Homogeneous Ru-catalyzed hydrogenation of HMF delivers a high percentage of trans-THFDM rather than only cis-THFDM known from heterogeneous hydrogenation.
The Pd‐catalysed synthesis of sodium acrylate from ethylene and CO2 in the presence of alcoholate bases has been improved significantly. We used amide solvents such as N‐cyclohexylpyrrolidone or N,N‐dibutylformamide to achieve turnover numbers greater than 500 in one run, which is significantly higher than that of systems for this reaction reported previously. For the first time, we were able to recycle the catalyst without any additional regeneration step. With this system, it is possible to use the simple and easily recycled alcoholate base sodium isopropoxide to achieve good turnover numbers up to 200.
Several chiral sulfonyl compounds were prepared using the iridium catalyzed asymmetric hydrogenation reaction. Vinylic, allylic and homoallylic sulfone substitutions were investigated, and high enantioselectivity is maintained regardless of the location of the olefin with respect to the sulfone. Impressive stereoselectivity was obtained for dialkyl substitutions, which typically are challenging substrates in the hydrogenation. As expected, the more bulky Z-substrates were hydrogenated slower than the corresponding E isomers, and in slightly lower enantioselectivity.
Development of iridium-catalyzed asymmetric hydrogenation: New catalysts, new substrate scope.. The asymmetric hydrogenation of olefins is a tremendously powerful tool used to synthesize chiral molecules. The field was pioneered using rhodium--and ruthenium--based catalysts; however, catalysts based on both of these metals suffer from limitations, such as the need for directing substituents near or even adjacent to the olefin. Iridium--based catalysts do not suffer from this flaw and can thus hydrogenate a wide variety of olefins, including some tetra substituted ones. It is also possible for iridium--based catalysts to hydrogenate hetero--π bonds such as those found in hetero--aromatic rings. This review summarizes the contributions made to this field by our research group over the past few years. Keywords: Asymmetric catalysis, Iridium, Hydrogenation, Alkenes Graphical Abstract:
Journal of Organometallic Chemistry
Abstract:We demonstrate here the asymmetric hydrogenation of orthosubstituted pyridines using an N,Pligated iridium catalyst. To facilitate this reaction, aromaticity of the pyridines was weakened by forming Niminopyridium ylides. The reactions gave very high conversions, and after a single recrystallization, excellent ee was obtained (up to 98%). This methodology lends itself to the synthesis of chiral piperidine building blocks.
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.