The present invention relates to novel compounds of the formula I which are inhibitors of phosphodiesterase type 10A and to their use for the manufacture of a medicament and which thus are suitable for treating or controlling of medical disorders selected from neurological disorders and psychiatric disorders, for ameliorating the symptoms associated with such disorders and for reducing the risk of such disorders. wherein Q is O or S, X1 is N or CH, X2 is N or C-R7； X3 is O, s -X4=C(R8)-, where C(R8) is bound to the carbon atom which carries R2, or -X5=C(R9)-, where X5 is bound to the carbon atom which carries R2； X4 is N or C-R9； X5 is N； Het is selected from optionally substituted phenyl, monocyclic hetaryl and fused bicyclic hetaryl； R1 is selected inter alia from hydrogen, halogen, OH, C1-C4-alkyl, trimethylsilyl, C1-C4-alkylsulfanyl, C1-C4-alkoxy-C1-C4-alkyl, C1-C4-alkoxy, C1-C4-alkoxy-C1-C4-alkoxy, the moiety Y1-Cyc1； R2 is selected inter alia from hydrogen, halogen, OH, C1-C4-alkyl, trimethylsilyl, C1-C4-alkoxy-C1-C4-alkyl, C1-C4-alkoxy, C1-C4- alkoxy-C1-C4-alkoxy, C2-C4-alkenyloxy, etc； A represents one of the following groups A1, A2, A3, A4 or A5: where * indicates the points of attachment to Het and to the nitrogen atom, respectively； and where R3 to R9, R3e, R3f, A', Y1 and Cyc1 are defined in the claims.本發明係關於作為磷酸二酯酶第10A型之抑制劑的新穎式I化合物及其用於製造藥物之用途，且因此該等新穎化合物適用於治療或控制選自神經病症及精神病症之醫學病症，適用於改善與該等病症有關之症狀且適用於降低該等病症之風險。其中Q 為O或S；X1為N或CH；X2為N或C-R7；X3為O、S、-X4=C(R8)-，其中C(R8)鍵結於攜帶R2之碳原子；或-X5=C(R9)-，其中X5鍵結於攜帶R2之碳原子；X4為N或C-R9；X5為N；Het 係選自視情況經取代之苯基、單環雜芳基及稠合雙環雜芳基；R1 尤其選自氫、鹵素、OH、C1-C4烷基、三甲基矽烷基、C1-C4烷基硫基、C1-C4烷氧基-C1-C4烷基、C1-C4烷氧基、C1-C4烷氧基-C1-C4烷氧基、部分Y1-Cyc1；R2 尤其選自氫、鹵素、OH、C1-C4烷基、三甲基矽烷基、C1-C4烷氧基-C1-C4烷基、C1-C4烷氧基、C1-C4烷氧基-C1-C4烷氧基、C2-C4烯氧基等；A 表示以下基團A1、A2、A3、A4或A5中之一者：其中*指示分別與Het及氮原子連接之點；且其中R3至R9、R3e、R3f、A'、Y1及Cyc1係定義於申請專利範圍中。
