Studies On The Oxidation Cleavage Of C-C Bonds Of Indoles Affording Quinazolinones And Quinazolines

C-C bond is one of a very basic chemical bond and widely exists in organic molecules.Similar to the activation of C-H bond,the selective cleavage and transformation of C-C bond can construct new C-C bond and C-heteroatom bond directly from inert starting materials,which is an important research direction in organic synthesis.Because of its thermodynamic and kinetic stability,the selective functionalization of unstrained C-C bond is still a great challenge.In order to realize such chemical process,transition metal complexes and harsh reaction condi tions are usually needed.Compared with the widely studied three-membered and four-membered ring,the relatively unstrained five-membered ring compounds such as indoles have not been fully underutilized.In this paper,tetrabutylammonium iodide/tert-butyl hydrogen peroxide,an efficient and environmentally friendly catalytic oxidation strategy,was successfully used to realize the selective functionalization of C-C bond of indoles and a series of nitrogen-containing heterocyclic compounds such as quinazolinones and quinazolines were constructed efficiently,which provide a new strategy for the activation of C-C bond and expand the reaction type of constructing other heterocyclic compounds by indole compounds.The specific contents and research results are as follows:(1)A method for the synthesis of quinazolinones by highly selective oxidative cleavage of multiple C-C bonds of 3-methylindoles was developed.In the n-Bu₄NI/t-BuOOH catalytic oxidation system,a series of quinazolinones were efficiently constructed by the coupling cyclization of 3-methylindoles with primary amines.The reaction realized the double cleavage of sp²C-sp²C double bond and sp³C-sp²C single bond of Indole substrate molecules by a free radical tandem way.The reaction process includes continuous oxygenation,nitridation,ring-opening and recyclization,with a wide range of substrates and good functional group compatibility.(2)A simple and efficient metal-free catalytic ring expansion reaction of3-phenylindoles and amines has been developed.Under the above similar conditions,the cleavage of the C2-C3 double bond of 3-phenylindoles was achieved,and a series of 3-phenylquinazolines were successfully synthesized by inserting a nitrogen atom,which provides a new approach for the construction of the nitrogen-containing heterocyclic compound.