Tertiary Phosphine Oxides in Reaction with Benzaldehyde

Symmetrical and unsymmetrical tertiary phosphine oxides containing benzyl and 5-chloro-2-thienyl radicals stereoselectively react with benzaldehyde in the sodium amide-THF system to form the E isomers of 1-organyl-2-phenylethene and diorganylphosphinic acids in high yields. Triethyl, tris(2-phenyl- ethyl)-, and tris[(4-methoxyphenyl)methyl]phosphine oxides under the above-mentioned conditions do not react with benzaldehyde.     

Synthesis of Tertiary Bisphosphine Oxides from Methylacetylene and Secondary Phosphine Oxides

Russian Journal of Organic Chemistry -     

New Insights into the Mechanism of Reduction of Tertiary Phosphine Oxides by Means of Phenylsilane

The mechanism of the reduction of phosphine oxides by PhSiH₃ was established on the basis of kinetic measurements and Density Functional Theory (DFT) calculations. In particular, it has been proved that the model reaction between tri‐n‐butylphosphine oxide and phenylsilane occurs via a nonpolar mechanism. The data presented herein allow prediction and verification of the applicability of the new reduction reagents and conditions for industrially attractive processes.     

The Concept of P--H Protection Extended to Phosphine Oxides: Preparation of Functional,Unsymmetrical Secondary and Tertiary Phosphine Oxides

Phosphine oxide analogues of Triazole fungicides and protected Threonine have been prepared. The enzymatic hydrolysis of phosphine oxide di-acetates has been investigated.     

Brønsted Acid Promoted Reduction of Tertiary Phosphine Oxides

Recently, Brønsted acids, such as phosphoric acids, carboxylic acids, and triflic acid, were found to catalyze the reduction of phosphine oxides to the corresponding phosphines. In this study, we fully characterize the HCl, HOTf, and Me₂SiHOTf adducts of triphenylphosphine oxide and find that the thermally stable adduct Ph₃POH⁺OTf^– is efficiently converted into triphenylphosphine at 100 °C in the presence of readily available hydrosiloxanes. Under the same reaction conditions, also Ph₃POSiMe₂H⁺OTf^– selectively affords triphenylphosphine indicating that silylated phosphine oxides are likely intermediates in this process.     

Coulombic Basis for Relative Hydrogen-Bonding Basicities and Conformational Energies of Tertiary Amine Oxides and Phosphine Oxides

The structures, energies, and natural atomic charges of 2-dimethylaminophenol oxide, 2-Me₂N-(O)C₆H₄OH, and 2-dimethylphosphinylphenol, 2-Me₂P(O)C₆H₄OH, in three different conformations were computed at the ab initio MP2/6-31G* level. Computed natural charges indicate distributions of electron density in amine oxides and phosphine oxides that are quite different from what is normally assumed on the basis of the formal charges in the usual representations of these compounds. The charges on nitrogen and phosphorus in these compounds are typically computed to be approximately zero on nitrogen and +2 on phosphorus, and the oxygen is considerably more negative in the phosphine oxide than in the amino oxide. Electronegativity differences thus play a larger role and formal charges a smaller one in determining atomic charges in these compounds than is generally believed. Despite the more negative oxygen in phosphine oxides, amine oxides are computed to be considerably more basic when participating in hydrogen bonding. Calculations treating the computed natural charges on these six conformations as point charges for classical approximations of the coulombic energies support the idea that the quantum mechanically computed relative energies are largely determined by coulombic interactions.     

New Dimethyl(Methylenoxyaryl)Phosphine Oxides

Abstract

In the poster presentation is reported the preparation of the new dimethyl(methylenoxyaryl)phosphine oxides via ZVilliamson reaction from dimethyl-chloromethyl-phoaphine oxide and sodium solts of the coresponding phenols: l-di-methylphosphinylmethylenoxy-4-methyl-2,6-bis(l,l -dimethylethyl)benzene; 1,3-bis(dimethylphosphinylmethylenOxy)benzene; 1,4-bis(dimethylphosphinylmethylenoxy)ben-zene; 1,3,5-tris(dimethylphosphinylmethylenoxy)benzene; 1,2,3-tris(dimethylphosphinylmethylenoxy～benzene; 2,2′-methylene-bia(6-tert-butyl-4-methyl-l-dimethyl-phosphinylmethylenoxybenzene); 2,2′-rnethylene-bis-(6-tert-butyl-4-ethyl-l-dimethylphosphinylmethyleno～-benzene) and 1,1,3-tris(5-tert-butyl-4-dimethylphoa-phinylmethylenoxy-2-methyl-phenyl)butan.     

The Reactivity of Cyameluric Chloride C6N7Cl3 towards Phosphines and Phosphine Oxides

Organophosphines (R₂PH) and phosphineoxides (R₂OPH) show a very high reactivity towards cyameluric chloride C₆N₇Cl₃. For example, 2,4,6‐trisdiphenylphosphino‐tri‐s‐triazine ( 1 ) forms quantitatively within a few seconds. Tris‐diphenylphosphinsulfide‐s‐heptazine ( 2 ) was obtained by reaction of 1 with sulfur. These compounds represent a new class of s‐heptazine derivatives which tend, unlike their s‐triazine analogues, to decompose in solution. 1 forms crystals with nitromethane, which were analysed by single‐crystal X‐ray diffraction. The nitromethane molecules fill the gaps in the crystal lattice supported by hydrogen bonds, C–H ··· π ring, and N–O ··· π ring interactions. All compounds were characterized by ¹H, ¹³C and ³¹P NMR and vibrational (FT‐IR, Raman) spectroscopy. The thermal stability of selected derivatives was measured by TG, indicating surprisingly low thermal decomposition temperatures.     

Synthesis of P-Stereogenic Phosphine Oxides via Nickel-Catalyzed Asymmetric Cross-Coupling of Secondary Phosphine Oxides with Alkenyl and Aryl Bromides

A general and mild nickel-catalyzed enantioselective C(sp²)−P cross-coupling for synthesizing P-stereogenic phosphine oxides has been developed. The asymmetric alkenylation/arylation of racemic secondary phosphine oxides with alkenyl/aryl bromides generated P-stereogenic phosphine oxides with high yields and enantioselectivities. Various functional groups were tolerated, and the applications of this method were demonstrated through late-stage functionalization and product transformations.     

Structure and Reactivity of Uracil Derivatives. 2. Ambident Nucleophilic Reactivity of 5-Diazouracil

On the basis of 3-21G type ab initio calculations we have studied all the possible complexes of 5-diazouracil with boron trifluoride. The most stable of these are the systems with the BF₃ coordinated at the 3, 9, and 10 positions of the heterocyclic molecule.     

Nucleophilic Reactivity of the Thiophosphoryl Group

The difference in the nucleophilic reactivities of the and groups can be satisfactorily explained on the basis of Pearson's acid-base concept^[21]. The thiophosphoryl sulfur is a typical “soft base”, and reacts preferentially with sub-group B metals, halogens, and sp³ hybridized carbon, whereas it is largely inert to “hard acids” such as protons, carbonyl carbon, and tetrahedral phosphorus. Since a nucleophilic attack by the thiophosphoryl sulfur leads to a decrease in the charge density of the phosphorus atom, the latter (or the α-carbon atom in O-alkyl esters) becomes more open to nucleophilic attack. This reaction principle forms the basis of sulfur exchange, dealkylation, isomerization, and the Pistschimuka and Michalski reactions.     

Reaction of Secondary Phosphine Oxides with Aromatic Aldehydes

Nucleophilic addition of secondary phosphine oxides to aromatic aldehydes proceeds under mild conditions (20-60°C, 10-40 h) and provides [bis(2-organylethyl)](arylhydroxymethyl)phosphine oxides in high yields.     

Pd-Catalysed Diastereoselective Synthesis of aza-Spirocyclic P-Stereogenic Phosphine Oxides

Phosphine oxides and spirocyclic compounds are privileged molecules widely employed in a variety of catalytic transformations either as chiral ligands for metals or bifunctional organocatalysts. Herein, we developed a Pd-catalysed cross-coupling reaction to synthesize spirocyclic amino-phosphine oxides with a P-stereogenic centre which could serve as potential P*(O), N-ligands or organocatalysis.     

Reactions of Elemental Phosphorus and Phosphines with Electrophiles in Superbasic Systems: XII. Synthesis of Unsymmetrical Tertiary Phosphine Oxides from Red Phosphorus and Organyl Halides

Alkyldibenzyl- and benzyldialkylphosphine oxides were prepared in one stage by direct phosphorylation of a mixture of alkyl bromides and benzyl chloride with red phosphorus under the conditions of phase-transfer catalysis (concentrated aqueous KOH solution-dioxane-benzyltriethylammonium chloride).     

P-手性膦氧化物的不对称催化合成研究进展

P-手性膦氧类化合物在药物化学、有机合成化学、生命及材料科学等领域具有重要的应用价值和潜能,是一类受到广泛关注的优势结构.近年来,针对这一结构的不对称催化构建取得了显著进展.本综述旨在从三级膦氧化物的去对称化反应和(动态)动力学拆分反应以及二级膦氧化物参与的不对称反应三种策略出发,介绍目前用于构建P-手性膦氧化物的不对称催化合成方法及最新研究进展.藉此也对这些反应的机理及其优势与不足之处进行简要讨论,为从事有机合成和有机膦化学相关的研究人员提供一些有益参考和借鉴.     

The Reactions of Dialkyl Phosphites and Phosphine Oxides with Iodosylbenzene

The reaction of iodosylbenzene with >P(O)H type of acids (dialkyl phosphites, secondary phosphine oxides) was studied. The acids of >P(O)H type add to iodosylbenzene to yield intermediate 6 which in the aprotic solvents yields oxidation products, it means >P(O)OH acids and/or anhydride of >P(O)OP(O)< type. On the other hand if the reaction is performed in alcohol as a solvent in the presence of sodium alcoholate >P(O)OR ester is the major product.     

The Reactivity of Silylsulfides with Disulfides: A New Aspect of the Thiol-Disulfide Interchange

Abstract

In this communication we report the silylsulfide-disulfide interchange which can be considered a novel aspect of the well known and widely studied thiol-disulfide interchange.     

Nucleophilic Solvent Participation in the Solvolysis of Tertiary Bromoalkanes

The solvolysis of 2‐bromo‐2‐methylpropane ( 1B ), 2‐bromo‐2‐methylbutane ( 2B ), 2‐bromo‐2, 3‐di‐methylbutane ( 3B ), 2‐bromo‐2, 3, 3‐trimethylbutane ( 4B ), 3‐bromo‐3‐methylpentane ( 5B ), 3‐bromo‐2, 3‐dimethylpentane ( 6B ), 3‐bromo‐2, 2, 3‐trimethylpentane ( 7B ), 3‐bromo‐3‐ethylpentane ( 8B ), 3‐bromo‐3‐ethyl‐2‐methylpentane ( 9B ) and 2‐bromo‐2, 4, 4‐trimethylpentane ( 11B ) in 15 to 21 solvents was studied, and correlation analyses by using the single‐ and dual‐parameter Grunwald‐Winstein equations (Eqns 1 and 2) were examined. Substrates 7B, 9B and 11B showed excellent linear relationship (R ≥ 0.997) in the logk ‐ Y_Br plots and indicated limiting S_N1 mechanism for the solvolysis. On the other hand, bromides 1B‐6B and 8B gave linear correlations (R = 0.987–0.996) with the dual‐parameter (Y_Br and N_OTs) equation (2) only, which indicated the presence of significant nucleophilic solvent participation. Normal trends of reactivity due to the relief of B‐strain could be found in the poorly nucleophilic trifluoroethanol. Similar to the corresponding chlorides, the overwhelming influence of nucleophilic solvent assistance results in the observed inverse order of reactivity: k( 2B ) > k( 3B ), k( 5B ) > k( 6B ) and k( 8B ) > k( 9B ).     

锰铈二元氧化物的制备与应用

Mn-Ce二元氧化物具有资源丰富、成本低廉、催化活性优异等优点,引起了科研人员的广泛关注,在诸多领域具有潜在的应用价值。本文详细阐述了Mn-Ce二元氧化物的合成方法和应用领域。合成方法包括沉淀法、溶胶-凝胶法、水热法、浸渍法等,并比较了各方法的优缺点。在应用方面,主要综述了Mn-Ce二元氧化物在空气污染物消除(消除NO_x、VOCs、CO、碳烟、Hg⁰、甲醛)和能源储存(金属-空气电池、超级电容器)两个方面的应用及其作用机制。另外,本文还介绍了Mn-Ce二元氧化物在水污染治理(氟离子吸附、三价砷吸附和甲基橙吸附等)和有机催化合成方面的应用。最后,讨论了Mn-Ce二元氧化物在制备中存在的问题,并对之后的研究方向进行了展望。