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
New biphenyl iminium salt catalysts for highly enantioselective asymmetric epoxidation: role of additional substitution and dihedral angle
作者:Philip C. Bulman Page、Christopher J. Bartlett、Yohan Chan、Steven M. Allin、Michael J. McKenzie、Jérôme Lacour、Garth A. Jones
DOI:10.1039/c6ob00542j
日期:——
The effects upon enantioselectivity of substitution in the heterocyclic ring of biaryl iminiumsalt catalysts for alkene epoxidation are reported. The influence of dihedral angle in these systems has been investigated. Enantioselectivities of up to 97% ee were observed.