Study On C-H Alkylation Of Quinoxalone Derivatives Enabled By Visible Light

As an important kind of N-heterocycle,quinoxalin-2（1H）-ones,especially alkylated at the C3 position,have particular biological activities and chemical properties and attracted substantial attention.Although great progress has been achieved in the field on the synthesis of 3-alkyl quinoxalin-2（1H）-ones,there are still deficiencies to be improved.Visible-light catalysis is a powerful methodology to achieve efficient and selective chemical transformation under mild reaction conditions,which has been booming in biological and pharmaceutical research due to its inherent environmental friendliness and sustainability.This thesis focuses on the methodology,mechanism and application of using photocatalysis as a green and efficient method to realize the alkylation of quinoxalin-2（1H）-ones at C3 position without transition metal catalyst.These are the main topics:1.A visible-light-driven divergent transformation of quinoxalin-2（1H）-ones had been established mediated using H₂O₂as a green oxidant.This reaction was controlled by the reaction atmosphere,providing 3-alkylquinoxalin-2（1H）-ones and quinoxaline-2,3（1H,4H）-diones,respectively.50 alkylation products and 15 oxidation products of quinoxalin-2（1H）-ones were successfully prepared.In addition,gram scale reaction and derivatization experiments were carried out.Finally,the possible mechanism was proposed according to the mechanism exploration experiment.2.A method of C3 alkylation of quinoxalin-2（1H）-ones with carboxylic acid as alkyl source was studied.Decarboxylation coupling reaction of various types of carboxylic acids and quinoxalin-2（1H）-ones had been realized in green solvent（dimethyl carbonate）under photocatalytic conditions,using TBHP as oxidant.Such approach also can efficiently convert a wide range of amino acids and carboxyl-containing drugs into desired products.67 alkylation products were successfully synthesized and the structures were characterized by ¹H NMR,¹³C NMR,melting point and HRMS.The results of controlled experiments showed that the reaction underwent radical pathway.3.A strategy for preparing 3-chloroalkyl quinoxaline ketone was developed by using HCl as the chlorine source through the combination of ring opening and1,3-difunctionalization of aryl cyclopropane.The advantages of this method are mild reaction conditions and wide range of substrates.31 substrates were prepared with good yields.The mechanism was discussed through control experiments.*All compounds were adequately verified by ¹H NMR,¹³C NMR,¹⁹F NMR and HRMS.