Synthesis of hetarylsulfanyl- and hetaryloxyfuroxans by nucleophilic substitution of nitro group in nitrofuroxans with heterocyclic thiol and hydroxy derivatives

We report a general method for the synthesis of previously unknown heterocyclic systems containing furoxan and heterocyclic fragments linked by S- and D-bridges, based on nucleophilic substitution of nitro group in 4-nitrofuroxans with HetS and HetO groups introduced by reactions with hetarylthiols and hydroxy heterocycles in 1,8-diazabicyclo[5.4.0]undec-7-ene/DeD mu CN system at room temperature. We showed that hetarylthiols reacted with 4-nitrofuroxans containing aliphatic, benzyl, and aromatic substituents at the ring D-3 atom, allowing to obtain a library of previously unknown hetarylsulfanylfuroxans, while the reaction with hydroxy heterocycles was successful only in the case of 4-nitro-3-phenylfuroxan, the rest of the nitrofuroxans showing low reactivity, and substitution products could be obtained only in certain cases. 4-Nitrofuroxans with electron-withdrawing substituents (NO2, CONH2) acted as oxidants, forming 1,2-di(hetaryl)disulfides.