J IRAN CHEM SOC
NaBH4/Cu NPs system (2:0.15), was carried out perfectly
within 8–10 min to afford the corresponding heteroam-
ines in 90–92 % yields (entries 17, 18). Reducing capabil-
ity of NaBH4/Cu NPs system toward aliphatic nitro com-
pounds was also studied by the reduction of 1-nitrohexane
and 2-nitroheptane at the optimized reaction conditions.
The results showed that as aromatic and heterocyclic nitro
compounds, this protocol was also efficient, and the corre-
sponding aliphatic amines were obtained efficiently within
5–7 min (entries 19, 20).
gelatinous precipitate together of gas evolution was pre-
pared. The reaction was completed within 2 min. The
resulted precipitate was filtered and washed with distilled
water (3 × 20 mL) and acetone (20 mL) followed by dry-
ing in vacuo to afford Cu NPs in 89 % yield (size of NPs:
42–47 nm).
A typical procedure for reduction of nitrobenzene
to aniline with NaBH4/Cu NPs system
In a round-bottom flask (10 mL) equipped with a mag-
netic stirrer, a mixture of nitrobenzene (0.123 g, 1 mmol)
and H2O (2 mL) was prepared. Cu NPs (0.0095 g,
15 mmol %) was then added, and the mixture was stirred
for 3 min at 80 °C. Afterward, NaBH4 (0.076 g, 2 mmol)
was added portion wisely (two portions) with the interval
of 2 min, and the resulting mixture was continued to stir-
ring at 80 °C. TLC monitored the progress of the reaction
(n-hexane/EtOAc: 5/2). After completion of the reaction,
Cu NPs was separated by filtration, and the mixture was
extracted with EtOAc (2 × 5 mL). The organic layer was
then dried over anhydrous Na2SO4. Evaporation of the sol-
vent affords the pure liquid aniline in 91 % yield (0.085 g,
Conclusions
In summary, we have shown that NaBH4 in the presence
of Cu NPs efficiently reduces verities of nitro compounds
to the corresponding amines. Reduction reactions were
carried out in water with the molar equivalents of 2–3 for
NaBH4 and 0.15–0.2 for Cu NPs under oil bath condi-
tions (80 °C). The product amines were obtained in high to
excellent yields within 4–15 min. High yields, easy work-
up procedure, the cheapness and availability of the rea-
gents, ability of aromatic, heterocyclic and aliphatic nitro
compounds toward reduction, and the benefits of using
water as a green solvent are the significant advantages that
make this protocol a synthetically useful addition to the
present methodologies.
Acknowledgments The financial support of this work was grate-
fully acknowledged by the Research Council of Urmia University.
Experimental
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solution,
a yellow–brown and then a brown–black
1 3