4-Guanylsemicarbazide dihydrochloride from 1-guanyl-2-nitro-urea - by redn with zinc in hydrochloric acid and then increasing the acid concn

摘要

4-Guanyloemicarbazide dihydrochloride (I) (HN=C(NH2)-NH-CO-NH-NH2.2HCl) is prepd. by (a) reducing 1-guanyl-2-nitrourea (II) with Zn in aq. HCl at ca. 0 degree C, and (b) increasing the HCl content of the reaction soln. to 15-40 wt.% at 30 degrees C to ppte. (I). Cpd. (Ie is an intermediate for triazine derivs. and antimaterial or antibacterial agents, e.g. pencillin derivs. Increasing the HCl content of the soln. to 15-40% decreases the solubility of (I) and reduces its ZnCl2 content, so that products with a Zn content of 0.1% (m.p. 201-202 degrees C, compared with 191 degrees C for known products) can be obtained in high yields (e.g. 60%). The HCl content is pref. increased by introducing gaseous HCl. The ZnCl2 concn. in the soln. during pptn. is pref. =30 wt.%.