A Synthesis of Spirocyclic Oxazinoisoquinolines and Oxazinoquinolines Bearing Thiazolopyrimidine Moieties

The reaction of isoquinoline or quinoline with dialkyl acetylenedicarboxylates in the presence of alkyl 2-{3,5-dioxo-5H-thiazolo[ 3,2-a] pyrimidin-2(3H)-ylidene} acetates (generated in situ from acetylenedicarboxylates and 2-thiouracils) led to dialkyl 2-(2-alkoxy-2oxoethylidene)- 5-oxo-2H, 5H, 11b' H-spiro{thiazolo[3,2-a] pyrimidine3,2'-[ 1,3] oxazino[2,3-a] isoquinoline}-3', 4'-dicarboxylates or dialkyl 2(2-alkoxy-2-oxoethylidene)-5-oxo-2H, 4a' H, 5H-spiro{thiazolo[3,2-a] pyrimidine- 3,2'-[1,3] oxazino[3,2-a] quinoline}-1', 2'-dicarboxylates in good yields. The structure of the target compounds was confirmed by X-ray diffraction study.