Vicinal Dihalides Research Articles

ChemInform Abstract: REACTION OF ORGANIC HALIDES WITH CHLOROTRIS(TRIPHENYLPHOSPHINE)COBALT(I)

AbstractDie Benzylhalogenide (I) reagieren mit dem einwertigen CobaIt‐Komplex (II) zu den Dimerisierungsprodukten (III).

Reaction of organic halides with chlorotris(triphenylphosphine)cobalt(I).

Reaction of various types of organic halides with a monovalent cobalt complex, chlorotris (triphenylphosphine) cobalt (I) is described. Reaction of benzylic monohalides, dihalides and trihalides with CoCl (Ph3P)3 gave a coupling product with formation of a carbon-carbon single bond, double bond and triple bond, respectively, under mild and non-basic conditions. Dehalogenation of non-benzylic vicinal dihalides with the reagent took place cleanly to give an olefin in high yield. Reductive coupling of allylic halides using the reagent afforded regioselectively a 1, 5-diene with retention of the stereochemistry of the carbon-carbon double bond of the allylic halides used. By using this reaction, (E, E, E, E)-squalene was stereospecifically synthesized from (E, E)-farnesyl bromide. Reaction of halohydrins with CoCl (Ph3P)3 gave exclusively a ketone in the presence of an amine or olefin through an alkylcobalt intermediate. A 1, 2-hydrogen shift is involved in this reaction.

PHOTO-DEHALOGANATION OF VICINAL DIHALIDE TO OLEFIN

Abstract Irradiation of vicinal dihalides in the presence of methanol or triethylamine resulted in an efficient dehalogenation to regenerate olefins.

Syn-anti Dichotomy in zinc-promoted dehalogenation of open-chain vicinal dihalides: The effect of the leaving groups

The title effect has been investigated in the homologous series of erythro- and threo-5,6-dihalodecanes (X = Br, Y = I; X = Cl, Y = I; X = F, Y = I; X = Br, Y = Br; X = Cl, Y = Br; X = F, Y = Br; X = Cl, Y = Cl; X = F, Y = Cl). It has been found that proportion of syn-elimination in the overall reaction varies with the variation of the halogen leaving groups in the order I < Br < Cl < F, ranging between the extreme 3-30% in the erythro- and 5-60% in the threo-series. On basis of the variable transition state theory, observed pattern of syn-anti dichotomy has been correlated with the extent of double bond development in the transition state.

Electrochemical dehalogenation of open-chain vicinal dihalides at mercury cathodes: The effect of leaving group identity on E1/2 values and on steric course

The title problem has been investigated polarographically in the homologous series of erythro and threo-5,6-dihalodecanes (X = Br, Y = I; X == Cl, Y = I; X = F, Y = I; X = Br, Y = Br; X = Cl, Y = Br; X = F, Y = Br; X = Cl, Y = Cl; X = F, Y = Cl). Each dihalide from the series gave a single two-electron wave. A very pronounced dependence of half-wave potential on halogen group identity was found in the series, the E1/2 values ranging from -0.3 V (X = Br, Y = I) to -2.8 V (X = F, Y = Cl). Controlled-potential electrolyses of the dihalides were accomplished at mercury pool electrode affording always cis- and/or trans-5-decene as the sole product, in almost quantitative (>90%) yields. Stereochemistry of the dehalogenation was deduced from the olefin-isomer distribution data determined by VPC. Very marked differences were found in the series, the elimination stereochemistry ranging between a clean anti and a prevalent syn, in dependence on the identity and configuration of the halogen groups.

Cathodic reduction of aromatic halides. an evidence for an ionic mechanism

A study on the cathodic reduction of the C-X bond in aryl vicinal dihalides and monohalides is made, demostrating in an unequivocal way the presence in all the cases of aryl anion intermediates.

Elimination and substitution in the reactions of vicinal dihalides and oxyhalides trimethylstanoylsodium. Effects of solvent and of ion aggregation on course and stereochemistry

Elimination and substitution in the reactions of vicinal dihalides and oxyhalides trimethylstanoylsodium. Effects of solvent and of ion aggregation on course and stereochemistry

Dehalogenation reactions of vicinal dihalides. Part V. Kinetic study of the reactions of 1,2-dihalogeno-1,2-diphenylethanes with triphenylphosphine

Triphenylphosphine-promoted dehalogenation reactions of meso-1,2-dibromo-1,2-diphenylethane and some para-substituted derivatives have been studied in dimethylformamide. Substituent effects on the reaction rate are in agreement with a concerted anti-elimination mechanism and do not support a stepwise mechanism involving bridged intermediates. The effect of solvent has also been investigated and the nucleophilicity of triphenylphosphine towards bromine is briefly discussed.

Dehalogenation reactions of vicinal dihalides. Part IV. Kinetics of amine-promoted eliminations of 1-chloro-2-iodo-1,2-diphenylethane in aqueous dioxan

The rate constants for the dehalogenation of 1-chloro-2-iodo-1,2-diphenylethane promoted by a series of amines have been determined in 60% dioxan. Pyridine reactivity follows a Bronsted relation with a slope β 0·29, which suggests little bond formation between the incoming nucleophile and iodine. Dehalogenation rates also correlate the stability constants of charge-transfer complexes between amines and iodine. The slope of this correlation is close to unity and this indicates that the charge distribution in the transition state of the dehalogenation reaction should be very similar to that of the charge-transfer complex.

Formation of carbon-carbon double bonds by the reaction of vicinal dihalides with sodium in ammonia

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTFormation of carbon-carbon double bonds by the reaction of vicinal dihalides with sodium in ammoniaEvan L. Allred, Boyd R. Beck, and Kent J. VoorheesCite this: J. Org. Chem. 1974, 39, 10, 1426–1427Publication Date (Print):May 1, 1974Publication History Published online1 May 2002Published inissue 1 May 1974https://doi.org/10.1021/jo00926a024RIGHTS & PERMISSIONSArticle Views240Altmetric-Citations25LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (318 KB) Get e-Alerts Get e-Alerts

Chlorination of α-sulfonyl carbanions with hexachloroethane: A novel preparation of α-halosulfones

The cyclic sulfones 1, 2, and 3 are lithiated in benzene with n-butyllithium. Lithiation is demonstrated to lead to α-mono, α,α′-di and/or α,α-di and α,α,α′ trimetallation. The lithiated sulfones are chlorinated with hexachloroethane (HCE). Some mechanistic aspects of the reaction of the lithiosulfones with vicinal dihalides are discussed.

Dehalogenation reactions of vicinal dihalides. Part III. Dehalogenations of 1-chloro-2-iodo-1,2-diphenylethane induced by a variety of nucleophiles. The nucleophilic reactivity towards iodine

Dehalogenations of erythro-1-chloro-2-iodo-1,2-diphenylethane promoted by a variety of nucleophiles have been studied in methanol and, in the case of halide ions, also in NN-dimethylformamide. The susceptibility of iodine in this compound to undergo nucleophilic attack is extremely high and surpasses that of bromine by a factor larger than 106. An order of nucleophilic reactivity towards iodine bonded to a saturated carbon has been established. Dehalogenation rates follow approximately the Edwards equation with α and β values (2·13 and –0·12, respectively) indicating that polarizability and desolvation factors play a larger role than basicity in determining nucleophilic reactivity. The importance of the polarizability is also shown by the reactivity order of the halide ions in dimethylformamide which is I– > Br– > Cl–. As an electrophilic centre, iodine appears to have a susceptibility to be attacked by polarizable nucleophilies which is larger than that of the saturated carbon atom.

Reactions of dicobalt octacarbonyl and related compounds with gem-dihalides

Dicobalt octacarbonyl and some of its derivatives (NaCo(CO) 4, Co 4(CO) 12, Hg[Co(CO) 4] 2, [Co(CO) 3PPh 3] 2, NaCo(CO) 3PPh 3) react with activated gem-dihalides, R 2CX 2, such as dichlorodiphenylmethane, 9,9-dihalofluorenes and dimethyl dibromomalonate, to give the ‘dimer’ olefin, R 2CCR 2. The course of this conversion involves formation of the coupling product, R 2XCCXR 2, followed by dehalogenation of the latter. These separate steps have been confirmed for activated monohalides (bromodiphenylmethane, 9-bromofluorene, dimethyl bromomalonate) which were readily coupled by cobalt carbonyls, and for activated vicinal dihalides (D,L and meso-dibromostilbene, 9,9′-dichlorobisfluorenyl) which cobalt carbonyls readily dehalogenated. A radical mechanism is favored for these processes, and indirect evidence in its favor is presented.

Studies in organophosphorus chemistry : Reaction of epoxides with tertiary phosphine dihalides

The reaction of tertiary phosphine dichlorides and dibromides with epoxides gives vicinal dihalides. The reaction involves initial cleavage of the epoxide carbon—oxygen bond emanating from the most highly substituted epoxide carbon. Haloalkoxyphosphonium salts are thus formed which undergo subsequent reaction giving vicinal dihalides and tertiary phosphine oxides. The vicinal dihalides which result from epoxides of cyclohexenes are mixtures of cis and trans isomers in which the cis isomer is formed by backside attack of halogen at both epoxide carbons.

Free-radical reduction and dehalogenation of vicinal dihalides by tri-n-butyltin hydride

Free-radical reduction and dehalogenation of vicinal dihalides by tri-n-butyltin hydride

Synthesis and properties of regular copolymers II—Spectroscopic analysis of regular copolymers of vinyl compounds with aliphatic dihalides

I.r. and n.m.r. spectra of polymers prepared by reacting vinyl. monomer with alkali metal in the presence of aliphatic dihalides are discussed and indicate that the materials may be described in general as regular copolymers of repeat unit [MRM] where M is monomer and R is the ligand of the dihalide. The spectra of those polymers prepared with vicinal dihalides, however, confirm that head-head homopolymer is prepared by an elimination reaction. The chemical shifts of a number of such polymers are listed and assigned, and the correlation of these assignments with the polymeric structures is discussed.

The synthesis of cycloalkanes via anionic coupling reactions

A number of cycloalkanes have been isolated among the products of the reactions of geminal and vicinal dihalides with dimeric dianions produced from substituted styrenes by the action of lithium. The n.m.r. and mass spectra of the products are reported.

Dehalogenation reactions of vicinal dihalides. Part II. Substituent and leaving-group effects in the reactions of 1,2-dihalogeno-1,2-diphenylethanes with iodide, bromide, and chloride ions

The I–-, Br–-, and Cl–-promoted dehalogenations of several meso- or erythro-1,2-dibromo-1-(4-R1-phenyl)-2-(4-R2-phenyl)ethanes and the I–- and Br–-promoted dehalogenations of erythro-1-bromo-2-chloro-1,2-di-phenylethane have been investigated. The reactions with I– have been carried out in MeOH and dimethylformamide, those with Br– and Cl– in dimethylformamide. Both leaving-group and substituent effects indicate that these reactions occur by a completely concerted mechanism of elimination with a large amount of double bond developed in the transition state. It has been observed that the order of nucleophilic reactivity in dimethylformamide is I– > Br– > Cl–, which is consistent with an attack of the nucleophile on one bromine atom of the substrate. A peculiar result has been obtained in the case of the dinitro-derivative (R1= R2= NO2) which is, with Br– and Cl–, much more reactive than expected. A modification of the usual transition-state structure is probably required in this case.

Conformation of open‐chain compounds. Part 3. Carbon‐halogen stretching frequencies and conformation of some vicinal dihalides

AbstractA study of the infrared and Raman spectra of some vicinal dihalogeno‐ethanes, ‐propanes and ‐butanes with predominant antiperiplanar orientation in the straight chain and branched series, reveals that the two C‐Hal stretching frequencies occur characteristically as a more or less strongly coupled pair: an intense Raman band (νs) and a strong infrared active mode of vibration (νas) at lower frequencey.The C‐Hal frequencies of the gauche conformations are weakly coupled.The position of the bands and the difference Δν = νs − νas are functions of the chemical/geometrical structure in the vicinity of the C‐Hal bonds. Empirical rules are presented by which the C‐Hal frequencies or, in strongly coupled systems, the average frequency of anti as well as of gauche forms can be predicted with fair accuracy.

Dehalogenation of vicinal dihalides. Exceptional utility of dihydroarylides

Dehalogenation of vicinal dihalides. Exceptional utility of dihydroarylides