The STOBBE condensation with substituted succinic esters,part I. A Synthesis of Benzothiophene Derivatives

The condensation of some thienyl carbonyl compounds with dimethyl methylsuccinate in presence of potassium t-butoxide or sodium hydride gave predominantly the (E)-half-esters

1 i. e., CO₂CH₃ group and thiophene ring in trans-position. The nomenclature of cis/trans isomers used herein follows the IUPAC 1968 Tentative Rules, Section E, Fundamental Stereo-chemistry, J. Org. Chem. 35 , 2849 (1970). See also: J. E. Blackwood, C. J. Gladys, K. L. Loening, A. E. Petrarca, and J. E. Rush, J. Amer. chem. Soc. 90 , 510 (1968); Introduction to Subject Index of Chem. Abstr. 66 (1963).

1a – d , which were cyclised to benzothiophene derivatives 2a – d . The (E)-dibasic acids 6a – d were converted to the corresponding anhydrides 7a – d , which upon methanolysis produced the isomeric half-esters 8a – d . Treatment of 6d with concentrated sulphuric acid gave the cyclic ketonic lactone 9 together with the fluorenone derivative 10 .     

The STOBBE Condensation with Pyrrolyl Aldehydes – a synthesis of indole derivatives

The condensation of pyrrolyl-2-aldehyde or 1-methyl-pyrrolyl-2-aldehyde with dimethyl succinate, using sodium hydride as condensing agent, gave predominantly the halfesters 1a and 1c respectively. Their structure and (E)-configuration

1 i. e., pyrrol ring and COOCH₃ group are in trans position. This nomenclature follows the IUPAC 1968 Tentative Rules, Section E, Fundamental Stereochemistry, J. org. Chemistry 35 , 2849 (1970).

were confirmed by their cyclisation to the corresponding indole derivatives 2a–h .     

Stevensanaloge,Durch Nickelkomplexe Katalysierte Umlagerung Von Triarylphosphoryliden Und Darstellung Sowie Strukturbestimmung Von Phosphorylid-Nickeltricarbonylkomplexen

The Stevens rearrangement of the triarylphosphorusylids R₃ P=CHR′ (III) (R′ = H, CH₃, C₂ H₅) to diarylbenzylphosphines (V) is catalyzed by nickel complexes (e.g., (COD)₂ Ni (I)). Attempts to prepare trimesitylphosphine-methylene result in direct formation of dimesityl (mesitylmethyl) phosphine (XII) — the first recorded direct Stevens rearrangement of a phosphorusylid. Phosphorusylids react with nickeltetracarbonyl without rearrangement to give complexes of the type R₃P=CH_a · Ni(CO)₃ (XIV). The structure of XIV has been established by the IR and NMR spectra and confirmed by an X-ray structural determination.

1 B. L. Barnett and C. Krüger, J. Cryst. Mol. Struct., im Druck.

The ylid is bonded to the nickel through the C-atom with resulting hybridization from sp² towards sp³.     

Carbon dioxide reforming of methane in kilohertz spark‐discharge plasma at atmospheric pressure

The spark‐discharge plasma, generated between tubular and rotary‐disc electrodes using a sine‐wave high voltage with 5 kHz frequency, was explored for CO₂ reforming of CH₄. Based upon the investigation on the effects of specific energy input and CO₂/CH₄ ratio, the energy costs (EC) and fuel‐production efficiencies (η) at various CO₂/CH₄ ratios (r) in the same conversion range were compared and accordingly their sequences were given: EC (r = 0.5) and EC (r = 3) are the lowest; η(r = 0.5) is the highest. Compared with other nonthermal discharge techniques, the kilohertz spark discharge exhibits low EC and high fuel‐production efficiency, especially at high total‐carbon conversions. Preliminary investigation on partial oxidation and CO₂ mixed reforming at (O₂ + CO₂)/CH₄ = 0.5 exhibited high H₂/CO ratio (nearly 2) and low total‐carbon EC (0.59–0.96 MJ/mol, 58–77% of total‐carbon conversion, and O₂/(CO₂ + O₂) = 0.8). © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Neutral Pd(II) and Ni(II) Acetylide Catalysts for the Polymerization of Methyl Methacrylate

Homogenous polymerization of methyl methacrylate using Pd(II)- and Ni(II)-based acetylide complexes as initiators has been investigated. M(PR'₃)₂(CCR)₂ (M=Pd, Ni; R'=PPh₃, Pn-Bu₃; R=Ph, CH₂OH, CH₂OOCCH₃, CH₂OOCPh, CH₂OOCPhOH-o) were found to be a novel type of effective initiators for the polymerization of methyl methacrylate. Among them, Pd(C CPh)₂(PPh₃)₂ (PPP) shows the highest activity in the MMA polymerization and the PMMA obtained is a syndiotactic polymer with high number-average molecular weight (M _n) of 14.1 × 10⁴. Some features and kinetic behavior of MMA polymerization initiated by PPP were studied in detail. The polymerization reaction is first-order with respect to both [PPP] and [MMA]. Radical polymerization mechanism is proposed.     

Polyorganosiloxanes containing both ester and hydride functionalities: A detailed study by 1H and 13C NMR spectroscopy

A total of eighteen linear polysiloxanes of general formula Me₃SiO-(MeSi(E)O)_x(MeSi(H)O)_ySiMe₃ (E = —(CH₂)_nester; x+y = 40) have been prepared by the platinum catalysed addition of CH₂=CH(CH₂)_n-2 -ester to Me₃SiO-(MeSi(H)O)₄₀SiMe₃ under anhydrous conditions. Polymers containing the ester functionalities—(CH₂)₃CO₂R(R = Me, CF₃, Et, Pr, and CH₂COMe),—(CH₂)₃-CHMeCO₂Et, —(CH₂)₂CH(CO₂Me)₂, —(CH₂)₃CH(CO₂Et)₂, -(CH₂)₃CO₂CH= CHCO₂CH₂CH=CH₂ and —(CH₂)₃CO₂C₆H₄CO₂ CH₂CH=CH₂ have been characterised by analysis and ¹H and ¹³C NMR spectroscopies. Factors affecting Markownik off versus anti-Markownikoff addition of allyl acetate to this polymethylsiloxane have also been explored.     

Aspartic acid in a new role: Synthesis and application of a pH-responsive cyclopolymer containing residues of the amino acid

The reaction between diallylamine and dimethyl maleate afforded the Michael addition product dimethyl N,N-diallylaspartate [(CH₂CH–CH₂)₂NCH(CO₂Me)CH₂CO₂Me] I, which upon treatment with dry HCl and ester hydrolysis with aqueous HCl gave its hydrochloride salt [(CH₂CH–CH₂)₂NH⁺CH(CO₂Me)CH₂CO₂Me Cl⁻] II and N,N-diallylaspartic acid hydrochloride [(CH₂CH–CH₂)₂NH⁺CH(CO₂H)CH₂CO₂H Cl⁻] III, respectively. The new monomers II and III underwent cyclopolymerization to give, respectively, cationic polyelectrolytes (CPEs) poly(II) and poly(III). Under the influence of pH, triprotic acid (+) poly(III) was equilibrated to water-insoluble diprotic polyzwitterionic acid (±) IV, water-soluble monoprotic poly(zwitterion–anion) (± −) V, and its conjugate base polydianion (=) VI. The protonation constants of the carboxyl group and trivalent nitrogen in VI have been determined. A 20-ppm concentration of IV is effective in inhibiting the precipitation of CaSO₄ from its supersaturated solution with an ≈ 100% scale inhibition efficiency for a duration of 50 h at 40 °C. The aqueous two-phase systems (ATPSs) of VI and polyoxyethylene have been studied. The transformation of water-soluble VI to insoluble IV makes it a recycling ATPS as it can be recycled by precipitation at a lower pH.     

Effects of Elevated CO2 and Temperature on Methane Production and Emission from Submerged Soil Microcosm

Incubation experiments were conducted under controlled laboratory conditions to study the interactive effects of elevated carbon dioxide (CO₂) and temperature on the production and emission of methane (CH₄) from a submerged rice soil microcosm. Soil samples (unamended soil; soil + straw; soil + straw + N fertilizer) were placed in four growth chambers specifically designed for a combination of two levels of temperature (25 °C or 35 °C) and two levels of CO₂ concentration (400 or 800 mol mol^–1) with light intensity of about 3000 Lx for 16 h d^–1. At 7, 15, 30, and 45 d after incubation, CH₄ flux, CH₄ dissolved in floodwater, subsurface soil-entrapped CH₄, and CH₄ production potential of the subsurface soil were determined. The results are summarized as follows: 1) The amendment with rice straw led to a severalfold increase in CH₄ emission rates, especially at 35 °C. However, the CH₄ flux tended to decrease considerably after 15 d of incubation under elevated CO₂. 2) The amount of entrapped CH₄ in subsurface soil and the CH₄ production potential of the subsurface soil were appreciably larger in the soil samples incubated under elevated CO₂ and temperature during the early incubation period. However, after 15 d, they were similar in the soil samples incubated under elevated or ambient CO₂ levels. These results clearly indicated that elevated CO₂ and temperature accelerated CH₄ formation by the addition of rice straw, while elevated CO₂ reduced CH₄ emission at both temperatures.     

Steric and Polar Effects in the STOBBE condensation of aryl isopropyl ketones with dimethyl methylsuccinate

The condensation of phenyl-, p-tolyl-, p-anisyl-, and p-chlorophenyl isopropyl ketones with dimethyl methylsuccinate in the presence of potassium t-butoxide, gave the crystalline (E)-4-aryl-3-methoxycarbonyl-2-methyl-4-isopropyl-but-3-enoic acids

1 i.e., Ar and COOCH₃ in trans-position. The nomenclature of cis/trans isomers used herein follows the IUPAC 1968 Tentative Rules, Section E, Fundamental Stereochemistry, J. org. Chemistry 35 , 2849 (1970). See also: J. E. BLACKWOOD , C. L. GLADYS , K. L. LOENING , A. E. PETRARCA and J. E. RUSH , J. Amer. chem. Soc. 90 , 510 (1968); Introduction to Subject Index of Chem. Abstr. 66 (1963).

1 as major products. These esters resisted oxidation, and the position of the double bond was indicated by their infrared absorption, as well as that of some derived products. Their configuration followed from their conversion to the 4-acetoxy-2-naphthoates 2 . The condensation also gave oily half-ester fractions which proved to contain small amounts of the (Z)-isomers 5 by their conversion (in low yields) to the oxoindenyl acids 6 .     

Methane oxidation to acetic acid catalyzed by Pd2+ cations in the presence of oxygen

Synthesis of acetic acid from methane catalyzed by Pd²⁺ cations dissolved in sulfuric acid was investigated to determine the effects of reaction conditions and the mechanism. Acetic acid yield was found to be a strong function of CH₄ and O₂ partial pressures. High O₂/CH₄ ratio and high total pressure delivered the highest yield of acetic acid (14.2 turnovers of Pd²⁺) and the highest retention of Pd²⁺ in solution (96%). Byproducts were sulfur containing compounds (most notably methyl bisulfate) and CO_x, but the acetic acid selectivity was maximized (82%) by lowering the reaction temperature. Methane is activated by Pd(OSO₃H)₂, forming (CH₃)Pd(OSO₃H). CO, generated from the oxidation of methyl bisulfate, inserts into the CH₃Pd bond creating a (CH₃CO)Pd(OSO₃H) species. Reaction of this complex with H₂SO₄ produces acetic acid. Pd²⁺ is reduced to Pd⁰ during the oxidation of methyl bisulfate or CO, and Pd⁰ is reoxidized to Pd²⁺ by H₂SO₄ and O₂.     

Ring‐opening polymerization of trimethylenecarbonate by the bridged diphenoxo ytterbium (II) complex

A novel ytterbium (II) complex 2 supporting by a bridged bisphenolate ligand H₂L^OC4H7 (L = C₄H₇OCH₂N(CH₂‐2‐OC₆H₂‐3,5‐Bu)₂) with a tetrahydrofuran donor on side‐arm was synthesized in high yield and characterized by elementary analysis, IR, ¹H‐NMR, and ¹³C‐NMR. Ring‐opening polymerization of 1,3‐trimethylenecarbonate (TMC) was carried out using complex 2 and a known complex [Me₂NCH₂CH₂N(CH₂‐2‐O‐3,5‐C₆H₂(Bu^t)₂)₂]Yb 1 as the initiators, respectively. It was found that both complexes 1 and 2 can alone initiate the ring‐opening polymerization of TMC, and complex 1 showed higher activity than complex 2 . The activity of both complexes 1 and 2 was found to be higher than that of monodentate phenoxo ytterbium (II) complex (2,6‐Bu‐C₆H₃O)₂Yb(THF)₃. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

13C NMR chemical shifts of polyisobutylene end groups and related model compounds

Summary The detailed end-structures of CH₃-,-Cl, exo-olefin, endoolefin, and-OH ended polyisobutylenes (PIB) have been characterized by high resolution¹³C NMR spectroscopy. Specifically, the¹³C chemical shifts characteristic of the various carbons in the following structures have been determined: CH₂C(CH₃)₂-CH₂C(CH₃)₃, CH₂C(CH₃)₂CH₂C(CH₃)₂Cl, CH₂C(CH₃)₂CH₂C(CH₃)=CH₂, CH₂C(CH₃)₂CH=C(CH₃)₂, and CH₂C(CH₃)₂CH₂CH(CH₃)CH₂OH. The structure analysis of model compounds was of utmost help in these investigations. The above information is of great value for the identification of terminally functional PIBs and analysis of reaction mixtures.     

Stimuli-responsive conjugated polymers. Synthesis and chiroptical properties of polyacetylene carrying l-glutamic acid and azobenzene in the side chain

A glutamic acid- and azobenzene-containing novel N-propargylamide, (S)-CHCCH₂NHCOCH(CH₂CH₂CO₂CH₂C₆H₅)NHCO₂CH₂CH₂-p-C₆H₄NNC₆H₅ (1) was synthesized and polymerized with (nbd)Rh⁺[η⁶-C₆H₅B⁻(C₆H₅)₃] as a catalyst to obtain the corresponding polymer [poly(1)] with the moderate number-average molecular weight of 12,200 in 93% yield. The chiroptical studies revealed that poly(1) took a helical structure in THF, CHCl₃, CH₂Cl₂ and toluene. Poly(1) underwent solvent and heat-driven helix-helix transition. The trans-azobenzene of the side chain isomerized into cis upon UV-irradiation, accompanying decrease in helicity. The cis-azobenzene moiety reisomerized into trans upon visible-light irradiation, while the polymer did not recover the original helicity.     

Miscibility of linear low density polyethylene (LLDPE)-graft-poly(methyl methacrylate) with poly(vinylidene fluoride) (PVF2) and its application as compatibilizer LLDPE/PVF2 blends

Differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) were used to study the miscibility of blends of a graft copolymer of poly(methyl methacrylate) on linear low density polyethylene (LLDPE-g-PMMA, G-3) with poly(vinylidene fluoride)

1 Systematic name: poly(1,1-difluoroethylene).

(PVF₂) and the compatibilization of blends of LLDPE/PVF₂. The specific interaction between PMMA side chains and PVF₂ in G-3/PVF₂ binary blends is weaker than that between the homopolymers PMMA and PVF₂. There are two states of PVF₂ in the melt of a G-3/PVF₂ (60/40, w/w) blend, one as pure PVF₂ and the other interacting with PMMA side chains. The miscibility between PMMA side chains and PVF₂ affects the crystallization of PVF₂. LLDPE-g-PMMA was demonstrated to be a good compatibilizer in LLDPE/PVF₂ blends, improving the interfacial adhesion and dispersion in the latter. Diffusion of PMMA side chains into PVF₂ in the interfacial region reduces the crystallization rate and lowers the melting point (T_m) and the crystallization temperature (T_c) of PVF₂ in the blends.     

Mechanistic aspects of carbon dioxide reforming of methane to synthesis gas over Ni catalysts

A study of the kinetic isotope effect (CH₄/CO₂ CD₄/CO₂) for carbon dioxide reforming of methane to synthesis gas shows that an isotope effect exists with k_{CH 4}/k_{CD 4} ratio of 1.05–1.97, depending on reaction temperature and catalyst applied. The attainment of stable performance over Ni/La₂O₃ catalyst is found to be related to the strong chemisorption of CO₂, weak chemisorption of CH₄ and slow rate of CH_x formation, and fast rate for CH_x removal by oxidation.     

A vibrational study of the activation sequence of C–H and C–C bonds of isobutene and 1-butene on Mo(110) and (4 × 4)-C/Mo(110) surfaces

The thermal decomposition pathways of isobutene and 1-butene on both Mo(110) and 4 × 4-C/Mo(110) surfaces have been studied using high-resolution electron energy loss spectroscopy (HREELS) in order to highlight the substantially different activities of these two surfaces towards the cleavage of C–H and C–C bonds. On clean Mo(110), the CH₂ group of isobutene decomposes upon heating to 150 K, producing either a /-bonded isobutenylidene [(CH₃)₂CCH] species or a 1,1-di-/-bonded isobutenyl [(CH₃)₂CC] species. Upon further heating, extensive C–H bond scission occurs to form hydrocarbon fragments which do not contain CH₃ or CH₂ groups, but appear to have largely intact carbon skeletons. By contrast, isobutene is molecularly adsorbed on the carbide-modified surface at 150 K. Further heating produces isobutylidyne [(CH₃)₂HCC] by 300 K, which subsequently decomposes via C–C bond scission to generate surface methyl groups. The different activation sequence of the C–H and C–C bonds of isobutene on clean and carbide-modified Mo(110) surfaces is also qualitatively confirmed by comparative studies of 1-butene on the two surfaces.     

Polyzwitterion-to-polyampholyte transition using pH-responsive cycloterpolymers of diallyldimethylammonium chloride, (N,N-diallylammonio)methanecarboxylate and sulfur dioxide

The cycloterpolymerizations of varying proportions of diallyldimethylammonium chloride (I) and N,N-Diallyl-N-carboethoxymethylammonium chloride (II) in the presence of sulfur dioxide afforded a series of cationic (+) polyelectrolytes (CPEs) (III) in excellent yields. CPEs, upon acidic hydrolysis of the ester functionalities of the repeating units of II, resulted in the formation of cationic/zwitterionic (+/±) polymers (IV). pH-responsive zwitterionic units of ammonioethanoate (NH⁺CH₂CO) (having unquenched valency of nitrogen) in IV was converted to its anionic counterparts (NCH₂CO) by treating with equivalent amount of NaOH to give cationic/anionic i.e., ampholytic (+/−) polymers (V) with a charge symmetry or asymmetry arising out of either excess of cationic or anionic centers. The transformations of III to IV to V have thus provided an opportunity to study the effects of the polyelectrolyte-to-polyzwitterion-to-polyampholyte transitions on the solution properties of these polymers. Basicity constants of the carboxylate group (NH⁺CH₂CO) in IV as well as the amine group (NCH₂CO) in V were found to be “apparent” and as such follow the modified Henderson–Hasselbalch equation. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effects of low and high molecular mass PEG incorporation into different types of poly(ether-<Emphasis Type="Italic">b</Emphasis>-amide) copolymers on the permeation properties of CO<Subscript>2</Subscript> and CH<Subscript>4</Subscript>

Blend membranes were prepared by incorporating two types of polyethylene glycol (PEG) (molecular masses of 400 and 1000 g mol^?1) into three grades of poly(ether-block-amide) (PEBAX), namely PEBAX 1074, PEBAX 1657, and PEBAX 2533. The PEGs, which were used as blending agents, were employed at mass fractions ranging from 10 to 40 wt.% based on the mass of PEBAX. The gas separation performance of each neat or blend membrane, comprising its CO₂ and CH₄ permeabilities and its ideal CO₂/CH₄ selectivity, was studied at room temperature (25 °C) and at pressures of 2–8 bar. X-ray diffraction (XRD) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) analyses were used to determine the crystallinities of and the chemical bonds in the prepared membranes, respectively. Scanning electron microscopy (SEM) was also utilized to observe the morphologies of the membranes. The results obtained from experimental investigations showed that the incorporation of low molecular mass PEG significantly increased the permeability but only slightly affected the ideal CO₂/CH₄ selectivity, while the incorporation of high molecular mass PEG decreased the permeability considerably but sharply increased the ideal CO₂/CH₄ selectivity. This behavior intensified as the polyether content of the PEBAX was decreased.

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