A flexible nanofiber membrane containing dendritic oxygen probe for visual monitoring pressure distribution

Pressure-sensitive paints (PSP) enable non-intrusive visualization of surface pressure distribution on model surface which is important for aerodynamic studies. However, conventional PSP materials suffer from photobleaching and inadequate sensitivity. In this work, we rationally designed and synthesized novel dendritic oxygen probes (PT1 and PT2) by covalently grafting fluorinated dendrons onto platinum tetrakis(pentafluorophenyl)porphyrin (PT0) (a common oxygen probe). Subsequently, PT2 loaded nanofibers membranes from polycaprolactone (PCL) were fabricated by electrospinning. Fabricated membranes showed high oxygen sensitivity (I0/I100 = 35.3) with excellent flexibility, good reversibility, and outstanding photostability (merely 2.0% intensity loss after prolonged irradiation). The pressure sensitivity was found around 0.73 % per kilopascal. Furthermore, significant variation in emission intensity with respect to the variation in air pressure (1.3-101.32 kPa), facilitates the naked eye visualization of the pressure distribution on the membrane surface. Such excellent oxygen and pressure sensitivity and photostability might be due to high fluorine contents of complex dendritic structure of PT2. This flexible fluorine-functionalized dendritic oxygen probe puts forward a facile and effective strategy to develop advanced PSP materials enabling accurate pressure mapping for aerodynamic studies.

Efficient synthesis of α-amino-vinylphosphine oxides from alkyl nitriles via manganese-catalyzed phosphinoenamination

A protocol for the synthesis of α-amino-vinylphosphine oxides by phosphinoenamination reaction between alkyl nitriles and phosphine oxides was developed. The combination of Mn(OAc)2 as a Lewis acid and guanidine as a Lewis base was found to be an efficient catalytic system for this reaction. A series of alkyl nitriles and phosphine oxides are compatible with this conversion, furnishing the desired products in up to 95% yield under mild conditions. Furthermore, this method demonstrates the capability of gram-scale synthesis.

Ligand-Free Iron-Catalyzed Construction of C-P Bonds via Phosphorylation of Alcohols: Synthesis of Phosphine Oxides and Phosphine Compounds

An efficient method for the construction of C-P(V) and C-P(III) bonds via the iron-catalyzed phosphorylation of alcohols under ligand-free conditions is disclosed. This strategy represents a straightforward process to prepare a series of phosphine oxides and phosphine compounds in good to excellent yields from the readily available alcohols and P-H compounds. A plausible mechanism is also proposed. We anticipate that this mode of transforming simple alcohols would apply in chemical synthesis widely.

Kinetic Resolution of P-Chiral Phosphindole Oxides through Rhodium-Catalyzed Asymmetric Arylation

Highly efficient kinetic resolution of P-chiral phosphindole oxides via rhodium-catalyzed asymmetric arylation under mild conditions is described. Selectivity factors of up to 569 were achieved by employing chiral diene* as a ligand. The transformation of the enantiopure benzophosphole derivative into a useful P-chiral bisphosphine ligand is also demonstrated.

Palladium-catalyzed regio- and stereo-selective phosphination of cyclic biarylsulfonium salts to access atropoisomeric phosphines

A palladium-catalyzed regio- and stereo-selective phosphination of cyclic biarylsulfonium salts (racemic) with HPAr3Ar4 for straightforward synthesis of atropoisomeric phosphines (P,S-ligands) bearing a stereogenic axis or both a stereogenic axis and a P-stereogenic center is reported. The high reactivity and regio- and stereo-selectivity originate from the torsional strain release and palladium catalysis, and the construction of a P-stereogenic center is enabled by an efficient dynamic kinetic resolution. The high performance of the nascent P,S-ligands has been demonstrated in palladium-catalyzed asymmetric allylic substitutions, indicating the great potential of the present methodology.

Enantioselective Synthesis of Phosphine Boranes via Crystallization-Induced Dynamic Resolution of Lithiated Intermediate by Understanding the Underlying Epimerization Process

Described herein is the successful crystallization-induced dynamic resolution (CIDR) of an α-lithiated phosphine borane utilizing the easily accessible and inexpensive ligand (R,R)-TMCDA. Starting from the essential P-prochiral building block dimethyl phenyl phosphine borane we were able to obtain phosphine boranes in yields up to 80 % and e.r. up to 98 : 2 by crystallization of the lithiated intermediate prior to the trapping reaction. NMR-based deuterium labeling experiments indicate that the epimerization in solution is based on the intermolecular proton transfer between nonlithiated phosphine borane and the corresponding lithiated intermediate, rendering the presence of the remaining starting compound in an optimized solvent mixture the main factor for successful enantioselective synthesis. Quantum chemical calculations using different model systems based on solid state structures confirm these experimental results. By gaining insights into the epimerization mechanism, essential principles for CIDR of lithiated phosphine boranes are elucidated that may be expanded to other important P-stereogenic compounds and simple chiral amines.

Second Generation Catalytic Enantioselective Nucleophilic Desymmetrization at Phosphorus (V): Improved Generality, Efficiency and Modularity

A broadly improved second generation catalytic two-phase strategy for the enantioselective synthesis of stereogenic at phosphorus (V) compounds is described. This protocol, consisting of a bifunctional iminophosphorane (BIMP) catalyzed nucleophilic desymmetrization of prochiral, bench stable P(V) precursors and subsequent enantiospecific substitution allows for divergent access to a wide range of C-, N-, O- and S- substituted P(V) containing compounds from a handful of enantioenriched intermediates. A new ureidopeptide BIMP catalyst/thiaziolidinone leaving group combination allowed for a far wider substrate scope and increased reaction efficiency and practicality over previously established protocols. The resulting enantioenriched intermediates could then be transformed into an even greater range of distinct classes of P(V) compounds by displacement of the remaining leaving group as well as allowing for even further diversification downstream. Density functional theory (DFT) calculations were performed to pinpoint the origin of enantioselectivity for the BIMP-catalyzed desymmetrization, to rationalize how a superior catalyst/leaving group combination leads to increased generality in our second-generation catalytic system, as well as shed light onto observed stereochemical retention and inversion pathways when performing late-stage enantiospecific SN2@P reactions with Grignard reagents.

Asymmetric synthesis of P-stereogenic phosphindane oxides via kinetic resolution and their biological activity

The importance of P-stereogenic heterocycles has been widely recognized with their extensive use as privileged chiral ligands and bioactive compounds. The catalytic asymmetric synthesis of P-stereogenic phosphindane derivatives, however, remains a challenging task. Herein, we report a catalytic kinetic resolution of phosphindole oxides via rhodium-catalyzed diastereo- and enantioselective conjugate addition to access enantiopure P-stereogenic phosphindane and phosphindole derivatives. This kinetic resolution method features high efficiency (s factor up to >1057), excellent stereoselectivities (all >20:1 dr, up to >99% ee), and a broad substrate scope. The obtained chiral phosphindane oxides exhibit promising therapeutic efficacy in autosomal dominant polycystic kidney disease (ADPKD), and compound 3az is found to significantly inhibit renal cyst growth both in vitro and in vivo, thus ushering in a promising scaffold for ADPKD drug discovery. This study will not only advance efforts towards the asymmetric synthesis of challenging P-stereogenic heterocycles, but also surely inspire further development of P-stereogenic entities for bioactive small-molecule discovery.

Regioselective One-Pot Synthesis of Vicinal Bisphosphine Derivatives from Nitroalkenes by Hydrophosphinylation/Elimination/Hydrophosphinylation

Herein, a facile method is developed for the synthesis of vicinal bisphosphine derivatives based on a cascade of hydrophosphinylation, elimination, and hydrophosphinylation of secondary phosphine oxides with nitroalkenes. This cascade reaction provides step-economy access to a series of vicinal bisphosphine derivatives with high to excellent yields (up to 99%). This method was further extended to prepare, in one-pot, regioselective vicinal bisphosphine derivatives that incorporated two different phosphorus functional groups.

Enantioselective Hydrophosphination of Terminal Alkenyl Aza-Heteroarenes

This paper presents a Mn(I)-catalysed methodology for the enantioselective hydrophosphination of terminal alkenyl aza-heteroarenes. The catalyst operates through H-P bond activation, enabling successful hydrophosphination of a diverse range of alkenyl-heteroarenes with high enantioselectivity. The presented protocol addresses the inherently low reactivity and the commonly encountered suboptimal enantioselectivities of these challenging substrates. As an important application we show that this method facilitates the synthesis of a non-symmetric tridentate P,N,P-containing ligand like structure in just two synthetic steps using a single catalytic system.

Atroposelective hydroarylation of biaryl phosphines directed by phosphorus centres

Prized for their ability to generate chemical complexity rapidly, catalytic carbon-hydrogen (C-H) activation and functionalization reactions have enabled a paradigm shift in the standard logic of synthetic chemistry. Directing group strategies have been used extensively in C-H activation reactions to control regio- and enantioselectivity with transition metal catalysts. However, current methods rely heavily on coordination with nitrogen and/or oxygen atoms in molecules and have therefore been found to exhibit limited generality in asymmetric syntheses. Here, we report enantioselective C-H activation with unsaturated hydrocarbons directed by phosphorus centres to rapidly construct libraries of axially chiral phosphines through dynamic kinetic resolution. High reactivity and enantioselectivity are derived from modular assembly of an iridium catalyst with an endogenous phosphorus atom and an exogenous chiral phosphorus ligand, as confirmed by detailed experimental and computational studies. This reaction mode significantly expands the pool of enantiomerically enriched functional phosphines, some of which have shown excellent efficiency for asymmetric catalysis.

A Powerful P-N Connection: Preparative Approaches, Reactivity, and Applications of P-Stereogenic Aminophosphines

For more than five decades, P-stereogenic aminophosphine chalcogenides and boranes have attracted scientific attention and are still in the focus of ongoing research. In the last years, novel transition metal-based synthesis methods have been discovered, in addition to the long-known use of chiral auxiliaries. Enantiomerically pure compounds with N-P+ -X- (X=O, S, BH3 ) motifs served as valuable reactive building blocks to provide new classes of organophosphorus derivatives, thereby preserving the stereochemical information at the phosphorus atom. Over the years, intriguing applications in organocatalysis and transition metal catalysis have been reported for some representatives. Asymmetric reductions of C=C, C=N, and C=O double bonds were feasible with selected P-stereogenic aminophosphine oxides in the presence of hydrogen transfer reagents. P-stereogenic aminophosphine boranes could be easily deprotected and used as ligands for various transition metals to enable catalytic asymmetric hydrogenations of olefins and imines. This review traces the emergence of a synthetically and catalytically powerful functional compound class with phosphorus-centered chirality in its main lines, starting from classical approaches to modern synthesis methods to current applications.

P(III)-Chirogenic Phosphinite Building Blocks by Stereospecific N→O Phosphinyl Migration

In the recent past, the chirality borne by a phosphorus center has aroused growing interest in many fields, and the development of new methodologies, notably using inexpensive reagents and simple experimental conditions, has become topical. An efficient stereoselective synthesis of P-chirogenic phosphinites useful as chiral phosphorus building blocks is herein described thanks to a new intramolecular phosphorus rearrangement based on P*(III)-phosphinyl N→O migration. This rearrangement was performed by heating at 50 °C aminophosphine-boranes, easily prepared from chiral amino alcohols, with DABCO in toluene overnight. Twenty-seven P-chirogenic phosphinites and borane complexes were thus prepared in yields up to 89%. The crude P*(III)-phosphinites were in situ used in stereoselective synthesis of P-chirogenic aminophosphine-phosphinites, phosphinothioates, sec- and tert-phosphine-oxides, and mono- and diphosphines in overall yields ranging from 28 to 89% and with e.e. up to 99%. Twenty-one X-ray structures of P-chirogenic compounds were established, allowing us to attribute undoubtedly their absolute configuration and the stereochemistry of the reactions. Finally, new ferrocenyl-bridged diphosphine ligands synthesized from P*(III)-chirogenic diphosphinites were tested in asymmetric metal-catalyzed reactions, providing enantioselectivities up to 95% e.e. in allylation of α-naphthylmethylamine at room temperature. To conclude, this rearrangement opens up an efficient new way for the stereoselective synthesis of numerous classes of P-chirogenic phosphorus compounds, notably bearing bulky substituents.

Borrowing Hydrogen β-Phosphinomethylation of Alcohols Using Methanol as C1 Source by Pincer Manganese Complex

Herein, we report a manganese-catalyzed three-component coupling of β-H containing alcohols, methanol, and phosphines for the synthesis of γ-hydroxy phosphines via a borrowing hydrogen strategy. In this development, methanol serves as a sustainable C1 source. A variety of aromatic and aliphatic substituted alcohols and phosphines could undergo the dehydrogenative cross-coupling process efficiently and deliver the corresponding β-phosphinomethylated alcohol products in moderate to good yields. Mechanistic studies suggest that this transformation proceeds in a sequential manner including catalytic dehydrogenation, aldol condensation, Michael addition, and catalytic hydrogenation.

Ruthenium(II) Complexes of a Xanthene-Spanned Dicarbene Ligand

Octahedral ruthenium(II) complexes of a xanthene-di(N-heterocyclic carbene) ancillary ligand (XdC) have been prepared and structurally characterized. Examples catalyze the transfer hydrogenation of ketones {[Ru(CO)I2(C,O,C'-XdC)] (1) and [Ru(CO)(MeCN)2(C,O,C'-XdC)]2+ (22+)} and the selective electrochemical reduction of CO2 to CO {[Ru(N,N'-bpy)(CO)(C,O,C'-XdC)]2+ (32+) at 0.40 V overpotential in MeCN-H2O (1 M)}. The reaction of 1 with KBEt3H afforded isomers of [(C,C'-XdC)Ru(μ-H)(H)]2 dimers, which are stable to reductive elimination of the XdC ligand, thereby suggesting similar (XdC)Rh(coligand)(H)x species may be viable intermediates in catalyses. The electrochemical reduction of CO2 involves a double reduction of 32+ to 3••, which has been characterized by IR-SEC and DFT calculations. The DFT calculations suggest the Ru-Oxanth bond breaks in 3••, opening a metal site for CO2 binding with selectivity over protons enabled by the diffuse nature of the HOMO delocalized over the metal and the bipyridine and carbonyl coligands. The results point to the promise of metal complexes of flexible and hemilabile xanthene-(NHC)2 ancillary ligands in catalysis.

Design and Application of Peptide-Mimic Phosphonium Salt Catalysts in Asymmetric Synthesis

Chiral phosphonium salt catalysis, traditionally classified as a type of phase transfer catalysis, has proven to be a powerful strategy for the stereoselective preparation of diverse optically active molecules. However, there still remain numerous forbidding issues of reactivity and selectivity in such well-known organocatalysis system. Accordingly, the development of new and high-performance phosphonium salt catalysts with unique chiral backbones is highly desirable, yet challenging. This Minireview describes the prominent endeavours in the development of a new family of chiral peptide-mimic phosphonium salt catalysts with multiple hydrogen-bonding donors and their applications in a plethora of enantioselective synthesis during the past few years. Hopefully, this minireview will pave a way for further developing much more efficient and privileged chiral ligands/catalysts featuring exclusively catalytic ability in asymmetric synthesis.

Nickel-Catalyzed Asymmetric Synthesis of P-Stereogenic Phosphanyl Hydrazine Building Blocks

Catalytic asymmetric methods for the synthesis of synthetically versatile P-stereogenic building blocks offer an efficient and practical approach for the diversity-oriented preparation of P-chiral phosphorus compounds. Herein, we report the first nickel-catalyzed synthesis of P-stereogenic secondary aminophosphine-boranes by the asymmetric addition of primary phosphines to azo compounds. We further demonstrate that the P-H and P-N bonds on these phosphanyl hydrazine building blocks can be reacted sequentially and stereospecifically to access various P-stereogenic compounds with structural diversity.

Sustainable Photo- and Electrochemical Transformation of White Phosphorous (P4 ) into P1 Organo-Compounds

Elemental white phosphorous (P4 ) is a crucial feedstock for the entire phosphorus-derived chemical industry, serving as a common precursor for the ultimate preparation of high-grade monophosphorus (P1 ) fine chemicals. However, the corresponding manufacturing processes generally suffer from a deep reliance on hazardous reagents, inputs of immense energy, emissions of toxic pollutants, and the generation of substantial waste, which have negative impacts on the environment. In this context, sustainability and safety concerns provide a consistent impetus for the urgent overall improvement of phosphorus cycles. In this Concept, we present an overview of the most recent growth in photo- and electrochemical synthesis of P1 organo-compounds from P4 , with special emphasis on sustainable features. The key aspects of innovations regarding activation mode and mechanism have been comprehensively analyzed. A preliminary look at the possible future direction of development is also provided.

Carbon-Phosphorus Ligands with Extreme Donating Character

Carbeniophosphines [R2 C+ -PR2 ] and phosphonium ylides [R3 P+ -CR2 - ] are two complementary classes of carbon-phosphorus based ligands defined by their unique donor properties. Indeed, while carbeniophosphines are electron-poor P-ligands due to the positioning of a positive charge near the coordinating P-atom, phosphonium ylides are electron-rich C-ligands due to the presence of a negatively charged coordinating C-atom. Based on this knowledge, this account summarizes our recent contribution on these two classes of carbon-phosphorus ligands, and in particular the strategies developed to lower the donor character of carbeniophosphines and enhance that of phosphonium ylides. This led us to design, at both extremities of the donating scale, extremely electron-poor P-ligands exemplified by imidazoliophosphonites [R2 C+ -P(OR)2 ] and dicarbeniophosphines [(R2 C+ )2 -PR], and extremely electron-rich C-ligands illustrated by pincer architectures exhibiting several phosphonium ylide donor extremities. In the context of carbon-phosphorus analogy, the closely related cases of ligands where the C-atom of a NHC ligand is in close proximity of two positive charges, and that of a phosphonium ylide coordinated through its P-atom are also discussed. An overview of the synthetic methods, coordinating properties, general reactivity and electronic structure of all these C,P-based species is presented here.

Copper(I)-Catalyzed Asymmetric Hydrophosphination of 3,3-Disubstituted Cyclopropenes

Herein, a copper(I)-catalyzed asymmetric hydrophosphination of 3,3-disubstituted cyclopropenes is reported. It provides a series of phosphine derivatives in high to excellent diastereo- and enantioselectivities. The methodology enjoys broad substrate scope on both 3,3-disubstituted cyclopropenes and diarylphosphines. The high stereoselectivity is attributed to both the high stability of the Cu(I)-(R,R)-QUINOXP* complex in the presence of stoichiometric HPPh2 and the produced phosphines, and the high-performance asymmetric induction of the Cu(I)-(R,R)-QUINOXP* complex. Finally, the method is used for the synthesis of new chiral phosphine-olefin compounds built on a cyclopropane skeleton, one of which serves as a wonderful ligand in Rh-catalyzed asymmetric conjugate addition of phenylboronic acid to various α,β-unsaturated compounds.

Asymmetric construction of phosphono dihydropyranones from α-ketophosphonates enabled by Pd/chiral isothiourea relay catalysis

A highly enantio- and diastereoselective approach has been developed for the synthesis of chiral phosphono dihydropyranones. This approach is enabled by Pd/chiral isothiourea relay catalysis under mild reaction conditions, starting from readily available benzyl bromides, CO, and α-ketophosphonates. The cascade reaction involves the generation of a ketene intermediate from Pd-catalyzed carbonylation of benzyl bromide and subsequent chiral Lewis base catalyzed formal [4 + 2] reaction. Phosphono lactone products can also be transformed to chiral 1,5-diester products in good yield and high stereoselectivity.

Linear bis-Coordinate Silver(I) and Iodine(I) Complexes with R3 R2 R1 N Tertiary Amines

Homoleptic [L-I-L]+ iodine(I) complexes (where L is a R3 R2 R1 N tertiary amine) were synthesized via the [L-Ag-L]+ → [L-I-L]+ cation exchange reaction. In solution, the amines form [R3 R2 R1 N-Ag-NR1 R2 R3 ]+ silver(I) complexes, which crystallize out from solution as the meso-[L-Ag-L]+ complexes, as characterized by X-ray crystallography. The subsequent [L-I-L]+ iodine(I) analogues were extremely reactive and could not be isolated in the solid state. Density functional theory (DFT) calculations were performed to study the Ag+ -N and I+ -N interaction energies in silver(I) and iodine(I) complexes, with the former ranging from -80 to -100 kJ mol-1 and latter from -260 to -279 kJ mol-1 . The X-ray crystal structures revealed Ag+ ⋅⋅⋅Cπ and Ag+ ⋅⋅⋅H-C short contacts between the silver(I) cation and flexible N-alkyl/N-aryl groups, which are the first of their kind in such precursor complexes.

Access to Enantiomerically Pure P-Chiral 1-Phosphanorbornane Silyl Ethers

Sulfur-protected enantiopure P-chiral 1-phosphanorbornane silyl ethers 5a,b are obtained in high yields via the reaction of the hydroxy group of P-chiral 1-phosphanorbornane alcohol 4 with tert-butyldimethylsilyl chloride (TBDMSCl) and triphenylsilyl chloride (TPSCl). The corresponding optically pure silyl ethers 5a,b are purified via crystallization and fully structurally characterized. Desulfurization with excess Raney nickel gives access to bulky monodentate enantiopure phosphorus(III) 1-phosphanorbornane silyl ethers 6a,b which are subsequently applied as ligands in iridium-catalyzed asymmetric hydrogenation of a prochiral ketone and enamide. Better activity and selectivity were observed in the latter case.

Synthesis of P-Stereogenic Phosphinamides via Pd(II)-Catalyzed Enantioselective C-H Alkynylation

P-Stereogenic phosphinamides represent important structural elements in chiral organocatalysts and bioactive compounds. Herein, we report Pd(II)-catalyzed enantioselective C-H alkynylation using cheap commercially available l-pyroglutamic acid as a chiral ligand. A range of structurally diverse P-stereogenic phosphinamides was prepared in good yields with high enantioselectivities via desymmetrization and kinetic resolution. A tailor-made congested directing group, N-ethyl-N-(3-methylpyridin-2-yl)amino, was crucial for the reactivity.

Cobaltaelectro-Catalyzed C-H Annulation with Allenes for Atropochiral and P-Stereogenic Compounds: Late-Stage Diversification and Continuous Flow Scale-Up

The 3d metallaelectro-catalyzed C-H activation has been identified as an increasingly viable strategy to access valuable organic molecules in a resource-economic fashion under exceedingly mild reaction conditions. However, the development of enantioselective 3d metallaelectro-catalyzed C-H activation is very challenging and in its infancy. Here, we disclose the merger of cobaltaelectro-catalyzed C-H activation with asymmetric catalysis for the highly enantioselective annulation of allenes. A broad range of C-N axially chiral and P-stereogenic compounds were thereby obtained in good yields of up to 98% with high enantioselectivities of up to >99% ee. The practicality of this approach was demonstrated by the diversification of complex bioactive compounds and drug molecules as well as decagram scale enantioselective electrocatalysis in continuous flow.

Universal and divergent P-stereogenic building with camphor-derived 2,3-diols

The access to P-stereogenic motifs has always been considered a very challenging and high attractive mission in modern organic synthesis. While several chiral auxiliaries employed by the practical Jugé-Stephan-like methodology have been developed, new type of readily accessible bifunctional ligands toward P-stereogenic building still remain much desirable. Herein, we present a powerful chiral template, camphor-derived 2,3-diols named CAMDOL, which were designed and synthesized from the commercially cheap camphorquinone in high yields at 50 grams scale with a column-free purification. Diverse P(III)-chiral compounds and their borane forms including phosphinous acids, phosphinites, and phosphines, as well as the corresponding P(V)-chiral compounds including phosphinates, phosphine oxides, phosphinothioates, phosphine sulfides, and secondary phosphine oxides were afforded in high yields and ee values through the optimal 2,3-diphenyl CAMDOL platform. An unusual C³-OP bond cleavage following the first P-OC² bond breaking was observed during the ring-opening process when quenching by NH₄Cl solution, which generates a unique but valuable camphor-epoxide scaffold as by-product.

New Optically Active tert-Butylarylthiophosphinic Acids and Their Selenium Analogues as the Potential Synthons of Supramolecular Organometallic Complexes: Syntheses and Crystallographic Structure Determination

The aim of the research described in this publication is two-fold. The first is a detailed description of the synthesis of a series of compounds containing a stereogenic heteroatom, namely the optically active P-stereogenic derivatives of tert-butylarylphoshinic acids bearing sulfur or selenium. The second is a detailed discussion dedicated to the determination of their structures by an X-ray analysis. Such a determination is needed when considering optically active hetero-oxophosphoric acids as new chiral solvating agents, precursors of new chiral ionic liquids, or ligands in complexes serving as novel organometallic catalysts.

Catalytic enantioselective nucleophilic desymmetrization of phosphonate esters

Molecules that contain a stereogenic phosphorus atom are crucial to medicine, agrochemistry and catalysis. While methods are available for the selective construction of various chiral organophosphorus compounds, catalytic enantioselective approaches for their synthesis are far less common. Given the vastness of possible substituent combinations around a phosphorus atom, protocols for their preparation should also be divergent, providing facile access not only to one but to many classes of phosphorus compounds. Here we introduce a catalytic and enantioselective strategy for the preparation of an enantioenriched phosphorus(V) centre that can be diversified enantiospecifically to a wide range of biologically relevant phosphorus(V) compounds. The process, which involves an enantioselective nucleophilic substitution catalysed by a superbasic bifunctional iminophosphorane catalyst, can accommodate a wide range of carbon substituents at phosphorus. The resulting stable, yet versatile, synthetic intermediates can be combined with a multitude of medicinally relevant O-, N- and S-based nucleophiles.

Three- and Five-Membered Anionic Chains of Pnictogenylboranes

An unprecedented family of three- and five-membered substituted anionic derivatives of parent pnictogenylboranes is herein reported. Reacting various combinations of the pnictogenylboranes H₂ E'-BH₂ -NMe₃ (E'=P, As) with pnictogen-based nucleophiles MER1R2 (E=P, As; R1=H, R2=^t Bu; R1=R2=Ph; M=Na, K) allows for the isolation of the unsymmetrical products [Na(18-crown-6)][H₂ E'-BH₂ -EH^t Bu] (3: E=E'=P; 4: E=E'=As; 5: E=As, E'=P) and [M(C)][H₂ E'-BH₂ -EPh₂ ] (7: E=E'=P, M=Na, C=18-crown-6; 8: E=E'=As; M=K, C=[2.2.2]cryptand; 9: E=P, E'=As, M=Na, C=[2.2.2]cryptand; 10: E=As, E'=P, M=K, C=[2.2.2]cryptand). [Na(18-crown-6)][H₂ As-BH₂ -^t BuPH-BH₃ ] (6) is only accessible by a different pathway, using ^t BuPH₂ , BH₃  ⋅ SMe₂ and NaNH₂ as starting materials. Additionally, the synthesis of symmetrical diphenyl-substituted compounds [M(18-crown-6)][Ph₂ E-BH₂ -EPh₂ ] (11: E=P, M=Na; 12: E=As, M=K) is reported which can be regarded as isostructural inorganic, negatively charged analogs of dppm (1,1-bis(diphenylphosphino)methane) and dpam (1,1-bis(diphenylarsino)methane). Furthermore, an elongation of the pnictogen boron backbone in compounds 3, 7 and 9' (similar compound to 9, stabilized however by 18-crown-6), is attainable by reacting them with the pnictogenylboranes H₂ E'-BH₂ -NMe₃ leading to corresponding five-membered chain-like compounds [Na(18-crown-6)][H₂ E-BH₂ -R1R2P-BH₂ -E'H₂ ] (E=E'=P, R1=H, R2=^t Bu (13); E=E'=P, R1=R2=Ph (14); E=E'=As, R1=R2=Ph (15); E=P, E'=As, R1=R2=Ph (16)). Finally, the thermodynamics of the reaction pathways were evaluated by quantum chemical computations.

Cooperative Nitrile Coordination Using Nickel and a Boron-Containing Secondary Coordination Sphere

Metal-ligand cooperation has emerged as a versatile tool for substrate activation in chemical reactivity. Herein, we provide the synthesis and characterization of a monoboranyl-containing analogue of the ubiquitous bulky diphosphine ligand, 1,2-bis(di-tert-butylphosphino)ethane, whose reactivity has been examined using nickel. Together, the pairing of nickel and boron provides a platform that allows for the cooperative coordination of organonitriles, giving unusual examples of intermolecularly bound dinickelacycles.

Manganese(I)-Catalyzed Asymmetric Hydrophosphination of α,β-Unsaturated Carbonyl Derivatives

Here we report catalytic asymmetric hydrophosphination of α,β-unsaturated carbonyl derivatives using a chiral Mn(I) complex as a catalyst. Through H-P bond activation, various phosphine-containing chiral products can be accessed via hydrophosphination of various ketone-, ester-, and carboxamide-based Michael acceptors.

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.

Rhodium and ruthenium complexes of methylene-bridged, P-stereogenic, unsymmetrical diphosphanes

Enantiopure P-stereogenic methylphosphane-boranes (S_P)-P(BH₃)PhArMe (ArMe; Ar = 1-naphthyl (NpMe), and 2-biphenylyl (BiphMe)) have been used to prepare diphosphanes of the type ArPhPCH₂PR₂ (R = Ph, iPr or tBu; ArR). The ligands have been reacted with [Rh(COD)₂]BF₄ to furnish the corresponding six monochelated [Rh(COD)(ArR)]BF₄ organometallic compounds (RhArR) or, depending on the reaction conditions, the bis(chelated) coordination compound [Rh(BiphiPr)₂]BF₄ as a mixture of cis and trans isomers. The crystal structure of cis-[Rh(BiphiPr)₂]BF₄ was obtained. The coordination of the BiphR with [RuCl(μ-Cl)(η⁶-p-cymene)₂]₂ under different conditions produced cationic chelated complexes of the type [RuCl(η⁶-p-cymene)(κ²-BiphR)]PF₆ (RuBiphR) and the neutral monocoordinated complex [RuCl₂(η⁶-p-cymene)(κ¹-BiphPh)] (RuBiphPh') with the uncoordinated P-stereogenic moiety. The Rh(I) complexes were used in the catalytic hydrogenation of functionalized olefins and the Ru(II) complexes were tested in the transfer hydrogenation of acetophenone. Both precursors displayed good activities with moderate enantioselectivities.

Copper-Catalyzed Dynamic Kinetic Resolution of Secondary Phosphine Oxides

Copper-catalyzed dynamic kinetic resolution of secondary phosphine oxides has been successfully developed, providing a general method for the gram-scale enantioselective synthesis of P-stereogenic cyclic phosphine oxides with high yields and high enantioselectivities. The products could be easily reduced to the corresponding useful P(III)-stereogenic cyclic phosphines. A mechanism of the dynamic kinetic resolution involving the unusual rapid racemization of SPOs has been proposed.

Enantioseparation of P-Stereogenic 1-Adamantyl Arylthiophosphonates and Their Stereospecific Transformation to 1-Adamantyl Aryl-H-phosphinates

A focused library of 1-adamantyl arylthiophosphonates was prepared in racemic form. An enantioseparation method was developed for P-stereogenic thiophosphonates using (S)-1-phenylethylamine as the resolving agent. Under optimized conditions, three out of the five arylthiophosphonates were prepared in enantiopure form (ee > 99%). The subsequent desulfurization of optically active arylthiophosphonates gave the corresponding H-phosphinates without significant erosion of enantiomeric purity (ee = 95-98%). Hence, this reaction sequence can be considered an alternative method for the preparation of 1-adamantyl aryl-H-phopshinates. The absolute configuration of the (S)-1-adamantyl phenylphosphonothioic acid was assigned using single-crystal XRD and it allowed the confirmation that the removal of the P = S group proceeds with retention of configuration. The organocatalytic applicability of (S)-1-adamantyl phenylphosphonothioic acid was also evaluated as a P-stereogenic Brønsted acid.

Investigation of the Asymmetric Addition Reactions Induced by Pentacoordinated Hydrospirophosphorane Substrate

Pentacoordinated bisaminoacyl hydrospirophosphoranes were first found to induce the asymmetric addition reactions as a novel chiral organic framework. Asymmetric addition reactions of bisaminoacyl hydrospirophosphoranes with aromatic aldehyde and in situ generated imine were investigated, and the corresponding α-hydroxyspirophosphonates and α-amino spirophosphonates were obtained. The addition reaction of hydrospirophosphoranes with Δ_P configuration showed better stereoselectivity than that with Λ_P configuration, not only for the addition reaction to aromatic aldehyde but also to in situ generated imine. Furthermore, the stereochemical mechanisms of asymmetric addition reactions induced by pentacoordinated hydrospirophosphorane were proposed by ³¹P NMR tracing experiment and X-ray diffraction analysis.

A Ni-catalyzed asymmetric C(sp)-P cross-coupling reaction for the synthesis of P-stereogenic alkynylphosphines

Due to the high reactivity of the triple bond, P-stereogenic alkynylphosphines could be easily derivatized, serving as universal building blocks for structurally diverse phosphine compounds. However, the synthesis of alkynylphosphines via direct P-C bond formation was unprecedented. Here, we report an efficient method for the synthesis of P-stereogenic alkynylphosphines with high enantioselectivity via a Ni-catalyzed asymmetric cross-coupling reaction. The reaction could tolerate a variety of functional groups, affording products that can be converted into useful phosphine derivatives.

Asymmetric Hydrophosphinylation of Alkynes: Facile Access to Axially Chiral Styrene-Phosphines

A Cu/CPA co-catalytic system has been developed for achieving the direct hydrophosphinylation of alkynes with phosphine oxides in delivering novel axially chiral phosphorus-containing alkenes in high yields and excellent enantioselectivities (up to 99 % yield and 99 % ee). DFT calculations were performed to elucidate the reaction pathway and the origin of enantiocontrol. This streamlined and modular methodology establishes a new platform for the design and application of new axially chiral styrene-phosphine ligands.

Stereospecific nickel-catalyzed [4+2] heteroannulation of alkynes with aminophosphanes

Enantioenriched phosphorus compounds play crucial roles in many fields ranging from catalyst to materials science to drug development. Despite advances in the construction of phosphacycles, incorporation of a P-chirogenic center into heterocycles remains challenging. Here, we report an effective method for the preparation of phosphacycles through nickel-catalyzed [4+2] heteroannulation of internal alkynes with aminophosphanes derived from o-haloanilines. Notably, chiral 2-λ5-phosphaquinolines can be prepared from P-stereogenic substrates via NH/PH tautomeric equilibrium without loss of stereochemical integrity. The strategy is found to exhibit a broad scope in terms of both reaction components, enabling modular construction of libraries of 2-λ5-phosphaquinolines with different steric and electronic properties for fine-tuning photophysical properties, where some of these compounds showed distinct fluorescence with high quantum yields. A series of mechanistic studies further shed light on the pathway of the heteroannulation and reasons for stereospecificity.

Organocatalytic asymmetric synthesis of P-stereogenic molecules

P-chirality broadly appears in natural and synthetic functional molecules. The catalytic synthesis of organophosphorus compounds bearing P-stereogenic centers is still challenging, due to the lack of efficient catalytic systems. This review summarizes the key achievements in organocatalytic methodologies for the synthesis of P-stereogenic molecules. Different catalytic systems are emphasized for each strategy class (desymmetrization, kinetic resolution, and dynamic kinetic resolution) with examples cited to illustrate the potential applications of the accessed P-stereogenic organophosphorus compounds.

Prodrugs of Nucleoside 5'-Monophosphate Analogues: Overview of the Recent Literature Concerning their Synthesis and Applications

Nucleoside analogues are widely used as anti-infectious and antitumoral agents. However, their clinical use may face limitations associated with their physicochemical properties, pharmacokinetic parameters, and/or their peculiar mechanisms of action. Indeed, once inside the cells, nucleoside analogues require to be metabolized into their corresponding (poly-)phosphorylated derivatives, mediated by cellular and/or viral kinases, in order to interfere with nucleic acid biosynthesis. Within this activation process, the first-phosphorylation step is often the limiting one and to overcome this limitation, numerous prodrug approaches have been proposed. Herein, we will focus on recent literature data (from 2015 and onwards) related to new prodrug strategies, the development of original synthetic approaches and novel applications of nucleotide prodrugs (namely pronucleotides) leading to the intracellular delivery of 5'-monophosphate nucleoside analogues.

Access to Enantiomerically Pure P-Stereogenic Primary Aminophosphine Sulfides under Reductive Conditions

Stereochemically pure phosphines with phosphorus-heteroatom bonds and P-centered chirality are a promising class of functional building blocks for the design of chiral ligands and organocatalysts. A route to enantiomerically pure primary aminophosphine sulfides was opened through stereospecific reductive C-N bond cleavage of phosphorus(V) precursors by lithium in liquid ammonia. The chemoselectivity of the reaction as a function of reaction time, substrate pattern, and chiral auxiliary was investigated. In the presence of exclusively aliphatic groups bound to the phosphorus atom, all competing reductive side reactions are totally prevented. The absolute configurations of all P-stereogenic compounds were determined by single-crystal X-ray diffraction analysis. Their use as synthetic building blocks was demonstrated. The lithium salt of (R)-BINOL-dithiophosphoric acid proved to be a useful stereochemical probe to determine the enantiomeric purity. Insights into the coordination mode of the lithium-based chiral complex formed in solution was provided by NMR spectroscopy and DFT calculations.

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.

Alkylboronic acids as alkylating agents: photoredox-catalyzed alkylation reactions assisted by K3PO4

Despite the ubiquity of alkylboronic acids in organic synthesis, their utility as alkyl radical precursors in visible-light-induced photocatalytic reactions is limited by their high oxidation potentials. In this study, we demonstrated that an inorganophosphorus compound can modulate the oxidation potentials of alkylboronic acids so that they can act as alkyl radical precursors. We propose a mechanism based on the results of fluorescence quenching experiments, electrochemical experiments, ¹¹B and ³¹P NMR spectroscopy, and other techniques. In addition, we describe a simple and reliable alkylation method that has good functional group tolerance and can be used for direct C-B chlorination, cyanation, vinylation, alkynylation, and allylation, as well as late-stage functionalization of derivatized drug molecules. Notably, alkylboronic acids can be selectively activated in the presence of a boronic pinacol ester.

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.