A compd. of the 3a, 4, 5, 9b-tetrahydrobenzo[e -isoindoline[I; R, R1, R2 are independently selected from H, OH, C1-3 alkoxy, or R and R1, or R1 and R2 can be taken together to form methyleneodioxy or ethylenedioxy bridge; with proviso that at least one of R, R1 or R2 must be other than H; and R3 is H, C1-4 alkyl, aralkyl, 1,4- benzodioxane), useful as antihypertensive agents and their intermediates, is prepd. by reduction of a compd. of 1,3-dioxo-3a, 4, 5, 9b-tetrahydro-benzo [e -isoindoline (II).