Abstract: Compounds of the general formula (I) ##STR1## (R is H, alkyl, alkenyl, alkynyl, cycloalkyl, aralkyl or CHO, R.sup.1 and R.sup.2 are independently halogen, alkyl, alkoxy, hydroxyl, cyano, nitro or --NR.sup.3 R.sup.4 where R.sup.3 and R.sup.4 are independently H or alkyl and R.sup.2 may be H) and their salts have selective .alpha..sub.2 -adrenoreceptor antagonist action.The compounds may be prepared by amination of compounds of the general formula (II) ##STR2## (where R.sup.1 and R.sup.2 are as defined above and X is a leaving group.

Abstract: Compounds are disclosed of general formula ##STR1## where R is H, C.sub.1-6 alkyl optionally substituted by C.sub.3-7 cycloalkyl, C.sub.3-6 alkenyl or alkynyl, C.sub.3-7 cycloalkyl, aralkyl or --CHOand the physiologically acceptable salts thereof. The compounds have selective .alpha..sub.2 -adrenoreceptor antagonist action and are indicated as potentially useful for the treatment or prevention of migraine, thrombosis, diabetes, obesity, hypertension, constipation, paralytic ileus, senile dementia and analepsis, and for use in appetite suppression and for the treatment of depression; they may be formulated as pharmaceutical compositions in conventional manner. The compounds may be prepared, for example, by amination of a compound of formula ##STR2## where X is a leaving group such as halogen or a hydrocarbylsulphonyloxy group.