Sulphides synthesis

Preparation.—In addition to a number of reactions of thiols, discussed in the preceding section, a variety of other routes have been explored for the preparation of sulphides. U.v. irradiation of thiolesters gives mixtures (CHa CO SPh gives PhSH, PhSMe, o- and p-AcPhSH, and disulphides as major products), while addition of an alkyl halide to a thiolester in the presence of strong base (LiH, PhgCLi, etc.) provides a one-step route. A novel /3-keto-sulphide synthesis from a 1,2-diketone is illustrated by the conversion of (29) into (30). ° Alternative routes to jS-keto-sulphides often... 

Alkylation of thiols is represented by their reaction with O-alkyl NN-di-cyclohexylureas at 100—110 and -keto sulphide synthesis using CF3-... 

S Ag"" and a-bromoketones an alternative route to -keto-sulphides employs an aldehyde and LiCH(SPh)2, and treatment of the adduct with MeLi. Sulphur ylides are now shown to be capable of acting as C—S transfer agents, in addition to their well-known ability to alkylate through carbon. Among five products from cyclopropenium cations and are a 3-methylthio-cyclobutene and a 3-methylthiomethyl-cyclopropene. The use of Bunte salts in sulphide synthesis is illustrated by the synthesis of 1- of 2-naphthyl sulphides from the naphthols with sodium benzylthiosul-phate. ... 

Hydrogen sulphide is used in the preparation of metal sulphides, oil additives ete., in the purifieation and separation of metals, as an analytieal reagent and as raw material in organie synthesis. It burns in air with a blue flame ... 

II. SYNTHESIS OF ACHIRAL AND RACEMIC SULPHOXIDES A. Oxidation of Sulphides... 

The oldest and generally applied sulphoxide synthesis consists of the oxidation of sulphides to sulphoxides. This reaction was reported for the first time by Marcker9 as early as 1865. He found that treatment of dibenzyl sulphide with nitric acid afforded the corresponding dibenzyl sulphoxide in a high yield. Since that time the oxidation of... 

The use of optically active peracids for asymmetric oxidation of sulphides will be discussed in Section III dealing with the synthesis of optically active sulphoxides. 

Oxidation of phenyl hexyl sulphide with sodium metaperiodate gave also only a trace amount of the corresponding sulphoxide72. On the other hand, Hall and coworkers73 prepared benzylpenicillin and phenoxymethyl penicillin sulphoxides from the corresponding benzyl esters by oxidation with sodium metaperiodate in dioxane solution with a phosphate buffer. A general procedure for the synthesis of penicillin sulphoxides was reported later by Essery and coworkers74 which consists in the direct oxidation of penicillins or their salts with sodium metaperiodate in aqueous solution at pH 6.5-7.0. 1-Butadienyl phenyl sulphoxide 4475 and a-phosphoryl sulphoxides 4576 were also prepared by the same procedure. 

Photochemical synthesis of sulphoxides was reported for the first time by Foote and Peters111 in 1971. They found that dialkyl sulphides undergo smoothly dye-photosensitized oxidation to give sulphoxides (equation 32). This oxidation reaction has been postulated to proceed through an intermediate adduct 63, which could be a zwitterionic peroxide, a diradical or cyclic peroxide, which then reacts with a second molecule of sulphide to give the sulphoxide (equation 33). 

Strecker153 reported in 1910 that the reaction of thionyl chloride with two equivalents of phenylmagnesium bromide or benzylmagnesium bromide afforded diphenyl or dibenzyl sulphoxides, respectively (equation 49 Table 8). The corresponding sulphides are formed as by-products of this reaction. Recently, other sulphoxides were prepared by this procedure154,155. It should be pointed out that this rather simple approach to the synthesis of symmetrical sulphoxides has not yet found wider application. 

A closely related asymmetric synthesis of chiral sulphoxides, which involves a direct oxidation of the parent sulphides by t-butylhydroperoxide in the presence of metal catalyst and diethyl tartrate, was also reported by Modena and Di Furia and their coworkers-28-7,288 jjje effect 0f the reaction parameters such as metal catalyst, chiral tartrate and solvent on the optical yield does not follow a simple pattern. Generally, the highest optical purities (up to 88%) were observed when reactions were carried out using Ti(OPr-i)4 as a metal catalyst in 1,2-dichloroethane. 

Chiral alcohols have also been used in an asymmetric synthesis of sulphoxides based on halogenation of sulphides. Johnson and coworkers have found319 that the reaction of benzyl p-tolyl sulphide with JV-chlorobenzotriazole (NCBT) followed by addition of (—) menthol and silver tetrafluoroborate afforded diastereoisomeric menthoxysulphonium salts 267 which, upon recrystallization and hydrolysis, gave benzyl p-tolyl sulphoxide with 87% optical purity (equation 145). More recently, Oae and coworkers reported320 that optically active diaryl sulphoxides (e.e. up to 20%) were formed either by hydrolysis or thermolysis of the corresponding diaryl menthoxysulphonium salts prepared in situ from diaryl sulphides using ( —) menthol and t-butyl hypochlorite. 

Van t Hoff t-factors 565 Vinylallenes rearrangement of 748 synthesis of 737 Vinyl carbonium ions 620 17a-Vinyl-17/f-hydroxysteroids, epimerization of 735 Vinyl sulphides, as alkyl sulphoxide reduction products 930, 932 Vinyl sulphones - see also Alkenyl... 

The application of ly transition metal carbides as effective substitutes for the more expensive noble metals in a variety of reactions has hem demonstrated in several studies [ 1 -2]. Conventional pr aration route via high temperature (>1200K) oxide carburization using methane is, however, poorly understood. This study deals with the synthesis of supported tungsten carbide nanoparticles via the relatively low-tempoatine propane carburization of the precursor metal sulphide, hi order to optimize the carbide catalyst propertira at the molecular level, we have undertaken a detailed examination of hotii solid-state carburization conditions and gas phase kinetics so as to understand the connectivity between plmse kinetic parametera and catalytically-important intrinsic attributes of the nanoparticle catalyst system. 

Grignard reactions have been used in the preparation of l-(dialkyl-phosphinyl)- ,3-dienes, e.g. (11), which are intermediates in the synthesis of antiflame polymers. Double-resonance n.m.r. techniques have been applied to the study of the reactions between thiophosphoryl halides and Grignard reagents. For example, the reaction between methylmag-nesium iodide and t-butyldibromophosphine sulphide gave the mixed... 

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