The present invention relates to compounds of formula (I), wherein R1 is heteroaryl or heterocyclyl, optionally substituted; R2 is C1-4alkyl, heterocyclyl, C1-4alkylaryl, C1-4alkylheteroaryl, carbocyclyl, C1-4alkylheterocyclyl, heterocyclyl-heteroaryl, aryl-heterocyclyl, carbocyclyl-heteroaryl, heterocyclyl-aryl, optionally substituted; R3 is hydrogen or C1-4alkyl, or R2 and R3 may together with the nitrogen atom, form a saturated ring system containing 4, 5 or 6 ring forming atoms, and optionally substituted; R4 is hydrogen, halogen, methyl or methoxy; to pharmaceutical composition containing said compounds and to the use of said compounds in therapy, for instance in treating cognitive disorders. The present invention further relates to new intermediates useful in the preparation thereof.