Rhodium-catalyzed triarylphosphine synthesis via cross-coupling of aryl iodides and acylphosphines

Alkylation Triggered an Acylation of Arenes with a Highly Electrophilic Acylphosphonium Salt

Friedel-Crafts acylation is usually promoted by Lewis acids or Brønsted acids. In this work, a novel acylation of arenes with a highly electrophilic acylphosphonium salt was developed. The alkylation of the phosphorus atom in acylphosphines generated a neutral trivalent phosphine as a good leaving group and triggered the high electrophilicity of the acylphosphonium salt. Using acylphosphonium salts, 38 examples of acylations of arenes, alcohols, phenol, amines, thioalcohols, and even polystyrene were achieved. The acylation of arenes was monitored by 31P nuclear magnetic resonance and disclosed the existence of an acylphosphonium intermediate. The electrophilic capability of the acylphosphonium salt was ranked by the following series of controlled reactions: AcPR+ ≈ AcOTf > AcI > AcCl.

Nickel-catalysed diversification of phosphine ligands by formal substitution at phosphorus

We report a diversification strategy that enables the direct substituent exchange of tertiary phosphines. Alkylated phosphonium salts, prepared by standard alkylation of phosphines, are selectively dearylated in a nickel-catalysed process to access alkylphosphine products via a formal substitution at the phosphorus center. The reaction can be used to introduce a wide range of alkyl substituents into both mono- and bisphosphines. We also show that the alkylation and dearylation steps can be conducted in a one-pot sequence, enabling accelerated access to derivatives of the parent ligand. The phosphine products of the reaction are converted in situ to air-stable borane adducts for isolation, and versatile derivatisation reactions of these adducts are demonstrated.

Phosphine substituents can be exchanged by standard alkylation of a phosphine and a subsequent dearylation of the resulting phosphonium salt. A wide variety of alkyl groups can be introduced into both mono- and bidentate ligands using this method.

Synthesis of triarylphosphines from arylammonium salts via one-pot transition-metal-free C-P coupling

A nucleophilic aromatic substitution (S_NAr) reaction that allowed transition-metal-free C-P bond construction via C-N bond cleavage was developed. The coupling between aryltrimethylammonium salts and secondary phosphines from the in situ reduction of diarylphosphine oxides led to the formation of diverse triarylphosphines with various functional groups. This one-pot process was not only a pertinent S_NAr precedent but also a favorable transition-metal-free alternative for C-P coupling.

Palladium-Catalyzed C-P(III) Bond Formation by Coupling ArBr/ArOTf with Acylphosphines

Palladium-catalyzed C-P bond formation reaction of ArBr/ArOTf using acylphosphines as differential phosphination reagents is reported. The acylphosphines show practicable reactivity with ArBr and ArOTf as the phosphination reagents, though they are inert to the air and moisture. The reaction affords trivalent phosphines directly in good yields with a broad substrate scope and functional group tolerance. This reaction discloses the acylphosphines' capability as new phosphorus sources for the direct synthesis of trivalent phosphines.