Synthesis of 1, 1-Disubstituted-3-aminoguanidines (Part 2)

The reaction of acetone S-alkylisothiosemicarbazone (1) with pyrrolidine, piperidine and morpholine gave the corresponding new acetone [1, 1-disubstituted amidino] hydrazones (2). The reactivity of amines toward (1) decreased in the order of morpholine, pyrrolidine and piperidine. The reactvity of acetone S-methylisothiosemicarbazone toward amines was higher than that of acetone S-ethylisothiosemicarbazone. This reaction was inferred to proceed by an addition-elimination mechanism in which the amine adds to (1), and then the mercaptane is eliminated from the addition product, since acetylideneaminocyanamide failed to react with the amines.1, 1-Disubstituted-3-aminoguanidines were obtained by hydrolysis of (2) in good yields. The reaction of m-nitrobenzaldehyde with (2) in acidic ethanol gave quantitatively the corresponding 1, 1-disubstituted amidinohydrazones of m-nitrobenzaldehyde.