Structural Investigations on Enantiopure POP Ligands: a High- Performing POP Ligand for Rhodium-catalysed Hydrogenations

A second generation of phosphine–phosphite (P–OP) ligands, incorporating a more sterically bulky phosphite group than previous P–OP ligand designs, gave very efficient catalysts for the Rh‐catalysed asymmetric hydrogenation of a diverse array of substrates (11 examples, 93–99 % ee) containing structurally diverse substituents and chelating groups at the C=C double bond. The presence of the sterically bulky (Sa)‐3,3′‐diphenyl‐5,5′,6,6′,7,7′,8,8′‐octahydro‐[1,1′‐binaphthalene]‐2,2′‐diol‐derived phosphite fragment caused significant increases in enantioselectivity (up to Δee = 58 %), and provided improved results compared to those obtained with the first generation of P–OP‐derived rhodium catalysts {i.e., rhodium complexes incorporating phosphine–phosphite ligands with (Ra)‐ and (Sa)‐BINOL‐derived phosphite groups; BINOL = [1,1′‐binaphthalene]‐2,2′‐diol}. Overall, the optimal ligand L8 provided very high enantioselectivities for a range of structurally diverse olefins (up to 99 % ee)

Palladium-Based Supramolecularly Regulated Catalysts for Asymmetric Allylic Substitutions

Herein is reported the effect of different polyether binders (alkali metal, alkaline earth metal, and lanthanide salts) as regulation agents to enhance the catalytic properties of palladium complexes derived from enantiopure bisphosphite ligands in allylic substitutions. The addition of RbOAc or M­(OTf)_<i>x</i> (M = Mg²⁺, La³⁺, or Ho³⁺) led to positive effects in enantioselectivity (by up to 16% ee) for the allylic substitution reactions. These ligands coordinated in the usual <i>cis</i>-fashion or in an unprecedented <i>trans</i>-fashion to the palladium center, depending on the phosphite group, and presented different reactivity in the allylic substitutions

Stereoselective Rh-Catalyzed Hydrogenative Desymmetrization of Achiral Substituted 1,4-Dienes

Highly efficient catalytic stereoselective hydrogenative desymmetrization reactions mediated by rhodium complexes derived from enantiopure phosphine–phosphite (P–OP) ligands are described. The highest performing ligand, which contains a TADDOL-derived phosphite fragment [TADDOL = (2,2-dimethyl-1,3-dioxolane-4,5-diyl)­bis­(diphenylmethanol)], presented excellent catalytic properties for the desymmetrization of a set of achiral 1,4-dienes, providing access to the selective formation of a variety of enantioenriched secondary and tertiary alcohols (six examples, up to 92% ee)

Small Bite-Angle P–OP Ligands for Asymmetric Hydroformylation and Hydrogenation

A series of small bite-angle phosphine-phosphite (P–OP) ligands have been synthesized by a two-step method. The key intermediate was prepared by an unprecedented asymmetric carbonyl reduction of a phosphamide using the CBS (Corey–Bakshi–Shibata) catalyst. The topology of these ligands (a configurationally stable stereogenic carbon with two heteroatom substituents) and their small bite-angle (created by the close proximity of the two ligating groups to the metal center) together provide a rigid asymmetric environment around this center, enabling high stereoselectivity in hydroformylations and hydrogenations of standard substrates

Small Bite-Angle P–OP Ligands for Asymmetric Hydroformylation and Hydrogenation

A series of small bite-angle phosphine-phosphite (P–OP) ligands have been synthesized by a two-step method. The key intermediate was prepared by an unprecedented asymmetric carbonyl reduction of a phosphamide using the CBS (Corey–Bakshi–Shibata) catalyst. The topology of these ligands (a configurationally stable stereogenic carbon with two heteroatom substituents) and their small bite-angle (created by the close proximity of the two ligating groups to the metal center) together provide a rigid asymmetric environment around this center, enabling high stereoselectivity in hydroformylations and hydrogenations of standard substrates