The present invention relates to compounds of formula I,whereinR1 is phenyl, lower alkyl, C3-6-cycloalkyl, —；CH2—；C3-6-cycloalkyl, or bridged C3-5-cycloalkyl, optionally substituted by one, two or three substituents, selected from halogen, lower alkyl or lower alkyl substituted by halogen；R2 is hydrogen, halogen, lower alkoxy, lower alkyl substituted by halogen or lower alkoxy substituted by halogen；R3 is a five membered heteroaryl group, selected fromwhereinR6 is hydrogen or lower alkyl；R7 is halogen or lower alkyl；R8 is hydrogen or lower alkyl；R9 is hydrogen or lower alkyl；R4 is lower alkyl or lower alkyl substituted by hydroxy；R5/R5′； is independently from each other hydrogen or lower alkyl；-( )n- is —；CH2—； or —；CH2CH2—； for n being 1 or 2；X is CH or N；or to pharmaceutically active acid addition salts thereof, to racemic mixtures or to its corresponding enantiomers and/or optical isomers and/or stereoisomers thereof.The 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.
