Fused pyrimidine derivatives R 0515 Synthesis and Rearrangement of Cycloalkyl[1,2-e]oxazolo[3,2-a]pyrimidin-8/9-ones: An Access to Cycloalkyl[1,2-d]oxazolo[3,2-a]pyrimidin-5-ones. -The one-step ring-annulation of oxazolines (I) with oxocyclohexanecarboxylate (II) at room temperature gives oxazolopyrimidinones (III). These compounds can be easily dehydrated to provide the corresponding pyrimidinones (IV). In refluxing xylene, the same reaction leads to isomeric pyrimidinones (IV)/(V) and (VII)/(VIII), respectively. -(ADETCHESSI, O.-S.; LEGER, J.-M.; GUILLON, J.; FORFAR-BARES, I.; BOSC, J.-J.; JARRY*, C.; Tetrahedron 61 (2005) 18, 4453-4460; Pharmacochim., Univ. Victor Segalen, F-33076 Bordeaux, Fr.; Eng.) -Bartels 36-150