Chiral poisoning of rac-diop iridium complexes in the catalytic enantioselective hydrogenation of imines
作者:Rafael Sablong、John A. Osborn、J.W. Faller
DOI:10.1016/s0022-328x(96)06624-7
日期:1997.1
efficient catalysts for the enantioselective hydrogenation of imines. In the present study we have prepared the analogues using rac-diop. Among the possible dimers, there was only a slight preference for the μ-I2 heterodimer [Ir(R,R)-ddiopHI2][Ir(S,S)-diopHI2]}. Although this mixture of dimers was a moderately good catalyst for the hydrogenation of imines, it showed no enantioselectivity, as expected
二聚体Ir(III)络合物[Ir(PP)HI 2 ] 2(PP =对映纯生物磷s)先前已被证明是亚胺对映选择性氢化的有效催化剂。在本研究中,我们使用rac -diop制备了类似物。在可能的二聚体,只有对μ-I的轻微偏爱2异源二聚体物[Ir([R ,- [R)-ddiopHI 2 ]的[Ir(小号,小号)-diopHI 2 ]}。尽管这种二聚体混合物对于亚胺的氢化是中等良好的催化剂,但没有显示出预期的对映选择性。易于获得的氨基膦次膦酸酯配体(+)-(S)-pronop,以[(S)-pronop]:[Ir] tot = 1:1的比例与该二聚体混合物产生不良的催化剂,该催化剂在100h内仅产生了很少的周转。然而,以[(S)-pronop]:[Ir] tot= 1∶2的比例向该二聚体混合物中添加(+)-(S)-nonop产生了亚胺的对映选择性氢化的有效催化剂。由非外消旋二重奏制备的二聚体在催化中未观察到明显的手性扩增。