Comparative Study of Bifunctional Mononuclear and Dinuclear Amidoiridium Complexes with Chiral C−N Chelating Ligands for the Asymmetric Transfer Hydrogenation of Ketones
作者:Yasuhiro Sato、Yoshihito Kayaki、Takao Ikariya
DOI:10.1002/asia.201600955
日期:2016.10.20
amido‐bridged dinuclear complexes (3 a and 3 a’), more sterically hindered complexes were solely transformed into the coordinatively unsaturated mononuclear amido complexes (3 b and 3 c), which can serve as real catalyst species in the asymmetric transfer hydrogenation. The structural difference in the C−N chelate framework markedly affected the catalytic performance. Among them, amido complex 3 c showed a pronounced
通过光学活性的伯苄胺如O-甲硅烷基化(S)-2-氨基-2-苯基乙醇(1a和1a'),(R)-5-氨基-6,7,8,9-四氢-5 H-苯并环庚烯(1 b)和(R)-1-苯基-2-2,2-二甲基丙胺(1 c)。尽管用源自1a和1a'的胺络合物处理KO t Bu可以得到酰胺桥联的双核络合物(3a和3a'),空间位阻较大的配合物仅转化为配位不饱和的单核酰胺配合物(3b和3c),可在不对称转移氢化反应中用作真正的催化剂。CN螯合物骨架中的结构差异显着影响了催化性能。其中,即使在−30°C的低温下,酰胺基络合物 3 c仍具有明显的催化苯乙酮在2-丙醇中转移氢化的能力。在2丙醇中3 c的反应中还发现了氢化铱络合物(4 c),这为将氢转移到前手性酮中的对映异构步骤提供了机械原理的见解。