Chiral Ligand PPFA And FAA Catalyse Asymmetric Addition Reaction

The target of this paper is to apply old catalysts to new asymmetric reaction. Chiral ferrocenyl phosphoramidite ligands (R , S) PPFA and (S , R) PPFA have been reported before 1981. Chiral ferrocenyl aziridino alcohol ligand was synthesized in our laboratory three years ago by professer Mincan-Wang . Now we try to use both of them to copper-catalyzed asymmetric conjugate addition of diethylzinc to substitutedβ-nitro-styrene and asymmetric aryl transfer reaction to aldehydes with boronic acids as aryl source , respectively . Both of them got moderate or excellent results.(I) Copper-catalyzed asymmetric conjugate addition of diethylzincto substitutedβ-Nitro-styreneEnantioselective conjugate additions of organometallic reagents to nitroalkenes provides a useful carbon-carbon bond forming process. Among such processes, the copper-catalyzed dialkylzinc addition to nitroalkenes has recently been extensively attented by chemists in this field . The enantioselectivity of this reaction has been modest to fairly good except for only a few particular types of substrates with excellect selectivity was achieved. We use old chiral phosphoramidite ligand PPFA whith copper catalyzed a series of substitutedβ-nitro-styrene, only the ortho-substitutedβ-nitro-styrene got moderate results. (II) Highly Enantioselective Preparation of (R)-and ( S )-Diarylmethanols Catalyzed by the Same Chiral FerrocenylAziridino AlcoholThe efficient and highly enantioselective synthesis of chiral diarylmethanol is of primary importance because some of them are important intermediates for preparation of pharmacologically and biologically active compounds . Our group find that (2S)-l-ferrocenylmethylaziridin-2-yl(diphenyl)methanol L is a highly effective catalyst in aryl transfer reaction to aldehydes with boronic acids as aryl source. (S)-diarylmethanol can be easily obtained in the present of a catalytic amount of ligand L. With the improvement of our work, we found an interesting phenomena , the R or S enantiomers of a series of given diarylmethanols can be easily obtained in high yields with excellent enantioselectivities simply by the reverse combinations of both reaction partners.