Asymmetric Catalyzed Allylic Substitution Using a Pd/P–S Catalyst Library with Exceptional High Substrate and Nucleophile Versatility: DFT and Pd-π-allyl Key Intermediates Studies

Diverse “roof shaped” chiral diamidophosphites: palladium coordination and catalytic applications

“Roof shaped” chiral diamidophosphites of various structures and denticities were obtained and tested in Pd-catalyzed asymmetric allylic substitution.

Recent Advances in Enantioselective Pd-Catalyzed Allylic Substitution: From Design to Applications

This Review compiles the evolution, mechanistic understanding, and more recent advances in enantioselective Pd-catalyzed allylic substitution and decarboxylative and oxidative allylic substitutions. For each reaction, the catalytic data, as well as examples of their application to the synthesis of more complex molecules, are collected. Sections in which we discuss key mechanistic aspects for high selectivity and a comparison with other metals (with advantages and disadvantages) are also included. For Pd-catalyzed asymmetric allylic substitution, the catalytic data are grouped according to the type of nucleophile employed. Because of the prominent position of the use of stabilized carbon nucleophiles and heteronucleophiles, many chiral ligands have been developed. To better compare the results, they are presented grouped by ligand types. Pd-catalyzed asymmetric decarboxylative reactions are mainly promoted by PHOX or Trost ligands, which justifies organizing this section in chronological order. For asymmetric oxidative allylic substitution the results are grouped according to the type of nucleophile used.

Stereodivergent Pd/Cu catalysis: asymmetric alkylation of racemic symmetrical 1,3-diphenyl allyl acetates

A stereodivergent Pd/Cu catalyst system was developed, which was successfully applied to the asymmetric allylic alkylation of symmetrical 1,3-disubstituted allyl acetates with prochiral imino esters in a fully stereodivergent manner.

Evolution of phosphorus-thioether ligands for asymmetric catalysis

In the early 1990s chiral P-thiother ligands emerged as promising ligands in the field of asymmetric catalysis, with the development of many P-thioether ligand families. However, only a few of them have shown a broad reaction and substrate scope. So, compared with other heterodonor ligands such as the widely studied P-N ligands, their impact in asymmetric catalysis was not realised until recently. This has been mainly attributed to the difficulty of controlling the configuration at the sulfur atom when coordinated to the metal. More recently, it has been found that this problem could be solved by a rigorous choice of the ligand scaffold, a process usually aided by mechanistic studies. This allowed the recent discovery of new P-thioether ligand families with a broader versatility, both in reactions and in substrate/reagent scope. This feature article aims to highlight those new P-thioether ligand libraries and the relationship between the structure and catalytic performance.

A readily accessible and modular carbohydrate-derived thioether/selenoether-phosphite ligand library for Pd-catalyzed asymmetric allylic substitutions

A large library of thioether/selenoether-phosphite ligands have been tested in the Pd-catalyzed asymmetric allylic substitution reaction. The presented ligands are derived from cheap and available carbohydrates and they are air-stable solids and easy to handle. Their highly modular nature has made it possible to achieve excellent enantioselectivities in the substitution of a range of hindered and unhindered substrates (ees up to 99% and 91%, respectively). In addition, twelve C-, N- and O-nucleophiles can be efficiently introduced, independently of their nature. Among the whole library, ligands that contain an additional chiral centre in the alkyl backbone chain next to the phosphite group and an enantiopure biaryl phosphite group provided the best enantioselectivities. In general, there is a cooperative effect between these two chiral elements, and therefore, a matched combination between them is necessary to achieve the highest enantioselectivities. However, in the case of cyclic substrates, this cooperative effect is less pronounced and advantageously, both enantiomers of the product can be obtained by setting up the desired configuration of the biaryl phosphite group. Studies of the key Pd-π-allyl intermediates allowed us to better understand the enantioselectivities obtained experimentally.

Pd/Phosphoramidite Thioether Complex-Catalyzed Asymmetric N-Allylic Alkylation of Hydrazones with Allylic Acetates

A general and efficient Pd/phosphoramidite thioether complex-catalyzed asymmetric N-allylic alkylation of hydrazones with allylic acetates has been developed for the first time. The reaction allows for the preparation of various valuable N-substituted hydrazones with generally good yields and excellent enantioselectivities. Minor structural modification of the ligand resulted in opposite enantiomers, enabling enantiodivergent synthesis of products by the same catalytic system.