Synthesis of bi-and tricyclic monoesters of dicarboxylic acids

A thermal addition of aliphatic dicarboxylic acids to bicyclo[2.2.1]-heptene hydrocarbons and to tricyclo[5.2.1.0^2,6]deca-3,8-diene was investigated and new samples of dicarboxylic acids alicyclic monoesters were synthesized. Some of monoesters synthesized have a pleasant fragrance and can find application as fragrance substances. They are also of interest as initial components for preparation of new organic compounds.     

Ion-molecule reactions of gas-phase chromium oxyanions: CrxOyH z − + O2

Chromium oxyanions, Cr(x)O(y)H(z)(-), were generated in the gas-phase using a quadrupole ion trap secondary ion mass spectrometer (IT-SIMS), where they were reacted with O(2). Only CrO(2)(-) of the Cr(1)O(y)H(z)(-) envelope was observed to react with oxygen, producing primarily CrO(3)(-). The rate constant for the reaction of CrO(2)(-) with O(2) was approximately 38% of the Langevin collision constant at 310 K. CrO(3)(-), CrO(4)(-), and CrO(4)H(-) were unreactive with O(2) in the ion trap. In contrast, Cr(2)O(4)(-) was observed to react with O(2) producing CrO(3)(-) + CrO(3) via oxidative degradation at a rate that was approximately 15% efficient. The presence of background water facilitated the reaction of Cr(2)O(4)(-) + H(2)O to form Cr(2)O(5)H(2)(-); the hydrated product ion Cr(2)O(5)H(2)(-) reacted with O(2) to form Cr(2)O(6)(-) (with concurrent elimination of H(2)O) at a rate that was 6% efficient. Cr(2)O(5)(-) also reacted with O(2) to form Cr(2)O(7)(-) (4% efficient) and Cr(2)O(6)(-) + O (2% efficient); these reactions proceeded in parallel. By comparison, Cr(2)O(6)(-) was unreactive with O(2), and in fact, no further O(2) addition could be observed for any of the Cr(2)O(6)H(z)(-) anions. Generalizing, Cr(x)O(y)H(z)(-) species that have low coordinate, low oxidation state metal centers are susceptible to O(2) oxidation. However, when the metal coordination is >3, or when the formal oxidation state is > or =5, reactivity stops.     

Multicapillary Chromatographic Columns

The possibilities for multicapillary tubes with channels 3–10 μm in diameter and a total number of channels of about 2 × 10⁵−10⁶ to be used as chromatographic columns are studied. It is shown that substances with a sufficiently high boiling point can be separated at temperatures of 20–30°C in 2–3 min with an efficiency of about 1500 theoretical plates per meter (300 theoretical plates for a 20-cm column). __________ Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 10, 2005, pp. 1075–1079. Original Russian Text Copyright ? 2005 by Rudenko, Shoromov, Kumakhov, Naida.     

Beyond the Roger Brown rearrangement: long-range atom topomerization in conjugated polyynes

Long-range carbon atom topomerization in a 1,3-diyne has been demonstrated for the first time. 1-Phenyl-4-p-tolyl-1,3-butadiyne, (13)C-enriched at C-1, was synthesized and subjected to flash vacuum pyrolysis. At 800 degrees C and 0.01 Torr, this resulted in nearly complete (13)C label equilibration between C-1 and C-2, as seen by NMR analysis. Pyrolysis at 900 degrees C further led to ca. 35% of the label migrating about equally to C-3 and C-4. These results demonstrate that both intrabond and interbond atom exchange processes are operative, with the former having a lower activation barrier. DFT and Moller-Plesset calculations support a mechanism that passes through Brown rearrangement (1,2-shift), closure to trialene (bicyclo[1.1.0]-1,3-butadiene), bond-shift isomerization to exchange C-2 and C-3, and ring opening. The resulting vinylidene can rearrange to a butadiyne with the isotopic label at C-3 or C-4. Consistent with earlier calculations, trialene is predicted to have alternating peripheral bonds, with a weak central sigma bond and significant diradical character. Trialene is predicted [(B3LYP/6-311+G(2d,p)] to lie 64.6 kcal/mol above butadiyne, with barriers of 2.2 and 4.4 kcal/mol, respectively, for ring opening or bond-shift isomerization. Other potential rearrangement mechanisms which pass through tetrahedrene (E(rel) = 167.2 kcal/mol) or 1,2,3-cyclobutatriene (E(rel) = 161.1 kcal/mol) lie at much higher energies.     

Amino acid analysis by micellar electrokinetic chromatography with laser-induced fluorescence detection: application to nanolitre-volume biological samples from Arabidopsis thaliana and Myzus persicae

Amino acids were derivatised with 4-fluoro-7-nitrobenzo-2,1,3-oxadiazol (NBD-F), separated by micellar electrokinetic chromatography (MEKC), and detected by argon-ion (488 nm) laser-induced fluorescence. The optimised MEKC background electrolyte conditions were: 40 mM sodium cholate, 5 mM beta-cyclodextrin in 20 mM aqueous borate buffer, pH 9.1, with 7% v/v acetonitrile. Using these conditions, 19 amino acids were separated within 17 min. The limits of detection were in the range of 7.6-42.2 pmol/mL and limits of quantitation from 0.05-0.14 nmol/mL. The method was systematically validated for injection volume error, migration time variation, calibration linearity, accuracy, precision, and recovery. Nanolitre volume samples of phloem sap of individual sieve element cells from the plant Arabidopsis thaliana and honeydew from the aphid Myzus persicae were directly analysed with this method. Quantitative amino acid concentrations in these two biological matrices were profiled for the first time. This method is particularly important because it allows the complete profile of the amino acids obtained from individual phloem elements, allowing cell to cell and plant to plant variation to be quantified, which to date has not been possible with Arabidopsis thaliana.     

Denaturation and renaturation of the 11S globulin of cotton seeds by polarography

It has been established by a polarographic analysis of the globulins of cotton seeds that the 7S and 11S golublins possess a two-step polarographic wave with a half-wave potential of –1.42 V. On the basis of the results of a study of the kinetics of thermal denaturation the high lability of the 11S globulin on heating has been shown. The conditions have been determined of the complete denaturation of the 11S globulin in 8 M urea solution and it has been established that the latter is an irreversible process.Institute of the Chemistry of Plant Substances of the Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 809–813, November–December, 1980.     

Water-methanol-benzene ternary system. Thermochemical experiment and computer simulation

Solution heats have been measured for benzene dissolved in mixtures of water with methanol at 25°C. The resulting values are compared with data for water-methanol-aniline, water-acetonitrile-benzene, and water-acetonitrile-aniline systems. Computer simulations have been performed for binary mixtures of water with methanol and dilute solutions of benzene in these mixtures. Thermodynamic and structural characteristics of solutions were obtained by calculations. The enthalpy of benzene transfer from water into a mixed solvent correlates with the relative deviation of the local composition from the mean composition of the mixture.     

Electrophilic fluorinating reagent mediated synthesis of fluorinated alpha-keto Ethers,benzil, and 6,6'-dialkoxy-2,2'-bipyridines

Interactions of various fluorinated and nonfluorinated alcohols with trans-stilbene in the presence of electrophilic reagents were studied. Under neat conditions, reactions of trans-stilbene (1) with fluorinated alcohols, R(f)OH (R(f) = CF3CH2-, CFH2CH2-, CF3CF2CH2-, CF2H(CF2)3CH2-, (CF3)2CH-, (CF3)3C- (2a-f) in the presence of an electrophilic reagent, 1-(chloromethyl)-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (Selectfluor) or N,N-difluoro-2,2'-bipyridinium bis(tetrafluoroborate) (MEC-31), gave alpha-keto ethers (3a-f) and benzil (4) in good to moderate yields. alpha-Keto ether and benzil formation was very much dependent on the reaction time, the degree of fluorination of the alcohols, and whether a solvent such as CH3CN, DMF or DMA was utilized. In solution, alpha-keto ethers and benzil did not form. Interestingly, under neat conditions, nonfluorinated alcohols, ROH (R = CH3-, CH3CH2-, CH3CH2CH2-, CH3CH2CH2CH2-, CH3CH2CH2CH2CH2CH2-) (5g-k) did not react with trans-stilbene in the presence of MEC-31 but gave 6,6'-dialkoxy-2,2'-bipyridines (6g-k), regioselectively, in excellent isolated yields. On the other hand, fluorinated alcohols did not react with MEC-31. Reaction of MEC-31 with an excess of diethylene glycol (7) gave the bipyridine derivative (8) in 88% isolated yield. Reaction of 8 either with diethylaminosulfur trifluoride (DAST) or bis(2-methoxyethyl)aminosulfur trifluoride (Deoxofluor) readily produced the corresponding difluoro derivative (9) in 85% isolated yield. All new compounds have been characterized by spectroscopic and elemental analysis.     

Study of the mechanism of recyclization of furans into thiophenes and selenophenes in conditions of acid catalysis. 5. Direction of protonation of furans

2,5-Dimethyl-3-D-furan was prepared for the first time. Its recyclization into the corresponding thiophene and selenophene was investigated. The possibility of -C-protonation of the furan ring was confirmed by experimental and quantum chemical data.See [1] for Communication 4.Scientific-Research Institute of Chemistry, N. G. Chernyshevskii Saratov State University, Saratov 410026. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1030–1034, August, 1997.     

Research on heterocyclic compounds. XXIII. Phenyl derivatives of fused imidazole systems

The reaction of various heteroarylamines with ethyl 2-benzoyl-2-bromoacetate was used to obtain some imidazo[1,2-a]pyridines, imidazo[1,2-a]pyrimidines, imidazo[2,1-b]thiazoles and imidazo[2,1-b]benzothiazoles characterized by the presence of a phenyl moiety on the imidazole ring. In the case of thiazole and benzothiazole derivatives, unexpected by-products were isolated and their structures elucidated.