Diversity-Oriented Synthesis Of Thiochromeno[2,3-b]Pyridines And Chromeno[2,3-b]Quinolines From β-(2-Haloaroyl) Thioacetanilides

Diversity-oriented synthesis of small organic molecules has been a rapidly developing interdisciplinary field in recent years. Diversity-oriented synthesis offers a powerful means to access structurally complex and diverse small molecules. Multicomponent reactions are the most enabling synthetic tools in diversity-oriented synthesis. This thesis focuses on diversity-oriented synthesis of several heterocyclic skeletons from functionalβ-(2-haloaroyl) thioacetanilides.In the first chapter, polarized ketene N,S-, N,N-, S,S-acetals andβ-aroyl thioacetanilides as very useful synthons in organic synthesis were reviewed in brief. Then the advantages of several synthetic methods such as diversity-oriented synthesis(DOS), multicomponet reactions (MCRs) and microwave-assisted organic synthesis(MAOS) were introduced.In the second chapter and the third chapter, two series of unusual fused tricyclic thiochromeno[2,3-b]pyridines were successfully synthesized by tandem aza-[3+3] annulation and SNAr ofβ-(2-haloaroyl) thioacetanilides with activated 4-arylidene-2-phenyloxazol-5(4H)-ones or aromatic aldehydes and ethyl 2-cyanoacetate under microwave irradiation. These reactions were very mild, convenient and effective. To the best of our knowledge, the fused tricyclic thiochromeno[2,3-b]pyridine skeleton has not been reported before.In the fourth chapter, a series of new chromene derivatives were synthesized by tandem oxy-[3+3] annulation ofβ-(2-haloaroyl) thioacetanilides with aromatic aldehydes and 5,5-dimethyl-1,3-cyclohexanedione catalyzed by triethylamine; Then they underwent an intramolecular SNAr in the presence of K₂CO₃ and produced a series of new chromeno[2,3-b]quinoline derivatives. This is a new strategy for the synthesis of chromeno[2,3-b]quinoline derivatives, which has not found in literature.Up to 50 new compounds were synthesized in this paper. The structures of all the target compounds were confirmed by the IR, ¹ H NMR, ¹³ C NMR and elemental analyses, some of them were confirmed by mass spectra. Moreover, the crystal structures of 6b and 9f have been studied by X-ray diffraction.