Highly Enantioselective Binaphthyl-Based Chiral Phosphoramidite Stabilized-Palladium Nanoparticles for Asymmetric Suzuki C–C Coupling Reactions

Abstract

The optically pure binaphthyl-based phosphoramidite ligands and their perfluorinated analogs have been first used for the preparation of chiral palladium nanoparticles (PdNPs). These PdNPs have been extensively characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, 31 P NMR, and thermogravimetric analysis techniques. The circular dichroism(CD) analysis of chiral PdNPs exhibited negative cotton effects. Perfluorinated phosphoramidite ligands provided smaller (2.32–3.45 nm) and well-defined nanoparticles, in comparison with the nonfluorinated analog (4.12 nm). The catalytic behavior of binaphthyl-based phosphoramidite stabilized chiral PdNPs has been investigated in the asymmetric Suzuki C–C coupling reactions for the formation of sterically hindered binaphthalene units, and high isolated yields (up to 85%) were achieved with excellent enantiomeric excesses (>99% ee). Recycling studies revealed that chiral PdNPs could be reused over 12 times without significant loss in activity and enantioselectivity (>99% ee). The nature of the active species was also investigated with a combination of poisoning and hot filtration tests and found that catalytically active species is the heterogeneous nanoparticles. These results indicate that the use of phosphoramidite ligands as a stabilizer for developing efficient and unique chiral nanoparticles could open up a field for many other asymmetric organic transformations promoted by chiral catalysts.

Cationic and Neutral PdII and PtII Pincer Complexes of Phosphinamino-Triazolyl-Pyridine [PN(H)N]: Pincer Ligand-Stabilized Palladium Nanoparticles and Their Catalytic Annulation of Internal Alkynes to Indenones

“…They also reported bisphosphine (C8-BINAP)-stabilized Pd nanoparticles, which exhibited good activities in Stille and Suzuki coupling reactions . Yilmaz and co-workers reported the utility of chiral Pd nanoparticles stabilized by binaphthyl-based phosphoramidite ligands and their perfluorinated analogues, in Suzuki coupling reactions, with the aid of 31 P NMR data . Also in this study, due to the partially soluble nature of the in situ -generated complex 2 nanoparticles ( Pd@2 ), useful information was obtained from the solution by 31 P NMR spectroscopy (Figure S66).…”

“…22 Yilmaz and co-workers reported the utility of chiral Pd nanoparticles stabilized by binaphthyl-based phosphoramidite ligands and their perfluorinated analogues, in Suzuki coupling reactions, with the aid of 31 P NMR data. 23 Also in this study, due to the partially soluble nature of the in situ-generated complex 2 nanoparticles (Pd@2), useful information was obtained from the solution by 31 P NMR spectroscopy (Figure S66). The Fourier transform infrared (FT-IR) spectra of 1, 2, and Pd@2 are compared in Figure S67.…”

“…22 Yilmaz and co-workers reported the utility of chiral Pd nanoparticles stabilized by binaphthyl-based phosphoramidite ligands and their perfluorinated analogues, in Suzuki coupling reactions. 23 Hyeon and co-workers have studied the coordination chemistry of palladium nanoparticles stabilized with various phosphine ligands. 21 In situ-generated palladium nanoparticles stabilized by phosphine ligands have shown excellent catalytic activity in organic synthesis.…”

“…The first optically active ( R )- and ( S )-BINAP-stabilized Pd nanoparticles were reported by Fujihara and co-workers, in which these chiral catalysts were used in the asymmetric hydrosilylation of styrene . Yilmaz and co-workers reported the utility of chiral Pd nanoparticles stabilized by binaphthyl-based phosphoramidite ligands and their perfluorinated analogues, in Suzuki coupling reactions . Hyeon and co-workers have studied the coordination chemistry of palladium nanoparticles stabilized with various phosphine ligands …”

Biomimetic Chiral Nanomaterials with Selective Catalysis Activity

“…In order to increase the chiral recognition, amino acids served as chiral selectors were coated on an inorganic metal NPs surface. [ 215 ] Inorganic metal NPs, such as Au NPs and Ce NPs, were prepared for the enantioselective catalysis oxidation of chiral DOPA. [ 216 , 217 ] Cys functionalized Au NPs were easily fabricated through the covalent bond between Au NPs and sulfhydryl group from Cys.…”