Disclosed are 2-(3-phenyl)-N-(pyridinyl)-2-[(methylpyrimidin-5-yl)oxymethyl]cyclopropane carboxamide derivatives as represented by the general formula (IV), or a pharmaceutically acceptable salt thereof, wherein Q represents -CH- or a nitrogen atom, R1a and R1b each independently represent a alkyl, haloalkyl, hydroxy-alkyl or alkoxy-alkyl R1c represents a hydrogen atom or a hydroxyl group R2a, R2b, R2c and R2d each independently represent a hydrogen atom, a halogen atom, a hydroxyl group, alkyl, alkoxy, haloalkyl or a cyano group and R3a, R3b, R3c and R3d each independently represent a hydrogen atom, a halogen atom, a hydroxyl group, alkyl, alkoxy, haloalkyl, alkoxy-alkyl, a cyano group or a cyano-alkyl group. Representative compounds include (1R,2S)-2-{ [(2,4-dimethylpyrimidin-5-yl)oxy]methyl} -N-(5-fluoropyridin-2-yl)-2-phenylcyclopropanecarboxamide, (1R,2S)-2-{ [(2,4-dimethylpyrimidin-5-yl)oxy]methyl} -N-(5-fluoro-4-methylpyridin-2-yl)-2-phenylcyclopropanecarboxamide, (1R,2S)-2-{ [(2,4-dimethylpyrimidin-5-yl)oxy]methyl} -N-(5-fluoro-4-methylpyridin-2-yl)-2-(3-fluorophenyl)cyclopropanecarboxamide, (1R,2S)-2-{ [(2,4-dimethylpyrimidin-5-yl)oxy]methyl} -2-(3-fluorophenyl)-N-(5-fluoropyridin-2-yl)cyclopropanecarboxamide, (1R,2S)-2-(3,5-difluorophenyl)-2-{ [(2,4-dimethylpyrimidin-5-yl)oxy]methyl} -N-(5-fluoro-4-methylpyridin-2-yl)cyclopropanecarboxamide and (1R,2S)-2-{ [(4-ethyl-2-methylpyrimidin-5-yl)oxy]methyl} -2-(3-fluorophenyl)-N-(pyridin-2-yl)cyclopropanecarboxamide. Also disclosed is a compound as defined above or a pharmaceutically acceptable salt thereof for use as an active ingredient of a pharmaceutical composition, for the treatment of sleep disorder (and particularly insomnia) for which orexin receptor antagonism is effective.
