Abstract  Threefold symmetrical chiral podands may simplify the stereochemistry of key catalytic intermediates for cases in which they only act as bidentate ligands. This applies to systems in which chemical exchange between the different kappa2-coordinated forms takes place and in which the non-coordinated sidearm may play a direct or indirect role at some earlier or later stage in the catalytic cycle. Palladium(II)-catalysed allylic substitutions provide appropriate test reactions along these lines. A series of neutral dichloropalladium(II) complexes, [PdCl2(iPr-trisox)] (1a), [PdCl2(Ph-trisox)] (1b), [PdCl2(Bn-trisox)] (1c) and [PdCl2(Ind-trisox)] (1d) (trisox=1,1,1-tris(oxazolinyl)ethane) were synthesised by reaction of the respective trisox derivative with [PdCl2(PhCN)2] and characterised inter alia by 15N NMR spectroscopy. Direct detection of the heteronuclei without isotope enrichment and with "normal" sample concentrations was achieved with the aid of a cryogenically cooled NMR probe on a 600 MHz NMR spectrometer. Whereas the 15N nuclei of the coordinated oxazoline rings resonate at delta=160-167 ppm and appear as two singlets due to their diastereotopicity, the signal assigned to the dangling oxazoline "arm" is observed at delta=238-240 ppm. Variable-temperature NMR studies along with a systematic series of magnetisation transfer experiments established exchange between ligating and non-ligating oxazoline rings. Reaction of [Pd(allyl)(cod)]BF4 (cod=cyclooctadiene) with Ph-trisox in CH(2)Cl(2) gave the corresponding allyl complex 2, for which fast exchange between the three oxazoline heterocycles as well as between the exo and endo diastereomers was observed along with a very slow eta3-eta1-eta3 process of the allyl fragment (magnetisation transfer). Palladium(0) complexes were prepared by reaction of trisox derivatives or sidearm-functionalised BOX (BOX=bis(oxazolinyl)dimethylmethane) ligands with [Pd(nbd)(alkene)] (nbd=norbornadiene, alkene=maleic anhydride or tetracyanoethylene). X-ray diffraction studies of the iPr-trisox and Ph-trisox complexes (3a and 3b) established Y-shaped trigonal planar coordination geometries with the trisox ligand coordinated in a bidentate fashion, whilst the pi-coordinated maleic anhydride ligand adopts one of the two possible diastereotopic orientations. As the catalytic test reaction, the allylic alkylation of 1,3-diphenylprop-2-enyl acetate substrate with dimethyl malonate as nucleophile (in the presence of N,O-bis(trimethylsilyl)acetamide) was investigated for the trisox derivatives, their BOX analogues, and a series of less symmetric "sidearm" functionalised bisoxazolines. The trisoxazoline-based catalysts generally induce a better enantioselectivity compared to their bisoxazoline analogues and display significant reduction of the induction period as well as rate enhancement.

Abstract  A butenolide-containing sugar available from the aldol condensation of methyl 4,6-O-benzylidene-alpha-D-glucopyranosid-2-ulose with diethyl malonate is autoxidized at the C-3 position into the corresponding alpha,beta-unsaturated gamma-lactone sugar by air, which subsequently undergoes 1,4-conjugate (Michael) addition of hydroxide ion (or water) leading to a C-branched-chain glucopyranosidulose. The autoxidations are also performed in weakly basic, neutral and weakly acidic medium, respectively.

Abstract  Solvent-free reactions of C(60) with active methylene compounds, either with or without carbon tetrabromide (CBr(4)), in the presence of a base under high-speed vibration milling (HSVM) conditions were investigated. The reaction of C(60) with diethyl bromomalonate was conducted under HSVM conditions in the presence of piperidine, triethylamine or Na(2)CO(3) to afford cyclopropane derivative. In the presence of CBr(4), methanofullerenes, and could be obtained by the direct reaction of C(60) with diethyl malonate, dimethyl malonate, ethyl acetoacetate and ethyl cyanoacetate, respectively, with the aid of 1,8-diazabicyclo[5,4,0]undec-7-ene, piperidine, triethylamine or Na(2)CO(3). More interestingly, 1,4-bisadducts and were produced by the reaction of C(60) with diethyl malonate and dimethyl malonate in the presence of piperidine, triethylamine or Na(2)CO(3) under HSVM conditions. On the other hand, dihydrofuran-fused C(60) derivatives, and were obtained from the reaction of C(60) with ethyl acetoacetate, 2,4-pentanedione and 5,5-dimethyl-1,3-cyclohexanedione with the aid of a base. Under the same conditions, less activated aryl methyl ketones such as 2-acetylpyridine, 2-acetylpyrazine and acetophenone provided monocarbonylated methanofullerene derivatives, and. Except for the Bingel reactions, all other reactions under the HSVM conditions are considered to proceed according to a single-electron-transfer mechanism.

Abstract  Treatment of 5,10,15,20-tetraarylporphyrins (1) with perfluoroalkyl iodides (2) in the presence of Na(2)S(2)O(4)/NaHCO(3) in DMSO-CH(2)Cl(2) at 30-40 degrees C for several hours gives the corresponding 2-perfluoroalkylporphyrins (3). Nucleophilic attack on 3 with dimethyl malonate, diethyl malonate, malonitrile, or cyano acetate (Nu) anion results in the formation of (E)-3-Nu-2-perfuoroalkyl(methylenyl)chlorins. Electrophilic substitution on 3 with NBS or NO(2) affords regioselectively the corresponding 12(or 13)-bromo- and 12,13-dibromo- or nitroporphyrins.

Abstract  2,5-Cyclohexadienyl-substituted aryl or vinylic iodides have been reacted with carbon nucleophiles (diethyl malonate and 2-methyl-1,3-cyclohexanedione), nitrogen nucleophiles (morpholine, potassium phthalimide, N-benzyl tosylamide, di-tert-butyl iminodicarboxylate, lithium azide, and anilines), a sulfur nucleophile (sodium benzenesulfinate), and oxygen nucleophiles (lithium acetate and phenols) to afford products of cyclization and subsequent cross-coupling in good to excellent yields. In most cases, this process is highly diastereoselective. The reaction is believed to proceed via (1) oxidative addition of the aryl or vinylic iodide to Pd(0), (2) organopalladium addition to one of the carbon-carbon double bonds, (3) palladium migration along the carbon chain on the same face of the ring to form a pi-allylpalladium intermediate, and (4) nucleophilic displacement of the palladium.

Abstract  Azorhizobium caulinodans mutant 62004 carries a null allele of pdhB, encoding the E1beta subunit of pyruvate dehydrogenase, which converts pyruvate to acetyl-CoA. This pdhB mutant completely lacks pyruvate oxidation activities yet grows aerobically on C(4) dicarboxylates (succinate, L-malate) as sole energy source, albeit slowly, and displays pleiotropic growth defects consistent with physiological acetyl-CoA limitation. Temperature-sensitive (ts), conditional-lethal derivatives of the pdhB mutant lack (methyl)malonate semialdehyde dehydrogenase activity, which thus also allows L-malate conversion to acetyl-CoA. The pdhB mutant remains able to fix N(2) in aerobic culture, but is unable to fix N(2) in symbiosis with host Sesbania rostrata plants and cannot grow microaerobically. In culture, A. caulinodans wild-type can use acetate, beta-D-hydroxybutyrate and nicotinate--all direct precursors of acetyl-CoA--as sole C and energy source for aerobic, but not microaerobic growth. Paradoxically, acetyl-CoA is thus a required intermediate for microaerobic oxidative energy transduction while not itself oxidized. Accordingly, A. caulinodans energy transduction under aerobic and microaerobic conditions is qualitatively different.

Abstract  Carnitine palmitoyltransferases 1 and 2 (CPT-1 and CPT-2) catalyze the transfer of long chain fatty acids between carnitine and coenzyme A. Unlike CPT-2, CPT-1 exists in at least two isoforms with different physical and kinetic properties. Liver and skeletal muscle each contain a different isoform of CPT-1. Cardiac muscle contains both isoforms, and the minor component is identical to the isoform found in the liver. 2-[6-(2,4-Dinitrophenoxy)hexyl]oxiranecarboxylic acid (2) was reported to be a selective inhibitor for the liver isoform of CPT-1. A synthesis of 2 is described here which involves the reaction of diethyl malonate with 1-bromo-6-phenoxyhexane.

Abstract  Non-rhamnose-containing phosphoramidon analogues, in which the amide bond was replaced by the isosteric ketomethylene group, have been synthesized in order to stabilize these compounds to peptidase degradation. The key step in this synthesis was suitable alkylation of a 4-ketodiester, prepared from Z-Leu chloromethyl ketone and dimethyl malonate. The ketomethylene dipeptide derivatives P-Leu psi (COCH2)(RS)Xaa-OMe (Xaa = Trp, Phe) are good inhibitors of thermolysin, ACE and specially enkephalinase.

Abstract  A series of new steroid pyrimidines (7-9) were synthesized by reacting steroidal thiosemicarbazones (46) with diethyl malonate. The new compounds were characterized by IR, H-1 NMR, C-13 NMR, MS and analytical data. The interaction studies of compounds (7-9) with DNA were carried out by employing gel electrophoresis, UV-vis and fluorescence spectroscopy. The acting force between the compounds (7-9) and DNA was mainly hydrophobic while the other interactions like van der Waals, hydrogen bonding cannot be ruled out. The gel electrophoresis pattern also demonstrated that the compound 7 alone or in presence of Cu (II) causes the nicking of supercoiled pBR322 and it seems to follow the mechanistic pathway involving generation of hydroxyl radicals that are responsible for initiating DNA strand scission. The docking study of compounds (7-9) suggested that the intercalation of compounds in between the nucleotide base pairs might be due to the presence of pyrimidine moiety in steroid molecule. MTT assay was carried out to check the toxicity of new compounds (7-9) against the different human cancer as well as non-cancer cell lines A545, MCF-7, HeLa, HL-60, SW480, HepG2, HT-29, A549, 184B5, MCF10A, NL-20, HPC and HPLF. Apoptotic degradation of DNA in presence of steroidal pyrimidines (7-9) was analyzed by agarose gel electrophoresis and visualized by ethidium bromide staining (comet assay). (C) 2013 Elsevier B.V. All rights reserved.

Abstract  The article presents pioneering research of textile chemiresistors on Evolon and Polyester substrates equipped with graphite electrodes and in-situ polymerized poly(tetrabutylphosphonium 3-sulfopropylacrylate) or poly(tributylhexylphosphonium 3-sulfopropylacrylate) sensitive layers. The DC- and AC-responses to 10 ppm of methanol, nitrogen dioxide, 4-bromoacetophenone, diethylmalonate and yperite were then investigated at laboratory temperature - the reference was "pure" synthetic air. Under these circumstances the DC-responses (S-DC) varied from 0.48 to 1.36 and maximum AC-responses (S-pa) from 8 to 26 deg. It was shown that sensor dynamics depends mainly on molecular weight of the analytes. Moreover, the magnitude of AC-responses correlated both qualitatively and quantitatively with the dipole moments of the analyzed molecules. (C) 2018 Elsevier B.V. All rights reserved.

Abstract  The phase separation of isopycnic polystyrene-diethyl malonate solutions has been studied by investigating the microstructure of polymer membranes. Polymer solutions underwent spinodal decomposition and coarsening via a thermally induced phase separation-procedure, and supercritical CO2 extraction was employed to remove solvent, resulting in microporous membranes. At relatively short Coarsening times, the coarsening rate of the cell size can be expressed as a power law in time with the exponent increasing with increasing quench depth; for deep quenches, the growth rate has an exponent of 1/3 in agreement with the classic theories for coarsening by Ostwald ripening or coalescence. At longer coarsening times, there was a crossover to a much faster growth rate, yielding an exponent of 1.0 independent of phase separation temperature, consistent with expectations for the hydrodynamic flow mechanism of coarsening suggested by Siggia. This is the first experimental Confirmation of the evolution of the coarsening mechanism from one mechanism with a growth rate consistent with Ostwald ripening or coalescence to a second mechanism with a faster growth rate. Comparisons were also made to coarsening observed-in nonisopycnic/low-viscosity polystyrene-cyclohexane systems where strong gravitational effects dominate the phase separation process : at relatively short times and crossover effects cannot be observed.

Abstract  ''Metalloautism''-this term perfectly describes the characteristic of the adamantanoid iron(III) chelate complex 1 that the four iron centers do not interact with each other either electronically or magnetically. The four metal atoms are linked by six chelatino ligands (2), which are prepared by deprotonation of the product of the condensation of terephthaloyl chloride and dimethyl malonate.

Abstract  The synthesis and fluorescent properties of some new benzocoumaryl heterocyclic molecules are presented. Condensation of 2-hydroxy-1-naphthaldehyde with diethyl malonate in the presence of catalytic amount of piperidine in ethanol affords benzocoumarin-3-ethyl carboxylate 2 in fairly good yield (90%). Further the compound 2 on treatment with hydrazine hydrate afforded compound 3 with excellent yield ( 95%). Thus compounds 4a-e have been obtained by direct cyclization of 3 with various fatty acids in the presence of POCl(3). The structures of all newly synthesized compounds were confirmed by IR, (1)H NMR, (13)C NMR and UPLC-Mass spectral data. Fluorescent experimental results revealed remarkable photoluminescence properties. Luminescent properties of all newly synthesized compounds were determined and observed that they exhibited strong blue-green fluorescent properties. The fluorescence spectral properties of compounds 4a-e are similar to each other and the Stoke's shift ranges from 54 to 59 nm. Both the absorption and fluorescence maxima of the benzocoumarin-oxadiazole compounds showed good bathochromic shift.

Abstract  From reaction of bis(ethane-1,2-diamine)copper(II) with formaldehyde and diethyl malonate then formaldehyde and nitroethane in turn the pendant-arm macrocyclic complexion (hydrogen 13-methyl-13-nitro-1,4,8,11-tetraazacyclotetradecane-6-carboxylat e)copper(II) was prepared. Reduction with zinc in aqueous acid yields the free pendant-arm beta-polyamino acid macrocycle hydrogen 13-amino-13-methyl-1,4,8,11-tetraazacyclotetradecane-6-carboxylate (L3) as the hydrochloride salt. Co-ordination to cobalt(III) was achieved following reaction with cobalt(II) ion and air, yielding the chloro(hydrogen 13-amino-13-methyl-1,4,8,11-tetraazacyclotetradecane-6-carboxylat e)cobalt(III) ion, as well as its aqua analogue. The chlorocobalt(III) complex crystallized as the perchlorate salt in the space group Pbca, a = 10.256(4), b = 12.689(5), c = 3.08(2) angstrom, Z = 8, with the co-ordinated chloride in a cis disposition relative to the pendant amine, the four secondary amines co-ordinated in a folded geometry with uncommon RRRR stereochemistry, and the pendant carboxylic acid group not coordinated. Equilibration of the reaction mixture from this synthesis at pH 8 over activated carbon yielded almost exclusively the complex with the ligand bound as a sexidentate ligand where the pendant amine and carboxylate groups occupy trans sites. This complex crystallized as the perchlorate salt in the space group P2(1)/n with a = 10.939(2), b = 13,355(2), c = 14.596(2) angstrom, beta = 102.17(1)-degrees and Z = 4. Metal-donor distances [Co-O 1.899(2), Co N (pendant) 1.956(2), average Co-N (secondary) 1.95(1) angstrom] are at the short end of the range for saturated polydentate amino acid ligands, presumably influenced by the sterically efficient ligand.

Abstract  Endohedral N@C-60 (atomic nitrogen inside C-60) is produced by ion implantation. N@C-60 is soluble in organic solvents and stable in air. A special Feature is that it gives a very clear hyperfine split EPR signal with sharp lines even in the solid. This makes it an ideal probe for monitoring chemical reactions of C-60 via changes of the EPR signal. As an example, the formation of the monoadduct of diethyl malonate on C-60 will be discussed. In general, N@C-60 can be used as a probe or tracer for monitoring reactions or the transport of C-60. We show that C-60 is an ideal trap for atomic nitrogen. Nitrogen is in the center of C-60 and keeps its atomic structure. In a first experiment, the Vibrations of nitrogen in C-60 were studied. (C) 1998 Elsevier Science Ltd. All rights reserved.

Abstract  A combination of in situ one-dimensional H-1 magnetic resonance profiling and two-dimensional imaging has been applied to study the shape and subsequent dynamic evaporation behaviour of a single liquid droplet after impact onto a porous surface. Diethyl-malonate (DEM) droplets are initially embedded in the porous substrate by impingement, and are then evaporated over a period of several hours; the surface of the substrate being ventilated by a controlled airflow. The configuration is intended to mimic the behaviour of droplets evaporating into atmospheric flows. In order to evaluate the influence of the airflow at the surface of the porous medium, different experimental configurations were tested by varying the speed of the airflow stream above the porous surface. The method produces several types of data, including images of impinged droplets inside the porous substrate and their development with time during the evaporation episode, one-dimensional concentration profiles through the substrates, and corresponding estimates of the mass fraction of liquid remaining, evaporation rate and mass flux per unit area. The results obtained show that although liquid droplets tend to evaporate faster and present larger evaporation rates when exposed to a more efficient removal of vapour from the surface, the limiting effects of the porous medium are even more evident. (c) 2005 Elsevier Ltd. All rights reserved.

Abstract  The evaporation model of Roberts and Griffiths (1995 Atmospheric Environment 29, 1307-1317) has been subjected to an extensive validation exercise based on a major campaign of field experiments on evaporation from surfaces composed of sand and of concrete. This complements the previous validation which was limited to wind tunnel experiments on sand surfaces. Additionally, the validation using wind tunnel data has been extended to include concrete surfaces. The model describes the constant-rate and falling-rate periods that characterise evaporation from porous media. During the constant-rate period, the evaporation is solely determined by the vapour transport rate into the air. During the falling-rate period, the process in the porous medium is modelled as a receding evaporation front, the overall evaporation rate being determined by the combined effects of vapour transport through the pore network and subsequently into the air. The field trials programme was conducted at sites in the USA and the UK, and examined the evaporation of diethyl malonate droplets from sand and concrete surfaces. Vapour concentrations at several heights in the plume were measured at the centre of a 1 m radius annular source (of width 10 cm) contaminated by uniformly sized droplets (2.4 or 4.1 mm in diameter), key meteorological data being measured at the same time. The evaporation was quantified by coupling concentration and wind speed data. In all, 22 trials were performed on sand and concrete; a further 8 were performed an non-pore us surfaces (aluminium foil and slate) as references. The model performance was evaluated against the experimental data in terms of two quantities, the initial evaporation rate of the embedded droplets, and the mass-fraction remaining in the substrate at intervals over the evaporation episode. Overall, the model performance was best in the case of the field experiments for concrete, and the wind tunnel experiments for sand; the performance for wind tunnel experiments for concrete was reasonably good; in the case of the field experiments for sand there was significant underprediction of evaporation rates, though the trends with the determining variables were well predicted. (C) 1999 Elsevier Science Ltd. All rights reserved.

Abstract  Novel P*- and P-monodentate phosphoramidites of a 1,3,2-dioxaphosphepine series were derived from (S-a)-3-trimethylsilyl-BINOL, (R,S)-semi-TADDOL, and (R,R)-TADDOL. Catalytic performance of the synthesized compounds were examined in the Pd-catalyzed asymmetric allylic substitution of (E)-1,3-diphenylallyl acetate: the reaction with dimethyl malonate gave up to 92% ee. The effects of additives of 5,10,15,20-tetraphenylporphyrin and its metal complexes on conversion and enantioselectivity were studied.

Abstract  A simple and efficient procedure was developed for the preparation of [(Ph(3)P)(4)Rh-2(mu-OH)(2)], 1, from Wilkinson's catalyst and aqueous KOH under biphasic conditions (75-85% yield). Complex 1 reacted with cyclopentadiene, methyl malonate, and benzoic acid to give [CpRh(PPh(3))(2)], [(Ph(3)P)(2)Rh(CH(COOMe)(2))], and [(Ph(3)P)(2)Rh(mu-PhCOO)], respectively. Depending on the amount of formic acid, the reaction between 1 and HCOOH resulted in either decarboxylation and formation of [(Ph(3)P)(2)Rh(H)(2)(HCOOO)] or dehydration affording trans-[(Ph(3)P)(2)Rh(Co)(HCOO)], 6 both transformations being chemospecific. Treatment of 1 with [CpM(CO)(3)H] (M = Cr, Mo, W) gave heterobinuclear complexes, [(Ph(3)P)(2)Rh(mu-Co)(2)M(CO)Cp], in excellent yield. The structure of 6 was confirmed by X-ray analysis.

Abstract  Advances in the transition-metal catalyzed alpha-arylation of carbonyl derivatives and compounds with acidic hydrogen are reviewed.. By using sterically hindered, electron-rich alkylphosphines and N-heterocyclic carbenes(NHC), this process has encompassed a broad range of substrates including ketones, aldehydes, esters, amides, malonates, nitrocompounds, nitriles and sulfones.

Abstract  We have designed and synthesized a small library of modular monodentate diamidophosphite ligands with stereogenic phosphorus atoms. The library was prepared efficiently from the commercially available and inexpensive (S)-N-Boc-amino acids. These novel ligands were screened in the Pd-catalyzed asymmetric allylations of (E)-1,3-diphenylallyl acetate with dimethyl malonate as the C-nucleophile with up to 93% ee being obtained. The results showed that the different substituents in the 1,3,2-diazaphospholidine cycle had remarkable effects on the enantioselectivity. (c) 2013 Elsevier Ltd. All rights reserved.

Abstract  The phase transfer catalytic cyclopropa nation of the malonic ester of allylic alcohol or its 3,3-dibromo and 3,3-dichloro derivatives yields bicyclic cyclopropane carboxylic acid lactones; reduction of these lactones with LiAlH4 in boiling THF yields the appropriate 1,1,2-tris-(hydroxymethyl)cyclopropanes in satisfactory yield.

Abstract  Esters of 1,1,2,2-ethanetetracarboxylic acid or of ethylenetetracarboxylic acid were obtained by electrochemical oxidation of malonic esters in the presence of halides as mediators. Esters of 1,1,2,2,3,3-propanehexacarboxylic acid or of cyclopropanehexacarboxylic acid were obtained by electrolysis in the presence of alkali metal bromides. An analogous process was used fir electrochemical ring closure of substituted 1,1,3,3-propanetetracarboxcylic acid esters to substituted 1,1,2,2-cyclopropanetetracarboxylic acid esters and for the assembly of four and five-membered rings from the corresponding esters of alpha,alpha,omega,omega-alkanetetracarboxylic acids. Common features and differences between the electrolysis of malonic esters and the esters of beta-oxoalkanecarboxcylic acids, 1,3-diketones, and malononitrile were studied under the conditions of mediated electrooxidation in the presence of halides.

Abstract  While searching for new HIV integrase inhibitors we discovered that some ethyl malonate amides (EMA) are active against this enzyme. Surprisingly, the main function can only very rarely be found among the reported drug candidates. We synthesised a series of compounds in order to establish and analyse the structure-activity relationship. The similarity to the important classes of HIV integrase inhibitors as well as the synthetic availability of the different targets including this pharmacophore makes EMA compounds an interesting object of investigations.