L-proline catalyzed asymmetric transfer aldol reaction ...



L-proline catalyzed asymmetric transfer aldol reaction between diacetone alcohol and aldehydes:

S. Chandrasekhar, * Ch. Narsihmulu, N. Ramakrishna Reddy and S. Shameem Sultana.

Indian Institute of Chemical Technology, Hyderabad-500 007, India.

Fax: (+91)-40-27160512; E-mail: srivaric@iict.res.in

General:

The following chemicals were purchased from Aldrich and used as supplied: L-proline, 4-nitrobenzaldehyde, 2-chloro-5-nitrobenzaldehyde, isobutyraldehyde, cyclohexyl carboxaldehyde and freshly distilled diacetone alcohol.

1H NMR spectra were recorded as solutions in CDCl3 at room temperature on a Varian Gemini spectrometer at 200 MHz, Brucker 300 MHz, and mass spectra were recorded on Finnigan MAT 1020B or micro mass VG 70-70H spectrometer operating at 70eV using direct inlet system.

ee of the products determined by chiral HPLC analysis using chiralcel OB-H column.

Physical data of the products are as follows:

4-Hydroxy-4- (4’-nitrophenyl)-butan-2-one: Spectral data are identical to authentic sample and to those previously reported.1

4-Hydroxy-4- (4’-bromophenyl)-butan-2-one: Spectral data are identical to authentic sample and to those previously reported. 1

4-Hydroxy-4- (2’-chlorophenyl)-butan-2-one: Spectral data are identical to authentic sample and to those previously reported. 1

4-Hydroxy-4-(3’-nitro-phenyl)-butan-2-one: Spectral data are identical to authentic sample and to those previously reported. 1

(4R)-4-(Cyclohexyl)-4-hydroxy-2-butanone: Spectral data are identical to authentic sample and to those previously reported. 1

4-Hydroxy-5-methyl-hexan-2-one: Spectral data are identical to authentic sample and to those previously reported. 1

4-Hydroxy-4-(2’-nitro-phenyl)-butan-2-one: Spectral data are identical to authentic sample and to those previously reported.2

4-Hydroxy-4-(4’- methoxy-phenyl)-butan-2-one: Spectral data are identical to authentic sample and to those previously reported.2

4-Hydroxy-4-(2’- chloro- 5’-nitro-phenyl)-butan-2-one:

1H NMR (CDCl3, 200 MHz): δ 8.58-8.52 (m, 1H), 8.16-8.04 (m, 1H), 7.44 (d, J= 9.6 Hz, 1H),

5.43 (d, J= 12.0 Hz, 1H), 3.65 (bs, 1H), 3.08-2.52 (m, 2H), 2.24 (s,3H).

EI MS : m/z 243 (M+),183, 43.

Enantiomeric excess: 64 % determined by HPLC using chiralcel OB-H column (Hexane: isopropanol / 80: 20), tR = 6.37 (major), tR = 7.01 (minor).

References:

1. Z. Tang, F. Jiang, L. Yu, X. Cui, L. Gong, A. Mi, Y. Jiang and Y. Wu, J. Am. Chem. Soc., 2003, 125, 5262.

2. P. Kotrusz, I. Kmentova, B. Gotov, S. Toma and E. Solcaniova, Chem. Commun., 2002, 2510.

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