Preparation of α-diazo-β-disulphones; a novel sulphinate elimination in their coupling reactions

Abstract

Bisarylsulphonyldiazomethanes are most conveniently prepared by the addition of a bisarylsulphonylmethane in aqueous ethanol containing 1 equiv. of sodium hydroxide to 3 mol. equiv. of toluene-p-sulphonyl azide. The reverse order of addition, with equimolar amounts of reactants as suggested by Klages and Bott, is unsatisfactory, since under these conditions the first-formed diazodisulphone undergoes secondary reactions, a major product of which is the bisarylsulphonyiformaldehyde hydrazone (XI). In anhydrous tetrahydrofuran, α-diazo-β-disulphones react with 2 mol. Equiv, of the sodium salt of a β-disulphone to provide a vinylhydrazone and sodium arenesulphinate. The latter must arise exclusively from the carbanion since interaction of bisphenylsulphonyldiazomethane (V; Ar = Ph) and the carbanion from the 2,4-xylyl disulphone (II; Ar = 2,4-xylyl) yields exclusively sodium 2,4-xylenesulphinate whilst a similar reaction between bis 2,4-xylylsulphonyldiazomethane and the carbanion from the phenyl disulphone (II; Ar = Ph) provides only sodium benzenesulphinate. In contrast, sulphinate elimination occurs from the diazo-compound when it is coupled with a carbanion containing carbonyl rather than sulphonyl groups. The mechanism of the reactions is discussed.