Hydrophosphorylation of Alkynes Catalyzed by Palladium: Generality and Mechanism

Rhodium-catalyzed enantioselective hydrogenation of (1-arylvinyl)phosphonates with TADDOL-based phosphoramidite P,S ligands

A series of readily available modular chiral P,S-bidentate TADDOL-based phosphoramidites were evaluated in the Rh(I)-catalyzed hydrogenation of α,β-unsaturated phosphonates. The Rh(I)-L3 catalyst was revealed to be highly effective for a wide variety of diisopropyl (1-arylvinyl)phosphonates, producing the corresponding (1-arylethyl)phosphonates under mild conditions with low catalyst loading (up to 0.2 mol%) and overall excellent enantiocontrol (up to 99% ee).

Base-promoted regio- and diastereoselective synthesis of tri- and tetra-substituted homoallenyl phosphine oxides via alkynyl enones

A novel base-promoted method for hydrophosphinylation of alkynyl enones with secondary phosphine oxides has been developed. Using inexpensive and commercially available potassium carbonate, a variety of functionalized tri-substituted allene products were synthesized with exclusive regio- and diastereoselectivity under mild conditions. Furthermore, a one-pot, two-step, three-component tandem hydrophosphinylation/Heck reaction efficiently produced tetra-substituted homoallenyl phosphine oxides in excellent yields, demonstrating a relatively broad substrate scope.

Palladium-catalyzed regio- and enantio-selective trifluoromethylated allylic alkylation of diphenylphosphine oxides

The first convenient method for the allylic alkylation of diphenylphosphine oxides catalyzed by palladium has been designed and developed, affording various chiral allylphosphine oxides bearing CF3 groups with exclusive regio-selectivity and excellent enantioselective control. The reaction was performed in one pot under relatively mild reaction conditions using "easy-to-prepare" starting materials and relatively inexpensive chiral bis(phosphines) ligands. Further transformations of a representative product confirm the feasibility and potential applications of our synthetic strategies. In conclusion, this study provides a valuable method method for synthesizing chiral molecules bearing CF3 and allylphosphine oxide.

Recent progress in the catalytic transformation of acetylene

Acetylene, a traditional industrial raw material, has garnered increasing attention in modern organic synthesis over the past two decades. Its catalytic transformation has emerged as an atom-economical and efficient strategy for producing a variety of high value-added compounds. This review comprehensively summarizes recent advancements and breakthroughs in the catalytic conversion of acetylene, focusing on two main categories: transition-metal-catalyzed transformations and photo-catalyzed/promoted transformations. The discussions center on various reaction intermediates, including alkenylmetals, acetylides, metallacyclopentadienes or heterometallacycles, gold carbenes, alkenyl-Ni complexes, and vinyl radicals. Furthermore, this review delves into the detailed mechanisms and diverse derivatizations of these reactions, highlighting their significance in the development of versatile acetylene catalytic transformations.

C-P Bond Formation by Nickel or Cobalt Catalyzed Coupling Reactions

This review discloses nickel- and cobalt-catalyzed coupling reactions that allow C-P bond formation. Activation of C-halide bonds to form phosphonium, pentavalent phosphorus, or trivalent phosphorous compounds has been reported with both metals. However, the conversion of C-O bonds ((activated) ethers, carbonates, acetates) into C-P ones has been only described with Ni. Similarly, there are more examples of C-Y (Y=C, S, N, B) bond activations catalyzed by Ni than by Co. Nevertheless, the cross-dehydrogenative coupling reaction between a P-H reagent and a C-H bond has been reported more often with cobalt than with nickel. In addition, for both metals, electrolytic and photocatalytic processes have been shown to produce a variety of C-P containing molecules. This review aims to provide an overview of the potential of both metals for C-P bond formation and to highlight the remaining challenges.

Metal-free regioselective hydrophosphorylation of electron-deficient alkynes catalyzed by oxazaborolidines

Here, we describe a metal-free strategy for the hydrophosphorylation of electron-deficient alkynyl to access various P-containing olefins catalyzed by commercial oxazaborolidines with high regio-selectivity (E : Z up to 99%). Interestingly, the possible mechanism suggests that the catalytic path proceeds through a synergistic addition process which leads to single E-structure products. Moreover, the chiral oxazaborolidine catalyst probably works as a Lewis pair which can accelerate the cleavage of the O-H bond in diarylphosphine oxides and provide appropriate steric hindrance to control the regioselectivity.

Selective C(sp2)-P Cross-Coupling of Alkenylsulfonium Salts with P(O)H Compounds: Divergent Synthesis of Alkenylphosphorus Compounds

Herein, we report a both regioselective and stereoselective method for the formation of C(sp2)-P bonds using alkenylsulfonium salts and >P(O)-H compounds. By employing a palladium catalyst or K2CO3, a variety of (E)-alkenylphosphorus compounds and terminal alkenylphosphorus compounds were successfully synthesized with high selectivity. Notably, trisubstituted (Z)-alkenylphosphorus compounds were synthesized for the first time under metal-free conditions. This protocol has a wide substrate scope and good functional group compatibility, providing a direct and highly selective approach for the preparation of various alkenylphosphorus compounds.

Selective hydrophosphorylation of alkynes for the synthesis of (E)-vinylphosphonates

Hydrophosphorylation of alkynes with dialkylphosphites in the various copper catalysts was investigated. The reactions provided the regio- and stereoselective E-vinylphosphonates under commercially available copper chloride catalyst in the presence of ethylene diamine as an efficient ligand. The impact of solvents, temperature, and diamine ligands are included in this report. In addition, the DFT calculations provided insight into the regio- and stereoselectivity of the reaction. It is suggested that the reaction proceeded via an in situ generated Cu(AN)4 + complex. The reaction of phenylacetylene with diethyl phosphite in the presence of EDA and the (CH3CN)4CuBF4 complex as a catalyst also gave the corresponding E-vinylphosphonates in good yield.

Copper-Catalysed Synthesis of (E)-Allylic Organophosphorus Derivatives: A Low Toxic, Mild, Economical, and Ligand-Free Method

Organophosphorus compounds are fundamental for the chemical industry due to their broad applications across multiple sectors, including pharmaceuticals, agrochemicals, and materials science. Despite their high importance, the sustainable and cost-effective synthesis of organophoshoryl derivatives remains very challenging. Here, we report the first successful regio- and stereoselective hydrophosphorylation of terminal allenamides using an affordable copper catalyst system. This reaction offers an efficient protocol for the synthesis of (E)-allylic organophosphorus derivatives from various types of P-nucleophiles, such as H-phosphonates, H-phosphinates, and secondary phosphine oxides. Key advantages of this ligand-free and atom-economic strategy include low toxicity of the Cu-based catalyst, cost effectiveness, mild reaction conditions, and experimental simplicity, making it competitive with methods that use toxic and expensive Pd-based catalysts. In an effort to comprehend this process, we conducted extensive DFT calculations on this system to uncover the mechanistic insights of this process.

Diastereoselective and Enantioselective Hydrophosphinylations of Conjugated Enynes, Allenes and Dienes via Synergistic Pd/Co Catalysis

Different from the reported work focusing on the construction of single P- or C-stereocenter via hydrophosphinylation of unsaturated carbon bonds, the highly diastereo- and enantioselective hydrophosphinylation reaction of allenes, conjugated enynes and 1,3-dienes is achieved via a designed Pd/Co dual catalysis and newly modified masked phosphinylating reagent. A series of allyl motifs bearing both a tertiary C- and P-stereocenter are prepared in generally good yields, >20 : 1 dr, >20 : 1 rr and 99 % ee. The unprecedented diastereo- and enantioselective hydrophosphinylation of 1,3-enynes is established to generate skeletons containing both a P-stereocenter and a nonadjacent chiral axis. The first stereodivergent hydrophosphinylation reaction is also developed to achieve all four P-containing stereoisomers. The present protocol features the use of only 3-minutes reaction time and 0.1 % catalyst, and with the observation of up to 730 TON. A set of mechanistic studies reveal the necessity and roles of two metal catalysts and corroborate the designed synergistic process.

Photocatalytic C(sp3)-P and C(sp2)-P Bond Formation via a Phosphorus Radical Cation

A straightforward method for the phosphorylation of electron-deficient alkenes and aryl alkynes has been developed, leading to C(sp3)-P and C(sp2)-P bond formation. This process involves the generation of phosphorus radical cation intermediates through the photocatalyzed oxidation of ethyl diarylphosphinites. The coupling with electron-deficient alkenes encompasses a variety of heteroaromatics, including pyridine, (benzo)thiazole, and benzoxazole, as well as α,β-unsaturated esters and amides. Impressively, the coupling of radical cations with aryl alkynes demonstrated remarkable regioselectivity, thereby facilitating the synthesis of rare α-aryl vinyl phosphine oxides.

Metal-catalyzed Markovnikov-type selective hydrofunctionalization of terminal alkynes

Metal-catalyzed highly Markovnikov-type selective hydrofunctionalization of terminal alkynes provides a straightforward and atom-economical route to access 1,1-disubstituted alkenes, which have a wide range of applications in organic synthesis. However, the highly Markovnikov-type selective transformations are challenging due to the electronic and steric effects during the addition process. With the development of metal-catalyzed organic synthesis, different metal catalysts have been developed to solve this challenge, especially for platinum group metal catalysts. In this perspective, we review homogeneous metal-catalyzed Markovnikov-type selective hydrofunctionalization of terminal alkynes according to the classified element types as well as reaction mechanisms. Future avenues for investigation are also presented to help expand this exciting field.

Nucleophiles Target the Tungsten Center Over Acetylene in Biomimetic Models

Inspired by the first shell mechanism proposed for the tungstoenzyme acetylene hydratase, the electrophilic reactivity of tungsten-acetylene complexes [W(CO)(C2H2)(6-MePyS)2] (1) and [WO(C2H2)(6-MePyS)2] (2) was investigated. The biological nucleophile water/hydroxide and tert-butyl isocyanide were employed. Our findings consistently show that, regardless of the nucleophile used, both tungsten centers W(II) and W(IV), respectively, are the preferred targets over the coordinated acetylene. Treatment of 2 with aqueous NaOH led to protonation of coordinated acetylene to ethylene, pointing toward the Brønsted basic character of the coordinated alkyne instead of the anticipated electrophilic behavior. In cases involving isocyanides as nucleophiles, the attack on the W(II) center of 1 took place first, whereas the W(IV) complex 2 remained unchanged. These experiments indicate that the direct nucleophilic attack of W-coordinated acetylene by water, as some computational studies of acetylene hydratase propose, is unlikely to occur.

Regio- and stereoselective access to highly substituted vinylphosphine oxides via metal-free electrophilic phosphonoiodination of alkynes

In general, the P-centered ring-opening of quaternary phosphirenium salts (QPrS) predominantly leads to hydrophosphorylated products, while the C-centered ring-opening is primarily confined to intramolecular nucleophilic reactions, resulting in the formation of phosphorus-containing cyclization products instead of difunctionalized products generated through intermolecular nucleophilic processes. Here, through the promotion of ring-opening of three-member rings by iodine anions and the quenching of electronegative carbon atoms by iodine cations, we successfully synthesize β-functionalized vinylphosphine oxides by the P-addition of QPrS intermediates generated in situ. Multiple β-iodo-substituted vinylphosphine oxides can be obtained with exceptional regio- and stereo-selectivity by reacting secondary phosphine oxides with unactivated alkynes. In addition, a variety of β-functionalized vinylphosphine oxides converted from C-I bonds, especially the rapid construction of benzo[b]phospholes oxides, demonstrates the significance of this strategy.

Efficient synthesis of α-amino-vinylphosphine oxides from alkyl nitriles via manganese-catalyzed phosphinoenamination

A protocol for the synthesis of α-amino-vinylphosphine oxides by phosphinoenamination reaction between alkyl nitriles and phosphine oxides was developed. The combination of Mn(OAc)2 as a Lewis acid and guanidine as a Lewis base was found to be an efficient catalytic system for this reaction. A series of alkyl nitriles and phosphine oxides are compatible with this conversion, furnishing the desired products in up to 95% yield under mild conditions. Furthermore, this method demonstrates the capability of gram-scale synthesis.

CuH-Catalyzed Reductive Coupling of Nitroarenes with Phosphine Oxides for the Direct Synthesis of Phosphamides

A CuH-catalyzed reductive coupling of nitroarenes with phosphine oxides is developed, which produces a series of phosphamides in moderate to excellent yields with good functional group tolerance. Gram-scale synthesis and late-stage modification of nitro-aromatic functional molecule niclosamide are also successfully conducted. The mechanism study shows that the nitro group is transformed after being reduced to nitroso and a nucleophilic addition procedure is involved during the reaction.

Bis(2,2,2 trifluoroethyl) Phosphonate as a Convenient Precursor for the Synthesis of H-Phosphonates

A microwave-assisted synthesis of dialkyl and cyclic H-phosphonates via bis(2,2,2 trifluoroethyl) phosphonate (BTFEP) is described. This method enables the synthesis of various cyclic H-phosphonates and hetero-substituted dialkyl H-phosphonates by simple alcoholysis under non-inert and additive-free conditions. Short reaction times and the requirement for only stoichiometric amounts of alcohol render this method attractive for synthetic applications.

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.

Synthesis of alkenylphosphine oxides via Tf2O promoted addition-elimination of ketones and secondary phosphine oxides

Herein, we describe an efficient method for the synthesis of alkenylphosphine oxides via a Tf2O promoted addition-elimination process. Various diarylphosphine oxides and alkylarylphosphine oxides react with ketones smoothly and produce alkenylphosphine oxides in moderate to excellent yields with abundant functional group compatibility. In addition, several transformations and applications of the product also demonstrate the potential value of the methodology.

Reductive Coupling of P(O)-H Compounds and Aldehydes for the General Synthesis of Phosphines and Phosphine Oxides

A novel strategy for the selective construction of a C(sp3)-P(III) or -P(V) bond from >P(O)-H compounds and aldehydes is disclosed. By using the H3PO3/I2 system, various secondary phosphine oxides could react with both aromatic and aliphatic aldehydes to afford valuable phosphines (isolated as sulfides) and phosphine oxides in good yields. This method features a wide substrate scope and simple reaction conditions and avoids the use of toxic halides and metals.

Zn-Catalyzed Dehydroxylative Phosphorylation of Allylic Alcohols with P(III)-Nucleophiles

A novel and efficient protocol for the synthesis of diarylallyl-functionalized phosphonates, phosphinates, and phosphine oxides through the zinc-catalyzed dehydroxylative phosphorylation of allylic alcohols with P(III)-nucleophiles via a Michaelis-Arbuzov-type rearrangement is reported. A broad range of allylic alcohols and P(III)-nucleophiles (P(OR)3, ArP(OR)2, and Ar2P(OR)) are well tolerated in this reaction, and the expected dehydroxylative phosphorylation products could be synthesized with good to excellent yields under the optimal reaction conditions. The reaction can be easily scaled up at a gram-synthesis level. Furthermore, through the step-by-step control experiments, kinetic study experiments, and 31P NMR tracking experiments, we acquired insights into the reaction and proposed the possible mechanism for this transformation.

Three-Component Direct Phosphorylation of Aldehydes and Alkylation of Ketones: Synthesis of γ-Ketophosphine Oxides under Acidic Conditions

An effective and economical acid-promoted three-component reaction for the construction of C-P and C-C bonds for the synthesis of γ-ketophosphine oxides with water as the only byproduct was developed. Detailed mechanistic experiments confirmed that the reaction proceeds by phospha-aldol elimination, in which a benzylic carbocation is generated from the phosphorylation of aldehydes, which then reacts with ketone enolates under acidic conditions.

A Simple and Practical Bis-N-Heterocyclic Carbene as an Efficient Ligand in Cu-Catalyzed Glaser Reaction

Conjugated diyne derivatives are important scaffolds in modern organic synthetic chemistry. Using the Glaser reaction involves the coupling of terminal alkynes which can efficiently produce conjugated diyne derivatives, while the use of a stoichiometric amount of copper salts, strong inorganic base, and excess oxidants is generally needed. Developing an environmentally friendly and effective method for the construction of symmetrical 1,3-diynes compounds by Glaser coupling is still highly desirable. In this study, we present an economical method for the production of symmetric diynes starting from various terminal acetylenes in a Glaser reaction. A simple and practical bis-N-heterocyclic carbene ligand has been introduced as efficient ligands for the Cu-catalyzed Glaser reaction. High product yields were obtained at 100 °C for a variety of substrates including aliphatic and aromatic terminal alkynes and differently substituted terminal alkynes including the highly sterically hindered substrate 2-methoxy ethynylbenzene or 2-trifluoromethyl ethynylbenzene and a series of functional groups, such as trifluoromethyl group, ester group, carboxyl group, and nitrile group. The established protocol is carried out in air under base-free condition and is operationally simple. These research work suggest that bis-N-heterocyclic carbene could also an appealing ligand for Glaser reaction and provide a reference for the preparation of symmetric 1,3-diynes in industrial filed.

Palladium-catalyzed Enantio- and Regioselective Ring-Opening Hydrophosphinylation of Methylenecyclopropanes

Transition metal-catalyzed hydrofunctionalization of methylenecyclopropanes (MCP) has presented a considerable challenge due to the difficult manipulation of regioselectivity and complicated reaction patterns. Herein, we report a straightforward Pd-catalyzed ring-opening hydrophosphinylation reaction of MCP via highly selective C-C bond cleavage. This allows for rapid and efficient access to a wide range of chiral allylic phosphine oxides in good yields and high enantioselectivities. Additionally, density functional theory (DFT) calculations were performed to elucidate the reaction mechanism and the origin of product enantioselectivity.

Nickel-Catalyzed Sodium Hypophosphite-Participated Direct Hydrophosphonylation of Alkyne toward H-Phosphinates

The traditional methods for the synthesis of phosphinate esters use phosphorus trichloride (PCl₃) as the phosphorous source, resulting in procedures that are often highly polluting and energy intensive. The search for an alternative approach that is both mild and environmentally friendly is a challenging, yet highly rewarding task in modern chemistry. Herein, we use an inorganic phosphorous-containing species, NaH₂PO₂, to serve as the source of phosphorous that participates directly in the nickel-catalyzed selective alkyne hydrophosphonylation reaction. The transformation was achieved in a multicomponent fashion and at room temperature, and most importantly, the H-phosphinate product generated is an advanced intermediate which can be readily converted into diverse phosphinate derivatives, including those bearing new P-C, P-S, P-N, P-Se, and P-O bonds, thus providing a complimentary method to classic phosphinate ester synthesis techniques.

Preparation of Vinylphosphonates from Ketones Promoted by Tf2O

An efficient triflic anhydride promoted phosphorylation of ketone was disclosed, and vinylphosphorus compounds were prepared under solvent- and metal-free conditions. Both aryl and alkyl ketones could perform smoothly to give vinyl phosphonates in high to excellent yields. In addition, the reaction was easy to carry out and easy to scale up. Mechanistic studies suggested that this transformation might involve nucleophilic vinylic substitution or a nucleophilic addition-elimination mechanism.

Carboxylic-Phosphoric Anhydrides as Direct Electrophiles for Decarbonylative Hirao Cross-Coupling of Carboxylic Acids: DFT Investigation of Mechanistic Pathway

In this anniversary issue, we present a DFT study of the mechanism of decarbonylative Hirao cross-coupling of carboxylic-phosphoric anhydrides to afford aryl phosphonates. Traditionally, the direct activation of carboxylic acids to participate in decarbonylative couplings is performed in the presence of carboxylic acid anhydride activators. We discovered that direct dehydrogenative decarbonylative phosphorylation of benzoic acid can be performed in high yield via dehydrogenative and decarbonylative coupling in the presence of phosphite as dual activating and nucleophilic reagent, enabling direct decarbonylative phosphorylation. Control studies demonstrated that carboxylic-phosphoric anhydride (acyl phosphate) is an intermediate in this process. DFT studies were conducted to gain insight into this decarbonylative process and compare the selectivity of C-O and P-O bond activations. Considering the utility of ubiquitous carboxylic acids, this alternative activation pathway may find applications in decarbonylative coupling of carboxylic acids for the synthesis of valuable molecules in organic synthesis.

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.

Computational Study Revealing the Mechanistic Origin of Distinct Performances of P(O)-H/OH Compounds in Palladium-Catalyzed Hydrophosphorylation of Terminal Alkynes: Switchable Mechanisms and Potential Side Reactions

Pd-catalyzed hydrophosphorylation of alkynes with P(O)-H compounds provided atom-economical and oxidant-free access to alkenylphosphoryl compounds. Nevertheless, the applicable P(O)-H substrates were limited to those without a hydroxyl group except H₂P(O)OH. It is also puzzling that Ph₂P(O)OH could co-catalyze the reaction to improve Markovnikov selectivity. Herein, a computational study was conducted to elucidate the mechanistic origin of the phenomena described above. It was found that switchable mechanisms influenced by the acidity of substrates and co-catalysts operate in hydrophosphorylation. In addition, potential side reactions caused by the protonation of Pd^II-alkenyl intermediates with P(O)-OH species were revealed. The regeneration of an active Pd(0) catalyst from the resulting Pd(II) complexes is remarkably slower than the hydrophosphonylation, while the downstream reactions, if possible, would lead to phosphorus 2-pyrone. Further analysis indicated that the side reactions could be suppressed by utilizing bulky substrates or ligands or by decreasing the concentration of P(O)-OH species. The presented switchable mechanisms and side reactions shed light on the co-transformations of P(O)-H and P-OH compounds in the Pd-catalyzed hydrophosphorylation of alkynes, clarify the origin of the distinct performances of P(O)-H/OH compounds, and provide theoretical clues for expanding the applicable substrate scope of hydrophosphorylation and synthesizing cyclic alkenylphosphoryl compounds.

Copper-catalyzed stereo- and regioselective hydrophosphorylation of terminal alkynes: scope and mechanistic study

Herein, a protocol for copper-catalyzed highly stereo- and regioselective hydrophosphorylation of terminal alkynes to E-alkenylphosphorus compounds was well developed. It represents a general and practical hydrophosphorylation method, of which diarylphosphine oxide, dialkylphosphine oxide and dialkyl phosphite all had effective P(O)H parts to react with different types of terminal alkynes. Contrary to previous air-sensitive reports, all the reactions proceeded well under air. This methodology is quite attractive owing to the high stereo- and regioselectivity, good functional group tolerance, scalability and facile late-stage derivatization of some natural product derivatives and commercially available herbicides. What's more, investigations on the reaction mechanism with deuterium-labeling experiments and DFT studies firstly disclosed the deprotonation-protonation equilibrium of terminal alkynes and P(O)H part during the catalytic hydrophosphorylation process.

Ni-catalyzed asymmetric hydrophosphinylation of conjugated enynes and mechanistic studies

The catalytic asymmetric synthesis of P-stereogenic phosphines is an efficient strategy to access structurally diverse chiral phosphines that could serve as organocatalysts and ligands to transition metals and motifs of antiviral drugs. Herein, we describe a Ni catalyzed highly regio and enantioselective hydrophosphinylation reaction of secondary phosphine oxides and enynes. This method afforded a plethora of alkenyl phosphine oxides which could serve as valuable precursors to bidentate ligands. A new type of mechanism was discovered by combined kinetic studies and density functional theory (DFT) calculations, which was opposed to the widely accepted Chalk-Harrod type mechanism. Notably, the alkene moiety which could serve as a directing group by coordinating with the Ni catalyst in the transition state, plays a vital role in determining the reactivity, regio and enantioselectivity.

Palladium-catalyzed hydroboration reaction of unactivated alkynes with bis (pinacolato) diboron in water

A highly efficient and mild palladium-catalyzed hydroboration of unactivated internal alkynes in water is described. Both aryl- and alkyl-substituted alkynes proceeded smoothly within the reaction time to afford the desired vinylboronates in moderate to high yields. Bis (pinacolato) diboron was used to afford α- and β-hydroborated products in the presence of HOAc. These reactions showed high reactivities and tolerance, thus providing a promising method for the synthesis of alkenyl boron compounds.

Palladium-Catalyzed Tail-to-Tail Reductive Dimerization of Terminal Alkynes to 2,3-Dibranched Butadienes

The palladium-catalyzed tail-to-tail reductive dimerization of terminal alkynes is described for the first time. Aromatic terminal alkynes bearing diverse and sensitive functional groups as well as aliphatic terminal alkynes are efficiently transformed to 2,3-dibranched butadienes. The key to achieve a selective tail-to-tail reductive dimerization reaction is to control appropriately the acidity of the reaction solution, which is accomplished by a combined use of pivalic acid and para-toluenesulfonic acid. The tail-to-tail reductive dimerization reaction is proposed to proceed via a cationic alkenyl palladium intermediate under acidic conditions.

A highly selective turn-on fluorescence probe with large Stokes shift for detection of palladium and its applications in environment water and living cells

Nowadays, palladium has been widely used in many fields, which facilitates all aspects of our life. However, it may cause water and soil pollution and bring irreversible damage to the environment and organisms. Developing a fluorescence probe for rapid, highly sensitive and selective detection of palladium is still a poser. In this work, we designed and synthesized a novel fluorescence probe (RHS) for specific detection of palladium. Based on Pd⁰-mediated Tsuji-Trost reaction, the fluorescence probe was constructed by a rhodol derivative as thefluorophore and an allyl carbonate moiety as the specific palladium reactive site. The probe displayed excellent properties for detecting palladium, such as high selectivity and sensitivity, rapid response (20 min) and large Stokes shift (155 nm). The detection limit was determined to be as low as 0.140 μM with a linear range from 20 to 80 μM. After addition of palladium in RHS solution, the color of the solution turned from yellow to blue, indicating palladium could be monitored by the naked eyes. Moreover, probe RHS was successfully applied to palladium detection in environmental water samples. Importantly, with low cytotoxicity and good biocompatibility, the probe could monitor palladium in living cells.

Rh-Catalyzed Regio- and Enantioselective Allylic Phosphinylation

Transition-metal-catalyzed branched and enantioselective allylic substitution of monosubstituted precursors with carbon, nitrogen, oxygen, sulfur, and fluoride nucleophiles has been well-established. However, such a selective carbon-phosphorus bond formation has not been realized probably due to the catalyst deactivation by the strong coordinating nature of phosphinylating reagents. Herein, we report a Rh-catalyzed highly regio- and enantioselective synthesis of allylic phosphine oxides in the presence of a chiral bisoxazoline-phosphine ligand. The application of α-hydroxylalkylphosphine oxides to keep the low concentration of the secondary phosphine oxides is essential for the high yields. The addition of diphenyl phosphoric acid was found to not only activate allylic alcohols but also accelerate the carbon-phosphorus bond formation.

Visible-light-initiated regio- and stereoselective C(sp2)–H phosphorylation of enamides under transition-metal-free conditions

A visible-light-induced stereo- and regioselective phosphorylation of enamides with phosphine oxides under transition-metal-free conditions has been disclosed.

Manganese(I) Catalyzed Alkenylation of Phosphine Oxides Using Alcohols with Liberation of Hydrogen and Water

Herein, a catalytic cross-coupling of methyldiphenylphosphine oxide with arylmethyl alcohols leading to the alkenylphosphine oxides is reported. A manganese pincer catalyst catalyzes the reactions, which provides exclusive formation of trans-alkenylphosphine oxides. Mechanistic studies indicate that reactions proceed via aldehyde intermediacy and the catalyst promotes the C═C bond formation. Reactions are facilitated by dearomatization, and aromatization metal-ligand cooperation operates in catalyst. Use of abundant base metal catalyst and formation of water and H₂ as the only byproducts make this catalytic protocol sustainable and environmentally benign.

Nickel-Catalyzed Asymmetric Synthesis of P-Stereogenic Vinyl Phosphines

Addition reaction to alkynes is an efficient strategy for constructing valuable alkenyl compounds. However, the elusive regioselectivity has been a persistent challenge. In the context of hydrophosphination reaction which could afford valuable P-stereogenic phosphines, the control of enantioselectivity as well as regioselectivity were especially tricky. Here, we highlighted our recent work on the nickel-catalyzed regio- and enantioselective hydrophosphination of unactivated alkynes with in situ generated secondary phosphines.

1 Introduction

2 Hydrophosphination of Alkynes

3 Derivatization Reactions

4 Mechanism Research

5 Summary and Outlook

An efficient catalytic method for hydrophosphination of heterocumulenes with diethylzinc as precatalyst without a solvent

Commercially available compound ZnEt₂ acts as an efficient precatalyst for the solvent-free hydrophosphinations of heterocumulenes using Ph₂PH as reagent. As far as we knew, this has been not reported in group 12 metal catalyzing reactions. A suggested mechanism of this reaction is explored, and the intermediate [{Ph₂PC(NⁱPr)₂}ZnEt]₂ is obtained and characterized by a single-crystal X-ray structural analysis.