N-linked azabicyclic heterocycles useful for treating dementia

Abstract

A compound of formula (I) or a pharmaceutically acceptable salt thereof: ##STR1## in which one of X and Y represents hydrogen and the other represents Z, where Z is a group ##STR2## in which Q represents a 3-membered divalent residue completing a 5-membered aromatic ring and comprises zero, one or two nitrogen atoms, Q being optionally C-substituted by a group R.sub.1 selected from halogen, CN, OR.sub.2, SR.sub.2, N(R.sub.2).sub.2, NHCOR.sub.2, NHCOOCH.sub.3, NHCOOC.sub.2 H.sub.5, NHOR.sub.2, N.sub.3, NHNH.sub.2, NO.sub.2, COR.sub.2, COR.sub.3, C.sub.2-4 alkenyl, C.sub.2-4 alkynyl, cyclopropyl or C.sub.1-2 alkyl optionally substituted with OR.sub.2, N(R.sub.2).sub.2, SR.sub.2, CO.sub.2 R.sub.2, CON(R.sub.2).sub.2 or one, two or three halogen atoms, in which each R.sub.2 is independently hydrogen or C.sub.1-2 alkyl and R.sub.3 is OR.sub.2, NH.sub.2 or NHR.sub.2 ; r represents an integer of 2 or 3, s represents an integer of 1 or 2 and t represents 0 or 1; R.sub.a and R.sub.b each represent hydrogen or, when X is hydrogen, optionally together represent a bond; with the proviso that when Y is hydrogen s is 1.