Synthesis Of Chiral Monophosphite Ligands And Their Applications In Asymmetric Hydrogenation

Synthesis of a series of monophosphite ligands derived from carbohydrates and H8-BIN0L and their applications in the Rh-catalyzed asymmetric hydrogenation of α-dehydroamino acid ester, enamides and dimethyl itaconate and synthesis of β2 -amino acid by asymmetric hydrogenation constitutes the paper.1. Synthesis of monophosphite ligands and application of these ligands in the Rh-catalyzed asymmetric hydrogenation1) Six monodentate phosphite ligands derived from D-fructose, D-glucose, D-mannitol and H8-BINOL have been synthesized. Their structures fully were characterized by NMR and HRMS.2) Application of new developed monophosphite ligands in Rh-catalyzed asymmetric hydrogenation of functioned olefins such as α-dehydroamio acids methyl ester, enamides and dimethyl itaconate were investigated. Total conversions and excess 99.0%ee were obtained in Rh-catalyzed asymmetric hydrogenation of enamides and dimethyl itaconate. Only 90.6%ee has been achieved in Rh-catalyzed asymmetric hydrogenation of α-dehydroamino acid methyl ester.2. Synthesis of β2-amino acid by asymmetric hydrongenation 3-Substitution-2-(phthalidomethyl)-acrylic acid methyl ester and 2-(phthalido-methyl)-acrylic acid ethyl ester can be easily synthesized from commerciallyavailable acrylate ester and aldehydes in three steps.2-(Phthalido-methyl)-acrylic acid ethyl ester was chosen as a model substrate, the reaction conditions such as the solvents, hydrogen pressure, were investigated in details. Up to 99.1%ee has been achieved with 1.0 mol% Rh-ManniPhos complex under the optimized condition (in dichloromethane at room temperature under 1.01 MPa of hydrogen ). but the catalyst was not efficient for asymmetric hydrogenation of 3-substitution-2-(phthalidomethyl)-acrylic acid methyl ester.