Recent Advances in C(sp3)—H Phosphorylation Based on Secondary Phosphine Oxides and Phosphite Esters

Electrochemical-induced phosphorylation of arenols and tyrosine containing oligopeptides

A disclosed technique employs electrochemical dehydrogenative cross-coupling to create organophosphates, utilizing phosphites compounds with arenols. Inorganic iodide salts serve dual roles as redox catalysts and electrolytes in an undivided cell, omitting the need for external oxidants or bases. Initial mechanistic investigations indicate the reaction unfolds via an electro-oxidative radical pathway, facilitating the formation of P-O bonds, leading to the generation of oxygen radicals in the formation of acetylaminophenol. This environmentally friendly approach offers excellent tolerance to various functional groups, achieves high yields (up to 95% isolated yield), and accommodates a wide range of substrates, showcasing its utility for practical synthesis applications.

Regioselective α-Phosphonylation of Unprotected Alicyclic Amines

Unprotected alicyclic amines undergo α-C-H bond phosphonylation via a two-stage one-pot process involving the oxidation of amine-derived lithium amides with simple ketone oxidants, generating transient imines which are then captured with phosphites or phosphine oxides. Amines with an existing α-substituent undergo regioselective α'-phosphonylation. Amine α-arylation and α'-phosphonylation can be combined, generating a difunctionalized product in a single operation.

Photoinduced Remote C(sp3)-H Phosphonylation of Amides

The present study reports an unprecedented protocol for the phosphonylation of unactivated C(sp3)-H bonds. By utilizing 1 mol % 4DPAIPN (1,2,3,5-tetrakis(diphenylamino)-4,6-dicyanobenzene) as the catalyst, satisfactory yields of γ-phosphonylated amides are obtained through a visible-light-induced reaction between N-((4-cyanobenzoyl)oxy)alkanamides and 9-fluorenyl o-phenylene phosphite at room temperature. This protocol demonstrates broad substrate scope and wide functional group compatibility.

TEMPO/PhI(OAc)2 promotes the α-aminophosphinoylation of alcohols with amines and H-phosphine oxides in aqueous medium

A novel method for synthesizing α-aminoalkyl phosphine oxides in aqueous medium, using Ar2P(O)-H reagents, alcohols and amines, is described. This method: (i) allows for the smooth aminophosphinoylation of alcohols with amines and H-phosphine oxides under mild conditions; (ii) provides an efficient and alternative approach to access various α-aminoalkylphosphine oxides. Although various amines exhibited remarkable versatility and tolerance for functional groups in this reaction, alcohols and H-phosphine oxides demonstrated limited applicability as reactants. Hence, further investigation using a wider range of substrates is crucial. The postulated mechanism indicated that the three-component reaction followed the imine pathway due to the in situ oxidation of alcohol to aldehyde.

Tuning the Photocatalytic Performance of Ruthenium(II) Polypyridine Complexes Via Ligand Modification for Visible-Light-Induced Phosphorylation of Tertiary Aliphatic Amines

Tuning the redox potential of commonly available photocatalyst to improve the catalytic performance or expand its scope for challenging synthetic conversions is an ongoing demand in synthetic chemistry. Herein, the excited state properties and redox potential of commercially available [Ru(bpy)₃ ]²⁺ photocatalyst were tuned by modifying the structure of the bipyridine ligands with electron-donating/withdrawing units. The visible-light-mediated photoredox phosphorylation of tertiary aliphatic amines was demonstrated under mild conditions. A series of cross-dehydrogenative coupling reactions were performed employing the Ru^II complexes as photocatalyst giving the corresponding α-aminophosphinoxides and α-aminophosphonates via carbon-phosphorus (C-P) bond formation.

Visible-Light-Promoted Phosphorylation/Cyclization of 1-Acryloyl-2-cyanoindoles in Green Solvent

A visible-light-induced persulfate-promoted cascade phosphorylation/cyclization reaction to access various phosphorylated pyrrolo[1,2-a]indolediones under mild conditions was developed. Notably, the transformation was carried out with diethyl carbonate/H₂O as a green medium at room temperature. More impressively, traditional metal catalysts and photocatalysts could be effectively avoided. The reactions are simple to operate, easy to scale up, and have good functional group tolerance.

Visible-Light-Induced α-C(sp3)-H Phosphinylation of Unactivated Ethers under Photocatalyst- and Additive-Free Conditions

A photocatalyst- and additive-free visible-light-induced α-C(sp³)-H phosphinylation of unactivated ethers involving a C-O bond cleavage with molecular oxygen as the sole oxidant at room temperature has been achieved. This method provides a sustainable access to α-hydroxyphosphine oxides in up to 88% yield with good functional group compatibility under mild and neutral conditions (34 examples). Moreover, the subsequent two-step conversion of the resulting dihydroxy diarylphosphine oxides afforded α-phosphinylated cyclic ethers in good overall yields (10 examples).

Direct phosphorylation of benzylic C-H bonds under transition metal-free conditions forming sp3C-P bonds

Direct phosphorylation of benzylic C-H bonds was achieved in a biphasic system under transition metal-free conditions. A selective radical/radical sp3C-H/P(O)-H cross coupling was proposed, and various substituted toluenes were applicable. The transformation provided a promising method for constructing sp3C-P bonds.