Sulfur-containing Reagents Research Articles

Isobutane dehydrogenation over sulfided nickel catalysts

We have studied the dehydrogenation of isobutane to isobutylene over heavily sulfided Ni catalysts at 873 K. In the absence of sulfur but in the presence of hydrogen, supported metallic nickel catalyzes the rapid hydrogenolysis of alkanes, resulting in exceedingly poor selectivity toward dehydrogenation products. However, the hydrogenolysis activity can be essentially eliminated by proper sulfidation, resulting in high selectivity toward isobutylene production. Due to thermodynamic limitations, elevated temperatures are necessary to attain reasonable conversions to isobutylene. Under these conditions, the formation of coke is rapid and is the main cause of catalyst deactivation. Treatment of nickel catalysts with relatively large amounts of sulfur-containing reagents results not only in dramatically improved selectivity but also in a decreased rate of coke formation. The catalysts exhibited activation periods of several hours until a maximum was reached when they were placed in the reaction environment at 873 K. This activation period did not depend upon the previous reduction treatment but did depend upon the time on stream. A correlation was found between the increase in activity and the growth of a carbidic phase on the catalyst. This species, characterized by TPO and XPS, reached a saturation value at a C/Ni ratio of unity, which was coincidental with the amount of carbon on the catalyst when it achieved its maximum activity. Two alternative explanations for the activation process are discussed. The first considers the participation of a nickel-carbidic-carbon complex in the reaction scheme. The second considers the creation of sulfur vacancies during the initial coke deposition period which would increase the exposure of a catalytically active NiS moiety.

New Xanthic Acid Derivative as Selective Reagent for the Solvent Extraction of Palladium

Abstract Trimethylene-bis(n-butyl)xanthate (TrMBnBX) has been synthesized as a new sulfur-containing reagent for the extraction of precious metal ions. This compound exhibited high selectivity for extraction of Pd(II) and Ag(I) ions in dichloroethane, over Pt(IV), Au(III) and most of the base metal ions. A mixed aqueous system containing H2SO4 in presence of small amount of chloride ions provides the maximum extraction of Pd(II), where it forms a 1:1 complex with TrMBnBX.

SOLVENT EXTRACTION OF MERCURY(II) WITH SOME SULFUR-CONTAINING EXTRACTING REAGENTS

ABSTRACT A few novel kinds of sulfur-containing extracting reagents, i.e. 2-ethyl-2-(isobutylthiomethyl)butanethiol (EIBTMBT), 3,3-diethylthietane (DETE) and 3,3-di-butylthietane (DBTE), were synthesized to investigate their extraction behaviors for mercury(II) from acidic chloride media at 303 K and compared with that of di-hexylsulfide (DHS), a conventional sulfur-containing extracting reagent. 1,2-dichloroethane was used as a diluent for all reagents. Mercury(II) was found to be extracted with DETE and DBTE according to solvation reaction mechanism as 1:2:2 metahchloride ion:reagent complexes as well as with DHS as follows: The evaluated extraction equilibrium constants for DETE and DBTE were virtually the same, i.e. Kc = 2.3, regardless of the Length of the alkyl radicals and, surprisingly, less than that for DHS (Kc =7.3). On the other hand, it was found to be extracted with EIBTMBT as a 1:2 metal:reagent chelate according to the following extraction reaction:

Synthesis of 4,5-disubstituted imidazolinones-2

1. 4-Methyl-5-(α-oxo-Β-bromo-e-ethoxycarbonylpentyl)imidazolinone-2 reacts with diethylamine with migration of the electrophilic reaction center to give 4-diethylaminomethyl-5-(α-oxo-e-ethoxycarbonylpentyl)imidazolinone-2. 2. Sulfur-containing nucleophilic reagents and potassium benzoate enter into a nucleophilic substitution reaction with 4-methyl-5-(α-oxo-Β-bromo-e-ethoxycarbonylpentyl)imidazolinone-2 without migration of the reaction center. 3. Direct conversion of 1,3-diacetyl-4-acetoxymethyl-5-(α-oxo-e-ethoxycarbonylpentyl)imidazolinone-2 to 4-methoxymethyl-5-(α-oxo-e-methoxycarbonylpentyl)imidazolinone-2, an intermediate product in the synthesis of the methyl ester of 3,4-dehydrobiotin, is realized by the reaction with a solution of sulfuric acid in methanol.

Nitromethane-lithium perchlorate system as an effective stimulator for skeletal rearrangements in AdE reactions of sulfur-containing reagents

Nitromethane-lithium perchlorate system as an effective stimulator for skeletal rearrangements in AdE reactions of sulfur-containing reagents

ChemInform Abstract: SULFUR‐CONTAINING REAGENTS IN ORGANIC SYNTHESIS

Chemischer InformationsdienstVolume 15, Issue 13 Reviews ChemInform Abstract: SULFUR-CONTAINING REAGENTS IN ORGANIC SYNTHESIS A. SENNING, A. SENNINGSearch for more papers by this author A. SENNING, A. SENNINGSearch for more papers by this author First published: March 27, 1984 https://doi.org/10.1002/chin.198413383AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume15, Issue13March 27, 1984 RelatedInformation

Stereospecifïc total synthesis of (±)-cassipurine, an alkaloid from rhizophoraceae

Two isomeric 1α,2α-epoxy- and 1β,2β-epoxypyrrolizidines have been obtained from 1,2-dehydropyrrolizidine. The structure of both isomers has been determined enabling a study of the stereochemistry of their reactions with a number of sulfur-containing nucleophilic reagents. The BzS− anion has been shown to stereospecifically attack the C2 carbon atom of both compounds. In the three-stage process 1β,2β-epoxypyrrolizidine was transformed into 1α,2α-epithiopyrrolizidine, which reacts stereospecifically with benzylthiol to yield 1α-(2β-thiobenzylpyrrolizidine)-thiol. This, in turn, oxidizes in air to give a mixture of three diastereomeric 1α,1′α-dithio-2β,2′β-dithiobenzyldipyrrolizidines. These diastereomers were chromatographically separated into the racemic mixture and the meso diastereomer. Treatment of the racemic mixture with Na/liquid NH3 induced debenzylation without cleavage of the disulfide bond. The resulting enantiomeric α,1′α-dithio-2β,2′β-dimercaptodipyrrolizidines were oxidized in air to give racemic cassipurine.

Umpolung of the Reactivity of Carbonyl Compounds Through Sulfur-Containing Reagents

The synthetic usefulness of the umpolung of the reactivity of carbonyl compounds by reaction of sulfur-containing reagents is discussed. Firstly, hydrolysis and other reactions of S, S-acetals (mainly 1,3-dithianes) and vinyl sulfides are described. The second part is concerned with the reactions of other sulfur-containing reagents such as derivatives of vinyl sulfides, ketene S,S-acetals and derivatives, etc. Finally the applications of the methods to the syntheses of natural products are briefly mentioned. 1. Introduction 2. Hydrolysis of S,S-Acetal and Vinyl Sulfide Derivatives and other Desulfurization Reactions 2.1. Acidic Hydrolysis and Transacetalization 2.2. The Transition Metal-Induced Hydrolysis 2.3. Oxidative and Alkylative Hydrolysis of S,S-Acetals 2.4. Oxidative Solvolysis of Vinyl Sulfides and Ketene S, S-Acetals 2.5. Reductive Desulfurizations 3. Reactions of S,S-Acetal Derivatives (E1-Type) 3.1. Metallated 1,3-Dithianes 3.2. Use of Metal Derivatives of S,S-Acetals other than 1,3-Dithianes 3.3. S,S-AcetalS-Oxides: Alkylation, Cycloalkylation, Arylation, Hydroxyalkylation, and Acylation Reactions 3.4. Reactions of Metallated S,S-Acetals with Heteroelectrophiles 3.5. Michael-Addition of S,S-Acetal Metal Derivatives 4. Miscellaneous Sulfur-Containing Reagents 4.1. Nucleophilic Acylations with Diheterosubstituted Anionic Reagents (XYRC-) 4.2. Reactions of (RS)3C- -Reagents and of Thioformyl Anions with Electrophiles 4.3. Umpolung of Carbonyl Reactivity with α-Phenylsulfonyl Nucleophiles and with Sulfur-Substituted Cyclopropanes 5. The Use of Vinyl Sulfides and Ketene S,S-Acetal Derivatives (E1-, N2--, N4-Type Reactions) 5.1. Generation and E1-Reactions of α-Lithiovinyl Sulfides 5.2. Derivatives of Ketene S, S-Acetals 5.3. Survey of Useful Transformations through Vinyl Sulfides and Ketene S, S-Acetals 6. Applications of Sulfur-Substituted Allylic Anions (E3-, E5-Type) 7. Natural Product Synthesis 7.1. 1,4-Diketone Synthesis: Access to Jasmonoids, Rethrolonoids, and Prostanoids 7.2. Use of 2-Lithio-1,3-dithianes in Carbohydrate Synthesis 7.3. Other Natural Product Syntheses

Stereospecific addition of sulfur-containing electrophiles to a trisubstituted double bond

On the example of the reaction for the cylization of the D3-analog of geranic ester under the influence of sulfur-containing reagents it was shown that the addition of these reagents to a trisubstituted double bond is stereospecific.

Synergistic effects in the solvent extraction of chelate compounds: Influence of the donor atoms of the reagent

The solvent extraction of zinc has been investigated in the form of chelate compounds with 2-thenoyltrifluoracetone, 1-phenyl-1-methyl-4-benzoylpyrazolone-5, 1,5-diphenylcarbazone, 8-mercaptoquinoline, 1,5-diphenylthiocarbazone (dithizone) and diethyldithiocarbamate. Benzene was used as diluent. Extraction of the above compounds in the presence of tri-n-butylphosphate has also been studied. A synergistic effect was observed for the extraction of complexes of the first three reagents, its magnitude decreasing in the indicated sequence. When using sulfur-containing reagents, the effect was completely absent. This may be accounted for by the difference in the zinc coordination number in these chelates. It is assumed that the coordination number of the metal ion in chelates studied is the lower the stronger the metal-reagent bond.