Iridium-catalyzed hydrogenation of β-dehydroamino acid derivatives using monodentate phosphoramidites

Abstract

The iridium-catalyzed asymmetric hydrogenation of 13 different β-dehydroamino acid derivatives to give optically active β-amino acid esters has been examined. Readily accessible monodentate octahydrobinaphthol- based phosphoramidites were used as chiral ligands. Good to excellent enantioselectivities and yields were obtained for the E isomers, whereas poorer catalyst performance was found for the Z isomers. Importantly, to obtain high enantioselectivity, substitution at the 3,3′-positions of the ligands was necessary. Enantioselectivities of up to 94% ee were achieved under optimized conditions. © Wiley-VCH Verlag GmbH & Co. KGaA, 2008.