Modular POP Ligands in Rhodium-Mediated Asymmetric Hydrogenation: A Comparative Catalysis Study

Access to α-Aminophosphonic Acid Derivatives and Phosphonopeptides by [Rh(P-OP)]-Catalyzed Stereoselective Hydrogenation

The hydrogenation of N-substituted vinylphosphonates using rhodium complexes derived from P-OP ligands L1, ent-L1, or (R,R)-Me-DuPHOS as catalysts has been successfully accomplished, achieving very high levels of stereoselectivity (up to 99% ee or de). The described synthetic strategy allowed for the efficient preparation of α-aminophosphonic acid derivatives and phosphonopeptides, which are valuable building blocks for the preparation of biologically relevant molecules.

Efficient modular phosphorus-containing ligands for stereoselective catalysis

Over several years, our research team has contributed to ligand design for metal-catalyzed stereoselective transformations. This has been achieved with the synthesis and application to organic transformations of interest of an array of structurally diverse P-containing ligands. These range from highly modular enantiopure phosphine–phosphite ligands to supramolecularly regulated enantioselective phosphorus-based catalysts. Our research in supramolecular interactions has also led to the discovery of an unprecedented halogen-bonded rhodium-catalyst.

Features and Application in Asymmetric Catalysis of Chiral Phosphine-Phosphite Ligands

Chiral phosphine-phosphites are a class of ligands for asymmetric catalysis characterized by two coordinating functionalities with different electronic properties. These ligands also possess a highly modular structure and, due to versatile synthetic processes, they can be tuned precisely in the catalyst optimization process. Research regarding the application of these ligands in several enantioselective catalytic processes has provided outstanding results in a good number of them. These processes include not only Rh catalyzed reactions, such as olefin hydrogenation and hydroformylation, but also other reactions, such as hydrogenation of olefins and imines by Ru complexes, of imines and N-heterocycles by Ir derivatives, allyl alkylation or conjugate addition by Cu catalysts, or hydrocyanation of olefins by Ni ones. Overall, the use of these ligands has led to the preparation of a wide variety of chiral building blocks with high enantiomeric excess. Therefore, phosphine-phosphites have become in an important class of ligands in asymmetric catalysis.

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).

Modular solid-phase synthesis, catalytic application and efficient recycling of supported phosphine–phosphite ligand libraries

A highly modular solid-phase synthetic approach is presented which provides facile access to libraries of recyclable phosphine–phosphite ligands in quantitative yield requiring only minimal work-up.

Hydrogenative Kinetic Resolution of Vinyl Sulfoxides

Enantiopure sulfoxides are valuable precursors of organosulfur compounds with broad application in organic and pharmaceutical chemistry. An unprecedented strategy for obtaining highly enantioenriched sulfoxides based on a hydrogenative kinetic resolution using Rh-complexes of phosphine-phosphite ligands as catalysts is reported. After optimization, highly efficient conditions for the kinetic resolution of racemic sulfoxides have been identified. This methodology has been applied to a set of racemic aralkyl or aryl vinyl sulfoxides and allowed the isolation of both recovered and reduced products in excellent yields and enantioselectivities (up to 99% and 97% ee, respectively; 16 examples).

Preparation of highly substituted (β-acylamino)acrylates via iron-catalyzed alkoxycarbonylation of N-vinylacetamides with carbazates

A simple and efficient iron-catalyst system was applied for the synthesis of various (β-acylamino)acrylate derivatives under mild reaction conditions.

Highly enantioselective Rh-catalysed hydrogenation of 1-alkyl vinyl esters using phosphine-phosphoramidite ligands

MatPhos, a good mate for hard tasks: The asymmetric hydrogenation of 1-alkyl vinyl esters, thwarted so far by mediocre ee values and low activities, can now be achieved with MatPhos/Rh catalysts with ee values of 96-99% for a variety of substrates at low catalyst loadings (0.1-1 mol %) and under mild conditions (5-20 bar H2, room temperature). After hydrolysis, the corresponding chiral secondary alkyl alcohols can be obtained in high enantiopurities providing a general and practical route to this important product class.

Rhodium-catalysed asymmetric hydrogenation as a valuable synthetic tool for the preparation of chiral drugs

During the last few decades, rhodium-catalysed asymmetric hydrogenation of diverse alkene classes has emerged as a powerful synthetic tool in the pharmaceutical industry, contributing to the manufacturing of chiral drugs, recent drug candidates for clinical trials, and major synthetic precursors of drugs. Numerous efficient chiral rhodium complexes, most of which are derived from enantiopure phosphorus ligands, have been employed for the preparation of chiral drugs and intermediates thereof. This review article is intended to provide an updated overview of the most striking contributions in this field, organised according to substrate class: acrylate derivatives, itaconate derivatives, α-substituted enamides, α-arylenol acetates, and minimally functionalised olefins.