Ligand‐Free Ultrasmall Recyclable Iridium(0) Nanoparticles for Regioselective Aromatic Hydrogenation of Phosphine Oxide Scaffolds: An Easy Access to New Phosphine Ligands

Abstract

Herein, we developed the recyclable ligand‐free iridium (Ir)‐hydride based Ir0 nanoparticles (NPs) for the first regioselective partial hydrogenation of PV‐substituted naphthalenes. Both the isolated and in situ generated NPs are catalytically active. A control nuclear magnetic resonance (NMR) study revealed the presence of metal‐surface‐bound hydrides, most likely formed from Ir0 species. A control NMR study confirmed that hexafluoroisopropanol as a solvent was accountable for substrate activation via hydrogen bonding. High‐resolution transmission electron microscopy of the catalyst supports the formation of ultrasmall NPs, and X‐ray photoelectron spectroscopy confirmed the dominance of Ir0 in the NPs. The catalytic activity of NPs is broad as showcased by highly regioselective aromatic ring reduction in various phosphine oxides or phosphonates. The study also showcased a novel pathway toward preparing bis(diphenylphosphino)‐5,5′,6,6′,7,7′,8,8′‐octahydro‐1,1′‐binaphthyl (H8‐BINAP) and its derivatives without losing enantioselectivity during catalytic events.

Access to C(sp3) borylated and silylated cyclic molecules: hydrogenation of corresponding arenes and heteroarenes

“…Other recent reports on saturating arenes and heteroarenes that do not bear boryl or silyl substituents include the work of Handa, who used [Ir(cod)Cl] 2 to hydrogenate phosphine oxide scaffolds with Ir nanoparticles being the active catalyst. 30 A cooperative heterogeneous and homogeneous strategy for asymmetric hydrogenations of arenes and heteroarenes has also been developed, which has been applied to a single borylated substrate (benzofuran). [31][32][33] The hydrogenation of uoropyridines using Pd(OH) 2 , in acidic media has also been reported.…”