Reaction Of Xanthate Research Articles

A Novel 1,3-Stannyl Shift Promoted Intramolecular Cyclizations of α-Stannyl Radicals with a Formyl Group

Reactions of α-stannyl bromides and xanthates with tributyltin hydride generate α-stannyl radicals. Intramolecular cyclizations of these radicals with a formyl group afford γ-stannyl alkoxy radicals that undergo a 1,3-stannyl shift from carbon to oxygen. The carbon radicals obtained can be trapped inter- or intramolecularly. Approximately, the rates of 5-exo cyclizations of α-stannyl radicals with a formyl group and terminal olefin are similar.

Some New Radical Reactions of Xanthates

AbstractXanthates are convenient precursors of a variety of radicals that can be captured in an inter‐ or intramolecular fashion. Overall, the process involves rupture of the sulfide C‐S bond and addition of the elements of the xanthate to the olefinic trap. The xanthate in the product can be used in another radical sequence or ionically modified in a great variety of ways. S‐Propargyl xanthates exhibit a special but interesting behaviour which involves a sigmatropic rearrangement to the corresponding allene and ring closure to a novel betaine.

New radical reactions of S-alkoxycarbonyl xanthates. Total synthesis of (±)-cinnamolide and (±)-methylenolactocin

Irradiation with visible light of S-alkoxycarbonyl xanthates derived from various alcohols gives rise to alkoxycarbonyl radicals with bifurcate reactivity: loss of carbon dioxide leads to deoxygenated derivatives (i.e. alkyl xanthates) whereas intramolecular addition to a suitably located double bond produces lactones; these new reactions were applied to the total synthesis of (±)-cinnamolide and (±)-methylenolactocin.

ChemInform Abstract: Sequential Pericyclic Reaction of Unsaturated Xanthates. Intramolecular Cycloaddition Selectivity of the 2,4‐Alkadienyl 2‐ Alkenyl Sulfides.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Sequential pericyclic reaction of unsaturated xanthates. Intramolecular cycloaddition selectivity of the 2,4-alkadienyl 2-alkenyl sulfides

Heating of S-(1-vinyl-2-alkenyl) S-(2-alkenyl or alkynyl) dithiocarbonates (dithiolcarbonates) derived from [3,3]-sigmatropic rearrangement of O-(2,4-alkadienyl) S-(2-alkenyl or alkynyl) dithiocarbonates (xanthates) gave the 2,4-alkadienyl 2′-(alkenyl or alkynyl) sulfides, which then underwent intramolecular Diels-Alder cycloaddition to give hydrobenzo[c]thiophene derivatives. The thermal cyclizations of O-(2,4-pentadienyl) derivatives of xanthate afforded mixtures of the cycloadducts, in which the cis-FUSED products slightly predominated over the trans-isomers. The selectivity of IMDA reactions is discussed based on the ab initio calculation data.

Photopolymerization of styrene and methyl methacrylate using macro photoinitiators. Synthesis and characterization of PS‐PEG‐PS or PMMA‐PEG‐PMMA block copolymers

AbstractMacro photoinitiators based on poly(ethylene glycol)s (PEG) bearing benzoyl xanthate moieties were synthesized by the reaction of PEG xanthates with benzoyl chloride. These macro photoinitiators possessing PEGs of different molecular weights were used in the photoinduced radical polymerization of styrene (S) and methyl methacrylate (MMA) to yield block copolymers having an inner‐PEG segment. The influence of the concentration of reactants and polymerization time on the yield and intrinsic viscosities of block copolymers were also investigated. Characterization of block copolymers was carried out by fractional precipitation and IR, UV and 1H NMR spectroscopic methods.

ChemInform Abstract: Sequential Pericyclic Reactions of Unsaturated Xanthates. One‐Pot Synthesis of Hydrobenzo(c)thiophenes.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Sequential pericyclic reactions of unsaturated xanthates. One-pot synthesis of hydrobenzo[c]thiophenes

O-Alka-2,4-dienyl S-(alk-2-ynyl or alk-2-enyl) dithiocarbonates (xanthates) underwent [3,3]sigmatropic rearrangement to give the dithiol esters which, on heating, extruded carbon oxysulfide (COS) to give the allylically rearranged sulfides which then underwent intramolecular Diels–Alder cycloaddition to give hydrobenzo[c]thiophenes. Lewis acids catalysed the extrusion and intramolecular cycloaddition reactions, in which the reactivity and endo-selectivity were remarkably enhanced. The structures of the cycloadducts were determined on the basis of the X-ray structure of a hydrobenzo[c]thiophene.

ChemInform Abstract: A Simple One‐Pot Synthesis of Hydroisobenzothiophenes via Three‐Step Sequential Pericyclic Reactions of Xanthates.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A simple one-pot synthesis of hydroisobenzothiophenes [formula omitted] three-step sequential pericyclic reactions of xanthates

Thermolysis of O -(2,4-alkadienyl) S -(2-alkenyl or 2-alkynyl) dithiocarbonates (xanthates) gave the hydroisobenzothiophene derivatives via two sequential [3,3]-sigmatropic rearrangement followed by the intramolecular cycloaddition.

Al-Fe precipitation during laser surface treatment: A TEM investigation

Alkyl xanthyl thiosulphates (R.OCSS.S2O3−) (RXT−) are formed in solution by mild oxidation (e.g. by I2) of solutions containing both xanthate and thiosulphate. They can also be formed by reaction of Cu2+ with xanthate and thiosulphate, reaction of dixanthogen with thiosulphate, and by reaction of xanthate with tetrathionate; these last three reactions can occur in flotation pulps in slightly acid or alkaline solutions (pH 5–10).Alkyl xanthyl thiosulphates are stable in acid and neutral solution; the solutions have a UV absorption maximum at 289 nm. In strongly alkaline solution (pH 12) RXT− decomposes within a few minutes to yield a xanthate (mostly) plus a little perxanthate. At pH 10 this decomposition to xanthate takes about 48 h. At pH 7–9 RXT− is relatively stable. RXT− is not extracted from aqueous solution with common solvents (chloroform, iso-octane, cyclohexane, or ether). It forms a water-insoluble adduct with cetyltrimethyl-ammonium bromide (CTAB); this adduct can be extracted into chloroform, and the extract has a UV absorption maximum at 296 nm.RXT− was found in solutions from the gangue-sulphide flotation section at Renison Ltd, the zinc flotation circuit and the copper flotation circuit at Mount Isa Mines Ltd, and the lead flotation section of The Zinc Corporation Ltd. The presence of RXT− in operating flotation plants has various practical and theoretical implications.

Reaction of cellulose xanthate with chromium compounds by UV spectroscopy

The type of chemical bond in the chromium compounds obtained which are based on cellulose xanthate has been ascertained.

Some reactions of alkoxythiocarbonyl derivatives with N,N-dimethylhydrazine

The reaction of xanthate (dithiocarbonate) esters with N,N-dimethylhydrazine leads to mixtures of the derived thionocarbamates and thionocarbazates whereas alkoxythiocarbonylimidazoles give cleanly the thionocarbazates. The outcome of these reactions is determined by the nature of the intermediate formed by expulsion of the leaving group.

Acceleration of the xanthation process of alkali cellulose

In spite of the abundance of articles and monographs devoted to the xanthation of alkali celluose [i, p. 243; 2, p. 86; 3, p. 157], up untilnowit has not been clear whether it is advisable to carry out this process at an elevated or reduced temperature, with vigorous or only slight agitation, or in the absence ("dry" method) or presence of solvent alkali ("wet" method). Moreover, the xanthation process of alkali cellulose is complicated by reactions involving the formation of by-products. Therefore the xanthation reaction cannot be described by simply kinetic equations of the first or second order, and is described only by complex equations for parallel and consecutive reactions.

Formation and recognition of alkyl xanthyl thiosulphates in sulphide ore flotation liquors

Alkyl xanthyl thiosulphates (R.OCSS.S 2O 3 −) (RXT −) are formed in solution by mild oxidation (e.g. by I 2) of solutions containing both xanthate and thiosulphate. They can also be formed by reaction of Cu 2+ with xanthate and thiosulphate, reaction of dixanthogen with thiosulphate, and by reaction of xanthate with tetrathionate; these last three reactions can occur in flotation pulps in slightly acid or alkaline solutions (pH 5–10). Alkyl xanthyl thiosulphates are stable in acid and neutral solution; the solutions have a UV absorption maximum at 289 nm. In strongly alkaline solution (pH 12) RXT − decomposes within a few minutes to yield a xanthate (mostly) plus a little perxanthate. At pH 10 this decomposition to xanthate takes about 48 h. At pH 7–9 RXT − is relatively stable. RXT − is not extracted from aqueous solution with common solvents (chloroform, iso-octane, cyclohexane, or ether). It forms a water-insoluble adduct with cetyltrimethyl-ammonium bromide (CTAB); this adduct can be extracted into chloroform, and the extract has a UV absorption maximum at 296 nm. RXT − was found in solutions from the gangue-sulphide flotation section at Renison Ltd, the zinc flotation circuit and the copper flotation circuit at Mount Isa Mines Ltd, and the lead flotation section of The Zinc Corporation Ltd. The presence of RXT − in operating flotation plants has various practical and theoretical implications.

Perxanthates — A new factor in the theory and practice of flotation

A compound with a UV absorption maximum at 348 nm was observed in Mount Isa copper flotation plant solution. This spectrum was similar to that of the product of reaction of xanthate and peroxide in dilute, alkaline aqueous solution. The compound was termed perxanthate (more correctly “O”-alkyl dithiomonoperoxycarbonate). A new compound, ammonium sec-butyl perxanthate (C 4H 9 OCSSO·NH 4), was prepared by reacting potassium sec-butyl xanthate and hydrogen peroxide in dilute alkaline solution, acidifying, extracting into iso-octane, and precipitating with anhydrous ammonia. Solutions of this compound were compared with solutions containing the Mount Isa compound. Each compound was found to have the same UV absorption spectrum in a given solvent (alkaline aqueous, acid aqueous, chloroform, iso-octane, iso-amyl alcohol, and n-butyl acetate), but the spectra were different in different solvents (especially in alkaline and acid aqueous solutions). Both compounds could be extracted from acid, but not alkaline, aqueous solutions by organic solvents, and both had similar IR and mass spectra. It was concluded that the perxanthate in plant solution resulted from reaction of xanthate with peroxide derived from reduction of oxygen during flotation. This lends credence to the electrochemical theory of flotation and has some important theoretical and practical implications.

Synthesis and reactions of xanthate and thioxanthate carbonyl complexes of molybdenum and tungsten

A series of complexes CpM(CO) n S 2CX (M = Mo, W; n = 2, 3; X = OR, SR; R = Me, Et) has been prepared by the reaction of xanthates and thioxanthates with CpM(CO) 3Cl. The dicarbonyl compounds are the exclusive products after sufficiently long reaction times and are produced at least partially through the tricarbonyl species as intermediates. The conversion of CpM(CO) 2S 2CX to CpM(CO) 2S 3CX is not a simple first-order process but is catalyzed by Cl − and/or S 2CX −. The tricarbonyl species can be alkylated at the uncoordinated sulfur atom to give ionic di- or tri-thiocarbonate complexes.

Die präparative Chemie derO- undN-funktionellen Orthokohlensäure-Derivate

The methods for the preparation of O- and N-functional orthocarbonic acid derivatives are reviewed, and a survey of the reactions of these compounds with electrophilic and nucleophilic reagents is given. 1. Synthesis of Orthocarbonic Acid Esters 1.1 Reaction of Substituted Trichloromethanes with Alcohols, Alkoxides, Phenols, or Phenoxides 1.2. Reaction of Substituted Dichloromethanes with Alcohols or Phenols 1.3. Reaction of Trialkoxycarbenium Salts with Alkoxides 1.4. Reaction of Cyanic Acid Esters with Alcohols 1.5. Thermolysis of Cyclic Carbonic Acid Derivatives 1.6. Reaction of Carbon Disulfide with Thallium(I) Alkoxides 1.7. Reaction of Carbon Disulfide with Organotin Compounds 1.8. Reaction of Zinc Xanthates with Alcohols 1.9. Transesterification of Orthocarbonic Acid Esters 2. Synthesis of Orthocarbamic Acid Esters 2.1. Reaction of Trihetero-substituted Carbenium Ions with Alkoxides 2.2. Alcoholysis of Tetramethylurea Diethyl Acetal 2.3. Transesterification of Orthocarbamic Acid Esters 2.4. Spirocyclic Orthocarbamic Acid Esters from Organotin Compounds 3. Synthesis of Bis[dialkylamino]-dialkoxymethanes (Tetraalkylurea Dialkyl Acetals) 3.1. Reaction of Bis[dialkylamino]-ethoxycarbenium Tetrafluoroborates with Alkoxides 3.2. Reaction of Tetraalkylurea Dichlorides (Chloroformamidinium Chlorides) with Alcohols or Alkoxides 3.3. Reaction of 2,2-Dichloro-1,3-benzodioxole with Amines 3.4. Spirocyclic Urea Acetals from Organotin Compounds 4. Synthesis of Alkoxytris[dialkylamino]methanes 5. Synthesis of Tetrakis[dialkylamino]methanes 6. Reactions of O- and N-Functional Orthocarbonic Acid Derivatives 6.1. Reactions with Electrophilic Agents 6.2. Reactions with Nucleophilic Agents 6.3. Miscellaneous Reactions of Orthocarbonic Acid Derivatives

Electron-impact and pyrolytic eliminations from 4-tert-butylcyclohexyl xanthates

The stereochemistry of electron--impact induced xanthic acid elimination reactions was assessed by mass spectrographic studies of cis and trans deuterated 4-tert-butylcyclohexyl xanthates and their derivatives. Cis elimination was observed to be about 30 times as facile as trans elimination in the axial xanthate reaction. In the equatorial ester derivative reactions, the cis elimination was found to be slightly preferred. The electron-impact induced elimination results were compared with pyrolytic elimination results for the xanthates; and similar stereochemistry was observed for each type of elimination. (DDA)

Rearrangement and trans-elimination contrary to the chugaev reaction rule. XIII. Solvent effect on rearrangement reaction of allylic xanthates and a correction of the former report.

To provide an additional evidence which confirms the concerted mechanism postulated for the thermal rearrangement reaction of allylic xanthates, the kinetic study on the rearrangement of them was conducted in a variety of solvent. The rearrangement showed a first order process with relatively low sensitivity to the ionizing power of the medium indicating that it proceeds by a mechanism which involves very little change in charge separation between the ground state and the transition state. In addition, this paper includes the correction of the former report referring to the product formation in the thermolysis of cinnamyl S-methyl xanthate.