Nitrogen- and oxygen-bridged bidentate phosphaalkene ligands

An overview is given on synthesis and structures of new bidentate phosphaalkene ligands [(RMe₂Si)₂CP]₂E (E = O, NR, N^?) and (RMe₂Si)₂CPN(R′)PR′′₂. Exceptional properties of these ligands, extending beyond predictable properties of phosphaalkenes are: (i) the NSi bond cleavage of [(iPrMe₂Si)₂CP]₂NSiMe₃ with Au^I and Rh^I chloro complexes under mild conditions leading to binuclear complexes of the 6π-delocalised imidobisphosphaalkene anion [(iPrMe₂Si)₂CP]₂N^?, and (ii) the chlorotropic formation of molecular 1:2 Pd^II and Pt^II metallochloroylid complexes with novel ylid-type ligands [(RMe₂Si)₂CP(Cl)N(R)PR₂]^?, and the transformation of a P-platina-P-chloroylid complex into a C-platina phosphaalkene by intramolecular chlorosilane elimination. Properties of the heavier congeners [(RMe₂Si)₂CP]₂E (E = S, Se, Te, PR, P^?, As^?) and (RMe₂Si)₂CPEPR′′₂ (E = S, Se, Te) are also described.     

Recognition of ionic guests by ionic beta-cyclodextrin derivatives

Inclusion compounds of cationic, anionic, and neutral p-substituted derivatives of tert-butylbenzene complexed in beta-cyclodextrin and its ionic 6-mono and 6-hepta derivatives were systematically investigated by isothermal titration calorimetry (ITC). All inclusion compounds showed 1:1 stoichiometry with binding constants ranging from 10 to 3 x 10(6) M(-1). The binding free energies could be subdivided into apolar and electrostatic contributions. The electrostatic interactions could be quantitatively described by Coulomb's law by taking into account the degree of protonation of hosts and guests, the orientations of the guests within the hosts, and ion shielding as described by the Debye-Hückel-Onsager theory. The orientations of the guests within the cyclodextrin cavities were determined by ROESY NMR spectroscopy.     

Unprecedented solvent-induced acceleration of free-radical propagation of methyl methacrylate in ionic liquids

The rate of propagation in the free-radical polymerization of methyl methacrylate in an ionic liquid has been determined and shows unprecedented solvent-induced acceleration, partially explaining the surprising increase in overall rates of polymerization and molecular weights in these solvents.     

Preparation of ortho-aryl-benzaldehyde derivatives via free-radical ipso-substitution of an amidomethyl group

Preparation of 2-biarylcarbaldehydes using an intramolecular free-radical ispo-substitution is described. The two aryl moieties to be coupled are pre-associated using a glycolamide derivative. An unusual amidomethyl leaving group was successfully employed in this process.     

Synthesis of 3,3,4,4-tetrafluoro-4-iodobutylamine,a bifunctional reagent for ionic and free-radical reactions

1,1,2,2-Tetrafluoro-1,4-diiodobutane reacts with NaN3 under phase-transfer catalysis conditions to give 3,3,4,4-tetrafluoro-4-iodobutyl azide. The reduction of the azide with triphe-nylphosphine followed by hydrolysis of intermediate iminophosphorane affords 3,3,4,4-tetra-fluoro-4-iodobutylamine.     

Effect of heterocyclic derivatives of ferrocene on free-radical polymerization of methyl methacrylate and styrene

The free-radical bulk homopolymerization of methyl methacrylate and styrene initiated by benzoyl peroxide or AIBN in the presence of heterocyclic derivatives of ferrocene is studied. It is shown that, in the case of the peroxide initiator, ferrocene derivatives form highly efficient initiation systems, which make it possible to polymerize methyl methacrylate at a high rate, to reduce the molecular mass of polymers, and to synthesize polymers with a high content of syndiotactic triads, while in the case of AIBN, such systems are not formed.     

In situ monitoring of free-radical polymerization by fluorescence quenching of fluorene and reactive derivatives

A new approach for monitoring in situ the progress of an addition polymerization has been developed based on the fluorescence quenching of fluorene. Fluorene is quenched by the enone functionality on acrylates and methacrylates, but is not quenched after the carbon-carbon double bond in this group is broken by incorporation into the polymer backbone. Ethyl (2-fluorenyl)methacrylate was used as a self-quenching comonomer during the 2,2'-pazo bis(2-methylpropionitrile)-initiated free-radical copolymerization of methyl methacrylate at 60°C. The fluorescence intensity increases by 60% up to the onset of the gel effect (defined as the sudden increase in the temperature profile). The system shows sensitivity well into the glassy state, with fluorescence increasing more than two orders of magnitude from the beginning of the reaction. This sensitivity is compared with that of two free-volume-dependent probes, 1,3-bis(1-pyrene)propane and dimethylaminobenzylidenemalononitrile, and to fluorene. The temperature profile of the test-tube-scale reaction was used as an internal reference for characterizing the sensitivity of the probes with respect to the gel effect region. © 1994 John Wiley & Sons, Inc.     

Structure of ionic liquid-benzene mixtures

Neutron diffraction has been used to investigate the structure of liquid mixtures of 1,3-dimethylimidazolium hexafluorophosphate with benzene. Two concentrations of benzene were investigated, namely, 33 mol % and 67 mol %, and show similar structures in each case. The presence of benzene significantly alters the ionic liquid structure, in particular, in the cation-cation interactions, in agreement with the single-crystal structure described recently (Holbrey, J. D.; Reichert, W. M.; Nieuwenhuyzen, M.; Sheppard, O.; Hardacre, C.; Rogers, R. D. Chem. Commun. 2003, 476). In each case, the data was analyzed using an empirical potential structure refinement process.     

Facile synthesis of thiourea derivatives in ionic liquid

The synthesis of cinnamoyl thiourea derivatives from cinnamoyl isothiocyanate (CIT) with substituted aniline (RC6H4NH2) was investigated in the mostly used ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate, [Bmim][BF4]. Significant enhance-ments in reactivity, yield and reaction rate were achieved. The products could be recovered by simple filtration. [Bmim][BF4] couldbe recycled simply by removing water under vacuum and reused at least 9 times without significant decrease in activity.     

Structure of alkali metal ionic clusters

Quantum mechanical calculations show that alkali metal ionic clusters of the type M³⁺₄ have the tetrahedral structure, the stability varying as Na³⁺₄ > K³⁺₄ > Rb³⁺₄. Raman spectroscopy has been employed to establish the tetrahedral structure of Na³⁺₄.     

Effect of histidine-containing dipeptides on the free-radical fragmentation of biologically active phospho derivatives of glycerol

The effects of carnosine, anserine, and glycyl-histidine on the free-radical fragmentation of glycero-1-phosphate and dimiristoyl phosphatidylglycerol induced by γ-radiation or Fe²⁺(Cu²⁺)-containing systems have been studied. The histidine-containing dipeptides (HCDs) exert a radioprotector effect on the fragmentation; this effect depends on the concentration of O₂ and reaches a maximum in deaerated systems (by a factor of ~1.7). The HCDs can be antior prooxidants under the conditions of the Fe²⁺(Cu²⁺)-mediated generation of HO· radicals. Carnosine exhibits protector properties in a dose-dependent manner regardless of the inductor. Carnosine more effectively inhibits Cu²⁺-induced fragmentation (by a factor of 2–2.5) than the Fe²⁺-mediated process (by a factor of 1.4).     

A nucleophilic reaction of a phosphaalkene: the methylation of mesityldiphenylmethylenephosphine

The reaction of the title compound ($\underset{?}{1}$) with methyl iodine gives the ylide $\underset{?}{3}$ and the phosphonium salt $\underset{?}{4}$. The intermediate formation of the phosphoniaalkene $\underset{?}{2}$ is postulated.     

Redox-active iron-containing polymers: synthesis and anionic polymerization of a C-ferrocenyl-substituted phosphaalkene

The addition polymerization of a ferrocenyl-substituted P[double bond]C bond leads to new redox-active polymers with functional ferrocene and phosphine moieties.     

Polyrotaxane derivatives. II. Preparation and characterization of ionic polyrotaxanes and ionic slide‐ring gels

Four types of ionic polyrotaxane (PR) derivatives, that is, carboxymethylated, sulfoethylated, diethylaminoethylated, and trimethylammoniohydroxypropylated PRs, were successfully prepared starting from the same PR consisting of poly(ethylene glycol) as an axis and α‐cyclodextrins as ring molecules. The structures of the ionic PR derivatives were analyzed by ¹H and ¹³C nuclear magnetic resonance (NMR), attenuated‐total reflection Fourier transform‐infrared, and colloidal titration. Degrees of substitution of the ionic PRs were calculated from results of ¹H NMR and colloidal titrations; both sets of results satisfactorily agreed. Cross‐linking of sulfoethylated and quaternized PRs yielded ionic slide‐ring gels carrying sulfoethyl and quaternary ammonium groups on the mobile cross‐links, respectively. The former gel showed intriguing phenomena, including a large degree of swelling of up to 1147, drastic change in its swelling ratio by the presence of electrolyte and bending under a moderate applied electric field (7 V/cm). © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

碱性离子液体催化合成取代萘并吡喃衍生物

离子液体具有强极性、不挥发、化学稳定性好等特点,其极性和亲水/亲脂性可通过改变烷基碳链的长短和阴、阳离子的种类来进行调节,对其结构进行化学修饰,可以得到具有特定功能的离子液体[1-3],因此被誉为绿色溶剂和可设计的溶剂[2]。许多萘并吡喃衍生物都具有重要的生物活性和药     

Inhibiting effect of 5-amino-5-methyluracil and its derivatives on the free-radical oxidation of 1,4-dioxane

The antiradical activity of 5-amino-6-methyluracil in the initiated radical-chain oxidation of 1,4-dioxane as a model system was studied quantitatively. The rate constant k ₇ of its reaction with the peroxyl radical of 1,4-dioxane was measured to be (5.6 ± 1.8) × 10⁵ L mol^?1 s^?1 at 333 K. The effect of the methyl substituents in the 1- and 3-positions of the uracil ring and in the amino group on the rate constant of inhibition was studied. The strengths of all N-H bonds in the 5-amino-6-methyluracil and its derivatives were calculated in the G3MP2B3 approximation and were compared with the measured rate constants of inhibition. By the example of the reaction of 5-amino-6-uracil with i-PrO ₂ ^?? , different attack pathways of the peroxyl radical at the N-H bonds of uracil were analyzed in the UB3LYP/6-311+G(d,p) approximation. The lowest activation barrier (5.8 kJ/mol) was observed for peroxyl radical attack on the (C⁵)N-H bonds. The site responsible for the inhibition activity of the compound is the amino group.     

Effect of sulfur-containing amino acids and peptides on the free-radical fragmentation of biologically active phospho derivatives of glycerol

The effects of sulfur-containing amino acids and peptides (cysteine, N-acetylcysteine (NAC), methionine, methionine sulfoxide (MetO), taurine (Tau), glutathione (GSH, GSSH), cysteinylglycine, and glutamylcysteine) on the free-radical degradation of glycero-1-phosphate and dimiristoyl phosphatidylglycerol with phosphoether bond rupture induced by γ-radiation or the Fe²⁺(EDTA)(Cu²⁺)–H₂O₂–(ascorbate) systems have been studied. In the case of a radiation-initiated process, thiols exert the greatest radioprotective effect in a concentration-dependent manner, and the action of MetO and Tau is neutral. In the case of Cu²⁺- mediated fragmentation, all of the test compounds with exception of Tau and NAC inhibit the process. The action of the test compounds on the fragmentation mediated by the Fe²⁺/EDTA–H₂O₂ (Fe²⁺–H₂O₂–ascorbate) systems can be either anti(pro)oxidant or neutral. In this case, all of the thiols other than glutamylcysteine exert an activating effect.