J.Y. Mang et al. / Journal of Fluorine Chemistry 130 (2009) 259–262
261
Scheme 1.
complex 4i, we studied the amination of aliphatic
ketoesters 1g–h and cyclic -ketoesters 1i–j. As it can be seen by
the results summarized in Scheme 1, the corresponding
aminated -ketoester derivatives 3g–j were obtained in excellent
a
-fluoro-
b
-
Technology Foundation (KOTEF) through the Human Resource
Training Project for Regional Innovation.
b
a
-
b
References
yields and low to high enantioselectivities (20–78% ee).
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3. Conclusions
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In conclusion, we have developed a highly efficient catalytic
enantioselective -amination of -fluoro- -ketoesters using air-
and moisture-stable chiral nickel complex 4i. The desired
aminated products were obtained in good to high yields, and high
enantioselectivities (up to 78% ee) were observed. We believe that
this method provides a practical entry for the preparation of chiral
a
a
b
a
-
a
-fluoro-a-amino acid derivatives, and the availability of these
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General procedure for the
a
-hydrazination of
a-fluoro-b-ketoe-
sters 1: a mixture of -fluoro-
a
b
-ketoester 1 (0.2 mmol) and
catalyst 4i (8.79 mg, 0.01 mmol) in toluene (0.12 mL) was stirred
for 10 min. A solution of t-butyl azodicarboxylate (2, 46.05 mg,
0.4 mmol) in toluene (0.2 mL) was added dropwise over a period of
5 min. The reaction mixture was stirred for 14–34 h at room
temperature. After completion of the reaction, the resulting
solution was concentrated and purified by flash chromatography
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phenylbutyric acid ethyl ester (3ad): ½a D16
¼ ꢁ10:76 (c = 1.00,
ꢀ
CHCl3, 73% ee); 1H NMR (200 MHz, CDCl3) 1.26–1.51 (m, 21H),
4.11–4.35 (m, 2H), 6.63 (br, 1H), 7.41 (t, J = 7.8 Hz, 2H), 7.57 (t,
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441.2037; found: 441.2041; Rt HPLC (80:20, n-hexane: i-PrOH,
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Acknowledgements
This research was financially supported by the Ministry of
Education, Science, Technology (MEST) and Korea Industrial
[10] For a-cyanoketones, see:
(a) J.H. Lee, H.T. Bang, D.Y. Kim, Synlett (2008) 1821–1824;