The invention relates to a compound selected from the group consisting of compounds of the formula: ##STR1## in which R.sub.1, R.sub.2 and R.sub.3 are independently selected from hydrogen, halogen, trifluoromethyl, nitro, C.sub.1-4 alkoxy and C.sub.1-4 alkyl, R.sub.4 represents a heterocyclic radical selected from the radicals having the formulae ##STR2## in which R.sub.5 and R.sub.6 are independently selected from hydrogen, C.sub.1-4 alkyl, phenyl and halophenyl, R.sub.7 is selected from hydrogen and C.sub.1-4 alkyl, and a pharmaceutically acceptable acid addition salt thereof. These compounds are useful for the treatment of gastric ulcers.