Stereodivergently asymmetric synthesis of chiral phosphorus compounds by synergistic combination of ion-pair catalyst and base

Stereodivergently constructing the designed products having adjacent multi-stereocenters via a given reaction,with excellent control of both absolute and relative configurations,presents one of the substantial hurdles in asymmetric catalysis.Herein,we report a precisely stereodivergent asymmetric protocol by synergistic combination of phosphonium-involved ion-pair catalysis and base for accessing to chiral phosphorus compounds bearing two adjacent chiral centers particularly containing an acidic protonated enantioenriched carbon atom,having broad functional group compatibility in both dynamic and thermodynamic processes under mild reaction conditions.Two keys for the success in constructing these stereoisomers with high levels of regio-,diastereo-,and enantioselectivities were contained:firstly,the precise stereo-control in providing dynamic products was enabled by bifunctional phosphonium salt catalyst with semi-enclosed cavity;secondly,the readily stereospecific transformation of adducts from dynamic to thermodynamic version was initiated by achiral base.All four stereoisomers could be readily accessed even in gram-scale in high yields with maintaining excellent stereoselectivities,illustrating the potential of this synergistic catalytic methodology in organic synthesis.Moreover,mechanistic studies including density functional theory(DFT)calculations and control experiments provide insights into the mechanism.

The Generation of a Reduced Mechanism for Flame Inhibition by Phosphorus Containing Compounds Based on Path Flux Analysis Method

In order to analyze the complex chemical kinetic mechanism systematically and find out the redundant species and reactions, a numerical platform for mechanism analysis and simplification is established basing on Path Flux Analysis （PFA）. It is used to reduce a detailed mechanism for flame inhibited by phosphorus containing compounds, a reduced mechanism with 65 species and 335 reactions is obtained. The detailed and reduced mechanism are both used to calculate the freely-propagating premix C3H8/air flame with different dimethyl methylphosphonate doped over a wide range of equivalence ratios. The concentration distributions of free radicals and major species are compared, and the results under two different mechanisms agree well. The laminar flame speed obtained by the two mechanisms also matches well, with the maximum relative error introduces as a small value of 1.7%. On the basis of the reduced mechanism validation, the correlativity analysis is conducted between flame speed and flee radical concentrations, which can provide information for target species selection in the further mechanism reduction. By analyzing the species and reactions fluxes, the species and reaction paths which contribute the flame inhibition significantly are determined.

The role of 3d orbitals in the bonding of phosphorus compounds

Ab initio LCAO-MO-SCF calculations for several typical molecules containing phosphorus have been undertaken to study the role of phosphorus 3d orbitals in the bonding.It is emphasized that the discussion about the 3d orbital participation in bonding should be based on a reasonable choice of basis sets and it seems suitable to choose the atomic orbitals in proper molecular environment as the basis set.As an approximation,the optimized minimal STO-NG basis sets have been adopted in the present paper.The results obtained well exhibit the model of 3d orbital participation in bonding. It is shown that under the influence of highly electronegative ligands the phosphorus 3d orbitals con- tract greatly,their energy levels drop considerably,and thus they can effectively participate in bond- ing.The presence of highly electronegative ligands seems necessary.The contribution of 3d orbitals to bonding is achieved mainly through the concertedformation of σ bonds and p-d backbonds,though the contribution to σ bonding is minor.The three-center,four-electron bond modelis only approxi- mately correct.The results of the present paper demonstrate that the model of 3d orbital participation in bonding favoured by experimental chemists is reasonable and possesses sound ground.

Synthesis of 2-methoxy-6-oxo-1, 4, 2-diazaphosphorinane-2-oxide, A New Potential Antitumor Phosphorus Heterocycle Compound

2-methoxy-6-oxo-1, 4, 2-diazaphosphorinane-2-oxide 8, phosphorus counterpart of 2, 6-dioxopiperazine, was synthesized as antitumor agent. The new phosphorus heterocycle compound 8 is the key intermediate in the synthesis of phosphorus counterpart of bisdioxopiperazine.

SYNTHESIS OF FUSED PHOSPHORUS HETEROCYCLIC COMPOUNDS(II)

Using cation exchange resin(D72,Amberlyst-15) as catalyst, Mannich-type reaction of 5-amino-1,2,4-triazole 1, containing guanidine substructure, provides an efficient synthesis of a new kind of bicyclic P- and N-containing compounds, 6-phospha-4,5,6-trihydroimidazolo [2,3-e] 1,2,4-triazole 4.

Extraction of Tungsten and Molybdenum by Various Organic Compounds as Extractants

Seventy organic compounds including various organophosphorus esters, amines and oxygen-based ligands were investigated as extractants. The experiment results show that amines are excellent extractants for W and Mo. Their sequence of extraction ability for W is as follows: quarternary amine > tertiary amine > secondary amine > primary amine. Acidic organophosphorus extractants do not extract W, but can extract Mo with high extraction ability from the acidic solution. These extractants could provide a potential process for separating W from Mo.

Structural Characterization of ((S)-2＇-Hydroxy-1,1＇- binaphthalen-2-yl)-(SP)-vinylphosphonate Synthesized by the Chiral Induced Diastereoselective Reaction

Ethyl（（S）-2＇-hydroxy-1,1＇-binaphthalen-2-yl）-（SP）-vinylphosphonate （SBINOL-SP） was synthesized by diastereoselective reaction and characterized by means of NMR spectroscopy, H RMS and X-ray diffraction. The single crystal belongs to the monoclinic system, space group P21/c with a = 7.4983（13）, b = 12.065（2）, c = 21.805（4） ？, β = 90.094（6）°, Mr = 404.38, V = 1972.6（6） ？3, Z = 4, Dc = 1.362 g/cm3, F（000） = 848, μ = 0.168 mm-1, R = 0.0280 and wR = 0.0743. The title compound shows good activities against E. coli, S. albus, B. subtilis and M. tetragenus.

Search for New Opportunities Modification Raschig, Schiff, Andrusov, Hofmann, Colbe and Delepine Reactions

We explored new approaches to replace the nitrogen atoms of arsenic, antimony, bismuth, and discovered a new paths to modify Raschig, Schiff, Andrusov, Hofmann, Colbe, Delepine reactions with arsine, stibine and bismuthine in organometallic chemistry. We have proposed a new mechanism for possible reactions.

Phosphatase activity and culture conditions of the yeast Candida mycoderma sp. and analysis of organic phosphorus hydrolysis ability

Orthophosphate is an essential but limiting macronutrient for plant growth. About 67% cropland in China lacks sufficient phosphorus, especially that with red soil. Extensive soil phosphorus reserves exist in the form of organic phosphorus, which is unavailable for root uptake unless hydrolyzed by secretory acid phosphatases. Thus, many microorganisms with the ability to produce phosphatase have been exploited. In this work, the activity of an extracellular acid phosphatase and yeast biomass from Candida mycoderma was measured under different culture conditions, such as pH, temperature, and carbon source. A maximal phosphatase activity of 8.47 × 10^5±0.11× 10^5 U/g was achieved by C. Mycoderma in 36 hr under the optimal conditions. The extracellular acid phosphatase has high activity over a wide pH tolerance range from 2.5 to S.0 （optimum pH 3.5）. The effects of different phosphorus compounds on the acid phosphatase production were also studied. The presence of phytin, lecithin or calcium phosphate reduced the phosphatase activity and biomass yield significantly. In addition, the pH of the culture medium was reduced significantly by lecithin. The efficiency of the strain in releasing orthophosphate from organic phosphorus was studied in red soil （used in planting trees） and rice soil （originating as red soil）. The available phosphorus content was increased by 230% after inoculating 20 days in rice soil and decreased by 50% after inoculating 10 days in red soil. This work indicates that the yeast strain C. mycoderma has potential application for enhancing phosphorus utilization in plants that grow in rice soil.

Penta-coordinate phosphorous compounds and biochemistry

The relationship between penta-coordinate phosphorus compounds and biochemistry is briefly reviewed. Some interesting phenomena such as peptide formation, ester formation, ester exchange on phosphorus and N to O migration occur at room temperature when the amino group of amino acid is associated with phosphoryl group. Serine or threonine in conjugate of nucleo-side-amino acid could recognize different nucleobases. N-phosphoryl Histine and Ser-His dipep-tide could cleavage nucleic acid, protein and ester in neutral medium. It is found that the above phenomena all undergo penta-coordinate intermediate of phosphorus atom, which is proposed as the key factor to determine their activities.

Ligand Exchange Between Penta-Coordinated Phosphoryl Serine and Histidine Compounds

With the assistance of HPLC-ESI-MS/MS,the self-assembly products of serine and histidine penta-coordinated phosphorus compound were separated and identified. The expectative product was seryl-histidine dipeptide,but it was found that there was almost equimolar amount of histidyl-histidine dipeptide as well as seryl-histidine dipeptide. The mechanism was speculated that there was ligand exchange between penta-coordinated phosphoryl serine and histidine in the reaction process. As a result,two types of dipeptide were produced.

Synthesis of chiral allylic phosphonates via asymmetric reductive cross-coupling of α-bromophosphonates and vinyl bromides

Chiral phosphine-containing skeletons play a pivotal role in bioactive natural products, pharmaceuticals, chiral catalysts, and ligands. Despite considerable progress has been made in the synthesis of chiral phosphorus compounds, the development of facile and modular methods to access chiral allylic phosphorus compounds remains challenging due to the simultaneous control required for reactivity, enantioselectivity, and stereoselectivity. Herein, we present a general and modular platform to achieve the asymmetric reductive cross-coupling of α-bromophosphonates and vinyl bromides, enabling the synthesis of highly valuable chiral allylic phosphonate products with remarkable yields, enantioselectivities, and stereoselectivities.

A DFT study of two-dimensional P_2Si monolayer modified by single transition metal(Sc-Cu)atoms for efficient electrocatalytic CO_(2)reduction

In the present work,a stable two-dimensional(2D)P_(2)Si monolayer was predicted.The monolayer is semimetallic/metallic under the PBE/HSE06 functional and is mechanically isotropic.The stability of the P_(2)Si monolayer has been proved via cohesive energy,mechanical criteria,molecular dynamics simulation,and phonon dispersion respectively,and the monolayer possesses high carrier mobility which is three times that of Mo S_(2).On the other hand,the catalytic performance of the P_(2)Si monolayer modified with a single transition metals(M=Sc-Cu)atom for the electrochemical reduction of CO_(2)was investigated,and the monolayer can catalyze CO_(2)with three constraints:stable molecular dynamics,high migration potential of metal atoms,and suitable band gap for electrocatalyst after metal doping exhibiting excellent catalytic stabilization activity and CRR selectivity.In addition,the reduction product of V@P_(2)Si is HCOOH with an overpotential as low as 0.75 V,and the most suitable reaction path is^(*)CO_(2)→^(*)CHOO→O^(*)CHOH→^(*)+HCOOH with the final reduction product HCOOH obtained.As a whole,the above results endow the P_(2)Si monolayer to be a good 2D material holding great promises for applications in nanoelectronics and CO_(2)reduction catalysts.