Cu(II) immobilized on mesoporous organosilica as an efficient and reusable nanocatalyst for one‐pot Biginelli reaction under solvent‐free conditions

Abstract

Cu(II) immobilized on mesoporous organosilica nanoparticles (Cu2+@MSNs‐(CO2−)2) has been synthesized, as a inorganic–organic nanohybrid catalyst, through a post‐grafting approach. Its characterization is carried out by Fourier transform infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Energy dispersive X‐ray (EDX), Thermogravimetric/differential thermal analyses (TGA‐DTA), and Nitrogen adsorption–desorption analysis. Cu2+@MSNs‐(CO2−)2 exhibits high catalytic activity in the Biginelli reaction for the synthesis of a diverse range of 3, 4‐dihydropyrimidin‐2(1H)‐ones, under mild conditions. The anchored Cu(II) could not leach out from the surface of the mesoporous catalyst during the reaction and it has been reused several times without appreciable loss in its catalytic activity.

Copper supported on acid-activated vermiculite as an efficient and recyclable catalyst for the Biginelli reaction: a green approach

“…Finally, the Cu content in AAVrm-Cu2 was 6.18%, slightly greater than that of Cu nanoparticles supported over hydrotalcite (Mitsudome et al ., 2008) and of Cu supported over chitosan (Baig & Varma, 2013). However, it is comparable to the Cu content reported for other heterogeneous catalysts (Nasresfahani & Kassaee, 2018; Yao et al ., 2018).…”

“…A reasonable mechanism is proposed on the basis of this work (Fig. 10) and the available literature (Nasresfahani & Kassaee, 2018; Yao et al ., 2018; Kappe, 2000). The catalyst AAVrm-Cu2 activates the carbonyl group in the aryl aldehyde by coordination to O atoms in order to favor the nucleophilic attack of urea.…”

“…AAVrm was mainly composed of SiO 2 and had CaO, TiO 2 , Cr 2 O 3 , MnO as minor components, suggesting that the acid treatment created cavities in the structure of Vrm due to the leaching of almost all the components of the original vermiculite. Finally, the copper content in AAVrm-Cu2 was estimated to be 6.18%, this value is slightly higher than the copper content of copper nanoparticles supported over hydrotalcite (Mitsudome et al, 2008) and copper supported over chitosan (Baig & Varma, 2013) and it is comparable to those reported for other heterogeneous catalysts containing copper (Nasresfahani & Kassaee, 2018;Yao et al, 2018). The FTIR spectra of Vrm (Figure 4) showed absorption bands at 3350 cm -1 and 1645 cm -1 assigned to water molecules in the interlayer of Vrm (Madejová et al, 2017), a small shoulder at 3600 cm -1 assigned to superficial OH groups (Madejová et al, 2017), the strong band at 971 cm -1 was assigned to Si-O-Al stretch and is shifted in comparison to other clay minerals where this band appears at a wavenumber higher than 1000 cm -1 , this suggests that the octahedral sheets of vermiculite are trioctahedral and composed of a combination of 3 divalent cations such as Mg 2+ and Fe 2+ with no substitution of Al 3+ in the divalent cation positions (Madejová et al, 2017).…”

“…Melting point and spectroscopic data of compounds 4a-4d (Table S1) is in good agreement with literature results (Yao et al, 2018) In comparison to reported catalysts (Table 7), the effectiveness of AAVrm-Cu2 is slightly lower compared to expensive catalysts containing holmium or ytterbium but is comparable and even enhanced to most copper catalysts and above these catalysts, excels due to the fact that does not need strong mineral acids or inert atmosphere to maintain the catalytic activity and the recyclability in the reaction. (Song, et al, 2008) Cu(NO 3 ) 2 •2H 2 O Δ 80°C 2 91 (Wang et al, 2009) Cu(NH 2 SO 3 ) 2 Δ 100°C 6 79 Cu 2+ @MSNs-(CO 2 − ) 2 ) Δ 100°C 1 95 (Nasresfahani & Kassaee, 2018) A reasonable mechanism is proposed on the basis of this work ( Figure 10) and available literature (Kappe, 2000;Nasresfahani & Kassaee, 2018;Yao et al, 2018 the open chain ureide III than undergoes a cyclization to form IV followed by the acid catalyzed elimination of water by Cu 2+ atom in AAVrm-Cu2 in order to form the target dihydropyrimidinone.…”

Asparagine-EDTA MNPs: A Highly Efficient And Recyclable Magnetic Multifunctional Core-Shell Nanocatalyst For Green Synthesis of Biologically-Active 3,4-Dihydropyrimidin-2(1H)-One Compounds

“…Among the various types of nitrogen-containing heterocycles, derivatives of 3,4-dihydropyrimidin-2(1H)one, as biologically-active compounds, have found versatile applications such as anti-bacterial, anti-in ammatory, antihypertensive agents, calcium channel blockers, antitumor compounds [41][42][43][44][45][46][47] . A simple and general protocol for access to 3,4-dihydropyrimidin-2(1H)-ones involves a three-component one-pot Biginelli cyclocondensation of ethyl acetoacetate, urea and various aldehydes accelerated by different types of catalytic systems such as polymer-supported catalysts 48 , ionic liquids 49,50 , ionic liquid/silica sulfuric acid 51 , metal−organic framework (MOF) 52,53 , montmorillonite clay 54 , magnetic nanoparticles 55 , Lewis acidic zirconium (IV)-salophen per uorooctanesulfonate or sulfated polyborate 56,57 , nanocrystalline CdS thin lm 46 , graphene oxide 58,59 and mesoporous materials 60,61 as well as environmental friendly energy inputs such as ultrasound 62 or microwave irradiation 63 . Most of the reported methods in this regard have the role of heterogeneous catalysts and high value.…”