Benzyl alcohol-based synthesis of mono- and bis-dihydropyridines in the presence of Al(HSO4)3, sodium nitrite, and sodium bromide under solvent-free conditions

Article abstract of DOI:10.1134/S1070363216060281

Dihydropyridines were synthesized in good to excellent yields in the presence of NaNO₂, Al(HSO₄)₃, and a catalytic amount of NaBr at room temperature. Low cost, the use of available reagents, simple methodology, and easy work-up procedure make this method attractive for organic synthesis.

Full text of DOI:10.1134/S1070363216060281

ISSN 1070-3632, Russian Journal of General Chemistry, 2016, Vol. 86, No. 6, pp. 1412–1418. © Pleiades Publishing, Ltd., 2016.
Benzyl Alcohol-Based Synthesis of Mono- and
Bis-dihydropyridines in the Presence of Al(HSO ) ,
4
3
Sodium Nitrite, and Sodium Bromide
1
under Solvent-Free Conditions
a
b
L. Z. Fekri and M. Nikpassand
a
Department of Chemistry, Payame Noor University, PO Box 19395-3697, Tehran, Iran
e-mail: chem_zare@yahoo.com
b
Department of Chemistry, Rasht Branch, Islamic Azad University, Rasht, Iran
Received December 17, 2015
2 4 3
Abstract—Dihydropyridines were synthesized in good to excellent yields in the presence of NaNO , Al(HSO ) ,
and a catalytic amount of NaBr at room temperature. Low cost, the use of available reagents, simple
methodology, and easy work-up procedure make this method attractive for organic synthesis.
Keywords: solvent free, dihydropyridine, benzyl alcohol, Al (HSO
4 3
)
DOI: 10.1134/S1070363216060281
INTRODUCTION
antianxiety, antidepressive, antitumor, analgesic, se-
ditative, vasodilator, bronchodilator, hypnotic, and anti
-inflammatory agents [3, 4]. DHPs are commercial
calcium channel blockers used for the treatment of
cardiovascular diseases, including hypertension [5].
Recently, chemists have found that many reactions,
especially organic reactions, proceed with higher
efficiency and selectivity in the solid than in a liquid
state. Advantages of solvent-free reaction are reduced
pollution, low cost, simplicity of the synthesis process,
and easy work-up procedure. These factors are
especially important for industry [1].
The method of the synthesis of 1,4-dihyd-
ropyridines was first reported by Hantzsch for more
than a century ago and involves one-pot condensation
of an aldehyde with ethyl acetoacetate and ammonium
acetate [6]. In recent years, there exist several efficient
modifications of the Hantzsch synthesis, including the
use of microwave irradiation [5], refluxing solvents
[9], ionic liquids [6], TMSCl-NaI [10], metal triflates
The synthesis in the presence of solid acids, which
are easy-to-work-up compounds, uses reactors of
smaller capacity, involves lesser problems associated
with corrosion of plant equipment, and allows the
environmentally friendly methods of waste disposal.
[11], I [12], CAN [13], and L-propine [14].
2
Also, wastes and by-products can be minimized or
avoided by developing cleaner synthesis routes. On the
other hand, to minimize risk of synthesis, make it
economically profitable and eco-friendly, it is
necessary to reduce the amount of sulfuric acid and/or
make work-up procedures simpler [1].
However, high temperatures, harmful organic
solvents, harsh reaction conditions, expensive metal
precursors, long reaction times, occurrence of side
products, and difficulty in recovery and reusability of
the catalyst set limit for these methods.
RESULTS AND DISCUSSION
1
,4-dihydropyridines (1,4-DHPs) and their deriva-
tives are important class of bioactive molecules in the
field of drugs and pharmaceuticals [2]. The hetero-
cyclic ring in DHP is a common fragment of such
bioactive compounds, as anticonvulsant, antidiabetic,
In continuation of our ongoing studies on the
synthesis of heterocyclic and pharmaceutical com-
pounds at mild and practical protocols, especially those
using benzyl alcohols [14–19], here we report our
experimental results on the synthesis of dihyd-
1
The text was submitted by the authors in English.
1
412

BENZYL ALCOHOL-BASED SYNTHESIS OF MONO- AND BIS-DIHYDROPYRIDINES
1413
4 3
Scheme 1. Synthesis of dihydropyridines from benzyl alcohols in the presence of Al(HSO ) , NaNO2, and NaBr.
O
CH OH
2
O
NH
O
N
Al(HSO4)3
+
+ NH
4
OAc
+
NaNO , NaBr
2
Solvent free
R
O
O
3
O
4
R
R
1
2
Not observed
ropyridines, in which a novel oxidizing system based
on in situ generation of halonium is used for the
selective oxidation of benzyl alcohols to aryl
aldehydes. The reaction of a substituted benzyl alcohol
with dimedone and ammonium acetate proceeds in the
presence of NaNO , Al(HSO ) and a catalytic amount
of NaBr under solvent-free condition (Scheme 1). To
the best of our knowledge, no data are available from
the literature on the alcohol-based synthesis of
dihydropyridines.
In continuation of our study on the benzyl alcohol-
based synthesis of dihydropyridines, we synthesized
bis-dihydropyridines 6h–6k, as shown in Scheme 2.
The results are summarized in Table 2.
The structures of bis-dihydropyridines synthesized
from corresponding benzyl alcohols are demonstrated
in the figure.
2
4 3,
A possible mechanism of the synthesis of fused 1,4
-dihydropyridine derivatives in the presence of the
oxidative catalytic system consisting of Al(HSO ) ,
4
3
We used in the reaction 0.1 g of Al(HSO ) , 0.1 g
4
3
NaNO , and NaBr was developed (Scheme 3). We
2
of NaNO , 0.05g of NaBr and different benzyl
2
suggest that, first, Al(HSO ) , NaNO , and NaBr [20]
4
3
2
alcohols. The results are listed in Table 1.
can produce an active oxidant, bromonium, to convert
benzyl alcohols to aldehydes and Al(HSO ) is capable
4
3
of catalyzing the formation of an oxonium ion with
aldehyde. The higher reactivity of the oxonium ion
compared to that of carbonyl could facilitate the
Knoevenagel condensation between aldehyde and
dimedone. After eliminating the water, 6 might
undergo the Michael addition with a second equivalent
of dimedone and enolize to intermediate 7. The
addition of ammonium acetate accompanied by the
elimination of the catalyst to intermediate 7 could give
the desired product 3.
Table 1. Synthesis of dihydropyridines from benzyl alcohols
in the presence of Al(HSO
4
)
3
, NaNO
2
, and NaBr
b
a
Time, Yield ,
Product
Benzyl alcohol
Benzyl alcohol
mp, °C
min
45
60
30
30
45
30
35
45
30
60
70
%
91
85
94
97
87
90
98
94
90
90
93
3
a
176–178
280–282
210–211
201–203
178–179
214–216
221–222
245–246
113–115
156–157
211–213
3
b
2-NO
3-NO
4-NO
2-Cl
2
2
2
3
c
3
d
3
e
Table 2. Synthesis of bis-dihydropyridines from various benzyl
alcohols
3
f
3-Cl
3
g
4-Cl
Comp. no.
Time, min
Yield, %
mp, °C
210–211
287–288
256–257
198–199
204–206
210–212
3
h
3-Br
4-F
6
a
60
45
30
50
40
35
94
95
92
89
97
89
3
i
6
b
3
j
4-OH
6c
3
k
4-OCH
3
6d
a
Products are identified from data on their IR and NMR spectra
and results of the elemental analysis. Yield is given for isolated
6
e
b
products; the same for Table 2.
6f
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 86 No. 6 2016

1
414
FEKRI, NIKPASSAND
Scheme 3.
Br
NO
AlCH OH
2
O
O
Al(HSO4)3
O−Al(HSO4)3
Al(HSO ) + NaNO
HNO2
AlCHO
4
3
2
Br
Ar
H
2
4
Al(HSO4)3
O
Ar
O
O
HO
Ar
Al(HSO4)3
N
H
3
H
O
5
O
Ar
O
O−Al(HSO4)3
H O
2
H
NH OAc
4
Ar
6
HO
Al(HSO )
4
3
O
7
O
EXPERIMENTAL
Chemicals were purchased from Merck and Fluka
recorded on a Bruker Avance DRX 500 spectrometer
using CDCl and DMSO-d as solvent and TMS as
3
6
internal standard. FT-IR spectra were taken on a
Shimadzu FT-IR-8400S spectrometer. Elemental
analysis was done on a Carlo-Erba EA1110CNNO-S
analyzer.
and used as purchased. Melting points were measured
on an Electrothermal 9100 apparatus and are reported
1
13
uncorrected. H NMR and C NMR spectra were
O
HN
O
O
O
O
(
CH2)n
O
NH
O
HN
O
NH
O
O
O
O
ortho (6a), meta (6b), para (6c)
ortho, n = 1 (6d), meta, n = 2 (6e), para, n = 3 (6f)
The structure of the synthesized bis-dihydropyridines 6.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 86 No. 6 2016

BENZYL ALCOHOL-BASED SYNTHESIS OF MONO- AND BIS-DIHYDROPYRIDINES
1415
Scheme 2. The synthesis of bis-dihydropyridines using benzyl alcohol as starting compound.
O
HO
OH
+
NH OAc
+
4
O
O
O
5
2
O
NH
Al(HSO4)
3
HN
O
NaNO , NaBr
2
Solvent free
O
O
O
O
–
1
General procedure for the preparation of
dihydropyridines using benzyl alcohols. A mixture
of a substituted benzyl alcohol 1 (1 mmol), dimedone
solid, mp 280–282°C, IR spectrum (KBr), ν, cm :
3450, 3080, 2980, 1650, 1540, 1520, 1480, 1360, 1345,
1220. H NMR spectrum (500 MHz), δ, ppm: 7.41–
1
2
(2 mmol), ammonium acetate (1 mmol), Al(HSO4)3
7.48 m (2H), 7.37 d (1H, J = 6.8 Hz), 7.21 t (1H, J =
(
0.1 g), NaNO (0.1 g), and NaBr (0.05 g) was stirred
7.0 Hz), 5.80 s (1H), 2.23–2.46 m (8H), 1.06 s (6H),
2
1
3
at room temperature for the required time (see Tables 2
and 3). The reaction progress was monitored by TLC
(
0.96 s (6H). C NMR spectrum (125 MHz), δ, ppm:
27.8, 29.5, 32.9, 41.2, 51.1, 112.9, 124.5, 127.0, 132.5,
134.2, 141.2, 149.6, 149.8, 195.9. Calculated, %: C
70.03; H 6.64; N 7.10. C H N O . Found, %: C
EtOAc : petroleum ether = 1 : 4). After the reaction
was complete, acetone (10 mL) was added and
insoluble reagents were removed by filtration. The
filtrate was evaporated under reduced pressure and the
resulting crude material was purified by recrystal-
lization from EtOAc to afford pure products. Unlike
the traditional method of dihydropyridine synthesis, in
which as starting compounds are used aldehydes [15],
in this method, alcohols in an oxidative procedure are
used for the first time. The properties of the
synthesized compounds were determined by the IR and
NMR spectroscopies and by the elemental analysis.
2
3
26
2
4
70.02; H 6.55; N 7.21.
3,3,6,6-Tetramethyl-9-(3-nitrophenyl)-3,4,6,7,9,10-
hexahydroacridine-1,8(2H,5H)-dione (3c). Off-white
–1
solid, mp 210–211°C, IR spectrum (KBr), ν, cm :
1
3
380, 3060, 1645, 1610, 1480, 1520, 1360, 1340. H
NMR spectrum (500 MHz), δ, ppm: 8.90 br.s (1H),
8
6
.02 s (1H), 7.83 d (1H, J = 8.1 Hz), 7.65 d (1H, J =
.9 Hz), 7.29 t (1H, J = 7.86 Hz), 5.01 s (1H), 2.35 d
(
(
2H, J = 17.1 Hz), 2.28 d (2H, J = 17.1 Hz), 2.10 d
2H, J = 16.3 Hz), 2.0 d (2H, J = 16.3 Hz), 1.01 s (6H),
1
3
3
,4,6,7-Tetrahydro-3,3,6,6-tetramethyl-9-phenyl-
0.86 s (6H). C NMR spectrum (125 MHz), δ, ppm:
27.4, 30.0, 33.0, 34.5, 51.1, 112.2, 121.2, 123.1, 130.0,
135.2, 148.4, 149.6, 150.2, 195.6. Calculated, %: C 70.03;
H 6.64; N 7.10. C H N O . Found, %: C 70.10; H
acridine-1,8(2H,5H,9H,10H)-dione (3a). White solid,
mp 280–282°C, IR spectrum (KBr), ν, cm : 3354,
3
–
1
1
081, 2946, 1654, 1532, 1445, 1367. H NMR
23
26
2
4
spectrum (500 MHz), δ, ppm: 7.67–7.82 m (5H), 5.05
s (1H), 2.41 d (2H, J = 15.0 Hz), 2.32 d (2H, J =
6.55; N 7.11.
3,3,6,6-Tetramethyl-9-(4-nitrophenyl)-3,4,6,7,9,10-
1
1
5.0 Hz), 2.09 d (2H, J = 17.5 Hz), 2.01 d (2H, J =
7.5 Hz), 1.02 s (6H), 0.87 s (6H). C NMR spectrum
hexahydroacridine-1,8(2H,5H)-dione (3d). Yellow-
orange solid, mp 201–203°C, IR spectrum (KBr), ν,
1
3
(
1
%
125 MHz), δ, ppm: 25.7, 27.9, 30.8, 33.9, 51.6, 119.4,
27.5, 129.1, 136.1, 147.7, 154.1, 199.1. Calculated,
: C 79.05; H 7.79; N 4.01. C H NO . Found, %: C
–1
cm : 3384, 3070, 2956, 1643, 1580, 1460, 1515, 1360,
1
1
342. H NMR spectrum (500 MHz), δ, ppm: 8.39 d
23
27
2
(
2H, J = 8.4 Hz), 7.98 d (2H, J = 8.4 Hz), 5.05 s (1H),
.34 d (2H, J = 17.0 Hz), 2.26 d (2H, J = 17.0 Hz),
2.15 d (2H, J = 16.3 Hz), 2.04 d (2H, J = 16.3 Hz), 1.02
7
9.03; H 7.78; N 4.12.
,3,6,6-Tetramethyl-9-(2-nitrophenyl)-3,4,6,7,9,10-
hexahydroacridine-1,8(2H,5H)-dione (3b). Off-white
2
3
13
s (6H), 0.87 s (6H). C NMR spectrum (125 MHz), δ,
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 86 No. 6 2016

1
416
FEKRI, NIKPASSAND
ppm: 27.4, 29.9, 32.9, 34.9, 51.0, 112.3, 123.5, 129.4, 146.3,
49.8, 154.9, 195.6. Calculated, %: C 70.03; H 6.63; N 7.10.
C H N O . Found, %: C 69.93; H 6.75; N 7.32.
9-(4-Fluorophenyl)-3,3,6,6-tetramethyl-3,4,6,7,9,10-
1
hexahydroacridine-1,8(2H,5H)-dione (3i). Off-white
–
1
solid, mp 113–115°C, IR spectrum (KBr), ν, cm :
23
26
2 4
1
3
355, 3047, 2958, 1618, 1498, 1147. H NMR
9-(2-Chlorophenyl)-3,3,6,6-tetramethyl-3,4,6,7,9,10-
spectrum (500 MHz), δ, ppm: 8.30 br.s (1H), 7.30 m
hexahydroacridine-1,8(2H,5H)-dione (3e). Off-white
–
1
(2H), 6.90 m (2H), 5.09 s (1H), 2.04–2.38 m (8H),
solid, mp 178–179°C, IR spectrum (KBr), ν, cm :
13
1
1.10 s (6H), 0.98 s (6H). C NMR spectrum (125 MHz),
3
400, 2980, 1660, 1465, 1355, 1040. H NMR spec-
δ, ppm: 27.4,30.0, 33.0, 41.0, 51.3, 113.3, 115.0 d
trum (500 MHz, CDCl ), δ, ppm: 7.47 d (1H, J =
3
2
3
(
JCF = 83.5 Hz), 129.7 d ( J = 31.0 Hz), 143.0,
CF
6
7
.4 Hz), 7.25 d (1H, J = 7.5 Hz), 7.01–7.19 m (1H),
.09 d (1H, J = 7.2 Hz), 5.04 s (1H), 2.45–2.62 m
1
1
49.9, 162.5 d ( J = 249.0 Hz), 196.5. Calculated, %:
CF
1
3
C 75.18; H 7.13; N 3.81. C23
5.12; H 7.29; N 3.73.
H26FNO . Found, %: C
2
(
4H), 2.10–2.30 m (4H), 1.14 s (6H), 1.05 s (6H). C
7
NMR spectrum (125 MHz), δ, ppm: 27.8, 29.7, 32.5,
4
1
6
6
1.2, 51.2, 114.2, 126.8, 127.6, 128.2 (two peaks),
30.6, 133.9, 163.5, 197.0. Calculated, %: C 71.96; H
.82; N 3.65. C H ClNO . Found, %: C 71.72; H
9
-(4-Hydroxyphenyl)-3,3,6,6-tetramethyl-3,4,6,7,9,10-
hexahydroacridine-1,8(2H,5H)-dione (3j). Off-white
solid, mp 156–157°C, IR spectrum (KBr), ν, cm :
252, 3012, 2942, 1672. H NMR spectrum (500 MHz),
δ, ppm: 7.72 d (2H, J = 7.4 Hz), 7.44 d (2H, J =
7.4 Hz), 5.11 s (1H), 2.34 d (2H, J = 17.0 Hz), 2.26 d
(2H, J = 17.0 Hz), 2.15 d (2H, J = 16.3 Hz), 2.04 d
2
3
26
2
–1
.55; N 3.81.
-(3-Chlorophenyl)-3,3,6,6-tetramethyl-3,4,6,7,9,10-
hexahydroacridine-1,8(2H,5H)-dione (3f). Off-white
1
3
9
–
1
solid, mp 214–216°C, IR spectrum (KBr), ν, cm :
1
13
3443, 3075, 2980, 1643. H NMR spectrum (500 MHz),
(2H, J = 16.3 Hz), 1.02 s (6H), 0.87 s (6H). C NMR
δ, ppm: 8.58 s (1H), 8.23 t (1H, J = 8.5 Hz), 7.67 d
spectrum (125 MHz), δ, ppm: 25.5, 28.9, 31.4, 36.3,
51.6, 117.8, 122.2, 128.3, 146.8, 148.3, 156.0, 193.1.
Calculated, %: C 75.59; H 7.45; N 3.83. C H NO .
(
1H, J = 8.5 Hz), 7.57 d (1H, J = 8.2 Hz), 5.08 s (1H),
1
3
2
.10–2.34 m (8H), 1.22 s (6H), 1.06 s (6H). C NMR
2
3
27
3
spectrum (125 MHz), δ, ppm: 27.5, 30.3, 32.7, 44.9,
Found, %: C 75.45; H 7.59; N 3.65.
5
1
1.7, 118.2, 127.8, 128.9, 129.5, 133.6, 149.0, 151.2,
63.0, 198.2. Calculated, %: C 71.96; H 6.82; N 3.65.
9-(4-Methoxyphenyl)-3,3,6,6-tetramethyl-3,4,6,7,9,10-
C H ClNO . Found, %: C 71.77; H 6.75; N 3.71.
hexahydroacridine-1,8(2H,5H)-dione (3k). Off-white
2
3
26
2
–
1
solid, mp 211–213°C, IR spectrum (KBr), ν, cm :
9-(4-Chlorophenyl)-3,3,6,6-tetramethyl-3,4,6,7,9,10-
1
3
384, 3094, 2961, 1631. H NMR spectrum (500 MHz),
hexahydroacridine-1,8(2H,5H)-dione (3g). Off-white
solid, mp 221–222°C, IR spectrum (KBr), ν, cm :
δ, ppm: 7.69 d (2H, J = 7.8 Hz), 7.47 d (2H, J =
–
1
7
0
2
1
3
.8 Hz), 5.10 s (1H), 2.32–2.04 m (8H), 1.06 s (6H),
1
3178, 3060, 2958, 1641, 1606, 1488, 1020. H NMR
13
.94 s (6H). C NMR spectrum (125 MHz), δ, ppm:
spectrum (500 MHz), δ, ppm: 8.06 br.s (1H), 7.32 d
8.7, 29.6, 32.6, 35.1, 51.7, 119.2, 123.9, 129.2, 145.6,
49.2, 155.0, 192.1. Calculated, %: C 75.96; H 7.70; N
.69. C H NO . Found, %: C 76.08; H 7.83; N 3.78.
(
2H, J = 8.3 Hz), 7.20 d (2H, J = 8.3 Hz,), 5.51 s (1H),
1
3
2
.17–2.33 m (8H), 1.15 s (6H), 1.03 s (6H). C NMR
2
4
29
3
spectrum (125 MHz), δ, ppm: 27.5, 30.0, 33.0, 41.1,
1.2, 113.3, 128.5, 129.9, 132.0, 145.6, 149.7, 196.5.
Calculated, %: C 71.96; H 6.82; N 3.65. C H ClNO .
5
9
,9'-{2,2'-[1,4-Phenylenebis(methylene)]bis(oxy)-
23
26
2
bis(2,1-phenylene)}bis[3,3,6,6-tetramethyl-3,4,6,7,9,10-
hexahydroacridine-1,8(2H,5H)-dione] (6a). Light
yellow solid, mp 210–211°C, IR spectrum (KBr), ν,
Found, %: C 72.06; H 6.95; N 3.43.
-(3-Bromophenyl)-3,3,6,6-tetramethyl-3,4,6,7,9,10-
hexahydroacridine-1,8(2H,5H)-dione (3h). Off-white
solid, mp 245–246°C, IR spectrum (KBr), ν, cm :
3
9
–
1
1
cm : 3288, 3060, 2954, 1631. H NMR spectrum
(500 MHz, DMSO-d ), δ, ppm: 7.29 d (2H, J =
–
1
6
1
280, 3080, 2970, 1640, 1555, 1470, 1060. H NMR
6.7 Hz), 7.25 s (4H), 7.02 t (2H, J = 7.4 Hz), 6.85 d
(2H, J = 8.2 Hz), 6.45 t (2H, J = 7.4 Hz), 5.10 s (2H),
spectrum (500 MHz), δ, ppm: 7.98 s (1H), 7.48 s (1H),
7
2
.35 m (2H), 7.11 t (1H, J = 7.6 Hz), 5.05 s (1H), 2.18–
.35 m (8H), 1.12 s (6H), 1.01 s (6H). C NMR
5.00 s (4H), 2.00–2.67 m (16H), 0.94 s (12H), 0. 86 s
1
3
13
(12H). C NMR spectrum (125 MHz, DMSO-d
), δ,
6
spectrum (125 MHz), δ, ppm: 27.5, 30.0, 33.1, 41.1,
ppm: 27.6, 29.7, 32.6, 40.9, 51.4, 67.3, 118.6, 120.6,
127.8, 127.5, 129.5, 137.4, 148.4, 149.9, 151.0, 158.3,
196.0. Calculated, %: C 77.75; H 7.12; N 3.52.
5
1
1.3, 113.1, 122.6, 127.5, 129.5, 130.0, 131.4, 149.3,
49.8, 196.3. Calculated, %: C 64.49; H 6.11; N 3.27.
C H BrNO . Found, %: C 64.66; H 6.32; N 3.15.
C H N O . Found, %: C 77.85; H 7.26; N 3.36.
54 60 2 6
2
3
26
2
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 86 No. 6 2016

BENZYL ALCOHOL-BASED SYNTHESIS OF MONO- AND BIS-DIHYDROPYRIDINES
1417
9
,9'-{3,3'-[1,4-Phenylenebis(methylene)]bis(oxy)-
27.3, 28.9, 33.8, 35.5, 50.9, 61.4, 119.2, 121.2, 122.8,
125.6, 133.8, 144.6, 150.3, 156.3, 194.5. Calculated,
%: C 76.26; H 7.80; N 3.48. C H N O . Found, %: C
bis(1,3-phenylene)}bis[3,3,6,6-tetramethyl-3,4,6,7,9,10-
hexahydroacridine-1,8(2H,5H)-dione] (6b). Light
yellow solid, mp 287–288°C, IR spectrum (KBr), ν,
5
1
62
2
6
76.66; H 7.82; N 3.51.
–
1
1
cm : 3282, 3066, 2954, 1635, 1483, 1367, 1208. H
9,9'-{2,2'-[Hexane-1,6-diylbis(oxy)]bis(2,1-phenyl-
NMR spectrum (500 MHz, DMSO-d ), δ, ppm: 7.49 t
2H, J = 7.8 Hz), 7.34 s (4H), 7.01 t (2H, J = 7.8 Hz),
.87 d (2H, J = 7.5 Hz), 6.94 s (2H), 6.62 t (2H, J =
.7 Hz), 5.05 s (2H), 4.97 s (4H), 1.94–2.99 m (16H),
.98 s (12H), 0.89 s (12H). C NMR spectrum
125 MHz, DMSO-d ), δ, ppm: 27.5, 29.9, 32.8, 33.8,
1.2, 70.1, 118.1, 121.4,123.9, 127.5, 129.1, 137.4,
48.8, 149.7, 150.4, 158.9, 196.0. Calculated, %: C
7.82; H 7.21; N 3.39. C H N O . Found, %: C
6
ene)}bis[3,3,6,6-tetramethyl-3,4,6,7,9,10-hexahyd-
(
roacridine-1,8(2H,5H)-dione] (6f). Off-white solid,
6
7
0
–1
mp 275–277°C, IR spectrum (KBr), ν, cm : 3290,
1
3
065, 2960, 1645, 1490, 1365, 1225. H NMR
1
3
spectrum (500 MHz, DMSO-d ), δ, ppm: 8.83 s (2H),
6
(
6
6
2
.71–7.26 m (8H), 5.10 s (2H), 3.97 br.s (4H), 1.96–
5
1
7
7
.29 m (20H), 1.01–1.06 m (4H), 0.97 s (12H), 0.90 s
13
(
12H). C NMR spectrum (125 MHz, DMSO-d ), δ,
6
5
4
60
2
6
ppm: 20.4, 21,9, 26.3, 28.0, 32.5, 35.6, 52.1, 60.1,
18.5, 120.1, 122.5, 127.3, 135.1, 147.7, 150.2, 157.3,
7.85; H 7.26; N 3.36.
1
9
,9'-{4,4'-[1,4-Phenylenebis(methylene)]bis(oxy)-
195.8. Calculated, %: C 76.81; H 7.93; N 3.45.
C H N O . Found, %: C 76.95; H 7.82; N 3.59.
bis]1,4-phenylene)}bis(3,3,6,6-tetramethyl-3,4,6,7,9,10-
hexahydroacridine-1,8(2H,5H)-dione] (6c). Light
yellow solid, mp 211–213°C, IR spectrum (KBr), ν,
5
2
64
2
6
CONCLUSIONS
–
1
1
cm : 3278, 3066, 2954, 1637. H NMR spectrum
(
8
500 MHz, CDCl , DMSO-d ), δ, ppm: 7.84 d (4H, J =
.4 Hz), 7.29 s (4H), 7.09 d (4H, J = 8.4 Hz), 5.10 s
In conclusion, the catalytic system constituted by
Al(HSO , NaNO , and NaBr was studied as a mild
3
6
)
4
3
2
(
0
2H), 4.98 s (4H), 2.18-2.40 m (16H), 1.08 s (12H),
.97 s (12H); C NMR spectrum (125 MHz, DMSO-
and efficient catalyst for the synthesis of mono and bis
-dihydropyridines, in which alcohols instead of
aldehydes were used as starting compounds. Remark-
able advantages of the method are the use of cheap,
non-toxic, easy-to handle, and reusable catalyst, simple
work-up procedure, short reaction time, high yield and
better purity of the products, and environmental safety.
1
3
d6), δ, ppm: 26.3, 29.6, 32.0, 33.5, 51.7, 67.3, 117.3,
26.3, 136.1, 149.4, 151.8, 157.1, 195.7. Calculated,
: C 77.77; H 7.23; N 3.21. C H N O . Found, %: C
1
%
7
5
4
60
2
6
7.85; H 7.26; N 3.36.
9,9'-{2,2'-[Butane-1,4-diylbis(oxy)]bis(1,2-phenyl-
ene)}bis[3,3,6,6-tetramethyl-3,4,6,7,9,10-hexahyd-
ACKNOWLEDGMENTS
roacridine-1,8(2H,5H)-dione] (6d). Off-white solid,
–
1
mp 269–271°C, IR spectrum (KBr), ν, cm : 3290,
The authors are grateful to the Research Council of
the Payame Noor University for the partial support of
this study.
1
3
060, 2960, 1655. H NMR spectrum (500 MHz,
DMSO-d ), δ, ppm: 7.67 s (2H), 6.80–7.06 m (6H),
6
5
.12 s (2H), 4.06 s (4H), 1.98–2.35 m (20H), 1.04 s
1
3
(
12H), 0.92 s (12H). C NMR spectrum (125 MHz,
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6
6
1
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0
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9,9'-{2,2'-[Pentane-1,5-diylbis(oxy)]bis(2,1-phenyl-
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3
6
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6
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