Ir-Catalyzed Enantioselective Hydrogenation of Imines with Xylose Ligands
COMMUNICATIONS
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Experimental Section
¬ √
[4] a) P. Schnider, G. Koch, R. Pretot, G. Wang, M. Bohnen,
Synthesis of [Ir(COD)(1)]BF4 (4)
C. Kr¸ger, A. Pfaltz, Chem. Eur. J. 1997, 3, 887 892;
b) A. Pfaltz, Chimia 2001, 55, 708 714; c) P. von Matt,
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568.
To a chilled ( À 80 8C) solution of [Ir(COD)2]BF4 (150 mg,
0.3 mmol) in dry and deoxygenated dichloromethane (4 mL)
was added dropwise a solution of 1 (250 mg, 0.4 mmol) in dry
and deoxygenated dichloromethane (5 mL). The mixture was
allowed to warm to 0 8C and stirred for 15 min. At that time
diethyl ether (30 ml) was added to precipitate the desired
product as a pale purple solid; yield: 322 mg (76%); Anal.
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calcd.: C 52.65, H 5.85%; found: C 52.80; H 5.69; 31P NMR
(161.9 MHz, CDCl3): d 114.1 (d, 2JP, P 27.4 Hz), 110.2 (d, JP, P
2
27.5 Hz).
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General Procedure for the Ir-Catalyzed
Hydrogenation of Imines
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Bˆrner, Tetrahedron: Asymmetry 1999, 10, 4009 4015.
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T. V. RajanBabu, in Process Chemistry in the Pharma-
ceutical Industry; (Ed.: K. G. Gadamasetti), Marcel
A flask (150 mL) with a magnetic stirring bar was charged
under a nitrogen atmosphere with a solution of [Ir(COD)1]BF4
(0.022 mmol, 28.09 mg) and N-(phenylethylidene)aniline (7;
2 mmol, 0.39 g) in 10 mL of anhydrous and deoxygenated
CH2Cl2 and placed in a steel autoclave. The reaction mixture
was stirred overnight at room temperature under 25 bar of H2
pressure. Gas chromatographic analyses were performed using
a Hewlett-Packard 5890A. The conversion was measured with
an Ultra-2 (5% diphenylsilicone/95% dimethylsilicone) col-
umn (25 m  0.2 mm F). The enantiomeric excess of N-
phenyl-1-phenylethylamine (8) was determined by chiral gas
chromatography after derivatization into the acetamide com-
pound. Chiral column FS-Cyclodex b-I/P, 50 m  0.25 mm.
¬
¡
Dekker Inc., New York, 1999; c) M. Dieguez, O. Pamies,
¬
A. Ruiz, S. Castillon, C. Claver, Chem. Commun. 2000,
1607 1608.
¡
[15] a) O. Pamies, G. Net, A. Ruiz, C. Claver, Eur. J. Inorg.
Acknowledgements
¡
Chem. 2000, 1287 1294; b) O. Pamies, G. Net, A. Ruiz,
Financial support by Bayer AG is acknowledged. Technical
assistance by the Servei de Recursos Cientifics (URV) is
acknowledged.
C. Claver, Eur. J. Inorg. Chem. 2000, 2011 2015; c) O.
¡
¬
Pamies, M. Dieguez, G. Net, A. Ruiz, C. Claver, J. Org.
Chem. 2001, 66, 8364 8369.
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References
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Iridium-Catalyzed Enantioselective Hydrogenation of Imines with Xylose Diphosphite and Diphosphinite Ligands
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