Organic Reactions of Reduced Species of Sulfur Dioxide

Article abstract of DOI:10.1021/jo00259a026

Rongalite (sodium hydroxymethanesulfinate or sodium formaldehydesulfoxylate) reacts with organic halides in a variety of ways depending on the structure of the organic compound.Benzyl and other alkyl halides give sulfones in generally good yields; but in several cases, reduction (2,4-dinitrobenzyl bromide, phenacyl halides) or coupling (p-nitrobenzyl bromide under basic conditions, phenacyl bromide or iodide) of the halide occurs.Addition of sodium iodide to the mixture of Rongalite and phenacyl chloride changed the reaction from one of complete reduction to acetophenone to one of mainly dimerization to 1,4-diphenyl-1,4-butanedione.The amount of acetophenone from phenacyl bromide depends on the water content of the reaction mixture, more dimer being formed when little water is present.Diphenacyl sulfone is formed from phenacyl bromide and Rongalite in the presence of excess sulfur dioxide.The intermediate β-keto sulfinate is believed to normally lose sulfur dioxide very readily to give the enolate anion, which either is protonated to give acetophenone or reacts with phenacyl halide to give the butanedione.In the presence of excess sulfur dioxide, the loss of sulfur dioxide from the sulfinate is supressed, allowing sulfone formation to occur by reaction of the sulfinate with phenacyl halide. o-Xylylene dibromide gave o-xylylene, trapped as the Diels-Alder adduct with norbornene, along with the expected cyclic sulfone and cyclic sulfinate ester (sultine).A convenient synthesis of the sultine in 78percent yield is achieved by treatment of α,α'-dichloro-o-xylene with Rongalite and sodium iodide.Treatment of Rongalite in DMF-H2O with sulfur dioxide gives the blue anion radical complex (SO2)(SO2^.-).Anion radicals are produced from p-dinitrobenzene and p-nitrobenzoate ion when they are treated with Rongalite.