Studien zur Chemie von thienoanellierten O,N- und S,N-haltigen Heterocyclen, 15. Mitt. [1]: Zugänge zum Thieno[3,2-b][1,4]-oxazin-, Thieno[3,2-b][1,4]thiazin-und Thienodithiazepin-Grundgerüst

3-Bromo-2-nitrothiophene is reacted with bifunctional reagents like methyl 3-mercaptopropionate to yield the corresponding thioether derivatives. Reduction of the nitro function followed by ring closure provides a possibility to synthesize the hitherto unknown thieno [3,2-b][1,4]oxazines as well as thieno [3,2-b][1,4]thiazines. In a similar manner, the new thienodithiazepine ring system is obtained.