Free Radicals Promoted C-H Functionalization Reaction

C-H bonds are widely present in organic compounds.Direct C-H bonds functionallizationhas become an effective method for building C-C,C-X,C-O and C-N bonds.In recent years,free radicals involved in the C-H functional groups favored by chemists,alkane compounds in the free radical initiator under the action of carbon free radicals in order to achieve its functional group.In this paper,the application of palladium and ruthenium catalysts in the C-H functionalization of free radicals is extended.The main contents of this paper include the following three parts.In the first part,the progress of C-O bonding,free radicals in the reaction of C-H functionalization and meta C-H reaction have been well reviewed.In the second part,a practical palladium-catalyzed direct acyloxylation of C（sp²）-H and C（sp³）-H bonds under the assistance of oxalyl amide with TBPB as oxidant was developed.Selective acyloxylation of C（sp²）-H bond for oxalyl amide protected benzyl amine using TBPB or carboxylic acids as acyloxylating reagent was achieved.For oxalyl amide protected 2-alkylanilines,the selective acyloxylation of benzylic C（sp³）-H bond was also achieved.This protocol provided an efficient and practical method for the synthesis of aryl esters.In the third part,a C³_sp radical promoted ortho-and meta-alkylation reaction of2-arylpyridines in the presence of Ru-catalyst.In the presence of DTBP,alkanes can be oxidized to generate carbon radicals.Carbon radicals can react with2-arylpyridines to afford ortho-alkylation products in the presence of Ru-catalyst or to give meta-alkylation products in the presence of DNDHP and Ru-catalyst.All the structures of product are identified by their ¹H NMR,¹³C NMR and HRMS.