Spectrophotometric determination of the pH scale in ethane-1,2-diol

A highly selective method is described for the determination of gallium at the ppm-level in manganese nodules and geological reference samples. After dissolution of the sample, gallium is adsorbed on Dowex 1 (chloride form) from hydrochloric acid solution containing titanium trichloride, which reduces iron(III) so that it is not adsorbed. After elution with dilute nitric acid and evaporation, gallium is determined by atomic-absorption spectrometry with an air-acetylene flame.     

Studies in organic mass spectrometry—XI. The fragmentation of hop bitter acids derivatives having a five membered ring structure

The mass spectra of the hops derived humulinic acids, isohumulones and hulupones are discussed. The fragmentations are in accordance with those found for model compounds.     

1,2-Bis(methylamino)ethane-1,2-diol dihydrochloride as a new precursor of 1,2,1",2"-tetramethyl-3,3"-bidiaziridine

Using the synthesis of 1,2-bis(methylamino)ethane-1,2-diol dihydrochloride (5) as an example, it was demonstrated that aliphatic -aminocarbinols can be stabilized as hydrochlorides. The reaction of compound 5 with N-chloromethylamine in CHCl₃ in the presence of K₂CO₃ afforded 1,2,1",2"-tetramethyl-3,3"-bidiaziridine as a mixture of diastereomers (a racemate and a meso form). The meso form was isolated in the individual state and its structure was established by X-ray diffraction analysis. The kinetics of inversional epimerization was studied.     

Kinetics of the solvolysis of chloropentacyanocobaltate (III) ions in mixtures of ethane-1,2-diol or ethanonitrile with water

The kinetics of the solvolysis of [Co(CN)₅Cl]^3? ions have been investigated in mixtures formed by the addition of ethane-1,2-diol or ethanonitrile to water where the physical properties indicate little enhancement of structure in water-rich conditions. The effect on the kinetics of this solvolysis of this lack of structural change in the solvent shows in the linearity of the variation of log (rate constant) with the reciprocal of the dielectric constant for the addition of ethane-1,2-diol to water and the absence of any prominent extrema in the enthalpy or entropy of activation using either co-solvent. However, the effect of changes in solvation on the solvolysis with these two co-solvents appears to operate in a similar manner to the effects found when the hydrophobic co-solvent propan-2-ol is added to water. The application of a free energy cycle to the process of the initial state going to the transition state for this dissociative process suggests that, with both co-solvents, [Co(CN)₅]^2? in the transition state is more stable than [Co(CN)₅Cl]^3? in the initial state. © John Wiley & Sons, Inc.     

Novel synthesis of pyran,thiophene, and pyridine derivatives incorporating thiazole ring and their antitumor evaluation

This study aims to design and synthesize a number of novel pyran, thiophene, and pyridine derivatives incorporating thiazole ring and evaluate their antitumor inhibition (μM) as significant anticancer agents. The reactivity of compound 1 [2-(4-oxo-4,5-dihydrothiazol-2-yl)acetonitrile] towards different chemical reagents was described. Furthermore, the reactivity of all the newly synthesized products was evaluated. The most active compounds towards all the three tumor cancer cell lines used such as MCF-7 (breast adenocarcinoma), NCI-H460 (non-small cell lung cancer) and SF-268 (CNS cancer), and normal fibroblasts human cell line (WI-38) were compounds 6d , 8 , and 10b , which compared with the antiproliferative effects of the reference control doxorubicin. Also, some of the novel compounds indicate higher inhibition than doxorubicin against some of the cancer cell lines used such as 6c (especially towards MCF-7) and 2b , 6b (especially towards SF-268).     

cis-3,5-Cyclohexadiene-1,2-diol derivatives: facial selectivity in their Diels-Alder reactions with ethylenic, acetylenic and azo dienophiles

The Diels-Alder reactions of maleimide with the acetonide derivative (6a) of cis-3,5-cyclohexadiene-1,2-diol (1a) in various solvents showed facial selectivities ranging from 1 : 1 to 1 : 9. The same derivative 6a reacted in benzene with ethylenic dienophiles with generally modest facial selectivity, but acetylenic dienophiles added exclusively anti to the oxygen functions of 6a. Dimerization of cyclic acetals 6a and 7 was mainly, but for 6a not exclusively, by anti addition with respect to both the diene and the dienophile partners. Reactions of azo dienophiles with derivatives of 1a were predominantly by anti addition, but the diol itself (1a) gave the syn adduct as the major product.     

Oxidation by Permanganate in strong alkaline medium. Oxidation of ethane-1,2-diol,glycol aldehyde,glycollic acid,and glyoxylic acid

A study was made on the kinetics and mechanism of the reaction in aqueous solutions of 0.10 to 2.0 mol dm^?3 alkaline concentrations. The substrates (S) applied were ethane-1,2-diol (ethylene glycol), glycol aldehyde, glycollic acid, and glyoxylic acid. Glycol aldehyde and glyoxylic acid were present in the form of dihydrate. In each case alkoxy anion is the reactive form and the K_B constant of deprotonation can be calculated from the kinetic data. A mechanism based on electron abstraction is suggested. Manganate reacts with these substrates much slower than permanganate.     

1,2-Dimethyl-1,2-diphenyidisilane-1,2-diol and its K,Na, and FeII derivatives. Molecular structure of the all-trans-isomer, 2,3,5,6-tetra-methyl-2,3,5,6-tetraphenyl-1,4-dioxa-2,3,5,6-tetrasilacyclohexane

Hydrolysis of 1,2-dimethyl-1,2-diphenyl-1,2-dichlorodisilane yields 1,2-dimethyl-1,2diphenyldisilane-1,2-diol, which undergoes dimerization into stereoisomeric 2,3,5,6-tetramethyl-2,3,5,6-tetraphenyl-1,4-dioxa-2,3,5,6-tetrasilacyclohexanes under the action of H₂SO₄. Pure all-trans-isomer has been isolated and characterized by¹H NMR and IR spectroscopy and X-ray analysis. The reaction of sodium disilanediolate with FeBr₂ results in the formation of 1,2-dimethyl-1,2-diphenyl-4-ferra(ii)-3,5-dioxa-1,2-disilacyclopentane.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2550–2556, October, 1996.     

Kinetics and mechanism of the picolinic acid catalysed chromium(VI) oxidation of ethane-1,2-diol in the presence and absence of surfactants

The kinetics and mechanism of the Cr^VI oxidation of ethane-1,2-diol in the presence and absence of picolinic acid (PA) in aqueous acid media have been carried out under the conditions: [ethane-1,2-diol]_T [Cr^VI]_T and [PA]_T [Cr^VI]_T at different temperatures. The micellar effect on the title reactions has been studied in order to substantiate the suggested mechanism. Under the experimental conditions, ethane-1,2-diol is predominantly oxidised to hydroxyethanal and the kinetic contribution from the glycol splitting path is negligible. In the absence of PA, the simple alcohol oxidation mechanism, involving one —OH group, operates. In the PA-catalysed path, a Cr^VI–PA cyclic complex has been proposed as the active oxidant. In the PA-catalysed path, the Cr^VI–PA complex is the subject of nucleophilic attack by the substrate to form a ternary complex which subsequently experiences a redox decomposition (through 2e transfer) leading to hydroxyethanal and the Cr^IV–PA complex. The Cr^IV–PA complex then participates further in the oxidation of organic substrate and ultimately is converted into the inert Cr^III–PA complex. It is striking to note that the uncatalysed path shows a second-order dependence on [H⁺], while the PA-catalysed path shows a zeroth-order dependence on [H⁺]. Both the uncatalysed and PA-catalysed paths show first-order dependence on [ethane-1,2-diol]_T and on [Cr^VI]_T. The PA-catalysed path is first-order in [PA]_T. All these observations (i.e. dependence patterns on the reactants) remain unaltered in the presence of externally added surfactants. The effect of the cationic surfactant (i.e. cetylpyridinium chloride, CPC) and anionic surfactant (i.e. sodium dodecyl sulfate, SDS) has been studied both in the presence and absence of PA. CPC acts as an inhibitor and restricts the reaction to aqueous phase, while SDS acts as a catalyst and the reactions proceed simultaneously in both aqueous and micellar phase, with an enhanced rate in the micellar phase. The observed micellar effects have been explained by considering the preferential partitioning of the reactants between the micellar and aqueous phase. The applicability of different kinetic models, e.g. the Menger–Portnoy model, Piszkiewicz cooperative model, pseudo-phase ion exchange (PIE) model, has been tested to explain the observed micellar effects.     

Electronic structure and conformational flexibility of 1,2-dihydropyridine, 1,2- and 1,6-dihydropyrimidines,and their ylide derivatives

Molecular and electronic structures of 1,2-dihydropyridine, 1,2- and 1,6-dihydropyrimidine, and their oxo, imino, and methylene derivatives were studied by the semiempirical quantum-chemical AM1 method. In all compounds, the heterocycle exhibits a high conformational flexibility. The transition from a planar equilibrium conformation to a distorted sofa conformation with the =C-NH-C-C(N)= torsion angle of ±20° causes an increase in the energy by less than 1.7 kcal mol^–1. All molecules have similar -electronic structures, which, apparently, determines the similarity in their conformational behavior. The bending strain and the nonaromatic character of the cyclic -system are the factors that stabilize the nonplanar conformation of the ring in unsubstituted dihydroazines and ylide derivatives, respectively.Translated fromIzvestiva Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1934–1937, August, 1996.     

Influence of the heterocyclic side ring on orientation during nitrations of 1,2-alkylenedioxy-annelated benzenes and their mononitro derivatives

Nitration of 1,2-alkylenedioxybenzenes 1 furnished the respective nitro derivatives 3 and 4 in the relative ratios: 4a:3a /100:trace, 4b:3b /98:2.4, 4c:3c /86:14, 4e:3e /91:9 and 4f:3f /99:1.3. Nitration of 4 gave 5a:6a:8a /0:0:100, 5b:6b:8b /7.7:3.2:89, 5c:6c:8c /23:12:65, 5d:6d:8d /14:74:12, 5e:6e:8e /27:18:55 and 5f:6f:8f /23:7.0:70. Nitration of the isomeric 3 afforded the dinitro products 5, 6 and 7 in the following relative ratios: 5a:6a:7a /92:8:0, 5b:6b:7b /80:20:0, 5c:6c:7c /69:20:1 1, 5d:6d:7d /45:19:36, 5e:6e:7e /37:57:5.9 and 5f:6f:7f /64:36:0. Nitration of 3-nitro-1,2-dimethoxybenzene ( 9 ) furnished: 10:11 /63:37. Orientation as a function of the heterocyclic ring-size is discussed.     

1,1,4,4-Tetranitrobutane-2,3-diol and its derivatives. 3. Synthesis of 1,4-dichloro- and 1,4-dibromo-1,1,4,4-tetranitrobutane-2,3-diol dinitrates and their crystalline structure

1,4-Dichloro- (1) and 1,4-dibromo-1,1,4,4-tetranitrobutane-2,3-diol dinitrates (2) were synthesized by nitration of the corresponding diols with a mixture of trifluoroacetic anhydride and nitric acid. The x-ray diffraction investigations of 1 and 2 that have been carried out showed the influence of the intramolecular interactions of the nitro and nitrate groups on the packing of the molecules in the crystal.Institute of Chemical Physics, Russian Academy of Sciences, 142432 Chernogolovka. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 664–671, March, 1992.     

Deracemization of 1,2-diol monotosylate derivatives by a combination of enzymatic hydrolysis with the Mitsunobu inversion using polymer-bound triphenylphosphine

The deracemization of 1,2-diol monotosylate derivatives is achieved by the sequential combination of enzymatic hydrolysis and Mitsunobu inversion using a polymer-bound triphenylphosphine. After the lipase-catalysed hydrolysis of the racemic 2-acetoxyhexyl tosylate, the subsequent Mitsunobu reaction without separation causes an inversion of the resulting (R)-alcohol to give the (S)-enantiomer of the acetate as a single product. In particular, the reaction using the polymer-bound triphenylphosphine also proceeds smoothly, and the product is easily separated by filtration from the polymer-bound reagent and its by-products. This deracemization process is applicable to the preparation of several optically active 1,2-diol monotosylates.     

Gold-catalyzed tandem C-C and C-O bond formation: a highly diastereoselective formation of cyclohex-4-ene-1,2-diol derivatives

We have reported an efficient gold(I)-catalyzed tandem cyclization of tert-butyl carbonate derivatives of hex-1-en-5-yn-3-ol where nucleophilic participation of the O-Boc group appears to intercept a carbocationic (or cyclopropyl carbene) Au intermediate. This novel protocol leads to densely functionalized cyclohexene-3,4-diol derivatives where 1,2- or 1,2,3-stereocenters are controlled in a highly diastereoselective fashion.     

Synthesis and structure of some group VII 1,2-diacyl cyclopentadiene complexes and their pyridazine derivatives

A series of 1,2-diacyl cyclopentadienyl tricarbonyl manganese and rhenium complexes, [M(CO)₃{η⁵-1,2-C₅H₃(CO-(R)₂}] (3a–c and 4a–b), were isolated utilizing a straightforward, 3-step route. The synthetic pathway began with a 1,2-diacyl cyclopentadiene (fulvene), followed by the formation of its corresponding thallium salt and transmetallation with the appropriate pentacarbonyl metal bromide. X-ray crystallographic analysis and high-accuracy mass spectrometry confirmed the structures of the both the 4-methoxyphenyl and 4-chlorophenyl diacyl rhenium complexes, [Re(CO)₃{η⁵-1,2-C₅H₃(CO-(4-OCH₃)C₆H₄)₂}] (4a) and [Re(CO)₃{η⁵-1,2-C₅H₃(CO-(4-Cl)C₆H₄)₂}] (4b). Diacyl complexes 3a–c and 4a–b were then ring-closed with hydrazine hydrate to form their corresponding pyridazine complexes, [M(CO)₃{η⁵-1,2-C₅H₃(1,4-(R)₂N₂C₂}] (5a–c and 6a–b), in good yields (60–83%). The pyridazyl ligands were found to be relatively labile, and recrystallization of the target complexes 5a–c and 6a–b afforded only the free pyridazine ligands.     

Synthesis of stable derivatives of c(62): the first nonclassical fullerene incorporating a four-membered ring

A rational synthetic approach to the first four-membered ring-containing derivatives of C(62) is reported. They were synthesized by an inverse electron demand Diels-Alder reaction of 3,6-diaryl-1,2,4,5-tetrazines with C(60) in o-dichlorobenzene, followed by visible light irradiation at reflux. The structure of these nonclassical fullerenes derivatives was determined by X-ray single-crystal diffraction.     

Control of photoreactions of eight membered ring di- and trienones in a crystalline inclusion complex with optically active 1,6-DI(o-Chlorophenyl)-1,6-diphenylhexa-2,4-diyne-1,6-diol

By complexing with the title host compound, flipping equilibrium of cycloocta-2,4,6-trien-1-one was frozen in one optical conformer as a 2:1 complex, which upon irradiation gave optically active bicyclo [4.2.0] octa-4,7-dien-2-one. Irradiation of a 1:2 complex of cycloocta-2,4-dien-1-one and the same host compound gave an optically active dimer, anti-tricyclo [8.6.0.0^2,9] hexadeca-7, 11-diene-3, 16-dione.     

Isolation,evaluation of bioactivity and structure determination of amethinol A,a prototypic amethane diterpene from Isodon amethystoides bearing a six/five/seven‐membered carbon‐ring system

We report the isolation of a novel diterpene, designated as `amethane', from Isodon amethystoides (Lamiaceae). The diterpene [amethinol A; systematic name: (4aR,4bR,7R,10aS)‐4b,7‐dihydroxy‐7‐isopropyl‐1,1‐dimethyl‐9‐oxododecahydrobenzo[a]azulene‐4a(2H)‐carboxylic acid], possesses a unique skeleton containing a six/five/seven‐membered tricyclic system. Intermolecular O—H…O close contacts were found to the carboxyl, carbonyl and hydroxy groups, connecting molecules into a two‐dimensional structure. A possible biosynthetic pathway has been proposed. In addition, the compound was evaluated for its biological activities against different disease targets, and was found to significantly attenuate RORγt‐dependent autoimmune responses.     

The identification of some novel four‐membered ring cyclic triphosphenium ions in solution

The first four‐membered ring cyclic triphosphenium ions with carbon substituents (methyl or cyclohexyl) on the outer phosphorus atoms have been identified in solution by ³¹P NMR spectroscopy. The cyclohexyl derivative in the presence of [SnCl₆]²⁻ as counterion was stable enough for methylation by methyl triflate to be carried out. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:464–467, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20043