Asymmetric Michael Addition of Phenylboronic Acid to Cycloalkenones Using Aminoalcohol-Appended b?Cyclodextrins

Aminoalcohol ligands-appended β-cyclodextrins(β-CD)were prepared by the nucleophilic substitution of aminoethanol derivatives to β-CD-6-OTs at 80℃. The asymmetric 1,4-addition of phenylboronic acid to cycloalkenones was carried out in the presence of 2-aminoethanol-appended β-CD(β-CD-6-AEt),Ni(II)or Cu(II)and Pd(OAc)2 in aqueous solution at 0℃. The complexes of β-CD-6-AEt with Ni(II)and Cu(II)formed a highly enantioselective catalyst for the asymmetric addition,but it did not accelerate the reaction compared with β-CD. The best chiral induction,59% ee,was achieved in the combination of β-CD-6-AEt and Ni(II)to give the corresponding adduct with(R)-configuration whereas the use of the Cu(II)complex give the product with the opposite configuration(51% ee,(S))