Aryl azides undergo a [3+2]-cycloaddition with 1,1-diaminoethenes having an electron-withdrawing group at C-2 to give unstable 5,5-diamino-4,5-dihydro-1,2, 3-triazoles from which one amino group is eliminated to afford 5-amino-1-aryl-1, 2,3-triazoles functionalized at C-4.