392
F. Shirini, N.G. Khaligh / Journal of Molecular Liquids 177 (2013) 386–393
Scheme 4. Proposed mechanism for the N-Boc protection of amines in presence DSIMHS.
(
Scheme 2, entry 1). The N-Boc protected cyclohexylamine was formed
exclusively when a mixture of cyclohexylamine (1 mmol) and dicyclo-
hexylamine (1 mmol) were treated with (Boc) O (1 mmol) for 10 min
IR, TLC comparison with authentic compounds) (Scheme 2, entries
experimental procedure. Further work to explore this novel catalyst in
other organic transformations is in progress.
2
(
2
Acknowledgments
and 3). The preferential N-Boc formation of cyclohexylamine over
dicyclohexylamine was due to the steric factor as otherwise the
later was expected to form the N-Boc derivative selectively because
a secondary amine is more nucleophilic than a primary amine. When a
mixture of benzylamine (1 mmol) and dibenzylamine (1 mmol) were
The authors are thankful to the Guilan University Research Council
for the partial support of this work.
References
2
treated with (Boc) O (1 mmol) for 5 min a 26:74% selectivity (GC–MS
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demonstrates the practical recyclability of this catalyst Fig. 4.
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[
[
2
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2
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8
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[
7
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In conclusion, we have developed a simple, efficient and
2
chemoselective protocol for the N-Boc protection of various amines
using DSIMHS as a new ionic liquid catalyst. The protocol is highly
chemoselective offering potential in different applications. The
methodology also has several other advantages such as: high reaction
rates and excellent yields, no side reactions, ease of preparation and
handling of the catalyst, cost efficiency and effective reusability of the
catalyst, use of inexpensive catalyst with lower loading and simple
5
[
[
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