Catalytic asymmetric synthesis of esters from ketenes

Journal of the American Chemical Society

Volumn 127, Issue 17, 2005, Pages 6176-6177

  Wiskur, Sheryl L ^a   Fu, Gregory C ^a  

^a MASSACHUSETTS INSTITUTE OF TECHNOLOGY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

ESTER DERIVATIVE; KETENE DERIVATIVE; METHANOL; PHENOL;

ACYLATION; ARTICLE; CATALYSIS; CATALYST; CHEMICAL STRUCTURE; ENANTIOMER; ENANTIOSELECTIVITY; PROTON NUCLEAR MAGNETIC RESONANCE; PROTON TRANSPORT; REACTION ANALYSIS; STEREOCHEMISTRY; SYNTHESIS;

CATALYSIS; ESTERS; ETHYLENES; FERROUS COMPOUNDS; KETONES; STEREOISOMERISM;

EID: 18244391730     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja0506152     Document Type: Article

References (25)

1. For leading references, see: (a) Fu, G. C. Acc. Chem. Res. 2004, 37, 542-547.
2. (b) Fu, G. C. Acc. Chem. Res. 2000, 33, 412-420.
3. (c) For more recent work, see: Wilson, J. E.; Fu, G. C. Angew. Chem., Int. Ed. 2004, 43, 6358-6360; Mermerian, A. H.; Fu, G. C. Angew. Chem., Int. Ed. 2005, 44, 949-952.
4. (c) For more recent work, see: Wilson, J. E.; Fu, G. C. Angew. Chem., Int. Ed. 2004, 43, 6358-6360; Mermerian, A. H.; Fu, G. C. Angew. Chem., Int. Ed. 2005, 44, 949-952.
5. Hodous, B. L.; Ruble, J. C.; Fu, G. C. J. Am. Chem. Soc. 1999, 121, 2637-2638.
6. For pioneering studies of the catalytic enantioselective addition of alcohols to ketenes, see: (a) Pracejus, H. Justus Liebigs Ann. Chem. 1960, 634, 9-22.
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16. 3:EtOAc was used to elute catalyst 3). The ester was then purified by flash chromatography.
17. Notes: (a) Upon increasing the scale of the General Procedure, we have obtained essentially identical enantiomeric excess and yield. (b) The catalyst can typically be recovered in ≥80% yield. (c) In a preliminary study, we have obtained 50% ee for the addition of a phenol to a dialkylketene (cyclopentyl methyl ketene). (d) Price of 2-tert-butylphenol; $55 for 2 L (Aldrich).
18. A wide variety of α-alkyl-α-arylacetic acid derivatives are bioactive. For leading references, see: (a) Fenvalerate: The Merck Index, 13th ed.; Merck: Whitehouse Station, NJ, 2001; pp 710-711.
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24. The fact that the ester is generated in high enantiomeric excess despite the presence of an achiral proton donor (the phenol) that is more abundant and more acidic than protonated 3 is readily accommodated within the mechanism outlined in the bottom of Figure 1; the enolate of ion pair A prefers to react with its chiral counterion, rather than participating in a bimolecular reaction with the phenol. This would suggest that, at higher concentration or in a more polar solvent, intermolecular protonation by the phenol might become competitive, leading to an erosion in enantiomeric excess; this is indeed observed.
25. For example, see: Doyle, M. P.; Bagheri, V.; Wandless, T. J.; Harn, N. K.; Brinker, D. A.; Eagle, C. T.; Loh, K.-L. J. Am. Chem. Soc. 1990, 112, 1906-1912.