All chemicals were purchased from Merck and Sigma Aldrich and used without purification. X-ray diffraction (XRD) patterns were obtained using the Philips PW-1830. The Electro thermal 9100 apparatus was used to determine of melting points. Magnetic analysis curves were recorded using the VSM model MDKB from Danesh Pajohan Kavir Co. Kashan, Iran. The FT-IR Spectra were detected using the Shimadzu IR-470 spectrophotometer. The 1H and 13C spectra of the products were recorded with a Bruker DRX 400-Avance spectrometer. TEM images were obtained by TEM Philips EM-208S. The SEM images were recorded via a SEM VEGA3. The EDS analysis was done using MAP, LINE SCAN. Termogravimetric analysis (TGA) was recorded with TGA STA6000.Preparation of Fe3O4@SiO2@Pr-NH2
The synthetic steps of Fe3O4@SiO2 were followed according to previously reported literature10. 2.5 ml of APTES were added to 1 g of Fe3O4@SiO2 which was subjected to ultrasonic waves in 30 ml of dry toluene. 24 h were spent stirring the mixture under reflux conditions. Finally, it was collected using an external magnetic field, washed with toluene and dried.Preparation of Fe3O4@SiO2@NH2-TCT1 g of the nanoparticle from the previous step was subjected to ultrasonic waves in dry THF (40 ml). In the next step, cyanuric chloride (TCT) (0.5 g) and Et3N (3 mmol) were added to it and stirred for 6 h at a temperature of 0–5 °C under nitrogen gas. Finally, the nanoparticles were separated with the help of the magnetic field and washed several times with THF.Preparation of Fe3O4@SiO2@NH2-TCT-Mel1 g of Fe3O4@SiO2@NH2-TCT nanoparticles were dispersed in 40 ml of dry THF. Then, 8 mmol of melamine and 1 ml of Et3N were separately dissolved in dry THF and slowly added to the reaction container containing nanoparticles. The solution was mechanically stirred at 0–5 °C for 5 h and 8 h at room temperature under a nitrogen atmosphere. Fe3O4@SiO2@NH2-TCT-Mel as separated using the magnet, washed with THF, and then dried.Preparation of Fe3O4@SiO2@NH2-TCT-Mel-PrBr1 g of Fe3O4@SiO2@NH2-TCT-Mel nanoparticles were dispersed in 30 ml of dry toluene. Then 6 ml of 1,3-dibromopropane and 0.1 g sodium iodide were added in a nitrogen atmosphere and refluxed for 30 h. After finishing the reaction, it was separated with a magnet, washed with ethyl acetate, and then dried.Preparation of Fe3O4@SiO2@NH2-TCT-Mel-Pr-thiosemicarbazide-Cu(II) (Fe3O4@SiO2@NTMPThio-Cu)1 g Fe3O4@SiO2@NH2-TCT-Mel-Pr was suspended in 50 ml of dry toluene and sonicated for 30 min. Following this, 1 g of thiosemicarbazide was dissolved in it and refluxed for 24 h. Eventually, the desired Fe3O4@SiO2-Pr-Thiosemicarbazide was separated using a strong magnet and washed several times with EtOH to leave only the thiosemicarbazide that had chemically bonded with the magnetic substrate. In the next step, 1 g of the catalyst and 6 mmol of Cu(OAc)2 in 50 ml of EtOH were placed under reflux conditions and stirred for 24 h. Finally, after separating the catalyst, it was washed several times with EtOH (Scheme 1).Scheme 1Preparation of Fe3O4@SiO2@NTMPThio-Cu catalyst.General procedure for the synthesis of xanthenesA mixture of dimedone (2 mmol), and/or β-naphthol (2 mmol), aromatic aldehyde (1 mmol), and 15 mg Fe3O4@SiO2@NTMPThio-Cu in the solvent-free conditions and was stirred for 10 min at 25 °C. Following the reaction’s completion (follow up with help from TLC), EtOH /H2O (1:1) was added to the reaction medium, and the catalyst was collected by the magnetic field. The solid product recrystallized from EtOH (Scheme 2).Scheme 2Preparation of xanthenes in the presence of Fe3O4@SiO2@NTMPThio-Cu.General procedure for the synthesis of spirooxindole-pyran derivatives (10a–t)1 mmol of isatins, 1 mmol of malononitrile, 1 mmol of 1,3-dicarbonyl compounds, and 15 mg of Fe3O4@SiO2@NTMPThio-Cu were stirred at 25 °C under solvent-free conditions. After completing the reaction (which was monitored by TLC), EtOH was added to the mixture. After separating the catalyst, the products were purified in EtOH (Scheme 3).Scheme 3Preparation of spirooxindole-pyran derivatives in the presence of Fe3O4@SiO2@NTMPThio-Cu.Spectral data for selected productsCompound (4a) δH (400 MHz, CDCl3): 1.04 (s, 6H), 1.15 (s, 6H), 2.21 and 2.27 (ABq, 4H), 2.49 (s, 4H), 4.74 (s, 1H), 7.21–7.28 (m, 4H). δC (100 MHz, CDCl3): 27.5, 29.5, 32.6, 32.4, 40.9, 50.6, 115.6, 128.2, 129.8, 132.0, 142.4, 162.5, 196.3.Compound (4d) δH (400 MHz, CDCl3): 1.00 (s, 6H), 1.16 (s, 6H), 2.18 and 2.31 (ABq, 4H), 2.52 (s, 4H), 4.86 (s, 1H), 7.49 (d, 2H), 8.15 (d, 2H,). δC (100 MHz, CDCl3): 27.4, 30.0, 32.3, 32.6, 41.0, 50.6, 111.0, 114.6, 123.5, 130.1, 147.4, 151.5, 163.0, 196.2.Compound (5a) δH (400 MHz, CDCl3): 6.51 (s, 1H), 7.14 (d, 2H), 7.44–7.53 (m, 6H), 7.61–7.65 (m, 2H), 7.84 (d, 2H), 8.57 (d, 2H), 8.34 (d, 2H). δC (100 MHz, CDCl3): δ 37.4, 116.8, 118.2, 122.5, 124.4, 126.9, 128.7, 128.9, 129.1, 129.5, 131.1, 131.3, 132.1, 143.5, 148.7.Compound (5c) δH (400 MHz, CDCl3): 2.15 (s, 3H), 6.47 (s, 1H), 6.99 (d, 2H), 7.26–7.43 (m, 4H), 7.49 (d, 2H), 7.60 (t, 2H), 7.78 (d, 2H), 7.85 (d, 2H), 8.43 (d, 2H). 13C NMR (CDCl3): 20.8, 37.6, 117.4, 118.0, 122.7, 124.2, 126.7, 128.1, 128.7, 129.1, 131.0, 131.4, 135.8, 142.1, 148.6.Compound (5f) δH (400 MHz, CDCl3): 6.545 (t, 1H), 7.27 (t, 1H), 7.40–7.84 (m, 12 H), 8.30 (d, 2H), 8.43 (s, 1H). 13C NMR (CDCl3): 37.6, 115.8, 118.1, 121.6, 122.0, 122.7, 124.5, 127.2, 129.0, 129.4, 129.5, 131.0, 134.2, 146.9, 148.1, 148.7.Compound (6b) δH (400 MHz, CDCl3): 0.98 (s, 3H), 1.16 (s, 3H), 2.29 and 2.35 (2H), 2.60 (s,), 5.70 (s, 1H), 7.15–7.19 (m, 2H,), 7.30–7.33 (m, 2H), 7.35 (d, 1H), 7.40–7.44 (m, 1H), 7.45–7.49 (m, 1H), 7.80–7.83 (m, 2H), 7.92 (d, 1H). δC (100 MHz, CDCl3): 27.2, 29.4, 32.3, 34.2, 41.6, 51.0, 114.0, 117.0, 123.45, 124.9, 127.2, 128.4, 128.5, 128.6, 130.1, 129.9, 131.3, 131.6, 132.0, 143.2, 147.8, 164.0, 197.0.Compound (6d) δH (400 MHz, CDCl3): δ 0.99 (s, 3H), 1.18 (s, 3H), 2.26 and 2.39 (ABq, 2H), 2.74 (s, 2H), 5.85 (s, 1H), 7.40 (d, 1H), 7.42–7.51 (m, 2H), 7.60 (d, 2H), 7.84–7.89 (m, 3H), 8.09 (d, 2H). 13C NMR (100 MHz, CDCl3): 27.1, 31.1, 34.3, 36.1, 42.4, 52.0, 114.0, 116.2, 118.2, 123.3, 125.8, 126.6, 128.5, 129.9, 129.9, 131.2, 131.4, 146.8, 152.0, 164.3, 197.0.Compound (10a) δH (400 MHz, CDCl3): 1.00 (s, 3H), 1.04 (s, 3H), 2.14 (q, 2H), 2.54 (d, 2H), 6.78 (d, 1H), 6.88 (t, 1H), 6.97 (d, 1H), 7.15 (t, 1H), 7.24 (s, 2H), 10.41 (s, 1H). δC (100 MHz, CDCl3): 28.4, 29.0, 32.4, 47.2, 50.4, 57.9, 109.6, 111.2, 117.7, 122.1, 123.4, 128.6, 134.8, 142.4, 159.2, 164.5,178.5, 195.3.Compound (10f) δH (400 MHz, DMSO): δ 3.05 (s, 3H), 3.7 (s, 3H), 6.83 (d, 1H), 7.22 (d, 2H), 7.29 (s, 1H), 7.66 (s, 2H), 10.66 (s, 1H). δC (100 MHz, CDCl3,): 28.11, 29.81, 48.07, 57.43, 86.96, 111.13, 117.17, 124.52, 126.24, 128.82, 136.16, 141.50, 150.13, 152.70, 158.64, 159.98, 177.85.Compound (10m) δH (400 MHz, DMSO): 6.87 (d, 1H), 6.95 (t, 1H), 7.22 (d, 2H), 7.51 (t, 1H), 7.55 (t,1H), 7.67 (s, 1H), 7.76 (t, 1H), 7.95 (d, 1H), 10.7 (s, 1H). δC (100 MHz, CDCl3): 20.15, 27.22, 36.73, 47.61, 57.25, 111.01, 111.70, 123.92, 126.08, 128.50, 137.03, 141.38, 159.18, 167.053, 178.40, 195.71.Compound (10o) δH (400 MHz, DMSO): 1.87–198 (m, 2H), 2.25 (t, 2H), 2.66 (t, 2H), 6.81 (d, 1H), 7.15 (s, 1 H), 7.20 (d, 1H), 7.31 (s, 2H), 10.57 (s, 1H). δC (100 MHz, CDCl3): 20.15, 27.22, 36.73, 47.61, 57.25, 111.01, 111.70, 123.92, 126.08, 128.50, 137.03, 141.38, 159.18, 167.053, 178.40, 195.71.Compound (10l) δH (400 MHz, DMSO): δ 2.74 (s,1H), 2.89 (s,1H), 6.81 (d, 1H), 7.22 (d, 1H), 7.39 (s, 1H), 7.49 (s, 2H), 10.67 (s, 1H). δC (100 MHz, CDCl3): 47.47, 57.19, 91.42, 111.12, 117.20, 124.84, 126.36, 128.91, 135.51, 141.50, 153.59, 158.72, 159.75, 174.53 and 177.56.Ethical approvalThis work does not contain any studies with human participants or animals performed by any of the authors.
Fe3O4@SiO2@NTMPThio-Cu: a sustainable and eco-friendly approach for the synthesis of heterocycle derivatives using a novel dendrimer template nanocatalyst
