Direct Annulation of Hydrazides to 1,3,4-Oxadiazoles via Oxidative C(CO)–C(Methyl) Bond Cleavage of Methyl Ketones

A new strategy for the synthesis of 1,3,4-oxadiazoles was established through direct annulation of hydrazides with methyl ketones. It was found that the use of K2CO3 as a base achieves an unexpected and highly efficient C-C bond cleavage. This reaction is proposed to go through oxidative cleavage of Csp(3)-H bonds, followed by cyclization and deacylation.