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4 Conclusions
In summary, a base-free Co(acac)3/BMMImCl catalyst sys-
tem was developed for the syntheses of N,N′-disubstituted
ureas from amines and CO2. Good yields to N,N′-dialky-
lureas and acceptable yields to N,N′-diarylureas were ob-
tained when the reaction was carried out at 160 °C for 10 h.
In comparison with the reported catalyst systems, the
Co(acac)3/BMMImCl not only exhibits good catalytic per-
formance but also avoids the use of strong organic base or a
large amount of chemical dehydrants as sacrificial agents,
which is more consistent with the rules of green chemistry.
This work was financially supported by the National Natural Science
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