Preparation of Secondary Phosphine Oxide Ligands through Nucleophilic Attack on Imines and Their Applications in Palladium‐Catalyzed Catellani Reactions

Abstract

Several new amino-type secondary phosphine oxide (SPO) pre-ligands (3a-3h) that contain P-N bonds were synthesized and characterized. SPOs 3a-3h can tautomerize to phosphinous acids (PA, 3a-3h) as genuine ligands. The formation of SPOs 3a-3h occurred first through nucleophilic attack on the imine carbon atom, then by the addition of RPCl 2 (R = Ph, Cy, tBu, or iPr), and work-up under acidic conditions. The P-N bond in the newly prepared SPOs is evident from the crystal structures of SPOs 3d and 3h. Reactions of SPOs 3f, 3g, or 3h with Pd(COD)Cl 2 (COD = cyclooctadiene) yielded palladium complexes 6f, 6g, or 6h. In these crystal structures, PAs 3f, 3g, and

Synthesis of Pd-NNP Phosphoryl Mononuclear and Phosphinous Acid-Phosphoryl-Bridged Dinuclear Complexes and Ambient Light-Promoted Oxygenation of Benzyl Ligands

“…36,39,40 Bidentate NP(O)H preligands also form quasi-chelate structures. 18,43 Phosphoryl complexes without intramolecular hydrogen bonding were formed as transient intermediates in transition metal-catalyzed reactions using SPOs as substrates. 44,45 Structurally defined Au 11 clusters with monodentate phosphoryl ligands were also reported.…”

“…Thus, taking advantage of these stable structures as pseudo-bidentate ligands, several catalytic reactions have been developed. ,,,,,,,,− In contrast, monodentate PA or phosphoryl ligand-coordinated complexes without the formation of quasi-chelate structures are relatively rare. Bulky SPO preligands tend to afford PA complexes, ,,− although these preligands can also furnish quasi-chelate structures. ,, Bidentate NP­(O)H preligands also form quasi-chelate structures. , Phosphoryl complexes without intramolecular hydrogen bonding were formed as transient intermediates in transition metal-catalyzed reactions using SPOs as substrates. , Structurally defined Au 11 clusters with monodentate phosphoryl ligands were also reported . To utilize the cooperative effects of the PA ligand (or phosphoryl ligand) and the transition metal in catalysis, such as oxygenation shown in Scheme , SPO preligands that do not form strong intramolecular hydrogen bonding are required.…”