M. Abdollahi-Alibeik, E. Heidari-Torkabad / C. R. Chimie 15 (2012) 517–523
519
Table 1
Optimization of reaction conditions for the synthesis of quinoxalines in the presence of catalytic amount of TPA/MCM-41.
Entry
Catalyst
Solvent
Catalyst amount (mg/mol%)
Time (min)
Yield (%)
1
2
3
4
5
6
7
8
9
5% TPA/MCM-41
10% TPA/MCM-41
15% TPA/MCM-41
10% TPA/MCM-41
10% TPA/MCM-41
10% TPA/MCM-41
10% TPA/MCM-41
10% TPA/MCM-41
10% TPA/MCM-41
EtOH
EtOH
EtOH
EtOH
EtOH
EtOAc
15/0.026
15/0.052
15/0.078
10/0.035
20/0.07
2
0.25
2
98
99
94
90
95
99
99
92
99
5
10
1
15/0.052
15/0.052
15/0.052
15/0.052
CH
CH
3
CN
Cl
20
44
21
2
2
CHCl
3
1
1
7
8
446, 1340; H NMR (500 MHz, CDCl
3
):
d
(ppm) = 7.39–
2.5.9. 6-Nitro-2,3-difuran-2-yl-quinoxaline (Table 2, entry 9)
.48 (m, 6H), 7.60 (t, 4H, J = 6.5 Hz),8.33 (d, 1 H, J = 9.1 Hz),
Orange solid, mp 171–173 8C (Lit. [18] 164–166 8C); IR
13
À1
.56 (dd, 1H, J = 9.1, 2.2 Hz), 9.19 (d, 1H, J = 2.3 Hz);
): (ppm) = 123.73, 126.06,
28.89, 130.07, 130.20, 130.26, 130.33, 131.192, 138.47,
38.54, 140.42, 144.02, 148.32, 156.13, 156.75.
C
(Neat):
y
max (cm ): 3129, 1617, 1563, 1520, 1467, 1300,
1
NMR (125.77 MHz, CDCl
3
d
3
1160, 1058; H NMR (400 MHz, CDCl ): d (ppm) = 6.63–
1
1
6.66 (m, 2H), 6.85 (dd, 1H, J = 3.4, 0.6 Hz), 6.91 (dd, 1H,
J = 3.4, 0.6 H), 7.69–7.71 (m, 2H), 8.25 (d, 2H, J = 9.2 Hz),
1
3
8
.51 (dd, 2H, J = 9.2, 3.2 Hz), 9.04 (d, 1H, J = 3.2); C NMR
2.5.5. 2,3-Dihydro-5,6-diphenylpyrazine (Table 2, entry 5)
(100.62 MHz, CDCl ): (ppm) = 112.31, 112.44, 114.51,
3
d
White solid, mp 160–163 8C (Lit. [23] 163 8C); IR (Neat):
115.37, 123.66, 125.37, 130.47, 139.26, 143.02, 144.23,
144.73, 145.01, 145.49, 147.95, 149.40, 150.17.
À1
1
y
(
max (cm ): 3050, 2945, 1560, 1552, 1443; H NMR
): (ppm) = 3.73 (s, 4H), 7.28 (t, 4H,
J = 7.5 Hz), 7.34 (t, 2H, J = 7 Hz), 7.43 (d, 4H, J = 7.5 Hz);
NMR (125.77 MHz, CDCl ): (ppm) = 46.25, 128.33,
28.54, 130.05, 138.21, 160.73.
500 MHz, CDCl
3
d
13
C
2.5.10. 2,3-Bis(4-methoxyphenyl)quinoxaline (Table 2,
entry 10)
3
d
1
White solid, mp 151–152 8C (Lit. [25] 151–152 8C); IR
À1
(
Neat):
y
max (cm ): 3010, 3090, 1605, 1511, 1394, 1346,
1
2
.5.6. 2,3-Difuran-2-yl-quinoxaline (Table 2, entry 6)
1240, 1026; H NMR (500 MHz, CDCl
3
): d = 3.8 (S, 6 H), 6.91
Pale brown solid, mp 132–134 8C (Lit. [24] 129–130 8C);
(d, 4 H, J = 6.73 Hz), 7.53 (d, 4H, J = 6.63 Hz),7.76(dd, 2 H),
À1
13
IR (Neat):
058; H NMR (500 MHz, CDCl
y
max (cm ): 3107, 1571, 1535, 1479, 1163,
3
8.16 (dd, 2 H); C NMR (125.77 MHz, CDCl ): d = 55.74,
114.21, 129.44, 129.95, 131.68, 132.17, 141.51, 153.46,
160.60.
1
1
2
7
3
):
d
(ppm) = 6.59–6.60 (m,
H), 6.7 (d, 2 H, J= 3.31 Hz), 7.6 (d, 2H, J = 1.02 Hz), 7.77–
13
.79 (m, 2 H), 8.15–8.18 (m, 2 H); C NMR (125.77 MHz,
): 112.35, 113.43, 129.56, 130.83, 141.074, 143.09,
44.66, 151.25.
CDCl
3
2.5.11. 6-Methyl-2,3-bis(4-methoxyphenyl)quinoxaline
(Table 2, entry 11)
1
White solid, mp 123–126 8C (Lit. [26] 124–126 8C); IR
À1
2
.5.7. 6-Methyl-2,3-difuran-2-yl-quinoxaline (Table 2,
(Neat):
y
max (cm ): 3050, 2900, 1655, 1604, 1511, 1343,
1
entry 7)
3
1246, 1027; H NMR (400 MHz, CDCl ): d (ppm) = 2.52 (s,
Pale brown solid, mp 118–120 8C (Lit. [18] 112–114 8C);
3H), 3.75 (s, 6H), 6.79 (d, 4H, J = 7.2 Hz), 7.40 (d, 4H,
À1
IR (Neat):
147, 1062; H NMR (400 MHz, CDCl
y
max (cm ): 3110, 2900, 1618, 1569, 1490, 1350,
J = 7.2 Hz), 7.47 (d, 1H, 7.6 Hz), 7.84 (s, 1H), 7.93 (d, 1H,
1
13
1
3
3
):
d
(ppm) = 2.52 (s,
3
7.6 Hz); C NMR (100.62 MHz, CDCl ): d (ppm) = 21.89,
H), 6.48–6.49 (m, 2H), 6.54–6.56 (m, 2H), 7.51 (dd, 2H,
55.31, 113.74, 127.88, 128.53, 131.20, 131.24, 132.87,
139.54, 140.00, 141.14, 152.17, 152.90, 160.01.
J = 8.6, 1.8 Hz), 7.54–7.55 (m, 1H), 7.84 (s, 1H), 7.95 (d, 1H,
13
J = 8.4 Hz); C NMR (100.62 MHz, CDCl
3
): d (ppm) = 21.95,
1
1
1
11.87, 111.89, 112.58, 112.83, 127.99, 128.64, 132.80,
39.12, 140.74, 141.14, 141.87, 142.62, 144.01, 144.14,
50.92.
3. Result and discussion
3.1. Catalyst characterization
2
.5.8. 6-Benzoyl-2,3-difuran-2-yl-quinoxaline (Table 2,
The structure of TPA/MCM-41 is well known and has
been reported in many papers. However, the small
difference in the procedure of preparation of the MCM-
41 still requires some characterization experiments.
The morphology of the MCM-41 was studied by
scanning electron microscopy (SEM) (Fig. 1). SEM image
shows the MCM-41 as agglomerated nanoparticles with
the size range less than 100 nm.
entry 8)
Pale brown solid, mp 118–120 8C (Lit. [13] 132–134 8C);
À1
1
IR (Neat):
NMR (400 MHz, CDCl
y
max (cm ): 3135, 1654, 1597, 1154, 1065; H
): (ppm) = 6.60–6.63 (m, 2H), 6.76–
.79 (m, 2H), 7.53–7.57 (m, 3H), 7.64–7.69 (m, 2H), 7.90–
.92 (m, 2H), 8.27 (d, 2H, J = 1.6 Hz), 8.50 (t, 1H, J = 1.2 Hz);
3
d
6
7
13
3
C NMR (100.62 MHz, CDCl ): d (ppm) = 112.09, 112.22,
1
1
1
13,62, 114,26, 128.55, 129.59, 130.11, 130.29, 132.29,
32.84, 137.11, 138.55, 139.54, 142.42, 143.47, 143.97,
44.56, 144,89, 150.52, 195.67.
The FT-IR spectra of TPA, MCM-41 and TPA/MCM-41
with 10 wt.% loading amounts of TPA are shown in Fig. 2.
The bulk TPA shows four peaks at 1080, 981, 887 and