Dearomatizing Naphthols Mannich Bases Toward Spiro Thiazolidinethiones Catalyzed By Reduced Graphene Oxide

Graphene derivatives as nontoxic and environmentally new carbon materials have been widely involved as heterogeneous catalysts and materials. Recently, reduced graphene oxide (rGO) has been used as a reusable carbocatalyst in various organic reactions.Spiro compounds have a wide range of applications in the fields of medicine,asymmetric catalysis and materials. In traditional synthetic methods toward spiro compounds, hypovalent iodide compounds and transition metals have been widely used as catalysts. However, these catalysts often have some drawbacks, such as high toxicity, high price and recycling retard. Besides, harsh conditions are necessary for some reactions. Therefore, it is very important to develop a green and reusable catalyst for the synthesis of spiro compounds under mild conditions.In this thesis, rGO was first used as a renewable catalyst in aerobically oxidative dearomatization of naphthol Mannich bases to synthesize spiro thiazolidinethiones.We screened different carbon materials and found rGO had the best catalytic activity.Moreover, the impact of residual manganese on the catalytic activity of rGO was excluded. The rGO was characterized by using FT-IR, X-ray diffraction , TEM, AFM,TG, XPS and Raman. The structures of spiro products were indentified by 1H NMR,13C NMR and high resolution mass spectrometry. The merits of this method include easy operation, simple separation of product, and usage of green oxidant and catalyst.Furthermore, rGO was easily separated after the reactions and it was reusable at least five times without significant loss of catalytic activity.