UNEXPECTED FORMATION OF THINO[3′,4′:4,5]OXAZOLO[1,3-b]-[1,3]OXAZEPINE DERIVATIVES

The reactions of pyridinium 2-alkylthio-1-benzoyl-2-thioxoethylides with dimethyl acetylenedicarboxyate in THF at the reflux temperature afforded the unexpected products, dimethyl 2-alkylthio-4a-phenyl-4aH,5aH-thiino-[3 ',4 ':4,5]oxazolo[1,3-b][1,3]oxazepine-3,4-dicarboxylates, together with dimethyl 10aH-4-alkylthio-5-benzoylpyrido[1,2-d]thiazepine-1,2-dicarboxylates.