Tf2O/DMSO-Promoted P–O and P–S Bond Formation: A Scalable Synthesis of Multifarious Organophosphinates and Thiophosphates

DMSO-Catalyzed Double P-O Bond or Double P-S Bond Formations of Phosphinic Acids

A DMSO-catalyzed double P-O bond or double P-S bond formation of phosphinic acid with an O- or S-containing nucleophile has been developed. Under metal-free and mild conditions, this simple procedure provides a compatible and rapid access to a variety of phosphonates and dithiophosphates. The DFT calculation of stabilization energy (SE) and the mechanism studies demonstrated that the "just right" Lewis base property and the relatively "soft" interaction strength with the phosphenium-dication ensure the unique catalytic activity of DMSO in this transformation.

NaIO4/air-initiated phosphorylation of alcohols with H-phosphine oxides for the construction of P(O)-O bonds in water

A facile and efficient protocol for P(O)-O bond formation was discovered through NaIO4/air-initiated phosphorylation of alcohols with H-phosphine oxides in water. This reaction showed good functional group tolerance and a broad substrate scope, providing an alternative method for constructing P(O)-O bonds. Mechanistic studies suggested that a phosphoryl radical-involving process from H-phosphine oxides facilitated the phosphorylation of alcohols under air.

Ligand-Free Iron-Catalyzed Construction of C-P Bonds via Phosphorylation of Alcohols: Synthesis of Phosphine Oxides and Phosphine Compounds

An efficient method for the construction of C-P(V) and C-P(III) bonds via the iron-catalyzed phosphorylation of alcohols under ligand-free conditions is disclosed. This strategy represents a straightforward process to prepare a series of phosphine oxides and phosphine compounds in good to excellent yields from the readily available alcohols and P-H compounds. A plausible mechanism is also proposed. We anticipate that this mode of transforming simple alcohols would apply in chemical synthesis widely.

Tf2O-Mediated P(O)-N Bond Formation of Either P(O)-OH or P(O)-H Reagents with Multitype Amines

We have developed a Tf2O-mediated approach for the direct amination of either P(O)-OH or P(O)-H reagents with a variety of aliphatic or aromatic amines. Without the requirement of precious metals and toxic reagents, this protocol provides an alternative route to various phosphinamides and phosphoramides. The reaction proceeds under simple and mild conditions and can be effectively scaled up with similar efficiency.

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.

Photocatalyzed Aerobic Cross-Dehydrogenative Coupling of Diarylphosphine Oxides with Alcohols and Phenols

A photocatalytic cross-dehydrogenative coupling of diarylphosphine oxides with alcohols and phenols has been developed. Using organic dye Rose Bengal as the photocatalyst and air as the oxidant, the reaction proceeded smoothly at room temperature. Both alcohols and phenols were feasible, affording various organophosphinates in high yields. The absence of a halogenating reagent, the absence of a transition-metal catalyst, a green oxidant, and mild conditions make this strategy environmentally benign and sustainable. Mechanistic studies indicated that the reaction is enabled by the cooperation of photoredox catalysis and photosensitization.

Lewis-acid-catalyzed phosphorylation of alcohols

An efficient method has been developed for reacting dialkyl H-phosphonates or diarylphosphine oxides with alcohols for constructing C-P bonds. This reaction was catalyzed by Lewis acid and involved nucleophilic substitution. A series of diphenylphosphonates and diphenylphosphine oxides were obtained, from the phosphorylation of alcohols, with good-to-excellent yields.

Cu(II)-Mediated direct 18F-dehydrofluorination of phosphine oxides in high molar activity

BACKGROUND

The 18F/19F-isotope exchange method employing P(V)-centered prosthetic groups demonstrates advantages in addressing mild one-step aqueous 18F-labeling of peptides and proteins. However, the molar activity (Am) achieved through isotope exchange remains relatively low, unless employing a high initial activity of [18F]F-. To overcome this drawback, our work introduces a novel approach through a Cu-mediated direct 18F-dehydrofluorination of phosphine oxides. This method leverages the straightforward separation of the 18F-labeled product from the phosphine oxide precursors, aiming to primarily increase Am.

RESULTS

Through a 19F-dehydrofluorination efficiency test, Cu(OAc)2 was identified as the optimal oxidative metal salt, exhibiting a remarkable 100% conversion within one hour. Leveraging the straightforward separation of phosphine oxide precursors and phosphinic fluoride products, the Am of an activated ester, [18F]4, sees an impressive nearly 15-fold increase compared to the 18F/19F-isotope exchange, with the same initial activity of [18F]F-. Furthermore, this Cu(II)-mediated 18F-dehydrofluorination approach demonstrates tolerance up to 20% solvent water content, which enables the practical radiosynthesis of 18F-labeled water-soluble molecules under non-drying conditions.

CONCLUSIONS

The direct 18F-dehydrofluorination of phosphine oxide prosthetic groups has been successfully accomplished, achieving a high Am via Cu(II)-mediated oxidative addition and reductive elimination.

Low-Valent-Tungsten-Catalyzed Aerobic Oxidative Cross-Dehydrogenative Coupling Reaction

A straightforward and convenient protocol was established for the synthesis of thiophosphates and 3-sulfenylated indoles via low-valent-tungsten-catalyzed aerobic oxidative cross-dehydrogenative coupling reactions. These reactions occur under mild conditions and simple operations with commercially available starting materials, processing the advantage of excellent atom and step economy, broad substrate scope, and good functional groups tolerance. Moreover, this transformation could be practiced on the gram scale, which exhibits great potential in the preparation of drug-derived or bioactive molecules.

Photochemical halogen-bonding assisted carbothiophosphorylation reactions of alkenyl and 1,3-dienyl bromides

Herein, we present a synthetic procedure for the facile and general preparation of novel S-alkenyl and dienyl phosphoro(di)thioates for the first time. Extensive mechanistic investigations support that the reactions rely on a photochemical excitation of a halogen-bonding complex, formed with a phosphorothioate salt and an alkenyl or dienyl bromide, which light-induced fragmentation leads to the formation of the desired products through a radical-based pathway. The substrate scope is broad and exhibits a wide functional group tolerance in the formation of the final compounds, including molecules derived from natural products, all with unknown and potentially interesting biological properties. Eventually, a very efficient continuous flow protocol was developed for the upscale of these reactions.

Tf2O/DMSO-mediated dual activation of aryl phosphinate to access various aryl phosphonates

A metal-free method for the dual activation of aryl phosphinate has been developed; the P-H and P-O bonds are sequentially activated by the Tf2O/DMSO system. Without the requirement of metals and unstable P-reagents, this one-pot procedure provides a convenient and practical access to a variety of aryl phosphonates. A mechanism involving twice generation of electrophilic P-species and two SN-processes is proposed on the basis of the control experiments.

Metal-Free S-Arylation of Phosphorothioate Diesters and Related Compounds with Diaryliodonium Salts

We developed a direct metal-free S-arylation of phosphorothioate diesters using diaryliodonium salts. The method allows for the preparation under simple conditions of a broad range of S-aryl phosphorothioates, including complex molecules (e.g., dinucleotide or TADDOL derivatives), as well as other related organophosphorus compounds arylated at a chalcogen. The reaction proceeds with a full retention of the stereogenic center at the phosphorus atom, opening convenient access to P-chiral products. The mechanism of the reaction was established using DFT calculations.

Visible-Light Mediated Arbuzov-Like Reaction with Thiophenols

We hereby disclose, a visible light mediated addition of sulfenyl radicals to trialkyl phosphites to access functionalized phosphorothioates. The use of cheap and readily available Eosin Y as a photocatalyst under mild energy efficient conditions bypassing the use of external oxidants forms the chief highlight of the work. The protocol is scalable and mechanistic studies indicate that the reaction proceeds through an ionic-Arbuzov like pathway from phosphoranyl radicals.

Blue LED-Promoted Syntheses of Phosphorothioates and Phosphorodithioates

An environmentally friendly and resourceful modular protocol for the synthesis of phosphorochalcogenoates, phosphorochalcogenothioates, and phosphinothioates under blue light-emitting diode irradiation is described. The blue LED-promoted P-S, P-Se, and P-Te bond constructions occurred under metal-free, ligand-free, oxidant-free, and photocatalyst-free conditions with minimum chemical waste generation and high atom economy providing the resulting phosphorochalcogenoates, phosphorochalcogenothioates, and phosphinothioates in good to excellent yields.

Bisphosphorylation of anhydrides - convenient access to bisphosphonates with a P-O-C-P motif

A novel strategy of bisphosphorylation of anhydrides with P(O)-H reagents via a DMAP-catalyzed and DBU-promoted process has been developed. These one-step transformations proceed efficiently to provide convenient access to a variety of P-O-C-P motif containing organophosphorus compounds. In addition, the gram-scale synthesis and the efficient recovery of the by-product highlight the sustainability and applicability of this method.

Copper and Photocatalytic Radical Relay Enabling Fluoroalkylphosphorothiolation of Alkenes: Modular Synthesis of Fluorine-Containing S-Alkyl Phosphorothioates and Phosphorodithioates

A photoredox and copper-catalyzed fluoroalkylphosphorothiolation of activated and unactivated alkenes via a radical relay mechanism is reported. By employing fluoroalkyl halides as radical precursors and P(O)SH or P(S)SH compounds as coupling partners, a wide range of β-monofluoroalkyl-, -difluoroalkyl-, -trifluoromethyl-, or -perfluoroalkyl-substituted S-alkyl phosphorothioates and phosphorodithioates can be easily constructed under mild conditions with good functional group tolerance. Furthermore, this modular reaction system can be successfully applied to late-stage functionalization of bioactive molecules.

Photoinduced Decarboxylative Phosphorothiolation of N-Hydroxyphthalimide Esters

A visible-light-induced protocol for the synthesis of phosphorothioates is developed by employing the Ir-catalyzed decarboxylative phosphorothiolation of N-hydroxyphthalimide esters. This novel synthesis method utilizes carboxylic acids as raw material, which is stable, cheap, and commercially available. Scope studies show that this reaction has good compatibility of functional groups. Notably, both the synthesis of steric hindrance phosphorothioates and the later modification of some bioactive compounds are successfully achieved.

Copper-Catalyzed Multicomponent Trifluoromethylphosphorothiolation of Alkenes: Access to CF3-Containing Alkyl Phosphorothioates

An unprecedented copper-catalyzed multicomponent radical-based reaction involving alkenes, P(O)H compounds, sulfur powder, and Togni reagent II at room temperature has been developed. A variety of highly functionalized CF₃-containing S-alkyl phosphorothioates can be directly prepared from a wide range of activated and unactivated alkenes. Moreover, this protocol highlights its potential in the late-stage functionalization of complex molecules and opens up a new avenue for the construction of C(sp³)-S-P bonds.

Tunable synthesis of chalcophosphinic amides and tertiary phosphinates using tert-butyl N,N-dialkylperoxyamidate

The tunable amidation and esterification of phosphine chalcoxide have been developed, in which tert-butyl N,N-dialkylperoxyamidate plays a dual role as a secondary amine and a tertiary alcohol precursor.