| Carboxylic acids and their derivatives play an important role in research laboratories and synthesis industries due to their simple availability,stable properties,and low environmental pollution.Carboxylic acids and their derivatives can release carbon dioxide by decarboxylation as multifunctional sites for building C-C and C-heteroatom bonds.Therefore,the coupling reaction involving carboxylic acid and its derivatives has become one of the fields that organic chemists are eager to study.Transition metal-catalyzed decarboxylation coupling has shown strong and efficient advantages in many reactions.However,most of these reactions require complex conditions such as high temperature and oxidant,with problems such as difficult handling of metal residues.Moreover,the transition metal-catalyzed coupling reaction for aliphatic carboxylic acids is rarely studied,which greatly limits its application.Different from traditional transition metal-catalyzed decarboxylation couplings,the development of photochemistry has brought new opportunities for decarboxylation coupling reactions.The visible light-mediated decarboxylation coupling reaction is easy to operate,with mild and efficient traits,so it is widely used by scientists in various fields of organic synthesis.N-Hydroxyphthalimide(NHP)ester is a stable and readily available radical precursor,which is easily decarboxylated to generate alkyl radicals under the irradiation of visible light,and is an ideal alkyl coupling reagent.At present,it has been realized for its coupling with functional groups such as alkenes,alkynes,(hetero)aryl groups.However,most of these reactions require the help of traditional photocatalysts such as polypyridine-substituted noble metals Ir and Ru.These reagents are expensive and cannot be used in industrialization.The application in production is very limited and the metal residue is not easy to deal with,which causes great pollution to the environment.In addition,for low-cost organic dyes,the low redox potential and short excited state lifetime limit their application range.Therefore,it is very necessary to develop a more green,mild,concise and efficient method to realize the decarboxylation coupling of carboxylic acids and their derivatives.In view of this,this paper focuses on NHP ester as alkyl radical precursor,cheap copper and1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene(4Cz IPN)as photosensitizer,and realizes the introduction of C(sp~3)radical under mild conditions.The main research contents include the following three parts:1.A brief overview of transition metal-catalyzed decarboxylation coupling of carboxylic acids and their derivatives and deacidification of NHP esters under visible light.Therefore,the research basis and significance of this thesis are put forward.2.The alkylarylation of alkenes was successfully achieved via copper-catalyzed decarboxylation and C(sp~2)-H functionalization under the mediation of visible light,C(sp~3)-C(sp~3)and C(sp~3)-C(sp~2)key were successful constructed.This reaction replaces noble metal photocatalysts with Cu(I)complexes generated in situ,with good economy,simple and mild conditions,wide range of substrate applications,and high functional group tolerance.In addition,this method can also be used for the modification of natural product fragments to generate a series of 1,1-diarylalkane derivatives that may have better activity.3.The visible light-mediated regioselective alkylation of chromone derivatives without metal participation was achieved.This method has the advantages of high energy group tolerance,wide substrate application range,high regioselectivity,and the ability to introduce quaternary carbon centers into natural products.In addition,we have extended this strategy to the alkylation of other heterocyclic compounds,such as coumarin,quinolinone,quinoxaline,etc.,and all the reaction can proceed smoothly,whose application value of this reaction is further improved. |
PDF Full Text Request