Organisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg (Germany).
Angew Chem Int Ed Engl. 2015 Mar 16;54(12):3580-6. doi: 10.1002/anie.201412098. Epub 2015 Feb 23.
Asymmetric catalysis using enantiomerically pure catalysts is one of the most widely used methods for the preparation of enantiomerically pure compounds. The separate synthesis of both enantiomerically pure compounds requires tedious and time-consuming preparation of both enantiomerically pure catalysts or chiral separation of the racemic products. Here, we report a stereochemically flexible diastereomeric rhodium(I) catalyst for asymmetric hydrogenations of prochiral (Z)-α-acetamidocinnamates and α-substituted acrylates, which changes its enantioselectivity depending on the temperature to produce each enantiomerically pure compound in high yield with constant high enantioselectivity over time. The same axially chiral rhodium(I) catalyst produces (R)-phenylalanine derivatives in enantiomeric ratios of up to 87:13 (R/S) at low temperature and up to 3:97 (R/S) of the corresponding S enantiomers after re-equilibration of the same catalyst at elevated temperature.
使用对映体纯催化剂的不对称催化是制备对映体纯化合物最广泛使用的方法之一。两种对映体纯化合物的单独合成需要繁琐且耗时的两种对映体纯催化剂的制备或外消旋产物的手性分离。在这里，我们报告了一种立体化学灵活的手性钌（I）催化剂，用于对映选择性氢化前手性（Z）-α-乙酰氨基肉桂酸酯和α-取代丙烯酸酯，该催化剂根据温度改变其对映选择性，以高产率长时间恒高质量地生成每种对映体纯化合物。相同的轴向手性钌（I）催化剂在低温下产生高达 87:13（R/S）的对映体比的苯丙氨酸衍生物，并且在相同催化剂在高温下重新平衡后，相应的 S 对映体高达 3:97（R/S）。
