Diarylphosphine Oxides Research Articles

Application of Oxazaborolidine Catalysts (CBS) on Enantioselective 1,4-Addition of Diarylphosphine Oxides to α,β-Unsaturated Thioesters.

Here, we report the first catalytic enantioselective 1,4-addition of diarylphosphine oxides to α,β-unsaturated thioesters. Importantly, the most common and commercial oxazaborolidine (CBS) was employed as a catalyst for its new application without being activated by strong protonic acids or Lewis acids and led to the chiral thioesters in excellent yields and enantioselectivities. Furthermore, this method features mild reaction conditions (room temperature and air-insensitive), good substrate tolerance, and easy scalability.

A Study of the Bisphosphonic Derivatives from the Pudovik Reaction of Dialkyl α-Oxophosphonates and >P(O)H Reagents: X-ray Structure and Bioactivity.

New hydroxy-methylenebisphosphonic derivatives were prepared with different P-functions. The outcome of the reaction of α-oxophosphonates (YC(O)P(O)(OR)2) and dialkyl phosphites or diarylphosphine oxides depended on the Y substituent of the oxo-compound, the nature of the P-reagent and the amount of the diethylamine catalyst. Starting from dimethyl α-oxoethylphosphonate, in the presence of 5% of diethylamine, the corresponding Pudovik adduct was the single product. While using 40% of the catalyst, the rearranged species with the >P(O)-O-CH-P(O)< skeleton was the exclusive component. A similar reaction of α-oxobenzylphosphonate followed the rearrangement protocol. X-ray crystallography revealed not only the spatial structures of the three products, but also an intricate pattern evolving from the interplay of slight chemical differences, solvent inclusion and disorder as well as H-bridge patterns, which invite further investigation. In vitro activity of the compounds was assessed on different tumor cell cultures using end-point-type cell tetrazolium-based measurements. These structure-activity studies revealed a cytostatic effect for four rearranged derivatives containing aromatic units. One of them had a pronounced effect on MDA-MB 231 and Ebc-1 cells, showing IC50 = 37.8 and 25.9 µM, respectively.

Microwave-Assisted Palladium Acetate-Catalyzed C-P Cross-Coupling of Arylboronic Acids and >P(O)H Reagents in the Absence of the Usual Mono- and Bidentate P-Ligands: Mechanistic Insights.

A less-studied halogen-free variation of the Hirao reaction involving the coupling of arylboronic acids with >P(O)H reagents, such as diarylphosphine oxides, diethyl phosphite, and ethyl phenyl-H-phosphinate, was investigated in detail using Pd(OAc)2 as the catalyst precursor and applying some excess of the P-reagent to supply the ligand via its trivalent tautomeric (>P-OH) form. The optimum conditions (1.2 equiv of the P-reagent, 135-150 °C, and air) were explored for the synthesis of diaryl-phenylphosphine oxides, aryl-diphenylphosphine oxides, diethyl arylphosphonates, ethyl diphenylphosphinate, and two bisphosphinoyl derivatives. In the reaction of 4-chlorophenyl- or 3-chlorophenylboronic acid with Ph2P(O)H, triphenylphosphine oxide was also formed as a byproduct. Theoretical calculations suggested that the catalytic cycle of the P-C coupling of PhB(OH)2 with Ph2P(O)H is different from that of the usual cross-coupling reactions. It comprises the addition of a phenyl anion and then the tautomeric form >P-OH of the >P(O)H reagent to the Pd2+ catalyst complex. This is then followed by reductive elimination affording Ph3PO that is accompanied with the conversion of Pd2+ to Pd0. There is a need for a subsequent stoichiometric oxidation of Pd(0) by molecular oxygen. The spontaneous formation of the self-assembling ligands around the Pd2+ center from the >P(O)H reactant plays a crucial role in the mechanism and promotes the efficiency of the catalyst.

Metal‐Free One‐Pot Tandem Construction of C4‐Phosphorylated Phthalazin‐1(2H)‐ones under Visible‐Light Photoredox Catalysis

AbstractVisible‐light photoredox‐catalyzed metal‐free one‐pot tandem regioselective synthesis of C4‐phosphorylated phthalazin‐1(2H)‐ones from arylhydrazines, 2‐formylbenzoic acids with diarylphosphine oxides is described. This three‐component transformation occurs smoothly under mild conditions, providing regiospecific access to various phosphorylated products in 73–91% yield. The efficacy of the current catalysis arises from the use of organic 1,2,3,5‐tetrakis(carbazol‐9‐yl)‐4,6‐dicyanobenzene (4CzIPN) as the photocatalyst and cheap K2S2O8 as the oxidant.

Magnesium-Catalyzed Regioselective Hydrophosphinylation of Alkenes with Diarylphosphine Oxides

Magnesium-Catalyzed Regioselective Hydrophosphinylation of Alkenes with Diarylphosphine Oxides

Photocatalytic Synthesis of 6-Phosphorylated Phenanthridines from 2-Isocyanobiphenyls via Radical C−P and C−C Bond Formation

A mild, efficient, photocatalytic synthesis of 6-phosphorylated phenanthridines via tandem radical addition/cyclization/aromatization of 2-isocyanobiphenyls with diarylphosphine oxides is reported. The method features operational simplicity in metal-free conditions, using low-cost Rose Bengal as a catalyst and sustainable air as a terminal oxidant at room temperature and providing the desired products in moderate to good yields.

Unraveling Ultralong Phosphorescence in Ar2PO(H): n(O) → σ*(P-C) Transitions in Ar2PO(H) Stabilize Triplet States Better than n(P) → σ*(P-C) in Ar3P

Herein, we report the crystallization-induced persistent room-temperature phosphorescence (CIpRTP) characteristics of simple diarylphosphine oxides 1, 2, and 3. Under ambient conditions, crystalline solids of 1, 2, and 3 show photoluminescence (PL) lifetime of more than 100 ms. At 77 K, they exhibit a PL lifetime of nearly a second. Replacing one of the aryl moieties in Ar3P═O with hydrogen creates more space for intermolecular interactions in Ar2P═O (H); consequently, the latter shows better PL quantum yield (PLQY) than the former. The PLQYs of these compounds are tuned systematically by varying the steric perturbation around the phosphorus center. Detailed analysis of the crystal structure of these compounds revealed that the intermolecular interactions play a crucial role in stabilizing the triplet state in the solid state and bestowing them with CIpRTP. Thin films of these compounds do not show pRTP, further affirming that the intermolecular interactions indeed play a crucial role in stabilizing the triplet state. In the solution state, these compounds show ultraviolet fluorescence (λem ≈ 305 nm) with a small Stokes shift of ∼3200 cm–1 and narrow bandwidth (FWHM: 37, 35, and 33 nm for 1, 2, and 3, respectively). The calculated SOC (⟨T1|Ĥ|S0⟩) matrix element for 1, 2, and 3 is significantly lower than the value estimated for triarylphosphines; thus, the former show ultralong phosphorescence compared to the latter. Furthermore, the n(O) → σ*(P-C) transition plays a crucial role in controlling the optical features in these compounds.

Photoinduced Homolysis of the Ni–P Bond via Ligand to Metal Charge Transfer for C–P Bond Formation in Nickel Catalysis

Photoinduced homolysis of NiII-carbon and -heteroatom bonds has been well studied for carbon-heteroatom couplings, but homolysis of the NiII-P bond is still undisclosed. Herein, we describe the homolysis of NiII-P bonds via ligand to metal charge transfer to access active nickel(I) complexes and phosphorus-centered radicals under visible-light irradiation for C-P couplings of diaryl phosphine oxides with aryl bromides. Experimental studies demonstrated that visible light enabled homolysis of the NiII-P bond and the NiI/NiIII self-sustained cycle was involved in C-P bond formation. Furthermore, homolysis of the NiII-P bond can be applied to the hydrophosphination of [1.1.1]propellane in single-nickel photocatalysis.

Silver-catalyzed radical bisphosphonation reaction of maleimides with diarylphosphine oxides

A silver-catalyzed bisphosphonate reaction of substituted maleimides with various diarylphosphine oxides was developed. This methodology provided an efficient strategy to prepare phosphorus–containing succinimide derivatives with satisfactory yields. The reaction exhibited mild reaction conditions and good functional group compatibilities. The radical species induced pathway was also demonstrated by mechanistic studies.

Electrochemical Oxidative Phosphorylations of Glycine Derivatives with R2P(O)−H‐Containing Compounds via C(sp3)−H Functionalisation

Herein, we report the development of transition-metal-catalyst- and external-oxidant-free electrochemical cross-coupling hydrogen-evolution chemistry involving glycine amides and diarylphosphine oxides. A broad range of biologically active α-aminophosphonates was obtained in moderate to good yields in a clean and sustainable manner. Moreover, the TBAB (tetrabutylammonium bromide) electrolyte was recycled four times without obvious loss of reaction activity. Moreover, this protocol was performed on the gram scale under slightly modified electrolytic conditions or in combination with continuous flow microreactor technology. Control experiments were used to disclose a possible free-radical mechanism. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Chiral phosphoric acid-catalyzed enantioselective phosphinylation of 3,4-dihydroisoquinolines with diarylphosphine oxides

Chiral phosphorous-containing compounds are playing a more and more significant role in several different research fields. Here, we show a chiral phosphoric acid-catalyzed enantioselective phosphinylation of 3,4-dihydroisoquinolines with diarylphosphine oxides for the efficient and practical construction of a family of chiral α-amino diarylphosphine oxides with a diverse range of functional groups. The phosphine products are suitable for transforming to several kinds of chiral (thio)ureas, which might be employed as chiral ligands or catalysts with potential applications in asymmetric catalysis. Control and NMR tracking experiments show that the reaction proceeds via the tert-butyl 1-(tert-butoxy)-3,4-dihydroiso-quinoline-2(1H)-carboxylate intermediate, followed by C-P bond formation. Furthermore, computational studies elucidated that the hydrogen bonding strength between the phosphonate and isoquinolinium determines the stereoselectivity of the phosphinylation reaction.

An improved cobalt-catalysed alkoxycarbonylation of olefins using secondary phosphine oxide promotors

A cobalt-catalysed alkoxycarbonylation under mild conditions was conducted. Diaryl phosphine oxides (SPOs) are the key for performing this reaction with simple and stable cobalt(ii) salts as precursors, leading to advantages in practicability.

Mn-catalyzed electrooxidative radical phosphorylation of 2-isocyanobiaryls.

As an efficient and green synthesis method, the electrocatalysis hydrogen evolution coupling reaction has been widely used by chemists to realize the combining of two nucleophiles. In this work, an alternative method to synthesize 6-phosphorylated phenanthridines has been developed by synergistically utilizing electrocatalysis and Mn catalysis, with moderate to relatively good yields achieved. Mild and oxidant-free conditions make this synthetic method applicable in various settings.

Organoboron/iodide-catalyzed photoredox N-functionalization of NH-sulfoximines/sulfonimidamides.

An aminoquinolate diarylboron (AQDAB) and tetrabutylammonium iodide (TBAI) co-catalyzed photoredox process for N-functionalization of NH-sulfoximines/sulfonimidamides has been successfully developed. This protocol can afford the corresponding N-sulfenylated and N-phosphonylated products in good to excellent yields under conditions without metallic (photo)catalysts, external oxidants, or acidic/basic additives. A wide range of functional groups are tolerated, and the N-phosphonylated products of NH-sulfonimidamides have been reported for the first time.

Cobalt-catalyzed asymmetric phospha-Michael reaction of diarylphosphine oxides for the synthesis of chiral organophosphorus compounds

A cobalt-catalyzed imidazolyl-directed asymmetric phospha-Michael-type reaction for synthesizing chiral organophosphorus compounds is presented. This protocol features broad substrate scope, good functional group tolerance, and mild conditions.

Enantioselective 1,4-addition of diarylphosphine oxides to α,β-unsaturated ketones catalyzed by oxazaborolidines

A new application of oxazaborolidines in enantioselective phospha-Michael addition to α,β-unsaturated ketones under mild reaction conditions was developed and the possible mechanism is described.

Visible‐Light‐Driven Hydrophosphorylation of Azobenzenes Enabled by trans‐to‐cis Photoisomerization

AbstractA visible‐light‐driven hydrophosphorylation of azobenzenes with diarylphosphine oxides was successfully developed. The reaction proceeded smoothly under blue light irradiation at room temperature without any photocatalyst required, providing a mild approach for this transformation with new strategy. Of important note is that the visible light‐driven trans‐to‐cis photoisomerization of azobenzenes was found to be the key for the process of the reaction, highlighting this underestimated reactivity of azobenzenes in visible‐light‐promoted mechanism.magnified image

Copper-Catalyzed Radical Hydrazono-Phosphorylation of Alkenes.

An efficient copper-catalyzed radical hydrazono-phosphorylation of alkenes with hydrazine derivatives and diarylphosphine oxides is described. The reaction provides a general and convenient method toward the synthesis of diverse β-hydrazonophosphine oxides in satisfactory yields. Based on conducted mechanistic experiments, a mechanism involving Ag-catalyzed oxidative generation of phosphinoyl radicals and subsequent addition to alkenes followed by Cu-assisted hydrazonation is proposed. Moreover, the practicability of the reaction is successfully demonstrated by its successful application on a gram scale.

Visible-Light-Induced Cascade Cyclization of 3-(2-(Ethynyl)phenyl)quinazolinones to Phosphorylated Quinolino[2,1-b]quinazolinones.

3-(2-(Ethynyl)phenyl)quinazolinones were designed and synthesized as a class of novel and efficient skeletons for phosphorylation/cyclization reactions. Under visible light irradiation, a series of phosphorylated quinolino[2,1-b]quinazolinones (35 examples, up to 87% yield) were first synthesized from 3-(2-(ethynyl)phenyl)quinazolinones and diarylphosphine oxides by using 4CzIPN as a photocatalyst under mild conditions. This reaction was also applicable under sunlight irradiation. Moreover, the reaction efficiency could be significantly improved under continuous-flow conditions.

Copper-Catalyzed Stereoselective Radical Phosphono-hydrazonation of Alkynes.

A copper-catalyzed stereoselective phosphono-hydrazonation of terminal alkynes with alkyl carbazates and diarylphosphine oxides is described. This methodology provides facile access to a variety of β-hydrazonophosphine oxides in satisfactory yields. The reaction proceeds under mild conditions and exhibits good functional group tolerance. A mechanism featuring persulfate-mediated oxidative generation of phosphinoyl radicals and copper-assisted hydrazonation is proposed.