Alkenes with hydrogen sulfide

Acid-Gatalyzed Synthesis. The acid-catalysed reaction of alkenes with hydrogen sulfide to prepare thiols can be accompHshed using a strong acid (sulfuric or phosphoric acid) catalyst. Thiols can also be prepared continuously over a variety of soHd acid catalysts, such as seoHtes, sulfonic acid-containing resin catalysts, or aluminas (22). The continuous process is utilised commercially to manufacture the more important thiols (23,24). The acid-catalysed reaction is commonly classed as a Markownikoff addition. Examples of two important industrial processes are 2-methyl-2-propanethiol and 2-propanethiol, given in equations 1 and 2, respectively. 

Alkenes (Olefins) and Cycloalkenes. Olefins are unsaturated and highly reactive. Because of their propensity to be reduced to paraffins w ilh hydrogen or to merceptans with hydrogen sulfide, alkenes are found in petroleum only in very low concentrations. Single-ring cycloalkenes have the same formula, as olefins and so are difficult... 

Both anhydrous and hydrated sodium or potassium sulfide in ethanol have been used in the synthesis of thietanes. A common procedure is to use a solution of sodium or potassium hydroxide saturated with hydrogen sulfide. Liquid ammonia has been used as a solvent for the preparation of thietane (32%) from sodium sulfide and 1,3-dibromopropane. Phase-transfer catalysis has been used to good effect.A variation in which l,3-dichloro-3-methylbutane 3 is treated with aluminium chloride and hydrogen sulfide followed by aqueous sodium hydroxide gave 2,2-dimethylthietane 4 in 90% yield. An intermediate aluminium chloride-alkene complex, 5 or 6, was proposed. 

Active oxygen transfer in the reactions of aldehydes and alkenes with hydrogen peroxide in carboxylic acid medium is possible both via catalyst and via carboxylic acid.220 Micellar effects on the cobalt(II)-catalysed oxidation of jn-nitroso-lV,lV-dialky-lanilines by H2O2 have been studied with a variety of surfactants of different charge types. Acid-catalysed oxidations of aryl sulfides and phosphorus esters of thiols with... 

Electron-deficient alkenes add stereospecifically to 4-hydroxy-THISs with formation of endo-cycloadducts. Only with methylvinyl-ketone considerable amounts of the exo isomer are produced (Scheme 8) (16). The adducts (6) may extrude hydrogen sulfide on heating with methoxide producing 2-pyridones. The base is unnecessary with fumaronitrile adducts. The alternative elimination of isocyanate Or sulfur may be controlled using 7 as the dipolarenOphile. The cycloaddition produces two products, 8a (R = H, R = COOMe) and 8b (R = COOMe, R =H) (Scheme 9) (17). Pyrolysis of 8b leads to extrusion of furan and isocyanate to give a thiophene. The alternative S-elimi-nation can be effected by oxidation of the adduct and subsequent pyrolysis. 

A substantial portion of fhe gas and vapors emitted to the atmosphere in appreciable quantity from anthropogenic sources tends to be relatively simple in chemical structure carbon dioxide, carbon monoxide, sulfur dioxide, and nitric oxide from combustion processes hydrogen sulfide, ammonia, hydrogen chloride, and hydrogen fluoride from industrial processes. The solvents and gasoline fractions that evaporate are alkanes, alkenes, and aromatics with relatively simple structures. In addition, more complex... 

The mesoionic compound 54 reacts with acetylenic and olefinic dipolaro-philes to give l-methyltriazolopyridin-5-ones (5S).69 With the acetylenes sulfur is eliminated from the bridged intermediate, and with the alkenes hydrogen sulfide is eliminated. 

The intramolecular addition of thiols to alkenes provides a novel entry into heterocycles. One example of this is the reaction of hydrogen sulfide with various nonconjugated dienes to form six-membered rings (equation 302).549 550... 

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