Sodium Hydroxide → 3-(2-Thiazolyl)propylguanidine hemisulphate

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A mixture of 3-phthalimidothiobutyramide (15.0 g) and bromoacetaldehyde diethyl acetal (19.7 g) is heated at 100° C with frequent agitation for two hours. The solid mass is extracted with hot ethanol, and the extracts are treated with charcoal and filtered. On cooling, crystals are deposited. These are dissolved in water (50 ml) and the solution washed with ether (25 ml) and diluted with aqueous sodium acetate to pH 6. A yellowish-brown solid crystallizes out which is collected and washed with water yielding 3-(2-thiazolyl)propylphthalimide hydrobromide, m.p. 67°-70° C. The phthalimido derivative (5.0 g) is dissolved in ethanol (50 ml), hydrazine hydrate (2 ml) is added and the solution heated under reflux for two hours. The solvent is removed under reduced pressure and the residue is dissolved in concentrated hydrochloric acid (30 ml) and heated under reflux for one hour. After cooling, phthalhydrazide is removed by filtration and the filtrate evaporated to dryness. The residue is recrystallized from methanol-ether yielding 3-(2-thiazolyl) propylamine dihydrochloride, m.p. 160°-165° C. 3-(2-Thiazolyl)propylamine (2.7 g) (prepared from the amine dihydrochloride by reaction with aqueous sodium hydroxide and extraction with ethyl acetate) is mixed intimately with finely powdered S-methyl-thiouronium sulphate (5.3 g) and the mixture is heated at 140°-150° C for one hour. After cooling, the mass is extracted with hot ethanol several times, and the combined extracts are diluted with ether which causes the precipitation of a white solid. Recrystallization from aqueous ethanol yields 3-(2-thiazolyl)propylguanidine hemisulphate, m.p. 160°-163° C.

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