Modulators of beta-amyloid.

A compound of the general formula: R1 is -C (O) -lower, cyano or is hetaryl O-alkyl; hetaryl is a heteroaryl group of five or six membered ring optionally substituted with R '; R 'is halogen, C1-C7 alkyl, C1-C7 alkyl substituted by halogen, C1-C7 or C1-C7 substituted by halogen; R2 is hydrogen, C1-C7 alkoxy, C1-C7, halogen or cyano; R3 is - (CH2) nC (O) O-C1-C7, C1-C7, C1-C7 alkoxy, hydroxy, -O-Si (CH3) 2-C1-C7, -C (O) -N (C1-C7) 2, -OS (O) 2-C1-C7, C3-7 cycloalkyl, S (O) 2-aryl, heterocyclyl, -C (O) -heterocyclyl, or is aryl or hetaryl, which aryl or hetaryl rings are optionally substituted by one or more R ''; R4 is hydrogen, C1-C7, hydroxy or CH2CN; X is S or -N = C (R5) -; R5 is hydrogen, C1-C7 alkyl or hydroxy, Y is a bond, -O-, -CH2-, -CH2-CH2-, OO or -N (R) -; R is hydrogen, C1-C7, C (O) O-C1-C7, C (O) -C1-C7, S (O) 2-C1-C7 or benzyl; n is 0 or 1; or their addition salts with pharmaceutically acceptable acid.