Tandem synthesis of N,N'-alkylidenebisamides promoted by nano-SnCl4.SiO2

Article abstract of DOI:10.1007/s12039-013-0519-2

A highly efficient procedure for the preparation of N,N'- alkylidenebisamides in the presence of nano-SnCl4.SiO2 as a catalysis described. N,N'-alkylidenebisamides have been prepared via condensation reaction of various aldehydes and amides. All of the re

Full text of DOI:10.1007/s12039-013-0519-2

c
J. Chem. Sci. Vol. 125, No. 6, November 2013, pp. 1481–1486. ꢀ Indian Academy of Sciences.
Tandem synthesis of N, Nꢀ-alkylidenebisamides promoted
by nano-SnCl4.SiO2
BIBI FATEMEH MIRJALILI∗ and MOHAMMAD ALI MIRHOSEINI
Department of Chemistry, College of Science, Yazd University, Yazd, P.O. Box 89195-741, Iran
e-mail: fmirjalili@yazduni.ac.ir
MS received 5 January 2013; revised 1 May 2013; accepted 27 May 2013
Abstract. A highly efficient procedure for the preparation of N,Nꢁ-alkylidenebisamides in the presence of
nano-SnCl4.SiO2 as a catalysis described. N,Nꢁ-alkylidenebisamides have been prepared via condensation
reaction of various aldehydes and amides. All of the reactions proceeded in high yields and in moderately short
reaction times.
Keywords. N,Nꢁ-alkylidenebisamides; aldehydes; amides; nano-SnCl4.SiO2.
1. Introduction
2. Experimental
Bisamides are of considerable interest in the synthe- The chemicals were used without any additional purifi-
sis of peptidomimetic compounds.1,2 They are key cation. The products were characterized by FT-IR,
constituent of many biologically active and pharma- 1H-NMR, and a comparison of their physical proper-
ceutical compounds such as introduction of gem- ties with those reported in the literature. FT-IR spec-
diaminoalkyl residues in retro-inverso pseudopeptide tra were run on a Bruker, Eqinox 55 spectrometer. A
derivatives by treating the corresponding amide with Bruker (DRX-400 Avance) NMR was used to record
1
iodobenzenebistrifluoroacetate.3,4
the H NMR spectra. Melting points were determined
Generally, symmetrical alkylidenebisamides are syn- by a Buchi melting point B-540 B.V.CHI appara-
thesized by the direct reaction of aldehydes with amides tus. BANDELIN Sonopuls HD 3200 ultrasonic appa-
under suitable catalytic condition. In this topic, various ratus (20 kHz, 150 W) was used for sonication. The
catalysts such as triflic acid,5 p-toluene sulphonic acid,6 microwave oven Kenwood, 1300 W and Mixer Mill
SiO2-MgCl2,7 CC-activatd DMSO,8 sulphamic acid,9 (MM 400) in 25 Hz frequency were used for running
phosphotungstic acid,10 boric acid11 and silica sup- the described reactions. Elemental analyses were done
ported polyphosphoric acid (SiO2-PPA)12 have been by Costech ECS 4010 CHNS-O analyser.
examined. However, each method has certain restric-
tions with regards to scope and reaction conditions,
for example, long reaction times, low yields, difficult
work-up and harsh reaction conditions.
2.1 General procedure for the synthesis
of N,Nꢁ-alkylidenebisamides
SnCl4·SiO2 13–15 is bench-top catalyst which has many
A mixture of aldehyde (1 mmol), amide (2 mmol),
advantages such as simple preparation, reusability, easy
n-hexane (5 ml) and nano-SnCl4.SiO2 (0.01 g) was
handling and high efficiency. Because of the important
refluxed for appropriate time. The progress of the reac-
role of solid acids in organic synthesis16,17 and in con-
tions was monitored by TLC. After completion of the
tinuation of our investigations on this area,18–22 we have
reaction, the mixture was cooled to room temperature
studied nano-SnCl4.SiO2 efficiency in the synthesis of
and filtered to isolation of product and catalyst. The cata-
N,Nꢁ-alkylidenebisamides under mild conditions.
lyst was separated from product by boiling ethanol. The
crude solid product was purified by recrystallization in
ethanol:water, 80:20, or ethanol.
2.1a N,Nꢁ-(phenylmethylene)dibenzamide (table 1,
∗For correspondence
¯
−1
entry 1): FT-IR: ∪ (ATR, neat, cm ):3275 (N-H),
1481

1482
Bibi Fatemeh Mirjalili and Mohammad Ali Mirhoseini
Table 1. Preparation of N,Nꢁ-alkylidenebisamides in the presence of nano-SnCl4.SiO2 .
a
Entry
1
R1
R2
Product
Yield (%)b/time (h)
90/2.1
M.P. ◦C (Ref.)
C6H5
C6H5
213–215 (214–216)11
O
O
Ph
N
H
N
H
Ph
NO
O
2
224–225 (224–226)11
240–241 (242–244)11
O
2
3
3-NO2-C6H4
4-NO2-C6H4
CH2 =CH-
86/4.9
94/1.9
H
C=CH
N
H
N
H
CH=CH
2
2
NO
2
C6H5
O
O
Ph
N
H
N
Ph
H
NO2
4
4-NO2-C6H4
OCH3
85/0.81
197–198
O
O
MeO
N
H
N
OMe
H
Cl
Cl
5
6
7
2,4-di-Cl-C6H3
3-NO2-C6H4
OCH3
C6H5
CH3
91/0.9
94/1.4
75/4.5
249–251 (252–254)
237–238
O
O
MeO
N
H
N
H
OMe
2
NO
O
O
Ph
N
H
N
H
Ph
Cl
Cl
2,4-di-Cl-C6H3
265–266
O
O
H
C
N
H
N
CH
3
3
H
C3H7
O
O
8
CH3-CH2-CH2-
3-NO2-C6H4
C6H5
OCH3
C6H5
C6H5
80/2.3
91/2.1
89/6
171–172
184–185
Ph
N
N
Ph
H
H
NO
O
2
9
O
OMe
N
N
OMe
H
H
O
O
10
11
1,3,5-trioxane
Ph-CH2-CH2-
124–125
N
Ph
Ph
N
H
H
NHCOPh
71/4
247–249 (248–249)6
NHCOPh
NHCOPh
12
Ph-CH2 =CH2-
C6H5
69/2
199–201
NHCOPh
NHCOPh
NHCOPh
13
14
CHOCH2-CH2-CH2-
(CH3)2-CH-
C6H5
C6H5
79/6.5
74/5.1
128–129
126–127
NHCOPh
NHCOPh
NHCOPh
NHCOPh
N O2
15
16
4-NO2-C6H4
2-OH-C6H4
CH3
96/4.8
72/5
235–237 (233–235)7
178–179
O
O
H3C
N
N
CH3
H
H
OH
O
C6H5
O
Ph
N
N
H
Ph
H
aReaction conditions: amide (2 mmol), aldehyde (1 mmol), nano-SnCl4.SiO2 (0.01 g)
bIsolated yields

Tandem synthesis of N,Nꢁ-alkylidenebisamides promoted by nano-SnCl4.SiO2
1483
1650 (C=O), 1480 (N-H), 715, 799; 1H NMR (DMSO- 2.1f N ,Nꢁ-(3-nitrophenylmethylene)dibenzamide
−1
¯
d6, ppm): δ 9.01 (d, J = 7.7 Hz, 2 H, N-H),7.92 (d, (table 1, entry 6): FT-IR: ∪ (ATR, neat, cm ):3250
J = 7.8 Hz, 2 H),7.56 (t, J = 7.1 Hz, 1 H),7.49 (t, (N-H), 1646 (C=O),1340 (N-H), 1339, 1533, 1505,
1
J = 7.5 Hz, 3 H),7.39 (t, J = 7.5 Hz, 1 H), 7.32 (t, 715, 695; HNMR (DMSO-d6, ppm): δ 9.2 (d, J =
J = 7.1 Hz, 1 H), 7.05 (t, J = 7.7 Hz, 1 H, CH). Ele- 7.4 Hz, 2 H, N-H), 8.35 (sbr, 1 H), 8.2 (dd, J = 6.9 and
mental analysis. Found, %: C 76.55; H 5.38; N 8.38. 1.37 Hz, 2 H), 7.96 (s, I H), 7.93 (d, J = 8.4 Hz, 4 H),
C21H18N2O2. Calculated, %: C 76.34; H 5.49; N 8.48.
7.71 (t, J = 7.9 Hz, 1 H), 7.58 (t, J = 7.2 Hz, 2 H), 7.5
(t, J = 7.8 Hz, 4 H), 7.50 (s, 4 H), 7.09 (t, J = 7.3 Hz,
1 H, CH). Elemental analysis. Found, %: C 66.89; H
4.67; N 11.39. C21H17N3O4. Calculated, %: C 67.19; H
4.56; N 11.19.
2.1b N ,Nꢁ-(3-nitrophenylmethylene)diacr−y1lamide
¯
(table 1, entry 2): FT-IR: ∪ (ATR, neat, cm ):3242
(N-H), 1664 (C=O), 1628, 1346, 1528, 1520, 966, 703,
667; 1H NMR (DMSO-d6, ppm): δ 9.22 (d, J = 7.4 Hz,
2 H, N-H), 8.20 (d, J = 1.7 Hz, 2 H), 7.82 (d, J =
7.8 Hz, 1 H), 7.70 (t, J = 8.0 Hz, 1 H), 6.74 (t, J =
7.5 Hz, 1 H, CH), 6.35 (dd, J = 17.1 and 10.2 Hz, 2 H),
6.17 (dd, J = 17.1 and 1.7 Hz, 2 H), 5.68 (dd, J = 10.2
and 1.7 Hz, 2 H). Elemental analysis. Found, %: C
56.56; H 4.58; N 15.38. C13H13N3O4. Calculated, %: C
56.72; H 4.76; N 15.27.
2.1g N,Nꢁ-(2,4-dichlorophenylmethylene)diacetamide
−1
¯
(table 1, entry 7): FT-IR: ∪ (ATR, neat, cm ):3285
1
(N-H), 1665 (C=O), 1425, 1518, 856, 749, 643; H
NMR (DMSO-d6, ppm): δ 8.54 (d, J = 7.2 Hz, 2 H,
N-H), 7.62 (d, J = 1.6 Hz, 1 H), 7.5 (m, 2 H), 6.6 (t,
J = 7.5 Hz, 1 H, CH), 1.84 (s, 6H, CH3). Elemental
analysis. Found, %: C 47.90; H 4.48; N 10.08; Cl
25.62. C11H12N2O2Cl2. Calculated, %: C 48.02; H
4.40; N 10.18; Cl 25.77.
2.1c N ,Nꢁ-(4-nitrophenylmethylene)dibenzamide
−1
1
¯
(table 1, entry 3): FT-IR: ∪ (ATR, neat, cm ):3256
(N-H), 1649 (C=O), 1343, 1507, 1546, 852; H NMR
2.1h N,Nꢁ-(n-propylmethylene)diben−z1amide (table 1,
(DMSO-d6, ppm): δ 9.2 (d, J = 5.0 Hz, 2 H, N-H),
8.26 (d, J = 6.9 Hz, 2 H), 7.93 (d, J = 5.6 Hz, 4 H),
7.75 (d, J = 6.9 Hz, 2 H), 7.58 (s, 2 H), 7.50 (s, 4
H), 7.09 (brs, 1 H, CH). 13C-NMR (DMSO-d6, ppm):
166.7, 134.4, 132.6, 129.2, 128.9, 128.4, 124.3. Ele-
mental analysis. Found, %: C 66.99; H 4.78; N 11.15.
C21H17N3O4. Calculated, %: C 67.19; H 4.56; N 11.19.
¯
entry 8): FT-IR: ∪ (ATR, neat, cm ):3232 (N-H),
1
1643 (C=O), 1484, 1600, 1530; H NMR (DMSO-d6,
ppm): δ 8.52 (d, J = 7.6 Hz, 2 H, N-H), 7.86 (d,
J = 7.1 Hz, 4 H), 7.55 (t, J = 7.1 Hz, 2 H), 7.47
(t, J = 7.7 Hz, 4 H), 5.85 (m, 1 H, CH), 1.85 (q,
J = 7.2 Hz, 2 H, CH2), 1.37 (m, 2 H, CH2), 0.938 (t,
J = 7.3 Hz, 3 H, CH3). Elemental analysis. Found, %:
C 73.09; H 6.57; N 9.39. C18H20N2O2. Calculated, %:
C 72.95; H 6.80; N 9.45.
2.1d N,Nꢁ-(4-nitrophenylmethylene)di-methylcarbox-
¯
amide (table 1, entry 4): FT-IR: ∪ (ATR, neat,
cm−1):3306 (N-H), 1706 (C=O), 1600, 1349, 1530,
2.1i N,Nꢁ-(3-nitrophenylmethylene)dimethylcarbox-
1
1550, 1251, 1195, 871; HNMR (DMSO-d6, ppm):
¯
amide (table 1, entry 9): FT-IR: ∪ (ATR, neat,
δ 8.2 (d, J = 7.5 Hz, 2 H), 8.1 (brs, 2 H, N-H), 7.6
(d, J = 7.6 Hz, 2 H), 6.24 (brs, 1 H, CH), 3.58 (s, 6
H, OMe); 13C-NMR (DMSO-d6, ppm): 156.6, 148.1,
147.9, 128.7, 124.3, 61.9, 52.5. Elemental analysis.
Found, %: C 46.50; H 4.70; N 14.90. C11H13N3O6.
Calculated, %: C 46.65; H 4.63; N 14.84.
cm−1):3287 (N-H), 1701 (C=O), 1515, 1343, 1556,
1255, 1032, 674, 783, 809; 1HNMR (DMSO-d6, ppm):
δ 8.24 (s, 1 H), 8.17 (d, J = 8.3 Hz, 1 H), 8.15 (sbr, 2
H, NH), 7.82 (d, J = 7.6 Hz, 1 H), 7.67 (t, J = 7.9 Hz,
1 H), 6.25 (t, J = 7.9 Hz, 1 H, CH), 3.61(s, 6 H, OMe).
Elemental analysis. Found, %: C 46.82; H 4.56; N
14.28. C11H13N3O6. Calculated, %: C 46.65; H 4.63; N
14.84.
2.1e N,Nꢁ-(2,4-dichlorophenylmethylene)dimethyl-
¯
carboxamide (table 1, entry 5): FT-IR: ∪ (ATR, neat,
cm−1):3309 (N-H), 1708 (C=O), 1550, 720, 699, 643;
1H NMR (DMSO-d6, ppm): δ 8.04 (sbr, 2 H, N-H),
7.61 (d, J = 2 Hz, 1 H), 7.57 (d, J = 8.4 Hz, 1 H),
6.24 (dd, J = 8.4 and 1.9 Hz, 1H), 6.24 (t, J = 7.5 Hz,
1 H, CH), 3.55 (s, 6 H, OMe); 13C-NMR (DMSO-d6,
ppm): 156.3, 137.5, 134.1, 133.8, 130.3, 129.5, 128.1,
59.8, 52.4. Elemental analysis. Found, %: C 42.92; H
3.90; N 9.08; Cl 23.02. C11H12N2O4Cl2. Calculated, %:
C 43.02; H 3.94; N 9.12; Cl 23.09.
2.1j N,Nꢁ-(methylene)d−ib1enzamide (table 1, entry 10):
¯
FT-IR: ∪ (ATR, neat, cm ):3308 (N-H), 1634 (C=O),
1487, 1578, 1526, 1448; 1H NMR (DMSO-d6, ppm): δ
9.03 (t, J = 5.5 Hz, 2 H, N-H), 7.9 (d, J = 7.1 Hz,
4 H), 7.55 (t, J = 7.1 Hz, 2 H), 7.48(t, J = 7.1 Hz,
4 H), 4.84(t, J = 5.5 Hz, 2 H, CH2). Elemental analy-
sis. Found, %: C 69.99; H 4.97; N 11.48. C15H14N2O2.
Calculated, %: C 70.85; H 5.55; N 11.02.

1484
Bibi Fatemeh Mirjalili and Mohammad Ali Mirhoseini
2.1k N ,Nꢁ-(2-phenylethylmethylene)dibenzamide 2 H). Elemental analysis. Found, %: C 72.49; H 5.67;
−1
¯
(table 1, entry 11): FT-IR: ∪ (ATR, neat, cm ):3299 N 10.39. C33H32N4O4. Calculated, %: C 72.24; H 5.88;
1
(N-H), 1637 (C=O), 1508, 1579, 1545, 690, 756; H N 10.21.
NMR (DMSO-d6, ppm): δ 8.64 (d, J = 7.5 Hz, 2 H,
2.1n N,Nꢁ-(iso-propylmethylene)dibenzamide (table 1,
N-H), 7.88 (d, J = 7.2 Hz, 4 H), 7.54 (t, J = 7.3 Hz,
2 H), 7.48 (t, J = 7.7 Hz, 4 H), 7.28 (m, 4 H), 7.17
(m, 1 H), 5.85 (m, 1 H, CH), 2.69 (t, J = 8.2 Hz, 2 H,
CH2), 2.17 (dd, J = 15.4 and 7.3 Hz, 2 H, CH2). Ele-
mental analysis. Found, %: C 76.89; H 6.24; N 7.95.
C23H22N2O2. Calculated, %: C77.07; H 6.19; N 7.82.
−1
¯
entry 14): FT-IR: ∪ (ATR, neat, cm ):3234 (N-H),
1
1737 (C=O), 1480, 1643, 1561; H NMR (DMSO-
d6, ppm): δ 8.40 (d, J = 8.2 Hz, 2 H, N-H), 7.85(d,
J = 7.2 Hz, 4H), 7.54 (t, J = 7.2 Hz, 2 H), 7.48 (t,
J = 7.7 Hz, 4 H), 5.67 (q, J = 8 Hz, 1 H, CH), 2.2
(m, 1 H, CH), 0.97 (d, J = 6.7 Hz, 6 H, CH3). Ele-
mental analysis. Found, %: C 66.89; H 6.8; N 9.45.
C18H20N2O2. Calculated, %: C 72.95; H 6.8; N 9.45.
2.1l N,Nꢁ-(3-phenyl-2-ene-propylene)dibenzamide
−1
¯
(table 1, entry 12): FT-IR: ∪ (ATR, neat, cm ):3274
1
(N-H), 1647 (C=O), 1484,1504, 1543, 690, 756; H
NMR (DMSO-d6, ppm): δ 8.87 (d, J = 6.8 Hz, 2 H,
N-H), 7.92 (d, J = 7.4 Hz, 4 H), 7.86 (t, J = 7.9 Hz, 2
H), 7.56 (t, J = 7.2 Hz, 2 H), 7.48 (m, 4 H), 7.35 (m, 2
H), 7.28 (t, J = 7.3 Hz, 1 H), 6.69 (d, J = 14.7 Hz, 1
H, CH), 6.65 (m, 2 H). Elemental analysis. Found, %:
C 77.99; H 5.37; N 7.59. C23H20N2O2. Calculated, %:
C 77.51; H 5.66; N 7.86.
2.1o N,Nꢁ-(2-hydroxyphenylmethylene)dibe−n1zamide
¯
(table 1, entry 16): FT-IR: ∪ (ATR, neat, cm ):3406-
3268 (O-H and N-H), 1639 (C=O), 1425, 1126, 758;
1H NMR (DMSO-d6, ppm): δ 9.02 (d, J = 7.4 Hz, 2 H,
N-H), 8.03 (d, J = 7.3 Hz, 2 H), 7.81 (d, J = 7.3 Hz,
3 H), 7.69 (m, 1 H), 7.52 (m, 3 H), 7.45 (m, 5 H),
2.1m N,N,Nꢁ,Nꢁ-(1,5-pentylene)tetrabenzamide (table 1,
R1
−1
¯
nano-SnCl4.SiO2
entry 13): FT-IR: ∪ (ATR, neat, cm ):3364, 3162 (N-
R1CHO
+
R2CONH2
R2CONH
HNOCR2
H), 1655 (C=O), 1448, 1622, 1577, 683, 774; 1H NMR
(DMSO-d6, ppm): δ 8.53 (d, J = 7.6 Hz, 4 H, N-H),
7.83 (m, 8 H), 7.53 (t, J = 7.3 Hz, 4 H), 7.44 (t, J =
7.4 Hz, 8 H), 5.86 (m, 2 H, CH), 1.94 (m, 4 H), 1.5 (m,
H
-hexane, reflux
n
Scheme 1. Synthesis of N,Nꢁ-alkylidenebisamides in the
presence of nano-SnCl4.SiO2.
Table 2. Synthesis of N, Nꢁ-(phenylmethylene)dibenzamides.
O
O
Cat.
PhCONH2
+
CHO
N
N
Ph
Ph
H
H
Entry
Catalyst (g)
SnCl4.SiO2 (0.05)
Conditions
Time (h)/yield (%)a
Ref.
1
2
2
4
5
6
7
8
S.F./Mixer Mill
S.F./M.W.
1/5
0.05/50
1/45
1/55
7/81
1/88
0.6/25
1/94
0.5/40
1/91
1/83
0.83/96
0.83/90
0.83/75
3/73
1.5/71
20/70
40 min/80
SnCl4.SiO2 (0.05)
SnCl4.SiO2 (0.05)
SnCl4.SiO2 (0.05)
SnCl4.SiO2 (0.05)
SnCl4.SiO2 (0.05)
SnCl4.SiO2 (0.05)
SnCl4.SiO2 (0.05)
SnCl4.SiO2 (0.05)
SnCl4.SiO2 (0.06)
SnCl4.SiO2 (0.04)
Nano-SnCl4.SiO2 (0.01)
Nano-SnCl4.SiO2 (0.01), 2nd run
Nano-SnCl4.SiO2 (0.01), 3rd run
SiO2-MgCl2 (0.025)
CC (1.2 equiv)-activatd DMSO (7.0 equiv)
Phosphortungstic acid (0.3 mmol)
Boric acid (0.3 mmol)
S.F./60◦C
S.F./90◦C
CHCl3/reflux
EtOAc/reflux
EtOAc/sonication
n-Hexane/reflux
n-Hexane/sonication
n-Hexane/reflux
n-Hexane/reflux
n-Hexane/reflux
n-Hexane/reflux
n-Hexane/reflux
Solvent-free/100
Toluene/70
-
-
9
10
11
12
13
14
15
16
17
18
-
-
-
-
7
8
10
11
Toluene/reflux
Microwave
aIsolated yield

Tandem synthesis of N,Nꢁ-alkylidenebisamides promoted by nano-SnCl4.SiO2
1485
nano-SnCl4.SiO2
PhCHO
+
PhNHCOCH3
+ H2NCOC6H5
PhCH(HNCOC6H5)2
PhNHCOCH3
+
n-hexane, reflux
Scheme 2. Chemoselectivity in formation of N,Nꢁ-alkylidenebisamides for primary amides
in the presence of secondary amides.
nano-SnCl4.SiO2
PhCHO
+ H2NSO2C6H4CH3
H NCOC H
+
PhCH(HNCOC6H5)2
H2NSO2C6H4CH3
+
2
6
5
n-hexane, reflux
Scheme 3. Chemoselectivity in formation of N,Nꢁ-alkylidenebisamides for primary amides
in the presence of sulfonamides.
O
O
Ph
Next, the scale of this procedure was explored using
a wide range of aldehydes containing electron-donating
or electron-withdrawing groups attaching to aromatic
ring (table 1, scheme 1). In all cases, aromatic alde-
hydes containing electron-withdrawing groups gave
higher yield of products in shorter time than benzalde-
hyde (table 1, entries 1 and 3).
nano-SnCl4.SiO2
PhCHO
H2NCONH2
2
+
H2NCNH-CH-HNCNH2
n-hexane, reflux
Scheme 4. Formation of N,Nꢁ-alkylidenebisamides from
urea.
7.35 (m, 1 H), 7.26 (t, J = 7.3 Hz, 1 H, CH). Ele-
mental analysis. Found, %: C 72.99; H 5.17; N 7.99.
C21H18N2O3. Calculated, %: C 72.82; H 5.24; N 8.09.
Aromatic aldehydes have reacted in this protocol in
lower times and higher yields, than aliphatic aldehydes
(table 1, entries 1, 8, 10, 11) specially aliphatic alde-
hydes with steric hinders (table 1, entry 14) or con-
jugated aliphatic aldehydes (table 1, entry 12). 1,3,5-
trioxane was used as formaldehyde source to pro-
duce N,Nꢁ-(methylene)dibenzamide (table 1, entry 10)
and the both of aldehyde group in glutardialdehyde
have reacted in this process and yield the tetra-amide
derivative (table 1, entry 13). The aromatic aldehydes
with electron-withdrawing group have reacted faster
than aromatic aldehydes with electron-releasing group
(table 1, entries 3 and 16). Aromatic amides have
reacted with an active aldehyde with higher yield in
lower time (table 1, entries 3 and 15). The OMe group
in methyl carbamate caused higher yield of correspond-
ing amide in lower time than acetamide (table 1, entry
5 and 7).
This protocol is special for primary amides and
not for secondary amides or primary sulphonamides
(schemes 2 and 3).
Reaction of benzaldehyde with urea produces corre-
sponding bisamide with good yield (scheme 4).
Additional efforts about chemoselectivity of this
protocol have shown that aromatic aldehydes versus
aliphatic aldehydes or aromatic amides versus aliphatic
amides have not shown any chemoselectivity.
¯
2.1p N-benzylidene urea (scheme 1): FT-IR: ∪
(ATR, neat, cm−1):3272 (N-H), 1670 (C=O), 1467,
1
1268, 1060, 868. H NMR (DMSO-d6, ppm): 7.98 (d,
J = 5.7 Hz, 2 H), 7.6 (d, J = 6.5 Hz, 1 H), 7.5 (t,
J = 6.4 Hz, 2 H), 7.4 (d, J = 6.5 Hz, 2 H), 6.45 (t,
J = 5.8 Hz, 1 H), 5.7 (brs., 2 H), 5.4 (brs., 2 H). Ele-
mental analysis. Found, %: C 51.52; H 5.67; N 26.79.
C9H12N4O2. Calculated, %: C 51.92; H 5.81; N 26.91.
3. Results and discussion
Our aim was to develop new synthetic methods using
heterogeneous catalysts to reduce risks to humans and
the environment. To prepare N,Nꢁ-alkylidenebisamides
and find the best reaction conditions, the reaction of
benzamide and benzaldehyde was examined under vari-
ous conditions and different quantities of SnCl4.SiO2
or nano-SnCl4.SiO2 (table 2). The reaction proceeded
efficiently in n-hexane under reflux condition using
0.05 g of SnCl4.SiO2 or 0.01 g of nano-SnCl4.SiO2 with
1 mmol of aldehyde and 2 mmol of amide (table 2,
entries 8 and 12). The reusability of the nano-
SnCl4·SiO2 catalyst was also examined. After each run,
CH2Cl2 was added and the product was filtered, the sol-
vent evaporated and the residue (catalyst) was washed
with CH2Cl2 and reused. Apparently, treatment with
4. Conclusion
CH2Cl2 removes tar efficiently from the catalyst surface We have demonstrated simple method for the syn-
(table 2, entries 13 and 14). This catalyst was reusable, thesis of preparation of N,Nꢁ-alkylidenebisamides with
although a gradual decline in activity was observed.
using nano-SnCl4.SiO2 as highly efficient and reusable

1486
Bibi Fatemeh Mirjalili and Mohammad Ali Mirhoseini
catalyst. Short reaction times, high yields, a clean pro- 10. Harichandran G, Amalraj S D and Shanmugam P 2011
Indian J. Chem. Part B 50 77
11. Harichandrana G, Amalraja S D and Shanmugam P 2011
J. Iranian Chem. Soc. 8 298
cess, simple methodology and easy work-up conditions
are some advantages of this protocol.
12. Shafiee M R 2011 J. Saudi Chem. Soc. doi: 10.1016/j.
jscs.2011.06.005, in press
Acknowledgement
13. Mirjalili1 B F, Bamoniri A and Mirhoseini M A 2012
Chem. Heterocycl. Comp. 48 856
14. Mirjalili1 B F, Bamoniri A and Mirhoseini M A 2012
J. Nanostruct. 2 241
Authors thank the Research Council of Yazd University
for the financial support.
15. Mirjalili B F, Hashemi M M, Sadeghi B and Emtiazi H
2009 J. Chinese Chem. Soc. 56 386
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