State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, PR China.
Chemistry. 2009 Sep 28;15(38):9855-67. doi: 10.1002/chem.200900899.
Well-designed, self-assembled, metal-organic frameworks were constructed by simple mixing of multitopic MonoPhos-based ligands (3; MonoPhos=chiral, monodentate phosphoramidites based on the 1,1'-bi-2-naphthol platform) and [Rh(cod)(2)]BF(4) (cod=cycloocta-1,5-diene). This self-supporting strategy allowed for simple and efficient catalyst immobilization without the use of extra added support, giving well-characterized, insoluble (in toluene) polymeric materials (4). The resulting self-supported catalysts (4) showed outstanding catalytic performance for the asymmetric hydrogenation of a number of alpha-dehydroamino acids (5) and 2-aryl enamides (7) with enantiomeric excess (ee) ranges of 94-98 % and 90-98 %, respectively. The linker moiety in 4 influenced the reactivity significantly, albeit with slight impact on the enantioselectivity. Acquisition of reaction profiles under steady-state conditions showed 4 h and 4 i to have the highest reactivity (turnover frequency (TOF)=95 and 97 h(-1) at 2 atm, respectively), whereas appropriate substrate/catalyst matching was needed for optimum chiral induction. The former was recycled 10 times without loss in ee (95-96 %), although a drop in TOF of approximately 20 % per cycle was observed. The estimation of effective catalytic sites in self-supported catalyst 4 e was also carried out by isolation and hydrogenation of catalyst-substrate complex, showing about 37 % of the Rh(I) centers in the self-supported catalyst 4 e are accessible to substrate 5 c in the catalysis. A continuous flow reaction system using an activated C/4 h mixture as stationary-phase catalyst for the asymmetric hydrogenation of 5 b was developed and run continuously for a total of 144 h with >99 % conversion and 96-97 % enantioselectivity. The total Rh leaching in the product solution is 1.7 % of that in original catalyst 4 h.
通过简单混合多齿 MonoPhos 配体（3；MonoPhos=基于 1,1'-联-2-萘酚平台的手性单齿膦酰胺）和 [Rh(cod)(2)]BF(4)（cod=环辛-1,5-二烯），构建了设计合理、自组装的金属有机骨架。这种自支撑策略允许在不使用额外添加支撑的情况下进行简单高效的催化剂固定化，得到了特征良好、不溶（在甲苯中）的聚合物材料（4）。所得的自支撑催化剂（4）在不对称氢化一系列 α-去氢氨基酸（5）和 2-芳基烯酰胺（7）方面表现出优异的催化性能，对映体过量（ee）分别为 94-98%和 90-98%。4 中的连接基部分对反应性有显著影响，尽管对对映选择性的影响较小。在稳态条件下获得的反应曲线表明，4 h 和 4 i 的反应性最高（在 2 个大气压下的周转频率（TOF）分别为 95 和 97 h(-1)），而对于最佳手性诱导，则需要适当的底物/催化剂匹配。尽管观察到每个循环约 20%的 TOF 下降，但在 ee（95-96%）没有损失的情况下，前一种催化剂已回收 10 次。还通过分离和氢化催化剂-底物配合物来估算自支撑催化剂 4 e 中的有效催化位，结果表明，在自支撑催化剂 4 e 中，约 37%的 Rh(I)中心可用于催化中的底物 5 c。开发了一种使用活性 C/4 h 混合物作为固定相催化剂的连续流反应系统，用于 5 b 的不对称氢化，总运行时间为 144 小时，转化率大于 99%，对映选择性为 96-97%。产物溶液中 Rh 的总浸出量为原始催化剂 4 h 的 1.7%。
