M-Type SrFe₁₂O₁₉ Ferrite: An Efficient Catalyst for the Synthesis of Amino Alcohols under Solvent-Free Conditions

Abstract

<jats:p>Magnetically separable strontium hexaferrite SrFe<jats:sub>12</jats:sub>O<jats:sub>19</jats:sub> was prepared using the chemical coprecipitation method, and the nanostructured material was characterized by X-ray diffraction, scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), and BET analysis. The SEM images showed the homogeneity of the chemical composition of SrFe<jats:sub>12</jats:sub>O<jats:sub>19</jats:sub> and uniform distribution of size and morphology. The pore size of the nanomaterial and its specific area were determined by BET measurements. Strontium hexaferrite SrFe<jats:sub>12</jats:sub>O<jats:sub>19</jats:sub> exhibited a strong magnetic field, which is highly suitable in the heterogeneous catalysis as it can be efficiently separated from the reaction. The magnetic nanocatalyst showed high activity and environmentally benign heterogeneous catalysts for the epoxide ring-opening with amines affording <jats:italic>β</jats:italic>-amino alcohols under solvent-free conditions. When unsymmetrical epoxides were treated in the presence of aromatics amines, the regioselectivity was influenced by the electronic and steric factors. Total regioselectivity was observed for the reactions performed with aliphatic amines. The magnetically SrFe<jats:sub>12</jats:sub>O<jats:sub>19</jats:sub> nanocatalyst showed excellent recyclability with continuously good catalytic activities after four cycles.</jats:p>

Synergistic effect of GO/SrFe12O19 as magnetic hybrid nanocatalyst for regioselective ring-opening of epoxides with amines under eco-friendly conditions

“…The reaction was faster (2 h) compared to our previous work (17 h). 58 The regioselectivity of the catalytic reaction is influenced by the electronic and steric factors associated with both studied substrates epoxide and amines. 84 In presence of aromatic amines, the opening reaction is mainly oriented towards amino alcohols 5 through the nucleophilic attack at the benzylic carbon atom of the epoxide ring (entries 1–4).…”

“…Both prepared nanocomposites present crystalline SrFe 12 O 19 in a hexagonal structure with a space group 194/ P 63 mmc , in good agreement with the standard JCPDF file (33-1340). 58,70 According to the Scherrer equation, 71 the crystallite size of the M-type hexagonal SrFe 12 O 19 phase in the prepared SrFe 12 O 19 , hybrid GO/SrFe 12 O 19 , and rGO/SrFe 12 O 19 were to be 25.098, 25.663, and 20.331 nm, respectively.…”

“…The catalytic performance of the prepared nanomaterials, SrFe 12 O 19 and hybrid GO/SrFe 12 O 19 , was rst evaluated in freesolvent conditions (Table 1). 58 As shown in Table 1, the epoxide was converted to the resulting ring-opening products in good yields (entries 1 and 2). However, the presence of GO/SrFe and increase the active surface area of the hybrid nanomaterial compared to pure SrFe 12 O 19 , providing a good dispersion and distribution of SF.…”

“…Recently, we have reported the non-adaptability of water as a solvent for the ring-opening of epoxide while using SrFe 12 O 19 as a catalyst. 58 In contrast, the ZP value of hybrid GO/ SrFe 12 O 19 indicates its high stability in water, conrming the good choice of GO sheets for the dispersion of SrFe 12 O 19 nanoparticles, which will be of great advantage for a greener catalytic application. On the other hand, the size peaks and zaverage conrm the nanoscale size of hexaferrite nanoparticles and the microscale of GO sheets (conrmed by the increase in size and z-average of GO/SrFe 12 O 19 sample).…”

“…Recently, we have reported M-type hexaferrite SrFe 12 O 19 (SF) as an efficient heterogeneous bulk catalyst for amino alcohol synthesis. 58 To improve the catalytic activity of SrFe 12 O 19 , we have herein selected graphene oxide as dispersion of the catalytic active sites of SF due to its intriguing characteristics including high surface area, numerous oxygen-containing functional groups, high hydrophilicity, and good dispersion in water.…”