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R1 NH2
step A
O
O
I
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NH2
step B
R2
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of N-substituted carbamate in the second step with the contempo-
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Although the aliphatic amines as substrate for the identification
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CO2 and water in the air, which could be lead to some error for the
results, we believe that the aliphatic amines undergo the same
reaction pathway as the aromatic amines. Additional, the urea
intermediate was further prepared with the reaction of HDA, EC,
and ethanol without catalyst. The results showed that HDA conver-
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EHDC selectivity was only 20%. Then, the reactivity of urea inter-
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5.1 wt.% Ni/Fe3O4. The results showed the conversion of urea inter-
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that the urea intermediate was formed easily and the catalyst
mainly promoted the further alcoholysis of the urea intermediate.
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4. Conclusions
In conclusion, a nickel-promoted magnetic iron oxide catalyst
was developed for the effective syntheses of N-substituted carba-
mates. The catalyst could be easily isolated using external mag-
netic field and recovered for several runs without deactivation. In
general, good to excellent yields were obtained with various
amines and alkyl carbamates. Catalyst characterization results sug-
gested the catalytic activity may be derived from the delicate syn-
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Reaction pathway investigations revealed that the N-substituted
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Acknowledgment
This work has been financially supported with the National Nat-
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