Abstract  Fluorine smoothly attacks quinuclidine-trifluoroborane, quinuclidine-pentafluorophosphorane, and quinuclidine-sulfur trioxide in acetonitrile at -35 degrees C to give the corresponding N-fluoroquinuclidinium salts NFQ(+)X(-) (X(-)=BF4-, PF6-, and FSO3- respectively; Q = quinuclidine). Like its tetrafluoroborate analogue (NFQ(+)BF(4)(-)), the hexafluorophosphate NFQ(+)PF(6)(-) can also be prepared by direct fluorination of quinuclidine in the presence of the appropriate sodium salt (NaPF6). An alternative route to the tetrafluoroborate involves treatment of NFQ(+)F(-) with boron trifluoride. A comparative study of site-specific electrophilic fluorination of methoxybenzene [--> 1-fluoro-2- and 4-methoxybenzene], 2-hydroxynaphthalene (--> 1-fluoro-2-hydroxynaphthalene and 1,1-difluoro-2-oxo-1,2-dihydronaphthalene),2-nitropropan-2-yl-lithium (--> 2-fluoro-2-nitropropane) and diethyl sodio(phenyl) malonate [--> diethyl fluoro(phenyl) malonate] with all of the NFQ(+) X(-) salts mentioned above, plus the triflate (X(-) = CF3SO3-), revealed that the hexafluorophosphate and triflate are the most easily-handled and effective reagents.

Abstract  The complexing properties of four dimalonate and one diester calix[4]arene derivatives toward alkali and alkaline earth cations have been investigated in acetonitrile by means of UV spectrophotometry. Mononuclear complexes have been detected for all the complexes except in the case of ligands 4 and 5 with Na+ and Ca2+ where a biligand species (ML2) is present. This later stoichiometry was also confirmed by H-1-NMR and FAB(+) MS methods. In the case of ligand 3 and Sr2+ we observed the formation of both mono and binuclear species (ML, (ML)-L-2). Particular selectivities have to be noted from the unique complexation of Na+ and Ba2+ by ligand 2 and Rb+ by ligand 3 toward the two series of cations. The complexation is predominantly dependent on the bulkiness of the cavity and the cation size.

Abstract  The paper considers the possibility of increasing the sensitivity of semiconductor adsorption sensors using photon laser stimulation of low power. The results of experiments on the detection of vapors of malonic ester to semiconductor sensors manufactured on the basis of tin dioxide with various doping impurities with the use of laser irradiation and without it. The mechanism of photon stimulation was proposed and its effect was examined on the kinetics of adsorption and an increase the indicator effect.

Abstract  The bubble points for (triethyl orthoformate + diethyl malonate) at T = (373.15, 383.15, and 393.15) K and at p = 13.33 kPa, measured with an inclined ebulliometer are presented. The experimental results are analyzed using the UNIQUAC equation with the temperature-dependent binary parameters with satisfactory results. Experimental vapour pressures of triethyl orthoformate are also included. (C) 2004 Elsevier Ltd. All rights reserved.

Abstract  Novel P*-chiral P,N-bidentate ligands were synthesized by treatment of ferrocene-based imino alcohols with chlorophosphites derived from (S)-2-anilinomethylpyrrolidine or (S)-prolinol. Metal chelate complexes with the ligands [Rh(CO)(PN)Cl] and [Pd(PN)(allyl)]X-+(-) (X- = BF4-, Cl-, I-, CH12B11-) - were obtained and all new compounds were fully characterized by H-1, C-13, P-31 NMR, IR, MS (El, Cl, FAB, ESI and plasma desorption techniques) and X-ray analysis (imino alcohol 2d and complex 7). P*-Chiral diamidophosphites gave up to 97 % ee in the Pd-catalysed allylic substitution of 1,3-diphenylallyl acetate with dimethyl malonate and paratoluenesulfinate. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Abstract  Ring-opening of N-(PhF)serine-derived cyclic sulfamidate 17 was achieved with different nucleophiles (beta -keto esters, beta-keto ketones, dimethyl malonate, nitroethane, sodium azide, imidazole, and potassium thiocyanate) to prepare a variety of amino acid analogs. Two different pathways for ring opening of 17 were elucidated: direct nucleophilic displacement, as well as beta -elimination followed by Michael addition. Furthermore, beta -keto ester and beta -keto ketone products 18k,18m, and 18i were converted to prolines and pyrazole amino acids.

Abstract  Rhodium complexes, in the presence or absence of PEt3, catalyse the carbonylation of CH2I2 to dialkylmalonates in the presence of alcohols (ROH, R = Me, Et, Pr-i, Bu) with side products from reactions in EtOH being CH2(OEt)(2), EtI and traces of EtCO2Et and EtOAc. The active species when using PEt3 is shown to be [RhI(CO)(PEt3)(2)], formed via [Rh(OAc)(CO)(PEt3)(2)] from [Rh-2(OAc)(4). 2MeOH] and PEt3. Mechanistic studies show that the first step of the catalytic cycle is oxidative addition of CH2I2 to give [Rh(CH2I)I-2(CO)(PEt3)(2)], but that insertion of CO into the Rh-CH2I bond gives an iodoacyl complex which is unstable. The analogous [Rh(COCH2X)X-2(CO)(PEt3)(2)], (X = Cl or Br) have been synthesised by oxidative addition of XCH2COX to [RhX(CO)(PEt3)(2)] and fully characterised (by X-ray crystallography, for X = Cl). [Rh(COCH2Br)Br-2(CO)(PEt3)(2)] has also been formed from reaction of [Rh(COCH2Cl)Cl-2(CO)(PEt3)(2)] with excess NaBr. However, the analogous reaction with NaI does not give the iodoethanoyl complex, but rather [RhI3(CO)(PEt3)(2)] and its decomposition products. It is proposed that [Rh(COCH2I)I-2(CO)(PEt3)(2)] is unstable towards loss of I- to form the ketene complex, [RhI2(CH2 = C = O)(CO)(PEt3)(2)]I, which is transformed into [Rh(COCH2CO2Et)I-2(CO)(PEt3)] by nucleophilic attack of ethanol at the central C atom, followed by CO insertion into the Rh-C bond. An analogue, [Rh(COCH2CO2Et)Cl-2(CO)(PEt3)(2)], has been isolated by oxidative addition of EtO2CCH2COCl across [RhCl(CO)(PEt3)(2)], and characterised both spectroscopically and crystallographically. In refluxing ethanol, [Rh(COCH2CO2Et)Cl-2(CO)(PEt3)(2)] produces diethylmalonate and [RhCl(CO)(PEt3)(2)], thus completing the catalytic cycle. Possible pathways of deactivation of the catalyst to give [RhI3(CO)(PEt3)(2)] are discussed. One involves the reaction of ketene with ethanol to give EtOAc, whilst the others involve protonation of the Rh-Z bond in [RhZI(2)(CO)(PEt3)(2)] (where Z = CH2I, CH2CO2Et or H) by HI. The isolation of CH2DCO2Et, when carrying out the reaction in EtOD, is consistent with all of these deactivation pathways except protonation of [RhHI2(CO)(PEt3)(2)]. (C) 1998 Elsevier Science S.A. All rights reserved.

Abstract  The kinetics of oxidation of esters by chromic acid has been investigated in acetic acid-water mixtures in the presence and absence of oxalic acid. In the absence of oxalic acid, the reaction is overall second order, first order in each reactant. The reaction rates are independent of the added salts, while in the presence of oxalic acid the rate of oxidation increases. The products are identified and activation parameters have been calculated.

Abstract  Bromomethyl cyclopent-1-enyl sulfone and bromomethyl cyclohex-1-enyl sulfone reacted with dimethyl malonate and malononitrile sodium salts in THF at 20-50A degrees C to give products of Michael-induced Ramberg-Backlund reaction, functionalized derivatives of methylidenecyclopentane and methylidenecyclohexane. Reactions of bromomethyl hex-1-en-1-yl sulfone and bromomethyl hept-1-en-1-yl sulfones with the same sodium enolates followed the Michael-induced ring closure pattern with formation of tetrahydrothiophene 1,1-dioxide derivatives containing allylmalonic acid derivatives as impurities. Factors responsible for the different reaction pathways of cyclic and acyclic bromomethyl sulfones are discussed.

Abstract  P*-Chiral diamidophosphite ligand-assisted Pd-catalyzed Tsuji-Trost reaction between dimethyl malonate and prochiral 3-acetoxy-1,3-diphenylpropene in organic solvents using potassium carbonate as the base affords the substitution product in quantitative yields and with enantioselectivities up to 99% ee.

Abstract  Palladium-catalyzed potassium carbonate-assisted reaction between diethyl malonate and allyl acetate in the presence of 1,3-dialkylimidazolium ionic liquids (ILs) as solvents or phase transfer catalysts affords major monoallylation product, whereas in the presence of 1,2,3-trialkylimidazolium or quaternary ammonium/phosphonium ILs diallylation product is preferably formed. These procedures are extended to some other CH-acids and allylic acetates.

Abstract  Coating sol solutions were prepared from anhydrous ethanol solutions of Ta(OC2H5)5. With the addition of high-purity acetic acid, Ta(OC2H5)5 was partially hydrolyzed by trace amounts of water in the acetic acid used and further condensation took place. Among the sol solutions obtained, the solution (A) containing 1.2 mol% Ta(OC2H5)5 together with acetic acid at its molar ratio of 1.5 to Ta(OC2H5), was transparent and stable on storage for two months. When chelating agents (diethyl malonate, acetylacetone, ethyl acetoacetate and ethyl acetate) were added to one of the starting solutions, the agents (especially diethyl malonate) were found to remain in gels when the solution was dried at room temperature. Among these gels, one containing acetylacetone crystallized at the highest temperature of about 830-degrees-C on heating.

Ta2O5 gel thin films were prepared from the solution (A) by the drop-coating method, the solution was dropped on a substrate to spread over and evaporate. Preparation under dry nitrogen (approximately 0% relative humidity) gave a transparent gel film at room temperature. DTA analysis revealed that, on heating in air, the gel film crystallized around 840-degrees-C which was higher by about 100-degrees-C than the crystallization temperatures of the other gels prepared under high relative humidities. On heating under nitrogen atmosphere, the exothermic peak of crystallization at 840-degrees-C decreased extremely to be replaced by a weak exothermic peak (appearing) at 1000-degrees-C. Preparation test under different relative humidities and substrate temperatares showed that transparent gel films were obtained regardless of substrate temperatures under low relative humidities, while only at somewhat elevated substrate temperatures under high humidities.

Abstract  The coordination of transition metals to organic fragments can yield complexes with fascinating and unexpected binding patterns. The study of metal-benzyl complexes has demonstrated the feasibility of η(3)-coordination, which results in a dearomatized ring. These complexes also offer insight into reaction mechanisms as proposed intermediates in catalytic cycles. In this Review we discuss the synthesis and characterization of these complexes with late transition metals and the subsequent development of catalytic benzylic functionalization methods, including asymmetric variants.

Abstract  alpha,beta-Unsaturated acetylenic -hydroxyketones have been shown to react with ethyl acetoacetate in a Michael-addition fashion and subsequently undergo cyclization followed by dehydration to give substituted furans with a predictable regiospecificity. The yields were good to excellent. A mechanism for the transformation is proposed, and this mechanism explains why furan formation does not take place when the same unsaturated ketones are treated with -methylated acetoacetate and diethyl malonate. [Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications (R) for the following free supplemental resource: Full experimental and spectral details.]

Abstract  The rhenium hydroxy and methoxy carbonyl complexes [Re-2(mu-OR)(3)(CO)(6)](-) (R=H or Me) have been studied by negative-ion electrospray mass spectrometry (ESMS). The complexes undergo facile exchange reactions with protic compounds, including alcohols and phenols. With dimethyl malonate, ester hydrolysis occurs giving carboxylate-containing complexes, and with H2O2 or (BuOOH)-O-t, oxidation to ReO4- occurs. The feasibility and extent of these reactions can conveniently, rapidly, and unambiguously be determined by electrospray mass spectrometry, and is dependent on the acidity and steric bulk of the protic compound. The results also suggest that the complexes can be used as versatile starting materials for the synthesis of a wide range of analogous [Re-2(mu-OR)(3)(CO)(6)](-) complexes by simple reaction with an excess of the appropriate alcohol. By varying the applied cone voltage the fragmentation pathways have been investigated; the hydroxy complex undergoes dehydration followed by CO loss, whereas for the methoxy complex beta-hydride elimination (and CO loss) is observed, with confirmation provided by deuterium labelling studies. Under ESMS conditions, the neutral complexes [Re-2(mu-OR)(2)(mu-dppf)(CO)(6)] [R=H or Me; dppf=1,1'-bis(diphenylphosphino)ferrocene] undergo substantial solvolysis and hydrolysis to give mainly mononuclear species; simple parent ions (e.g. [M+H](+)) are not formed in appreciable abundance, probably due to the lack of an efficient ionisation pathway.

Abstract  Novel liquid crystalline malonic ester monomer was synthesized from malonyl dichloride and disperse red 1, a photoresponsive group. The monomer was polymerized with 1,6-dibromohexane, 1,8-dibromooctane, 1,10-dibromo-decane, 1,12-dibromododecane, alpha,alpha'-dibromo-p-xylene, alpha,alpha'-dibromo-m-xylene, or alpha,alpha'-dibromo-o-xylene in the presence of sodium hydride to give seven kinds of novel poly(malonic esters) with two symmetrical photoresponsive groups in the side chain. The resulting polymer films were found to be excellent as reversible optical information recording media for data storage and retrieval through a trans-cis isomerization of azobenzene group by Ar laser irradiation. The sensitivity of data recording was dependent not only on the thickness of the polymeric thin film but also on the intensity of laser beam. (C) 2002 Elsevier Science B.V. All rights reserved.

Abstract  We report an efficient process for the synthesis of diethyl malonate (DEM) and other malonates through the palladium-catalyzed carbonylation of chloroacetates. Excellent selectivity (96?%) and yield (94?%) were obtained without the formation of Pd black. For the first time, a weakly alkaline buffer was used to control the selectivity for DEM in the reaction and we discuss the relationship between the buffer medium and selectivity in the reaction. The combination of anisole as the solvent and a Na2HPO4/NaH2PO4 buffer was beneficial for completely restraining the phase-transfer-catalyzed substitution of DEM with ethyl chloroacetate, as well as accommodating the proposed [(PPh3)2PdI]-[Bu4N]+ intermediate, by providing a suitable environment for its stable existence. We achieved the highest efficiency in the catalytic cycle by fine-tuning the balance between the rates of oxidative addition and reductive elimination; moreover, we synthesized a recoverable heterogeneous polymer-bound Pd catalyst in 85?% yield that could be reused without an appreciable loss in activity over four cycles.

Abstract  New poly(malonic ester) with two symmetrical azobenzene groups was synthesized by the reaction of novel liquid crystalline malonic ester monomer with disperse red 1 with 1,6-dibromohexane. The resulting polymer was found to be excellent as reversible optical information recording media for data storage and retrieval through st trans-cia isomerization of the azobenzene units by Ar laser irradiation and thermal process.

Abstract  The problems of liquid-liquid extraction and solids dissolution in stirred tanks are classic mass transfer problems which have been studied extensively in the literature. An analogous problem, that of dissolution of pure drops close to their solubility limit, has been almost completely neglected. This problem has practical application in the dissolution and dispersion of small amounts of surface active additives, particularly in the water treatment industry and in oil field applications where the cost of the chemical additive is one of the major process costs. The question is also of interest for some chemical reactions, such as the third Bourne reaction (diethylmalonate in water) and the hydrolysis of acetic anhydride to acetic acid. In this paper, the drop size distribution and solute concentration in the bulk are measured throughout the dissolution period and the dissolution process is successfully modelled using an Eulerian-Lagrangian approach. The validated model is used to identify the key variables driving the dissolution rate. The approach to saturation, the impeller rotational speed, and the continuous phase viscosity all play an important role. When the solute is injected close to the impeller, the role played by surface tension is surprisingly small.

Abstract  Cerium(IV) ammonium nitrate (CAN) has recently emerged as a versatile reagent for oxidative electron transfer; the overwhelming number of reports serve as a testimony to the unparalleled utility of CAN in a variety of transformations of synthetic importance. Our recent work has uncovered novel carbon-carbon bond-forming reactions leading to the one-pot synthesis of dihydrofurans, tetrahydrofurans, and aminotetralins. In addition, we have developed a number of facile carbon-heteroatom bond-forming reactions by the CAN-mediated oxidative addition of soft anions to alkenes. A mechanistic rationale has been provided for the reactions explored. As might be expected of very powerful one-electron oxidants, the chemistry of cerium(IV) oxidation of organic molecules is dominated by radical and radical cation chemistry.

Abstract  A straightforward synthetic pathway allowing the access to anti or syn 2-amino-1,3-diol scaffolds is presented. The strategy relies on a diastereoselective organocatalyzed decarboxylative aldol reaction of a N-Boc-hemimalonate that is easily formed from commercial N-Boc-diethyl malonate. Although this method has been optimized previously with the N-Bz-hemimalonate analogue, this key step was reinvestigated with the N-Boc derivative to improve the required reaction time, the yield, and the diastereoselectivity. The new conditions enhance this transformation, and quantitative yields and anti/syn ratios up to 96:4 can be obtained. The anti aldol product was easily isolated in pure form and then taken forward as the key precursor in the preparation of both a set of ten N-/O-alkylated anti 2-amino-1,3-diol derivatives and the syn congeners.

Abstract  Incidents involving the release of chemical agents can pose significant risks to public health. In such an event, emergency decontamination of affected casualties may need to be undertaken to reduce injury and possible loss of life. To ensure these methods are effective, human volunteer trials (HVTs) of decontamination protocols, using simulant contaminants, have been conducted. Simulants must be used to mimic the physicochemical properties of more harmful chemicals, while remaining non-toxic at the dose applied. This review focuses on studies that employed chemical warfare agent simulants in decontamination contexts, to identify those simulants most suitable for use in HVTs of emergency decontamination. Twenty-two simulants were identified, of which 17 were determined unsuitable for use in HVTs. The remaining simulants (n = 5) were further scrutinized for potential suitability according to toxicity, physicochemical properties and similarities to their equivalent toxic counterparts. Three suitable simulants, for use in HVTs were identified; methyl salicylate (simulant for sulphur mustard), diethyl malonate (simulant for soman) and malathion (simulant for VX or toxic industrial chemicals). All have been safely used in previous HVTs, and have a range of physicochemical properties that would allow useful inference to more toxic chemicals when employed in future studies of emergency decontamination systems.

Abstract  Fragmental topology-activity landscapes (FRAGTAL), a new concept for encoding molecular descriptors for fragonomics into the framework of the molecular database records is presented in this paper. Thus, a structural repository containing biological activity data was searched in a substructure mode by a series of molecular fragments constructed in an incremental or decremental manner. The resulted series of database hits annotated with their activities construct FRAGTAL descriptors encoding a frequency of the certain fragments among active compounds and/or their activities. Actually, this method might be interpreted as a simplified adaptation of the frequent subgraph mining (FSM) method. The FRAGTAL method reconstructs the way in which medicinal chemists are used to designing a prospective drug structure intuitively. A representative example of the practical application of FRAGTAL within the ChemDB Anti-HIV/OI/TB database for disclosing new fragments for HIV-1 integrase inhibition is discussed. In particular, FRAGTAL method identifies ethyl malonate amide (EMA) as the diketo acid (DKA) related arrangement. Since new molecular constructs based on the EMA fragment are still a matter of future investigations we referred to this as anthe DKA offspring.

Abstract  Active methylene compounds such as acetone, butanone, cyclopentanone, nitromethane, malononitrile, ethyl 2-cyanoacetate, diethyl malonate, and ethyl acetylacetate react with the C3 position of N-confused porphyrin in the presence of L-proline in refluxing THF-EtOH affording a variety of N-confused porphyrin derivatives in moderate yield. L-Proline catalyzes the reaction facilitating the formation of the carbanion derived from an active methylene compound simultaneously delivering protons to the N-confused porphyrin. Both processes are key factors of this reaction.

Abstract  The mechanism of Michael addition reactions of 1,3-dicarbonyl compounds to cyclic enones catalyzed by bifunctional Ru catalysts bearing N-sulfonylated (R,R)-DPEN ligands (DPEN = (R,R)-1,2-diphenylethylenediamine) was studied by NMR and DFT computational analyses. NMR investigation of the stoichiometric reactions of chiral amido Ru complexes, Ru(N-sulfonylated dpen)(η(6)-arene) 1a-c, with dimethyl malonate 2 and β-keto ester 3 revealed that at decreased temperatures deprotonation proceeds in a stereoselective manner to provide amine complexes. The reaction with malonic ester 2 provided exclusively C-bound amino Ru complexes 6a,c, while the reaction of β-keto ester 3 gave an equilibrium mixture of rapidly interconverting C- and O-bound complexes. The structures of C-bound Ru complex 6c and O-bound Ru complex 9c were determined by single crystal X-ray analysis. A computational study showed that the enatioselective C-C bond formation proceeds through intermediate formation of chelating ion pairs that coordinate a molecule of enone via the Ru metal center producing a highly organized environment for the C-C bond formation, yielding selectively only one enantiomer of the product. Systematic study of a series of the catalyst-substrate combinations revealed that the experimentally observed sense of enantioselection was consistently explained by computational analysis. The tendency of increasing ee with the bulk of the coordinated arene in Ru complex is reproduced computationally by changes in the difference of either ZPPE-corrected energies or Gibbs free energies for S- and R-pathways.