Abstract: A new and simple process for the preparation of crystalline cimetidine (N-cyano-N'-methyl-N"-{2/(5-methyl-1H-imidazole-4-yl)methylthio/ethyl}guan idine) is described, wherein cimetidine is obtained by reacting O-ethyl-S-(4-methylimidazolyl-5-methyl)dithiocarbonate hydrobromide with N-cyano-N'-methyl-N"-(2-chloroethyl)guanidine in an aqueous methylamine solution at a temperature between room temperature and the reflux temperature of the reaction mixture, whereupon the desired compound is separated.Cimetidine is a valuable drug in the therapy of the ulcer disease.

Abstract: A new, technologically easily feasible process for the preparation of 4(5)-methyl-5(4)-thiomethyl imidazole of the formula ##STR1## and of acid addition salts thereof is described, wherein 4(5)-methyl-5(4)-bromomethyl imidazole hydrobromide is reacted in an aqueous medium at room temperature with potassium O-ethyl dithiocarbonate to the intermediate O-ethyl-S-(4-methylimidazolyl-5-methyl) dithiocarbonate, which is hydrolyzed at the reflux temperature under nitrogen atmosphere with an aqueous HBr or HCl solution to 4(5)-methyl-5(4)-thiomethyl imidazole hydrobromide or hydrochloride resp.The compound is a valuable starting material in the synthesis of cimetidine, a well-known drug in the therapy of the ulcer disease.