A method for functional analysis of organosilicon compounds containing silacyclobutane groups

A method of determining quantitatively silacyclobutane rings in organosilicon compounds is worked out. It is based on addition of bromine or iodine to a Si-C bond in the ring, followed by determination of those elements in the resultant Si-Br or Si-I group. The error in determining bromine or iodine numbers by the method is 0.5–2.0%; the error in determining percentage bromine (iodine) is 0.5–2.0%. A determination takes 3–4 hr. The silacyclobutane group does not react with thiocyanogen, so that it is possible to determine separately multiple bonds and silacyclobutane groups present in one and the same molecule.     

Electrochemical reduction of 1,1-dihalo-2,2-disubstituted cyclopropanes

The electrochemical reduction of 1,1-dihalo-2-R-2-methylcyclopropanes was studied by polarography and preparative electrolysis. A mixture of stereoisomeric monoboro- and monochlorocyclopropanes was obtained with preparative yield of 60–70% in preparative electroreduction in methanol against a background of 0.1 M LiClO₄. In the case of bromine derivatives of cyclopropanes (except when R = CN) an effect was found on the part of the current density on the ratio of cis and trans isomers, which was interpreted as a change, in dependence on current density, of the contributions of the reactions of reduction of the starting compounds (S_N2 mechanism) and ionic pairs (S_N1 mechanism). The effect of the solvent (CHCl₃, DMF, DMSO, MeOH) and background salt (LiClO₄, Et₄NBr) on the ratio of stereoisomers is in agreement with this interpretation.A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Science Center, Russian Academy of Sciences, Kazan. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 9, pp. 2023–2032, September, 1992.     

Bromination and iodination of trialkylethynylsilanes

Conclusions The addition of bromine and iodine to trimethyl- and dimethylethylethynylsilanes has been studied. The halogenation of these compounds takes place stepwise. The first molecule of bromine adds at 30–50° and the second at 70–90°. In the case of bromination under UV irradiation, hydrogen bromide is eliminated as a side-reaction. The addition of iodine ceases at the stage of the formation of the diiodovinylsilanes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 693–694, March, 1967.     

Halogenation of the components of nucleic acids

Summary Preparative methods have been worked out for the bromination of unprotected deoxy-AMP, deoxy-GMP, and deoxy-CMP and methods have been devised for the isolation and purification of the bromine derivatives.Some physicochemical characteristics (UV spectra, R_f values on thin-layer and paper chromatography, coefficients of millimolar extinction) of the bromine derivatives of the DNA components obtained have been determined.Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 524–527, July–August, 1976.     

Anion-radical mechanism of bromine exchange by iodine in furan derivatives

The kinetics of bromine exchange by iodine in furan derivatives were studied; it is shown that the reaction is reversible and inhibited by oxidizing agents. Chloro derivatives of furan do not undergo this reaction. A cryptoreductive mechanism is proposed; the first stepof this mechanism consists of electron transfer to the halofuran molecule with subsequent reversible dissociation of the anion radical — inclusion of the iodide anion in the dissociation equilibrium leads to the substitution product.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1601–1606, December, 1976.     

Determination of Some Catecholamines by Coulometric Titration and Cyclic Voltammetry

Catecholamines quantitatively react with electrogenerated halogens. The reactions of adrenaline with bromine and iodine involve three electrons, and the reactions of dopamine with chlorine and bromine involve two electrons. Possible reaction schemes are proposed. Adrenaline and dopamine are reversibly oxidized at graphite and glassy-carbon electrodes in acid media at 0.7 and 0.58 V, respectively, to form corresponding quinones. Determination limits and linearity ranges of oxidation current were found as functions of catecholamine concentrations. The relative standard deviation was 1–4% for model solutions. A procedure was proposed for the electrochemical determination of adrenaline and dopamine in pharmaceuticals.__________Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 7, 2005, pp. 753–758.Original Russian Text Copyright © 2005 by Ziyatdinova, Budnikov.     

Synthesis of regecoline

An improved synthesis of the quaternary homoproaporphine alkaloid regecoline from the main alkaloid ofColchicum kesselringii Rgl. — kesselringine — has been carried out by two methods: by photochemical conversion (yield 77%) and by iodine oxidation (yield 86%). It has been shown that the iodine oxidation of homoproaporphines of the kesselringine type leads to C_6a-dehydro derivatives.V. I. Lenin Tashkent State University. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 464–465, July–August, 1986.     

The reaction of esters of thioacids of tervalent arsenic with halides and some halogen-containing compounds

Conclusions The reaction of esters of thioaeids of tervalent arsenic with chlorine, bromine, iodine chloride, sulfuryl chloride, thionyl chloride, HCl, PCl₅, dichloro(phenyl)phosphine, and chloro(ethyl)phenylphosphine leads to the complete cleavage of the As-S bonds with the formation of corresponding halogenoarsines and sulfur-containing compounds.Deceased.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1612–1616, July, 1972.     

Bromination of 1-(4-nitrophenyl)-2-formylpyrrole

Depending on the amount of bromine, the bromination of 1-(4-nitrophenyl)-2-formylpyrrole with bromine in chloroform without a catalyst gives 5-bromo and 4,5-dibromo derivatives. 4-Bromo-1-(4-nitrophenyl)-2-formylpyrrole is formed in the presence of excess AlC1₃, while a mixture of 3,4- and 4,5-dibromo derivatives with preponderance of the latter is formed with excess bromine. The results are compared with the literature data on the bromination of 2-formylpyrrole, 2-formylfuran, and 2-formylthiophene and are interpreted with allowance for the electronacceptor effect of the p-nitrophenyl substituent attached to the nitrogen atom of the pyrrole ring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 662–665, May, 1982.     

Polarographic study of η2-acetylenic derivatives of cymanthrene

Conclusions The electrochemical reduction of ₂-acetylenic derivatives of cymanthrene CpMn(CO)₂-(PhC=CR) (R=H, Ph, SiPh₃, and GePh₃) proceeds in three consecutive steps. The addition of one electron in the first step leads to the elimination of the acetylenic ligand, which is reduced in the subsequent steps. The nature of R does not affect the course of the electrochemical reaction and is only slightly reflected in the reduction potential values.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimlcheskaya, No. 1, pp. 200–202, January, 1985.     

Reactivity of main grouptransmittion metal bonds : III. Reactions of halogens with Ph3SiMn(CO)5 and Ph3SnMn(CO)5

The products of the reaction of Ph₃MMn(CO)₅ (M = Si or Sn) with chlorine, bromine and iodine in tetrachloromethane, have been determined.Ph₃SiMn(CO)₅ does not react with iodine, and the SiMn bond is cleaved by chlorine and by bromine.Ph₃SnMn(CO)₅ reacts in a much more complex manner, PhSn bond cleavage occurring with all three halogens to give mono-, di-, and, with the exception of iodine, tri-halogenated derivatives. Bromine, in high concentration, and iodine also cleave the SnMn bond.     

Synthesis of biologically active bromine derivatives of quercetin

The synthesis of a series of bromine derivatives of quercetin differing by the number of bromine atoms introduced is described. It has been shown that in the dynamics of the bromination process the deciding factors affecting the qualitative and quantitative compositions of the reaction products are the temperature regime and the ratio of the reactants. Thus, the use of equimolar amounts of the reactants in dioxane in the temperature interval from 20 to 25° C gives a monobromo derivative, while all other conditions give mixtures of bromo derivatives. The antiviral and antitumoral activities of the mono- and dibromo derivatives of quercetin have been studied.Al-Farabi Kazakh State National University, Almaty, fax (3272) 47 26 09. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 709–711, September–October, 1996. Original article submitted February 27, 1995.     

[2+4]Cycloaddition of perfluoroazomethines

Conclusions Perfluoroazomethines react with cyclopentadiene at 160–180°C to form [2 + 4]-cycloadducts, viz., fluorine derivatives of 5-azabicyclo[2.2.1]hept-2-ene. These derivatives were used to obtain the products of the radical addition of chlorine, bromine, and bis(trifluoromethyl)-nitroxyl.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1437–1440, June, 1986.     

Iodometric microdetermination of semicarbazide by amplification reactions

An analytical method for the determination of 10–2000 μg of semicarbazide is described, using titrimetric procedure with an amplification reaction. It relies upon the reaction of semicarbazide, in phosphate-buffer (pH 7) solution, with a chloroform solution of iodine, and removal of its excess; oxidation of the iodide formed with bromine; and determination of the liberated iodate by the Leipert amplification procedure. The recovery ranged from 97.0 to 100.1%.     

Degree of solid-phase oxidation of nickel and cobalt phthalocyanines by halogens

Electronic and IR transmission spectroscopy and ESR have been used to investigate the products obtained in the oxidation of layes of nickel and cobalt phthalocyanines by halogen vapors. It has been established that cobalt phthalocyanine in chlorine or bromine vapor forms stable cation radicals in which one electron has been detached from the cobalt and the other from the phthalocyanine ligand; in iodine vapor, a partially oxidized product is formed, with a positive charge on the ligand. Nickel phthalocyanine in bromine vapor at high pressure of bromine, and also in chlorine or iodine vapor, nickel phthalocyanine forms partially oxidized products with various degrees of oxidation of the ligand. An interpretation is given for the spectra of the ionic species that have been investigated; the interpretation can be used in particular to determine the degree of the ionic species on the basis of their spectra.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 5, pp. 528–534, September–October, 1989.The authors wish to thank A. V. Baranov for measuring the Raman spectrum of the bromine-oxidized Copc.     

Electrochemical cyclization of tetramethyl esters of 2-substituted propane-1,1,3,3-tetracarboxylic acids in the presence of salts of hydrohalic acids

The chemical and electrochemical cyclization of tetramethyl esters of 2-substituted propane-1,1,3,3-tetracarboxylic acids in the presence of hydrohalic acid salt mediators were studied. It was found that the chemical variant of the cyclization of the corresponding ,'-dianions of esters of propane-1,1,3,3-tetracarboxylic acids by the action of iodine or bromine is substantially inferior to the electrochemical variant. In the latter case, the esters of substituted cyclopopane-1,1,2,2-tetracarboxylic acids are formed in a 87–98% yield. The tetramethyl ester of 2-isopropylpropane-1,1,3,3-tetracarboxylic acid, which under the electrolysis conditions decomposes according to a Michael retroreaction is an exception.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2783–2789, December, 1990.     

Electrochemical reduction of 4-(nitrophenyl)-1,2- and 4-(nitrophenyl)-1,4-dihydropyridines and the ESR spectra of the obtained free-radical particles

In the course of electrochemical generation the intermediate reaction products (free radicals of the nitro-and nitrosophenyl type, which appear on the cyclic voltammetric curves) were identified by ESR. The N-substituted derivatives are characterized by reduction of the dihydropyridine ring. The 4-nitrophenyl derivatives are characterized by the absence of intramolecular electron transfer during electrochemical reduction. In the case of the corresponding derivatives of 1,2-dihydropyridine intramolecular transfer of electrons and protons is possible under these conditions. Combined schemes of the primary and secondary chemical reactions involved in the electrochemical reduction of the investigated compounds are presented. It was established that the substances investigated with reference to the mechanism of the electrochemical transformations include the antihypertensive nifedipine (corinfar, fenigidine).Latvian Institute of Organic Synthesis, Riga LV-1006. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 219–233, February, 1997.     

Kinetics and mechanism of the reaction of 5-bromo-2- carbonyl derivatives of furan with amines

The kinetics of exchange of bromine in 5-bromo-2-carbonyl derivatives of furan by dimethylamino and morpholino groups was studied. The reaction is kinetically complicated for 5-bromofurfural (I) — aldehyde I initially reacts simultaneously at both the carbonyl group to give the aminocarbinol and at the bromine atom with exchange by an amino group. The accumulation of the ammonium salt in the latter reaction leads to the development of an autocatalytic reaction, the product of which is 5-N,N-dialkylaminofurfurylidene-N,N-dialkylammonium bromide. Amines react with the ketones without complications; the second-order rate constants are presented. The rate of exchange decreases in the order CHO > COC₆H₅ > COCH=CHC₆H₅ > COCH₃ > CH=CHCOC₆H₅.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1465–1470, November, 1976.     

Synthesis of derivatives of 7,8-dihydrothiazolo[2,3-<Emphasis Type="Italic">i</Emphasis>]purine by halocyclization of 6-allylthiopurine

7-Halomethyl-7,8-dihydrothiazolo[2,3-i]purines were synthesized by the reaction of bromine and iodine with 6-allylthiopurine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, 1551–1553, October, 2004.     

Electrochemical reduction and structural properties of borylphosphinoethene derivatives

The intramolecular coordination bonds between phosphoryl-, thio-, and selenophosphoryl groups and boron facilitate the electrochemical reduction of borylphosphinoethene derivatives as compared with their noncyclic analogs. In 1-dibutylboryl-2-diphenylphosphino-1-butyl-2-phenylethene reception of the first electron takes place in the C=C bond. In the oxide, sulfide, and selenide, the electron-accepting centers are most likely the P-C₁ and P=R (R=S, Se) bonds.Deceased.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 24–27, January, 1990.