The present invention provides compounds of formula (I) and pharmaceutically acceptable salts thereof: wherein A is C1-6alkyl, C2-6alkenyl, C2-6alkynyl, C3-6cycloalkyl, arylC1-6alkyl, aryl, S(O)pR1, OR1 or NR1R12; B is optionally substituted 5- or 6-membered heteroaromatic ring or C(O)NR10R11; R1 is hydrogen, optionally substituted C1-6alkyl, C2-6alkenyl, C2-6alkynyl, C3-6cycloalkyl or C3-6cycloalkenyl, optionally substituted aryl, arylC1-6alkyl, arylC2-6alkenyl or arylC2-6alkynyl or an optionally substituted 5- or 6-membered heteroaromatic ring; R2 and R3 are hydrogen or C1-6alkyl; R4 is hydrogen, C1-8alkyl, C2-8alkenyl, C2-8alkynyl, aryl or CH2(CO)mNR8R9; R5 is NR6R7, C1-6alkyl or C1-6alkoxy; R6 is independently as defined for R4; R7 is aryl optionally substituted by halogen, nitro or cyano; R8 is hydrogen, C1-6alkyl, C3-6cycloalkyl, C3-6cycloalkenyl, C2-6alkenyl, C2-6alkynyl; arylC1-6alkyl, arylC2-6alkenyl or arylC2-6alkynyl optionally substituted on the aryl ring by halogen, nitro or cyano; thiophene or pyridine; R9 is C1-6alkyl; C2-alkenyl; C2-6alkynyl; or phenyl optionally substituted by one, two or three substituents independently chosen from halogen, CF3, OCH3, nitro and cyano; R10 and R11 are individually hydrogen, C1-6alkyl, C2-6alkenyl, C2-6alkynyl or C3-8cycloalkyl or R10 and R11, together with the nitrogen atom to which they are attached, form a saturated 4 to 8 membered ring optionally containing an oxygen atom or a further nitrogen atom as a ring member, the further nitrogen atom being unsubstituted or substituted by C1-4alkyl, C2-4alkenyl or C2-4alkynyl; R12 is hydrogen or C1-6alkyl; m is zero or 1; p is zero, 1 or 2; q is 0, 1 or 2; and r is 0, 1 or 2; the preparation of these compounds, their use in enhancing cognition in disease states, particularly Alzheimer's disease, and methods of treatment using them.
Substituted thienobenzisoxazole derivatives for enhancing cognition