Ring closure reactions O 0130 The Synthesis of a New Fused Heterocyclic System: Hexahydro[1,5]oxathiocino[2,3-b]pyrazine. -The different behavior of the 1,4-diazines (I) and (IV) towards the reaction with 1,3-dibromopropane (II) is studied. -(ZALESKA*, B.; KARELUS, M.; SERDA, P.; J. Chem. Res. 2007, 1, 22-23; Dep. Org. Chem., Jagiellonian Univ., PL-30-060 Krakow, Pol.; Eng.) -H. Haber 29-042