Photooxidation of N-acylhydrazones to 1,3,4-oxadiazoles catalyzed by heterogeneous visible-light-active carbon nitride semiconductor

The remarkable bioactivity of 1,3,4-oxadiazoles permanently motivates chemists to develop new milder and broader approaches to synthesize new derivatives, as well as to improve the preparation methodologies of the known compounds. Potassium poly(heptazine imide), a well crystallized representative of carbon nitrides family, shows great performance as a heterogeneous and hence recyclable photocatalyst in the visible light driven oxidative cyclization of N-acylhydrazones to the corresponding oxadiazoles. The proposed method uses elemental sulfur as a cheap and selective electron scavenger. A series of 2,5-disubstituted-1,3,4-oxadiazoles bearing aryl, hetaryl and alkyl substituents were obtained with 42-84% isolated yield.