In the studies on oxime ether derivative synthesis, a serendipitous reactivity of dihydropyrroloimidazol-6-ones has been observed. Instead of expected oxime ethers, a new class of 1,2-dioxime ether derivatives with nitromethylene imidazolidine subunit were prepared in moderate to good yields. In this reaction, the adjacent carbon of carbonyl, but not the carbonyl, was preferentially attacked by oxyamine. The methodology has been applied on a wide range of oxyamine hydrochlorides, such as alkoxyamine hydrochlorides and benzyloxyamine hydrochlorides.