Blackmond D G, Lightfoot A, Pfaltz A, Rosner T, Schnider P, Zimmermann N
Max-Planck-Institut fur Kohlenforschung, Mulheim an der Ruhr, Germany.
Chirality. 2000 Jun;12(5-6):442-9. doi: 10.1002/(SICI)1520-636X(2000)12:5/6<442::AID-CHIR25>3.0.CO;2-F.
Cationic iridium complexes with chiral phosphinooxazoline ligands are efficient catalysts for the enantioselective hydrogenation of olefins. The complexes are readily prepared, air-stable, and easy to handle. In contrast to chiral rhodium- and ruthenium-phosphine catalysts, they do not require the presence of a polar coordinating group near the C=C bond. In the hydrogenation of unfunctionalized trisubstituted 1,2-diaryl-olefins, high enantioselectivities of >95% ee with full conversion and turnover frequencies of >7,000 h-1 can be achieved, using 0.1 mol% of catalyst with tetrakis[3, 5-bis(trifluoromethyl)phenyl]borate (TFPB or BARF) as the counterion. The corresponding hexafluorophosphate or tetrafluoroborate salts give low conversion due to deactivation of the catalyst during the reaction. Substrates with polar substituents such as allylic alcohols, on the other hand, afford better results with the hexafluorophosphate salts.
具有手性膦基恶唑啉配体的阳离子铱配合物是烯烃对映选择性氢化的高效催化剂。这些配合物易于制备，对空气稳定且易于处理。与手性铑和钌膦催化剂不同，它们不需要在C = C键附近存在极性配位基团。在未官能化的三取代1,2 - 二芳基烯烃的氢化反应中，使用0.1 mol%的催化剂和四[3, 5 - 双（三氟甲基）苯基]硼酸盐（TFPB或BARF）作为抗衡离子，可以实现>95% ee的高对映选择性、完全转化以及>7000 h-1的周转频率。相应的六氟磷酸盐或四氟硼酸盐由于在反应过程中催化剂失活而转化率较低。另一方面，具有极性取代基的底物如烯丙醇，使用六氟磷酸盐时效果更好。
