Palladium-Based Supramolecularly Regulated Catalysts for Asymmetric Allylic Substitutions

Abstract

ABSTRACT: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. ) led to positive effects in enantioselectivity (by up to 16% ee) for the allylic substitution reactions. These ligands coordinated in the usual cis-fashion or in an unprecedented transfashion to the palladium center, depending on the phosphite group, and presented different reactivity in the allylic substitutions.

Supramolecularly fine-regulated enantioselective catalysts

“…A low ee was obtained for benzylamine (BZA) as the nucleophile when no RAs were used (see entry 13 in Table 11). In contrast with the results observed with the Cnucleophile, 32 an improvement in the ee was observed by using group II or lanthanide triflates as RAs (see entry 14 in Table 11). In short, it has been described in this section how combinations of RAs and polyether based-ligands have been used to supramolecularly regulate the outcome of AHs, AHFs, asymmetric Henry reactions and AASs.…”

Recent developments in enantioselective lanthanide-catalyzed transformations

“…A range of excellent results were also published in the area of enantioselective lanthanide-catalyzed Scheme 64. Oxidation of sulfides catalyzed by Mn/Gd polymeric catalyst [104].…”

“…In 2016, Vidal-Ferran et al investigated the effect of lanthanide triflates as regulator agents, such as La(OTf) 3 and Ho (OTf) 3 , to enhance the catalytic properties of palladium complexes derived from chiral biphosphite ligands and [Pd(l-Cl) (g 3 -C 3 H 5 )] 2 in asymmetric allylic substitutions [104]. Indeed, the addition of 5.5 mol% of these lanthanide triflates led to positive effects on the enantioselectivity (by up to 16% ee) for the asymmetric allylic substitution of 1,3-diphenylallyl acetate 204 with a nitrogen nucleophile, such as benzylamine 135, to give the corresponding chiral amine 205.…”

Cofactor-Controlled Chirality of Tropoisomeric Ligand

“…To circumvent this problem, Ooi and co-workers used a ligand assembled from an achiral monodentate phosphine equipped with an ammonium group and chiral biphenolates or phosphates via electrostatic interactions (B, Figure ). An alternative approach, with more general applications, consists of the use of cofactor-controlled ligands containing a receptor unit capable of supramolecular interaction with a chiral anion (C, Figure ); such ligands have been developed by some of us and successfully applied in enantioselective catalysis . We anticipated that this strategy could be efficient for conformational control of bistropos ligands, which is demonstrated in studies presented here.…”