Construction And Transformation Of Benzofuranone Saturated Carbon Centers

Benzofuran-2(3H)-ones are a sort of important structure in natural products,pharmaceuticals,antioxidants and biologically active compounds.It was synthesized by Friedel-Crafts reaction,intramolecular dehydration ring-closing reaction and transition-metal-catalyzed reaction.Despite the progress,the synthesis of benzofuran-2(3/H)-ones exist some defects,such as prefunctionalization of starting materials,harsh reaction conditions,low yield,poor tolerance of functional groups,complicated procedures or complex operations,etc.Therefore,it is theoretically and practically important to develop an efficient,green and simple method for the synthesis of benzofuran-2(3H)-ones.Due to the low pKa value of the C-H bond at C3 in benzofuran-2(3H)-ones and easy enolization,the C-H bond is active that can be easily functionalized.In recent years,C-H bond functionalization of benzofuranones has become a hot issue.Based on previous work of our group,in this thesis,we have developed a protocol for the efficient synthesis of 3-aryl benzofuran-2(3H)-ones under solvent-free conditions from phenols and mandelic acids using Ni(OTf)2 as a catalyst.Considering the special activity of benzofuran-2(3H)-ones,the further functionalization of benzofuran-2(3H)-ones was studied,and a series of benzofuran-2(3H)-ones skeleton compounds were constructed.The main results of this paper are as follows:(1)We developed a protocol for the efficient synthesis of 3-aryl benzofuran-2(3H)-ones under solvent-free conditions from phenols and mandelic acids using Ni(OTf)2 as a catalyst.A diverse range of mandelic acids and phenols undergo C-H/O-H bond dual functionalization to generate products in moderate to good or excellent yields.Compared with the traditional method,this system is greener,efficient,simple,high yield and good substrate applicability.The nickel catalyst can be easily recycled in a test of three runs at the scale of 10 mmol without significant decline in the product yield.This proves that the reaction system has a good application value and provides a potential for industrialization.(2)We described a catalytic cross-dehydrogen ative coupling(CDC)reaction of benzofuranones with quinolines,indoles,carbazoles and thiophene that creates three aryls quaternary carbon center at C3 position.This CDC reaction of benzofuranones and heteroarenes provides a simple and efficient approach for the generation of all-carbon triaryl quaternary centers.Various quinolines,indoles,carbazoles and thiophenes are suitable substrates for this transformation.This CDC system tolerates a diversity of valuable functional groups on the aryl ring,such as alkoxy,amino,halo,cyano,ester,and formyl groups,and 97 examples,the yields are up to 93%.The product can be enlarged to gram-scale.Furthermore,preliminary mechanistic studies indicate that this protocol involves a Cu(?)/Cu(?)radical process or a Cu(?)/Cu(?)/Cu(?)catalytic cycle.It also first provides a simple and effective method for the arylation of benzofuranones.(3)We developed an efficient and convenient method for the synthesis of triarylmethanes via decarbonylation from 3,3-diaryl benzofuranones in the presence of CH3ONa and H2O.The reaction can be applied to the synthesis of various triarylmethanes,including various heterocyclic rings such as quinoline,indole,carbazole,and thiophene groups in good to excellent yields.Phenol rings as well as haloarene groups in the products will allow further useful transformations,leading to functionalized triarylmethanes.The mechanism can be demonstrated by deuterium experiment and carbon dioxide capture experiment.(4)We developed an efficient and convenient method for the synthesis of indolin-2-one in the presence of iodine.It is first example that indolin-2-one was synthesized by ring opening reaction of lactone without metal catalysis.Through optimization of reaction conditions,various benzofuran-2(3H)-ones and amines are suitable substrates for this transformation and a series of indolin-2-ones were obtained in good yield.Preliminary studies on the reaction mechanism show that the reaction involves the single electron transfer of process.