Publication 101
- Enantioselective Olefin Epoxidation using Axially Chiral Biaryl Azepinium Salts as Catalysts. Rapid in-situ Screening and Origin of the Stereocontrol
Roman Novikov, Gérald Bernardinelli, Jérôme Lacour
Adv. Synth. Catal. 2008, 350, 1113-1124
![](/sciences/chimie/pubGA/ga_208.gif)
To unravel the origin of the stereocontrol in epoxidation reactions of unfunctionalized alkenes by diastereomeric biaryl oxaziridinium salts, two series of novel iminium cations were prepared. These moieties combine (Ra)-dimethylbiphenyl or (Ra)-5,5′,6,6′,7,7′,8,8′-octahydrobinaphthyl cores with chiral exocyclic appendages derived from commercially available (S)- or (R)-3,3-dimethylbutan-2-amine and (S)- or (R)-1-phenylpropan-1-amine. Under biphasic enantioselective olefin epoxidation conditions, in-situ generated bromide salts of these derivatives have displayed similar or better asymmetric efficiency than the classical binaphthyl derivatives. A structural analysis was performed in search of a correlation between the origin of the stereocontrol/level of enantioselectivity in the products, and dihedral angles around the biaryl twist of the catalysts.
DOI : 10.1002/adsc.200800022
archive ouverte unige:7051