The present invention relates to a compound of formula IwhereinR1 is phenyl, lower alkyl, C3-6-cycloalkyl, —；CH2—；C3-6-cycloalkyl or bridged C4-6-cycloalkyl, substituted by one, two or three halogen atoms, or by lower alkyl or lower alkyl substituted by halogen；R2 is a five or six membered heteroaryl group, selected fromwhereinR6 is hydrogen, lower alkyl, halogen or lower alkoxy； andR7 is hydrogen, lower alkoxy or halogen；R3 is lower alkyl or lower alkyl substituted by hydroxy:R4 is hydrogen or lower alkyl；R5 is hydrogen or lower alkyl；n is 1 or 2；-( )n- is —；CH2—； or —；CH2CH2—； for n being 1 or 2；or to a pharmaceutically active acid addition salt thereof, to a racemic mixture or to its corresponding enantiomer and/or optical isomer and/or stereoisomer thereofThe compounds may be used for the treatment of Alzheimer's disease, cerebral amyloid angiopathy, hereditary cerebral hemorrhage with amyloidosis, Dutch-type (HCHWA-D), multi-infarct dementia, dementia pugilistica or Down syndrome.
