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VCD configuration of enantiopure/‐enriched tetrasubstituted α‐fluoro cyclohexanones and their use for epoxidation of trans ‐olefins
Author(s) -
Freedman T.B.,
Cao X.,
Nafie L.A.,
SolladiéCavallo A.,
Jierry L.,
Bouerat L.
Publication year - 2004
Publication title -
chirality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.43
H-Index - 77
eISSN - 1520-636X
pISSN - 0899-0042
DOI - 10.1002/chir.20061
Subject(s) - enantiopure drug , chemistry , conformational isomerism , catalysis , stereochemistry , fluorine , medicinal chemistry , organic chemistry , enantioselective synthesis , molecule
The configurations of three enantiopure tetrasubstituted α‐fluoro cyclohexanones (–)‐ 5Ia, (–)‐ 5IIa and (–)‐ 6a were determined by VCD and proved to be (–)‐(2 S ,5 R )‐ 5Ia, (–)‐(2 R, 5 R )‐ 5IIa, and (–)‐(2 R ,5 R )‐ 6a. The VCD study also identified the conformers populated in CDCl 3 solution, including higher‐energy gas‐phase conformers with equatorial fluorine for 5Ia and 5IIa that are stabilized in CDCl 3 solution. Used as catalysts for epoxidation of trans olefins (β‐methylstyrene, stilbene, methyl p ‐methoxy cinnamate) by oxone, it was found that (–)‐ 5Ia is the most efficient for all trans olefins (providing, respectively, 62%, 90% and 66% ee) but that all three ketones provide high ee% with stilbene (78–90% ee). Moreover, the configurations predicted from the stereo outcome of the epoxidation reaction are identical to those determined by VCD. Chirality 16:467–474, 2004. © 2004 Wiley‐Liss, Inc.