text: Using the appropriate reagent and conditions, alkyl, alkenyl, allylic, and α-keto sulfones may be reduced in good yield and high stereoselectivity (where applicable). Appropriate conditions for the reduction of these classes of sulfones are discussed below.
  Alkyl sulfones may be reduced with sodium or lithium in liquid ammonia; however, the strongly basic conditions of these dissolving metal reductions represent a significant disadvantage. In alcoholic solvents, magnesium metal and a catalytic amount of mercury(II) chloride may be used. A wide variety of functional groups are unaffected by these conditions, including many that are transformed by dissolving metal reductions. Reductive desulfonylation with these reagents does not occur in reactions of β-hydroxy sulfones, due to the poor leaving group ability of the hydroxyl group.
  A significant issue associated with the reduction of allylic sulfones is transposition of the allylic double bond, which occurs in varying amounts during reductions by metal amalgams. and tin hydrides Palladium-catalyzed reductive desulfonylations of allylic sulfones do not have this issue, and afford allylic sulfones with high site and stereoselectivity.
  Aluminum amalgam (Al/Hg) may be used for the chemoselective reduction of α-sulfonylated carbonyl groups. Carboxylic acid derivatives, acetals, thioacetals, amines, alcohols, and isolated double bonds are all inert to Al/Hg. Selective desulfonylation may be carried out on β-hydroxy sulfones without reductive elimination. 
  Transition metal catalysis is also useful for the stereospecific reduction of alkenyl sulfones. In the presence of an excess of a Grignard reagent, a palladium(II) or nickel(II) catalyst, and a phosphorus or nitrogen ligand, alkenyl sulfones are converted to the corresponding alkenes stereospecifically in good yield. On the other hand, dissolving metal and metal amalgam reductions are not stereoselective in general. Palladium catalysis is generally superior to nickel catalysis, giving higher yields and stereoselectivities.
  Alkyl and alkenyl sulfones with good leaving groups in the β position undergo elimination under reductive conditions to afford alkenes or alkynes. The Julia olefination exploits this process for the synthesis of alkenes from alkyl sulfones and carbonyl compounds. Addition of an α-sulfonyl anion to a carbonyl compound, followed by quenching with an acyl or sulfonyl chloride, leads to a β-acyloxy or -sulfonyloxy sulfone, which undergoes elimination under reductive conditions. Sodium amalgam may be used to accomplish the elimination step; however, the combination of samarium(II) iodide and HMPA is milder than strongly basic sodium amalgam and leads to higher yields in reductive elimination processes.