Highly Enantioselective Reformatsky Reaction of Ketones: Chelation-Assisted Enantioface Discrimination

Organic Letters

Volumn 4, Issue 18, 2002, Pages 3051-3054

  Ojida, Akio ^a,b   Yamano, Toru ^a   Taya, Naohiro ^a   Tasaka, Akihiro ^a  

^a TAKEDA PHARMACEUTICAL COMPANY LIMITED   (Japan)

^b KYUSHU UNIVERSITY   (Japan)

Author keywords

[No Author keywords available]

Indexed keywords

ALCOHOL DERIVATIVE; CINCHONA ALKALOID; CINCHONINE; ESTER; HYDROXYACID; KETONE;

ARTICLE; CHEMISTRY; ISOLATION AND PURIFICATION; METHODOLOGY; STEREOISOMERISM; SYNTHESIS;

ALCOHOLS; CHEMISTRY, PHARMACEUTICAL; CINCHONA ALKALOIDS; ESTERS; HYDROXY ACIDS; KETONES; STEREOISOMERISM;

EID: 0037026463     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol0263189     Document Type: Article

References (24)

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17. Enantioselective indium-induced Reformatsky-type reaction using cinchona alkaloids has been reported: Johar, P. S.; Araki, S.; Butsugan, Y. J. Chem. Soc., Perkin Trans. 1 1992, 711.
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20. Pyridine enhances the enatioselectivity and also accelerates the reaction at low temperatures. In the absence of the pyridine, the reaction with the ketone 1 was not completed even after 12 h at -40 °C (∼80%); however, the reaction was completed within 4 h in the presence of 4 equiv of pyridine (Table 2).
21. Typical Experimental Procedure. The Reformatsky reagent (0.47 M, 4.3 mL, 2.0 mmol) was added to a suspension of cinchonine (220 mg, 0.75 mmol) in dry THF (1.0 mL) at 0 °C under an argon atmosphere. After the mixture was stirred for 10 min, pyridine (0.15 mL, 2.0 mmol) was added, and the mixture was stirred for 20 min. The ketone (0.50 mmol) dissolved in dry THF (20 mL) was added to the mixture over a period of 10 min at -40 °C. After being stirred at the same temperature for 4 h, the resulting mixture was diluted with 1 N aqueous hydrochloric acid and extracted with ethyl acetate. The extracts were washed with saturated aqueous sodium hydrogen carbonate and brine followed by drying over sodium sulfate. After removal of the solvent in vacuo, the product was subjected to HPLC analysis.
22. 2-nitrogen as a directing group, see: (a) Porter, N. A.; Feng, H.; Kavrakova, I. K. Tetrahedron Lett. 1999, 40, 6713. (b) Sibi, M. P.; Shay, J. J.; Ji, J. Tetrahedron Lett. 1997, 38, 5955. (c) Kashima, C.; Takahashi, K.; Fukuchi, I.; Fukusawa, K. Heterocycles 1997, 44, 1.
23. 2-nitrogen as a directing group, see: (a) Porter, N. A.; Feng, H.; Kavrakova, I. K. Tetrahedron Lett. 1999, 40, 6713. (b) Sibi, M. P.; Shay, J. J.; Ji, J. Tetrahedron Lett. 1997, 38, 5955. (c) Kashima, C.; Takahashi, K.; Fukuchi, I.; Fukusawa, K. Heterocycles 1997, 44, 1.
24. 2-nitrogen as a directing group, see: (a) Porter, N. A.; Feng, H.; Kavrakova, I. K. Tetrahedron Lett. 1999, 40, 6713. (b) Sibi, M. P.; Shay, J. J.; Ji, J. Tetrahedron Lett. 1997, 38, 5955. (c) Kashima, C.; Takahashi, K.; Fukuchi, I.; Fukusawa, K. Heterocycles 1997, 44, 1.