The present invention relates to compounds of the formula I and their salts etc. 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 Y1 and Y2 are adjacent atoms in Het1, which are independently selected from the group consisting of carbon and nitrogen； k is 0, 1, 2 or 3； Het1 is a bivalent monocyclic 5- or 6-membered heteroaromatic radical, having 1, 2 or 3 heteroatoms or heteroatom moieties selected from O, S, N and N-Ra as ring members, or a bivalent fused bicyclic 8-, 9- or 10-membered heteroaromatic radical, having 1, 2, 3 or 4 heteroatoms or heteroatom moieties selected from O, S, N and N-Ra as ring members； Het2 is inter alia monocyclic 5- or 6-membered hetaryl, having 1, 2 or 3 heteroatoms or heteroatom moieties selected from O, S, N and N-R1a as ring members, Cyc is inter alia optionally substituted monocyclic 5- or 6-membered hetaryl or optionally substituted fused 8-, 9- or 10-membered bicyclic hetaryl； Ar is optionally substituted phenylene or optionally substituted bivalent 6-membered hetaryl； R is attached to a carbon atom of Het1 and inter alia - halogen, C1-C6-alkyl, C2-C6-alkenyl, C2-C6-alkynyl, C1-C6-alkoxy, C1-C6-fluoroalkyl, C1-C6-fluoroalkoxy, C3-C6-cycloalkyl etc.本發明係關於作為磷酸二酯酶第10A型之抑制劑的式I化合物及其鹽等以及其用於製造藥物之用途，且因此該等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及適用於降低該等病症之風險。其中Y1及Y2為Het1中之相鄰原子，其獨立地選自由碳及氮組成之群；k為0、1、2或3；Het1為具有1、2或3個選自O、S、N及N-Ra之雜原子或雜原子部分作為環成員的二價單環5員或6員雜芳族基，或具有1、2、3或4個選自O、S、N及N-Ra之雜原子或雜原子部分作為環成員的二價稠合雙環8員、9員或10員雜芳族基；Het2尤其為具有1、2或3個選自O、S、N及N-R1a之雜原子或雜原子部分作為環成員的單環5員或6員雜芳基，Cyc尤其為視情況經取代之單環5員或6員雜芳基或視情況經取代之稠合8員、9員或10員雙環雜芳基；Ar為視情況經取代之伸苯基或視情況經取代之二價6員雜芳基；R連接於Het1之碳原子且尤其為鹵素、C1-C6烷基、C2-C6烯基、C2-C6炔基、C1-C6烷氧基、C1-C6氟烷基、C1-C6氟烷氧基、C3-C6環烷基等。
