A transition metal-free approach towards synthesis of -carboline tethered 1,3,4-oxadiazoles via oxidative C-O bond formation

An efficient protocol has been developed for one-pot synthesis of biologically interesting -carboline substituted 1,3,4-oxadiazoles via an I-2-assisted oxidative C-O bond formation strategy. This metal-free sequential approach is found to be compatible with diversely substituted 1-formyl -carbolines and aromatic as well as aliphatic hydrazides, providing access to a variety of multifunctional -carboline linked 1,3,4-oxadiazole derivatives in good to excellent yields. The methodology was found to be applicable to gram scale synthesis of -carboline substituted 1,3,4-oxadiazole derivatives. Additionally, -carboline C1 linked 2-amino-1,3,4-oxadiazoles and bis-1,3,4-oxadiazoles were also synthesized using the same strategy.