Sulfides, allylic chemoselective oxidation

A recent method for the highly chemoselective oxidation of sulfides to sulfones using Af-methylmorpholine IV-oxide (NMP) and a catalytic perruthenatc was found to be also applicable in the presence of isolated or allylic double bonds [115]. 

An interesting example of this type of chemoselective oxidation has been reported with the reagent mixture derived irom (Uisopropyl sulfide and )V-chlorosuccinimide. This reagent will oxidize selectively a primary alcohol to an aldehyde at 0 C. Surprisingly, this same reagent at -78 C will oxidize selectively a secondary alcohol to the corresponding ketone (Scheme 2). Allylic and benzylic alcohols are oxidized at both temperatures. 

We shall be using [2,3] sigmatropic shifts in the reactions of allylic alcohols so this section is an introduction to that as well as describing perhaps the most tightly controlled method for making allylic alcohols. Allylic sulfides 40 are easily oxidised chemoselectively with reagents such as sodium periodate to the corresponding sulfoxides 41. More powerful oxidants tend to form the sulfone 42. 

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