Bronsted Acid/Organic Photoredox Cooperative Catalysis: Easy Access to Tri- and Tetrasubstituted Alkenylphosphorus Compounds from Alcohols and P–H Species

Visible-Light-Induced Synthesis of Vinyl Sulfones via Decarboxylative Sulfonylation of Cinnamic Acids Using Sulfonylazides/p-Toluenesulfonylmethyl Isocyanide/β-Keto Sulfones

An efficient visible-light-induced synthesis of vinyl sulfones has been accomplished via decarboxylative sulfonylation of cinnamic acids using sulfonylazides, p-toluenesulfonylmethyl isocyanide, and β-keto sulfones as sulfonyl source, in the presence of inexpensive organic photocatalysts like rhodamine B and eosin Y. The reaction is facile, straightforward, and endowed with wide substrate scope and functional group tolerability.

Heteropolyacid-Catalyzed Phosphorylation of Secondary Aromatic Alcohols with H-Phosphine Oxides in DMC: A Simple Protocol for C-P Bond Formation

We successfully achieved the phosphorylation of secondary aromatic alcohols with H-phosphine oxides (less developed system) using phosphotungstic acid as a catalyst in dimethyl carbonate. The system was simple and environmentally friendly and showed better activity than traditional Lewis or Brønsted acids such as FeCl3, p-TsOH·H2O, etc., generating up to a 97% isolated yield. Control experiments indicated that the reaction did not occur through the radical pathway, and ethers and carbocation were the key intermediates in the pathway.

Dual Photoredox/Nickel-Catalyzed Dehydrative Difluoroalkylation of Benzyl Alcohols for the Synthesis of Allylic gem-Difluorides

A photoredox/Lewis acid cooperative catalytic system has been developed for the construction of Cvinyl-CRf bonds through the dehydrative difluoroalkylation of benzyl alcohols. A variety of allylic gem-difluorides could be obtained in moderate yields with good to excellent E/Z selectivity. In addition, several control experiments have been explored, and a possible mechanism was proposed for this process.

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.

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.

Visible-light-induced Direct 3-Ethoxycarbonylmethylation of 2-Aryl-2H-Indazoles in Water

A visible-light-driven Rhodamine B-catalyzed transition-metal-free 3-ethoxycarbonylmethylation of 2-aryl-2H-indazoles and imidazo[1,2-a]pyridines (40 examples) using commercially available α-bromoesters was realized in water. This protocol features sustainable, operational simplicity, mild reaction conditions, and...

Palladium-Catalyzed Cascade Difluoroalkylation and Phosphinoylation of 2-Vinyloxy Arylalkynes: Selective Synthesis of Difluoroalkyl-Containing Tetrasubstituted Alkenylphosphine Oxides

A Pd-catalyzed difluoroalkylation/cyclization/phosphinoylation of 2-vinyloxy arylalkynes with ethyl difluoroiodoacetate and diarylphosphine oxides has been successfully developed. This reaction allows the formation of C_sp3-CF₂, C_sp3-C_sp2, and C_sp2-P(O) bonds in one step, providing a straightforward route to difluoroalkyl-containing tetrasubstituted alkenylphosphine oxides with complete stereoselectivities under mild conditions.

Markovnikov-addition of H-phosphonates to terminal alkynes under metal- and solvent-free conditions

An addition of H-phosphonates to aryl alkynes was realized under solvent- and metal-free conditions, affording Markovnikov-selective α-vinylphosphonates in moderate to good yields. A wide range of aryl alkynes could be applied for the reaction. A tentative mechanism of addition-substitution was proposed based on in situ 31P {1H} NMR studies.

Visible-Light-Induced Photocatalytic Synthesis of β-Keto Dithiocarbamates via Difunctionalization of Styrenes

A facile photocatalyzed strategy for difunctionalization of styrenes in the presence of CS₂ and amines providing β-keto dithiocarbamates has been developed. In the case of 4-nitrostyrene and 2-vinylpyridine, however, only 2-arylethylthiocarbamates are interestingly formed without the aid of photoredox catalysis/TBHP.

TfOH-Catalyzed Phosphinylation of 2,3-Allenols into γ-Ketophosphine Oxides

The first facile and efficient acid-catalyzed direct coupling of a wide range of unprotected 2,3-allenols with arylphosphine oxides was developed, offering a general, one-step approach for the synthesis of structurally diverse γ-ketophosphine oxides accompanied by concurrent C-P/C═O bond formation with remarkable functional group tolerance and complete atom-economy under metal- and additive-free conditions. Mechanistic studies showed that this transformation involved a rearrangement and a phospha-Michael reaction.

Visible-Light-Induced Metal-Free Synthesis of 2-Phosphorylated Thioflavones in Water

The introduction of phosphorus functional groups into the skeleton of thioflavones is an attractive task and of great significance. Herein, a metal-free visible-light-induced radical cascade cyclization was developed for the preparation of 2-phosphorylated thioflavones from methylthiolated alkynones and phosphine oxides. In water as a green reaction medium, a large number of such 2-phosphorylated thioflavones were prepared, catalyzed by 4CzIPN [1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene] under visible-light irradiation. These reactions could be performed at ambient temperature and feature simple operation, wide reaction scope, and recyclability of aqueous media.

The construction of three C–P bonds of P-stereogenic tertiary phosphines containing (l)-menthyl

A wide range of R_P or S_P-(l)-menthyl-containing SPOs were prepared via the reaction of 1,1′-bi(2-naphthol) derived phosphonite with a metallic reagent with excellent yield and dr.

A Ba/Pd Catalytic System Enables Dehydrative Cross-Coupling and Excellent E-Selective Wittig Reactions

A Ba/Pd cooperative catalysis system was developed to enable the dehydrative cross-coupling of allylic alcohols with P-ylides to occur directly and promote a subsequent Wittig reaction in one pot. A variety of multisubstituted 1,4-dienes were isolated in good to excellent yields with broad P-ylides (stabilized by both ester and ketone carbonyl groups) and aldehyde (aliphatic and aromatic) substrates with excellent E selectivity.

Proton-Coupled Electron Transfer Enables Tandem Radical Relay for Asymmetric Copper-Catalyzed Phosphinoylcyanation of Styrenes

A tandem radical relay strategy was realized for the first Cu(I)-catalyzed enantioselective phosphinocyanation of styrenes. In this reaction, ^tBuOOSiMe₃ generated in situ from ^tBuOOH serves as a radical initiator to trigger t-butoxy radical production upon oxidization of L*Cu(I) species via proton-coupled-electron transfer (PCET) pathway, which leads to sequential phosphinoyl radical and benzyl radical formations. The resultant β-cyanodiarylphosphine oxides could be easily converted to a series of chiral γ-amino phosphine ligands.

Visible light-mediated CP bond formation reactions

Organophosphorus compounds have attracted continuous attention in materials science, agrochemical and pharmaceutical fields due to their unique bioactivities. Thus, the development of novel and robust manners for the construction new CP bond has therefore gained great interests in synthetic organic chemistry. Because of their intrinsic sustainability and green chemistry character, visible light-induced photoredox catalysis has been widely applied in the construction of new chemical bonds, including the formation of CP bond. In this review, we summarized recent achievements in CP bond formation reactions initiated by visible light-induced photoredox catalysis, which mainly focusing on the discussion of reaction design and the mechanism.

Silver-mediated radical phosphorylation/cyclization of N-allylbenzamides to access phosphoryl-substituted dihydroisoquinolones

A silver-mediated phosphorylation/cyclization of N-allylbenzamides with phosphine oxides for the synthesis of phosphoryl-substituted dihydroisoquinolones was developed.

Direct C-OH/P(O)-H dehydration coupling forming phosphine oxides

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.

Barium-catalyzed C–OH/P–H dehydrative cross-coupling for C–P bond construction

A barium-catalyzed C–OH/P–H dehydrative cross-coupling protocol for the construction of C–P bonds was developed in an environmentally benign manner.