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A Highly Enantioselective Phosphabicyclooctane Catalyst for the Kinetic Resolution of Benzylic Alcohols.
- Source :
-
Journal of the American Chemical Society . 4/9/2003, Vol. 125 Issue 14, p4166. 8p. 4 Diagrams, 3 Charts. - Publication Year :
- 2003
-
Abstract
- A new class of chiral phosphines belonging to the P-aryl-2-phosphabicyclo[3.3.0]octane family (PBO) has been prepared by enantioselective synthesis starting from lactate esters and 2,2-dimethylcyclopentanone enolate 5. A selective enolate alkylation method has been developed for preparation of 9 and 10 using a chelating ester substituent in the triflate alkylating agent 11. Subsequent conversion to the PBO catalysts 2 and 39 relies on a diastereoselective cyclization from the cyclic sulfate 17 and LiPHAr to afford the more hindered endo-aryl phosphines. These phosphines function as efficient catalysts for the kinetic resolutions of aryl alkyl carbinols by benzoylation (16, 21, 22) or iso-butyroylation in the case of the less hindered aryl alkyl carbinol substrates. With o-substituted aryl alkyl carbinols, the enantioselectivities exceed 100, and s = 380 ± 10 has been demonstrated in the case of methyl mesityl carbinol. The PBOcatalyzed acylations probably involve a P-acylphosphonium carboxylate intermediate and a tightly ion paired transition state. [ABSTRACT FROM AUTHOR]
- Subjects :
- *ENANTIOSELECTIVE catalysis
*PHOSPHINE
*LACTATES
Subjects
Details
- Language :
- English
- ISSN :
- 00027863
- Volume :
- 125
- Issue :
- 14
- Database :
- Academic Search Index
- Journal :
- Journal of the American Chemical Society
- Publication Type :
- Academic Journal
- Accession number :
- 9549163
- Full Text :
- https://doi.org/10.1021/ja021224f