B. Wang et al. / Chinese Chemical Letters 21 (2010) 794–797
797
products (N-methylaniline 87% (I) and N,N-dimethylaniline 8% (II)), the carbamate products were obtained on 5%.
As for the reaction of secondary aromatic amine with carbonate, no carbamate product was detected (entry 3). These
results indicated that sulfamic acid performed effective selectivity for the reaction between aliphatic amine with DMC,
but failed for aromatic amines. However, we can also change the mind from a different vision that there maybe
possible that sulfamic acid could serve as a specific catalyst for the alkylation of aromatic amine through varying or
modifying reaction conditions, where the prospect of research and development about sulfamic acid deserved in the
further investigation.
In summary, sulfamic acid has been proved to be an efficient catalyst for the synthesis of carbamates from aliphatic
amines and DMC carbonates. Compared with classical methods, the reaction using sulfamic acid as catalyst has
exhibited simple product isolation procedure, improved yield and exclusive selectivity. The alkyl carbamates could be
successfully separated from sulfamic acid catalyst by the use of dichloromethane as a precipitation solvent. Recovery
and reuse of sulfamic acid are also satisfactory. At the same time, the alkylation of aromatic amine could be also
catalyzed potentially by sulfamic acid, which demonstrated the reactivity-specific and green aspect of sulfamic acid.
Acknowledgments
Financial supports from the Beijing Forestry University Excellent Young Scientist Fund (No. BLYX200904),
National Innovation Experiment Program for University Students (No. 091002234) and Major State Basic Research
Development Program of China (973 Program, No. 2010CB732204) are gratefully acknowledged. We wish to thank
Prof. Run-Hua Lu and Prof. Li-Ming Yang for much useful criticism during the preparation of this paper and for many
interesting and helpful discussions.
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