254
M. Camats et al.
Maleki and coworkers synthesized Fe 3 O 4 nanoparticles stabilized by the biopolymer chitosan coming from chitin (polymer of N-acetylglucosamine) to be applied in
three-component reactions yielding benzodiazepines [86] and benzimidazoloquinazolinones [84] (Scheme 8.3), which present biological and pharmacological activities
[25, 58]. For both types of reactions, the catalyst was recycled up to four times preserving its catalytic performance, being ethanol the most appropriate solvent for these
catalytic reactions. Authors proposed a similar pathway for both transformations.
In Fig. 8.2, the postulated mechanism for the synthesis of benzimidazolo[2,3b]quinazolinones is illustrated. The reaction most likely starts by a Knoevenagel
NH 2
NH 2
O
O
+
+
Ar
O
[Fe 3 O 4 /chitosan]
EtOH
r.t. 25-60 min
HN
NH
Ar
O
[Fe 3 O 4 /chitosan]
EtOH
40 °C, 2-4 h
N
N
O
X
R
O
O
+
R
O
N
X
+
NH 2
Isolated Yield: 85-94%
Isolated Yield: 82-95%
Scheme 8.3 Three-component reactions catalyzed by Fe 3 O 4 nanoparticles stabilized by chitosan
[84, 86]
Fig. 8.2 Proposed mechanism for Fe-based catalyzed synthesis of benzimidazolo[2,3b]quinazolinones. Reprinted from [84] with permission from Elsevier 2015, license no.
4639401066332
M. Camats et al.
Maleki and coworkers synthesized Fe 3 O 4 nanoparticles stabilized by the biopolymer chitosan coming from chitin (polymer of N-acetylglucosamine) to be applied in
three-component reactions yielding benzodiazepines [86] and benzimidazoloquinazolinones [84] (Scheme 8.3), which present biological and pharmacological activities
[25, 58]. For both types of reactions, the catalyst was recycled up to four times preserving its catalytic performance, being ethanol the most appropriate solvent for these
catalytic reactions. Authors proposed a similar pathway for both transformations.
In Fig. 8.2, the postulated mechanism for the synthesis of benzimidazolo[2,3b]quinazolinones is illustrated. The reaction most likely starts by a Knoevenagel
NH 2
NH 2
O
O
+
+
Ar
O
[Fe 3 O 4 /chitosan]
EtOH
r.t. 25-60 min
HN
NH
Ar
O
[Fe 3 O 4 /chitosan]
EtOH
40 °C, 2-4 h
N
N
O
X
R
O
O
+
R
O
N
X
+
NH 2
Isolated Yield: 85-94%
Isolated Yield: 82-95%
Scheme 8.3 Three-component reactions catalyzed by Fe 3 O 4 nanoparticles stabilized by chitosan
[84, 86]
Fig. 8.2 Proposed mechanism for Fe-based catalyzed synthesis of benzimidazolo[2,3b]quinazolinones. Reprinted from [84] with permission from Elsevier 2015, license no.
4639401066332