Diphenylphosphino Propane Research Articles

DFT study on mechanism of nickel-catalyzed decarbonylative reductive alkylation of aroyl fluorides with alkyl bromides

The mechanism of the nickel-catalyzed decarbonylative reductive alkylation of aroyl fluorides with alkyl bromides is investigated using density functional theory calculations. The calculation result shows that the reaction mechanism involves sequential steps of C–F bond oxidative addition, decarbonylation, alkyl radical addition, C(sp2)–C(sp3) reductive elimination to afford the product, single electron transfer (SET) and reduction by Zn to regenerate the initiating complex. And the step of C–F bond oxidative addition was found to be the rate-determining step. The decarbonylation should occur before the alkyl radical addition. The effects of 1,3-bis(diphenylphosphino)propane (DPPP) ligand and different substrates on the reactivity were also analyzed. These calculation results disclosed the detailed reaction mechanism and shed lights on some ambiguous suggestions from experiments.

Molybdenum-catalyzed hydrogenation of carbon dioxide, bicarbonate, and inorganic carbonates to formates.

Herein, we report the hydrogenation of carbon dioxide to sodium formate catalyzed by low-valent molybdenum phosphine complexes. The 1,3-bis(diphenylphosphino)propane (DPPP)-based Mo complex was found to be an efficient catalyst in the presence of NaOH affording formate with a TON of 975 at 130 °C in THF/H2O after 24 h utilizing 40 bar (CO2 : H2 = 10 : 30) pressure. The complex was also active in the hydrogenation of sodium bicarbonate and inorganic carbonates to the corresponding formates. Mechanistic investigation revealed that the reaction proceeded via an intermediate formato complex.

Rational design of Lewis base molecules for stable and efficient inverted perovskite solar cells.

Lewis base molecules that bind undercoordinated lead atoms at interfaces and grain boundaries (GBs) are known to enhance the durability of metal halide perovskite solar cells (PSCs). Using density functional theory calculations, we found that phosphine-containing molecules have the strongest binding energy among members of a library of Lewis base molecules studied herein. Experimentally, we found that the best inverted PSC treated with 1,3-bis(diphenylphosphino)propane (DPPP), a diphosphine Lewis base that passivates, binds, and bridges interfaces and GBs, retained a power conversion efficiency (PCE) slightly higher than its initial PCE of ~23% after continuous operation under simulated AM1.5 illumination at the maximum power point and at ~40°C for >3500 hours. DPPP-treated devices showed a similar increase in PCE after being kept under open-circuit conditions at 85°C for >1500 hours.

Phosphine-Protected Atomically Precise Silver–Gold Alloy Nanoclusters and Their Luminescent Superstructures

Superstructures made by assemblies of metal nanoclusters (NCs) have gained interest due to their atomic precision and exciting photophysical properties. Although there are some reports of cluster-assembled materials of NCs protected with thiols, the preparation of stable thiol-free analogs is largely unexplored due to the poor stability of such structures. Herein, we report the synthesis of phosphine-protected alloy NCs of silver with varying gold doping and superstructures of such systems. We show that alloying of phosphine-protected silver clusters with gold results in comparatively more stable clusters than weakly ligated hydride- and phosphine-coprotected silver clusters. Two new Ag–Au alloy cluster series, [Ag11–xAux(DPPB)5Cl5O2]2+, where x = 1–10 (Ag11–xAux in short), and [Ag15–xAux(DPPP)6Cl5]2+, where x = 1–6 (Ag15–xAux in short), have been synthesized using two different phosphines, 1,4-bis(diphenylphosphino)butane (DPPB) and 1,3-bis(diphenylphosphino)propane (DPPP), respectively. These alloy clusters possess aggregation-induced emission (AIE) property, which was unexplored till now for phosphine-protected silver clusters. A visibly nonluminescent methanol solution of these clusters showed strong red luminescence in the presence of water due to the formation of cluster-assembled spherical hollow superstructures without any template. A solvophobic effect along with π···π and C–H···π interactions in the ligand shell make the alloy NCs assemble compactly within the hollow spheres. The assembly makes them highly emitting due to the restriction of intramolecular motion. The emissive states of the alloy clusters show a many-fold increase in lifetime in the presence of water. Femtosecond transient absorption studies revealed the lifetime of the excited-state charge carriers in their monomeric and aggregated states. Apart from enriching the limited family of phosphine-protected silver alloy NCs, this work also provides a new strategy to build a controlled assembly of NCs with tailored luminescence. These materials could be new phosphors for applications in composites, sensors, thin films, and photonic materials.

Copper-Catalyzed Ligand-Controlled Selective Borocarbonylation of α-Substituted Styrenes Toward β-Boryl Aldehydes and Cyclopropyl Boronate Esters

Copper-Catalyzed Ligand-Controlled Selective Borocarbonylation of α-Substituted Styrenes Toward β-Boryl Aldehydes and Cyclopropyl Boronate Esters

Isoquercitrin Attenuates Osteogenic Injury in MC3T3 Osteoblastic Cells and the Zebrafish Model via the Keap1-Nrf2-ARE Pathway.

Isoquercitrin (IQ) widely exists in natural products, with a variety of pharmacological activities. In this study, the anti-apoptotic and antioxidative activities of IQ were evaluated. IQ showed protective activity against 2, 2′-azobis [2-methylpropionamidine] dihydrochloride (AAPH)-induced cell damage, as well as a marked reduction in reactive oxygen species (ROS). The evidence of IQ regulating Keap1-Nrf2-ARE and the mitochondrial-mediated Caspase 3 pathway were found in the MC3T3 osteoblastic cell line. Furthermore, IQ significantly decreased ROS production, apoptosis, and lipid peroxidation in AAPH-treated 72 h post-fertilization (hpf) zebrafish, as observed via DCFH-DA, acridine orange (AO), and a 1,3-bis(diphenylphosphino) propane (DPPP) probe, respectively. In AAPH-treated 9 day post-fertilization (dpf) zebrafish, IQ strongly promoted osteogenic development, with increased concentrations by calcein staining, compared with the untreated group. In a molecular docking assay, among all signal proteins, Keap1 showed the strongest affinity with IQ at −8.6 kcal/mol, which might be the reason why IQ regulated the Keap1-Nrf2-ARE pathway in vitro and in vivo. These results indicated that IQ promotes bone development and repairs bone injury, which is valuable for the prevention and treatment of bone diseases.

Synthesis of N,O-Chelating Hydrazidopalladium Complexes from 1,2-Bis(trifluoroacetyl)hydrazine

N,O-chelating dicarbonylhydrazido-palladium complexes were synthesized by treatment of 1,2-bis(trifluoroacetyl)hydrazine with a mixture of a Pd(0) source, [Pd(dba)2] (DBA = dibenzylideneacetone), and four-electron donors including 1,3-bis(diphenylphosphino)propane (DPPP), N,N,N’,N’-tetramethylethylenediamine (TMEDA), and two equivalents of triphenylphosphine. The same products from DPPP and TMEDA could be obtained alternatively by using Pd(OAc)2 through deprotonation of the diacylhydrazine. The five-membered chelate structure was confirmed by NMR spectra and X-ray crystal structure determination. The X-ray structures indicate that the products are formally considered as Pd(II) complexes with a hydrazido(2–) ligand. In the case of the triphenylphosphine-coordinated complex, a fluxional behavior in dichloromethane-d2 was observed by variable temperature NMR experiments, possibly due to structural changes between the square planar and pseudo-tetrahedral geometries.

Rhodium-Catalyzed Carbonylative Synthesis of Aryl Salicylates from Unactivated Phenols.

A rhodium-catalyzed carbonylative transformation of unactivated phenols to aryl salicylates is described. This protocol is characterized by utilizing 1,3-rhodium migration as the key step to provide direct access to synthesize o-hydroxyaryl esters. Various desired aryl o-hydroxybenzoates were produced in moderate to excellent yields with bis(dicyclohexylphosphino)ethane (DCPE) as the ligand. Interestingly, diphenyl carbonate was formed as the main product when 1,3-bis(diphenylphosphino)propane (DPPP) was used as the ligand. A plausible reaction mechanism is proposed.

In Situ Synthesis of Neutral Dinuclear Rhodium Diphosphine Complexes [{Rh(diphosphine)(μ2‐X)}2]: Systematic Investigations

AbstractAs the workhorses for many applications, neutral dimeric μ2‐X‐bridged diphosphine rhodium complexes of the type [{Rh(diphosphine)(μ2‐X)}2] (X=Cl, OH) are usually prepared in situ by the addition of diphosphine ligands to the rhodium complex [{Rh(diolefin)(μ2‐X)}2] (diolefin=cyclooctadiene (cod) or norbornadiene (nbd)) or [{Rh(monoolefin)2(μ2‐Cl)}2] (monoolefin=cyclooctene (coe) or ethylene (C2H4)). The in situ procedure has been investigated for the diphosphines 2,2′‐bis(diphenylphosphino)‐1,1′‐binaphthyl (BINAP), 5,5′‐bis(diphenylphosphino)‐4,4′‐bi‐1,3‐benzodioxole (SEGPHOS), 5,5′‐bis[di(3,5‐xylyl)phosphino]‐4,4′‐bi‐1,3‐benzodioxole (DM‐SEGPHOS), 5,5′‐bis[di(3,5‐di‐tert‐butyl‐4‐methoxyphenyl)phosphino]‐4,4′‐bi‐1,3‐benzodioxole (DTBM‐SEGPHOS), 2,2′‐bis(diphenylphosphino)‐1,1′‐dicyclopentane (BICP), 1‐[2‐(diphenylphosphino)ferrocenyl]ethyldi‐tert‐butylphosphine (PPF‐PtBu2), 1,1′‐bis(diisopropylphosphino)ferrocene (DiPPF), 1,2‐bis(diphenylphosphino)ethane (DPPE), 1,2‐bis(o‐methoxyphenylphosphino)ethane (DIPAMP), 4,5‐bis(diphenylphosphinomethyl)‐2,2‐dimethyl‐1,3‐dioxalane (DIOP), 1,2‐bis(2,5‐dimethylphospholano)benzene (Me‐DuPHOS), 1,4‐bis(diphenylphosphino)butane (DPPB), and 1,3‐bis(diphenylphosphino)propane (DPPP); the resulting complexes have been characterized by 31P NMR spectroscopy and, in most cases, also by X‐ray analysis. Depending on the diphosphine ligand, the solvent, the temperature, and the rhodium precursor, species other than the desired one [{Rh(diphosphine)(μ2‐X)}2] are formed, for example, [(diolefin)Rh(μ2‐Cl)2Rh(diphosphine)], [Rh(diphosphine)(diolefin)]+, [Rh(diphosphine)2]+, and [Rh(diphosphine)(diolefin)(Cl)]. The results clearly show that the in situ method commonly applied for precatalyst preparation cannot be regarded as an optimal strategy for the formation of such neutral [{Rh(diphosphine)(μ2‐X)}2] complexes.

New pentacoordinated rhodium species as unexpected products during the in situ generation of dimeric diphosphine-rhodium neutral catalysts.

Dimeric rhodium complexes of the type [Rh(PP)(μ2 -Cl)]2 (PP=diphosphine) are often used as precatalysts and are generated "in situ" from the corresponding diolefin complexes by exchange of the diene with the desired diphosphine. Herein, we report that the "in situ" procedure also leads to unexpected monomeric pentacoordinated neutral complexes of the type [RhCl(PP)(diolefin)], for the first time herein characterized by NMR spectroscopy and X-ray crystallography for the ligands 1,4-bis(diphenylphosphino)propane (DPPP), 1,4-bis(diphenylphosphino)butane (DPPB), and 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (BINAP). The pentacoordinated complexes are in equilibrium with the dimeric target compound [Rh(PP)(μ2 -Cl)]2 . The equilibrium is influenced by the rhodium-diolefin precursor, the solvent and the temperature. Based on the results of NMR and UV/Vis spectroscopic analysis (kinetics) it could be shown that the pentacoordinated complex [RhCl(PP)(diolefin)] may arise both from the "in situ"-generated neutral complex [Rh(PP)(μ2 -Cl)] by reaction with the free diolefin and, more surprisingly, directly from [Rh(diolefin)(μ2 -Cl)]2 and the diphosphine.

Pd‐Catalyzed Carbonylative α‐Arylation of Aryl Bromides: Scope and Mechanistic Studies

Reaction conditions for the three-component synthesis of aryl 1,3-diketones are reported applying the palladium-catalyzed carbonylative α-arylation of ketones with aryl bromides. The optimal conditions were found by using a catalytic system derived from [Pd(dba)2] (dba=dibenzylideneacetone) as the palladium source and 1,3-bis(diphenylphosphino)propane (DPPP) as the bidentate ligand. These transformations were run in the two-chamber reactor, COware, applying only 1.5 equivalents of carbon monoxide generated from the CO-releasing compound, 9-methylfluorene-9-carbonyl chloride (COgen). The methodology proved adaptable to a wide variety of aryl and heteroaryl bromides leading to a diverse range of aryl 1,3-diketones. A mechanistic investigation of this transformation relying on 31P and 13C NMR spectroscopy was undertaken to determine the possible catalytic pathway. Our results revealed that the combination of [Pd(dba)2] and DPPP was only reactive towards 4-bromoanisole in the presence of the sodium enolate of propiophenone suggesting that a [Pd(dppp)(enolate)] anion was initially generated before the oxidative-addition step. Subsequent CO insertion into an [Pd(Ar)(dppp)(enolate)] species provided the 1,3-diketone. These results indicate that a catalytic cycle, different from the classical carbonylation mechanism proposed by Heck, is operating. To investigate the effect of the dba ligand, the Pd0 precursor, [Pd(η3-1-PhC3H4)(η5-C5H5)], was examined. In the presence of DPPP, and in contrast to [Pd(dba)2], its oxidative addition with 4-bromoanisole occurred smoothly providing the [PdBr(Ar)(dppp)] complex. After treatment with CO, the acyl complex [Pd(CO)Br(Ar)(dppp)] was generated, however, its treatment with the sodium enolate led exclusively to the acylated enol in high yield. Nevertheless, the carbonylative α-arylation of 4-bromoanisole with either catalytic or stoichiometric [Pd(η3-1-PhC3H4)(η5-C5H5)] over a short reaction time, led to the 1,3-diketone product. Because none of the acylated enol was detected, this implied that a similar mechanistic pathway is operating as that observed for the same transformation with [Pd(dba)2] as the Pd source.

A Bidentate Ligand Immobilized on Silica via a Tripodal Linker Unit: Preparation and Application to Suzuki–Miyaura Coupling

Abstract A new tripodal linker unit was synthesized and is expected to enable the robust immobilization of bidentate ligands such as 1,3-bis(diphenylphosphino)propane (DPPP) onto silica supports. It was subsequently used to anchor a palladium–DPPP complex onto ordered mesoporous silica, and the resulting catalyst showed moderate activity for the Suzuki–Miyaura coupling reaction of aryl chloride with phenylboronic acid. The catalyst was recycled three times without a significant loss in activity and with minimal leaching of palladium after the reaction.

The Conversion of Furans into Phosphinines

The [4+2] cycloadducts between furan compounds and a methylenechlorophosphane pentacarbonyltungsten complex are converted into the corresponding 2-hydroxy- or 2-bromophosphinine complexes by treatment with BBr(3) and triethylamine. The X-ray crystal structure of the parent 2-phosphaphenol complex shows that the hydroxy substituent is coplanar with the ring and that the conjugation between the π lone pair of electrons on the oxygen atom and the ring leads to lengthening of the P-C(OH) bond. This complex is methylated at the phosphorus atom by methyl iodide with disruption of the ring aromaticity. The complex is further silylated, acylated, and triflated at the oxygen atom with retention of the aromatic structure, and decomplexation by 1,2-bis(diphenylphosphino)propane (DPPE) leads to the free parent 2-phosphaphenol. The comparison of the X-ray crystallographic structural analysis of the 2-bromophosphinine complex with an earlier structure of the analogous 2-chlorophosphinine complex suggests that 2-bromo species is a better ligand than 2-chlorophosphinine. When the [4+2] adducts are treated with BBr(3) and water, a 2-hydroxy-3-bromo-1,2,3,6-tetrahydrophosphinine derivative is obtained, which yields a seven-membered 2,1-phosphaoxepin when treated with an amine.

Diversity-Oriented Synthesis Based on the DPPP-Catalyzed Mixed Double-Michael Reactions of Electron-Deficient Acetylenes and β-Amino Alcohols

In this study, we prepared oxizolidines through 1,3-bis(diphenylphosphino)-propane (DPPP)–catalyzed mixed double-Michael reactions of β-amino alcohols with electron-deficient acetylenes. These reactions are very suitable for the diversity-oriented parallel syntheses of oxizolidines because: (i) they are performed under mild metal-free conditions and (ii) the products are isolated without complicated work-up. To demonstrate the applicability of mixed double-Michael reactions for the preparation of five-membered-ring heterocycles, we prepared 60 distinct oxazolidines from five β-amino alcohols and 12 electron-deficient acetylenes. We synthesized 36 of these 60 oxazolidines in enantiomerically pure form from proteinogenic amino acid–derived β-amino alcohols.

Benzoheterocycle Synthesis via Diphosphine Catalysis

The authors reported a method to construct seven different types of ­benzo-fused heterocyles 3 - indolines, dihydro­pyrrolopyridines, benzimidazolines, dihydrobenzo-3,1-oxazines, benzomorpholines, tetrahydroquinolines, and tetrahydroisoquinolines - from simple dinucleophiles 1 and electron-deficient acetylenes 2. Diphenyl­phosphinopropane (DPPP) is an efficient catalyst for this mixed double Michael addition process. In some cases the addition of the AcOH-NaOAc pair can further increase the yields.

Diphosphine-catalyzed mixed double-Michael reaction: a unified synthesis of indolines, dihydropyrrolopyridines, benzimidazolines, tetrahydroquinolines, tetrahydroisoquinolines, dihydrobenzo-1,4-oxazines, and dihydrobenzo-3,1-oxazines.

Seven different types of benzannulated N-heterocycles-indolines, dihydropyrrolopyridines, benzimidazolines, dihydrobenzo-3,1-oxazines, benzomorpholines, tetrahydroquinolines, and tetrahydroisoquinolines-can be obtained from simple dinucleophiles and electron-deficient acetylenes in one synthetic step. This powerful methodology was made possible through the use of diphenylphosphinopropane (DPPP) as the catalyst, with acetic acid and sodium acetate used as additives in some cases. The benzannulated N-heterocycles were isolated in excellent yields under mild metal-free conditions; they were purified without the need for aqueous workups.

Translation of helical chirality from polymer into monomer: supramolecular polymerization of a chirality-memory molecule with an asymmetric Pd(II) complex

A chirality-memorizing saddle-shaped porphyrin ( 1 2H ) with 3,5-dipyridylphenyl side arms at the opposite meso positions underwent supramolecular polymerization in CH 2Cl 2 with a chiral Pd(II) complex of 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl (Pd II(BINAP)), forming a ladder-shaped polymer ( 3 2H ) with a prevailing one-handed helical chirality. When this polymer was poured into AcOH containing 1,3-bis(diphenylphosphino)propane (DPPP) as a decomplexing agent, 3 2H was depolymerized in a stereochemically retentive way to give optically active 1 2H , hydrogen-bonded with AcOH. Although a cyclodimeric reference of 3 2H , formed from 2 2H having two 3-pyridylphenyl meso substituents in conjunction with Pd II(BINAP), behaved similar to 3 2H , the translation efficiency of helical chirality was lower than that in the case with 3 2H .

Cobalt-catalyzed cross-coupling reactions of alkyl halides with allylic and benzylic Grignard reagents and their application to tandem radical cyclization/cross-coupling reactions.

Details of cobalt-catalyzed cross-coupling reactions of alkyl halides with allylic Grignard reagents are disclosed. A combination of cobalt(II) chloride and 1,2-bis(diphenylphosphino)ethane (DPPE) or 1,3-bis(diphenylphosphino)propane (DPPP) is suitable as a precatalyst and allows secondary and tertiary alkyl halides--as well as primary ones--to be employed as coupling partners for allyl Grignard reagents. The reaction offers a facile synthesis of quaternary carbon centers, which has practically never been possible with palladium, nickel, and copper catalysts. Benzyl, methallyl, and crotyl Grignard reagents can all couple with alkyl halides. The benzylation definitely requires DPPE or DPPP as a ligand. The reaction mechanism should include the generation of an alkyl radical from the parent alkyl halide. The mechanism can be interpreted in terms of a tandem radical cyclization/cross-coupling reaction. In addition, serendipitous tandem radical cyclization/cyclopropanation/carbonyl allylation of 5-alkoxy-6-halo-4-oxa-1-hexene derivatives is also described. The intermediacy of a carbon-centered radical results in the loss of the original stereochemistry of the parent alkyl halides, creating the potential for asymmetric cross-coupling of racemic alkyl halides.

Base‐Free Oxidative Homocoupling of Arylboronic Esters.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Base-free oxidative homocoupling of arylboronic esters

Base-free oxidative homocoupling reaction of arylboronic esters has been found to proceed using a catalytic amount of a palladium–1,3-bis(diphenylphosphino)propane (DPPP) complex under an oxygen atmosphere, affording a variety of biaryls in modest to excellent yields. Even arylboronic esters bearing a base-sensitive functional group are applicable to the reaction.