.92 (6H, s), 4.87–5.00 (3H, m), 6.66
2H, d, J = 8.8 Hz), 6.88–6.95 (2H, m), 7.14–7.21 (3H, m). C NMR
(300 MHz, CDCl ): ı (ppm) 2.94 (6H, s), 4.89–5.02 (3H, m), 6.67
3
3
13
(2H, d, J = 8.7 Hz), 7.06 (2H, d, J = 8.6 Hz), 7.48–7.59 (2H, m), 8.10
75 MHz, CDCl ): ı (ppm) 40.4, 43.9, 80.3, 112.6, 124.6, 124.9,
(1H, d, J = 8.4 Hz), 8.14 (1H, s). 13C NMR (75 MHz, CDCl ): ı (ppm)
3
3
1
26.1, 126.9, 128.2, 143.6, 150.1. Anal. Calcd. (%) for C14H16N O S:
40.3, 47.8, 78.9, 112.8, 122.5, 128.2, 128.8, 129.9, 130.9, 133.7,
2
2
C, 60.85; H, 5.84; N, 10.14. Found: C, 61.06; H, 5.60; N, 10.18.
142.2, 146.9, 148.1. Anal. Calcd. (%) for C16H17N O : C, 60.94; H,
3 4
N,N-diethyl-4-(2-nitro-1-(thiophen-2-yl)ethyl)benzenamine
5.43; N, 13.33. Found: C, 61.12; H, 5.51; N, 13.09.
(
Table 2, entry 12). Yield: 0.578 g (95%); viscous yellow oil. 1
H
NMR (300 MHz, CDCl ): ı (ppm) 1.19 (6H, t, J = 7.1 Hz), 3.37 (4H, q,
3
3
. Results and discussion
J = 7.1 Hz), 4.87–5.07 (3H, m), 6.66 (2H, d, J = 8.8 Hz), 6.94–7.00 (2H,
m), 7.15–7.26 (3H, m). 13C NMR (75 MHz, CDCl ): ı (ppm) 12.5,
3
In continuation of our research toward the development of
4
3.9, 44.2, 80.3, 111.7, 124.6, 124.76, 124.83, 126.8, 128.4, 143.7,
green organic chemistry by using water as the reaction medium
or as catalyst [20], herein we report an efficient, novel, and green
1
47.3. Anal. Calcd. (%) for C16H20N O S: C, 63.13; H, 6.62; N, 9.20.
2
2
Found: C, 63.11; H, 6.95; N, 9.52.
4
-(1-(2,4-dichlorophenyl)-2-nitroethyl)-N,N-
procedure for the Michael-type Friedel–Crafts alkylation of N,N-
dialkylaniline with nitroolefins in water using small amount of
HPW as catalyst as outlined in Scheme 2.
dimethylbenzenamine (Table 2, entry 13). Yield: 0.576 g (85%);
yellowish solid; mp 84–87 C. H NMR (300 MHz, CDCl ): ı (ppm)
◦
1
3
2
.97 (6H, S), 4.87–5.02 (2H, m), 5.33 (1H, t, J = 8.2 Hz), 6.72 (2H,
We initially examined the Friedel–Crafts alkylation of N,N-
dimethylaniline with 4-chloro nitrostyrene at catalyst-free con-
ditions in different solvents such as water, THF, diethyl ether,
acetonitrile, hexane, dichloromethane, chloroform, methanol and
ethanol in reflux temperature, with the exception of DMF, which
13
d, J = 8.8 Hz), 7.11 (2H, d, J = 8.8 Hz), 7.24–7.45 (3H, m). C NMR
75 MHz, CDCl ): ı (ppm) 40.2, 43.9, 77.8, 112.1, 124.1, 127.4,
(
1
3
28.0, 128.5, 130.0, 133.6, 134.7, 135.9, 149.8. Anal. Calcd. (%) for
C16H16Cl N O : C, 56.65; H, 4.75; N, 8.26. Found: C, 56.79; H, 4.97;
N, 7.76.
-(1-(2,4-dichlorophenyl)-2-nitroethyl)-N,N-
diethylbenzenamine (Table 2, entry 14). Yield: 0.654 g (89%);
viscous yellow oil. H NMR (300 MHz, CDCl ): ı (ppm) 1.18 (6H,
2
2
2
◦
was done at 100 C. We have found that the best yield was obtained
4
in water (40%) and no products were obtained in other used organic
solvents. In continuation, we have focused our attempt to improve
the reaction yield in water. Encouraged by the work of Saidi et al.
[12–14] on using heteropoly acids in water as efficient homogenous
catalyst, we have found that by using a small amount of het-
eropolyphosphotungstic acid in water at reflux temperature, good
to excellent yield of product was obtained. Using HPW in organic
solvents as heterogenous catalytic systems in reflux temperature
gave only trace amount of product.
1
3
t, J = 7.0 Hz), 3.35 (4H, q, J = 7.0 Hz), 4.87–5.02 (2H, m), 5.32 (1H, t,
J = 8.2 Hz), 6.65 (2H, d, J = 8.8 Hz), 7.07 (2H, d, J = 8.8 Hz), 7.23–7.31
(
2H, m), 7.45(1H, d, J = 1.6 Hz). 13C NMR (75 MHz, CDCl ): ı (ppm)
3
1
1
2.5, 43.9, 44.2, 77.9, 111.7, 122.9, 127.4, 128.7, 128.8, 130.0, 133.6,
34.7, 136.1, 147.2. Anal. Calcd. (%) for C18H20Cl N O : C, 58.86;
2
2
2
H, 5.49; N, 7.63. Found: C, 58.70; H, 5.0; N, 7.22.
N,N-diethyl-4-(2-nitro-1-p-tolylethyl)benzenamine (Table 2,
entry 15). Yield: 0.580 g (93%); viscous yellow oil. H NMR
After successful results of using HPW in water, diversity of
water-tolerant catalyst were also examined for the reaction of
N,N-dimethylaniline with 4-chloro nitrostyrene in water and the
1
(
300 MHz, CDCl ): ı (ppm) 1.23 (6H, t, J = 7.0 Hz), 2.44 (3H, s), 3.41
3

2
4
A.Z. Halimehjani et al. / Journal of Molecular Catalysis A: Chemical 381 (2014) 21–25
Table 2
Friedel–Crafts alkylation of nitroalkenes with N,N-dialkylanilines catalyzed by HPW in water
.
Entry
1
Electrophile
Electron rich arene
1
Yield (%)a
89
2
3
4
2
3
1
93
N.R.
90
5
2
85
6
7
1
2
87
85
8
1
92
9
1
1
1
2
1
83
90
92
0
1
1
2
2
95
1
1
3
4
1
2
85
89
1
1
5
6
2
2
93
87
1
7
8
1
1
90
1
N.R.
a
Reaction condition: N,N-dialkylaniline (2.2 mmol), nitroalkene (2 mmol), water (5 mL) and HPW (0.1 g, 0.035 mmol, 0.0175 mol%) at reflux temperature.
results are summarized in Table 1. Among the used catalysts,
3). Chalcones are not suitable electrophile in this reaction (Table 2,
entry 18), which may be because of lower electrophilicity compare
to nitroalkenes. Substitution was occurred only at the para posi-
tion of the N,N-dialkylanilines and no ortho product was observed.
Work-up was very simple; involving filtration of the solid products
or decanting the water in most of the cases. Further purification
was accomplished by using column chromatography if needed.
Theoretical calculations for determination of the optimized
parameters (dipole moment, solvation energy, and partial charge
on the p-position) of N,N-dimethylaniline and N,N-diethylaniline
were performed with the HF/6-311G** basis set using Gaussian 03
software. As shown in Table 3, the dipole moment and the par-
tial charge on the p-position of N,N-dialkylanilines in water are
greater than in organic solvents, which may ascribe the higher
Only PTSA and FeCl ·6H O gave 50% yields. Boric acid, SnCl , ␤-
3
2
2
cyclodextrin, ZrOCl ·8H O and CuCl gave low yield of product. With
2
2
CuCl , NiCl ·6H O, Silica-sulfuric acid and DABCO trace amount
2
2
2
of product was obtained. The results show the efficiency of HPW
as catalyst in this reaction. With optimized conditions in hand,
we then expanded our study to other electron-riched arenes and
different nitroalkenes. As shown in Table 2, N,N-dimethylanilines
and N,N-diethylaniline gave excellent yields. Also, nitroalkenes
with electron-donating and electron-withdrawing groups on the
phenyl ring gave excellent yields. Aliphatic nitroalkenes were also
examined for this transformation without any result. Using 1,2-
dimethoxy benzene as electron-riched arene did not afford any
products and the starting material was recovered (Table 2, entry

A.Z. Halimehjani et al. / Journal of Molecular Catalysis A: Chemical 381 (2014) 21–25
25
Table 3
Calculated parameters for N,N-dimethylaniline and N,N-diethylaniline in different solvents using the HF/6-311G** basis set.
Solvent
N,N-dimethylaniline
(Debye)a
N,N-diethylaniline
ꢀ
ıb
ꢁG#c
ꢀ (Debye)a
ıb
ꢁG#c,d
Gas phase
Water
DMSO
THF
CHCl3
CH3CN
CH3NO2
Toluene
Ethanol
Methanol
Acetone
0.7362
1.1498
1.1033
1.0042
0.9544
1.1063
1.1075
0.8543
1.0900
1.1147
1.0795
−0.4777
−0.5629
−0.5610
−0.5438
−0.5344
−0.5601
−0.5603
−0.5124
−0.5577
−0.5595
−0.5564
–
0.7109
1.2283
1.1845
1.0383
0.9802
1.1839
1.1878
0.8532
1.1662
1.1865
1.1536
−0.5838
−0.6424
−0.6400
−0.6281
−0.6223
−0.6395
−0.6396
−0.6078
−0.6380
−0.6401
−0.6367
–
4.03
2.25
2.64
2.05
4.35
2.12
2.64
−0.21
−0.3
0.19
5.91
3.81
4.10
3.27
6.24
3.60
3.69
0.79
0.70
1.22
a
Dipole moment for N,N-dialkylanilines in different solvents.
Partial charge on C-4 of N,N-dialkylanilines.
Solvation energy.
b
c
d
PCM model was used to model solvation effect.
nucleophilic ability of the p-carbon toward nitroolefins. Also partial
negative charge on the p-position in N,N-diethylaniline (−0.6424) is
greater than in N,N-dimethylaniline (−0.5629), which confirm the
higher electron donating ability of diethylamino group on phenyl
ring related to dimethylamino group. In addition, the higher dipole
moment of N,N-diethylaniline compare to N,N-dimethylaniline can
be correlated to higher solvation energy which in gas phase the
dipole moment is the reverse of this.
[6] A. Alsalme, E.F. Kozhevnikova, I.V. Kozhevnikov, Appl. Catal. A: Gen. 390 (2010)
19–224.
2
[
[
7] X. Li, Y. Jiang, L. Wang, L. Meng, W. Wang, X. Mu, RSC Adv. 2 (2012) 6921–6925.
8] H. Firouzabadi, N. Iranpoor, A.A. Jafari, Synlett (2005) 299–303.
[9] H. Firouzabadi, N. Iranpoor, K. Amani, Synthesis (2002) 59–60.
10] (a) X.M. Yan, P. Mei, J. Lei, Y. Mi, L. Xiong, L. Guo, J. Mol. Catal. A: Chem. 304
[
(
2009) 52–57;
(
b) B.S. Ma, Z. Zhang, W. Song, X. Xue, Y. Yu, Z. Zhao, Y. Ding, J. Mol. Catal. A:
Chem. 368–369 (2013) 152–157;
(c) H. Zhao, L. Zeng, L. Li, C. Liu, B. Hou, D. Wu, N. Feng, A. Zheng, X. Xie, S. Su,
N. Yu, Microporous Mesoporous Mater. 172 (2013) 67–76;
(
d) R. Gao, Q. Zhu, W.L. Dai, K. Fan, Green Chem. 13 (2011) 702–708.
4
. Conclusions
[11] (a) M. North, R. Pasquale, C. Young, Green Chem. 12 (2010) 1514–1539;
(
(
(
b) S.H. Chai, H.P. Wang, Y. Liang, B.Q. Xu, Green Chem. 10 (2008) 1087–1093;
c) E. Rafiee, S. Rashidzadeh, A. Azad, J. Mol. Catal. A: Chem. 261 (2007) 49–52;
d) S.V. Bhilare, A.R. Deorukhkar, N.B. Darvatkar, M.S. Rasalkar, M.M. Salunkhe,
In conclusion, we have reported a mild, simple, and environ-
mentally benign procedure for the Friedel–Crafts alkylation of
N,N-dialkylanilines with nitroolefins in aqueous medium using
heteropolyphosphotungstic acid as catalyst. This procedure offers
several advantages including the use of green and low-loading cat-
alyst, high to excellent yield, green solvent, cleaner reaction and
simple experimental procedure, which make it a useful and attrac-
tive strategy in synthetic organic chemistry. In addition, water may
play dual roles in this procedure as a solvent or as a co-catalyst.
Water may accelerate the reaction via hydrogen bonding with
nitroalkenes or increase the catalytic efficiency of heteropolyphos-
photungstic acid by providing a homogenous medium with highly
acidic strength. Theoretical studies also support our finding on the
Friedel–Crafts alkylation on the p-position in phenyl ring and why
the reaction is plausible in water compared to organic solvents.
J. Mol. Catal. A: Chem. 270 (2007) 123–126;
(e) J.S. Yadav, B.V. Subba Reddy, D.N. Chaya, G.G.K.S.N. Kumar, P. Naresh, P.
Jagadeesh, Tetrahedron Lett. 50 (2009) 1799–1802;
(
(
f) L. Yang, L.W. Xu, C.G. Xia, Tetrahedron Lett. 49 (2008) 2882–2885;
g) K. Lan, Z. Shan, S. Fan, Tetrahedron Lett. 47 (1) (2006) 4343–4345.
[12] N. Azizi, M.R. Saidi, Tetrahedron 63 (2007) 888–891.
[
[
[
13] N. Azizi, L. Torkian, M.R. Saidi, Org. Lett. 8 (2006) 2079–2082.
14] N. Azizi, F. Arynasab, M.R. Saidi, Org. Biomol. Chem. (2006) 4275–4277.
15] For a general review on Friedel–Crafts reactions, see:
(a) G.A. Olah, R. Krishnamurti, G.K.S. Prakash, Friedel–Crafts alkylations, in: B.M.
Trost, I. Fleming (Eds.), Comprehensive Organic Synthesis, vol. 3, Pergamon
Press, Oxford, 1991, p. 293.
[
[
16] For selected reviews on organocatalytic asymmetric Friedel–Crafts reaction,
see:
(
(
(
a) P. Chauhan, S.S. Chimni, RSC Adv. 2 (2012) 6117–6134;
b) S.L. You, Q. Cai, M. Zeng, Chem. Soc. Rev. 38 (2009) 2190–2201;
c) V. Terrasson, R.M. de Figueiredo, J.M. Campagne, Eur. J. Org. Chem. (2010)
2635–2655;
d) M. Zen, S.L. You, Synlett (2010) 1289–1301.
17] (a) N.A. Paras, D.W.S. MacMillan, J. Am. Chem. Soc. 124 (2002) 7894–7895;
(
Acknowledgment
(
(
b) Y.C. Guo, D.P. Li, Y.L. Li, H.M. Wang, W.J. Xiao, Chirality 21 (2009) 777–785;
c) Y. Zhou, X. Li, S. Hou, J. Xu, J. Mol. Catal. A: Chem. 365 (2012) 203–211;
We are grateful to the Faculty of Chemistry of Kharazmi Univer-
sity (former Tarbiat Moallem University) for supporting this work.
(d) W. Yin, Y. Ma, J. Xu, Y. Zhao, J. Org. Chem. 71 (2006) 4312–4315;
(
(
(
e) X. Wang, Y. Wang, D.M. Du, J. Xu, J. Mol. Catal. A: Chem. 255 (2006) 31–35;
f) Z. Zhang, Y. Ma, Y. Zhao, Synlett 7 (2008) 1091–1095;
g) J. Xu, J. Xia, Y. Lan, Synth. Commun. 35 (2005) 2347–2353.
References
[18] N. Takenaka, R.S. Sarangthem, S.K. Seerla, Org. Lett. 9 (2007) 2819–2822.
[
19] R. Ballini, in: Atta-ur-Rahman (Ed.), Studies in Natural Products Chemistry, 19,
Elsevier, Amsterdam, 1997, p. p117.
[1] (a) I.V. Kozhevnikov, Catalysts for Fine Chemicals Catalysis by Polyoxometa-
[
20] (a) A. Ziyaei-Halimehjani, K. Marjani, A. Ashouri, Green Chem. 12 (2010)
lates, Wiley, Chichester, 2002;
1
(
3
306–1310;
b) A. Ziyaei-Halimehjani, K. Marjani, A. Ashouri, J. Heterocycl. Chem. 46 (2009)
47–350;
(
b) I.V. Kozhevnikov, Chem. Rev. 98 (1998) 171–198.
2] (a) I.V. Kozhevnikov, Catal. Rev. Sci. Eng. 37 (1995) 311–352;
b) T. Okuhara, N. Mizuno, M. Misono, Adv. Catal. 41 (1996) 113–252.
3] (a) A. Alsalme, E.F. Kozhevnikova, I.V. Kozhevnikov, Appl. Catal. A: Gen. 349
[
[
(
(
(
c) A. Ziyaei-Halimehjani, M.R. Saidi, Tetrahedron Lett. 49 (2008) 1244–1248;
d) A. Ziyaei-Halimehjani, F. Aryanasab, M.R. Saidi, Tetrahedron Lett. 50 (2009)
(
2008) 170–176;
1441–1443;
(
b) T.H.T. Vu, H.T. Au, T.M.T. Nguyen, M.T. Pham, T.T. Bach, H.N. Nong, Catal. Sci.
(
(
(
e) N. Azizi, F. Aryanasab, L. Torkiyan, A. Ziyaei, M.R. Saidi, J. Org. Chem. 71
2006) 3634–3635;
f) K. Marjani, M. Khalesi, A. Ashouri, A. Jalali, A. Ziyaei-Halimehjani, Synth.
Technol. 3 (2013) 699–705.
[
[
4] Z. Yuan, S. Xia, P. Chen, Z. Hou, X. Zheng, Energy Fuels 25 (2011) 3186–3191.
5] (a) L.A.M. Cardoso, A.R.E. Gonzaga, L.M.G. Aguiar, H.M.C. Andrade, J. Mol. Cat.
A: Chem. 209 (2004) 189–197;
Commun. 1 (2011) 451–458;
g) F. Aryanasab, A. Ziyaei-Halimehjani, M.R. Saidi, Tetrahedron Lett. 51 (2010)
90–792.
(
7
(
b) A. Llanos, L. Melo, F. Avenda n˜ o, A. Montes, J.L. Brito, Catal. Today 133-135
(2008) 20–27.