Towards more chemically robust polymer-supported chiral catalysts: alpha,alpha-diphenyl-L-prolinol based catalysts for the reduction of prochiral ketones with borane.
alpha,alpha-Diphenyl-L-prolinol derivatives with para-bromo substituents in either one or both of the phenyl rings are easily bound to crosslinked polystyrene beads containing phenylboronic acid residues by Suzuki couplings. By using extended reaction periods boronic acid residues that do not take part in the couplings are simply lost by hydrolysis. The polymer-supported (PS) alpha,alpha-diphenyl-L-prolinols were used to catalyse reductions of several prochiral ketones with borane in tetrahydrofuran at 22 degrees C. The expected secondary alcohols were obtained in high chemical yields and ees were generally in the range 79-97%. One PS catalyst was recycled 14 times without loss of stereochemical performance.
Kell
Roger J
RJ
Department of Chemistry University of Manchester, Oxford Road, Manchester, UK M13 9PL.
Hodge
Philip
P
Snedden
Peter
P
Watson
David
D
D001880:Boranes / Q000737:chemistry*; D002384:Catalysis; D003432:Cross-Linking Reagents / Q000494:pharmacology; D006868:Hydrolysis; D007659:Ketones / Q000737:chemistry*; D008956:Models, Chemical; D011108:Polymers / Q000737:chemistry*; D013237:Stereoisomerism
D001880:Boranes; D003432:Cross-Linking Reagents; D007659:Ketones; D011108:Polymers