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30 min. Aer that, the mixture was stirred for 30 min for d (ppm) 3.37 (s, 3H, OMe), 6.17 (s, 1H, CHbenzylic), 6.45–6.67 (m,
complete releasing of HCl. The mixture was then ltered and 3H, ArH), 7.05–7.33 (m, 5H, ArH and NH), 7.42–7.58 (m, 2H, ArH),
the solid residue was washed with MeOH and dried at room 7.81 (d, 2H, ArH), 8.51 (bs, 1H, OH); 13C NMR (75 MHz, DMSO-
temperature to obtain (NiFe2O4@Cu)(MMT-SO3H) MNPs.
d6) d (ppm) 35.9, 56.1, 104.2, 112.2, 115.2, 119.7, 120.4, 123.3,
131.2, 133.6, 144.5, 147.4, 152.9, 165, 168.1.
2.10.6. 7-(3-Methoxyphenyl)-7,14-dihydro-6H,8H-dichromeno
[4,3-b:30,40-e]pyridine-6,8-dione (4f). FT-IR (KBr, n cmꢂ1): 3421,
3073, 3066, 1645, 1603, 1523, 1417, 1268, 1205, 1043, 973, 897, 761;
1H NMR (300 MHz, DMSO-d6) d (ppm) 3.72 (s, 3H, OMe), 5.45 (s,
1H, CHbenzylic), 6.82 (s, 1H, ArH), 7.05–7.35 (m, 7H, ArH and NH),
2.9. A general procedure for Hantzsch synthesis of coumarin-
based 1,4-DHPs catalyzed by (NiFe2O4@Cu)SO2(MMT) MNPs
In a round-bottom ask (15 mL), a mixture of 4-hydrox-
ycoumarin (2 mmol), aromatic aldehyde (1 mmol) and
ammonia (2 mmol) in water (2 mL) was prepared. Magnetically
nanoparticles of (NiFe2O4@Cu)SO2(MMT) (10 mg) was then
added and the resulting mixture was stirred at 60 ꢀC for an
appropriate time (Table 6). Aer completion of the reaction
(monitored with by TLC), DMSO (2 mL) was added to the
reaction mixture: the catalyst was insoluble in DMSO and easily
separated by an external magnetic eld. Aer that, a saturated
solution of NaCl was added. In a meanwhile of the addition, 1,4-
DHP was precipitated, ltered and washed with n-hexane.
7.35–7.60 (m, 1H, ArH), 7.83 (bs, 1H, ArH), 8.32 (bs, 3H, ArH); 13
C
NMR (75 MHz, DMSO-d6) d (ppm) 35.7, 94.1, 103.7, 109.7, 113.7,
119.7, 122.4, 123, 141.9, 144.5, 152.9, 159.5, 165, 168.2.
2.10.7. 7-(p-Tolyl)-7,14-dihydro-6H,8H-dichromeno[4,3-b:30,40-
e]pyridine-6,8-dione (4h). FT-IR (KBr, n cmꢂ1): 3433, 2927, 1671,
1613, 1412, 1189, 1039, 763; 1H NMR (300 MHz, DMSO-d6) d (ppm)
2.19 (s, 3H, Me), 6.20 (s, 1H, CHbenzylic), 6.94 (s, 4H, ArH), 7.18–7.25
(m, 5H, ArH and NH), 7.41–7.55 (m, 2H, ArH), 7.78 (d, 2H, ArH); 13
C
NMR (75 MHz, DMSO-d6) d (ppm) 22.2, 36.1, 103.9, 120.4, 124.5,
128.7, 131.2, 133.9, 152.9, 165, 168.1.
2.10.8. 7-(4-Nitrophenyl)-7,14-dihydro-6H,8H-dichromeno
[4,3-b:30,40-e]pyridine-6,8-dione (4j). FT-IR (KBr, n cmꢂ1): 3463,
2.10. Selected spectral data
2.10.1. 7-Phenyl-7,14-dihydro-6H,8H-dichromeno[4,3-b:30,40-
e]pyridine-6,8-dione (4a). FT-IR (KBr, n cmꢂ1): 3435, 3196, 3049, 3202, 3067, 2912, 1667, 1608, 1534, 1513, 1339, 1341, 1181,
1659, 1610, 1540, 1406, 1266, 1185, 1108, 1039, 901, 755; 1H NMR 1109, 1043, 942, 850, 762; 1H NMR (300 MHz, DMSO-d6) d (ppm)
(300 MHz, DMSO-d6) d (ppm) 6.30 (s, 1H, CHbenzylic), 7.01–7.38 (m, 6.33 (s, 1H, CHbenzylic), 7.15–7.30 (m, 5H, ArH and NH), 7.30–
10H, ArH and NH), 7.45–7.55 (m, 2H, ArH), 7.82 (d, 2H, ArH); 13
C
7.40 (m, 2H, ArH), 7.45–7.61 (m, 2H, ArH), 7.75–7.85 (m, 2H,
NMR (75 MHz, DMSO-d6) d (ppm) 36.5, 103.7, 115.9, 120.1, 123.5, ArH), 8.01–8.13 (m, 2H, ArH); 13C NMR (75 MHz, DMSO–d6)
124.5, 125.4, 127, 128.2, 131.5, 142.5, 152.8, 165.3, 168.3.
d (ppm) 37.1, 103.2, 116, 120.1, 122.8, 124.2, 125.7, 131.6,
2.10.2. 7-(2-Chlorophenyl)-7,14-dihydro-6H,8H-dichromeno 145.7, 151.9, 153, 164.8, 168.4.
[4,3-b:30,40-e]pyridine-6,8-dione (4b). FTIR (KBr, n cmꢂ1): 3418,
2.10.9. 7-(3-Nitrophenyl)-7,14-dihydro-6H,8H-dichromeno
3182, 1769, 1604, 1489, 1406, 1188, 1041, 944, 758; 1H NMR (300 [4,3-b:30,40-e]pyridine-6,8-dione (4k). FT-IR (KBr, n cmꢂ1): 3437,
MHz, DMSO) d 6.15 (s, 1H, CHbenzylic), 7.15–7.40 (m, 8H, ArH and 3213, 3066, 1611, 1530, 1415, 1345, 1183, 1045, 850, 758; 1H
NH), 7.40–7.60 (m, 3H, ArH), 7.80 (d, 2H, ArH); 13C NMR (75 MHz, NMR (300 MHz, DMSO-d6) d (ppm) 6.34 (s, 1H, CHbenzylic), 7.21–
DMSO) d 36.5, 103.2, 115.2, 115.9, 120.3, 123.4, 124.4, 127.4, 7.82 (m, 11H, ArH and NH), 7.88 (s, 1H, ArH), 7.97 (s, 1H, ArH);
130.88, 131.2, 133.1, 140.8, 152.8, 164.3, 164.3, 168.1.
2.10.3. 7-(4-Chlorophenyl)-7,14-dihydro-6H,8H-dichromeno 123.5, 123.5, 129.8, 131.7, 145.6, 153, 164.8, 168.4.
[4,3-b:30,40-e]pyridine-6,8-dione (4c). FT-IR (KBr, n cmꢂ1): 3183,
2.10.10. 7-(4-Chloro-3-nitrophenyl)-7,14-dihydro-6H,8H-
13C NMR (75 MHz, DMSO-d6) d (ppm) 36.7, 103, 116, 120.1,
3046, 2594, 1611, 1540, 1407, 1186, 1099, 1029, 903, 757; 1H NMR dichromeno[4,3-b:30,40-e]pyridine-6,8-dione (4l). FT-IR (KBr,
(300 MHz, DMSO-d6) d (ppm) 6.23 (s, 1H, CHbenzylic), 6.93 (s, 1H, n cmꢂ1): 3429, 3100, 2900, 1664, 1608, 1537, 1406, 1352, 1188,
NH), 7.05–7.18 (m, 2H, ArH), 7.18–7.35 (m, 6H, ArH), 7.45–7.60 1042, 834, 764; 1H NMR (300 MHz, DMSO-d6) d (ppm) 6.29 (s, 1H,
(m, 2H, ArH), 7.80 (d, 2H, ArH); 13C NMR (75 MHz, DMSO-d6) CHbenzylic), 7.15–7.30 (m, 5H, ArH and NH), 7.35–7.45 (m, 1H,
d (ppm) 36.2, 103.5, 115.9, 120.2, 123.3, 124.5, 128, 128.9, ArH), 7.45–7.62 (m, 3H, ArH), 7.68 (s, 1H, ArH), 7.75–7.85 (m, 2H,
129.8, 131.4, 166.8.
ArH); 13C NMR (75 MHz, DMSO-d6) d (ppm) 36.4, 102.8, 116,
2.10.4. 7-(3-Hydroxy-4-methoxyphenyl)-7,14-dihydro-6H,8H- 120.1, 123.5, 124.5, 131.4, 132.8, 144.6, 153, 164.7, 168.4.
dichromeno[4,3-b:30,40-e]pyridine-6,8-dione (4d). FT-IR (KBr,
n cmꢂ1): 3411, 3142, 3047, 2927, 2851, 1661, 1611, 1562, 1510,
3. Results and discussion
3.1. Synthesis and characterization of (NiFe2O4@Cu)
1406, 1270, 1098, 1028, 906, 760; 1H NMR (300 MHz, DMSO-d6)
d (ppm) 3.68 (s, 3H, OMe), 6.14 (s, 1H, CHbenzylic), 6.42–6.55 (m,
1H, ArH), 6.55–6.65 (m, 1H, ArH), 6.65–6.75 (m, 1H, ArH), 7.15–
SO2(MMT) MNPs
7.27 (m, 5H, ArH and NH), 7.41–7.58 (m, 2H, ArH), 7.82 (d, 2H, Synthesis of the magnetic sulfonyl-bridged clay composite,
ArH), 8.60 (bs, 1H, OH); 13C NMR (75 MHz, DMSO-d6) d (ppm) NFCSM, was carried out through a ve-step procedure: (i)
35.1, 54.1, 104, 112.4, 114.8, 115.8, 117.6, 120.4, 131.3, 135.2, preparation of NiFe2O4 MNPs via a solid state grinding of
145.5, 152.9, 165.2, 168.2.
Ni(OAc)2$4H2O and Fe(NO3)3$9H2O in the presence of NaOH,
2.10.5. 7-(4-Hydroxy-3-methoxyphenyl)-7,14-dihydro-6H,8H- (ii) mixing of NiFe2O4 MNPs with an aqueous solution of
dichromeno[4,3-b:30,40-e]pyridine-6,8-dione (4e). FT-IR (KBr, CuCl2$2H2O, (iii) reduction of Cu2+ ions to Cu0 with NaBH4 to
n cmꢂ1): 3410, 3218, 3069, 2931, 1651, 1607, 1514, 1448, 1403, afford NiFe2O4@Cu MNPs, (iv) preparation of acid-activated
1277, 1185, 1114, 1034, 760; 1H NMR (300 MHz, DMSO-d6) sodium montmorillonite (Na+-MMT-SO3H) by stirring of
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RSC Adv., 2019, 9, 8002–8015 | 8005