化学
催化作用
树枝状大分子
铑
不对称氢化
齿合度
部分
水解
位阻效应
吡那考
磷酰胺
有机化学
药物化学
对映选择合成
金属
DNA
生物化学
寡核苷酸
作者
Weijun Tang,Yiyong Huang,Yong He,Qing‐Hua Fan
标识
DOI:10.1016/j.tetasy.2006.01.013
摘要
A new class of dendritic monodentate phosphoramidite ligands were synthesized through substitution of the dimethylamino moiety in MonoPhos by the Fréchet-type dendritic wedge and applied in the asymmetric hydrogenation of α-dehydroamino acid esters and dimethyl itaconate. High enantioselectivities (up to 97.9% ee) and catalytic activities (up to 4850 h−1 TOF) were achieved, which are better or comparable to those obtained from MonoPhos. The third generation dendrimer catalyst gave the slightly lower catalytic activity relative to the lower generation ones. The steric shielding by the dendrimer could stabilize the rhodium complex against decomposition caused by hydrolysis in a protic solvent. The inactive catalysts (RhL3 and RhL4) were activated by addition of a free metal precursor Rh(COD)2BF4, and showed high enantioselectivities and catalytic activities.
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