New Polymer‐Supported Catalysts for the Asymmetric Transfer Hydrogenation of Acetophenone in Water – Kinetic and Mechanistic Investigations

Heterogenization is a powerful approach for the generation of easily recyclable catalysts. In this study, a modified tethered rhodium(III)‐ p‐toluenesulfonyl‐1,2‐diphenylethylenediamine (Rh‐TsDPEN) complex immobilized on polymeric supports was applied to kinetic and up‐scaling experiments on the asymmetric transfer hydrogenation of acetophenone in water. Study of the catalyst has helped in understanding some aspects of its operating mode. The results indicate that, in the investigated range, a simple second‐order model describes the enantioselective conversion of acetophenone to phenylethanol. Optimal reaction conditions were determined, and particularly the solution pH was found to play a decisive role for the activity and reusability of the catalyst. The good performance under optimized conditions emphasizes the practical usefulness of this recyclable catalytic system for environmentally benign asymmetric transfer hydrogenation processes.     

Chirally Modified Platinum Nanoparticles Stabilized by Dendritic Core‐Multishell Architectures for the Asymmetric Hydrogenation of Ethyl Pyruvate

In this paper we present the asymmetric hydrogenation of α‐keto esters with platinum nanoparticles homogeneously stabilized in dendritic core‐multishell architectures. The main focus lies on recycling and metal leaching, because little is reported so far about these aspects. It is shown that the stabilizing polymer allows for the efficient modification of the Pt surface with the chiral alkaloid cinchonidine, thereby inducing enantioselectivity and enhancing the reaction rate in the asymmetric hydrogenation of ethyl pyruvate. After optimization of the reaction conditions 63% ee for (R)‐ethyl lactate was obtained. During recycling it was found that this value could even be increased upon ultrafiltration of the catalyst prior to use. Recycling was accomplished for 10 cycles with stable activity and enantioselectivity (∼73% ee) in the first eight runs. Aggregation of the initially well dispersed nanoparticles was observed by transmission electron microscope (TEM) analysis, leading to reduced conversion after the 8^th cycle, but metal leaching into the product has been observed only in the very first run.     

Current trends in the involuntary civil commitment of mentally disabled persons.

Explores recent developments in involuntary civil commitment and the legal and psychosocial process whereby persons alleged to be mentally ill and dangerous are involuntarily hospitalized. Highlighted are current trends toward cooperation among lawyers and mental health professionals and toward an avoidance of formal procedures in commitment proceedings. It is concluded that psychologists need to assume a greater role in this process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)