Copper-promoted oxidative-fluorination of arylphosphine under mild conditions

A Modular Three-Component Approach for Site-selective Tandem Arene Thiophosphorylation

Thiophosphates serve as pivotal reagents within the realms of both organic and inorganic synthesis, with their most notable applications observed in agricultural chemistry. This manuscript delineates a modular three-component synthetic strategy for site-selective arene C-H thiophosphorylation with thianthrenium salt, 1,4-diazabicyclo[2.2.2]octane-sulfur dioxide (DABSO), and diarylphosphine oxides as substrates. This approach facilitates the metal-free and green synthesis of a diverse spectrum of S-aryl phosphorothioates through C-H functionalization and late-stage modification showcasing practicality and broad applicability.

Development of SF6 as a Formal Electrophilic Fluorinating Reagent for Photocatalyzed Oxidative Fluorination of Phosphine Oxides

Organophosphorus-fluorine compounds are of significant utility across biology, pharmacy, and chemical synthesis. Here, we introduce a photocatalyzed oxidative-fluorination approach employing SF6 as a formal electrophilic fluorinating reagent. It offers an innovative pathway to forge P(O)-F bonds. Notably, sulfur hexafluoride plays a dual role as both the oxidant and the fluorinating reagent under mild conditions in this transformation. Meanwhile, this method contributes to environmental sustainability by consuming a notorious greenhouse gas, underscoring the ecological benefits of our approach.

Poison to Promise: The Resurgence of Organophosphorus Fluoride Chemistry

Organophosphorus(V) fluorides have a long and tumultuous history, with early applications as toxins and nerve agents reflecting their poisonous past. Behind these very real safety considerations, there is also growing potential in a wide range of fields, from chemical biology to drug development. The recent inclusion of organophosphorus(V) fluorides in click chemistry exemplifies the promise these compounds possess and brings these molecules to the brink of a resurgence. In this Perspective, we delve into the history of P(V)-F compounds, discuss the precautions needed to work with them safely, and explore recent advancements in their synthesis and application. We conclude by discussing how this field can continue on a path toward innovation.

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.

SO2F2-Mediated Fluorination of P(O)-H and P(O)-OH Compounds under Mild Conditions

With the increasing relevance of organophosphorus fluorine compounds in the pharmaceutical industry, their synthesis has attracted great attention. Herein, we report an efficient fluorination strategy for P(O)-H and P(O)-OH compounds using sulfuryl fluoride as the fluorination reagent. Avoiding the use of expensive or complex prepreparation reagents for fluoridation, this strategy could conveniently construct a variety of fluorophosphonates and phosphonofluoridates under mild conditions and without additional oxidants.

Rapid Generation of P(V)-F Bonds Through the Use of Sulfone Iminium Fluoride Reagents

Phosphorus-fluorine bonds have become increasingly relevant in the pharmaceutical industry. To continue their exploration, more efficient synthetic methods are needed. Here, we report the application of sulfone iminium fluoride (SIF) reagents to the synthesis of P(V)-F bonds. The SIF reagents promote the deoxyfluorination of phosphinic acids in just 60 s with excellent yields and scope. The same P(V)-F products can also be synthesized from secondary phosphine oxides using an SIF reagent.

Mechanochemical Electrophilic Mono- or Disulfur Transfer: Construction of P(O)-S or P(O)-S-S Bonds

Under mechanochemically induced conditions, a wide range of diarylphosphine oxides or H-phosphonates react with trisulfide dioxides to afford various thiophosphate derivatives in good yields. Selective S-S bond cleavage of trisulfide dioxides determined by connecting groups is proposed as the key step in the construction of P(O)-S or P(O)-S-S bonds, which is supported by calculations.

Electrochemical Enabled Cascade Phosphorylation of N-H/O-H/S-H Bonds with P-H Compounds: An Efficient Access to P(O)-X Bonds

An electrochemical three component cascade phosphorylation reaction of various heteroatoms-containing nucleophiles including carbazoles, indoles, phenols, alcohols, and thiols with Ph₂ PH has been established. Electricity is used as the "traceless" oxidant and water and air are utilized as the "green" oxygen source. All kinds of structurally diverse organophosphorus compounds with P(O)-N/P(O)-O/P(O)-S bonds are assembled in moderate to excellent yields (three categories of phosphorylation products, 50 examples, up to 97 % yield). A tentative free radical course is put forward to rationalize the reaction procedure.

Nucleophilic H-Phosphites, H-Phosphinates, and H-Phosphine Oxides in Organic Reactions

P(O)–H compounds like H-phosphites, H-phosphinates, and H-phosphine oxides are widely used as nucleophiles. Herein, their reactions with unsaturated compounds, C–H activation, the Hirao reaction, P–C, P–S, P–O, P–N, and P–F couplings are thoroughly discussed and summarized. This review will focus on their reactions with alkenes, alkynes, enamides, propynoic acids, epoxide, arynes, arenes, quinones, isothiocyanates, diazo compounds, aldehydes, ketones, imines, pyridines, acid derivatives, carbocations, aryl halides, dibromoalkenes, disulfides, thiosulfates, sulfonyl chlorides, iodonium salts, amines, alcohols, and thiols.

1 Introduction

2 Addition to Alkenes/Alkynes

3 Addition to Other Unsaturated Compounds

4 Coupling with Carbocations

5 Phosphorylation of Aryl C–H Bonds

6 Hirao Reaction

7 P–S, P–O, P–N, or P–F Coupling

8 Conclusions

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.

Redox-Neutral P(O)-N Coupling between P(O)-H Compounds and Azides via Dual Copper and Photoredox Catalysis

We report a redox-neutral P(O)-N coupling reaction of P(O)-H compounds with azides via photoredox and copper catalysis, providing new access to useful phosphinamides, phosphonamides, and phosphoramides. This transformation tolerates a wide range of nucleophilic functionalities including alcohol and amine nucleophiles, which makes up for the deficiency of classical nitrogen nucleophilic substitution reactions. As a demonstration of the broad potential applications of this new methodology, late-stage functionalization of a diverse array of azido-bearing natural products and drug molecules, a preliminary asymmetric reaction, and a continuous visible-light photoflow process have been developed.

A phosphoryl radical-initiated Atherton–Todd-type reaction under open air

A phosphoryl radical-initiated Atherton–Todd-type reaction enables the phosphorylation of alcohols, phenols, and amines under mild reaction conditions.

Rapid one-step 18F-radiolabeling of biomolecules in aqueous media by organophosphine fluoride acceptors

Currently, only a few ¹⁸F-radiolabeling methods were conducted in aqueous media, with non-macroelement fluoride acceptors and stringent conditions required. Herein, we describe a one-step non-solvent-biased, room-temperature-driven ¹⁸F-radiolabeling methodology based on organophosphine fluoride acceptors. The high water tolerance for this isotope-exchange-based ¹⁸F-labeling method is attributed to the kinetic and thermodynamic preference of F/F over the OH/F substitution based on computational calculations and experimental validation. Compact [^18/19F]di-tert-butyl-organofluorophosphine and its derivatives used as ¹⁸F-labeling synthons exhibit excellent stability in vivo. The synthons are further conjugated to several biomolecular ligands such as c(RGDyk) and human serum albumin. The one-step labeled biomolecular tracers demonstrate intrinsic target imaging ability and negligible defluorination in vivo. The current method thus offers a facile and efficient ¹⁸F-radiolabeling pathway, enabling further widespread application of ¹⁸F.

The synthesis of ¹⁸F-labeled positron emission tomography (PET) tracers is difficult and typically requires anhydrous conditions. Here, the authors developed organophosphine precursors that allow for quick, high-yield synthesis of ¹⁸F-labeled probes in either organic solvents or aqueous media.

Iron-catalyzed clean dehydrogenative coupling of alcohols with P(O)–H compounds: a new protocol for ROH phosphorylation

An efficient oxygen–phosphoryl bond-forming reactionviairon-catalyzed cross dehydrogenative coupling has been developed. The reaction proceeds efficiently under oxidant- and halide-free conditions with H₂liberation, and represents a straightforward method to prepare organophosphoryl compounds from alcohols and P(O)–H compounds.

The cooperative FeCl3/DDQ system for the regioselective synthesis of 3-arylindoles from β-monosubstituted 2-alkenylanilines

A highly regioselective synthesis of 3-arylindoles by using the cooperative FeCl₃/DDQ system has been developed.

Chloroform-based Atherton–Todd-type reactions of alcohols and thiols with secondary phosphine oxides generating phosphinothioates and phosphinates

Various valuable phosphinothioates and phosphinates including those with functional groups are readily prepared under mild reaction conditions via chloroform-based Atherton–Todd-type reactions of secondary phosphine oxides with alcohols and thiols, respectively.

Mn(iii)-mediated phosphonation–azidation of alkenes: a facile synthesis of β-azidophosphonates

A new and general method for the synthesis of β-azidophosphonates has been achieved through Mn(OAc)₃-mediated radical oxidative phosphonation–azidation of alkenes.

Copper-catalyzed radical cascade cyclization for the synthesis of phosphorated indolines

A novel and convenient approach to the synthesis of various phosphorated indolines via a copper-catalyzed radical cascade cyclization reaction has been developed.