Silver-catalyzed P-centered anion nucleophilic addition to isocyanide: access to 2-phosphinoyl indoles/indol-3-ols

A silver-catalyzed chemoselective cascade nucleophilic addition of a P-centered anion to isocyanides and cyclization reaction was developed for the efficient and practical synthesis of a wide range of 2-phosphinoyl indole and indol-3-ol derivatives. Unlike the well-documented synthesis of phosphorus-functionalized heterocycles via a P-centered radical, an anionic reactivity profile of phosphine oxides is most likely involved in this domino transformation.

Synthetic Methods for Azaheterocyclic Phosphonates and Their Biological Activity: An Update 2004-2024

The increasing importance of azaheterocyclic phosphonates in the agrochemical, synthetic, and medicinal field has provoked an intense search in the development of synthetic routes for obtaining novel members of this family of compounds. This updated review covers methodologies established since 2004, focusing on the synthesis of azaheterocyclic phosphonates, of which the phosphonate moiety is directly substituted onto to the azaheterocyclic structure. Emphasizing recent advances, this review classifies newly developed synthetic approaches according to the ring size and providing information on biological activities whenever available. Furthermore, this review summarizes information on various methods for the formation of C-P bonds, examining sustainable approaches such as the Michaelis-Arbuzov reaction, the Michaelis-Becker reaction, the Pudovik reaction, the Hirao coupling, and the Kabachnik-Fields reaction. After analyzing the biological activities and applications of azaheterocyclic phosphonates investigated in recent years, a predominant focus on the evaluation of these compounds as anticancer agents is evident. Furthermore, emerging applications underline the versatility and potential of these compounds, highlighting the need for continued research on synthetic methods to expand this interesting family.

Electrochemical Synthesis of Phosphorylated Indoles and Trp-Containing Oligopeptides

Cp2Fe-mediated electrochemical synthesis of phosphorylated indoles and Trp-containing oligopeptides has been developed, which eliminates the need for external oxidants and yields the desired products in moderate to excellent yields under mild conditions. Importantly, the synthetic applicability was further demonstrated through its easy scalability and the anticancer activity of the product. Remarkably, it presents the first electrochemical protocol to access the phosphorylation of indoles and Trp-containing oligopeptides.

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.

Excited-state cobaloxime catalysis enabled scalable oxidant-free dehydrogenative C–H phosphinoylation of undirected heterocycles

Visible-light-induced excited-state cobalt catalysis enables C(sp2)–H/C(sp3)–H phosphinoylation accompanied by H2 evolution. The reaction achieves the late-stage modification of more than 10 distinct classes of heterocycles and arenes.

Phosphorylation of arenes, heteroarenes, alkenes, carbonyls and imines by dehydrogenative cross-coupling of P(O)-H and P(R)-H

Organophosphorous compounds have recently emerged as a powerful class of compounds with widespread applications, such as in bioactive natural products, pharmaceuticals, agrochemicals and organic materials, and as ligands in catalysis. The preparation of these compounds requires synthetic techniques with novel catalytic systems varying from transition metal, photo- and electrochemical catalysis to transformations without metal catalysts. Over the past few decades, the addition of P-H bonds to alkenes, alkynes, arenes, heteroarenes and other unsaturated substrates in hydrophosphination and other related reactions via the above-mentioned catalytic processes has emerged as an atom economical approach to obtain organophosphorus compounds. In most of the catalytic cycles, the P-H bond is cleaved to yield a phosphorus-based radical, which adds onto the unsaturated substrate followed by reduction of the corresponding radical yielding the product.

Palladium-Catalyzed Remote C-H Phosphonylation of Indoles at the C4 and C6 Positions by a Radical Approach

Palladium-catalyzed direct C-H activation of indole benzenoid moiety has been achieved in the past decade. However, palladium-catalyzed remote C-H activation of indoles is rare. Herein, we report a challenging palladium-catalyzed remote C4-H phosphonylation of indoles by a radical approach. The method provides access to a series of C4-phosphonylated indoles, including tryptophan and tryptophan-containing dipeptides, which are typically inaccessible by direct C4-H activation due to its heavy reliance on C3 directing groups. Notably, unexpected C6-phosphonylated indoles were obtained through blocking of the C4 position. The preliminary mechanistic studies indicated that the reactions may proceed via a C7-palladacycle/remote-activation process. Based on the strategy, examples of remote C4-H difluoromethylation with BrCF₂ COOEt are also presented, suggesting that the strategy may offer a general blueprint for other cross-couplings.

Copper-Catalyzed Vicinal Cyano-, Thiocyano-, and Chlorophosphorylation of Alkynes: A Phosphinoyl Radical-Initiated Approach for Difunctionalized Alkenes

A copper-catalyzed difunctional cyano-, thiocyano-, and chlorophosphorylation reaction of alkynes with P(O)-H compounds and coupling partners (TBACN, TMSNCS, TMSCl) is described. The reaction introduces versatile groups (-P(O)R₂ and -CN, -SCN, or -Cl) to form tri- and tetrasubstituted alkenyl phosphine oxides/phosphonates regio- and stereoselectively.

Silver-catalysed C–H bond activation: a recent review

Transition metal catalysed C–H activations are efficient, simple, mild, cost-effective and stereoselective, and many of them are environmentally sustainable transformations.

Synthesis, characterization and cytotoxic activity of cationic half-sandwich Ru(ii) complexes stabilized by iminophosphorane N,N,S and N,N,Se tridentate ligands

New Ru(ii) half-sandwich complexes stabilized by tridentate iminophosphorane N,N,S or N,N,Se ligands show potent cytotoxic activity with high selectivity.

Recent Organic Transformations with Silver Carbonate as a Key External Base and Oxidant

Silver carbonate (Ag2CO3), a common transition metal-based inorganic carbonate, is widely utilized in palladium-catalyzed C–H activations as an oxidant in the redox cycle. Silver carbonate can also act as an external base in the reaction medium, especially in organic solvents with acidic protons. Its superior alkynophilicity and basicity make silver carbonate an ideal catalyst for organic reactions with alkynes, carboxylic acids, and related compounds. This review describes recent reports of silver carbonate-catalyzed and silver carbonate-mediated organic transformations, including cyclizations, cross-couplings, and decarboxylations.

Palladium(ii)-catalyzed oxidative C(sp3)-P bond formation via C(sp3)-H bond activation

Disclosed herein is a Pd(ii)-catalyzed C(sp³)-H/P-H oxidative cross-coupling reaction between 8-methylquinolines with H-phosphonates or diarylphosphine oxides via chelation-assisted C(sp³)-H bond activation. The protocol exhibits a relatively broad functional-group tolerance and exclusive chemo- and regioselectivity. Furthermore, detailed mechanistic studies support the proposed reaction pathway.

Ag-Mediated Radical Cyclization of 2-Alkynylthio(seleno)anisoles: Direct Synthesis of 3-Phosphinoylbenzothio(seleno)phenes

A new method for the direct synthesis of 3-phosphinoylbenzothio(seleno)phenes has been achieved through an Ag-mediated radical addition-cyclization of 2-alkynylthio(seleno)anisoles with secondary phosphine oxides in good yields under mild conditions. In this single reaction, benzenethiophene or benzeneselenophene skeleton, C(sp²)-P and C(sp²)-S bonds can be constructed with the cleavage of the C(sp³)-S bond, highlighting the efficiency and step-economics of this protocol.

Regioselective N-1 and C-2 diacylation of 3-substituted indoles with arylglyoxal hydrates for the synthesis of indolyl diketones

A highly regioselective N-1 and C-2 diacylation of 3-substituted indoles with arylglyoxal hydrates to afford N-1 and C-2 indolyl diketones in moderate to good yields is described. Notably, the control of regioselectivity is achieved by small changes in the Cu catalyst, additive and solvent. Importantly, the intermediates for N-1 and C-2 diacylation were detected and two plausible pathways were also proposed.

Highly selective C–H bond activation of N-arylbenzimidamide and divergent couplings with diazophosphonate compounds: a catalyst-controlled selective synthetic strategy for 3-phosphorylindoles and 4-phosphorylisoquinolines

A highly efficient synthetic strategy to construct 3-phosphorylindole and 4-phosphorylisoquinoline was achieved.

Applications of H-phosphonates for C element bond formation

The readily accessible and inexpensive dialkyl H-phosphonates are important building blocks for organic synthesis. This review specifically covers our recent work on the application of H-phosphonates as reactants for C–P bond formation, and as promoters for quinoline N-oxides to synthesize 2-functionalized quinolines.

Lewis Acid-Controlled Regioselective Phosphorylation of 2-Indolylmethanols with Diarylphosphine Oxides: Synthesis of Highly Substituted Indoles

The Lewis acid-promoted phosphorylation of 2-indolylmethanols with diarylphosphine oxides is described. The regioselectivity of the reaction can be modulated by the choice of rare earth metal Lewis acid, offering a highly selective approach to structurally diverse indole derivatives in up to 97% yield for over 50 examples. This strategy features high selectivity, good functional group tolerance, and easy scalability. The utility of this method is further highlighted by facile modification of the products to access novel indole-based phosphine ligand.

External oxidant-free cross-coupling: electrochemically induced aromatic C–H phosphonation of azoles with dialkyl-H-phosphonates under silver catalysis

A convenient external oxidant-free method of azole derivatives phosphorylation by dialkyl-H-phosphonates through electrochemical catalytic oxidation in the presence of silver salts (1%) is proposed.

The regioselective synthesis of 2-phosphinoylindoles via Rh(iii)-catalyzed C–H activation

A step-economical route for the synthesis of 2-phosphinoylindoles via the Rh(iii)-catalyzed redox-neutral annulation of N-nitrosoanilines with 1-alkynylphosphine oxides was developed.

Recent progress in the synthesis of phosphorus-containing indole derivatives

Phosphorus-containing indole derivatives represent a special class of phosphorus-containing nitrogen heterocycles. This review summarizes the recent progress in the synthesis of such compounds, briefly discusses the reaction mechanisms and challenges, and outlines the synthetic opportunities still open.

Brønsted acid-catalysed regiodivergent phosphorylation of 2-indolylmethanols to synthesize benzylic site or C3-phosphorylated indole derivatives

A Brønsted acid catalyzed highly regiodivergent phosphorylation of 2-indolylmethanols with diarylphosphine oxides has been established, which provides an efficient protocol for accessing benzylic site or C3-phosphorylated indole derivatives with structural diversity.

Metal-free electrophilic phosphination of electron-rich arenes, arenols and aromatic thiols with diarylphosphine oxides

A metal-free and mild route to aromatic organophosphorus compounds from stable phosphines.

Merging photoredox catalysis with transition metal catalysis: site-selective C4 or C5-H phosphonation of 8-aminoquinoline amides

A simple and efficient protocol for the transition metal-catalyzed site-selective C–H phosphonation of 8-aminoquinoline at the C4 or C5 positions via a photoredox process was developed.

Cu/Pd cooperatively catalyzed tandem C–N and C–P bond formation: access to phosphorated 2H-indazoles

An unprecedented Cu/Pd cooperatively catalyzed tandem C–N/C–P bond formation reaction for the synthesis of phosphorated 2H-indazoles has been developed.

Palladium/silver reagent-promoted aryl phosphorylation: flexible synthesis of substituted-3-benzylidene-2-(2-(diphenylphosphoryl)-aryl)-isoindolin-1-one

A novel Pd(OAc)₂/Ag₂CO₃-catalyzed coupling reaction was investigated. Substituted 3-benzylidene-2-arylisoindolin-1-ones was reacted with diphenylphosphine oxide to afford 3-arylidene-2-(2-(diphenylphosphoryl)aryl)isoindolin-1-ones.