A Chiral-Bridged Aminotroponiminate Complex of Lutetium as Catalyst for the Asymmetric Hydroamination

Abstract

The enantiomerically pure bridged aminotroponiminate S,S-H2{(iPrATI)2diph}, in which two amino-isopropyl-troponimine moieties are linked by 1,2-(S,S)-diamino-1,2-diphenylethane, has been prepared. The chiral lutetium alkyl complex of composition [(R,R)-{(iPrATI)2diphLuCH2SiMe3(THF)] (3) was obtained via two synthetic approaches. In the first approach the dipotassium salt [(S,S)-K2{(iPrATI)2diph}] (1) of the ligand was reacted via a salt metathesis with lutetium trichloride to give [(S,S)-{(iPrATI)2diph}LuCl(THF)] (2). Reaction of 2 with LiCH2SiMe3 resulted in 3. Compound 3 can also be obtained by the reaction of [Lu(CH2SiMe3)3(THF)2] with (S,S)-H2{(iPrATI)2diph} under elimination of Me4Si. The alkyl complex 3 was used as catalyst in the intramolecular hydroamination reaction of nonactivated terminal aminoolefins. Good catalytic activities and moderate enantioselectivties were observed.