Umpolung of <i>N</i>-Tosylhydrazones: Synthesis of <i>N</i>-Cyano Tosylhydrazones and Their [3,3]-Sigmatropic Rearrangement to 2-Aminoimidazoles

The umpolung of <i>N</i>-tosylhydrazones was reported for the first time. Synthesis of <i>N</i>-cyano tosylhydrazones was developed, and various <i>N</i>-cyano tosylhydrazones were prepared in good yields. An umpolung <i>N</i>-tosylhydrazones mechanism was proposed. Meanwhile, the [3,3]-sigmatropic rearrangement of <i>N</i>-cyano tosylhydrazones was examined, and the corresponding 2-aminoimidazoles were given.