Phenolation of (+)-Catechin with Mineral Acids. II. Identification of New Reaction Products

To investigate the reactions that occur in the flavanoid unit during the liquefaction of tannin in phenol, the phenolysis of (+)-catechin was studied using either H₂SO₄, HCl, or BF₃ 2H₂O as acid catalyst. In addition to 2-[3-(3,4-dihydroxyphenyl)-2-hydroxy-3-(4-hydroxyphenyl)propyl]-1,3,5-benzenetriol (1) and 2-[(3,4-dihydroxyphenyl)(4-hydroxyphenyl)methyl]-2,3-dihydro-4,6-benzofurandiol (3) that have been described previously, eight additional reaction products were isolated, four of which were compounds that have not been described previously. The novel compounds described here are: 2-[3-(3,4-dihydroxyphenyl)-2-hydroxy-3-(2-hydroxyphenyl)propyl]-1,3,5-benzenetriol (2), 2-[(3,4-dihydroxyphenyl)(2-hydroxyphenyl)methyl]-2,3-dihydro-4,6-benzofurandiol (4), 2-[(3,4-dihydroxyphenyl)(4-hydroxyphenyl)methyl]-2,3-dihydro-7-(4-hydroxyphenyl)methyl-4,6-benzofurandiol (5), and 2-(1,3,5-trihydroxyphenyl)methyl-3-(3,4-dihydroxyphenyl)-6-[(3,4-dihydroxyphenyl)(4-hydroxyphenyl)methyl]-2,3,5,6-tetrahydrobenzo[1,2-b:5,4-b′]-difuran-4-ol (6). The structures of these and other previously described products are consistent with opening of the pyran ring of catechin and reaction at C-2 by either the para or the ortho position of phenol. Additional products resulting from reaction between pyran ring cleavage products and catechin, and from reaction of cleavage products were found. Similar reactions would be expected to take place during the phenolysis of condensed tannins.     

Acetals and ethers. XII. Reaction Products of Prop-2-enal with 1,2- and 1,3-Diols

2-(Hydroxyalkoxyethyl)-substituted cyclic acetals ( 1; 2; 3a-3d; 4a-4d ), derivatives of 1, 3-dioxolane or 1, 3-dioxane have been obtained in a p-toluenesulphonic acid-catalysed reaction of prop-2-enal with an excess of ethylene, propylene-1, 2, trimethylene, or butylene-1, 3 glycol. Respective 2-vinyl-1, 3-dioxolanes or 2-vinyl-1, 3-dioxanes were the intermediate products. The products of the reaction involving propylene-1, 2 and butylene-1, 3 glycols were mixtures of cis- and trans-2, 4-disubstituted-1, 3-dioxolanes and cis- and trans-2, 4-disubstituted-1, 3-dioxanes. The structure of HOROCH₂CH₂- substituents at C-2 atom of 1, 3-dioxacyclane ring has been proved through 2, 4-dinitrophenylhydrazone derivatives of the corresponding aldehydes HOROCH₂CH₂CHO that, however, could not be isolated as individual compounds.     

Darstellung,Struktur und Reaktivität quartärer Ammoniumcellulosate

Tetraalkylammonium cellulosates were prepared by means of an exchange reaction between cellulose and tetraalkylammonium methoxides in anhydrous methanol and dimethylsulfoxide up to a degree of substitution of about 0,7 without chain degradation. The course of this reaction and the structure of the cellulosates in comparison to lithium and sodium cellulosate has been studied. The reaction rate and the equilibrium substitution decreased with increasing size of the cation in the methoxide. The distribution of the alcoholate groups in equilibrium at C-2, C-3 and C-6 of the glucopyranosyl unit in the cellulosates, which was investigated by methylation, hydrolysis of the methylcelluloses, and analysis of the methylglucoses by gas chromatography, was independent of the nature of the cation. Under the given reaction conditions the hydroxyl group at C-2 was more acidic than those at C-3 and C-6, while for the latter practically no difference was found. The tetraalkylammonium cellulosates are highly reactive intermediates for the preparation of cellulose derivatives. The reactivity of the cellulosates increased with increasing size of the cation, Li^⊕ < Na^⊕ < N(CH₃)₄^⊕ <[(CH₃)₃N? CH₂? C₆H₅]^⊕.     

Ringspaltung von 4-(4-Nitrophenylazo)-substituierten Pyrazolidin-3,5-dion – Derivaten zu α-(4-Nitrophenylhydrazono)semicarbaziden und Folgeprodukten

Ring Cleavage of 4-(4-Nitrophenylazo)-substituted Pyrazolidine-3,5-diones to α-(4-Nitrophenylhydrazono)semicarbazides with Consecutive Reactions The reaction of 1 and 2 with ammonia, methylamine and dimethylamine in aprotic solvents, e. g. diethyl ether, yields the compounds 3 – 8 which can exist in two isomeric forms (form a/b ). On conditions which are usually chosen for spectroscopic investigations only form a could be detected. Nevertheless, under the influence of bases like KOH or ammonia in water or alcohol these compounds are mainly converted to semicarbazides ( 11–15 ) which means that this reaction must run via form b . Those semicarbazides which are unsubstituted at the N-4 of their semicarbazide-moiety show great tendency to cyclize, thus forming the triazolederivatives 16–18 . In contrast to these products, in the case of the N-4-monomethylated semicarbazide 14 the six-membered heterocyclus 19 was obtained. In comparison with 1 and 2 , stable intermediates such as 3–8 in the reaction with 21 could not be isolated.     

Isomerization of methylcyclopentadiene dimers

A commercial mixture of methylcyclopentadiene dimers mainly consisting of four dimeric compounds with partial structures of 1-methyl- and 2-methylnorbornene, undergoes slow oxidation and isomerization when it is dissolved in CH₂Cl₂, CHCl₃ or CCl₄. Both reactions are simultaneous but independent of each other. Isomerization only concerns those isomers that contain in their structure a 2-methylnorbornene ring. The nature of the isomerization and the influence of different acid media is studied.     

Oxidative Kupplung CH-acider Verbindungen mit p-Phenylendiaminen. VI. 13C-NMR-Untersuchung der Tautomerie und des Substituenteneffektes 4-substituierter Pyrazolin-5-one

Oxidative Coupling of CH-acid Compounds with p-Phenylendiamines. VI. ¹³C-N.M.R. Study of Pyrazolin-5-on Tautomerism and the Effect of 4-Substituents The ¹³C-n.m.r. spectra of a series of 4-substituted 3-methyl-1-phenyl-pyrazolin-5-ones 1–26 have been recorded and assigned. Examination of the chemical shifts of the heterocyclic ring carbons C-3, C-4, C-5 and the 1-phenyl carbons C_ipso and C_ortho permits to determine the preferred tautomeric forms of the compounds. In polar solvents like DMSO the OH-form is dominant, sometimes besides a small component of the CH-form. In nonpolar solvents like CDCl₃ the CH-form is preferred at room temperature besides a small component of the NH-form. Cooling or addition of CH₃OH to the solution shifts the tautomeric equilibrium to a higher amount of the NH-form. The influence of 4-substituents on the C-3, C-4 and C-5 chemical shifts have been compared with the effect of these substituents on the C_ipso and C_ortho carbons in benzene. A linear dependence between C-4 and C_ipso shows, that the effect of substituents in pyrazolin-5-ones and benzene is controlled by their electronegativity. The substituent effects are influenced remarkably by intermolecular hydrogen bondings to polar solvents and by intramolecular hydrogen bondings, if possible.     

Coal liquefaction by in-situ hydrogen generation.: 2. Zinc-water model compound reactions

Model compound studies were carried out to elucidate the reaction mechanisms taking place during the liquefaction of coal with the hydrogen produced from the reaction of zinc and water. In compounds of the type Ph-(CH₂)_n-Ph the splitting of the aliphatic bridge was easier with higher n values. Ether type compounds such as diphenylether were unreactive although the C-O bond in dibenzylether was easily cleaved. Condensed ring aromatic compounds gave low conversion with hydrogenation being facilitated by an increase in ring number. Phenolic compounds such as phenol did not react well, but the reactivity increased with increase in aromatic ring size. The cleavage of the aliphatic bridge was accelerated by the OH group, for example, in the case of 4-hydroxydiphenylmethane bond scission was about 15 times higher than that of diphenylmethane. Heterocyclic compounds were unreactive.     

The effects of catalysts in biodiesel production: A review

Biodiesel fuel has shown great promise as an alternative to petro-diesel fuel. Biodiesel production is widely conducted through transesterification reaction, catalyzed by homogeneous catalysts or heterogeneous catalysts. The most notable catalyst used in producing biodiesel is the homogeneous alkaline catalyst such as NaOH, KOH, CH₃ONa and CH₃OK. The choice of these catalysts is due to their higher kinetic reaction rates. However because of high cost of refined feedstocks and difficulties associated with use of homogeneous alkaline catalysts to transesterify low quality feedstocks for biodiesel production, development of various heterogeneous catalysts are now on the increase. Development of heterogeneous catalyst such as solid and enzymes catalysts could overcome most of the problems associated with homogeneous catalysts. Therefore this study critically analyzes the effects of different catalysts used for producing biodiesel using findings available in the open literature. Also, this critical review could allow identification of research areas to explore and improve the catalysts performance commonly employed in producing biodiesel fuel.     

Ultrasound-assisted synthesis of santalbic acid and a study of triacylglycerol species inSantalum album (Linn.) seed oil

Methyl ricinoleate (1) was treated with bromine and the dibromo derivative (2) was reacted with ethanolic KOH under ultrasonic irradiation to give 12-hydroxy-octadec-9-ynoic acid upon acidification with dil. HCl. The latter compound was methylated with BF₃/methanol to give methyl 12-hydroxy-octadec-9-ynoate (3). Compound3 was treated with methanesulfonyl chloride in the presence of triethylamine in CH₂Cl₂ to give methyl 12-mesyloxy-octadec-9-ynoate (4). Reaction of methyl 12-mesyloxy-octadec-9-ynoate with aqueous KOH under ultrasonic irradiation (20 kHz) gave (11E)-octadecen-9-ynoic acid (5, santalbic acid, 40%) and (11Z)-octadecen-9-ynoic acid (6, 60%) on acidification with dil. HCl. These isomers were separated by urea fractionation. The¹³C nuclear magnetic resonance (NMR) spectroscopic properties of the methyl ester and the triacylglycerol (TAG) esters of these enynoic fatty acid isomers were studied. The carbon shifts of the unsaturated carbon nuclei of the methyl ester of theE-isomer were unambiguously assigned as 88.547 (C-9), 79.287 (C-10), 109.760 (C-11), and 143.450 (C-12) ppm while the unsaturated carbon shifts of the (Z)-enynoate isomer appeared at 94.277 (C-9), 77.561 (C-10), 109.297 (C-11), and 142.668 (C-12) ppm. In the¹³C NMR spectral analysis of the TAG molecules of type AAA containing either the (Z)-or (E)-enyne fatty acid, the C-1 to C-6 carbon atoms on the α- and β-acyl positions were differentiated. The unsaturated carbon atoms in the α- and β-acyl chains were also resolved into two signals except that of the C-11 olefinic carbon. Sandal (Santalum album) wood seed oil (a source of santalbic acid) was separated by silica chromatography into three fractions. The least polar fraction (7.2 wt%) contained TAG which had a random distribution of saturated and unsaturated fatty acids, of which oleic acid (69%) was the predominant component. The second fraction (3.8 wt%) contained santalbic acid (58%) and oleic acid (28%) together with some other normal fatty acids. Santalbic acid in this fraction was found in both the α- and β-acyl positions of the glycerol “backbone”. The most polar fraction (89 wt%) consisted of TAG containing santalbic acid only. The distribution of the various fatty acids on the glycerol “backbone” was supported by the results from the¹³C NMR spectroscopic analysis.     

Fluorination Studies on Glycyrrhetic Acid Derivatives

Attempts to introduce a fluorine atom directly at the C-3 position of the triterpenoidal glycyrrhetic acid 1 by reacting the tosylate 2 with KF, or methyl glycyrrhetate 5 with Et₂NCF₂CHCIF, failed. The ring A olefin 3 and the rearrangement product 4 were obtained. The homoannular diene 7 was treated with NOF, but only nitroso-fluorine compounds 8, 9 were isolated. Nitrosyl fluoride was also reacted with olefin 3 . A difluoro compound 10 and the expected 2-keto-3α-fluoro compound 11 were obtained. The above two olefins were also reacted with bromine fluoride. Although the diene 7 gave only fluorine-free compounds 13, 14 , the expected fluoro-bromine compound 16 was obtained from 3 . When the 2β-fluoro-3α-bromo compound was treated with Bu₃SnH, the bromine atom was replaced by hydrogen and the 2β-fluoro compound 17 was formed.     

Synthesis of trisubstituted C18 pyrrole fatty ester derivatives

Reaction of methyl 10(11)-dicarbethoxymethyl-9,12-dioxooctadecanoate (1a,1b) with ammonium acetate furnished a mixture of positional isomers of a pyrrole derivative, methyl 9,12-imino-10(11)-dicarbethoxymethyl-9,11-octadecadienoate (2a,2b). Decarboxylation of the mixture of compounds 2a,2b with sodium carbonate in aqueous methanol yielded a mixture of compounds 3a,3b containing a CH₂COOCH₃ group at the 3- or 4-position of the pyrrole ring after esterification. Heating of the hydrolyzed mixture of compounds 3a,3b at 180°C for 1 h gave the desired trisubstituted pyrrole derivatives, methyl 9,12-imino-10(11)-methyl-9,11-octadecadienoate (4a,4b), containing a methyl group at the 3- or 4-position of the pyrrole nucleus. The structures of the products and intermediates were confirmed by infrared, and by¹H and¹³C nuclear magnetic resonance spectroscopy.     

A novel method for the introduction of a methyl group into the furan ring of a 2,5-disubstituted C18 furanoid fatty estervia a malonic acid function

Furan ring opening with benzohydroxamic acid of methyl 9,12-epoxy-9,11-octadecadienoate gave a mixture of positional isomers of conjugated methyl 3-phenyl-1,4,2-dioxazolyl C₁₈-enone esters 6a,6b. Michael addition of diethyl malonate anion to the conjugated enone system of 6a,6b furnished the corresponding malonyl intermediates 7a,7b, which upon removal of the dioxazole ring by hydrolysis gave methyl 10- and 11-dicarbethoxymethyl-9,12-dioxooctadecanoate 8a,8b. Cyclization of the latter gave the trisubstituted C₁₈ furanoid fatty esters 9a,9b, containing the malonate ester function at the 3-/4-position of the furan ring. Base hydrolysis of compounds 9a,9b gave the corresponding tricarboxylic acid derivatives 10a,10b, which were esterified to the trimethyl esters 11a,11b in BF₃/MeOH. When a mixture of 9a,9b was refluxed with Na₂CO₃/MeOH, hydrolysis of the malonate ester function was followed by decarboxylation to yield a-CH₂COOH substituent at the 3-/4-position of the furan ring (12a, 12b). Esterification of the latter with BF₃/MeOH gave the corresponding methyl diester derivatives 13a,13b. When a mixture of tricarboxylic acids 10a,10b was heated at 160–180°C for 6 hr, exhaustive decarboxylation of malonic acid function furnished a methyl group at the 3-/4-position of the furan nucleus. Esterification of the decarboxylated product gave a mixture of trisubstituted furanoid compounds 14a,14b (overall yield 28%). The procedure constitutes a novel method for the introduction of a methyl groupvia a malonic acid group to the 3-/4-position of the furan ring of a 2,5-disubstituted C₁₈ furanoid fatty ester.     

Synthesis, Characterization and Crystal Structure of a Novel One-Dimensional Supramolecular Dimethyltin (IV) Compound

A novel one-dimensional (1D) supramolecular dimethyltin compound of (Me₂SnO)₂(Me₂SnOCH₃)(O₂CCH₂SC₄H₃N₂-2,6)[Me₂Sn(O₂CCH₂SC₄H₃N₂-2,6)₂]·CH₃OH was prepared by the reaction of (CH₃)₂SnCl₂ with (2-pyrimidylthio)acetic acid with CH₃ONa as a base. The title compound contained four different tin atom environments. Among them, Sn(1) and Sn(2) were both five-coordinate with distorted trigonal bipyramidal geometries, Sn(3) was six-coordinate with a distorted octahedral geometry and Sn(4) was seven-coordinate with pentagonal bipyramidal geometry. Meanwhile, the compound was stabilized in a 1D infinite chain by intermolecular Sn–O bonds. An erratum to this article can be found at     

Synthesis of well-defined poly[(2-β-D-glucopyranosyloxy)ethyl acrylate] by atom transfer radical polymerization

The ‘living’ radical polymerization of 2-(2′,3′,4′,6′-tetra-O-acetyl-β-D -glucopyranosyloxy)ethyl acrylate (AcGEA) by atom transfer radical polymerization (ATRP) is reported. It has been found that the polymerization kinetics are first-order, the molecular weights increase linearly with conversion, and the molecular weight distribution remains narrow when the polymerization conversion is below 70%. Well-defined P(AcGEA) was obtained, and the O-protecting acetyl groups of P(AcGEA) were quantitatively removed by reacting with dilute CH₃ONa solution in CHCl₃/CH₃OH to afford well-defined poly[(2-β-D -glucopyranosyloxy)ethyl acrylate] (PGEA). © 1999 Society of Chemical Industry     

Anwendung von Ethoxyquin zur Qualitätserhaltung pflanzlicher Produkte

Application of Ethoxyquin for the Quality Preservation of Plant Products The use of the antioxidant ethoxyquin in plant products leads to ethoxyquin residues and many degradation and reaction products. The compound M₁, probably a primary reaction product, was identified as 1,1′,2,2′-tetrahydro-2,2,2′,2′,4,4′-hexamethyl-6,6′-diethoxy-1,8′-biquinoline by means of UV, IR and ¹H-NMR spectroscopy and by mass spectrometry. Two other degradation products were found to be oligomeric or polymeric compounds which, beside the ethoxyquin monomer, also contained structural elements formed by oxidative ring cleavage of the heterocycle. The predominating reaction, however, is the covalent binding of ethoxyquin to lignin. Regarding the mechanism of action of ethoxyquin, these studies have shown that ethoxyquin acts not only as a radical scavenger, but that it also binds oxygen by varying reactions.     

Novel oligonuclear ZnII4, ZnII8 and ZnII2NiII2 complexes with bis(benzoylacetone)-1,3-diiminopropan-2-ol

Reactions of bis(benzoylacetone)-1,3-diiminopropan-2-ol (abbreviated as H₃L) with zinc salts in the presence of triethylamine afforded the compounds [Zn₄(HL)₄]·4CH₃CN (1·4CH₃CN) and [Zn₈L₄(OH)₄]·2CH₃CN (2·2CH₃CN). Further reaction of 1 with Ni(CH₃COO)₂·4H₂O gave the heteronuclear species [Zn₂Ni₂(L)₂(CH₃O)₂(CH₃OH)₂] (3). The crystal structures of 1·4CH₃CN, 2·2CH₃CN and 3 were determined by the X-ray diffraction method.     

Hybridized 4-Trifluoromethyl-(1,2,3-triazol-1-yl)quinoline System: Synthesis,Photophysics, Selective DNA/HSA Bio-interactions and Molecular Docking

The synthesis, structural analysis, and evaluation of the photophysical properties of twelve novel 2-aryl(heteroaryl)-6-(4-alkyl(aryl)-1H-1,2,3-triazol-1-yl)-4-(trifluoromethyl)quinolines ( 6-8 ), where aryl(heteroaryl)=Ph, 4-Me-C₆H₄, 4-F-C₆H₄ and 2- furyl; 4-alkyl(aryl)=−CH₂OH, −(CH₂)₅CH₃ and Ph, are reported. Hybrid scaffolds 6 – 8 were synthesized at 77–95 % yields by regioselective copper-catalysed azide-alkyne cycloaddition (CuAAC) reaction of unpublished 6-azido-4-(trifluoromethyl)quinolines ( 2 ) with selected terminal alkynes ( 3 – 5 ). Azido intermediates 2 were obtained from the reaction of 6-amino-4-(trifluoromethyl)quinolines ( 1 ) and sodium azide at good yields (78–87 %). Compounds 6 – 8 were structurally fully characterized by ¹H−, ¹³C− and ¹⁹F− and ¹H−¹³C 2D-NMR (HSQC, HMBC) spectroscopy, X-ray diffraction (SC-XRD) and HRMS analysis. Moreover, the photophysical properties, DNA- and HSA-binding experiments (bio-interactions), and molecular docking studies for compounds 6 – 8 were performed. These are discussed and compared with similar compounds from recent research.     

Evaluation of Reaction Efficiency of Thioacidolysis for Cleavage of β-O-4 Interunitary Linkages by Using β-O-4 Type Artificial Lignin Polymer

Abstract

Dimeric lignin model compounds with non-phenolic and phenolic moieties and a β -O-4 type artificial lignin polymer were subjected to thioacidolysis to evaluate the reaction efficiency of thioacidolysis for cleavage of β -O-4 interunitary linkage. The obtained yields of thioethylated monomeric products from the dimeric lignin model compounds reached nearly 100% under the conventional condition, whereas that from the artificial lignin polymer was as low as 74%. Neither prolonged reaction time nor increased concentration of ethanethiol (the thioacidolysis reagent) enhanced the resulting monomer yields from the polymer (69–79%). Thioacidolysis of the lignin model compounds followed by HPSEC analysis also showed the dimeric model compounds were degraded almost quantitatively, but that the artificial lignin polymer was not. Thioacidolysis followed by desulfurization gave at least one dimeric product resulting from incomplete β -O-4 cleavage at significant yield. These results suggested the conventional thioacidolysis could not achieve quantitative cleavage of β -O-4 linkages in lignin macromolecules.     

A cis-directing effect towards diols by an exocyclic P-NHR moiety in cyclotriphosphazenes

Cyclophosphazenes containing the P-NHR moiety in an exocyclic spiro ring, N₃P₃Cl₄[NH(CH₂)₃O], (1), and N₃P₃Cl₄[NH(CH₂)₃NMe], (2), were used to investigate a possible directing effect of the P-NHR moiety on the formation of products in the nucleophilic substitution reactions with diols such as tetraethyleneglycol, 1,3-propanediol and 2,2-dimethyl-1,3-propanediol. The ³¹P NMR spectra of the reaction mixtures showed that only one kind of ansa product is formed in each of these reactions. X-ray crystallographic studies of the ansa products [(4a), (5a), (6a) and (7a)] have provided definitive proof of the cis-directing effect of the P-NHR moiety in cyclotriphosphazenes. It is likely that hydrogen-bond interaction between the incoming nucleophile and the P-NHR moiety of the reactant accounts for the preference for products with the substituents cis to the NH group.     

Metathesis ring opening polymerization of 5,6-dimethylenebicyclo[2.2.1]hept-2-ene

5,6-Dimethylenebicyclo[2.2.1]hept-2-ene ( I ) polymerizes in the presence of the two-component ring opening metathesis polymerization (ROMP) initiators WCl₆/(CH₃)4Sn and MoCl₅/(CH₃)4Sn. The product polymers were insoluble in all of many solvents investigated and are presumably cross-linked. The product polymers were investigated by IR and solid state ¹³C NMR spectroscopy, which established that the material consisted predominantly of poly(1,4-(2,3-dimethylene-cyclopentylene)vinylene) ( II ). A possible alternative route to II via thermal dehydrochlorination of poly(1,4-(2,3-bis(chloromethyl)cyclopentylene) vinylene) ( IV ) was also examined.