A series of Ru(II) catalysts were prepared and tested in the asymmetric transfer hydrogenation of ketones. The catalyst containing a "4-carbon" tether gave the fastest rates of ketone reduction. This is due to both increased rate of regeneration of hydride "Ru-H" and increased rate of ketone reduction. Several classes of ketone were reduced in enantiomeric excesses of up to 97%. Substituents on the arene ring of the catalyst influence the reaction rate and enantioselectivity.
A series of kinetic and structural investigations on ruthenium-based catalysts for asymmetric transfer hydrogenation (ATH) of ketones are reported. A method is reported for monitoring the formation of ruthenium hydride species in real time using 1 H NMR spectroscopy.10
[reaction: see text] We have developed an efficient method for the preparation of medium- and large-sized nitrogen heterocycles via copper-catalyzed intramolecular N-arylation of phosphoramidates and carbamates. Introduction of the phosphoryl group or tert-butoxycarbonyl at N-termini can improve intramolecular cyclization under copper catalysis, and the phosphoryl and tert-butoxycarbonyl can easily be removed under the mild conditions; thus, the convenient and efficient method is suitable for the preparation of medium- and large-sized nitrogen heterocycles.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.