The invention relates to compounds of formula (I) wherein R1 is hydrogen, lower alkyl or is lower alkyl substituted by hydroxy R2 is hydrogen, lower alkoxy or lower alkyl R3/R4 are independently from each other hydrogen, halogen, lower alkyl, C(O)O-lower alkyl, OR, NRR", lower alkyl substituted by halogen or hydroxy, or is phenyl or benzyl, optionally substituted by one or two halogen atoms R is lower alkyl, or is phenyl, benzyl or pyridinyl, which rings are optionally substituted by one or more halogen, lower alkyl or lower alkyl substituted by fluoro R is hydrogen or lower alkyl R" is lower alkyl, lower alkyl substituted by one or two hydroxy groups, CH(CH2OH)-phenyl, or is -(CH2)2O-lower alkyl, or is phenyl substituted by halogen, or R and R form together with the N-atom to which they are attached a heterocyclic ring, optionally substituted by one or more lower alkyl, CH2C(O)O-lower alkyl, or by CH2C(O)OH Ar is a fϊve-membered heteroaryl group or to pharmaceutically active acid addition salts. It has been found that the present compounds of formula (I) are modulators for amyloid beta and thus, they may be useful for the treatment or prevention of a disease associated with the deposition of β-amyloid in the brain, in particular Alzheimers disease, and other diseases such as cerebral amyloid angiopathy, hereditary cerebral hemorrhage with amyloidosis, Dutch-type (HCHWA-D), multi-infarct dementia, dementia pugilistica and Down syndrome.Linvention porte sur des composés représentés par la formule (I) dans laquelle R1 représente hydrogène, alkyle inférieur ou représente alkyle inférieur substitué par hydroxy R2 représente hydrogène, alcoxy inférieur ou alkyle inférieur R3/R4 représentent indépendamment lun de lautre hydrogène, halogène, alkyle inférieur, C(O)O-(alkyle inférieur) OR, NRR, alkyle inférieur substitué par halogène ou hydroxy, ou représentent phényle ou benzyle, éventuellement substitué par un ou deux atomes dhalogène R représente alkyle inférieur ou repré
