The oxorhenium(VII)-catalyzed direct condensation of phosphoric acid with an alcohol

A highly efficient catalytic method for the synthesis of phosphite diesters

In contrast to conventional methods that rely on stoichiometric activation of phosphonylating reagents, we have developed a highly efficient catalytic method for the synthesis of phosphite diesters using a readily available phosphonylation reagent and alcohols with environmentally benign Zn(ii) catalysts. Two alcohols could be introduced consecutively on the P center with release of trifluoroethanol as the sole byproduct, without any additive, under mild conditions. The products could be oxidized smoothly to access phosphate triesters. A range of alcohols, including sterically demanding and highly functionalized alcohols such as carbohydrates and nucleosides, can be applied in this reaction.

Beyond Triphenylphosphine: Advances on the Utilization of Triphenylphosphine Oxide

Triphenylphosphine oxide is a well-known industrial waste byproduct, and thousands of tons of it are generated every year. Due to its chemical stability and limited applications, settlement of this waste issue has drawn extensive attention from chemists. The reduction of triphenylphosphine oxide to triphenylphosphine is heretofore the most employed solution, and is well reviewed. In view of our recent studies on the selective and efficient conversion of Ph3P(O) to other valuable organophosphorus chemicals by using sodium, the present perspective mainly highlights the advances on the utilization of Ph3P(O) to prepare a diverse range of functional organophosphorus compounds, except Ph3P, via selective P-C, C-H, and P-O bond cleavages.

Straightforward Synthesis of the Poly(ADP-ribose) Branched Core Structure

Poly(ADP-ribosyl)ation is a post-translational modification that produces poly(ADP-ribose) with a branched structure every 20-50 units; such branching structure has been previously suggested to be involved in regulating chromatin remodeling. To elucidate its detailed functions, we developed a straightforward method for the synthesis of the poly(ADP-ribose) branched core structure, α-d-ribofuranosyl-(1‴ → 2″)-α-d-ribofuranosyl-(1″ → 2')-adenosine 5',5'',5‴-trisphosphate 1, from 6-chloropurine ribofuranoside 4 in 10 steps and 6.1% overall yield. The structure poses synthetic challenges for constructing iterative α-1,2-cis-glycosidic bonds in the presence of a purine base and the installation of three phosphate groups at primary hydroxyl groups. Iterative glycosidic bonds were formed by α-1,2-cis-selective ribofuranosylation using 2-O-(2-naphthylmethyl)-protected thioglycoside donor 6 and a thiophilic bismuth promoter. After the construction of diribofuranosyl adenosine 5 had been constructed, it was chemo- and regioselectively phosphorylated at a later stage. Subsequent deprotection provided the synthetic target 1.

P-Chloride-Free Synthesis of Phosphoric Esters: Microwave-Assisted Esterification of Alkyl- and Dialkyl Phosphoric Ester-Acids Obtained from Phosphorus Pentoxide

It is a reasonable endeavour to replace P-chloride starting materials (e.g., POCl3) with greener and cheaper reagents. Our purpose was to start from phosphorus pentoxide, i.e. to utilize its reaction with alcohols in the preparation of (HO)2P(O)(OR) and HOP(O)(OR)2, and to convert the mixtures of the corresponding monoester and diester, so obtained, into the target trialkyl esters. Separate experiments showed that the monobutylphosphate undergo microwave (MW)-assisted esterification with butanol in the presence of [bmim][BF4] catalyst at 200 °C to afford dibutylphosphate in a selective manner (ca. 95%) that, in turn, may be converted into tributylphosphate by alkylation under MW irradiation. In this way, the mixtures of (HO)2P(O)(OR) and HOP(O)(OR)2 obtained by the practical reaction of phosphorus pentoxide and alcohol (ROH) could also be converted in two additional steps into the corresponding trialkyl esters. The three-step synthesis of trialkylphosphates starting from phosphorus pentoxide was also transformed in a one-pot (step 1: preparation of the monoester diester mixture, step 2: diesterification) and telescoping (step 3: triesterification) variation, avoiding the isolation and purification of the intermediates, and affording the triesters­ in 86–93% yields. The three- and two-step P-chloride-free methods developed are ‘green’ and of more general value.

Mild and Chemoselective Phosphorylation of Alcohols Using a Ψ-Reagent

An operationally simple, scalable, and chemoselective method for the direct phosphorylation of alcohols using a P(V)-approach based on the Ψ-reagent platform is disclosed. The method features a broad substrate scope of utility in both simple and complex settings and provides access to valuable phosphorylated alcohols that would be otherwise difficult to obtain.

Recent Progress in the Selective Functionalization of P(O)-OH Bonds

As we all know, organic phosphorus compounds have high application values in chemical industries. Compared with traditional compounds with P-X (X = Cl, Br, I) and P-H bonds, phosphorylation reagents containing P(O)-OH bonds are stable, environmentally friendly, and inexpensive. However, in recent years, there have been few studies on the selective functionalization of P(O)-OH bonds for the fabrication of P-C and P-Z bonds. In general, four-coordinated P(O)-OH compounds have reached coordination saturation due to the phosphorus atom center, but cannot evolve the phosphorus coordination center through intra-molecular tautomerization; however, the weak coordination effects between the P=O bond and transition metals can be utilized to activate P(O)-OH bonds. This review highlights the most important recent contributions toward the selective functionalization of P(O)-OH bonds via cyclization/cross coupling/esterification reactions using transition metals or small organic molecules as the catalyst.

Let's Make White Phosphorus Obsolete

Industrial and laboratory methods for incorporating phosphorus atoms into molecules within the framework of Green Chemistry are in their infancy. Current practice requires large inputs of energy, involves toxic intermediates, and generates substantial waste. Furthermore, a negligible fraction of phosphorus-containing waste is recycled which in turn contributes to negative environmental impacts, such as eutrophication. Methods that begin to address some of these drawbacks are reviewed, and some key opportunities to be realized by pursuing organophosphorus chemistry under the principles of Green Chemistry are highlighted. Methods used by nature, or in the chemistry of other elements such as silicon, are discussed as model processes for the future of phosphorus in chemical synthesis.

Zinc-Catalyzed Phosphonylation of Alcohols with Alkyl Phosphites

In the presence of a catalytic amount of either Zn(acac)₂ or bis(2,2,6,6-tetramethyl-3,5-heptanedionato)zinc(II) (Zn(TMHD)₂), primary, secondary, and tertiary alcohol substituents on a wide range of substrates, including acyclic and cyclic structures, carbohydrates, steroids, and amino acids, reacted with dimethyl phosphite to afford the corresponding H-phosphonate diesters in high to excellent yields.

Catalytic Chemoselective O-Phosphorylation of Alcohols

Phosphorylation of alcohols is a fundamentally important reaction in both life science and physical science. Product phosphate monoesters play key roles in living organisms, natural products, pharmaceuticals, and organic materials. Most of the chemical methods to date for synthesizing phosphate monoesters, however, require multistep sequences or are limited to specific types of substrates possibly due to harsh conditions. An alternative way to enable the simple production of phosphate monoesters from highly functionalized precursor alcohols is, thus, highly desired. We report herein a catalytic phosphorylation of alcohols with high functional group tolerance using tetrabutylammonium hydrogen sulfate (TBAHS) and phosphoenolpyruvic acid monopotassium salt (PEP-K) as the catalyst and phosphoryl donor, respectively. This method enables the direct introduction of a nonprotected phosphate group to the hydroxy group of a diverse menu of alcohol substrates, including functionalized small molecules, carbohydrates, and unprotected peptides. Nuclear magnetic resonance, mass spectrometric, and density functional theory analyses suggest that an unprecedented mixed anhydride species, generated from PEP-K and TBAHS, acts as an active phosphoryl donor in this reaction. This operationally simple and chemoselective catalytic phosphorylation allows for the efficient production of densely functionalized O-phosphorylated compounds, which are useful in diverse fields including biology and medicine.

Palladium-Catalyzed C-H Bond Functionalization Reactions Using Phosphate/Sulfonate Hypervalent Iodine Reagents

A new and operationally simple approach for palladium-catalyzed C-H functionalization reactions utilizing an organophosphorus/sulfonate hypervalent iodine reagent as both an oxidant and the source of a functional group has been developed. Through this method, the oxidative phosphorylation-, sulfonation-, and hydroxylation of unactivated benzyl C(sp³)-H bonds, along with the hydroxylation and arylation of aryl C(sp²)-H bonds, are successfully realized under mild conditions and with excellent site-selectivity. The versatile C-OSO₂R bond provides a platform for a wide array of subsequent diversification reactions.

Polyurethane ionomers based on amino ethers of ortho-phosphoric acid

The etherification of ortho-phosphoric acid with triethanolamine and polyoxypropylene glycol is studied. The reaction process is accompanied by the formation of hyperbranched amino ethers of ortho-phosphoric acid terminated by hydroxyl groups. A specific feature of the chemical structure of the compounds obtained is the existence of ion pairs in their structure separated in space. The reaction of the etherification of ortho-phosphoric acid with glycols becomes possible through the use of tertiary amines. The amino ethers of ortho-phosphoric acid are investigated as a polyol component for the synthesis of polyurethanes with high adhesion characteristics and strength properties. The experimental results presented allow us to relate polyurethanes obtained on the basis of ortho-phosphoric acid amino ethers to polymers of ionomeric nature.

The etherification of ortho-phosphoric acid with triethanolamine and polyoxypropylene glycol is studied.

Synthesis and Properties of Lauryl Phosphate Monoester

Lauryl phosphate monoester was synthesized from the starting materials lauryl alcohol and phosphoric acid without catalysts. Subsequently, the crude product was purified by recrystallization and characterized by Fourier transform infrared (FT-IR) and nuclear magnetic resonance (31P-NMR). From the results, it was apparent that the synthesized material was the desired target product. Lauryl monoester potassium phosphate reduced the surface tension of water to 25.08 mN/m at a critical micelle concentration (CMC) of 0.569 mmol/L. It showed a low contact angle and had a low surface tension, indicating a good hydrophilicity. Lauryl monoester potassium phosphate also showed excellent antistatic properties, however its emulsifying ability was not good. The size of the aggregates of lauryl monoester calcium phosphate in aqueous solution was 220 nm and their morphology was spherical.

Two novel bi-functional hybrid materials constructed from POMs and a Schiff base with excellent third-order NLO and catalytic properties

The first polyoxometalates modified by a porphyrin-resembling planar Schiff base have been successfully designed and synthesized under hydrothermal conditions. The third-order NLO responses indicated that they are excellent third-order NLO materials. Their catalytic performances are also investigated.

Binding of ReO4(-) with an engineered MoO4(2-)-binding protein: towards a new approach in radiopharmaceutical applications

Radiolabeled biomolecules are routinely used for clinical diagnostics. (99m)Tc is the most commonly used radioactive tracer in radiopharmaceuticals. (188)Re and (186)Re are also commonly used as radioactive tracers in medicine. However, currently available methods for radiolabeling are lengthy and involve several steps in bioconjugation processes. In this work we present a strategy to engineer proteins that may selectively recognize the perrhenate (ReO(4)(-)) ion as a new way to label proteins. We found that a molybdate (MoO(4)(2-))-binding protein (ModA) from Escherichia coli can bind perrhenate with high affinity. Using fluorescence and isothermal titration calorimetry measurements, we determined the dissociation constant of ModA for ReO(4)(-) to be 541 nM and we solved a crystal structure of ModA with a bound ReO(4)(-). On the basis of the structure we created a mutant protein containing a disulfide linkage, which exhibited increased affinity for perrhenate (K(d) = 104 nM). High-resolution crystal structures of ModA (1.7 Å) and A11C/R153C mutant (2.0 Å) were solved with bound perrhenate. Both structures show that a perrhenate ion occupies the molybdate binding site using the same amino acid residues that are involved in molybdate binding. The overall structure of the perrhenate-bound ModA is unchanged compared with that of the molybdate-bound form. In the mutant protein, the bound perrhenate is further stabilized by the engineered disulfide bond.

Radioactive phosphorylation of alcohols to monitor biocatalytic Diels-Alder reactions

Nature has efficiently adopted phosphorylation for numerous biological key processes, spanning from cell signaling to energy storage and transmission. For the bioorganic chemist the number of possible ways to attach a single phosphate for radioactive labeling is surprisingly small. Here we describe a very simple and fast one-pot synthesis to phosphorylate an alcohol with phosphoric acid using trichloroacetonitrile as activating agent. Using this procedure, we efficiently attached the radioactive phosphorus isotope (32)P to an anthracene diene, which is a substrate for the Diels-Alderase ribozyme-an RNA sequence that catalyzes the eponymous reaction. We used the (32)P-substrate for the measurement of RNA-catalyzed reaction kinetics of several dye-labeled ribozyme variants for which precise optical activity determination (UV/vis, fluorescence) failed due to interference of the attached dyes. The reaction kinetics were analyzed by thin-layer chromatographic separation of the (32)P-labeled reaction components and densitometric analysis of the substrate and product radioactivities, thereby allowing iterative optimization of the dye positions for future single-molecule studies. The phosphorylation strategy with trichloroacetonitrile may be applicable for labeling numerous other compounds that contain alcoholic hydroxyl groups.