Conversion of Sulfones to Sulfoxides via Hydride Reduction of (Aryloxy)sulfoxonium Salt Intermediates

Article abstract of DOI:10.1021/jo00158a009

The conversion of sulfones into sulfoxides by a two-stage procedure, involving initial reaction of the sulfone with 4-chlorobenzenediazonium tetrafluoroborate to form an (aryloxy)sulfoxonium salt, R2⁺S(O)OArBF4^-, and subsequent reduction of this with NaBH4*Al2O3, has been investigated.Variations in the nature and amount of the diazonium salt used and its counterion, the temperature of the reaction, and solvent and concentration effects have been investigated in a largely unsuccessful attempt to improve significantly upon the yields in the first stage.It has been found, by using NaBD4, that the hydride reduction of the (aryloxy)sulfoxonium salt in the second stage proceeds mainly by hydride attack at sulfur, rather than by a Pummerer-type mechanism.The latter mechanism, however, does occur when strong base is added to the (aryloxy)sulfoxonium salt prior to hydride reduction.