A New Route to Substituted Guanidines

IN a recent communication1, the reaction between hydrazine and a 1-formimino-pyrazole (I) was reported. It was found that molecular cleavage resulted, the products being a substituted hydrazine and a 1-unsubstituted pyrazole. This rearrangement occurs either by cleavage of the 1-substituent with its attachment to the hydrazine (mode A), or by initial ring opening, with subsequent displacement of the aminoguanidine derivative from the resulting hydrazone (mode B).