312 resultados para ASYMMETRIC MICHAEL REACTIONS


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In this article, we describe an apparatus in our laboratory for investigating elementary chemical reactions using the high resolution time-of-flight Rydberg tagging method. In this apparatus, we have adopted a rotating source design so that collision energy can be changed for crossed beam studies of chemical reactions. Preliminary results on the HI photodissociation and the F atom reaction with H-2 are reported here. These results suggest that the experimental apparatus is potentially a powerful tool for investigating state-to-state dynamics of elementary chemical reactions. (c) 2005 American Institute of Physics.

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The low-cost and commercially available (-)-ephedrine hydrochloride was firstly employed in the [RuCl2(1)-cymene)](2)-catalyzed asymmetric transfer hydrogenation of prochiral ketones in water. The reaction could be performed in the open air at rt, affording excellent yields (up to 99%) and good enantioselectivities (up to 83% ee). It provided a further step toward the discovery of simplified catalyst systems for eventual availability. (c) 2005 Published by Elsevier Ltd.

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Reactions of selenium with imines ((RRC)-C-1=NR2) of aldehydes and ketones in the presence of carbon monoxide, water and triethylamine lead to reductive selenation, on aerobic work-up, to afford symmetrical diselenides ((RRCHSe)-C-1)(2) in good to excellent yields. The proposed mechanism suggests that both in situ generated carbonyl selenide (SeCO) and hydrogen selenide (H2Se) are involved in the reaction.

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A novel catalytic system for asymmetric hydrogenation of functionalized ketones has been developed using a Pd/bisphosphine complex as the catalyst in 2,2,2-trifluoroethanol. The reaction exhibits high enantioselectivity, and up to 92.2% ee was obtained.

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One asymmetric transformation reaction Of L-proline (L-Pro) to D-proline was studied by a home-made capillary array electrophoresis (CAE) for the first time. The aldehyde catalysts and the organic acid solvents for the asymmetric transformation reaction were rapidly screened and the enantiomeric excess values of the asymmetric product Of L-Pro were directly obtained from the electrophoretogram of CAE.