Catalytic asymmetric couplings of ketenes with aldehydes to generate enol esters

Angewandte Chemie - International Edition

Volumn 44, Issue 29, 2005, Pages 4606-4608

  Schaefer, Carsten ^a   Fu, Gregory C ^a  

^a MASSACHUSETTS INSTITUTE OF TECHNOLOGY   (United States)

Author keywords

Aldehydes; Asymmetric catalysis; Esters; Ketenes

Indexed keywords

ALCOHOLS; ALDEHYDES; CARBOXYLIC ACIDS; CATALYSIS; CATALYSTS; ESTERS;

ASYMMETRIC COUPLINGS; ENOL ESTERS; FERROCENYL CATALYSTS; KETENES;

DERIVATIVES;

ALDEHYDE; ESTER; ETHYLENE DERIVATIVE; KETENE; KETONE;

ARTICLE; CATALYSIS; CHEMICAL MODEL; CHEMISTRY; STEREOISOMERISM;

ALDEHYDES; CATALYSIS; ESTERS; ETHYLENES; KETONES; MODELS, CHEMICAL; STEREOISOMERISM;

EID: 22744444589     PISSN: 14337851     EISSN: None     Source Type: Journal    
DOI: 10.1002/anie.200501434     Document Type: Article

References (37)

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28. 3 at 0°C. The resulting solution was stirred at 0°C, and then the reaction was quenched by the addition of MeOH (1 mL). The solvent was removed by rotary evaporation, and the residue was purified by column chromatography.
29. 2; however, not N-methylpyrrolidone); b) Slightly lower ee values were observed at room temperature; c) Typically, ca. 85% of catalyst 1 can be recovered at the end of the reaction.
30. These enol esters are more reactive than the aryl esters produced by the addition of 2-iert-butylphenol to ketenes (see ref. [4b]).
31. For other processes catalyzed by 1 that are believed to proceed through chiral enolate A, see: a) B. L. Hodous, G. C. Fu, J. Am. Chem. Soc. 2002, 124, 1578-1579;
32. b) Ref. [8].
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34. For a process catalyzed by 1 that is believed to proceed through an analogous chiral Brønsted base/acid pathway, see ref. [4b].
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36. This behavior contrasts with enantioselective additions of 2-tert-butylphenol to ketenes catalyzed by 1 in which the catalyst deprotonates the phenol; the mechanism is likely a chiral Brønsted acid catalyzed pathway (see ref. [4b]).
37. 1/2 ≈ 1 h).