Electrocatalysis in MIRC reaction strategy: facile stereoselective approach to medicinally relevant spirocyclopropylbarbiturates from barbituric acids and activated olefins

Abstract

The combined electrolysis of barbituric acids and benzylidenemalononitriles or benzylidenecyanoacetates in methanol in an undivided cell in the presence of sodium bromide results in efficient MIRC (Michael-initiated ring-closure) formation of the corresponding spirocyclopropylbarbiturates in 45–93% yield. The electrocatalytic reaction proceeds smoothly under neutral and mild conditions with benzylidenemalononitriles or benzylidenecyanoacetates bearing both electron-donating and electron-withdrawing groups. NMR and single X-ray diffraction studies indicate that the electrocatalytic MIRC transformation of barbituric acids and benzylidenecyanoacetates results in the stereoselective formation of spirocyclopropanes with an (E)-configuration of aryl and alkoxycarboxylate substituents. The implication of electrocatalysis in the MIRC reaction strategy allows the combination of the synthetic virtues of both methods and accounts for an efficient approach to medicinally relevant spirocyclopropylbarbiturates avoiding inconvenient direct use of molecular halogen or halogenated substrates in accordance with the concepts of modern green chemistry.