Hydrogenated product reactions with sulfur, procedure

The production of industrially important perfluoroalkane sulfonic acids is generally accomplished by electrochemical fluorination. This method of preparation remains expensive and proceeds in good yields only for short hydrocarbon chains.30 Recently however, Wakselman and Tordeux have described a chemical method for the preparation of trifluoromethane sulfonic acid.31 The procedure involves reaction of a metal selected from zinc, cadmium, manganese, and aluminum with sulfur dioxide in DMF, followed by the introduction of trifluoromethyl bromide under slight pressure. The intermediate sulfinate is subsequently oxidized by hydrogen peroxide, and then hydrolyzed which leads to formation of the trifluoromethane sulfonic acid. Successful extension of the sulfination process to the modification of PCTFE should result in the formation of a sulfinated polymer which can ultimately be oxidized to give a sulfonic-acid modified polymer. 

If the sulfur dichloride and dissolved hydrogen chloride are not removed, a product contaminated with ammonium chloride will result. An alternative procedure to pumping off the volatile impurities is to allow the assembly to stand 48 hours so that the adhering liquids drain into the reaction flask. This procedure is not as efficient as pumping off the impurities but has the advantage of minimizing exposure of the product to the atmosphere. 

Esters of methacrylic acid are obtained directly from acetone cyanohydrin by reaction of the latter with concentrated sulfuric acid to give methacrylamide sulfate, followed by reaction with an alcohol. The process is continuous and the methacrylamide sulfate is not isolated. Acetone cyanohydrin is derived from acetone and hydrogen cyanide (Pig. 15-39), Polymerization Procedures. Of particular importmice to the acrylics is the cast or bulk method of polymerization. This method is employed to produce cast polymethyl methacrylate sheets which are widely used in industrial applications. Careful control of polymerization is required to obtain a bubble-free product with good optical clarity. A typical flow sheet for the production of cast eet is shown in fig. lfi-40. Solution, suspension, and particularly emulsion polymerizations are also, widely used with the acrylics. Such polymerization reactions involve relatively conventional batch-type processes. i... 

Other sulfur compounds such as thiourea, ammonium dithiocarbamate, or hydrogen sulfide also lead to 2-mercaptothiazoles. Thus thiourea has been used in the syntheses of 4,5-dimethyl (369) and 4-aryl-2-mercapto-thiazoles (Table 11-30) (519). The reactions were carried out by condensing the ia -thiocyanatoketones with thiourea in alcohol and water acidified with hydrochloric acid. By this procedure, 4-aryl-2-mercaptothiazoles were obtained in yields of 40 to 80% with bis-(4-aryl-2-thiazolyl) sulfides as by-products (519). These latter products (194) have also been observed as a result of the action of thiourea on 2-chloro-4-arylthiazole under the same experimental conditions. They can be separated from 2-mercaptothiazoles because of their different degrees of solubility in sodium hydroxide solution at 5%. In this medium bis-(4-phenyl-2-thiazolyl)sulfide is... 

One procedure for the synthesis of these title ring systems appeared recently <2003S1079>. Yadav and Kapoor described that the transformation of some oxadiazole and thiadiazole derivatives bearing specially substituted methylsulfinyl side chain 131, when reacted with thionyl chloride, give ring-closed compounds 134. The reaction was carried out in pyridine under reflux conditions in 74-79% yield. As shown in Scheme 25, the authors assume that the first step is the formation of the sulfonium salt 132 which undergoes cyclization with hydrogen chloride and sulfur dioxide elimination to 133 and, finally, demethylation of this intermediate leads to the final product 134. 

Dimsylsodium (24) functions as a highly basic sulfur ylide. It can be used to convert phosphonium salts to phosphorus ylides for use in the Wittig reaction. Dimsylsodium also reacts with aldehydes and ketones by nucleophilic addition to form epoxides and with esters by nucleophilic substitution to yield p-ketosulfoxides (25) (Scheme 11). The p-ketosulfoxides (25) contain acidic a-hydrogens which can be readily removed to allow alkylation, and the products (26) suffer reductive desulfuration on treatment with aluminium amalgam to yield ketones (27) (Scheme 11) This procedure can, for instance, be applied to the conversion of ethyl benzoate to propiophenone (28) (Scheme 12). 

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