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Direct phosphorylation of benzylic C–H bonds with secondary phosphine oxides was first realized. The reaction was performed in organo/aqueous biphasic system and under transition metal-free conditions, proceeding via the cross dehydrogenative coupling.

Herein reported is the facial modification of tertiary phosphine boranes R3PBH3 by selective cleaving the P-Ph bond by sodium in which the phosphide borohydride R2PNa(BH3) is quantitatively generated and could be easily quenched by electrophiles to furnish a series of new phosphine boranes in high yields. Graphical abstract

For the first time, H3PO3 was used as both the reducing reagent and the promotor in the reductive benzylation reactions with aryl aldehydes. By using a H3PO3/I2 combination, various aromatic aldehy...

The Pd-catalyzed Michaelis–Arbuzov rearrangement of triaryl phosphites to produce the corresponding arylphosphonates in good to excellent yields is disclosed. In comparison to the traditional metho...

Herein, we highlight advances in the phosphorylation of readily available carboxylic acids and their derivatives forming synthetically important P(O)–sp3C, P(O)–sp2C, and P(O)–spC bonds, with an emphasis on the results demonstrated since 2010. This review examines the challenges associated with the use of this strategy for the synthesis of organophosphorus compounds and details advances in the design of catalytic systems that suppress these problems thus resulting in notable progress. Mechanistic details are discussed where available.1 Introduction2 Formation of P(O)–sp3C Bonds3 Formation of P(O)–sp2C Bonds4 Formation of P(O)–spC Bonds5 Outlook and Conclusion

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.

The preparation, application, and reaction mechanism of sodium phosphide R2PNa and other alkali metal phosphides R2PM (M = Li and K) have been studied. R2PNa could be prepared, accurately and selec...

We report a new method for the synthesis of acylphosphine oxides by the direct coupling of hydrogen phosphine oxides and acyl chlorides mediated by chlorosilanes. This new protocol is greener and safer, because it precludes the generation of volatile haloalkanes and the use of oxidants employed in the conventional methods. Moreover, moisture-unstable acylphosphine oxides that are difficult to prepare via the conventional methods can be generated using this new method.

The three-component reactions of α-amino acids, p-quinone monoacetals (or p-quinol ethers), and diarylphosphine oxides have been developed for the synthesis of 3-(diarylphosphinyl) anilides and N-aryl-2-diarylphosphinylpyrrolidines. The transformations may involve the in situ generation of conjugated azomethine ylides or 2-azaallyl anion species from the reaction of α-amino acids and p-quinone monoacetals, which are further trapped by diarylphosphine oxides.

Despite the importance of P-chiral organophosphorus compounds in asymmetric catalysis, transition metal-catalyzed methods for accessing P-chiral phosphine derivatives are still limited. Herein, a catalytic enantioselective method for the synthesis of P-stereogenic alkenylphosphinates is developed through asymmetric hydrophosphorylation of alkynes. This process is demonstrated for a wide range of racemic phosphinates and leads to diverse P-stereogenic alkenylphosphinates directly.

For over half a century, thousands of tons of triphenylphosphine oxide Ph3P(O) have been produced every year from the chemical industries as a useless chemical waste. Here we disclose efficient transformations of Ph3P(O) with cheap resource-abundant metallic sodium finely dispersed in paraffin oil. Ph3P(O) can be easily and selectively transformed to three reactive organophosphorus intermediates—sodium diphenylphosphinite, sodium 5H-benzo[b]phosphindol-5-olate and sodium benzo[b]phosphindol-5-ide—that efficiently give the corresponding functional organophosphorus compounds in good yields. These functional organophosphorus compounds are difficult to prepare but highly industrially useful compounds. This may allow Ph3P(O) to be used as a precious starting material for highly valuable phosphorus compounds. As a byproduct of organic syntheses including the Wittig, Staudinger, and Mitsunobu reactions, triphenylphosphine oxide is often not recycled. Here a transformation of the waste product with metallic sodium to three organophosphorous compounds is presented.

Despite the importance of P-chiral organophosphorus compounds in asymmetric catalysis, transition metal-catalyzed methods for accessing P-chiral phosphine derivatives are still limited. Herein, a catalytic enantioselective method for the synthesis of P-stereogenic alkenylphosphinates is developed through asymmetric hydrophosphorylation of alkynes. This process is demonstrated for a wide range of racemic phosphinates and leads to diverse P-stereogenic alkenylphosphinates directly., A catalytic enantioselective synthesis of P-stereogenic alkenylphosphinates is developed through asymmetric hydrophosphorylation. This process is demonstrated on racemic phosphinates and leads to diverse P-stereogenic alkenylphosphinates directly.

By using I2 or I2/H3PO3 system, various alkenes and alkynes were converted to the corresponding alkyl and alkenyl iodides in good yields. In the presence of I2, alkynes could be di-iodinated using H2O as the solvent in air at room temperature. This method also features the simple work-up procedure since the pure product could be obtained by extraction. Additionally, for the first time, combining with the non-toxic and cheap phosphonic acid H3PO3, alkenes and alkynes were also hydroiodinated successfully, which provides a simple and practical approach for synthesis of organoiodides.

By using PCl3 as the chlorinating reagent, various carboxylic acids are converted into the corresponding acid chlorides in good yields. This method features high atom efficiency in which nearly all three chlorine atoms of PCl3 are used in the chlorination. Moreover, the work-up procedure is simple since the major side product is phosphonic acid [HP(O)(OH)2] which is non-toxic and easily removed by filtration. A possible mechanism is proposed in this paper.

Water is found able to determine the selectivity of Bronsted acid-catalyzed C–O cleavage reactions of trialkyl phosphites: with water, the reaction quickly takes place at room temperature to afford quantitative yields of H-phosphonates; without water, the reaction selectively affords alkylphosphonates in high yields, providing a novel halide-free alternative to the famous Michaelis–Arbuzov reaction. This method is general as it can be readily extended to phosphonites and phosphinites and a large scale reaction with much lower loading of the catalyst, enabling a simple, efficient, and practical preparation of the corresponding organophosphorus compounds. Experimental findings in control reactions and substrate extension as well as preliminary theoretical calculation of the possible transition states all suggest that the monomolecular mechanism is preferred.

The zinc triflate-catalyzed highly regioselective C-P cross coupling reaction of p-quinol ethers with secondary phosphine oxides is reported. The reaction provides a facile alternative method for the synthesis of 2-phosphinylphenols in good to high yields. Mechanistically, zinc triflate may serve as an oxophilic σ-Lewis acid to activate the C-O bond in p-quinol ether first. Then the regioselective attack of the phosphorus nucleophile at the α-carbon position takes place to form the C-P bond and give the product. In addition, α-alkynyl substituted p-quinol ethers also react with secondary phosphine oxides in the same reaction mode to give 6-alkynyl 2-phosphinylphenols in the presence of the zinc catalyst.

For the first time, H

Sodium exhibits better efficacy and selectivity than Li and K for converting Ph3P(O) to Ph2P(OM). The destiny of PhNa co-generated is disclosed. A series of alkyl halides R4X and aryl halides ArX all react with Ph2P(ONa) to produce the corresponding phosphine oxides in good to excellent yields.

A "wet" process and two "dry" processes for converting phosphonate esters to phosphonic acids catalyzed by a Bronsted acid have been developed. Thus, in the presence of water, a range of alkyl-, alkenyl-, and aryl-substituted phosphonates can be generally hydrolyzed to the corresponding phosphonic acids in good yields catalyzed by trifluoromethyl sulfonic acid (TfOH) at 140 °C (the wet process). On the other hand, with specific substituents of the phosphonate esters, the conversion to the corresponding phosphonic acids can be achieved under milder conditions in the absence of water (the dry process). Thus, the conversion of dibenzyl phosphonates to the corresponding phosphonic acids took place smoothly at 80 °C in toluene or benzene in high yields. Moreover, selective conversion of benzyl phosphonates RP(O)(OR')(OBn) to the corresponding mono phosphonic acids RP(O)(OR')(OH) can also be achieved under the reaction conditions. The dealkylation via the generation of isobutene of di-tert-butyl phosphonate, and the related catalysis by TfOH took place even at room temperature to give the corresponding phosphonic acids in good to high yields. Nafion also shows high catalytic activity for these reactions. By using Nafion as the catalyst, phosphonic acids could be easily prepared on a large scale via a simple process.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

This study details the oxidation of α-hydroxy(2,4,6-trimethylbenzyl)diphenylphosphine oxide (α-HDPO) to diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) by choosing the proper MnO2 as oxidant. In addition, the equilibrium of α-HDPO and 2,4,6-trimethylbenzaldehyde (MesCHO) was discussed.

A direct phosphorylation of the sp3C-CN bond catalyzed by a nickel catalyst is disclosed. A wide range of primary nitriles readily coupled with secondary phosphine oxides to produce the corresponding phosphorylated products in high yields. As a key step, this new method was applied to the synthesis of anticancer drug Combretastatin-A4, significantly shortening its synthetic path.

Three-component reactions can directly convert three reactants into the desired products in one pot and thus greatly shorten the synthetic path. Recently, transition-metal catalysis has been applied in the difunctionalization of alkenes and remarkable progress has been achieved to facilitate the construction of a wide range of functional molecules with high atom- and step-economic efficiency. This Focus Review highlights recent advances in this field.

Radical hydrophosphorylation of aliphatic terminal alkynes with H-phosphine oxides can produce the corresponding anti-Markovnikov alkenylphosphorus adducts in moderate yields. This method is a cleaner approach for the preparation of the corresponding alkenylphosphine oxides, since it avoids the use of a metal catalyst that sometimes is difficult to remove from the products.

A novel, transition-metal-free phosphorylation of cinnamic acids with P(O)H compounds has been developed via radical-promoted decarboxylation under mild conditions. This method provides simple, efficient, and versatile access to valuable ( E)-alkenylphosphine oxides in satisfactory yields with a wide variety of substrates.

We carried out a comprehensive study on the generality, scope, limitations, and mechanism of the palladium-catalyzed hydrophosphorylation of alkynes with P(O)-H compounds (i.e., H-phosphonates, H-phosphinates, secondary phosphine oxides, and hypophosphinic acid). For H-phosphonates, Pd/dppp was the best catalyst. Both aromatic and aliphatic alkynes, with a variety of functional groups, were applicable to produce the Markovnikov adducts in high yields with high regioselectivity. Aromatic alkynes showed higher reactivity than aliphatic alkynes. Terminal alkynes reacted faster than internal alkynes. Sterically crowded H-phosphonates disfavored the addition. For H-phosphinates and secondary phosphine oxides, Pd/dppe/Ph2P(O)OH was the catalyst of choice, which led to highly regioselective formation of the Markovnikov adducts. By using Pd(PPh3)4 as the catalyst, hypophosphinic acid added to terminal alkynes to give the corresponding Markovnikov adducts. Phosphinic acids, phosphonic acid, and its monoester were not applicable to this palladium-catalyzed hydrophosphorylation. Mechanistic studies showed that, with a terminal alkyne, (RO)2P(O)H reacted, like a Bronsted acid, to selectively generate the α-alkenylpalladium intermediate via hydropalladation. On the other hand, Ph(RO)P(O)H and Ph2P(O)H gave a mixture of α- and β-alkenylpalladium complexes. In the presence of Ph2P(O)OH, hydropalladation with this acid took place first to selectively generate the α-alkenylpalladium intermediate. A subsequent ligand exchange with a P(O)H compound gave the phosphorylpalladium intermediate which produced the Markovnikov adduct via reductive elimination. Related intermediates in the catalytic cycle were isolated and characterized.

A Cu(MeCN)4BF4-catalyzed dehydrative reaction of 1-(2-hydroxyphenyl)propargyl alcohols with diarylphosphine oxides has been developed to provide an efficient synthesis of phosphorylated benzofurans in good to high yields. In the presence of a catalytic amount of an organic base, a variety of H-phosphonates and H-phosphinates can also be employed as good substrates to produce the corresponding products in moderate yields. The reaction has significant economical and ecological advantages since the formation of a new Csp3−P bond and the benzofuran framwork could both be achieved using an inexpensive copper catalyst with water produced as the sole byproduct. The synthetic transformations of the product have also been demonstrated.

A highly selective Ph3P-mediated C(α)–P coupling reaction of quinone monoacetals with secondary phosphine oxides is developed to provide an effective method for the synthesis of a wide array of ortho-phosphinylphenols in good to excellent yields. This protocol can be adopted for scale-up synthesis directly from cheap and abundant phenols, and the products can be easily obtained in high yields by simple filtration without the use of organic extraction or chromatography.

A Ni-catalyzed hydrogenation of C-O compounds with sodium formate is developed. Various esters, i.e. aryl, alkenyl, benzyl pivalates, and even the aryl ethers, were efficiently reduced with a loading of nickel catalysts down to 0.5 mol%. Reactive functional groups such as C-C double bonds, carbonyl, CN, MeS and halogen groups are tolerable. This reaction can be used for the modification of complex molecules and carried out at a large scale.

A t-BuONa-mediated C-OH/P(O)-H cross dehydration coupling to produce alkylphosphine oxides is developed. This reaction employed readily available alcohols and P(O)-H compounds as the starting materials, providing an efficient alternative method for constructing sp3 C-P bonds. A reasonable reaction path involving dehydration and subsequent regio-selective hydrophosphorylation of the resulting alkenes was proposed.

Herein reported is the convenient and efficient strategy for the preparation of binaphthyl-based phosphines through direct modification to the commercially available 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl (BINAP) with sodium. In the absence of 15-crown-5-ether, a cyclic sodium dinapthylphospholide intermediate is mainly generated. With 15-crown-5-ether, P-Ph bonds are selectively cleft by Na to produce binaphthyl-based disodium phosphides. The mechanism of selective formation of sodium dinapthylphospholide or binaphthyl-based disodium phosphides is proposed.

Trimethyl phosphine was used as an efficient catalyst for the addition of P(O)-H compounds to electron-deficient alkenes. The addition reactions were generally conducted using a catalytic amount of Me3P under mild reaction conditions. Both 1 to 1 and 1 to 2 adducts were obtained.

The cadmium(II) chloride-catalyzed dehydrative C−P cross-coupling reaction of propargyl alcohols with diarylphosphine oxides is reported. Several propargyl alcohols including those bearing the sterically demanding tert-butyl group at the triple bond terminus can be used as good substrates in the reaction to produce the corresponding allenylphosphine oxides in good to high yields in acetonitrile at 100 °C. The reaction can also be easily scaled up to a gram-scale synthesis. A mechanism study indicates that the reaction may proceed through a process of propargylic substitution to generate phosphonite intermediates followed by [2,3] sigmatropic rearrangement to produce the allenyl products, rather than through a common allenylative substitution resulting from P-nucleophilicity.

The highly regioselective nucleophilic ring opening of propargyl epoxides by P(O)H compounds based on a Ag catalyst is reported. A variety of P(O)H compounds including H-phosphonates, H-phosphinates and diarylphosphine oxides can be used to produce 4-phosphoryl 2,3-allenols under mild conditions. The stereoselective synthesis of 1-phosphoryl 1,3-butadienes from 4-phosphoryl 2,3-allenols and organoboronic acids via a Pd-catalyzed coupling reaction is also described.

A variety of P -stereogenic organophosphorus compounds can be readily prepared by stereoretentive addition. The PMe 3 -catalyzed addition of optically active (−)MenthylO(Ph)P(O)H compounds to electron deficient alkenes occur stereospecifically, to produce the corresponding P -stereogenic adducts in high yields. By simply removing the volatiles under vacuum, spectroscopically pure products can be obtained. The present method provides a salt-free clean process for the preparation of P -chiral organophosphorus compounds.

An air-induced double addition of diphenyl phosphine oxide to various alkynes is reported. This reaction can proceed efficiently under metal- and solvent-free conditions, and is a clean and practically useful method for the preparation of the valuable 1,2-bisphosphorylethanes.

In sharp contrast to the transition metal-catalyzed diboration of alkynes with diboron species such as B 2 pin 2 , which affords vicinal cis -diborated alkenes, the organophosphine-catalyzed addition of B 2 pin 2 to alkynes proceeds under metal-free conditions upon photoirradiation to give the corresponding vicinal trans -diborated alkenes with good stereoselectivity. For example, the photoinduced diboration of 1-octyne with B 2 pin 2 in the presence of tris( o -methylphenyl)phosphine afforded 1,2-diborated octene with excellent trans selectivity ( trans / cis =95/5). The influence of various organophosphines on the diboration is described in detail. The diboration does not occur in the dark or in the absence of an organophosphine catalyst. Moreover, ESR (electron spin resonance) measurements of the reaction mixture revealed a radical species around g =2.003, supporting a radical pathway for the organophosphine-catalyzed diboration. In addition, the photoinduced cis to trans isomerization of vicinal cis -diborated alkenes in the presence/absence of organophosphines is discussed.

For the first time, by using H3PO3/I2 system, various benzyl chlorides, bromides and iodides were dehalogenated successfully. In the presence of H3PO3, benzyl halides underwent electrophilic substitution reactions with electron-rich arenes, leading to a broad range of diarylmethanes in good yields. These transformations feature green, cheap reducing reagents and metal-free conditions. A possible mechanism was proposed.

Supplemental material, Supporting_information_PDF for Atom-efficient chlorination of benzoic acids with PCl3 generating acyl chlorides by Jing Xiao and Li-Biao Han in Journal of Chemical Research

By photoredox-catalysis, alkylation/aryl C-H cyclization of readily available alkynylphosphine oxides towards benzo[b]phospholes has been realized under metal- and oxidant-free conditions at room temperature. This reaction readily incorporates various functionalized alkyl groups into the benzo[b]phosphole skeletons, representing a mild and versatile tool for the preparation of valuable phosphole compounds.

By introducing trimethylsilyl chloride (TMSCl), the pentavalent phosphoryl P(V) compounds such as triphenylphosphine oxides, secondary phosphine oxides etc., were readily converted to the corresponding R2P(OTMS) intermediates, that can further react efficiently with an electrophile R’X or with a nucleophile R’Li to produce the corresponding trivalent phosphines R2PR’. Chiral phosphines could also be obtained stereospecifically by this strategy.

The novel poly(vinyldiphenylphosphine) could be easily prepared by using the reactions of the cheap poly(vinyl chloride) with sodium phosphides. Poly(vinyldiphenylphosphine) is soluble in common solvents while its corresponding phosphine oxide is hardly soluble in the solvents. Taking advantage of this different solubility, poly(vinyldiphenylphosphine) could be used as a soluble phosphinopolymer for the Wittig reactions. The reactions could take place efficiently to produce the corresponding olefins while the isolation of the products were simple since the resulted poly(vinyldiphenylphosphine oxide) was not soluble in the solvent and could be easily removed by filtration.

A nickel-catalyzed phosphorylation of aryl triflates with P(O) H compounds is disclosed. This reaction can proceed smoothly under a mild reaction condition, producing the corresponding aryl phosphorus compounds in good to high yields.