In the present study, hollow MgO/SiO2 nanocatalyst with great base properties was made. This heterogeneous catalyst was a synthesis in several steps to create a great active area and decrease the density of the catalyst. The base hollow catalyst framework for the reaction of cyclohexanone, malononitrile and benzaldehyde to the synthesis of 1H-isocromene from Michael addition and aldol reaction at room temperature. All the reaction flowing was excellent in the yield of productand reaction times. At the end of the reaction, the nanocatalyst separated by simple filtration and reuse in several runs elsewhere.
Research Article
Preparation and Characterization of Hollow MgO/SiO2 Nanocomposites and using as Reusable Catalyst for Synthesis of 1H-Isochromenes
https://doi.org/10.21203/rs.3.rs-488543/v1
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Benzaldehyde
Nanocatalyst
1H-Isocromene
Cyclohexanone
Malononitrile
Hollow
Michael addition
The 1H-isochromene derivatives are a special structural style commonly appearance in a numerous of naturally and non-naturally products,(Butin et al., 2005; Hasan et al., 2015; Singh and Bodiwala, 2010; Tomás-Mendivil et al., 2015) which has represented as “advantaged structure” in various medicinally and related compounds due to its significant biological effects counting antitumor properties (Mondal et al., 2003; Morimoto et al., 2011; Shishido et al., 2008; Wang et al., 1998). Some natural compounds that include the isochromene were flaccidin separated of the orchids, Dendrobium amoenum also Coelogyne flaccida and also the numerous of compounds which separated from Cannabis sativa, can be observed as isochromenederivatives (Papadakis et al., 1983). Three derivatives of Ulmusdavidiana which comes from Korea are utilized in orientalmedicines for the usage of edema, inflammations, and stomach cancer.The enormousvalue of these compounds have inspired much effort to advance a vast number of influential and dependable procedures for their syntheses (Wang et al., 2017). Outdated 1H-isochromene synthesized with dimerization of benzopyrylium salts in acid conditional (Verin et al., 1991). The shortage of substrate range and the trouble in the supply of benzopyrylium salts was a disadvantage for this method. For solving this problem, direct and economical ways have been established to the synthesis of 1H-isochromenes via difference catalyst such as transition-metal-catalyzed and organic functional catalyzed.
The preparation of solid heterogeneous nanocatalyst with exact control the site of unique functionalities was commonly required in the organic reaction. In contrast, the solid catalysts attended with lacking clear morphology such as the hollow compound with small density and the great explicit surface area. Hollow catalyzed and nanoparticle wall, hollow spheres via nanometre or micrometre dimension often display singular chemical and physical properties dissimilar from dense particles.
Hollow spheres have used in many field, for example electrics, light-weight filler, optics selective adsorption, magnetics, drug delivery, medicine-release capsules, and catalysis (Budov, 1994; Cao et al., 2010; Chen et al., 2004; Fang et al., 2012; Ikeda et al., 2007; Russell et al., 2014). Consequently, there has been abundant interest in arranging hollow compound with altered arrangements in latest years. In earlier reports, the hollow structure with amorphous shells or nanocrystalline and hard template or soft template were ready in diversity courses. In the hard template structure, the first coating is formed on the core and then the hard template (core) is eliminated by chemical or thermal method to form hollow structure. To fabricate hollow spheres variability of solid particles have been utilized as hard templates like polystyrene spheres, silica particles, carbon spheres(Caruso et al., 2001; Hentze et al., 2003; Imhof, 2001; Titirici et al., 2006; Wang et al., 2006) The hard template technique is the great method for the construction of hollow spheres: hollow spheres with altered dimensions can be attained by the usage of colloid particles with a particular size, and the thickness wall of hard template hollow particles is due to reaction restrictions. In the soft template method, regularly usage of emulsions, vesicles, and micelles molecules which formed via self-assembly to template(Lai et al., 2012; Li et al., 2005; Liu et al., 2013; Sasidharan and Nakashima, 2014; Wang et al., 2008).
In this research, it was prepared the hollow MgO/SiO2 nanoparticles with the great surface active base area and used in the reaction of cyclohexanone, malononitrile and benzaldehyde for synthesis of 1H-isochromene under mild condition.
Chemicals
All material and solvents were used as the starting resources attained deprived of further purification cyclohexanone, malononitrile, benzaldehyde, cetyltrimethyl ammonium bromide (CTAB), tetraethyl orthosilicate (TEOS), ammonium, were acquired from Sigma. Magnesium oxide, sodium bicarbonate, ammonium peroxydisulfate and Hydrogen chloride, were purchased from Sinopharm Chemical. The products were recognized with melting point, FT-IR and 1HNMR analysis, the spectra were recorded in DMSO-d6 and CDCl3solvents and register on a Bruker DRX-400 spectrometer via tetramethylsilane as the inner reference. FT-IR spectra were attained via KBr pellets and record with Perkin-Elmer 781 spectrophotometer by an Impact 400 Nicolet FT-IR spectrophotometer. XRD analysis was recorded with (CuKa, radiation, ʎ = 0.154056 nm), with the speed of 2° min− 1 beginning 10° to 80° (2ϴ). The nanocatalyst size was determined with Zeiss Scanning Electron Microscope (SEM) worked at a 15 kV accelerating voltage. The surface areas (BET) were assignment via nitrogen adsorption-desorption in − 196 oC that recordby analyser Tristar 3020, Micromeritics
2.1. Synthesis of compact SiO2 spheres (sSiO2)
For a synthesis of sSiO2 from Stober procedure, 5 mL of tetraethylorthosilicate instantly was added to the mixture of deionized water (8mL), ethanol (70 mL) and ammonium aqueous solution (28%, 4 mL). Then the mixture was stirred for 1.5h in ambient temperature. At the end of the reaction, the white silica suspension was formed, then the product separated with a centrifuge and washed three times by deionized water and ethanol.
2.2. Synthesis of hollow SiO2
60 mg of the sSiO2 that prepared at prior step was dispersed in 15 ml deionized water via the ultrasonic waves for 20 min. Then 1.5 mL of the CTAB aqueous solution (1 mg, 1.5 ml) was added and stirred the mixture at ambient temperature for 1 h. Then 212 mg of Na2CO3 added to the reaction mixture and followed the reaction at 35ᴏC for 24 h. In the end, the product has separated and washed with deionized water and ethanol.
2.3. Synthesis of hollow SiO2 /MgO by Self-Assembly
50.0 mg of hollow SiO2 was dispersed in 5.0 mL toluene by ultrasonic water bath for 30 min. After that, 2.0 mL of the MgO NPs which dispersed in toluene was added to the mixture and sonicated for 1.5-2 h. Consequently, the product was washed by toluene and dried at 120 ᴏC overnight.
2.4. Preparation of hollow SiO2/MgO.
The product of previous steps was converted to hollow MgO/SiO2with hydrothermal removal of CTAB phase in 450ᴏC for 4h. As a result, the hollow MgO/SiO2were prepared.
2.5. General multicomponent procedure for synthesis of 1H-isochromene
1H-isochromene was synthesized from the three-component reaction. In this reaction, 1 mmol of cyclohexanone (1a-d) with 1 mmol of malononitrile were mixed in an ethanol solvent. Then 10 mg of hollow MgO/SiO2nanocatalyst was added to the mixture and stirred for 10–20 min at room temperature. After completed, the first step 1 mmol of benzaldehyde was added to the mixture and the reaction followed for 10–20 min at room temperature. In the end, the nanocatalyst was separated with simple filtration and added 5ml water to the mixture, for the formation of the pure product. The final product was characterized by melting points, IR and 1H NMR spectra.
3-amino-1-phenyl-5,6,7,8-tetrahydro-1H-isochromene-4-carbonitrile (4a); White solid; m.p.: 255–258°C; IR (KBr) v = 3419, 3338, 3252, 2934, 2211, 1647, 1602 1452, 1393, 1277, 1081, 712, 582 cm− 1, 1NMR (400 MHz, CDCl3) δ 7.57–7.45 (m, 5H), 6.04 (s. 1H), 4.85 (s, 2H, NH2), 3.11–3.08 (d, J = 12.5 Hz, 1H), 2.92–2.87 (m, 1H), 2.33–2.28 (m, 1H), 2.17–2.14 (m, 1H), 1.81–1.78 (m,1H), 1.68–1.71 (m, 1H), 1.57–1.48 (m, 1H), 1.01–0.92 (m, 1H).
3-amino-1-(2,4-dichlorophenyl)-5,6,7,8-tetrahydro-1H-isochromene-4-carbonitrile (4b); White solid; m.p.: 277–278°C; IR (KBr) v = 3444, 3354, 3202, 2941, 2213, 1623, 1591, 1474, 1337, 1268, 1107, 1052, 878, 563 cm− 1, 1H NMR (400 MHz, CDCl3) δ 7.67–7.53 (m, 2H), 7.44–7.42 (m, 1H), 6.12–6.08 (m, 1H), 4.88 (s, 2H, NH2), 3.99–3.97 (d, J = 8 Hz, 1H), 2.80–2.98 (t, J = 7 Hz,1H), 2.34–2.32 (m, 2H), 2.25–2.08 (m, 1H), 1.88–1.76 (m, 1H), 1.61–1.45 (m, 3H), 0.98 − 0.97 (m, 1H).
3-amino-1-(4-nitrophenyl)-5,6,7,8-tetrahydro-1H-isochromene-4-carbonitrile (4c); White solid; m.p.: 229–232°C; IR (KBr) v = 3419, 3348, 3287, 2937, 2207, 1645, 1524, 1449, 1349, 1133, 1042, 858, 557 cm− 1, 1H NMR (400 MHz, DMSO-d6) δ 8.55–8.27 (m, 2H), 8.23–8.19 (t, J = 7.9 Hz, 1H), 8.06–7.80 (m, 1H), 7.78–7.33 (m, 1H), 6.66 (s, 2H, NH2), 5.63 (s, 1H), 3.52 (d, J = 8.5 Hz 1H), 3.43 (s, 1H), 2.87–3.85 (d, J = 12.5 Hz, 1H), 2.15–2.11 (m, 1H), 1.71–1.61 (m, 1H), 1.45–1.42 (t, J = 7.5 Hz, 1H), 0.89 (m, 1H).
3-amino-1-(4-bromophenyl)-5,6,7,8-tetrahydro-1H-isochromene-4-carbonitrile (4d); White solid; m.p.: 260–263°C; IR (KBr) v = 3423, 3344, 3251, 2929, 2211, 1644, 1601, 1489, 1391, 1275, 1076, 835, 508 cm− 1, 1H NMR (400 MHz, CDCl3) δ 7.77–7.43 (m, 3H), 7.19 (d, J = 8.5 Hz, 1H), 6.11–6.06 (m, 1H). 4.86 (s, 2H, NH2), 3.10–3.06 (d, J = 8.6 Hz, 1H), 2.89–2.86 (d, J = 8.5 Hz, 1H), 2.34–2.28 (m, 1H), 2.27–2.04 (m, 1H), 1.84 (m, 2H), 1.74–1.40 (m, 2H), 1.08–0.74 (m, 1H).
3-amino-1-(4-chlorophenyl)-5,6,7,8-tetrahydro-1H-isochromene-4-carbonitrile (4e); White solid; m.p.: 274–277°C; IR (KBr) v = 3421, 3343, 3252, 2944, 2212, 1645, 1602, 1492, 1388, 1212, 1095, 805, 514 cm− 1, 1HNMR (400 MHz, DMSO-d6) δ 7.58 (d, J = 8.5 Hz, 1H), 7.52 (d, J = 7.8 Hz, 1H), 7.46 (d, J = 7.2 Hz, 2H), 5.75 (S, 1H), 3.65 (s, 2H, NH2), 2.77, 2.48 (m, 1H), 2.15–2.18 (m, 3H), 1.66 (s,1H), 1.42–1.51 (m, 2H), 0.79–0.88 (m, 1H)
3-amino-1-(4-(dimethyl amino) phenyl)-5,6,7,8-tetrahydro-1H-isochromene-4-carbonitrile; White solid (4f); m.p.: 248–250°C; IR (KBr) v = 3448, 3356, 3207, 2917, 2212, 1618, 1526, 1447, 1358, 1272, 1115, 948, 525 cm− 1. 1H NMR (400 MHz, CDCl3) δ 7.52–7.35 (m, 1H), 7.15 (d, J = 7.5 Hz, 1H), 6.89–6.61 (m, 2H), 6.06–6.02 (m, 1H), 4.88 (s, 2H, NH2), 3.01 (s, 6H), 2.92–2.76 (m, 1H), 2.34–2.24 (m, 1H), 2.15 (m, 1H), 1.81–1.75 (m, 2H), 1.64–1.41 (m, 2H), 1.04–0.85 (m, 1H).
3-amino-1-(3-nitrophenyl)-5,6,7,8-tetrahydro-1H-isochromene-4-carbonitrile (4g); White solid; m.p.: 248–250°C; IR (KBr) v = 3441, 3357, 3248, 2947, 2208, 1639, 1531, 1442, 1352, 907, 829, 547 cm− 1, 1H NMR (400 MHz, CDCl3) δ 7.48 (d, J = 8.3 Hz, 2H), 7.36–7.22 (m, 2H), 6.07–6.02 (m, 1H), 4.88 (s, 2H, NH2), 3.08–3.05 (d, J = 8.5 Hz, 1H), 2.94–2.78 (m, 1H), 2.18–2.16 (m, 1H), 1.84–1.82 (m, 1H), 1.74–1.71 (m, 1H), 1.66–1.48 (m, 3H), 1.03–0.88 (m, 1H).
3-amino-1-(4-fluorophenyl)-5,6,7,8-tetrahydro-1H-isochromene-4-carbonitrile (4h); White solid; m.p.: 262–265°C; IR (KBr) v = 3422, 3337, 3251, 2949, 2213, 1649, 1598, 1455, 1391, 1273, 828, 516 cm− 1, 1H NMR (400 MHz, DMSO-d6) δ 7.65–7.28 (m, 4H, 2H, NH2), 5.72 (s, 1H), 3.63–3.61 (d, J = 12.2 Hz, 1H), 2.78–2.78 (d, J = 8.5 Hz, 1H), 2.21–2.19 (d, J = 8.9 Hz, 1H), 2.07 (s, 1H), 1.66 (s, 1H), 1.59–1.37 (m, 2H), 0.85 (q, J = 7.5, 1H).
3-amino-1,7-diphenyl-5,6,7,8-tetrahydro-1H-isochromene-4-carbonitrile (4i); White solid; m.p.: 250–252°C; IR (KBr) v = 3423, 3328, 3225, 2915, 2213, 1645, 1598, 1495, 1391, 1264, 755, 568 cm− 1, 1H NMR (400 MHz, DMSO-d6) δ 7.63–7.62 (d, J = 7.8 Hz, 1H), 7.45 (s, 2H, NH2), 7.42 (s, 4H), 7.22–7.18 (t, J = 7.4 Hz, 2H), 7.15–7.11 (m, 3H), 5.81 (s, 1H), 3.64–3.61 (d, J = 8.4 Hz, 1H), 3.13–3.08 (m, 1H), 2.28–2.91 (m, 1H), 2.45–2.41 (m, 1H), 2.23–2.16 (m, 1H), 1.52–1.49 (d, J = 7.8 Hz, 1H), 1.24–118 (q, J = 7.6 Hz, 1H).
3-amino-7-methyl-1-phenyl-5,6,7,8-tetrahydro-1H-isochromene-4-carbonitrile (4J); White solid; m.p.: 218–220°C; IR (KBr) v = 3425, 3332, 3235, 2957, 2215, 1652, 1602, 1453, 1392, 1267, 711, 597 cm− 1, 1H NMR (400 MHz, DMSO-d6) δ 7.68–7.38 (m, 6H), 7.37 (s, 2H, NH2), 5.98 (s, 1H), 3.58 (d, J = 8.6 Hz, 1H), 2. 91-2.88 (d, J = 7.4 Hz, 1H), 2.32–2.24 (m, 1H), 1.67–1.67 (d, J = 8.2 Hz, 1H), 1.37–1.34 (m 1H), 0.93 − 0.88 (d, J = 7.2 Hz, 1H), 0.81 − 0.79 (d, J = 5.4 Hz, 3H), 0.66 − 0.63 (q, J = 8.7 Hz, 1H).
3-amino-1-(4-bromophenyl)-7-methyl-5,6,7,8-tetrahydro-1H-isochromene-4-carbonitrile (4k); White solid; m.p.: 246–248°C; IR (KBr) v = 3424, 3347, 3252, 2952, 2213, 1646, 1601, 1488, 1391, 1268, 827, 508 cm− 1, 1H NMR (400 MHz, DMSO-d6) δ 7.81–7.47 (m, 4H), 7.38 (s, 2H, NH2), 5.68 (s, 1H), 3.68–3.63 (d, J = 7.7 Hz, 1H), 2.87 (s, 1H), 2.27–2.22 (d, J = 8.8 Hz, 1H), 1.69 (s, 1H), 1.36–1.32 (d, J = 8.5 Hz, 1H), 0.81 (s, 3H), 0.74 − 0.54 (m, 1H).
3-amino-1-phenyl-7-propyl-5,6,7,8-tetrahydro-1H-isochromene-4-carbonitrile (4l); White solid; m.p.: 194–198°C; IR (KBr) v =, 3428, 3343, 3255, 2952, 2211, 1648, 1597, 1456, 1393, 1274, 708, 579 cm− 1, 1H NMR (400 MHz, DMSO-d6) δ 7.61–7.42 (m, 4H), 7.39 (s, 2H, NH2), 5.71 (s, 1H), 3.58–3.51 (m, 1H), 2.88–2.85 (d, J = 8.9 Hz, 1H), 2.32–2.26 (d, J = 7.6 Hz, 1H), 1.74–1.55 (m, 2H), 1.49–1.34 (m, 1H), 1.28–1.13 (m, 2H), 1.08–1.06 (q, J = 8.5, 2H), 0.79 − 0.76 (t, J = 7.4 Hz, 3H), 0.62 (q, J = 8.7 Hz, 1H).
3.1 Preparation and chracterization of catalyst
In this research, the hollow MgO/SiO2 nanoparticles were prepared in three-steps that show in Scheme 1(Fang et al., 2011; Wang and Zeng, 2009). At the first step, compact SiO2 sphere (sSiO) was prepared and decreased density and increased of the active area space via converted to hollow SiO2. The hollow SiO2 was functionalized with MgO nanoparticles then the nanostructure calcinated and converted to hollow MgO/SiO2 nanocatalyst.
After preparation, the nanocatalyst was characterized by various analysis such as FT-IR, XRD, BET, SEM and TEM. For the determined the crystal structure of nanoparticles, the X .ray diffraction patterns of nanostructure were investigated with the XRD spectrum (Fig 1). In the graph (a), the structure of hollow SiO2 considered by X-ray diffraction (XRD) (tetragonal, JCPDS card N 34-0425). The spectra were showed a wide peak in 20-30 that assignment an amorphous structure of SiO2 (Fig 2a). The graph (b) that due to hollow SiO2@MgO furthermore the wide peak in 20-30, it has two peaks in 43, 62 that due to MgO (Fig 2b).
The hollow catalyst was considered by FT.IR spectrum (Fig 2). Fig 2a described the hollow SiO2, the peak of around 1066 cm-1 determined stretching vibration from Si-O bonding. The peaks of 2924, 2853 cm-1 were showed C-H bonding from the CTAB and the peak of 3410 cm-1 due to the stretching vibration of the O-H bond. The spectrum 2b was related to hollow MgO/SiO2 and displayed Mg-O bonding in 3697 cm-1.
The hollow structure of synthetic compound has been demonstrated. The N2 adsorption-desorption isotherms and hysteresis loop, provide better confirmation of the mesoporous structure. The Brunauer–Emmett–Teller (BET) was demonstrate 619 m2 g−1surface area and the mean pore diameter is 2.11 nm. (Fig 3).
Hollow spheres morphology was achieved after calcination and considered by FE-SEM. The SEM images was displayed the formation of hollow MgO/SiO2 nanoparticles with smooth and regular morphology (Fig 4). The average crystal size of nanocatalyst was170 nm.
3.2. Investigation of catalytic activity
1H-isochromene was synthesized from cyclic ketones, malononitrile and benzaldehyde in varies conditions. The model reaction was investigated with different catalysts, the amount of catalyst and solvents moreover the result displayed in Table 1.
Table 1. Several condition in multicomponent reaction for synthesis of 1H-isochromene a
a Reaction conditions: cyclohexanone (1 mmol), malononitrile (1 mmol), benzaldehyde (1 mmol), room temperature
b Isolated yield
After optimization of the reaction conditions with different catalysts and solvents, the situation of a reaction was determined (Scheme 2). The hollow MgO/SiO2 with strong base properties selected as the catalyst for the synthesis of 1H-isochromene from cyclohexanone (1 mmol), malononitrile (1 mmol) and benzaldehyde (1mmol) in the ethanol solvent. Therefore, the different derivatives of 1H-isochromene (Table 2) were synthesized at room temperature in 20-30 min.
Table 2. The reaction of cyclohexanone 1a-d, malononitrile and benzaldehyde 3a-h for synthesis of 1H-isochromenes 4a-la
a Reaction conditions: cyclohexanone (1 mmol), malononitrile (1 mmol), benzaldehyde (1 mmol), ethanol solvent, room temperature
b Isolated yield
3.3. Proposed reaction mechanism
Synthesis of 1H-isochromene was done in the two-step, the first step, including the mixed of cyclohexanone with malononitrile in ethanol under the base condition. The reaction was followed by vinylogous Michael addition for the synthesis of vinylmalononitriles. In the second step, benzaldehyde was added to the mixture and during the aldol reaction vinyl malononitrile reacted with benzaldehyde. The vinyl malononitrile was adsorbed hydrogen, and the processes followed by cycle creation of C–C and C–O bonds. In the end, 1H-isochromene was synthesized with loss of the hydrogen via the base catalyst (Scheme 3).
3.4. Reusability
At the end of reaction, the hollow catalyst separated with simple filtration and washed with acetone and ethyl acetate solventThe heterogeneuse nanostructure can catalyze the reaction in six consecutive runs without loss of activity.(Fig 5).
In this research, it was prepared a novel heterogeneous hollow catalyst for the synthesis of 1H-isochromene from cyclohexanone, malononitrile, and benzaldehyde. The reaction was followed in the ethanol solvent at room temperature and hollow MgO/SiO2 nanostructure used as the base catalyst. The product was synthesized with excellent yield and short reaction time, the catalyst easy recovered and reused for several runs of the reactions.
Authors' contributions: Article publication approve by co-authors, as well as by the responsible authorities at the institute where the work has been carried out.
Ethics approval and consent to participate: Not applicable.
Consent for publication: In accordance to the copyright transfer or open access rules.
Competing interests: Not applicable.
Funding: See above Acknowledgements.
Compliance with Ethical Standards: Not applicable.
Acknowledgements: The authors are grateful to University of Kashan for supporting this work by Grant No. 159148/96.
Availability of data and materials: Electronic supplementary material contains 1H NMR, 13C NMR, FT-IR and microscopy data.
Supplementary data: Supplementary material related to this article can be found in the online version at doi//:
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- MohamadiCovLett.pdf
- MohamadiGA.pdf
- MohamadiHRes.pdf
- MohamadiSCONLett.doc
- MohamadiSI.pdf
- scheme1.jpg
Preparation of hollow SiO2/MgO.
- scheme2.jpg
Synthesis of 1H-isochoromenederivatives from cyclohexanones 1a-d, malononitrile and benzaldehydes 3a-h at room temperature
- scheme3.jpg
Proposed reaction mechanism for the Synthesis of 1H-isochoromene
