Magnetic Nanoparticles: Green and Environment Friendly …
481
heterogeneous catalysts for the synthesis of coumarin derivatives by one-pot condensation of various phenols with ethyl acetoacetate under solvent and halogen-free conditions. A proposed mechanism for 7-hydroxy-4-methyl-2H-chromen-2-one synthesis from the reaction of ethyl acetoacetate with resorcinol using γ-Fe 2 O 3 @HAp-Ag
NPs was depicted in Scheme 7 (Abbasi 2017).
Another case of Fe 3 O 4 nanoparticles is functionalized with calix[4]arene proline
moiety (Calix-Pro-MN) which is used as recyclable organocatalyst in asymmetric
aldol condensation of cyclohexanone and aromatic aldehydes as depicted in Scheme 8
(Akceylan 2015).
Another magnetic nanoparticles Fe 3 O 4 @SiO 2 GMSI-VBI were prepared via three
step synthetic protocol as depicted in Scheme 9. In the first step Fe 3 O 4 Nps were
synthesized via chemical co-precipitation of FeCl 2 and FeCl 3 and then these Nps
were coated with TEOS via Stober method. In second step, commercially available GMSI was reacted with VBI in dry THF to yield GMSI-VBI ligand. Finally
Fe 3 O 4 @SiO 2 GMSI-VBI MNPs obtain by refluxing suspended mixture of GMSIVBI and Fe 3 O 4 @SiO 2 in dry THF. The synthesized Fe 3 O 4 @SiO 2 GMSI-VBI MNps
has prominent advantage compare to other catalysts used for 2,3-dihydroquinazolin4(1H)-ones synthesis like shorter reaction time, low catalyst loading, and readily
recovered using external magnet and reused without any treatment with efficient
catalytic activity (Azizi et al. 2017).
A class of magnetic silver nanoparticles were supported over Al 2 O 3 cores and
Fe 2 O 3 shells were prepared successfully as depicted in Scheme 10. Synthesized AgAl 2 O 3 @Fe 2 O 3 magnetic nanoparticles used as a catalyst in synthesis of 1,2,3-triazole
and acylation of benzyl alcohol. Mesoporous Ag-Al 2 O 3 @Fe 2 O 3 shows high catalytic
efficiency for synthesis of 1,4-disubstituted 1,2,3-triazole in aqueous medium and
EtO
O
Me
O
O
O
Me
HO
O
HO
O
HO
O
Me
OEt
O
H
H
H
HO
Me
O
OEt
O
OH
O
HO
Me
O
O
EtO
O
Me
O
+
-H 2 O
-EtOH
Scheme 7 Proposed mechanism for one-pot synthesis of 7-hydroxy-4-methyl-2H-chromen-2-one
promoted by γ-Fe 2 O 3 @HAp-Ag NPs
481
heterogeneous catalysts for the synthesis of coumarin derivatives by one-pot condensation of various phenols with ethyl acetoacetate under solvent and halogen-free conditions. A proposed mechanism for 7-hydroxy-4-methyl-2H-chromen-2-one synthesis from the reaction of ethyl acetoacetate with resorcinol using γ-Fe 2 O 3 @HAp-Ag
NPs was depicted in Scheme 7 (Abbasi 2017).
Another case of Fe 3 O 4 nanoparticles is functionalized with calix[4]arene proline
moiety (Calix-Pro-MN) which is used as recyclable organocatalyst in asymmetric
aldol condensation of cyclohexanone and aromatic aldehydes as depicted in Scheme 8
(Akceylan 2015).
Another magnetic nanoparticles Fe 3 O 4 @SiO 2 GMSI-VBI were prepared via three
step synthetic protocol as depicted in Scheme 9. In the first step Fe 3 O 4 Nps were
synthesized via chemical co-precipitation of FeCl 2 and FeCl 3 and then these Nps
were coated with TEOS via Stober method. In second step, commercially available GMSI was reacted with VBI in dry THF to yield GMSI-VBI ligand. Finally
Fe 3 O 4 @SiO 2 GMSI-VBI MNPs obtain by refluxing suspended mixture of GMSIVBI and Fe 3 O 4 @SiO 2 in dry THF. The synthesized Fe 3 O 4 @SiO 2 GMSI-VBI MNps
has prominent advantage compare to other catalysts used for 2,3-dihydroquinazolin4(1H)-ones synthesis like shorter reaction time, low catalyst loading, and readily
recovered using external magnet and reused without any treatment with efficient
catalytic activity (Azizi et al. 2017).
A class of magnetic silver nanoparticles were supported over Al 2 O 3 cores and
Fe 2 O 3 shells were prepared successfully as depicted in Scheme 10. Synthesized AgAl 2 O 3 @Fe 2 O 3 magnetic nanoparticles used as a catalyst in synthesis of 1,2,3-triazole
and acylation of benzyl alcohol. Mesoporous Ag-Al 2 O 3 @Fe 2 O 3 shows high catalytic
efficiency for synthesis of 1,4-disubstituted 1,2,3-triazole in aqueous medium and
EtO
O
Me
O
O
O
Me
HO
O
HO
O
HO
O
Me
OEt
O
H
H
H
HO
Me
O
OEt
O
OH
O
HO
Me
O
O
EtO
O
Me
O
+
-H 2 O
-EtOH
Scheme 7 Proposed mechanism for one-pot synthesis of 7-hydroxy-4-methyl-2H-chromen-2-one
promoted by γ-Fe 2 O 3 @HAp-Ag NPs