This invention is directed to compounds, which are PDE10A enzyme inhibitors. The invention provides a pharmaceutical composition comprising a therapeutically effective amount of a compound of the invention and a pharmaceutically acceptable carrier. The present invention also provides processes for the preparation of the compounds of formula I. The present invention further provides a method of treating a subject suffering from a neurodegenerative disorder comprising administering to the subject a therapeutically effective amount of a compound of formula I. The present invention also provides a method of treating a subject suffering from a drug addiction comprising administering to the subject a therapeutically effective amount of a compound of formula I. The present invention further provides a method of treating a subject suffering from a psychiatric disorder comprising administering to the subject a therapeutically effective amount of a compound of formula I.本發明係關於為PDE10A酵素抑制劑之化合物。本發明提供一種醫藥組成物,其包含治療有效量之本發明之化合物及醫藥學上可接受之載劑。本發明亦提供製備式I化合物之方法。本發明進一步提供一種治療罹患神經退化性病症之個體的方法,其包含投予該個體治療有效量之式I化合物。本發明亦提供一種治療罹患藥物成癮之個體的方法,其包含投予該個體治療有效量之式I化合物。本發明進一步提供一種治療罹患精神病症之個體的方法,其包含投予該個體治療有效量之式I化合物。