Compounds of the general formula: ##STR1## and non-toxic physiologically acceptable salts thereof, in which R.sub.1 is a halogen atom or a group NR.sub.2 R.sub.3 ; R.sub.2 and R.sub.3, which may be the same or different, are hydrogen or (C.sub.1 -C.sub.6) straight or branched chain alkyl or R.sub.2 and R.sub.3 may, together with the nitrogen atom, form a 5 or 6 membered heterocyclic ring which may contain a further hetero atom selected from O, N or S; or R.sub.2 may be hydrogen and R.sub.3 may by group R.sub.4 CO or R.sub.4 SO.sub.2 where R.sub.4 is hydrogen or alkyl (C.sub.1-4); R.sub.5 is hydrogen or one or more halogen atoms or hydroxy or alkoxy (C.sub.1-4) groups; and X is CH.sub.2, O or a group NR.sub.6 where R.sub.6 is hydrogen or alkyl (C.sub.1-4). These compounds block .beta.-adrenoreceptors.