Palladium-Catalyzed CP Cross-Coupling of Arylhydrazines with H-PhosphonatesviaCN Bond Cleavage

Copper(II)-catalyzed cascade Csp2-P/C-C bond formation to construct benzo[d]thiazol-2-ylphosphonates

A novel, copper(II)-catalyzed cascade Csp2-P/C-C bond formation in o-haloaryl isothiocyanates with organophosphorus esters has been developed under mild conditions. A series of benzo[d]thiazol-2-ylphosphonates were synthesized in moderate to good yields. Different from the traditional method of obtaining these scaffolds with radical reactions, the method proposed allows accessing them via ionic reactions and has the advantages of easy access to raw materials and simple operation. Finally, we carried out a gram-scale experiment to further demonstrate the scalability of this strategy in the efficient synthesis of benzo[d]thiazol-2-ylphosphonates.

Stereospecific nickel-catalyzed [4+2] heteroannulation of alkynes with aminophosphanes

Enantioenriched phosphorus compounds play crucial roles in many fields ranging from catalyst to materials science to drug development. Despite advances in the construction of phosphacycles, incorporation of a P-chirogenic center into heterocycles remains challenging. Here, we report an effective method for the preparation of phosphacycles through nickel-catalyzed [4+2] heteroannulation of internal alkynes with aminophosphanes derived from o-haloanilines. Notably, chiral 2-λ5-phosphaquinolines can be prepared from P-stereogenic substrates via NH/PH tautomeric equilibrium without loss of stereochemical integrity. The strategy is found to exhibit a broad scope in terms of both reaction components, enabling modular construction of libraries of 2-λ5-phosphaquinolines with different steric and electronic properties for fine-tuning photophysical properties, where some of these compounds showed distinct fluorescence with high quantum yields. A series of mechanistic studies further shed light on the pathway of the heteroannulation and reasons for stereospecificity.

Palladium-Catalyzed Oxidative Nonclassical Heck Reaction of Arylhydrazines with Allylic Alcohols via C-N Bond Cleavage: Access to β-Arylated Carbonyl Compounds

An efficient palladium-catalyzed oxidative nonclassical Heck reaction of arylhydrazines with allylic alcohols via C-N bond cleavage has been successfully developed. This method provides a series of β-arylated carbonyl compounds with broad functional group tolerance under base-free, simple, and mild open air reaction conditions. In the reaction, arylhydrazines with the smaller molecular weight of the leaving group were employed as the "green" arylation reagent, which released N₂ and water as the byproducts under air. Mechanistic studies suggested that an aryl radical process and Pd-H complex migration reinsertion were involved. Moreover, the synthesis of the antiarrhythmic drug propafenone was completed with this transformation as the key step.

Transition-Metal-Free Photoredox Phosphonation of Aryl C-N and C-X Bonds in Aqueous Solvent Mixtures

Herein, we present an efficient and mild methodology for the synthesis of aromatic phosphonate esters in good to excellent yields using 10H-phenothiazine, an inexpensive commodity chemical, as a photoredox catalyst. The reaction exhibits wide functional group compatibility enabling the transformation in the presence of ketone, amide, ester, amine, and alcohol moieties. Importantly, the reaction proceeds using a green solvent mixture primarily composed of water, thus lowering the environmental footprint of this transformation compared to current methods. The transformation also proceeds under atmospheric conditions, which further differentiates it from current methods that require inert atmosphere. Mechanistic work using fluorescence quenching experiments and radical trapping approaches support the proposed mechanism.

I2-mediated Csp2–P bond formation via tandem cyclization of o-alkynylphenyl isothiocyanates with organophosphorus esters

A highly efficient molecular-iodine-catalyzed cascade cyclization reaction has been developed, creating a series of 4H-benzo[d][1,3]thiazin-2-yl phosphonates in moderate to excellent yields. This approach benefits from metal-free catalysts and available raw materials.

Palladium-catalyzed phosphorylation of arylsulfonium salts with P(O)H compounds via C–S bond cleavage

Herein we report a novel palladium-catalyzed phosphorylation of arylsulfonium salts with P(O)H compounds via C–S bond cleavage under mild conditions.

Recent Advances in the Pd-Catalyzed Coupling of Arylhydrazines and Ammonium Salts via C-N Bond Cleavage

Both arylhydrazines and quaternary ammonium salts are readily accessible or commercially available chemicals that show versatile reactivity in Pd-catalyzed coupling reactions via C-N bond cleavage. A tremendous array of coupling reactions involving reaction partners such as organoborons, aryl silanes, alkenes, alkynes, arylation or alkylation reagents in C-H functionalization and carbonylation reactions are summarized, in which arylhydrazines or quaternary ammonium salts function as aryl or alkyl donors. This account mainly focuses on recent advances in Pd-catalyzed coupling reactions with arylhydrazines or quaternary ammonium salts via C-N bond cleavage, including mechanistic elucidations.

Direct Synthesis of ortho-Halogenated Arylphosphonates via a Three-Component Reaction Involving Arynes

A three-component reaction involving arynes, trialkyl phosphites, and halides has been achieved under mild reaction conditions. This transformation provides a direct synthetic approach to ortho-halogenated arylphosphonates, which could be rapidly converted to diversely ortho-functionalized arylphosphorus compounds.

Nickel-catalyzed coupling of R2P(O)Me (R = aryl or alkoxy) with (hetero)arylmethyl alcohols

α-Alkylation of methyldiarylphosphine oxides with (hetero)arylmethyl alcohols was performed under nickel catalysis. Various arylmethyl and heteroarylmethyl alcohols can be used in this transformation. A series of methyldiarylphosphine oxides were alkylated with 30-90% yields. Functional groups on the aromatic rings of methyldiarylphosphine oxides or arylmethyl alcohols including OMe, NMe2, SMe, CF3, Cl, and F groups can be tolerated. The conditions are also suitable for the α-alkylation reaction of dialkyl methylphosphonates.

Recent Advances in Metal-Catalyzed Heterocyclic C-P Bond Formation

The phosphorus-containing heterocycles are an important class of compounds in organic chemistry. Because of their potential application in many fields, especially, the synthetic pesticides, medicine and catalyst, the phosphorus-containing heterocycles have attracted continuous attention from organic synthesis scientists. The development of efficient and low-cost catalytic systems is of great interest for the construction of heterocycles C-P bond. Usually, the phosphorus-containing heterocycles is prepared via direct carbon-hydrogen (C-H) bond activation or pre-functionalized of heterocycles with phosphorus-hydrogen (P-H) bond of phosphorus compounds reaction by metal-catalyzed. This review summarizes recent progress in the heterocycles C-P bond formation reactions by metal-catalyzed, which mainly focus on the discussion of the reaction mechanism. It aims to provide efficient methods for the future synthesis and application in this field.

Shining Light on the Light-Bearing Element: A Brief Review of Photomediated C–H Phosphorylation Reactions

Organophosphorus compounds have numerous useful applications, from versatile ligands and nucleophiles in the case of trivalent organophosphorus species to therapeutics, agrochemicals and material additives for pentavalent species. Although phosphorus chemistry is a fairly mature field, the construction of C–P(V) bonds relies heavily on either prefunctionalized substrates such as alkyl or aryl halides, or requires previously oxidized bonds such as C=N or C=O, leading to potential sustainability issues when looking at the overall synthetic route. In light of the recent advances in photochemistry, using photons as a reagent can provide better alternatives for phosphorylations by unlocking radical mechanisms and providing interesting redox pathways. This review will showcase the different photomediated phosphorylation procedures available for converting C–H bonds into C–P(V) bonds.

1 Introduction

1.1 Organophosphorus Compounds

1.2 Phosphorylation: Construction of C–P(V) Bonds

1.3 Photochemistry as an Alternative to Classical Phosphorylations

2 Ionic Mechanisms Involving Nucleophilic Additions

3 Mechanisms Involving Radical Intermediates

3.1 Mechanisms Involving Reactive Carbon Radicals

3.2 Mechanisms Involving Phosphorus Radicals

3.2.1 Photoredox: Direct Creation of Phosphorus Radicals

3.2.2 Photoredox: Indirect Creation of Phosphorus Radicals

3.2.3 Dual Catalysis

3.3 Photolytic Cleavage

4 Conclusion and Outlook

Radical Arylation of Triphenyl Phosphite Catalyzed by Salicylic Acid: Mechanistic Investigations and Synthetic Applications

A straightforward and scalable methodology to synthesize diphenyl arylphosphonates at 20 °C within 1-2 h is reported using inexpensive SA as the catalytic promoter of the reaction. Mechanistic investigations suggest that the reaction proceeds via radical-radical coupling, consistent with the so-called persistent radical effect. The reaction tolerated a wide range of functional groups and heteroaromatic moieties. The synthetic usefulness and the unique reactivity of the obtained phosphonates were demonstrated in different one-step transformations.

Catalyst-free phosphorylation of aryl halides with trialkyl phosphites through electrochemical reduction

A catalyst-free electrochemical cross-coupling reaction of aryl halides with trialkyl phosphite has been developed. This reaction proceeds in an undivided cell with a low-cost Ni anode and a graphite cathode under mild and neutral conditions. A wide range of functional groups are well-tolerated and the phosphorylated product can be obtained on the gram scale, showing that this transformation has the potential to be a valuable method for the construction of aromatic carbon-phosphorus bonds.

Surfactant-Type Catalyst for Aerobic Oxidative Coupling of Hydrazine with Thiol in Water

A series of PEG-functionalized nitrogen ligands were developed to conduct an aerobic oxidative cross-coupling reaction between alkyl- or aryl-hydrazines with thiols in water. This surfactant-type catalyst enables high efficiencies and selectivities, while tolerating a large variety of functional groups. The mother liquor is still catalytically active after five runs.

Visible-light-promoted organic dye-catalyzed sulfidation and phosphorylation of arylhydrazines toward aromatic sulfides and diarylphosphoryl hydrazides

Visible-light-promoted sulfidation and phosphorylation of arylhydrazines for the synthesis of aromatic sulfides and diarylphosphoryl hydrazides were developed using the organic dyes rose bengal and Na₂-eosin Y as photocatalysts, respectively.

Arylhydrazines: novel and versatile electrophilic partners in cross-coupling reactions

Arylhydrazines are extremely valuable compounds in organic chemistry that are widely used for the synthesis of a variety of biologically active molecules such as indoles, indazoles, pyrazoles, aryltriazoles, β-lactams and quinazolines. These compounds have also been widely utilized as arylation agents in oxidative cross-coupling reactions. In this review, we will highlight the most important explorations and developments in the carbon-carbon and carbon-heteroatom (nitrogen, phosphorus, sulfur, and selenium) cross-coupling of arylhydrazines. The literature has been surveyed from 2001 to June 2018.

Denitrogenative palladium-catalyzed coupling of aryl halides with arylhydrazines under mild conditions

A novel, simple, and efficient protocol via Pd(ii)-catalyzed denitrogenative coupling of arylhydrazines with aryl halides under ambient and mild conditions.

A mild electroassisted synthesis of (hetero)arylphosphonates

The first example of a nickel-catalyzed electrochemical coupling between dimethyl phosphite and (hetero)aryl halides to furnish (hetero)arylphosphonates is described.

Acid-promoted denitrogenative Pd-catalyzed addition of arylhydrazines with nitriles at room temperature

Pd(TFA)₂-catalyzed denitrogenative addition proceeded with selective C–N bond cleavage of arylhydrazines with nitriles under air at room temperature.

A palladium-catalyzed oxidative cross-coupling reaction between aryl pinacol boronates and H-phosphonates in ethanol

The first successful oxidative cross-coupling reaction of aryl phosphorous compounds started from pinacol aryl boronic esters is reported.

Ar–P bond construction by the Pd-catalyzed oxidative cross-coupling of arylsilanes with H-phosphonates via C–Si bond cleavage

A novel and efficient methodology that allows for the construction of Ar–P bonds via the Pd-catalyzed oxidative cross-coupling reaction of various arylsilanes with H-phosphonates leading to valuable arylphosphonates has been developed.

Palladium-catalyzed aerobic oxidative cross-coupling of arylhydrazines with terminal alkynes

The Pd-catalyzed aerobic oxidative coupling of arylhydrazines with terminal acetylenes was achieved under copper- and base-free conditions.