Steric factors in heterocyclic rearrangements. N-Methyl-N-phenylhydrazones of 3-benzoyl-5-phenyl-1,2,4-oxadiazole

Abstract

In acetic acid at room temperature, the (E)- and (Z)-N-methyl-N-phenylhydrazones of 3-benzoyl-5-phenyl-1,2,4-oxadiazole rearranged into 4-benzoylamino-2,5-diphenyl-1,2,3-triazole via demethylation of an intermediate triazolium salt. When refluxed in benzene, the (E)-N-methyl-N-phenylhydrazone (8E) gave 3-benzoylamino-1-methylindazole (17) through prior isomerisation to the unisolated Z-isomer (8Z) and thence via a carbodi-imide intermediate derived from cleavage of the ring O–N bond.