Yoshiro Furukawa

Enantioselective catalytic epoxidation of cinnamate esters

Abstract A broad study of the (salen)Mn(III)-catalyzed asymmetric epoxidation of cis-cinnamate esters reveals that the steric properties of the ester group have a profound influence on enantioselectivity in the epoxidation reaction, with bulkier esters affording highest ees. The sensitivity of the reaction selectivity to the steric properties of the cis-alkene are consistent with a “skewed” side-on approach of olefin to the metal-oxo. The electronic properties of the substrate arene ring substituents do not correlate with epoxidation ee, but instead with the cis/trans partitioning of product formation. Evidence is provided for a non-polar intermediate in a stepwise oxygen-atom-transfer mechanism. The presence of pyridine N-oxide derivatives has a significant effect on catalysts rates and total turnovers, but negligible influence on the stereoselectivity of epoxidation. A mechanistic basis for the role of these additives is proposed. The synthetic applicability of the cinnamate epoxidation methodology is illustrated in the highly enantioselective synthesis of diltiazem.

CsF in organic synthesis. Regioselective nucleophilic reactions of phenols with oxiranes leading to enantiopure β-blockers

Abstract The two modes of the paths in the reaction of oxiranes with phenols are completely controlled by CsF. Glycidyl nosylate undergoes exclusive substitution at the C 1 position whereas the ring-opening (C-3 attack) occurs with epichlorohydrin, glycidol, and 1,2-epoxyalkanes. These reactions provide convenient access to enantiopure β-blockers.