Hydrophosphination Reaction Research Articles

Recent Advances in the Asymmetric Conjugate Addition Reactions of Phosphorus Nucleophiles to Electron-Deficient Alkenes

Chiral phosphines are very useful in the fields of asymmetric catalysis, pharmaceutical chemistry, and materials. These compounds have been used as ligands coordinated to transition metals or organocatalysts in various reactions to furnish optically active products with high efficiency. Asymmetric phosphorus-addition reaction can be utilized for the direct preparation of chiral phosphorus compounds. This review summarizes the recent progress in the field of enantioselective phosphorus-addition reactions. Several examples of transition metaland organocatalyst-promoted asymmetric hydrophosphination reactions of electron-deficient alkenes have been introduced.

Synthesis of vinylphosphines and unsymmetric diphosphines: iron-catalyzed selective hydrophosphination reaction of alkynes and vinylphosphines with secondary phosphines

Iron complex-catalyzed regioselective single hydrophosphination of terminal arylalkynes with secondary phosphines was achieved. Unsymmetric 1,2-bis(phosphino)ethanes with different phosphino groups were obtained by using our catalytic systems. The structures of the obtained vinylphosphine, unsymmetric 1,2-bis(phosphino)ethane, and iron catalyst precursors were confirmed by single crystal X-ray diffraction studies.

Recent Progress in Palladium-Catalyzed Asymmetric Hydrophos­phination

Asymmetric construction of P–C bonds is considered to be one of the most powerful methods for the preparation of chiral organophosphorus compounds. This review highlights recent progress in palladium-catalyzed asymmetric hydrophosphination reactions involving activated C=C bonds and diarylphosphines. The main catalytic systems employed for this protocol together with current substrate scope and mechanistic insights are described. 1 Introduction 2 Five-Membered CN/CP Palladacycle Catalyzed Protocols 3 PCP Pincer-Type Catalyst Based Protocols 4 NCN and PCN Pincers as Catalysts 5 Conclusion and Outlook

Palladacyclo-promoted asymmetric hydrophosphination reaction between diphenylphosphine and 2-ethynylpyridine

The organopalladium complex containing ortho-metalated (R)-[1-(dimethylamino) ethyl]naphthalene as the chiral auxiliary has been used as the chiral template to promote the asymmetric hydrophosphination reaction between diphenylphosphine and 2-ethynylpyridine in high selectivity under mild conditions. The double hydrophosphination reaction produces four stereoisomeric products in the ratio of 1:19.4:2.4:1.3. The naphthylamine auxiliary could be removed chemoselectively from the template products by treatment with concentrated hydrochloric acid to form the corresponding chiral dichloro complexes [(P–P)PdCl2]. The molecular structure and absolute configuration of the dichloro complex have been resolved by single-crystal X-ray crystallography. It confirms that the asymmetric diphosphines as P–P bidentate chelate on the chiral naphthylamine palladium templates. Finally, the enantiomerically pure diphosphine ligand with chirality on the carbon backbone can be readily liberated from the dichloro palladium complex as an air-sensitive solid by treatment of the complex with aqueous potassium cyanide in high yield.

An Approach to the Efficient Syntheses of Chiral Phosphino‐ Carboxylic Acid Esters

AbstractThe catalytic hydrophosphination reaction is one of the most sustainable chemical transformations today. Here, the palladium‐catalyzed asymmetric PH addition of diarylphosphines with N‐enoylbenzotriazoles and analogues is described. Chiral phosphine products are obtained in 100% atom economy and without cumbersome protection–deprotection manipulations. The obtained products can be subsequently transformed to bear various functionalities, including phosphino‐carboxylic esters which play critical roles in catalysis and as synthetic aids. Anti‐tumour activities of the corresponding gold‐phosphine complexes have been explored, contributing to existing chemotherapeutic research in cancer treatment.magnified image

A one-pot diastereoselective self assembly of C-stereogenic copper(I) diphosphine clusters.

C-chirogenic diphosphine-based clusters with 8-membered "chairlike" Cu4Cl4L2 and 12-membered "drumlike" Cu6Cl6L3 (L = diphosphine) frameworks were prepared in one-pot syntheses from chiral diphosphines, which were generated in situ via the double hydrophosphination reaction in excellent enantio- and diastereoselectivity. Excellent control over the final molecular architecture of the cluster (drum vs chair) could be achieved by the judicious selection of the source of the copper atoms employed in the synthetic protocol. Each cluster was characterized by single-crystal X-ray crystallography, (1)H, (13)C, and (31)P{(1)H} NMR spectroscopy. The synthesized clusters were found to exhibit catalytic activity in the hydroboration reaction of α,β-unsaturated enones with excellent yields albeit with low enantioselectivity.

Development of a novel chiral palladacycle and its application in asymmetric hydrophosphination reaction

A novel amine ligand, 1-(2,5-dichlorophenyl)-N,N-dimethylethanamine, was synthesized from 1-(2,5-dichlorophenyl)ethanone via a three step synthetic route. Direct ortho-palladation of the amine ligand with Pd(OAc)(2) gave the racemic dimeric complex in high yield. This racemic palladacycle was efficiently resolved through the formation of its (S)-prolinato derivatives. The resulting diastereomeric complexes were separated efficiently by column chromatography. In the solid state, the structure and absolute configuration of the two optically resolved palladium complexes were determined by single crystal X-ray crystallography. In solution, their absolute conformations were also investigated by the 2D (1)H-(1)H rotating frame nuclear Overhauser enhancement (ROESY) NMR spectroscopy. Both (R,R) and (S,S)-di-μ-chloro dimeric palladium complexes could be obtained chemoselectively by treating the corresponding prolinato derivatives with dilute hydrochloric acid. The amine auxiliary could be subsequently removed from the palladium center by treatment with concentrated hydrochloric acid. The enantiomerically pure palladacycle was used to promote the asymmetric hydrophosphination reaction between diphenylphosphine and dimethyl acetylenedicarboxylate. The (31)P{(1)H} NMR spectroscopy indicated that only one stereo-isomeric product was formed.

Theoretical mechanism for selective catalysis of double hydrophosphination of terminal arylacetylenes by an iron complex

The detailed mechanism of the double hydrophosphination of terminal arylacetylenes catalyzed by an iron complex was studied by density functional theory. The calculated results suggest that the reaction proceeds in three steps: active species generation, single hydrophosphination reaction (Cycle 1), double hydrophosphination reaction, viz., active species regeneration (Cycle 2). The results uncovered the selectivity of the iron complex for double hydrophosphination of terminal arylacetylenes. The symmetry of frontier molecular orbitals determines the effectiveness of the catalyst. We also discuss the formation mechanism of the single hydrophosphination product with Z configuration.

Heteroleptic Alkyl and Amide Iminoanilide Alkaline Earth and Divalent Rare Earth Complexes for the Catalysis of Hydrophosphination and (Cyclo)Hydroamination Reactions

[{N^N}M(X)(thf)n] alkyl (X=CH(SiMe3)2) and amide (X=N(SiMe3)2) complexes of alkaline earths (M=Ca, Sr, Ba) and divalent rare earths (Yb(II) and Eu(II) ) bearing an iminoanilide ligand ({N^N}(-)) are presented. Remarkably, these complexes proved to be kinetically stable in solution. X-ray diffraction studies allowed us to establish size-structure trends. Except for one case of oxidation with [{N^N}Yb(II){N(SiMe3)2}(thf)], all these complexes are stable under the catalytic conditions and constitute effective precatalysts for the cyclohydroamination of terminal aminoalkenes and the intermolecular hydroamination and intermolecular hydrophosphination of activated alkenes. Metals with equal sizes across alkaline earth and rare earth families display almost identical apparent catalytic activity and selectivity. Hydrocarbyl complexes are much better catalyst precursors than their amido analogues. In the case of cyclohydroamination, the apparent activity decreases with metal size: Ca>Sr>Ba, and the kinetic rate law agrees with R(CHA) =k[precatalyst](1)[aminoalkene](1). The intermolecular hydroamination and hydrophosphination of styrene are anti-Markovnikov regiospecific. In both cases, the apparent activity increases with the ionic radius (Ca<Sr<Ba) but the rate laws are different, and obey R(HA) =k[styrene](1)[amine](1)[precatalyst](1) and R(HP) =k[styrene](1)[HPPh2 ](0)[precatalyst](1), respectively. Mechanisms compatible with the rate laws and kinetic isotopic effects are proposed. [{N^N}Ba{N(SiMe3)2}(thf)2] (3) and [{N^N}Ba{CH(SiMe3)2}(thf)2] (10) are the first efficient Ba-based precatalysts for intermolecular hydroamination and hydrophosphination, and display activity values that are above those reported so far. The potential of the precatalysts for C-N and C-P bond formation is detailed and a rare cyclohydroamination-intermolecular hydroamination "domino" sequence is presented.

An ESR and DFT revisitation of phosphonitroxides prompted by an ineffective ESR approach to the hydrophosphination of alkynes

An ESR investigation of the thermal hydrophosphination of 1-hexyne by five different secondary phosphines and phosphine-boranes did not lead to the observation of any radical, but in the presence of the spin trap MNP (2-methyl-2-nitrosopropane) several phosphonitroxides were detected. The unusually low phosphorus splitting exhibited by some of these species could be accounted for on the basis of DFT calculations. Although two phospho-substituted vinyl nitroxides were identified in the course of the hydrophosphination reaction, they could not be considered as evidence of the direct involvement of phosphorus-centred radicals.

Insertion Reactions and Catalytic Hydrophosphination of Heterocumulenes using α-Metalated N,N-Dimethylbenzylamine Rare-Earth-Metal Complexes

The reactivity of homoleptic α-metalated dimethylbenzylamine lanthanide complexes (α-Ln(DMBA)3; Ln = La, Y; DMBA = α-deprotonated dimethylbenzylamine) was probed through a series of stoichiometric insertion and catalytic hydrophosphination reactions. Both rare-earth-metal species inserted 3 equiv of various carbodiimides to form the corresponding homoleptic amidinates. α-La(DMBA)3 was also found to be a useful precatalyst for the room-temperature hydrophosphination of heterocumulenes to form phosphaguanidines, phosphaureas, and phosphathioureas in moderate to excellent isolated yields. Furthermore, through a series of stepwise stoichiometric protonation and insertion reactions, a plausible mechanism for the hydrophosphination catalysis was investigated.

Synthesis of novel chiral monophosphine ligands derived from isomannide and isosorbide. Application to enantioselective hydrogenation of olefins

A new class of monophosphine ligands has been prepared from natural chirality renewable source, 1,4:3,6-dianhydrohexitol compounds, via a nucleophilic substitution process, or a hydrophosphination reaction involving microwave activation. These ligands have been evaluated for the rhodium-catalyzed enantioselective hydrogenation of olefins giving good conversion and enantioselectivity up to 95% and 96% ee, respectively.

Air‐Stable, Highly Fluorescent Primary Phosphanes

Air‐Stable, Highly Fluorescent Primary Phosphanes

Hydrophosphination of Carbodiimides Using Protic Heptaphosphide Cages: A Unique Effect of the Bimodal Activity of Protonated Group 15 Zintl Ions

Direct reaction of the hydrogen heptaphosphide dianion, [HP7]2– (1), with carbodiimides RN═C═NR (R = Dipp (2,6-diisopropylphenyl), iPr, Cy) afforded the amidine-functionalized Zintl ions [P7C(NHR)(NR)]2– (R = Dipp (2), iPr (3), and Cy (4)). The bimodal activity of 1, which contains both negatively charged phosphide vertices alongside “electron-precise” phosphine-like nuclei allows for the direct hydrophosphination of the carbodiimides without need for an external proton source. Further reaction of the bis(2,6-diisopropylphenyl)amidine-functionalized cluster 2 with a proton source such as [NH4][BPh4] or [H(OEt2)2][BArF4] affords the protonated monoanionic species [HP7C(NHDipp)(NDipp)]− (5). As with 1, species 5 also has bimodal character, and additional hydrophosphination reactions are possible by reacting 5 with RN═C═NR to yield the bis-functionalized monoanions {[P7[C(NHDipp)(NDipp)][C(NHR)(NR)]}− (R = Dipp (6), iPr (7), and Cy (8)). All species were characterized by multielement NMR spectroscopy and electrospray mass spectrometry. In addition clusters 3, 5, and 6–8 were characterized by single-crystal X-ray diffraction in [K(18-crown-6)]2[3], [K(2,2,2-crypt)][5], [K(2,2,2-crypt)][6]·THF, [K(2,2,2-crypt)][7]·hex, and [K(2,2,2-crypt)][8]·0.65THF·0.35hex, respectively. Density functional theory level calculations were conducted on all anionic species to probe their electronic structure.

Chiral cyclopalladated complex promoted asymmetric synthesis of diester-substituted P,N-ligands via stepwise hydrophosphination and hydroamination reactions

A series of enantiomerically pure 1,2-diester substituted P,N-ligands incorporating two chiral carbons in the backbone were generated in high yields and high stereoselectivity from acetylenedicarboxylate via initial hydrophosphination using diphenylphosphine followed by hydroamination with various primary and secondary amines. The reactions were activated and stereochemically controlled by the organopalladium complex containing ortho-palladated (S)-(1-(dimethylamino)ethyl)naphthalene under mild conditions. The absolute stereochemistry and the coordination chemistry of P,N-products were determined by the single crystal X-ray diffraction analysis. All the chiral P,N-ligands could be liberated from the palladium template without loss of optical purity. Subsequent recomplexation to selected chiral palladium centers confirmed the optical purity of the new functionalized chiral P,N-ligands.

Stepwise activation of “non-innocent” Cp* substituents – a Cp* based cascade reaction

Reactions of Cp* substituted pentelidene complexes with the primary phosphine Cp*PH(2) yield novel polycyclic phosphorus/arsenic and carbon containing cage compounds via cascade-like reactions. These reactions include a sequence of nucleophilic addition reactions, intramolecular hydrophosphination (partially hydroarsination) reactions, retro-Diels-Alder reactions with Cp*H elimination and subsequent [2+4]-cycloadditions.

Palladacycle mediated synthesis of cyano-functionalized chiral 1,2-diphosphine and subsequent functional group transformations

Cyano-functionalized allylic phosphine substrates containing the ortho-metalated ( R)-(1-(dimethylamino)ethyl)naphthalene as the chiral auxiliary were synthesized from bromoacetaldehyde dimethylacetal via a one-pot process. The diastereoselective hydrophosphination reactions of the cis- and trans-allylic phosphine substrates gave the cyano-functionalized chiral 1,2-bis(diphenylphosphino)ethane products with high yield and stereoselectivity. The subsequent organic transformation reactions of the cyano-substituted products chemoselectively afforded the formyl- and hydroxyl-functionalized chiral 1,2-diphosphine complexes with retention of stereochemistry. The coordination properties and absolute configurations of the novel 1,2-diphosphine complexes were established by single crystal X-ray crystallography. The optically pure 1,2-bis(diphenylphosphino)ethane ligands with cyano-, formyl- and hydroxyl-functionalities could be liberated in high yields from the corresponding dihalo palladium complexes by treatment with aqueous potassium cyanide.

Novel Synthesis of Chiral 1,3-Diphosphines via Palladium Template Promoted Hydrophosphination and Functional Group Transformation Reactions

A novel cyano-functionalized monophosphine palladium substrate containing the ortho-metalated (R)-(1-(dimethylamino)ethyl)naphthalene as the chiral auxiliary was synthesized from 3-chloropropionaldehyde diethylacetal via a one-pot process. The asymmetric hydrophosphination reactions between diphenylphosphine and the trans- or cis-monophosphine substrates were carried out under mild conditions, which gave the corresponding cyano-substituted chiral 1,3-bis(diphenylphosphino)propane palladium complexes with good yields and stereoselectivities. Subsequent functional group transformation reactions were conducted by successive treatment of the hydrophosphination products with Dibal-H and chemoselectively yielded the formyl- and hydroxyl-functionalized chiral 1,3-diphosphine complexes. The absolute configurations and coordination information of the novel 1,3-diphosphine complexes were analyzed by X-ray crystallography. The optically pure 1,3-bis(diphenylphosphino)propane ligands with cyano, formyl, and hydroxyl ...

Asymmetric Synthesis of New Diphosphines and Pyridylphosphines via a Kinetic Resolution Process Promoted and Controlled by a Chiral Palladacycle

A chiral palladacycle has been used successfully to promote the asymmetric hydrophosphination reactions between the racemic secondary phosphine ethylphenylphosphine and (E)/(Z)-diphenyl-1-propenylp...

NBuLi‐Mediated Hydrophosphination: A Simple Route to Valuable Organophosphorus Compounds

AbstractA straightforward synthesis of homoallyl‐ and allylphosphanes has been developed using nBuLi‐mediated hydrophosphination of conjugated dienes. In all the cases the phosphorus atom of the reacting phosphane attacked thesterically less demanding side of the diene exclusively. In addition, high regioselectivities towards 1,2‐ or 1,4‐addition products were observed depending on the nature of the dienes. This hydrophosphination reaction was extended to a variety of substrates such as styrene derivatives, alkynes and 1,3,5‐cycloheptatriene. The structures of three hydrophosphination products were confirmed by X‐ray diffractionstudies.