SYNTHESIS OF DBN AND ITS CATALYTIC PERFORMANCE FOR METHANOL CARBONYLATION TO METHYL FORMATE

1 , 5-diazabicyclo['1, 3, 0]non-5-ene(DBN) has been synthesized in our laboratory, and its catalytic activity and selectivity for methanol carbonylation to methyl formate (MF) have been studied. The experimental results have demonstrated that the synthetic processes of DBN used for the present work are reasonable and feasible. The total yield of three steps of DBN synthsis is approximate to 80%. The activity evaluation has shown that DBN can effectively catalyze the carbonylation reaction of methanol in the presence of propylene oxide (PO) promoter. PO-promoted DBN is a novel catalytic system superior to sodium methoxide.     

Synthesis and characterization of new epoxy and cyanate ester resins

New epoxide and cyanate ester resins with an aromatic ester backbone namely 1,3-[di-(4-glycidyloxy diphenyl-2,2^′-propane)]-isophthalate (DGDPI) and 1,4-[di-(4-cyanato diphenyl-2,2^′-propane)]-terephthalate (DCDPT) were synthesized and the intermediates were characterized by IR, 1H-/¹³C-NMR spectroscopic methods. The cured products from DGDPI and DHDPI exhibited higher T_g compared with standard epoxy system. The increase in the T_g may be due to the cyanate ester and rigid aromatic backbones present in the curing system.     

Simple preparation of polymer supported IBX esters and amides and their oxidative properties

Novel polymer supported IBX esters and amides were prepared in two steps, which were the coupling of 2-iodobenzoic acid to a hydroxy or amino polystyrene followed by activation of the intermediate product. These polymer supported reagents were tested as oxidants by the conversion of a series of alcohols to the corresponding aldehydes or ketones. We found that the polymer supported IBX amides displayed excellent oxidative activity, in that they oxidized benzyl alcohol to benzaldehyde completely within 1 h at an oxidant to alcohol ratio of 2 to 1.     

Retention,enantioselectivity and enantiomeric elution order of propranolol and its ester derivatives on an alpha1-acid glycoprotein-bonded column

Summary The retention, enantionselectivity and enantiomeric elution order of racemic propranolol (PP) and its ester derivatives (O-acetyl,-propionyl,-butyrul and-valeryl PP) on an ₁-acid glycoprotein (AGP)-bonded column have been investigated by changing eluent composition (eluent pH, buffer concentration, type and content of organic modifier). The retention of these cationic solutes, PP and its ester derivatives, was influenced by eluent pH, ionic strength and organic modifier content. The enantioselectivity was dependent on eluent pH and type of organic modifier. Reversal of the enantiomeric elution order of ester derivatives of PP (O-propionyl-butyryl) and-valeryl PP) occurred around eluent pH 6–7. These results suggst that chiral recognition or binding properties may be altered by the change in eluent composition, espeically eluent pH and type of organic modifier.     

Synthesis of 1-oxa-2-silacyclopentane derivatives via intramolecular nucleophilic attack at silicon

Metalation of (HSiMe₂)₃CH with lithium diisopropylamide (LDA) in THF gives (HSiMe₂)₃CLi, which reacts with ethylene oxide, propylene oxide, 1,2-epoxy butane, 1,2-epoxy pentane, 1,2-epoxy hexane, and epichlorohydrin to give the corresponding 1-oxa-2-silacyclopentane derivatives. Then, glycidylmethacrylate (GM) random copolymers with styrene (St) (in a 1:1 and 1:3 mol ratio) were synthesized by solution free radical polymerization at 70(±1) °C using α,α′-azobis(isobutyronitrile) (AIBN) as an initiator. Both types of copolymers were treated with (HSiMe₂)₃CLi to give new modified copolymers. The reaction of (HSiMe₂)₃CLi with epoxides on the side chains of the copolymers does not lead to intramolecular nucleophilic attack contrary to simple epoxides. All the products have been characterized by spectroscopic techniques.     

A temperature study on critical micellization concentration (CMC), solubility, and degree of counterion binding of α-sulfonatomyristic acid methyl ester in water by electroconductivity measurements

 For a sodium salt of α-sulfonatomyristic acid methyl ester (14SFNa), one of the α-SFMe series surfactants, critical micellization concentration (CMC), solubility and degree of counterion binding (β) were determined by means of electrocon-ductivity measurements at different temperatures (at every 5 °C) ranging from 15 to 50 °C. The phase diagram of 14SFNa in pure water was constructed from the CMC- and solubility-temperature data, in which the Krafft temperature (critical solution temperature) was found around 0 °C. The changes in the Gibbs energy, ΔG ⁰ _m, enthalpy, ΔH ⁰ _m, and entropy, ΔS ⁰ _m, upon micelle formation as a function of temperature were evaluated taking βvalues into calculation. Received: 28 August 1996 Accepted: 5 November 1996     

Rapid transacylations of activated ester substrates bound to the primary side β-cyclodextrin-cyclen conjugate and its M2+ complexes

The ability of cyclodextrins to effect rapid transacylations of bound substrates has been well studied. One important difference between cyclodextrin and enzyme-mediated transacylation is the pH required. Because the pK _a of a cyclodextrin secondary-side hydroxyl group is about 12, transacylations are accelerated in the presence of cyclodextrin under basic conditions (pH > 10.5). In 1988, our group reported the synthesis of cyclodextrin with attached cyclen-Co(III) complexes; significant acceleration in the reaction withp-nitrophenyl acetate was observed only with the primary side derivative. Of course, metalloenzymes utilize M²⁺ and not M³⁺ catalytic centers; in addition, large rate accelerations in the transacylations of both activated and unactivated substrates have been observed previously in systems utilizing M²⁺ ions (e.g., Zn, Cu, Ni) as well as M³⁺ ions (e.g. Co, Ir, Cr). In this paper, we describe the ability of CD-cyclen-M²⁺ conjugates to transacylate activated esters, amides, and phosphates. In addition, the ability of the apoenzyme mimic to effect transacylations was examined.     

Redox Transformation of Adducts from Cycloaddition of Diazoacetic Ester to β-Arylacryloyloxiranes

It was established that, in addition to ethyl 4-aryl-3-(2,3-epoxyalkanoyl)-4,5-dihydro-1H-pyrazole-5-carboxylates, the reaction of diazoacetic ester with β-arylacryloyloxiranes also gives ethyl 4-aryl-3(5)-(3-hydroxy-2-methylalkanoyl)-1H-pyrazole-5(3)-carboxylates. The latter are formed from the tautomeric ethyl 4-aryl-5-(2,3-epoxyalkanoyl)-4,5-dihydro-1H-pyrazole-3-carboxylates as a result of intramolecular oxidative-reductive disproportionation. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, 1150–1160, August, 2005.     

Chemical Constituents from the Root of Antidesma Pentandrum var. Barbatum

Investigation of the root extract of Antidesma pentandrum var. barbatum led to the isolation of seven new compounds, antidesmol ( 1 ), antidesmanins E ( 2 ) and F ( 3 ), antidesnone ( 4 ), antidesnol ( 5 ), barbatumols A ( 6 ) and B ( 7 ), together with 14 known compounds including sodium aristolochate‐I ( 10 ) and aristolochic acid‐I methyl ester ( 11 ).     

Oxidation of methyl phenyl sulfide with hydrogen peroxide catalyzed by Ti(IV)-substituted heteropolytungstate

Alkylammonium salts of Ti(IV)-substituted heteropolytungstate, PW₁₁TiO ₁₀ ⁵⁻ , catalyze the oxidation of methyl phenyl sulfide with hydrogen peroxide. The yield of the corresponding sulfoxide and sulfone is practically quantitative. A³¹P NMR study confirms the formation and reactivity of the PW₁₁O₃₉TiO ₂ ⁵⁻ peroxo complex in organic media.