Fatty acid vinyl esters as acylating agents: A new method for the enzymatic synthesis of monoacylglycerols

Lipase-catalyzed synthesis of monoacylglycerols (MAG) was performed by transesterification reactions between fatty acid vinyl esters and either glycerol (1) or 1,2-O-isopropylidene-rac-glycerol (2), without solvents or in the presence ofn-pentane. Vinyl decanoate, vinyl laurate, vinyl stearate and vinyl palmitate have been converted to the corresponding monoacylglycerols. As expected for the reaction with1, a mixture of mono-, di- and triacylglycerols was synthesized. The highest concentrations of MAG were achieved with vinyl stearate (30% 2-MAG and 15% 1-MAG). The reactions of fatty acid vinyl esters with the protected glycerol (2) led to the corresponding protected 3-monoacylglycerols with 100% conversion after short reaction times. The subsequent cleavage of these acetonides was performed by four different methods. The fastest cleavage was found with trifluoroacetic acid as catalyst, whereas the highest concentration of MAG (100%) was obtained for the boric acid-catalyzed hydrolysis of the acetonides.     

Synthesis and Characterization of Zinc(II) Oxide Nanoparticles by Thermal Decomposition of Two Zinc(II) Nitrite Coordination Polymer Precursors

Two zinc(II) coordination polymers, {[Zn(3-bpdb)(NO₂)]·0.5H₂O} _n (1) and [Zn(4-bpdb)(NO₂)₂] _n (2), 3-bpdb = 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene and 4-bpdb = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene}, have been synthesized and characterized by elemental analyses and IR spectroscopy. Nanoparticles of zinc(II) oxide have been prepared by thermolyses of two different zinc(II) coordination polymers, 1–2. The nano-materials were characterized by scanning electron microscopy, X-ray powder diffraction and IR spectroscopy. The thermal stability of ZnO nano-particles was studied by thermal gravimetric and differential thermal analysis and showed that there is no loss of weight, which indicates that the products were zinc(II) oxide. This study demonstrates the coordination polymers may be suitable precursors for the preparation of nanoscale materials.     

Ab initio investigations of the equilibria between trichlorothioacetyl chloride,tetrachlorothiirane, and trichloroethenesulfenyl chloride,their reactants and decomposition products

Trichlorothioacetyl chloride (1), tetrachlorothiirane (2), and trichloroethenesulfenyl chloride (3) and the equilibria between them have been investigated by ab initio Hartree–Fock (HF), Møller–Plesset second order perturbation (MP2) calculations, and by Gaussian-3 theory, G3 (MP2). Transition states of the isomerization reactions have been identified. Also investigated were possible reactions leading to the isomers and their possible decomposition products. The results show that the unobserved isomerization reactions are feasible.     

Liquid-Liquid Extraction of Antimony (III) with Mesityl Oxide

Abstract

Mesityl oxide [(CH₃)₂C[dbnd]CHCOCH₃] was used for the liquid-liquid extraction of antimony. It can be quantitatively extracted from 3 M hydrochloric acid within 10 sec of equilibration with 15 ml of mesityl oxide. The metal from the organic phase was stripped with 10 ml of water and was determined photometrically as its iodide complex at 425 mm. The probable composition of the extractable species at 3 M hydrochloric acid was either SbCl₃ · 3MeO or [HSbCl⁴ (MeO)₃] where MeO is mesityl oxide. The method is simple, rapid, and selective, as it was possible to separate antimony from a large number of elements which are associated with it in alloys and minerals. The method is applicable for the analysis of antimony in solder. The standard deviation is ± 1%.     

Structures,absolute configurations,and syntheses of volatile signals from three sympatric ant-lion species,Euroleon nostras,Grocus bore,andMyrmeleon formicarius (Neuroptera: Myrmeleontidae)

The thoracic gland of the ant-lionEuroleon nostras was found to contain nerol oxide (1a) and (Z)-6-undecen-2-ol (nostrenol,3) while the speciesGrocus bore contained 10-homonerol oxide (1b) and nostrenol (3). Nerol (2a) and 10-homonerol (2b) were found in a third species,Myrmeleon formicarius. 10-Homonerol, racemic 10-homonerol oxide, and racemic as well as (R)- and (S)-nostrenol were synthesized. The nerol oxide ofE. nostras and the 10-homonerol oxide ofG. bore were found to be racemic, while both species contained optically pure (R)-nostrenol (28).Visiting research scientists from Institute of Photographic Chemistry, Academia Sinica, Beijing, China (H. H.-Z.) and Shanghai Institute of Organic Chemistry, Academia Sinica, 345 Ling Lu, Shanghai, China (L. G.-Q.).     

Disproportionation of Toluene on Monoliths Washcoated with Metal Oxide Modified ZSM5

Abstract  

Monoliths washcoated with ZSM5 and metal oxide (MgO, CaO, La₂O₃ or CeO₂) modified ZSM5 were prepared, characterized and studied for toluene disproportionation. An improvement in the yield of the desired p-xylene isomer was obtained by using monoliths coated with metal oxide-modified ZSM5. The enhancement in p-xylene yield depended on the type of modifier, metal loading and the washcoat thickness on the monolith. The 10% LaZSM5 coated monolith having an average washcoat thickness of 23 μm showed the highest p-xylene yield.     

Microbial synthesis of chiral intermediates for β-3-receptor agonists

Chiral intermediates were prepared by biocatalytic processes for the chemical synthesis of β-3-receptor agonists. These include: (i) the microbial reduction of 4-benzyloxy-3-methanesulfonylamino-2′-bromoacetophenone 1 to the corresponding (R)-alcohol 2 by Spingomonas paucimobilis SC 16113. In the biotransformation process, a reaction yield of >85% and an optical purity of 99.5% were obtained for the desired (R)-alcohol 2; (ii) the enzymatic resolution of racemic α-methyl phenylalanine amide, 3, and α-methyl-4-hydroxy-phenylalanine amide, 5, by amidase from Mycobacterium neoaurum ATCC 25795 to prepare the corresponding (S)-amino acids 4 and 6. Reaction yields of 49.9 and 49 M% (theoretical maximum yield 50 M%) and optical purities of 99 and 94% were obtained for the desired (S)-amino acids 4 and 6, respectively; (iii) the asymmetric hydrolysis of methyl-(4-methoxyphenyl)-propanedioic acid, ethyl diester, 7, to the corresponding (S)-monoester 8 by pig liver esterase. A reaction yield of 96 M% and an optical purity of 96% were obtained for (S)-monoester 8 when reactions were carried out in a biphasic system containing 10% ethanol at 10°C.     

Two-component,one-pot synthesis of pyrimido[1,2-b] [1,2,4,5]tetrazines

Derivatives containing the cyclohepta4′,5′thieno[2′,3′:4,5]pyrimido[1,2-b][1,2,4,5]-tetrazin-6-one system were prepared from the reaction of 3-amino-2-thioxo-1,2,3,5,6,7,8,9-octahydro-4H-cyclohepta[4,5]thieno[2,3-d]pyrimidin-4-one (5) or its 2-methylthio derivative 6 with hydrazonoyl chlorides 9. The mechanism of the studied reactions has been discussed and the biological activity of the isolated products has been evaluated.     

Addition of alkyllithiums to 3H-quinazoline-4-thione and various substituted quinazoline derivatives; application in synthesis

Reaction of 3H-quinazoline-4-thione (1) with two mole equivalents of an alkyllithium (t-BuLi, n-BuLi or MeLi) at?78 ^°C in dry THF gave the corresponding 2-alkyl-1,2-dihydro-3H-quinazoline-4-thione (4, 5 or 6) in high yield. Similarly, reactions of 4-(methylthio)quinazoline (7), 4-(ethylthio)quinazoline (8) and 4-methoxyquinazoline (9) with alkyllithiums (one mole equivalent) gave the corresponding 4-substitued 2-alkyl-1,2-dihydroquinazolines 11–18. On the other hand, blocking position 2 with a phenyl group in 4-(methylthio)-2-phenylquinazoline (20) and 4-methoxy-2-phenylquinazoline (21) resulted in reaction with two mole equivalents of alkyllithiums to give 4,4-dialkyl-2-phenyl-3,4-dihydroquinazolines 22–24.     

Novel carbonaceous coupling products containing sulphur

Summary The coupling of alkali ethynides with CSCl₂, SOCl₂, or SO₂Cl₂ results in new carbonaceous polymeric products; their structures were studied by FTIR and XPS spectra, and the assumptions on reaction mechanism were made with respect to the found elemental composition and model calculations. These macromolecular products, obtained in the yields of 80–92%, contain chlorine in the chain terminals, and alkyne sequences along with inserted C=S, S=O or SO₂ groups. These inserted sulphur groups contribute to the stability of alkyne sequences as evidenced by FTIR spectra. Soluble thioketone iPr₃SiC≡C–CS–C≡CSiiPr₃ (2) prepared by similar coupling of iPr₃SiC≡CLi (1) with CSCl₂ in the yield of 72%, was considered as a support of the suggested coupling mechanism. Similarly monomolecular sulfoxide iPr₃SiC≡C–SO–C≡CSiiPr₃ (3) was prepared by coupling of iPr₃SiC≡CLi (1) with SOCl₂ in the yield 75%.     

Selective Oxidation of Propylene to Propylene Oxide by Molecular Oxygen over Ti-Al-HMS Catalysts

Ti- and Al-containing hexagonal mesoporous silicas (HMS) were synthesized at ambient temperature using dodecylamine as surfactant, and the resultant compounds were used as catalysts for the oxidation of propylene by molecular oxygen. Ti-Al-HMS, which was prepared by reaction of Ti(iso-OC₃H₇)₄, Al(iso-OC₃H₇)₃ and SiOC₂H₅)₄ in an alcohol-aqueous solution in the presence of dodecylamine, showed 47.8 of conversion and 30.6 of selectivity for propylene oxide (PO) at 523K. The yield of PO over Ti-Al-HMS (14.6) was much higher than those over Ti-HMS (1.3) and Al-HMS (0.9) at the same reaction conditions. Ti-Al-HMS was also found to be more effective for PO formation than the supported catalysts (Ti/Al-HMS and Al/Ti-HMS) prepared by impregnation method. These results indicated that the simultaneous existence of Ti and Al in HMS was very important for improving the yield of PO from the oxidation of propylene, and the synthesis method influenced the catalytic activity of the Ti- and Al-containing HMS catalysts.     

Homogenous and Heterogeneous Catalytic Activity of Azo-Linked Schiff Base Complexes of Mn(II), Cu(II) and Co(II)

Abstract  

Azo linked Schiff-base[L] complexes of Mn(II)(1), Cu(II)(2) and Co(II)(3) obtained by template method, in the reaction of 4-(benzeneazo) salicylaldehyde with 1,2-propanediamine in the present of metal acetate, respectively. Complexes are used as catalyst for oxidation of cyclohexene with tert-butylhydroperoxide (TBHP); oxidation of cyclohexene catalyzed by these complexes gave 2-cyclohexene-1-one and 2-cyclohexene-1-ol as major products. Conversion of cyclohexene achieved was 95–100% with (1), (2) and (3), with selectivity of 57, 92 and 100% for 2-cyclohexene-1-one, respectively. The encapsulated Cu(II) complex (Cu–NaY) catalyzes the oxidation of cyclohexene using TBHP as oxidant in good yield. (Cu–NaY) under optimized reaction condition gave three reaction products. A maximum of 100% conversion of cyclohexene has been achieved where selectivity of 2-cyclohexene-1-one was 83%.     

Calcium-mediated hydrophosphination of diphenylethyne and diphenylbutadiyne as well as crystal structure of 1,4-diphenyl-1,4-bis(diphenylphosphanyl)buta-1,3-diene

Hydrophosphination reactions of phenyl substituted alkynes are catalyzed effectively by [(thf)₄Ca(PPh₂)₂] (1). The reactions of diphenylethyne and diphenylbutadiyne with diphenylphosphane in THF in the presence of catalytic amounts of 1 (approx. 5 mol%) yield quantitatively the cis-addition products trans-1,2-diphenyl-1-diphenylphosphanylethene (2) and 1,4-diphenyl-1,4-bis(diphenylphosphanyl)buta-1,3-diene (3), respectively. The phenyl groups in 3 are oriented nearly perpendicular to the butadiene backbone and therefore, the π-systems of the phenyl groups and the butadiene unit show no interaction with each other.     

Insoluble Lignin Models (4): Condensation Reactions of a Polymer-Bound Guaiacylpropanol Model

The reactions of syringyl alcohol with itself and with either a soluble phenol, 3-methoxy-4-hydroxyphenylpropane (guaiacylpropane, 13) or an insoluble polymer-bound phenol, guaiacylpropanol (14)¹, led to dimeric products. The low (11%), but significant yield of C5-Cα dimer 16 in the reaction of polymer-bound phenol with syringyl alcohol suggests that soluble lignin units are able to condense with insoluble lignin gels during the course of soda pulping. The yield of the C5-Cα dimer 15 in the soluble system was four times greater than that of the analogous heterogeneous dimer 16. Reactions of the polymer model 14 were not mass transfer limited.     

Supermicroporous Niobium Oxide as an Acid Catalyst

Supermicroporous (1.5–2.5 nm pore diameter) niobium oxide is synthesized using a nonionic block copolymer as a structural directing reagent, which is removed by water washing after aging. The oxide contains water in the bulk material in the form of a water-rich niobium oxide. The supermicroporous niobium oxide is applicable for various acid-catalyzed reactions.     

Reaction of mono-epoxidized conjugated linoleic acid ester with boron trifluoride etherate complex

The reaction of methyl 11, 12-E-epoxy-9Z-octadecenoate (1) with boron trifluoride etherate furnished a mixture of methyl 12-oxo-10E-octadecenoate (3a) and methyl 11-oxo-9E-octadecenoate (3b) in 66% yield. Methyl 9, 10-Z-epoxy-11 E-octadecenoate (2) with boron trifluoride etherate furnished a mixture of methyl 9-oxo-10 E-octadecenoate (4a, 45%) and methyl 10-oxo-11 E-octadecenoate (4b, 19%). A plausible mechanism is proposed for these reactions, which involves the attack on the epoxy ring system by BF₃, followed by deprotonation, oxo formation, and double bond migration to give a mixture of two positional α,β-unsaturated C₁₈ enone ester derivatives (3a/3b, 4a/4b). The structures of these C₁₈ enone ester derivatives (3a/3b, 4a/4b) were identified by a combination of NMR spectroscopic and mass spectrometric analyses.     

Thulium Oxide Nanopowders Obtained by Precipitation

The aim of this work was to investigate the influence of precipitation parameters on the morphology of obtained thulium oxide powders. Tm₂O₃ precursor powders were synthesized by precipitation method using 0.1–0.25M water solutions of thulium nitrate and 1.5M ammonium hydrogen carbonate water solution as a precipitation agent. The processes were conducted at different temperatures (25–50°C). The result showed that the morphology of the obtained thulium oxide (Tm₂O₃) powders depends both on the molar concentration of thulium nitrate and the temperature of precipitation. Small, round, loosely agglomerated Tm₂O₃ nanoparticles were obtained after air calcination of precursor precipitated at room temperature with the use of 0.1M thulium nitrate solution.     

Synthesis and Surface Properties of Disodium Monoalkyl Diphenyl Oxide Disulfonate

Disodium monoalkyl diphenyl oxide disulfonates (MADS) with different carbon chains (C_n‐MADS, n = 8, 12, 16) were synthesized through the steps of alkylation‐sulfonation‐neutralization using fatty alcohols (C₈, C₁₂, C₁₆), diphenyl oxide and fuming sulfuric acid (20 % free SO₃) as reagents. The structures of the products were identified by infrared spectroscopy and electrospray ionization‐mass spectrometry. The surface properties, emulsification, wettability alteration and salinity and hardness tolerance of the products were systematically investigated. The results show that the critical micelle concentration (CMC) of C₈MADS, C₁₂MADS and C₁₆MADS are 7.24 × 10^?3, 1.49 × 10^?3 and 2.09 × 10^?4 mol/L. The surface tensions at the CMC (γ_CMC) of each product are 37.5, 38.9 and 46.8 mN/m. The negative logarithm of the surfactant concentration in the bulk phase required to produce a 20 mN/m reduction in the surface tension of the solvent (pC₂₀) increases with the increase in the alkyl chain length. The emulsifying ability of C₁₂‐MADS is better than C₈‐MADS and C₁₆‐MADS, and the MADS showed less oil‐wet nature. The salinity and hardness tolerance of MADS is much stronger than that of conventional surfactants.     

Pummerer reaction of 4,7-di-tert-butyl-3h,8h-1,2,5,6-dithiadiazocine 1-oxide; formation of 1,4-dithiins

The Pummerer reaction of 4,7-di-tert-butyl-3H,8H-1,2,5,6-dithiadiazocine 1-oxide (4a) with (CF₃CO)₂O in the presence of DBU has produced 2,5-di-tert-butyl-1,4-dithiin (5a) in 67% yield, whereas the reaction of 4a with (CF₃CO)₂O alone gave a 5:2 mixture of 5a and 2,6-di-tert-butyl-1,4-dithiin (5a′) in 61% yield.     

Antioxidant synergism between butylated hydroxyanisole and butylated hydroxytoluene

Decay of the 2,6-di-tert-butyl-4-methylphenoxy radical [butylated hydroxytoluene (BHT)-radical] in the presence of butylated hydroxyanisole (BHA) was investigated in 1,2-dimethoxyethane with or without triethylamine. BHT-radical was conveniently generated by dissociation of its unstable dimer in solution. The products were BHT, 3,3′-di-tert-butyl-5,5′-dimethoxy-2,2′-dihydroxybiphenyl (BHA-dimer), 2,6-di-tert-butyl-p-quinone methide (QM), 1,2-bis(3,5-di-tert-butyl-4-hydroxyphenyl)ethane, and 3,3′,5,5′-tetra-tert-butyl-4,4′-stilbenequinone. The reaction without added triethylamine gave larger quantities of the last two products and BHA (recovery), whereas the reaction with it provided larger quantities of the first two products. The marked difference in the product distribution can be accounted for by a series of reactions including reversible dehydrogenation of BHA with BHT-radical, which generates 2-tert-butyl-4-methoxyphenoxy radical (BHA-radical) and BHT, reversible dimerization of BHA-radical, which affords an intermediarybis(cyclohexadienone), and spontaneous and base-catalyzed prototropic rearrangement of the intermediate into BHA-dimer. Products of coupling between BHT-radical and BHA-radical were not obtained. BHA was found to undergo facile acid-catalyzed addition to QM, providing two isomericbis(hydroxyphenyl)methanes. The results help to elucidate the mechanism of antioxidant synergism between BHA and BHT and may suggest that the synergism can be affected by base or acid.