Abstract  2-Methylprop-2-ene-, prop-2-ene-, 1-methylprop-2-ene-, and (E)-but-2-enesulfonyl chlorides have been used as electrophilic partners in desulfinylative palladium-catalyzed C-C coupling with Grignard reagents and sodium salts of dimethyl malonate and methyl acetoacetate. Neopentyl alk-2-ene sulfonates can also be used as electrophilic partners in desulfinylative allylic arylations and allylic alkylations. The regioselectivity of the allylic arylation and alkylation depends on the nature of the catalyst. With PdCl(2)(PhCN)(2), (E)-crotyl derivatives are formed in high regioselectivity using either 1-methylprop-2-ene- or (E)-but-2-enesulfonyl chloride. (C) 2008 Elsevier Ltd. All rights reserved.

Abstract  Two classes of indole-phosphine oxazoline ligands have been prepared from readily available starting materials in good overall yields. These modular ligands include an indole skeleton with either a phosphine moiety or an oxazoline ring at the 2- or 3-position, respectively. The utility of these ligands was demonstrated in a catalytic asymmetric reaction: the palladium-catalyzed allylic alkylation of 1,3-diphenyl-2-propenyl acetate with dimethyl malonate was performed with enantioselectivities as high as 98%. (C) 2010 Elsevier Ltd. All rights reserved.

Abstract  Optical limiting properties of methane [60]fullerene - diethyl malonate mono- and multiple-adducts were investigated systematically. For all of the fullerene derivatives in room-temperature solution, observed optical limiting responses toward the second harmonic of a Q-switched Nd:YAG nanosecond pulsed laser are strongly concentration dependent. The strong concentration dependence is likely due to effects on optical limiting contributions that are associated with bimolecular excited state processes in the fullerene derivatives. Consistent with such effects, optical limiting responses of the mono-adduct in polymethylmethacrylate polymer films are much weaker than those in concentrated solutions but in excellent agreement with those in dilute solutions. The results are explained in terms of a reverse saturable absorption mechanism that includes both unimolecular and bimolecular excited state processes of fullerenes.

Abstract  Zirconia and its modified forms such as 10%Mo(VI)/ZrO2, 10%V(V)/ZrO2, 10%W(VI)/ZrO2 and SO42-/ZrO2 were prepared and characterized for their physico-chemical properties such as BET for surface area, NH3-TPD and n-butylamine back titration method for total surface acidity, PXRD technique for crystallinity and ICP-OES technique for elemental analysis. These materials were used as catalysts in liquid phase transesterification reaction of diethyl malonate (DEM) with benzyl alcohol (BA). Optimization of reaction conditions such as reaction time, reaction temperature, weight of the catalyst and molar ratio of reactants were carried out to obtain highest possible transester yield. Dibenzyl malonate (DBM) and benzyl ethyl malonate (BEM) were obtained as major products. Highest total transester yield of (88%) was obtained in the presence of 0.75 g of SZ catalyst at a molar ratio of DEM:BA = 1:3, reaction temperature of 393 K and reaction time 5 h. Kinetic studies were carried out to find out the rate of the reaction and energy of activation values for zirconia catalysts, in order to identify a facile catalyst system for this reaction. A possible reaction mechanism was proposed based on the kinetic data and it was observed that Eley-Rideal mechanism fits well for this reaction. Reactivation and reusability studies of the catalysts were also taken up. (C) 2014 Elsevier B.V. All rights reserved.

Abstract  Mannich aminomethylation reactions involving M(aa)(2), where M = Cu, Ni and aa = glycine(gly), DL-alanine(DL-ala), L-alanine(L-ala), with formaldehyde and diethylinalonate have been carried out, resulting in carboxylate appended systems in high yield. All the compounds have been characterized by UV-Vis spectroscopy, infrared spectroscopy and elemental analysis. One of the synthesized complexes, (5,5-dicarboxyethyl-3,7-diazanonanedioato)copper(II) monohydrate, has been characterized by single crystal XRD and has been used as catalyst in the hydrogen peroxide-induced degradation of pyrocatechol violet (PCV) dye. The variations in the rate of degradation of the dye with respect to change in concentration of hydrogen peroxide, dye, catalyst and pH have been studied. Effect of addition of NaCl has been studied and a suitable mechanism based on the formation of free radical species during the degradation process has been proposed. (c) 2007 Elsevier Ltd. All rights reserved.

Abstract  A series of lower rim-functionalised calix[4]arenes bearing 1,3-positioned phosphorus(III) ligands L-1-L-9 have been synthesized and their coordinative properties examined. L-1 and L-2 {5,11,17,23-tetra-tert-butyl-25,27-bis[2-(diphenylphosphino)ethoxy]- and -25,27-bis(diphenylphosphinomethoxy)-26,28-bis(3-oxabutyloxy)calix[4]arene} react with [Rh(nbd)(THF)(2)]BF4 (nbd=1,5-norbornadiene; THF=tetrahydrofuran) to afford in high yield the complexes [Rh(nbd)L-1]BF4 and [Rh(nbd)L-2]BF4, respectively, where the calixarene behaves as a P,P' chelator. Both complexes catalyse hydroformylation of styrene at comparable rates, the linear:branched aldehyde ratio being 5:95. The presence of the ether side groups did not exert a noticeable effect on the selectivity nor the catalytic activity. Reaction of L-1-L-8 with [Pd(eta (3)-C3H4Me)(THF)(2)]BF4 gave the corresponding cationic chelate complexes [Pd(eta (3)-C3H4Me)L-i]BF4 that are active in the catalytic alkylation of 1,3-diphenylprop-2-enyl acetate with dimethyl malonate. Owing to the presence of a non-planar Pd-allyl fragment, the achiral calixarene subunits of some of these complexes are no longer C-2v-symmetrical, as evidenced by the H-1 and C-13 NMR spectra that show non-equivalent side groups. Selective chelation via the two phosphorus atoms was also observed in the complexes [RuCl(p-MeC6H4Pri)L-i]BF4 (L-i=L-3 or L-4) obtained by reaction of the amide phosphines L-i with [RuCl(p-MeC6H4Pri)(THF)(2)]BF4 [L-3=5,11,17,23-tetra-tert-butyl-25,27-bis(diethylcarbamoylmethoxy)-26,28-bis(diphenylphosphinomethoxy)- and L-4=5,11,17,23-tetra-tert-butyl-25,27-bis(diphenylphosphinomethoxy)-26,28-bis{(1-(R)-phenylethyl)carbamoylmethoxy}-calix[4]arene]. Reaction of L-3 or L-4 with neutral [RuCl2(p-MeC6H4Pri)](2) afforded the bimetallic complexes [{RuCl(p-MeC6H4Pri)}(2)L-i] where the calixarene acts as a P,P' bridging ligand. Reaction of AgBF4 with calix-crown L-9 {25,27-bis(diethoxyphosphinoxy)-26,28-(3,6,9-trioxaundecane-1,11-dioxy)calix[4]arene} resulted in quantitative formation of the complex [AgL9]BF4 in which the silver(I) ion lies inside the cavity constituted by the crown ether fragment and the two phosphorus arms. As revealed by a single crystal X-ray diffraction study, the Ag+ ion has a trigonal P2O coordination environment with a P-Ag-P angle of 134.74(4)degrees.

Abstract  Highly enantioselective Michael addition reactions of diethyl malonate to various chalcones have been achieved under mild chiral multisite phase-transfer reaction conditions by the successful utilization of 2,4,6-(triscinchoniummethyl)phenyl-1,3,5-triazines as new chiral quaternary ammonium catalysts. This simple asymmetric Michael addition process was found to be quite effective and to obtain Michael adducts with very good yields and enantiomeric excesses.

Abstract  Contrary to the widely held opinion that protic (''acidic'') solvents favor monoalkylation whereas aprotic (''inert'') solvents support dialkylation of diethyl malonate carbanion, exactly opposite results have been obtained in the reaction of the dibromide 7, tetrabromide 4 and hexabromide 1 in ethanol and dimethyl sulfoxide, the former solvent preferring strongly dialkylation (cyclization) and the latter monoalkylation. Investigation in a broader spectrum of solvents demonstrated that hydrogen bonding as well as ion-pairing may play an important role in the selectivity control, both strongly supporting dialkylation. When a separation of ion-pairs is induced with 18-crown-6, monoalkylation prevails in the reaction. The solvent and the leaving group employed have been found to participate in the selectivity control. In DMSO, propensity to dialkylation increases strongly in the order I < Br << Cl, again in discord with earlier predictions. Rationale for the novel findings is provided on the basis of kinetic analysis of the overall reaction and is expressed by the limiting equations (5) and (7). (C) 1997 Elsevier Science Ltd.

Abstract  Two novel supramolecular complexes-of types [Ru(L)(H2L)Cl.OH2] and [Ru(HLn)Cl-3] (where H2L is a potential tetradentate ligand derived from hydrazine hydrate and diethyl malonate, and HLn is a potential bidentate ligand derived from coupling of allyl azo-beta-diketone) have been synthesized and characterized by elemental analysis, conductance and magnetic measurements, followed by H-1 NMR, to determine the effect of substituents on the intramolecular hydrogen bond. The electronic properties and models of the bonding of ligands and complexes were investigated by UV-Vis and IR spectroscopies. The first type of complex contains terminal hydrazinic nitrogen atoms with an unshared electron pair and may take part in nucleophilic condensations. Therefore, the reactions of allyl-beta-diketone complexes with malonic dihydrazide have also been studied, as these cause ring closure and formation of supramolecular macrocyclic ligand complexes. The wavelengths of the principal electronic absorption peaks have been accounted for quantitatively in terms of crystal field theory, and various parameters have been evaluated. On the basis of the electronic spectra, an octahedral geometry has been established for the polymer complexes C. The macrocyclic polymer complexes D are pentacoordinate, and a trigonal-bipyramidal environment (D-3h) is suggested for the ruthenium(III) ion. The effect of the Hammett constant on the ligand field parameters is also discussed. Copyright (C) 2004 John Wiley Sons, Ltd.

Abstract  3-(4-Oxo-5,6,7,8-tetrahydro-4H-benzo[4,5]thieno[2,3-d][1,3]oxazin-2-yl)propanoic acid and its ethyl ester 6ab have been prepared via succinoylation of ethyl 2-amino-4,5,6,7-tetrahydrobenzo[b]thlophene-3-carboxylate 1, followed by ester hydrolysis, selective esterification, and acetic anhydride induced cyclization of the thiophenecarboxylic acid derivatives 3, 5. Reaction of 1 with diethyl malonate gave the malonic acid diamide 7, which on ester hydrolysis followed by acetic anhydride induced water elimination furnished the 2-substituted 4H-benzo[4,5]thieno[2,3-d][1,3]oxazine derivative 10 in high yield. A series of new benzo[4,5]thieno[2,3-d]pyrimidines 11-19, which bear a propanoic acid substituent in the 2-position and an amino, aryl, aminosugar, and arylmethylideneamino-substituents in the 3-position have been prepared via the reaction of 6ab with hydrazine hydrate or aromatic amines followed by treatment with aromatic aldehydes, isatin, or aldoses. The aldimines 18a-d underwent unprecedented acid catalyzed tandem cyclization-transannular aldehyde extrusion into octalzydro-1H-benzo[4'.5']thieno[2'.3'.4,5]pyrimido[1,2-b]pyridazines 21. Two other unequivocal approaches for 21 also have been explored, either by treatment of the amino acid derivative 11 with thionyl chloride or by thermal cyclization of the amino ester derivative 12.

Abstract  A highly enantioselective α-benzoyloxylation of malonic diester has been achieved by phase-transfer catalysis. The reaction of α-monosubstituted tert-butyl methyl malonate with benzoyl peroxide in the presence of aqueous KOH and N-(9-anthracenylmethyl)cinchoninium chloride afforded the corresponding α,α-disubstituted products in generally excellent chemical yields (up to 99% yield) with high enantioselectivities (up to 96% ee). In addition, the utility of this methodology was exhibited by the synthesis of a mineralocorticoid receptor antagonist.

Abstract  Total synthesis of (±)-antroquinonol D, which is isolated from very expensive and rarely found Antrodia camphorata and which has potential anticancer properties, was achieved from 4-methoxyphenol. In addition, a Michael addition to dimethoxy cyclohexadienones was studied. The main step involved chelation and substrate-controlled diastereoselective reduction of cyclohexenone and lactonization. Lactone synthesis facilitated the diastereoselective reduction of ketone, which help control the desired stereochemistry at the crucial stereogenic center in the natural product. Other key reactions in the synthesis involved a Michael addition of dimethyl malonate on cyclohexadienone, dihydroxylation, and Wittig olefination. A sesquiterpene side chain was synthesized through coupling with geranyl phenyl sulfide and Bouveault-Blanc reduction.

Abstract  Inhibition of intestinal and hepatic microsomal triglyceride transfer protein (MTP) is a potential strategy for the treatment of dyslipidemia and related metabolic disorders. Inhibition of hepatic MTP, however, results in elevated liver transaminases and increased hepatic fat deposition consistent with hepatic steatosis. Diethyl 2-((2-(3-(dimethylcarbamoyl)-4-(4'-(trifluoromethyl)-[1,1'-biphenyl]-2-ylcarboxamido)phenyl)acetoxy)methyl)-2-phenylmalonate (JTT-130) is an intestine-specific inhibitor of MTP and does not cause increases in transaminases in short-term clinical trials in patients with dyslipidemia. Selective inhibition of intestinal MTP is achieved via rapid hydrolysis of its ester linkage by liver-specific carboxylesterase(s), resulting in the formation of an inactive carboxylic acid metabolite 1. In the course of discovery efforts around tissue-specific inhibitors of MTP, the mechanism of JTT-130 hydrolysis was examined in detail. Lack of ¹⁸O incorporation in 1 following the incubation of JTT-130 in human liver microsomes in the presence of H₂¹⁸O suggested that hydrolysis did not occur via a simple cleavage of the ester linkage. The characterization of atropic acid (2-phenylacrylic acid) as a metabolite was consistent with a hydrolytic pathway involving initial hydrolysis of one of the pendant malonate ethyl ester groups followed by decarboxylative fragmentation to 1 and the concomitant liberation of the potentially electrophilic acrylate species. Glutathione conjugates of atropic acid and its ethyl ester were also observed in microsomal incubations of JTT-130 that were supplemented with the thiol nucleophile. Additional support for the hydrolysis mechanism was obtained from analogous studies on diethyl 2-(2-(2-(3-(dimethylcarbamoyl)-4-(4'-trifluoromethyl)-[1,1'-biphenyl]-2-ylcarboxamido)phenyl)acetoxy)ethyl)-2-phenylmalonate (3), which cannot participate in hydrolysis via the fragmentation pathway because of the additional methylene group. Unlike the case with JTT-130, ¹⁸O was readily incorporated into 1 during the enzymatic hydrolysis of 3, suggestive of a mechanism involving direct hydrolytic cleavage of the ester group in 3. Finally, 3-(ethylamino)-2-(ethylcarbamoyl)-3-oxo-2-phenylpropyl 2-(3-(dimethylcarbamoyl)-4-(4'-(trifluoromethyl)-[1,1'-biphenyl]-2-ylcarboxamido)phenyl)acetate (4), which possessed an N,N-diethyl-2-phenylmalonamide substituent (in lieu of the diethyl-2-phenylmalonate motif in JTT-130) proved to be resistant to the hydrolytic cleavage/decarboxylative fragmentation pathway that yielded 1, a phenomenon that further confirmed our hypothesis. From a toxicological standpoint, it is noteworthy to point out that the liberation of the electrophilic acrylic acid species as a byproduct of JTT-130 hydrolysis is similar to the bioactivation mechanism established for felbamate, an anticonvulsant agent associated with idiosyncratic aplastic anemia and hepatotoxicity.

Abstract  A systematic study concerning the immobilisation onto magnetic nanoparticles of three useful classes of chiral organocatalyst which rely on a confluence of weak, easily perturbed van der Waals and hydrogen bonding interactions to promote enantioselective reactions has been undertaken for the first time. The catalysts were evaluated in three different synthetically useful reaction classes: the kinetic resolution of sec-alcohols, the conjugate addition of dimethyl malonate to a nitroolefin and the desymmetrisation of meso anhydrides. A chiral bifunctional 4-N,N-dialkylaminopyridine derivative could be readily immobilised; the resulting heterogeneous catalyst is highly active and is capable of promoting the kinetic resolution of sec-alcohols with synthetically useful selectivity under process-scale friendly conditions and has been demonstrated to be reusable in a minimum of 32 consecutive cycles. The immobilisation of a cinchona alkaloid-derived urea-substituted catalyst proved considerably less successful in terms of both catalyst stability and product levels of enantiomeric excess. An immobilised cinchona alkaloid-derived sulfonamide catalyst was also prepared, with mixed results: the catalyst exhibits outstanding recyclability on a par with that associated with the successful N,N-dialkylaminopyridine analogue, however product enantiomeric excess is consistently lower than that obtained using the corresponding homogeneous catalyst. While no physical deterioration of the heterogeneous catalysts was detected on analysis after multiple recycles, in the cases of both the conjugate addition to nitroolefins and the desymmetrisation of meso anhydrides, significant levels of background catalysis by the nanoparticles in the absence of the organocatalyst was detected, which explains in part the poor performance of the immobilised organocatalysts in these reactions from a stereoselectivity standpoint. It seems clear that the immobilisation of sensitive chiral organocatalysts onto magnetite nanoparticles does not always result in heterogeneous catalysts with acceptable activity and selectivity profiles, and that consequently the applicability of the strategy must be ascertained (until more data is available) on a case-by-case basis.

Abstract  Herein we report the design and synthesis of multifunctional hyperbranched polyester-based nanoparticles and nanocomposites with properties ranging from magnetic, fluorescence, antioxidant and X-ray contrast. The fabrication of these nanostructures was achieved using a novel aliphatic and biodegradable hyperbranched polyester (HBPE) synthesized from readily available diethyl malonate. The polymer's globular structure with functional surface carboxylic groups and hydrophobic cavities residing in the polymer's interior allows for the formation of multifunctional polymeric nanoparticles, which are able to encapsulate a diversity of hydrophobic cargos. Via simple surface chemistry modifications, the surface carboxylic acid groups were modified to yield nanoparticles with a variety of surface functionalizations, such as amino, azide and propargyl groups, which mediated the conjugation of small molecules. This capability achieved the engineering of the HBPE nanoparticle surface for specific cell internalization studies and the formation of nanoparticle assemblies for the creation of novel nanocomposites that retained, and in some cases enhanced, the properties of the parental nanoparticle building blocks. Considering these results, the HBPE polymer, nanoparticles and composites should be ideal for biomedical, pharmaceutical, nanophotonics applications.

Abstract  An enantiodivergent strategy for the total chemical synthesis of both naturally occurring (+)-fomannosin (1) and its (-)-antipode (ent-1) from alpha-D-glucose has been developed and successfully implemented. The key steps in the overall pathway include the following: (i) application of the zirconocene-mediated ring contraction of vinyl furanosides for the construction of highly substituted cyclobutanols; (ii) the use of ring-closing metathesis to form the pendant five-membered ring; (iii) making recourse to a monothio malonic ester to allow for chemoselective reduction to sensitive lactone intermediate 45; (iv) hydroxyl-directed dihydroxylation with OsO(4) to generate 48; and (v) sequential elimination via a cyclic sulfite and a cyclobutyl triflate. The bridge between the enantiomeric series consisted of a six-step linkup involving the structural modification of 22 so as to generate ent-30b. Optical activity was fully preserved throughout.

Abstract  This (1)H nuclear magnetic resonance metabonomics study was aimed to determine urinary biomarkers of cholestasis resulting from inhibition of biliary secretion of bile or obstruction of bile flow. To inhibit biliary secretion of bile, cyclosporine A was administered to male Sprague-Dawley rats. Obstruction of bile flow was induced by administration of 4,4'-methylene dianiline, alpha-naphthylisothiocyanate or bile duct ligation. Clinical pathological and histopathological examinations were performed to confirm cholestatic injury and (1)H nuclear magnetic resonance spectral data for urine samples were analysed to determine similarities and differences in profiles of metabolites using the Spotfire. In cyclosporine A-treated groups, serum total bilirubin and bile acid were significantly increased but no remarkable hepatic histopathological-changes were observed. In 4,4'-methylene dianiline-, alpha-naphthylisothiocyanate- and bile duct ligation-treated groups, serum alkaline phosphatase, gamma-glutamyltranspeptidase and total bilirubin levels increased significantly, and hepatic histopathological-changes were observed. On urinary (1)H nuclear magnetic resonance spectral analysis, area intensities derived from 0.66 to 1.90 ppm were decreased by cyclosporine A, whereas they were increased by other treatments. These metabolites were identified using the NMR suite as bile acids, branched-chain amino acids, n-butyrate, propionate, methyl malonate and valerate. These metabolites were further investigated by K-means clustering analysis. The cluster of these metabolites is considered to be altered by cholestasis. We conclude that bile acids, valine and methyl malonate have a possibility to be urinary cholestatic biomarkers, which distinguish a difference in mechanism of toxicity. (1)H nuclear magnetic resonance metabonomics thus appears to be useful for determining the mechanisms of toxicity and can be front-loaded in drug safety evaluation and biomarker discovery.

Abstract  Three new hybrid ligands with trans-1,2-diaminocyclohexane backbone have been synthesized from (1R,2R)-2-aminocyclohexylcarbamic acid tert-butyl ester (4), which is prepared through an indirect monoprotection of the diamine. The ligands are (1R, 2R)-N-2-[2-(dimethylamino)benzoyl]aminocyclohexyl-2-(diphenylphosph anyl)benzamide and its di-n-butylamino- and diphenylamino-derivatives (3a-c), which belong to formal P,N-type chelates with possible wide bite angles in the metal chelation. To evaluate the new hybrid ligands against well-known P,N- and P, P-chelates (1 and 2), they were employed in the palladium-catalyzed allylic alkylations between two standard racemic allylic acetates, 2-acetoxy-1,3-diphenyl-2-propene (14a) and 2-acetoxy-1, 3-dimethyl-2-propene (14b), and dimethyl malonate under different reaction conditions. The catalytic system with the new ligands showed good reactivity toward both the substrates with moderate enantioselectivities (up to 78% ee toward 14a and 80% ee toward 14b). Of particular note, dramatic changes in the sense and in the degree of the enantioselectivity were observed depending on the ligands and reaction conditions, which suggested a different chelation mode was competing with the supposed P,N-chelation mode. An X-ray crystal structure of a chelated palladium complex [Pd(3c)(eta(3)-PhCHCHCHPh)]PF(6) was obtained, which showed a P, O-chelation mode in which a carboxamide oxygen acted as the O-ligand. This is the first example of the enantioselective palladium-catalyzed allylic alkylation in which a P,O-chelated complex of a carboxamide group participated as the ligand group.

Abstract  The Lewis acid-mediated reactions of allene-ene compounds, derived from 3-methylcitronellal or dimethyl malonate, were carried out using various Lewis acids such as ethylaluminum dichloride, diethylaluminum chloride, titanium chloride, zinc chloride etherate, or boron trifluoride etherate, affording unexpectedly intramolecular [2+2]cycloaddition products under some particular reaction conditions without any formation of intramolecular ene reaction products.

Abstract  The purpose of the research was to synthesize beta-diketo esters and to evaluate them for anticonvulsant activity. The reaction of methyl vinyl ketone with dimethyl malonate in the presence of potassium carbonate gave an uncyclized product that underwent a Claisen condensation to yield methyl 2-hydroxy-4-oxocyclohex-2-en-1-oate (5a). Similarly, other cyclized beta-hydroxyketo esters were prepared, and their spectrometric data confirmed that the enol tautomers were preferred to the beta-diketo tautomers. The synthetic work clarified the reaction pathway for the Michael addition of malonate esters to enones. Of the intermediates and products tested for anticonvulsant activity, dimethyl 2,2-bis-(3-oxobutyl)malonate (9a) was found to possess anticonvulsant property. However, it is emphasized that the beta-hydroxyketo esters could be useful intermediates in the synthesis of enaminone anticonvulsants.

Abstract  The uptake of dimethyl malonate and dimethyl succinate on aqueous surfaces was measured between 266 and 279 K, using the droplet train technique coupled with mass spectrometric detection. The uptake coefficients gamma were found to be independent of the aqueous phase composition and of the gas-liquid contact times. In addition, the uptake coefficients and the derived mass accommodation coefficients a show a negative temperature dependence in the temperature ranges studied. The mass accommodations decrease from 7.8 x 10(-2) to 5.0 x 10(-2) and from 4.5 x 10(-1) to 2.3 x 10(-2) for dimethyl malonate and succinate, respectively. These results are used to discuss the incorporation of oxygenated volatile organic compounds (VOCs) into the liquid using the nucleation theory. Henry's law constants of both compounds were directly measured between 283 and 298 K using a dynamic equilibrium system. Their values exponentially decrease when temperature increases, from (2.60 +/- 0.30) x 10(4) to (0.40 +/- 0.05) x 10(4) and from (1.20 +/- 0.10) x 10(4) to (0.30 +/- 0.03) x 10(4) for dimethyl malonate and succinate, respectively (in units of M atm(-1)). The partitioning of both dibasic esters between gas and aqueous phases and the corresponding atmospheric lifetimes have then been derived.

Abstract  A bifunctional catalytic system formed by Pd on MgO catalyzes the cascade process between benzyl alcohol and phenylacetonitrile, diethylmalonate and nitromethane, to give the respective alpha-monoalkylated products without external supply of hydrogen. The process involves a series of three cascade reactions occurring on different catalytic sites. The alcohol undergoes oxidation to the corresponding aldehyde with the simultaneous formation of a metal hydride; then, the aldehyde reacts with a nucleophile formed "in situ" to give an alkene, and finally, the hydrogen from the hydride is transferred to the alkene to give a new C-C bond. A kinetic study on the alpha-monoalkylation reaction of benzylacetonitrile with benzyl alcohol reveals that the rate-controlling step for the one-pot reaction sequence is the hydrogen transfer reaction from the surface hydrides to the olefin, and consequently, the global reaction rate is improved when decreasing the size of the Pd metal particle. (C) 2011 Elsevier Inc. All rights reserved.