G Model
CCLET-2652; No. of Pages 5
2
J. Safaei-Ghomi et al. / Chinese Chemical Letters xxx (2013) xxx–xxx
R
R
SnCl . nano SiO
2
2
CN
CN
O
O
O
O
O
O
O
CN
O
3
O
O
O
O
2
reflux
Ethanol
reflux
Ethanol
O
NH2
O
R
+
5a-i
4a-i
H
O
1
Scheme 1. SnCl2/nano SiO2 catalyzed synthesis of polyfunctionalized 4H-pyrans.
dihydrate (0.28 g) was added to a suspension of nano particles of
silica gel (3.075 g) in dichloromethane (DCM) (25.0 mL). The
mixture was stirred at room temperature overnight. Then the
solvent was removed under reduced pressure and the residue was
heated at 100 8C under vacuum for 5 h to furnish SnCl2/nano SiO2.
The prepared SnCl2/nano SiO2 has been structurally characterized
by EDAX and SEM analysis.
(KBr, cmÀ1):
(400 MHz, DMSO-d6):
1H), 3.94 (q, 2H, J = 7.2 Hz), 4.27 (s, NH2), 6.93–7.4 (CH aromatic);
13C NMR (400 MHz, DMSO-d6):
15.3, 18.6, 36.6, 60.9, 63.4, 111.5,
116.8, 120.6, 133.9, 135.8, 156.7, 159.1, 160.3, 165.9. Anal. calcd.
for C16H16O4N2: C, 53.03; H, 4.14; N, 7.73. Found: C, 52.91; H, 4.10;
N, 7.80.
n
3401, 3319 (NH2), 2210 (CN), 1692(C55O); 1H NMR
d
1.10 (t, 3H, J = 7.2 Hz), 2.28 (s, 3H), 2.48 (s,
d
Ethyl-6-amino-5-cyano-4-(3-methoxyphenyl)-2-methyl-4H-py-
ran-3-carboxylate (5h): Yellow crystal; 83%, mp: 264–265 8C, FT-IR
2.2. General procedure for the preparation of diethyl 4-aryl-2,6-
dimethl-4H-pyran-3,5-dicarboxylate (4a–i)
(KBr, cmÀ1):
(400 MHz, DMSO-d6):
3H), 3.97 (s, 1H), 4.10 (s, NH2), 4.45 (q, 2H, J = 6.8 Hz), 6.51–7.85
(CH aromatic); 13C NMR (400 MHz, DMSO-d6):
11.2, 17.2, 40.1,
n
3405, 3315 (NH2), 2206 (CN), 1706 (C55O); 1H NMR
d
1.61 (t, 3H, J = 6.8 Hz), 2.12 (s, 3H), 3.83 (s,
A mixture of aldehyde (2 mmol), ethyl acetoacetate (4 mmol),
and nano silica supported tin (II) chloride (0.15 mol%) was refluxed
in ethanol (10 mL) for the appropriate time (monitored by TLC
analysis). The hot reaction mixture was filtered to separate the
catalyst and filtrate was solidified after cooling to room tempera-
ture. Then, ice water was added to mixture. The organic phase was
extracted with dichloromethane, washed with water and dried
with Na2SO4. The solvent was removed under reduced pressure.
The crude products were purified by recrystallization (ethanol and
water) with sufficient purity for spectral analysis.
d
57.9, 61.1, 63.8, 105.5, 111.2, 117.9, 119.8, 123.4, 130.7, 141.8,
158.2, 159.9, 162.5, 170.2. Anal. calcd. for C17H18O4N2: C, 64.96; H,
5.73; N, 8.91. Found: C, 64.87; H, 5.66; N, 8.97.
3. Results and discussion
According to literature reports, utilities of the heterogeneous
solid-supported materials as new environmentally friendly
catalysts for the synthesis of biologically active molecules have
increased. Hence, we describe a simple and efficient method for the
synthesis of polyfunctionalized 4H-pyrans using the environmen-
tal friendly and reusable nano silica supported tin (II) chloride as a
catalyst herein. The catalyst was prepared by reacting of tin (II)
chloride with silica under favorable conditions (Scheme 2). In order
to study the morphology and dimension of SnCl2/nano SiO2, SEM
image of SnCl2/nano SiO2 was obtained and shown in Fig. 1.
These results show that the size of commercial silicagel and
synthesized SnCl2/nano SiO2 are till about 20 nm (Fig. 1). In the
EDAX pattern of SnCl2/nano SiO2 (Fig. 2), Sn, Cl, Si and O elements
are indicated. This analysis is detecting that SnCl2 is supported in
nano silicagel.
To identify the structure of this catalyst, we studied IR spectra of
SnCl2/nano SiO2 (Fig. 3). In the IR spectrum of SnCl2/nano SiO2, the
Sn–Cl, Sn–O, Si–OH and Si–O–Si resonances were observed in
1559, 563, 3347 and 1061 cmÀ1, respectively. Based on these
results, we suggest the following structure for SnCl2/nano SiO2.
We would like to report the preparation of polyfunctionalized
4H-pyran using reactions involving arylaldehydes, ethylacetoace-
tate, and malononitrile (Scheme 1). We chose the reaction of
2.3. General procedure for the preparation of ethyl-6-amino-5-cyano-
4-aryl-2-methyl-4H-pyran-3-carboxylate (5a–i)
A mixture of aldehyde (2 mmol), malononitrile (2 mmol), ethyl
acetoacetate (2 mmol), and nano silica supported tin (II) chloride
(0.15 mol%) was refluxed in ethanol (5 mL) for the appropriate
time (monitored by TLC analysis). The hot reaction mixture was
filtered to separate the catalyst and filtrate was solidified after
cooling to room temperature. The solid product was consecutively
washed with hexane (2 mL), ethyl acetate (2Â 0.5 mL), and dried.
Diethyl 4-(3-methoxyphenyl)-2,6-dimethl-4H-pyran-3,5-dicar-
boxylate (4h): Yellow crystal; 85%; mp: 91–94 8C, FT-IR (KBr,
cmÀ1):
n
3020 (C–H), 1682 (C55O); 1H NMR (400 MHz, CDCl3):
d
1.42 (t, 3H, J = 6.8 Hz), 1.72 (s, 3H), 3.81 (s, 2H), 3.90 (s, 1H), 4.10 (q,
2H, J = 6.8 Hz), 6.58–7.17 (CH aromatic); 13C NMR (400 MHz,
CDCl3):
d 14.5, 17.6, 48.1, 52.8, 64.2, 106.4, 112.5, 116.7, 120.7,
128.8, 141.1, 155.6, 162.3, 166.9. Anal. calcd. for C20H23O6: C,
66.85; H, 6.40. Found: C, 66.79; H, 6.48.
Ethyl-6-amino-5-cyano-4-(4-bromophenyl)-2-methyl-4H-pyran-
3-carboxylate (5e): Orange crystal; 95%; mp: 264–265 8C, FT-IR
Cl
Sn
Cl
Cl
Sn
H
H
H
overnight at r.t.
DCM
O
O
+ HCl (g)
O
O
O
O
O
O
O
O
Si
Si
Si
Si
Si
Si
Si
Si
O
O
O
O
Scheme 2. Reaction of SnCl2 with silicagel.
Please cite this article in press as: J. Safaei-Ghomi, et al., SnCl2/nano SiO2: A green and reusable heterogeneous catalyst for the synthesis