Direct synthesis of N2-unprotected five-membered cyclic guanidines by regioselective [3 + 2] annulation of aziridines and cyanamides

This work disclosed the first direct synthesis of N 2 -unprotected five-membered cyclic guanidines via a regioselective ring-opening/5- exo-dig cyclization strategy between aziridines and cyanamides under mild conditions.