Silver-Mediated Selective Oxidative Cross-Coupling between C–H/P–H: A Strategy to Construct Alkynyl(diaryl)phosphine Oxide

Base-Mediated and Silver-Catalyzed Divergent Synthesis of Hydroxynaphthalenamides and Phosphorylated Dihydronaphthylamides from Enone-Oxazolones

An efficient divergent approach to functionalized naphthalene derivatives, the naphthalenamides, via base-mediated and silver-catalyzed cyclization has been developed using enone-oxazolones as the precursors. This protocol utilized base in methanol with heating to construct the corresponding hydroxynaphthalenamides 2 by a C-C bond formation, oxazolone ring-opening, and aromatization in good yields. On the other hand, phosphorylated dihydronaphthylamides 3 were generated by using H-phosphonate as the phosphonating reagent in a silver-catalyzed cyclization involving the phospha-1,4-addition/intramolecular ring closure with concomitant C-P/C-C bond formation in good yields.

Non-Noble-Metal Mono and Bimetallic Composites for Efficient Electrocatalysis of Phosphine Oxide and Acetylene C-H/P-H Coupling under Mild Conditions

The present work describes an efficient reaction of electrochemical phosphorylation of phenylacetylene controlled by the composition of catalytic nanoparticles based on non-noble-metals. The sought-after products are produced via the simple synthetic protocol based on room temperature, atom-economical reactions, and silica nanoparticles (SNs) loaded by one or two d-metal ions as nanocatalysts. The redox and catalytic properties of SNs can be tuned with a range of parameters, such as compositions of the bimetallic systems, their preparation method, and morphology. Monometallic SNs give phosphorylated acetylene with retention of the triple bond, and bimetallic SNs give a bis-phosphorylation product. This is the first example of acetylene and phosphine oxide C-H/P-H coupling with a regenerable and recyclable catalyst.

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.

Highly Regioselective Tandem Reaction of Ene-Yne-Oxazolones Induced by H-Phosphonates: Construction of Phosphinylindane Derivatives

A highly regioselective divergent approach for the phosphine-containing indane/indene derivatives from the ene-yne-oxazolone precursors was reported. An insight into the reaction mechanism involving the phospha-1,4-addition followed by 5-exo-dig ring closure with a concomitant C-P/C-C bond formation was also proposed. This promising protocol utilized H-phosphonate as the phosphonating reagent in a silver-catalyzed or base-mediated cascade cyclization to construct the corresponding phosphorylated spiroindenoxazolones and amidoindenes, respectively, in good yields (up to 88% yield).

Nonconventional driving force for selective oxidative C-C coupling reaction due to concurrent and curious formation of Ag0

Is it possible to 'explore' metal's intrinsic property-a cohesive interaction-which naturally transform M0 into an aggregate or a particle or film for driving oxidative C-C bond formation? With this intention, reduction of [Ag(NH3)2]+ to Ag0 with concurrent oxidation of different phenols/naphthols to biphenyls was undertaken. The work is originated during careful observation of an undergraduate experiment-Tollens' test-where silver mirror film deposition takes place on the walls of borosilicate glass test tube. When the same reaction was carried out in polypropylene (plastic-Eppendorf) tube, we observed aggregation of Ag0 leading to floating Ag-particles but not silver film deposition. This prompted us to carry out challenging cross-coupling reaction by ONLY changing the surface of the reaction flask from glass to plastic to silicones. To our surprise, we observed good selective oxidative homo-coupling on Teflon surface while cross-coupling in Eppendorf vial. Thus, we propose that the formation of biphenyl is driven by the macroscopic growth of Ag0 into [Ag-particle] orchestrated by Ag…Ag cohesive interaction. To validate results, experiments were also performed on gram scale. More importantly, oxidation of β-naphthol carried out in quartz (chiral) tube which yielded slight enantioselective excess of BINOL. Details are discussed.

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.

Cross-Dehydrogenative Alkynylation: A Powerful Tool for the Synthesis of Internal Alkynes

Alkynes are among the most fundamentally important organic compounds and are widely used in synthetic chemistry, biochemistry, and materials science. Thus, the development of an efficient and sustainable method for the preparation of alkynes has been a central concern in organic synthesis. Cross-dehydrogenative coupling utilizing E-H and Z-H bonds in two different molecules can avoid the need for prefunctionalization of starting materials and has become one of the most straightforward methods for the construction of E-Z chemical bonds. This Review summarizes recent progress in the preparation of internal alkynes by cross-dehydrogenative coupling with terminal alkynes.

A synthetic guide to alkynyl sulfides

The relative stability and predictable reactivity of alkynyl sulfides make them ideal synthons for the development of new transformations. Classic methods for forming alkynyl sulfides relied on dehydrohalogenation approaches. However more recent methods have focused on employing umpolung strategies, as well as nucleophilic and electrophilic thiol alkynylation. In addition, the recent syntheses of Csp-S bonds have trended towards exploiting catalysis and expanding the reaction scope of the methods. A survey of existing methods to form alkynyl sulfides is presented as well as an evaluation with regards to the scope of each method, to provide the reader with an overview of advantages and limitations of current technology.

TiO2/Cu2O nanoparticle-catalyzed direct C(sp)-P bond formation via aerobic oxidative coupling in air and visible light

The synthesis of organophosphorus compounds is one of the important goals in organic chemistry. Among these compounds, alkynylphosphonates are significantly utilized as the main precursors for the synthesis of biologically active molecules in medicinal chemistry and have attracted extensive interest in the past few decades. Although few efforts have been made towards the direct and atom-economical synthesis of alkynylphosphonates, efforts towards the utilization of visible light as a green and renewable energy source have not been made to date. Here, we have promoted a strategy to construct a type of nano metal oxide composite photocatalyst (Cu2O decorated on TiO2) for the synthesis of alkynylphosphonates via direct C-P bond formation between terminal alkyne and H-phosphonate under visible light irradiation. In this p-n heterojunction photocatalyst, Cu2O acted as a visible-light absorber; moreover, the CB (conduction band) of TiO2 was favorable for accepting a photogenerated electron, and the generated electron hole (e-/h+) pair could initiate the reaction. The present study can provide a new way for the synthesis of this important class of phosphorus organic compounds.

Additive-free coupling of bromoalkynes with secondary phosphine oxides to generate alkynylphosphine oxides in acetic anhydride

A coupling of bromoalkynes with secondary phosphine oxides was developed to generate alkynylphosphine oxides under additive-free conditions in acetic anhydride.

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.

An efficient preparation of β-ketophosphine oxides from alkynylphosphine oxides with benzaldehyde oxime as a hydroxide source

An effective transition-metal-free method has been developed for the preparation of β-ketophosphine oxides from alkynylphosphine oxides with benzaldehyde oxime.

Photoredox-catalyzed decarboxylative alkylation/cyclization of alkynylphosphine oxides: a metal- and oxidant-free method for accessing benzo[b]phosphole oxides

By photoredox-catalysis, alkylation/aryl cyclization of alkynylphosphine oxides towards benzo[b]phospholes has been realized under metal- and oxidant-free conditions at room temperature.

Aerobic oxidative alkynylation of H-phosphonates and amides: an efficient route for the synthesis of alkynylphosphonates and ynamides using a recyclable Cu–MnO catalyst

We developed a straightforward, atom-economical and scalable route for the synthesis of alkynylphosphonates and ynamides using a reusable Cu–MnO catalyst.

Selective P-C(sp3 ) Bond Cleavage and Radical Alkynylation of α-Phosphorus Alcohols by Photoredox Catalysis

Herein the first P-C(sp³ ) bond cleavage and radical alkynylation of α-phosphorus alcohols to construct phosphonoalkynes is reported. The phosphorus radical is generated upon P-C bond cleavage reaction via the alkoxyl radical through photoredox catalysis with cyclic iodine(III) reagents. Various arylphosphinoyl-, alkylphosphinoyl-, phosphonate-, and phosphonic amide alcohols serve as radical phosphorus precursors to construct phosphonoalkynes for the first time.

Rhodium/Silver Synergistic Catalysis in Highly Enantioselective Cycloisomerization/Cross Coupling of Keto-Vinylidenecyclopropanes with Terminal Alkynes

A rhodium/silver synergistic catalysis has been established, enabling cycloisomerization/cross coupling of keto-vinylidenecyclopropanes (VDCPs) with terminal alkynes toward the regio- and enantioselective formation of diversified tetrahydropyridin-3-ol tethered 1,4-enynes in good yields and high ee values. In this synergistic catalysis, Rh(I) and Ag(I) catalysts selectively activate keto-VDCP substrates and terminal alkynes to generate the π-allyl Rh(III) complex of oxa-rhodacyclic intermediate and Ag alkynyl intermediate, respectively. The rapid transmetalation of alkynyl groups from Ag to Rh is proposed to play a key role in realizing the regioselective cleavage of the distal bond of the three-membered ring in this transformation.

Copper-catalyzed oxidative dehydrogenative coupling of carboxylic acids with H-phosphonates: an efficient and practical approach to acyl phosphate esters

A practical method through a copper-catalyzed dehydrogenative coupling of carboxylic acids with H-phosphonates to construct acyl phosphate esters has been developed.

Visible-Light-Induced Cascade Reaction of Isocyanides and N-Arylacrylamides with Diphenylphosphine Oxide via Radical C-P and C-C Bond Formation

An effective photoredox-mediated tandem phosphorylation/cyclization reaction of diphenylphosphine oxide with three types of radical acceptors leads to P(O)Ph₂-containing phenanthridines, isoquinolines, and indolin-2-ones by formation of both C-P and C-C bonds. [Ir(ppy)₂(dtbpy)]PF₆ (1 mol %) was used as the catalyst, CsF or Cs₂CO₃ as the base, and K₂S₂O₈ as the oxidant. A series of functional groups can be tolerated at room temperature. Moderate to good yields were generated.

Ag-catalyzed C-H/C-C bond functionalization

Silver, known and utilized since ancient times, is a coinage metal, which has been widely used for various organic transformations in the past few decades. Currently, the silver-catalyzed reaction is one of the frontier areas in organic chemistry, and the progress of research in this field is very rapid. Compared with other transition metals, silver has long been believed to have low catalytic efficiency, and most commonly, it is used as either a cocatalyst or a Lewis acid. Interestingly, the discovery of Ag-catalysis has been significantly improved in recent years. Especially, Ag(i) has been demonstrated as an important and versatile catalyst for a variety of organic transformations. However, so far, there has been no systematic review on Ag-catalyzed C-H/C-C bond functionalization. In this review, we will focus on the development of Ag-catalyzed C-H/C-C bond functionalization and the corresponding mechanism.

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.

Dehydrogenative coupling involving P(O)–H bonds: a powerful way for the preparation of phosphoryl compounds

This Frontier highlights the recent progress in the preparation of organophosphorus compounds via transition metal-catalysed dehydrogenative couplings of P(O)H compounds with Z–H compounds.

Synchronous double C–N bond formation via C–H activation for a novel synthetic route to phenazine

Pd–Ag binary nanocluster-catalysed synchronous double C–N bond formationviaC–H activation during self-coupling of anilines to form phenazines.