Synthesis Of Furanone Fused Pyridones And 2-aminobenzothiazoles By C(sp~2)-H Bond Functionalization

N(O,S)-Heterocyclic compounds not only constitute the essential unit of numerous natural products,but also demonstrate significant and diverse bioactivities.Therefore,how to quickly and efficiently synthesize these compounds has become an important research content in organic chemistry and pharmaceutical chemistry today.On the other hand,the application of the inert C-H bond functionalization reaction in organic synthesis has effectively improved the atomic economy and the step economy of the reaction,and gradually become a powerful synthesis method for complex organic compounds.In this dissertation,we use inert C(sp~2)-H bond functionalization to explore and discover new methods for the synthesis of furanone fused pyridones and 2-aminobenzothiazoles.The main results are summarized in the following two parts:Firstly,a novel synthesis of furanone fused pyridones via functionalization of C(sp~2)–H bonds is presented.Studies have found that A highly efficient synthesis of furanone and pyridones via Rh(III)-catalyzed one-pot cascade reactions of aromatic/vinylic N-alkoxyamides with 4-hydroxy-2-alkyno-ates.Mechanistically,the formation of the product is triggered by a Rh(III)-catalyzed inert C(sp~2)–H bond activation of the amide substrate followed by its[4+2]annulation and lactonization with4-hydroxy-2-alkynoate.During the process,the N-alkoxy unit act as an oxidizing and traceless directing group.Secondly,a novel synthesis of 2-aminobenzothiazoles via functionalization of C(sp~2)–H bonds is presented.The method uses phenyl isothiocyanate and amine compounds as raw materials,iodine as a catalyst,and oxygen as an oxidant to achieve efficient synthesis of 2-aminobenzothiazoles under relatively mild conditions.Mechanistically,the formation of 2-aminobenzothiazoles involves the in situ formation of the required benzothiourea intermediate followed by its intramolecular cross dehydrogenative coupling of a C(sp~2)-H bond and a S-H bond.In summary,some novel synthetic approaches toward furanone fused pyridones and2-aminobenzothiazoles have been developed.Compared with existing methods,this new protocol shows advantages such as broad substrate scope,high regioselectivity,good tolerance of functional groups,simple operation and high efficiency.