NJC
Paper
kindly acknowledged for providing spectral analysis of the
products. CSIR, New Delhi, is kindly acknowledged for funding
and providing the research fellowship to SK.
Notes and references
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Scheme 2 L-Proline-catalyzed synthesis of methylcarbamate.
of amines and DMC under mild reaction conditions. Operational
simplicity, the environmentally benign nature of DMC and metal
free catalysts and good-to-excellent chemical yields are key
features of the present protocol. Moreover, easy work-up and
high selectivity of the products make the developed protocol
more attractive from environmental and industrial viewpoints.
Experimental
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General
All commercially available substrates and solvents were used as
received. L-proline and TBAB were purchased from Sigma-Aldrich
and used as received. The melting points were determined in
open-capillaries on a Buchi apparatus and are uncorrected. The IR
spectra were recorded on a Perkin-Elmer FT-IR X 1760 instrument.
1H NMR and 13C NMR were recorded on a Bruker AVANCE III-400
MHz NMR spectrometer using TMS as the internal reference.
General experimental procedure
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A 50 ml round bottomed flask equipped with a magnetic stir bar
and reflux condenser was charged with amine (2.0 mmol), DMC
(10 mmol), and L-proline/TBAB (5 mol%). The resulting mixture was
stirred at room temperature for the desired time period as shown in
Table 2. The progress of the reaction was monitored by TLC (SiO2).
After completion of the reaction, the mixture was diluted with
methanol and analyzed by GCMS to determine the conversion
and selectivity. The methanol was evaporated under vacuum and
the resulting mixture was purified by column chromatography by
using hexane : diethyl ether (6 : 4) as the eluent. The isolated yield of
the pure N-methyl carbamates is given in Table 2. The identity of the
products was determined by comparing their physical and spectral
data with those of authentic samples.
Acknowledgements
We are thankful to the Director, IIP, for his kind permission to 10 T. Baba, M. Fujiwara, A. Oosaku, A. Kobayashi, R. G. Deleon
publish these results. Analytical division of the Institute is
and Y. Ono, Appl. Catal., A, 2002, 227, 1–6.
c
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2013
New J. Chem.