手性硼酸酯介入的不对称合成3† (R)-或(S)-1,1'-联-2-萘酚硼酸-(S)-脯氨酸酐促进的前手性亚胺的不对称硼烷还原

手性螺硼酸酯(R)-或(S)-1,1'-联-2-萘酚硼酸-(S)-脯氨酸酐(R,S)-1或(S,S)-1]对前手性亚胺硼烷还原的不对称催化活性被观察到. 在(R,S)-1或 (S,S)-1存在下, 由前手性二烷基酮或烷基苯酮与苯胺缩合生成的前手性亚胺在THF中被硼烷还原, 高产率地给出手性仲胺, 其对映体纯度高达74% ee. 其中, 三种手性仲胺N-(2-戊基)苯胺, N-(3-甲基-2-丁基)苯胺和N-(4-甲基-2-戊基)苯胺]系首次合成.

Chiral Borate Esters in Asymmetric Synthesis 3† Asym-metric Borane Reduction of Prochiral Imines Promoted by (R)- or (S)-1,1-Bi-2- naphthoxyboric Acid (S)-Proline An-hydride

Asymmetric catalytic activity of chiral spiroborate esters, (R)- or (S)-1,1-bi-2-naphthoxyboric acid (S)-proline anhydride (R,S)-1 or (S,S)-1], toward borane reduction of prochiral imines has been observed. In the presence of (R,S)-1 or (S,S)-1, prochiral imines generated from con-densation of aniline and a prochiral dialkyl ketone or alkylphenyl ketone were reduced by borane in THF to give chiral secondary amines in high yield and up to 74% ee. Among them, N-(2-pentyl)aniline, N-(3-methyl-2-butyl)aniline and N-(4-methyl-2-pentyl)aniline have not been reported before.