Ladder‐Type π‐Conjugated 4‐Hetero‐1,4‐dihydrophosphinines: A Structure–Property Study

π‐Conjugated six‐membered 1,4‐dihydrophosphinines containing a heteroatom (Si, P, S) at the 4 position were synthesized and systematically studied. X‐ray crystallographic analyses showed that the central six‐membered heterocyclic rings are almost planar. The sum of the angles around the phosphorus atom increases by 23° from the trivalent phosphorus to the phosphonium atom in the thiaphosphinine system, which is consistent with the NMR spectroscopic studies. UV/Vis spectroscopy and theoretical calculations revealed that the communication between the phosphorus center and the benzothiophene moiety is enhanced by the incorporation of a sulfur atom into the molecular scaffold. The increased conjugation endows the thiaphosphinines with interesting emission properties. Theoretical calculations supported the postulation that the orbital coupling between the π system and a σ* orbital could be enhanced in the thiaphosphinine system, especially through a phosphonium center. Cyclic voltammetry studies revealed that the thiaphosphinine oxide, thiaphosphonium, and cis‐diphosphinine oxide exhibit quasi‐reversible reduction processes, which demonstrate that simple changes in the bridge heteroatoms help to efficiently tune the redox properties of the ladder‐type 4‐hetero‐1,4‐dihydrophosphinines.     

Imide-amide rearrangement of oxazaphosphorimidates: studies towards the application to the synthesis of chiral Lewis bases

The Lewis acid catalysed imide-amide rearrangement of oxazaphosphorimides to diazaphoshoramides is reported for the first time. In spite of the similarity to the previously reported Lewis acid catalysed imide-amide rearrangement of dioxaphosphorimides to oxazaphosphoramides we show that this rearrangement proceeds by a different mechanism, not involving the formation of an oligomeric intermediate. The oxazaphosphorimides are prepared in situ by the Staudinger reaction of the appropriate trivalent phosphorus compound with an azide and after the addition of BF₃·OEt₂, undergo rearrangement to the corresponding diazaphosphoramides. We have found that the rearrangement occurs with retention of configuration at the phosphorus atom and inversion of configuration at the rearranged carbon atom. When starting from chiral 1,2-aminoalcohol, substituted at the carbon atom that undergoes rearrangement, a mixture of diastereomers is obtained, but the diastereomeric ratio, initially obtained in the formation of the trivalent phosphorus compounds is maintained during the whole transformation. This implies that if the rearrangement is to be used for the preparation of chiral phosphoramides with defined stereochemistry at the phosphorus atom, a high diastereoselectivity during the preparation of the trivalent phosphorus precursors should be obtained.     

Reaction of N-chloromethyldiethylamine,N-chloromethylbenzamide,N-chloromethylphthalimide with amides of trivalent phosphorus acids

Conclusions In the series of N-chloromethylphthalimide, N-chloromethylbenzamide, N-chloromethyldiethylamine, in reactions with amides of trivalent phosphorus acids, the contribution of the reaction at the phosphorus atom increases with increase in the polarity of the C-Cl bond. N-Chloromethylphthalimide, whose C-Cl bond is least polar in this series, reacts with hexaethyltriamidophosphite and diethylamidodiphenylphosphinite reacts at the N and P atoms to form the corresponding quasiphosphonium salts and acid chlorides of trivalent phosphorus acids.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 173–178, January, 1985.     

Pushing the Lewis Acidity Boundaries of Boron Compounds With Non‐Planar Triarylboranes Derived from Triptycenes

Bending the planar trigonal boron center of triphenylborane by connecting its aryl rings with carbon or phosphorus linkers gave access to a series of 9‐boratriptycene derivatives with unprecedented structures and reactivities. NMR spectroscopy and X‐ray diffraction of the Lewis adducts of these non‐planar boron Lewis acids with weak Lewis base revealed particularly strong covalent bond formation. The first Lewis adduct of a trivalent boron compounds with the Tf₂N^? anion illustrates the unrivaled Lewis acidity of these species. Increasing the pyramidalization of the boron center and using a cationic phosphonium linker resulted in an exceptional enhancement of Lewis acidity. Introduction of a phosphorus and a boron atom at each edge of a triptycene framework, allowed access to new bifunctional Lewis acid‐base 9‐phospha‐10‐boratriptycenes featuring promising reactivity for the activation of carbon‐halogen bonds.     

Phosphorus-based heteropentacenes: efficiently tunable materials for organic n-type semiconductors

Benzo-condensed dithieno[3,2-b:2',3'-d]phospholes have been synthesized that allow convenient tuning of properties that are essential for application as semiconductor materials in organic field-effect transistor (OFET) devices. The versatile reactivity of the trivalent phosphorus atom in these heteropentacenes provides access to a series of materials that show different photophysical properties, significantly different organization in the solid state, and distinctly different electrochemical properties that can be achieved by simple chemical modifications. The materials show strong photoluminescence in solution and in the solid state that depends on the electronic nature of the phosphorus center. Electrochemical studies revealed that the phosphorus atom intrinsically furnishes materials with n-channel or ambipolar behavior, also depending on its electronic nature. The experimental data were verified by DFT quantum chemical calculations and suggest that the phosphorus-based heteropentacenes could be excellent candidates for n-channel OFET semiconductor materials.     

Phosphorylated Allenes in the Cycloaddition Reactions

Abstract

The reactions of phosphorus-containing allenes with the derivatives of phosphorus of low coordination are investigated. The interaction of the l -vinyl-l-phosphoryloxy-3,3-di-methylallene with (dimethylaminomethylidene)phenylphosphine was shown to occur over 1,3-diene system according to Diels-Alder reaction. The formation of the six-membered heterocycle was accompanied by changing the coordination of the phosphorus atom from P^II to P^III. The reaction of the phosphorus containing 1,3-dipole (diethylaminobenzylidene)-aminodimethoxyphosphine with 1-vinyl-1-phosphoryloxy-3,3-dimethylallene was found to give the seven-membered aza-phosphepin. The changing of methoxy-radicals by ethoxy-groups in benzylideneaminophosphine leads to azaphos-phorins as products. The formation of the seven-membered adduct in this case is small. The two-step mechanism of these reactions with the initial attack of atom P at central carbon atom of allene is in agreement with kinetic, thermochemical and ³¹P-NBR data.     

Arine als elektrophile Reagentien, 1. Mitt.: Umsetzung mit Alkylen-phosphoranen

Arines, which may be considered as electrophilic reagents, react with Alkylenephosphorances (Ar)₃P-C(R₁)(R₂) attacking principally the nucleophilic C atom. The resulting zwitterion A (Ar)₃P⊕?C(R₁)(R₂)(o-C₆H₄)? form the more stable Benzophospha-cyclobutane-derivative with pentavalent phosphorus. This finally undergoes a rearrangement, in which the phosphorus atom passes over from the pentavalent into the trivalent state. The corresponding phosphine possesses the following general structure, as far as could be observed.

$$(Ar)_2 P---(o--) \cdot C_6 H_4 ---C(R_1 )(R_2 )(Ar).$$     

1H,4H-1,4-diborabuckminsterfullerene with pyridine molecules and ytterbium endo-atom

The competition between the ytterbium endo-atom and the pyridine exo-molecules as nucleophiles interacting with the electron-deficient 1H,4H-1,4-diborabuckminsterfullerene was studied using the quantum chemical DFT PBE0 method. The equilibrium structural parameters, dipole moments, IR spectra, and exothermic effects of the formation of the C₅₈B₂•Py₂ adduct and the endohedral Yb@C₅₈B₂•Py₂ complex were determined. The concept of the state of oxidation/reduction of an atom in a chemical compound has been clarified. The localization of the ytterbium(II) under a pair of equivalent carbon atoms bonded to boron(III) atoms is predicted. The introduction of ytterbium(II) into the adduct cavity weakens exo-bonds with pyridine molecules without changing the oxidation state of boron(III). Each nitrogen atom retains a lone electron pair, coordinated by a boron(III). The ytterbium(II) endo-atom retains 14 electrons in f states.     

Vibrational spectra and structures of a number of oxaazaphospholanes

The Raman and IR spectra of six 1,3,2-oxaazaphospholanes with a tri- and tetracoordinated phosphorus atom were obtained. The bands were assigned, and the spectroscopic features of the oxaazaphospholane ring were noted. Assumptions regarding the peculiarities of the three-dimensional structure of the molecules were made on the basis of the change in the characteristic frequencies on passing from trivalent phosphorus compounds to tetracoordinated phosphorus compounds.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1612–1615, December, 1971.     

Hydroxyoligophosphites and -Phosphonites on the Basis of 1,4:3,6-Dianhydro-D-sorbitol

The interaction of 1,4:3,6-dianhydro-D-sorbitol with phosphorous and phenylphosphonous acid amidochlorides leads to oligophosphites and -phosphonites with free hydroxyl groups on the periphery of their molecules. The obtained compounds were introduced into reactions via the transformation of trivalent phosphorus and hydroxyl groups.     

STEREOSELECTIVE REACTIONS OF CHIRAL AMINES WITH RACEMIC CHLOROPHOSPHINES

Racemic chlorophosphines react stereoselectively with chiral l-phenylethylamines or amino acid esters to give diastereomerically enriched aminophosphines 3, which were isolated as diastereomerically pure crystalline borane complexes. Oxidation, thionation, the reaction with methyl iodide provide optically active derivatives of aminophosphines. (R,S)- and (S,S)-stereomers of phosphinic acid amides were separated by crystallization and a flash-chromatography. The stereochemical properties of phosphorus acid amides were investigated. The mechanism of asymmetric induction at the trivalent phosphorus atom was rationalized.     

Stereoselective reactions of trivalent phosphorus compounds

The data on stereoselective reactions of achiral compounds of trivalent phosphorus with chiral nucleophiles (derivatives of secondary alcohols, amines, and amino acids) are analyzed and discussed. In certain cases, these reactions enable preparation of optically active aminophosphines and phosphinites, precursors in the synthesis of chiral organophosphorus compounds and phosphine ligands. The reactions are suitable for elucidation of mechanism and stereochemistry of nucleophilic substitution at trivalent phosphorus atom.     

Predictive elucidation of conformational characteristics and configurational properties of poly(1-methylphosphirane) and poly(1-phenylphosphirane) as a molecular design

Conformational characteristics and configurational properties of poly(1-methylphosphirane) (PMePP) and poly(1-phenylphosphirane) (PPhPP) have been predictively elucidated by the refined rotational isomeric state scheme coupled with ab initio molecular orbital and density functional calculations. The lone pair of the phosphorus atom adopts an sp hybrid orbital. Owing to the high s character (50%), the polyphosphiranes exhibit low proton (hydrogen) affinities, and hence the lone pair does not form any intramolecular attractive interactions with hydrogen. As the meso-diad probability varies from 0 (syndiotactic) to 1 (isotactic), the characteristic ratio of PMePP slightly increases from 6.7 to 7.4, whereas that of PPhPP considerably decreases from 38 to 7.3. The large dimension of syndiotactic PPhPP is chiefly due to π-π attractions formed between adjacent phenyl groups. The trivalent phosphorus atom may be bonded to heavy, noble, and transition metals but readily or gradually oxidized. The usefulness and necessity of the polyphosphiranes have been assessed.     

Reactions ofβ-chloroethyl derivatives of tricoordinated phosphorus acids with 1-nitro-1-propene

Conclusions The reactions of the-chloroethyl derivatives of trivalent phosphorus acids proceed via an ionic intermediate, which, depending on the experimental conditions, is stabilized in the direction of ring closure to give an adduct with a pentacovalent phosphorus atom and the formation of the corresponding unsaturated and (-methyl--nitroethyl)phosphoryl compounds. The liberated-chloroethyl nitrite functions as an oxidizing agent of the starting-chloroethyl derivatives of trivalent phosphorus acids.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1398–1401, June, 1978.The authors thank É. I. Gol'dfarb for taking the³¹P–{¹H} NMDR spectra.     

Reactions of areneselenenamides with alkenes in the presence of phosphorus(V) and sulfur(IV) oxyhalides. New synthesis of β-haloalkyl selenides

A new procedure was proposed for activation of areneselenenamides with phosphorus(V) and sulfur(IV) oxyhalides. According to the ¹H, ¹³C, and ³¹P NMR data, areneselenenamide reacts with phosphorus oxyhalide to form intermediate adduct in which the phosphorus atom is coordinated at the selenium. Areneselenenamides activated by phosphorus(V) oxyhalides react with alkenes (norbornene and norbornadiene) with high trans-stereoselectivity. Their reactions with terminal olefins are regioselective, and they lead to preferential formation of the corresponding Markovnikov adducts.     

Reaction of diphenylphosphine oxide with a 10-methylacridinium salt. Reversible formation of a P?C covalent bond

Diphenylphosphine oxide ( 1 ′) reacts reversibly with a 10-methylacridinium salt ( 2 ) in acetonitrile at 20°C to equilibrate with a new salt 3 formed by the addition of 1 ′ to the cation of 2 . The forward reaction in this equilibrium proceeds via nucleophilic attack by the phosphorus atom of diphenylphosphinous acid ( 1 ), the trivalent tautomer of 1 ′, upon the 9-carbon atom of the cation of 2 , forming a phosphorus–carbon covalent bond. The equilibrium constant has been determined by UV-vis and ¹H NMR spectroscopy as well as by HPLC analysis. The reaction has been analyzed kinetically, and the results have been compared with those obtained in the similar reaction of an alkyl ester of 1 , the diphenylphosphinite ( 5 ), with 2 that gives the phosphonium salt 6 . It is suggested that 6 is much more stable than 3 . The equilibrium constant for the tautomerism between 1 ′ and 1 has also been estimated. © 1995 John Wiley & Sons, Inc.     

C-phosphorylation of formaldehyde and crotonaldehydeN,N-dimethylhydrazones

The first representatives of hydrazones having trivalent phosphorus at the azomethine carbon atom or the carbon atom vinylogous to it were synthesized by reactions of formaldehyde and crotonaldehydeN,N-dimethylhydrazones with PBr₃ and diphenylchlorophosphine in the presence of organic bases. Some properties of the compounds synthesized were studied. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1797–1801, September, 1998.     

Electrochemical approaches to generation of phosphinidene complexes of tungsten pentacarbonyl

An alternative approach to synthesis of electrophilic terminal phosphinidene complexes of tungsten pentacarbonyl with various substituents at the phosphorus atom has been developed. The approach is based on the reaction of the electrochemically generated tungsten pentacarbonyl ion with trivalent phosphorus acyl chlorides. Electrochemical reduction of ethyldichlorophosphines in the presence of α-diimines is a one-step process that forms 1,3,2-diazaphospholenes containing an exocyclic P-C bond.     

Dibenzophosphaborin: a hetero-pi-conjugated molecule with fluorescent properties based on intramolecular charge transfer between phosphorus and boron atoms

[reaction: see text] The first dibenzo-1,4-phosphaborins were synthesized and characterized by X-ray crystallographic analysis. The phosphaborins exhibited UV/vis absorption derived from intramolecular charge transfer from the phosphorus atom to the boron atom. The phosphaborins showed different fluorescent properties depending on the substituents on the phosphorus atom.     

PAH formation under single collision conditions: reaction of phenyl radical and 1,3-butadiene to form 1,4-dihydronaphthalene

The crossed beam reactions of the phenyl radical (C(6)H(5), X(2)A(1)) with 1,3-butadiene (C(4)H(6), X(1)A(g)) and D6-1,3-butadiene (C(4)D(6), X(1)A(g)) as well as of the D5-phenyl radical (C(6)D(5), X(2)A(1)) with 2,3-D2-1,3-butadiene and 1,1,4,4-D4-1,3-butadiene were carried out under single collision conditions at collision energies of about 55 kJ mol(-1). Experimentally, the bicyclic 1,4-dihydronaphthalene molecule was identified as a major product of this reaction (58 ± 15%) with the 1-phenyl-1,3-butadiene contributing 34 ± 10%. The reaction is initiated by a barrierless addition of the phenyl radical to the terminal carbon atom of the 1,3-butadiene (C1/C4) to form a bound intermediate; the latter underwent hydrogen elimination from the terminal CH(2) group of the 1,3-butadiene molecule leading to 1-phenyl-trans-1,3-butadiene through a submerged barrier. The dominant product, 1,4-dihydronaphthalene, is formed via an isomerization of the adduct by ring closure and emission of the hydrogen atom from the phenyl moiety at the bridging carbon atom through a tight exit transition state located about 31 kJ mol(-1) above the separated products. The hydrogen atom was found to leave the decomposing complex almost parallel to the total angular momentum vector and perpendicularly to the rotation plane of the decomposing intermediate. The defacto barrierless formation of the 1,4-dihydronaphthalene molecule involving a single collision between a phenyl radical and 1,3-butadiene represents an important step in the formation of polycyclic aromatic hydrocarbons (PAHs) and their partially hydrogenated counterparts in combustion and interstellar chemistry.