Magnetic Nanoparticles: Green and Environment Friendly …
489
condensation reaction of 2-aminoazine, alkyl-4-formyl-1-substituted phenyl-1Hpyrazole-3-carboxylate and isocyanides in ethanol (Swami et al. 2016) (Scheme 23).
Similarly, a carbon nanotube supported CoFe 2 O 4 /CNT-Cu magnetic nanoparticles were used in 3-nitro-2-arylimidazo [1,2-a]pyridines synthesis. CoFe 2 O 4 /CNTCu Nps offer a reusable catalytic activity for 3-nitro-2-arylimidazo [1,2-a]pyridines
synthesis via a three-component reaction of 2-aminopyridines, aldehydes, and
nitromethane in PEG 400 under aerobic conditions as shown in Scheme 24 (Zhang
2016).
Another example of ferrite magnetic nanoparticle in organic transformation is
CuFe 2 O 4 Nps, these Nps are magnetically recoverable and reusable catalyst for the
synthesis of 5-substituted 1H-tetrazoles. A variety of aryl nitriles undergoes 2 + 3
cycloaddition in the presence of CuFe 2 O 4 magnetic Nps as shown in Scheme 25,
CuFe 2 O 4 provides mild reaction condition, excellent yield, and reusability around
five-times without losing catalytic efficiency (Sreedhar et al. 2011).
N
N
HN
R 4
NC
R 4
N
N
COOEt
OHC
N
N
COOEt
R 5
R 6
CuFe 2 O 4 @SiO 2 -SO 3 H
Nps (10 mol%)
N
NH 2
R 3
R 2
R 1
R 5
R 6
R 3
R 2
R 1
Ethanol
Reaction time: 10 min.
Yield: 90-96%
Scheme 23 Synthesis of 2-pyrazole-3-amino-imidazo[1,2-a]pyridine derivative in presence of
CuFe 2 O 4 @SiO 2 -SO 3 H magnetic nanoparticles
N
NH 2
N
N
R 2
NO 2
CH 3 NO 2
R 1
+
+
R 1
CoFe 2 O 4 @CNT-Cu
PEG 400, air, 80
o
C
R 2 -CHO
Scheme 24 Synthesis of 3-nitro-2-arylimidazo [1,2-a]pyridines catalyzed by CoFe 2 O 4 /CNT-Cu
Nps
CN
R
R
N
N
N
HN
NaN 3
+
40 mol% CuFe 2 O 4
DMF, 120
o
C
Scheme 25 Synthesis of 5-substituted 1H-tetrazoles using CuFe 2 O 4 Nps
489
condensation reaction of 2-aminoazine, alkyl-4-formyl-1-substituted phenyl-1Hpyrazole-3-carboxylate and isocyanides in ethanol (Swami et al. 2016) (Scheme 23).
Similarly, a carbon nanotube supported CoFe 2 O 4 /CNT-Cu magnetic nanoparticles were used in 3-nitro-2-arylimidazo [1,2-a]pyridines synthesis. CoFe 2 O 4 /CNTCu Nps offer a reusable catalytic activity for 3-nitro-2-arylimidazo [1,2-a]pyridines
synthesis via a three-component reaction of 2-aminopyridines, aldehydes, and
nitromethane in PEG 400 under aerobic conditions as shown in Scheme 24 (Zhang
2016).
Another example of ferrite magnetic nanoparticle in organic transformation is
CuFe 2 O 4 Nps, these Nps are magnetically recoverable and reusable catalyst for the
synthesis of 5-substituted 1H-tetrazoles. A variety of aryl nitriles undergoes 2 + 3
cycloaddition in the presence of CuFe 2 O 4 magnetic Nps as shown in Scheme 25,
CuFe 2 O 4 provides mild reaction condition, excellent yield, and reusability around
five-times without losing catalytic efficiency (Sreedhar et al. 2011).
N
N
HN
R 4
NC
R 4
N
N
COOEt
OHC
N
N
COOEt
R 5
R 6
CuFe 2 O 4 @SiO 2 -SO 3 H
Nps (10 mol%)
N
NH 2
R 3
R 2
R 1
R 5
R 6
R 3
R 2
R 1
Ethanol
Reaction time: 10 min.
Yield: 90-96%
Scheme 23 Synthesis of 2-pyrazole-3-amino-imidazo[1,2-a]pyridine derivative in presence of
CuFe 2 O 4 @SiO 2 -SO 3 H magnetic nanoparticles
N
NH 2
N
N
R 2
NO 2
CH 3 NO 2
R 1
+
+
R 1
CoFe 2 O 4 @CNT-Cu
PEG 400, air, 80
o
C
R 2 -CHO
Scheme 24 Synthesis of 3-nitro-2-arylimidazo [1,2-a]pyridines catalyzed by CoFe 2 O 4 /CNT-Cu
Nps
CN
R
R
N
N
N
HN
NaN 3
+
40 mol% CuFe 2 O 4
DMF, 120
o
C
Scheme 25 Synthesis of 5-substituted 1H-tetrazoles using CuFe 2 O 4 Nps