Premium
Asymmetric Epoxidation of trans ‐Olefins via Chiral Dioxiranes: A Possible Contribution of axial Approaches in the case of Tri‐ and Tetrasubstituted α‐Fluoro Cyclohexanones
Author(s) -
SolladiéCavallo Arlette,
Bouérat Laëtitia,
Jierry Loïc
Publication year - 2001
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/1099-0690(200112)2001:23<4557::aid-ejoc4557>3.0.co;2-a
Subject(s) - dioxirane , chemistry , desymmetrization , olefin fiber , substituent , enantiomer , enantiomeric excess , fluorine , yield (engineering) , chirality (physics) , stereochemistry , organic chemistry , enantioselective synthesis , medicinal chemistry , catalysis , materials science , nambu–jona lasinio model , chiral symmetry breaking , physics , quantum mechanics , quark , metallurgy
During the asymmetric epoxidation of stilbene and methyl p ‐methoxycinnamate with chiral dioxiranes (derived from 2,2′,5‐tri‐ and 2,2′,5,5′‐tetrasubstituted cyclohexanones with an axial fluorine at C2) a 26 to 30% increase in ee was observed upon desymmetrization of the axial face of the dioxirane (through disubstitution at C5 or introduction of a fluorine on the equatorial i Pr‐substituent located at C5), which suggests a contribution of the axial approach of the olefin to the dioxirane (in addition to the main equatorial approach). The two ketones 5a and 6a , which do not undergo Baeyer− Villiger oxidation, can be used in substoichiometric amounts and are fully recovered after the reactions, provide epoxides in high yield (75−90%) and high (95:5) to satisfying (83:17 to 87:13) enantiomeric ratios.