Recent studies on organic synthesis mediated by radical species of peroxysulfur compounds

Abstract

Reaction of superoxide ion (O2(-.)) with o-nitrobenzenesulfonyl chloride yields a material with strong oxidizing ability, capable of oxidizing benzylic methylenes to the aryl ketones, benzylic ethers to benzoic esters, hydrazones to ketones, and electron deficient alkenes regioselectively to epoxides. The oxidizing species is tentatively assigned the o-nitrobenzenesulfonyl peroxy radical structure 1. Tetrabutylammonium hydrogen sulfate, on treatment with potassium persulfate under phase transfer conditions, gives tetrabutyl ammonium peroxydisulfate 2, a new oxidizing agent capable of oxidizing primary and secondary alcohols to the corresponding aldehydes and ketones in almost quantitative yields in aprotic solvents under anhydrous conditions; 2 is evidently a source of tetrabutylammonium sulfate radical 3. Further reactions include formation of the tetrahydropyranyl or tetrahydrofuranyl ether derivatives on reaction with alcohols, regioselective iodinations of anisyl derivatives, and alpha,beta-unsaturated ketones or esters, nucleophilic epoxidations of alpha,beta-unsaturated ketones, and an interesting addition of the 1,3-dioxolanyl group to electron deficient alkenes, including a conversion of 1-nitrocyclohexene into a masked alpha-formylcyclohexanone.