Enantiomerically pure (S,S) -1,2-bis[(o-alkylphenyl) phenylphosphino]ethanes (o-alkylphenyl = o-methylphenyl, o-ethylphenyl, o-isopropylphenyl, 5',6',7',8'-tetrahydro-naphthyl) , (S,S) -1,2-bis (alkyl-methylphosphino) ethanes (alkyl = t-butyl, 1-adamantyl, 1-methylcyclo-hexyl, 1,1-diethylpropyl, cyclopentyl, cyclohexyl) (abbreviated as BisP*) , and (R,R) -1,1-bis (alkylmethylphosphino) methanes (alkyl = isopropyl, t-butyl, cyclohexyl, phenyl) (abbreviated as MiniPHOS) were prepared from phosphorus trichloride via short routes using phosphine-boranes as intermediates. The crystal structures of cationic rhodium complexes, [Rh ((S,S) -1,2-bis ((phenyl) (5',6',7',8'-tetrahydronaphthyl) phosphino) ethane) (cod)]BF4, [Rh ((S,S) -t-Bu-BisP* (nbd))]BF4, and [Rh ((R,R) -t-Bu-MiniPHOS) 2]PF6, clearly indicate the ideal asymmetric environments. These ligands exhibited an excellent to almost perfect level of enantioselectivity in asymmetric hydrogenations of a-dehydroamino acid derivatives and other catalytic asymmetric reactions.
CATALYTIC ASYMMETRIC HYDROGENATIONS WITH POLYMER SUPPORTED CHIRAL PYRROLIDINEPHOSPHINE–RHODIUM COMPLEXES
