An optically-active bis(alkynylphosphino)ethane-borane derivative represented by formula (1):
wherein R
1
and R
2
, which may be the same or different, each represent an alkyl group, a phenyl group, an alkylsilyl group or a hydrogen atom; R
3
represents a branched alkyl group, an alicyclic hydrocarbon group or an aromatic hydrocarbon group; and the asterisk * indicates an optically-active site.
The derivative (1) is prepared by bromination of, e.g., an (S)-t-butylmethylphosphine-borane, reaction with an alkynyl lithium, deprotonation, followed by oxidative coupling. Deprotection of the derivative (1) by deboranation gives an optically-active bis(alkynylphosphino)ethane derivative useful as a ligand providing an asymmetric catalyst for catalytic asymmetric synthesis. The asymmetric catalyst having the ligand exhibits high selectivity and catalyst activity.
公式(1)表示的具有光学活性的双(炔基膦)
乙烷硼衍
生物:
其中R1和R2,可以相同也可以不同,分别代表一个烷基基团、苯基、烷基
硅基团或氢原子;R3代表一个支链烷基基团、脂
环烃基团或
芳香烃基团;星号*表示一个光学活性位点。
通过
溴化,例如(S)-叔丁基
甲基膦硼烷,与炔基
锂反应,去质子化,然后进行氧化偶联制备衍
生物(1)。通过去
硼烷解保护衍
生物(1),得到一种有用的作为提供不对称催化剂的光学活性双(炔基膦)
乙烷衍
生物,该催化剂具有高选择性和催化活性。