Efficient Palladium Catalysts Containing Original Imidazolium-Tagged Chiral Diamidophosphite Ligands for Asymmetric Allylic Substitutions in Neat Ionic Liquid

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.

Diamidophosphites from β-hydroxyamides: readily assembled ligands for Pd-catalyzed asymmetric allylic substitution

Novel diamidophosphites based on β-hydroxyamides were prepared, and their individual and in situ formed complexes were tested in Pd-mediated allylations.

Novel Chiral Ligands for Palladium-catalyzed Asymmetric Allylic Alkylation/ Asymmetric Tsuji-Trost Reaction: A Review

Background:

Asymmetric catalysis holds a prestigious role in organic syntheses since a long time and chiral inductors such as ligands have been used to achieve the utmost desired results at this pitch. The asymmetric version of Tsuji-Trost allylation has played a crucial role in enantioselective synthesis. Various chiral ligands have been known for Pdcatalyzed Asymmetric Allylic Alkylation (AAA) reactions and exhibited excellent catalytic potential. The use of chiral ligands as asymmetric inductors has widened the scope of Tsuji-Trost allylic alkylation reactions.

Conclusion:

Therefore, in this review article, a variety of chiral inductors or ligands have been focused for palladium catalyzed asymmetric allylic alkylation (Tsuji-Trost allylation) and in this regard, recently reported literature (2013-2017) has been described. The use of ligands causes the induction of enantiodiscrimination to the allylated products, therefore, the syntheses of various kinds of ligands have been targeted by many research groups to employ in Pd-catalyzed AAA reactions.

Mechanistic insights into the tropo-inversion of the biphenyl moiety in chiral bis-amido phosphites and in their palladium(ii) complexes

Chiral bis-amido phosphites L1 and L2 containing a diaminobiphenyl unit and a chiral alkoxy group derived from either (-)-menthol or 3-acetoxy deoxycholic methyl ester have been synthesised. Both L1 and L2 react with PdCl₂(NCPh)₂ affording di- or mononuclear derivatives with formula trans-[Pd(μ-Cl)Cl(L)]₂ (1a, L = L1; 1b, L = L2) or trans-PdCl₂(L)₂ (2a, L = L1; 2b, L = L2) depending on the Pd : L molar ratio. The crystal structure of (M,P)-1a confirms the trans arrangement of the ligand L1 and shows an unusual puckering of the Pd₂(μ-Cl)₂ core (θ 46°). Both the ligands L1 and L2 and their complexes (1 and 2) are fluxional in solution as a consequence of the tropo-inversion of the diaminobiphenyl unit. For L1, L2, 1a and 2a a combined study including variable temperature ³¹P{¹H} NMR spectroscopy and line shape analysis, Eyring plots and DFT calculations have shed light on the mechanism of the tropo-inversion.

Recyclable imidazolium ion-tagged nickel catalyst for microwave-assisted C–S cross-coupling in water using sulfonyl hydrazide as the sulfur source

Recyclable nickel(ii) catalyst promoted sulfenylation of aryl halides with sulfonyl hydrazides in water using microwave irradiation under mild conditions is reported.

A protic ionic liquid as an atom economical solution for palladium catalyzed asymmetric allylic alkylation

A recyclable palladium catalyst for asymmetric allylic alkylation that generates its own ionic liquid solvent.

Ionic liquids in catalysis: molecular and nanometric metal systems

The catalyst immobilization in a liquid phase represents an attractive means to preserve high activities and selectivities, also permitting an easy recycling. To attain this goal, organic products should be extracted in a simple way from the catalytic phase leading to metal-free target compounds; for this reason, ionic liquids exhibiting high affinity for metallic species and low affinity for low polar compounds, turn into a promising medium, in particular for the synthesis of fine chemicals. In the present Accounts, we illustrate this approach through our research involving both molecular organometallic compounds and metallic nanoparticles dispersed in an ionic liquid phase.

Charge-tagged ligands: useful tools for immobilising complexes and detecting reaction species during catalysis

A critical overview is presented on the use of charged tagged ligands (CTLs) as immobilising agents in organometallic catalysis and as probes for studying mechanisms through electrospray ionisation mass spectrometry (ESI-MS) based on the most recent literature.

In recent years, charge-tagged ligands (CTLs) have become valuable tools in organometallic catalysis. Insertion of an ionic side chain into the molecular skeleton of a known ligand has become a useful protocol for anchoring ligands, and consequently catalysts, in polar and ionic liquid phases. In addition, the insertion of a cationic moiety into a ligand is a powerful tool that can be used to detect reaction intermediates in organometallic catalysis through electrospray ionisation mass spectrometry (ESI-MS) experiments. The insertion of an ionic tag ensures the charge in the intermediates independently of the ESI-MS. For this reason, these ligands have been used as ionic probes in mechanistic studies for several catalytic reactions. Here, we summarise selected examples on the use of CTLs as immobilising agents in organometallic catalysis and as probes for studying mechanisms through ESI-MS.