The present invention relates to compounds of the formula (I) wherein Ar1, R1, R2, R3, R4a, R4b and (R5)n are as described in the description, to their preparation, to pharmaceutically acceptable salts thereof, and to their use as pharmaceuticals, to pharmaceutical compositions containing one or more compounds of formula (I), and especially to their use as orexin receptor antagonists.本發明係關於式(I)化合物,其中Ar1、R1、R2、R3、R4a、R4b及(R5)n係如說明書中所述;其製備、其醫藥學上可接受之鹽及其作為藥物之用途、含有一或多種式(I)化合物之醫藥組合物,且尤其關於其作為食慾素受體拮抗劑之用途。