Thermolysis of furoxans annulated with five-membered carbocycles in the presence of dipolarophiles

The conditions for the thermolysis of furoxans annulated with differently strained five-membered carbocycles (cyclopentafuroxan 1, norbornenofuroxan 2, and acenaphthofuroxan 3) to bis(nitrile oxides) in the presence of various dipolarophiles (diethyl acetylenedicarboxylate, benzoylformonitrile, and ethoxycarbonylformonitrile) were optimized. It was found that the reactivities of the above furoxans as sources of bis(nitrile oxides) decrease in the order 2 > 1 > 3. Among the furoxans studied, only norbornenofuroxan 2 can be recommended as a possible cross-linking reagent for polymers. The formation of di-N-oxides of 3,4-bis(cyanopropyl)-, 3,4-bis(cyanocyclopentyl)-, and 3,4-bis(cyanonaphthyl)furoxans was detected. They resulted from intermolecular cyclodimerization of bis(nitrile oxides) initially formed in the thermolysis of furoxans 1–3.