ABSTRACT
The iridium-catalyzed asymmetric hydrogenation of various di- and trisubstituted enol phosphinates has been studied. Excellent enantioselectivities (up to >99% ee) and full conversion were observed for a range of substrates with both aromatic and aliphatic side chains. Enol phosphinates are structural analogues of enol acetates, and the hydrogenated alkyl phosphinate products can easily be transformed into the corresponding alcohols with conservation of stereochemistry. We have also hydrogenated, in excellent ee, several purely alkyl-substituted enol phosphinates, producing chiral alcohols that are difficult to obtain highly enantioselectively from ketone hydrogenations.
Subject(s)
Iridium/chemistry , Nitrogen/chemistry , Organophosphorus Compounds/chemistry , Phosphinic Acids/chemistry , Phosphorus/chemistry , Catalysis , Hydrogenation , Ketones/chemistry , Ligands , Models, Chemical , StereoisomerismABSTRACT
The tracer-pulse method provides the real adsorption data points directly from simple, straightforward calculations and is therefore a superior method for multicomponent adsorption isotherm determination in HPLC. Only one important problem has restricted its use so far: the tracer peaks are invisible using any conventional detection principle. We present a solution to this problem with an approach with a firm base in analytical chemistry, utilizing stable isotopes and mass spectrometric detection. The new approach was used for the determination of binary adsorption isotherms, and a systematic investigation was made of its main sources of error. With this modification, the tracer method can be a prime choice for future characterizations of multicomponent separation systems and of competitive drug binding studies.
ABSTRACT
Herein we describe the synthesis of a new class of chiral phosphine-oxazolines and their application as ligands in iridium-catalyzed hydrogenations. Mechanistic aspects of olefin hydrogenation with this class of iridium catalysts are discussed and a selectivity model to help rationalize the results obtained is also presented.
Subject(s)
Alkenes/chemistry , Imines/chemistry , Iridium/chemistry , Oxazoles/chemistry , Phosphines/chemistry , Catalysis , Hydro-Lyases , Hydrogenation , Ligands , Molecular StructureABSTRACT
[reaction: see text] A new class of chiral phosphine-oxazoline ligands have been developed. Chiral Ir complexes prepared from these ligands induced high enantioselectivities (66-90% ee) when applied to the asymmetric hydrogenation of acyclic aromatic N-arylimines.
