Halogen effects in Robinson-Gabriel type reaction of cyclopropanecarboxylic acid N′-substituted-hydrazides with PPh3/CX4

Halogen effects were described in the Robinson-Gabriel type reaction of cyclopropanecarboxylic acid N′-substituted-hydrazides with PPh3/CX4 (X = Cl, Br, I). Cyclopropyl-5-substituted-[1,3,4]oxadiazole (2) and 2-(3-halopropyl)-5-substituted-[1,3,4]oxadiazoles (4 or 5) were obtained, respectively.