A new family of air- and moisture-stable phosphine-phosphoramidite ligands (PEAPhos) has been prepared from commercially available and inexpensive (S)-alpha-phenylethylamine through a two- or three-step transformation and successfully applied in the rhodium-catalyzed enantioselective hydrogenations of a variety of substrates, in which up to 99.9% ee was obtained for all of these kinds of substrates.
[reaction: see text] A new family of unsymmetrical ferrocenylethylamine-derived monophosphoramidites were synthesized and successfully applied in the Rh-catalyzed enantioselective hydrogenation of a range of enamides and alpha-dehydroamino acid esters, and ee values of up to 99.5% were obtained for both types of substrate. These results suggest that unsymmetrical amine-derived monophosphoramidites can also exhibit excellent enantioselectivity for a broad range of substrates, comparable to or higher than those of the most efficient symmetrical amine-derived monophosphoramidites reported thus far.
A series of chiral beta-aryl-substituted gamma-amino butyric acid derivatives were synthesized in good enantioselectivities via the Cu-catalyzed asymmetric conjugate reduction of gamma-phthalimido-alpha,beta-unsaturated carboxylic acid esters using Cu(OAc)2 x H2O as a catalyst precursor, (S)-BINAP as a ligand, PMHS as a hydride source, and t-BuOH as an additive. The methodology has been applied successfully to the enantioselective synthesis of a chiral pharmaceutical, (R)-baclofen.
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