Reactions of ajS-dinitroolefins with 1,2-ethanedithiol form five-membered ring products. Similarly, reactions of ,/8-dinitroolefins with 2-mercaptoethanol give five-membered ring products along with monosubstituted olefins and products disubstituted on one carbon. The formation of cyclic products from a,d-dinitroolefins and 1,2-difunctional nucleophiles is explained in terms of a stepwise additionsubstitution mechanism in which a carbanion intermediate must be assumed. A Michael-type reaction seems to occur, and the addition intermediate loses a nitro group by intramolecular substitution. The reaction of 1,2-dinitrocyclohexene with 2-mercaptoethanol unexpectedly forms a /S'-substituted -nitroolefin by means of another reaction mechanism.