Transition Metal Participation In The Synthesis Of Heteroaromatic Rings And Methylation Reaction Research

In organic chemistry,the direct construction of C-N and C-C bonds plays a very important role in the synthesis of natural products and drug molecules,which has attracted the attention of many chemists.Because of the high efficiency and good selectivity,C-H activation reactions catalyzed by palladium,rhodium,ruthenium,iridium,copper,silver,and cobalt have been developed.At the same time,due to the green characteristics ofα-oxocarboxylic acid with CO₂ as the only by-product has been utilized as green acylating reagent to replace acid chloride in the formation of C-C,C-N and C-S bonds.Transition-metal-catalyzed C-H methylation is an effective way to introduce methyl into molecules.Peroxides can be used not only as oxidants and free radical initiators,but also as effective methylation reagents.It is widely used in synthetic organic chemistry because of its high efficiency and green characteristics.This thesis studies the synthes is of multi-substituent quinolones through the silver-promoted C-H functionalization and the palladium-catalyzed direct methylation of aromatic C-H bonds.（1）Ag（Ⅰ）-promoted decarboxylative annulation ofα-oxocarboxylic acids with（E）-3-（2-aminophenyl）-1-phenylprop-2-en-1-ones toward 3,4-functionalized quinolines.The reaction is featured with the readily available starting materials simple reaction procedure,good substrate tolerance to deliver a series of 2,3-disubstituted quinolines in high yields.In the reaction,α-oxocarboxylic acid and（E）-3-（2-aminophenyl）-1-phenylprop-2-en-1-ones undergo intermolecular condensation and oxa-6π-electrocyclization to obtain the desired quinoline products.（2）Palladium-catalyzed direct methylation of indoles using peroxide as methyl source.In this reaction,palladium-catalyzed methylation of N-pyrimidine indoles with di-tert-butyl hydroperoxide was developed.In this work,pyridyl and pyrimidinyl are effective directing groups for the methylation reaction to afford a series of C2-methylated indoles.The pre-functionalization of substrates is not necessary.Besides,the use of peroxide as a methyl source is also more environmentally friendly and meets the requirements of sustainable development.This reaction developed an economical,reliable,safe and environmentally friendly approach for the synthesis of C2-methylated indoles as peroxides as the methyl source.This work provided a new avenue for the methylation of organic heterocyclic molecules.