Some fatty acids having an O-heterocycle in their terminal positions. II. ω-(3-Coumarinyl)alkanoic acids and ω-(2-chromonyl)alkanoic acids

Some ω-3-coumarinyl)alkanoic acids 1a , n = 3-6 were synthesized by cyclization of corresponding ethyl o-formylphenyl alkanedioate 3 with DBU followed by hydrolysis. By a similar cyclization, some ω-(2-chromonyl)alkanoic acids 2a , n = 3-6 were also obtained from the cyclization of corresponding o-acetylphenyl ethyl alkanedioate 4 .     

Polymeric catalysis: Imidazoles grafted onto poly(vinylamine). I. Synthesis and grafting of imidazolylalkanoic acids

Some ω-(1-imidazolyl) and ω-[4(5)-imidazolyl]alkanoic acids were synthesized and grafted onto poly(vinylamine) with an amide bond. These water-soluble grafts were used to study the kinetics of the esterolysis of activated phenyl esters. The 1-substituted imidazoles were prepared by the reaction of the sodium salt of imidazole with the ethyl ω-bromoalkanoates. The 4(5)-substituted imidazoles were prepared from urocanic acid or 4(5)-hydroxymethylimidazole. The ω-(1-imidazolyl)alkanoic acids were grafted onto poly(vinylamine) via their acyl–guanidine derivatives; the 3-[4(5)-imidazolyl]propanoic acid was grafted with a water-soluble carbodiimide.     

Some fatty acids having an O-heterocycle in their terminal positions. I. ω-(3-Chromonyl)alkanoic acids

Some ω-(3-chromonyl)alkanoic acid derivatives, 1a and 2a , n = 4, 5; 3a, 4a and 5a , n = 2-6, were synthesized by cyclization of corresponding methyl ω-(2-hydroxybenzoyl)alkanoates 7b or ethyl ω-(2,4-dihydroxybenzoyl)alkanoates 8b with N,N-dimethylformamide-dimethyl acetal or acetic anhydride-DBU followed by hydrolysis.     

冠醚酮酸和烷酸的合成

本文介绍了在PPA存在下，由B15C5和DB18C6同过量的二羧酸发生酰化作用，得到酮酸1a～e和3a～c。再把所得相应的酮酸1a～e和3a～c利用黄鸣龙法制得4'-(ω－羧基多亚甲基)苯并-15-冠-5(2a～e)和4',4'(5')-二(ω-羧基多亚甲基)二苯并-18-冠-6(4a～c)等一系列ω-冠醚酮酸。     

Polymeric catalysis: Imidazoles grafted onto poly(vinylamine). II. Kinetics of the esterolysis of activated phenyl esters

In the previous paper, some ω-(1-imidazolyl) and ω-[4(5)-imidazolyl]alkanoic acids were synthesized and grafted onto poly(vinylamine). These water soluble catalysts of varying apolarity contain both hydrophobic and electrostatic binding sites for neutral and charged substrates. The influence of side chain length, percent graft, and the substitution in the imidazole ring are described. The grafts possessing the longer side chains and lesser apolar weight were more efficient catalysts than the grafts containing numerous short side chains and greater apolar weight. These grafts exhibited slower rates than poly[4(5)-vinylimidazole].     

Sulfur-containing carboxylic acids. Communication 3. Synthesis of β-(acetylthio)alkanoic acids amides

Conclusions Amides of -mercapto- or -(acetylthio)alkanoic acids were obtained by the reaction of -thiolactones or -(acetylthio)alkanoic acid chlorides with amines.For Communication 2, see [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 616–621, March, 1983.     

Synthesis of 13C—O-labelled tertiary alkanoic acids by the Koch-haaf-reaction

Good yields of tertiary alkanoic acids are obtained from the Koch-Haaf-synthesis even when only stoichiometric amounts of carbinol and HCOOH are used. This offers a new approach to ¹³CO-labelled tertiary alkanoic acids. - An excess of HCOOH is generally used in the Koch-Haaf-synthesis¹⁾ of carboxylic acids from carbinols and HCOOH in conc. H₂SO₄.     

Conjugate addition of nitroalkanes to dimethyl maleate. Regioselective formation of both monoesters of 2-alkylsuccinic acids

Diesters of (E)-2-alkylidenesuccinic acids obtained by conjugate addition of nitroalkanes to dimethyl maleate can be selectively monohydrolyzed at the more reactive carboxyl group to the corresponding half-ester. Alternatively, total hydrolysis to the diacid allows a subsequent selective methyl esterification of the alkanoic carboxyl group to give the other regioisomeric half-ester. 2-Alkylsuccinic monoesters can be finally obtained by catalytic hydrogenation of the unsaturated derivatives.     

Aroylnitrile oxide cyclizations. 2. Synthesis of (3-aroylisoxazol-5-yl)alkanoic acids

Intermolecular cyclization of 1,3-dipolar aroylnitrile oxides to terminal alkynols followed by phase transfer catalyzed oxidation provided a short, convenient route to several novel (3-aroylisoxazol-5-yl)alkanoic acids.     

Weak acids enhance halogen activation on atmospheric water's surfaces

We report that rates of I(2)(g) emissions, measured via cavity ring-down spectroscopy, during the heterogeneous ozonation of interfacial iodide: I(-)(surface, s) + O(3)(g) + H(+)(s) →→ I(2)(g), are enhanced several-fold, whereas those of IO·(g) are unaffected, by the presence of undissociated alkanoic acids on water. The amphiphilic weak carboxylic acids appear to promote I(2)(g) emissions by supplying the requisite interfacial protons H(+)(s) more efficiently than water itself, at pH values representative of submicrometer marine aerosol particles. We infer that the organic acids coating aerosol particles ejected from ocean's topmost films should enhance I(2)(g) production in marine boundary layers.     

Influence of the position of the substituent on the efficiency of lipase-mediated resolutions of 3-aryl alkanoic acids

Hydrolase-catalysed kinetic resolutions to provide enantioenriched α-substituted 3-aryl alkanoic acids are described. (S)-2-Methyl-3-phenylpropanoic acid (S)-1a was prepared in 96% ee by Pseudomonas fluorescens catalysed ester hydrolysis, while, Candida antarctica lipase B (immob) resolved the α-ethyl substituted 3-arylalkanoic acid (R)-1b in 82% ee. The influence of the position of the substituent relative to the ester site on the efficiency and enantioselectivity of the biotransformation is also explored; the same lipases were found to resolve both the α- and β-substituted alkanoic acids. Furthermore, the steric effect of substituents at the C2 stereogenic centre relative to that for their C3 substituted counterparts on the efficiency and stereoselectivity is discussed.     

Macrolactones built from the bis-3,4(indol-1-yl)maleimide scaffold

15, 16, and 17-Membered lactones based on the bis-3,4(indol-1-yl)maleimide framework were obtained using intramolecular esterification reaction starting from 3-(1-ω-carboxyalkyl-2,3-dihydroindol-1-yl)-4-(1-ω-hydroxyalkyl-2,3-dihydroindol-1-yl)-maleimides. 3,4-Dibromo-maleimide, ω-(2,3-dihydroindol-3-yl)alkanoic acids, and ω-(2,3-dihydroindol-3-yl)alkanoles were used as starting compounds. Substitution of Br for the substituted indolines followed by the intramolecular cyclization of O-silylated hydroxyl acids derivatives led to macrolactones that incorporated 4-(dihydroindol-1-yl)-3-(indol-1-yl)maleimide moieties. Indoline nuclei in these compounds were dehydrogenated by DDQ in refluxing toluene to give 15, 16 or 17-membered lactones 3-[(ω-3-carboxyalkylindol-1-yl)-4-(ω-hydroxyalkylindol-1-yl)maleimides. Quantum chemical calculations showed that the formation of macrolactones of smaller size (13-membered) corresponds to the higher Gibbs energy ΔG^# and correlates with the absence of the target reaction product.     

Separation of molecular constituents from a humic acid by solid-phase extraction following a transesterification reaction

A selective removal of humic constituents involved in ester groups was conducted by a boron trifluoride-methanol transesterification reaction after removal of structurally unbound lipids. An analytical separation of subfractions containing specific classes of compound liberated from the humic matrix simplifies their identification by gas chromatography-mass spectrometry. We compared the traditional liquid-liquid separation into phenolic and aliphatic fractions with the modern and versatile fractionation technique using solid-phase extraction (SPE) on aminopropyl-bonded phases. Our results showed that both methods ensured separation of the same compounds, such as di- and tri-hydroxyalkanoic acids, α-, β- and ω-hydroxy fatty acids, alkanoic acids, α,ω-alkanedioic acids, n-alkanols, phenolic acids and sterols. Moreover, the SPE method not only provided a larger recovery of compounds, but involved smaller sample and solvent requirements, and larger ease and rapidity of sample handling than the traditional liquid-liquid separation. The SPE method should be thus recommended in structural studies of natural organic matter.     

Two-carbon homologation of aldehydes via silyl ketene acetals. 2. Study of the stereochemical control in the formation of (E)-alkenoic acids.

The condensation of C,O,O-tris(trimethylsilyl)ketene acetal 1 with aldehydes 2 in the presence of catalytic amounts of mercuric iodide at room temperature affords syn and anti beta-trimethylsiloxy alpha-trimethylsilyl alkanoic acid silyl esters 3 in good yields. These new compounds gave, under acidic or basic conditions, E and (or) Z enoic acids 4. The paths for the formation of these alkenoic acids are discussed.     

4,5-Dihydro-5-thioxo-]H-tetrazoie-l-alkanoic and alkanesulfonic acids and their amide derivatives

Homologous 4,5-dihydro-5-thioxo-1H-tetrazole-l-alkanoic and alkanesulfonic acids were prepared by reaction of sodium azide with methyl (carboxyalkyl)- and (sulfoalkyl) carbamodithioates, respectively. 4,5-Dihydro-5-thioxo-1H-tetrazole-i-alkanamides were derived from the corresponding alkanoic acids by aminolysis of their acid chlorides or imidazolides. Analogous alkane-sulfonamides were synthesized by the reaction of methyl [[[(1,1-dimethylethyl) amino]sulfonyl]-alkyljcarbamodithioates with sodium azide followed by removal of the 1,1-dimethylethyl group with trifluoroacetic acid.     

Synthesis of (1H-pyrrol-2-ylsulfanyl)alkanoic acids

(1-Benzyl-1H-pyrrol-2-ylsulfanyl)acetic acid, 2- and 3-(1-benzyl-1H-pyrrol-2-ylsulfanyl)propionic acids, 1,1′-[1,4-phenylenebis(methylene)]bis[(1H-pyrrol-2-ylsulfanyl)acetic acid], and 1,1′-(hexane-1,6-diyl)bis-[(1H-pyrrol-2-ylsulfanyl)acetic acid] were synthesized for the first time by reactions of 1-benzyl-1H-pyrrole, 1,1′-[1,4-phenylenebis(methylene)]bis(1H-pyrrole), and 1,1′-(hexane-1,6-diyl)bis(1H-pyrrole) with thiourea, iodine, and the corresponding halogen-substituted alkanoic acids. 1-(4-Nitrophenyl)-1H-pyrrole failed to react with thiourea and iodine.     

High temperature kinetics of the thermal decomposition of the lower alkanoic acids

The thermal decomposition of propanoic acid dilute in argon has beenstudied in a single-pulse shock tube over the temperature range of 1100-1500 K and over the pressure range of 14-18 atm. The decomposition kinetics have been satisfactorily computer modelled by means of afree radical mechanism involving H and OH chains. Recent single-pulse shock tube product analyses of acetic acid decomposition have been computer modelled using a free radical mechanism for decarboxylation coupled to a unimolecular dehydration reaction. A comparison between the thermal decomposition kinetics of the C₁? C₃ alkanoic acids is made. The present studies do notprovide evidence for the participation of transition states involving a pentavalent carbon atom in the pyrolyses of the lower alkanoic acids.     

Supramolecular liquid crystals formed by hydrogen bonding between a benzocrown-bearing stilbazole and carboxylic acids

The mesomorphism of hydrogen bonded complexes formed between 4'-carboxybenzo-15-crown-5 stilbazolyl ester (CBCSE) as proton acceptor and carboxylic acids as proton donors is discussed. CBCSE is a monotropic mesogen, forming a nematic phase upon quench cooling. A total of 32 hydrogen bonded complexes has been studied. Hydrogen bonding with carboxylic acids stabilizes the nematic phase, and/or induces a smectic A (SmA) phase. CBCSE forms 1:1 complexes (molar ratio) with alkanoic acids (fatty acids) and 2:1 complexes with alkanedioic acids. None of these proton donors is a mesogen itself, but the hydrogen bonded complexes are. The influence of the chain or spacer length on the transition temperatures is discussed. Besides the homologous series of the alkanoic and alkanedioic acids, the following carboxylic acids were used in this study: diglycolic acid, pyridine-2,6-dicarboxylic acid, 4-dodecyloxybenzoic acid, 3,4-bis(dodecyloxy)benzoic acid, 2,3,4-tris(dodecyloxy)benzoic acid and 3,4,5-tris(dodecyloxy)benzoic acid, phthalic acid, isophthalic acid and terephthalic acid.     

Supramolecular liquid crystals formed by hydrogen bonding between a benzocrown-bearing stilbazole and carboxylic acids

The mesomorphism of hydrogen bonded complexes formed between 4'-carboxybenzo-15-crown-5 stilbazolyl ester (CBCSE) as proton acceptor and carboxylic acids as proton donors is discussed. CBCSE is a monotropic mesogen, forming a nematic phase upon quench cooling. A total of 32 hydrogen bonded complexes has been studied. Hydrogen bonding with carboxylic acids stabilizes the nematic phase, and/or induces a smectic A (SmA) phase. CBCSE forms 1:1 complexes (molar ratio) with alkanoic acids (fatty acids) and 2:1 complexes with alkanedioic acids. None of these proton donors is a mesogen itself, but the hydrogen bonded complexes are. The influence of the chain or spacer length on the transition temperatures is discussed. Besides the homologous series of the alkanoic and alkanedioic acids, the following carboxylic acids were used in this study: diglycolic acid, pyridine-2,6-dicarboxylic acid, 4-dodecyloxybenzoic acid, 3,4-bis(dodecyloxy)benzoic acid, 2,3,4-tris(dodecyloxy)benzoic acid and 3,4,5-tris(dodecyloxy)benzoic acid, phthalic acid, isophthalic acid and terephthalic acid.     

Evaporation rates and vapor pressures of the even-numbered C8-C18 monocarboxylic acids

Temperature-dependent vapor pressures of the even-numbered alkanoic monoacids from C8-C18 were measured using temperature-programmed desorption (TPD). In TPD, the evaporation rates from the samples are directly measured and the vapor pressures are subsequently determined from the Hertz-Knudsen equation. Our measurements indicate that the vapor pressures of the solid even-numbered alkanoic acids decrease monotonically with increasing carbon number by more than 6 orders of magnitude going from C8 to C18. The enthalpies of sublimation increase monotonically with carbon number, from approximately 110 to 205 kJ/mol. The liquid-phase vapor pressure was measured for oleic acid, a C18 alkenoic acid. Comparison to the estimated liquid-phase vapor pressure for the corresponding C18 alkanoic acid indicates that the liquid-phase vapor pressures of these two compounds are identical. Our measured solid-phase vapor pressures for the C14 and larger alkanoic acids are lower than in previous studies. We attribute these differences to the influence of residual solvent molecules on the previous measurements, which cause the measured vapor pressures to be too large.