Pyridinium bromide as a mediator in electrochemical reactions: the preparation of cyclopropane-1,1-dicarbonitriles

Abstract

Pyridinium bromide has been tested as a new mediator for electrochemical transformations in methanol and acetonitrile. An efficient protocol for the synthesis of cyclopropanes via the electrochemical transformations of alkylidenemalononitriles and C-H acids (malononitrile, malonic ester, N,N-dimethylbarbituric acid, pyrazolin-5-ones) has been developed. The chemistry proceeds in a simple undivided cell under constant current conditions employing a substoichiometric amount of PyHBr that serves both as a redox catalyst and a supporting electrolyte; in this manner additional conducting salt is not required.