Hydrogenolysis of sulfur compounds

The reactions involving the hydrogenolysis of sulfur compounds encountered in hydroprocessing are exothermic and thermodynamically complete under ordinary operating conditions. The various molecules have very different reactivity, with mercaptan sulfur much easier to eliminate than thiophene sulfur or di-benzothiophene sulfur. 

Aluminum amalgam (Al/Hg) is also a useful reagent that is most commonly employed for hydrogenolysis of sulfur compounds.533 Reduction of sulfoxides is an important application,534 as is reduction of sulfones. Aluminum amalgam reduces the a-phenylsulfonyl moiety in 554 to give lactone 555 in 68% yield.535 Aluminum amalgam has also been used for reduction of nitro compounds to the amine,536 and reduction of azides to the amine.532... 

Although nearly aU unsaturated groups can be reduced with Raney nickel, this catalyst is most frequently used for the hydrogenolysis of sulfur compounds such as disulfides, thioacetals and thioamides. When freshly prepared, it contains 20-100 mL absorbed hydrogen per gram of nickel. The bound hydrogen can be partially replaced with tritium by... 

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