Sulfonated grapheneoxide as a sustainable metal free acid catalyst: a smart approach for synthesizing 1, 3, 4-oxadiazole derivatives from carboxylic acids: antimicrobial activities

Using metal free solid acid catalyst in chemical reactions is essential for the development of a new organic synthesis approach. Herein, we demonstrate the use of sulfonated reduced graphene oxide (GO-SO3H, SGO) metal free catalyst, which is emerging as a popular catalyst. The metal free catalyst was prepared as an anchored aryl diazonium salt of sulfanilic acid free radicals onto its surface by sonication. As such synthesized SGO catalyst was structurally elucidated by various analytical techniques. An effective one-pot synthesis of 2, 5-diarylsubstituted1, 3, 4-oxadiazoles was reported here. Initially, benzohydrazides were condensed with substituted carboxylic acids in the presence of O-(benzotriazol-1-yl)-N, N, Nʹ, Nʹ-tetramethyluronium tetrafluoroborate (TBTU) to obtain diacylhydrazine. Later, the diacylhydrazines underwent sulfonated graphene oxide (SGO) catalyzed cyclodehydration reaction to obtain targeted heterocyclic molecules. This work exemplifies numerous benefits in work-up methods and environmental friendliness. The obtained 1,3,4-oxadiazoles were evaluated successfully for their antibacterial activities. SGO attracts the scientific community and its catalytic applications in synthesis of 1,3,4-oxadiazoles and other organic transformations.