Isoindoline derivatives of the formula ##STR1## and the pharmaceutically acceptable acid addition salts thereof, wherein R represents a moiety selected from the group consisting of hydrogen, halogen, lower alkyl, lower alkoxy, nitro, hydroxy and hydroxy lower alkyl, and n is a positive number from 1 to 3, which R's may be the same or different when n is 2 or 3, and when n is 2, the two R's may be joined to the carbon atom vicinal to the phenyl ring to which the two R's are joined and may taken together form lower alkylenedioxy and the group ##STR2## and R.sub.1 is a member of the group consisting of hydrogen and lower alkyl.The compounds of this invention can be readily prepared by reacting a compound of the formula ##STR3## wherein R represents, in addition to the above defined, alkoxycarbonyloxy; R.sub.1 and n are as defined above; and X is halogen or the groups --O--SO.sub.2 --Y where Y is either lower alkyl or aryl, with isoindoline of the formula ##STR4## or a minemal acid salt thereof. The compounds are useful in such fields as, for example cardiovascular drugs.