| C-H bonds activation has been recognized as one of the most effective methods for the construction of carbon-carbon bonds.One protocol of this series is the Catellani reaction.Through Pd/NBE cooperative catalysis,the Catellani reaction can selectively introduce electrophiles at the ortho position of aryl halides via C-H bond functionalization.Concomitantly,nucleophiles were cross-coupled at the ipso position of aryl halides to achieve multi-functionalization of aryl halides and synthesizing structurally diverse,multi-substituted aromatic compounds in a one-pot manipulation.The reaction protocol has found wide utility in the synthesis of natural products,pharmaceutical intermediates,and optoelectronic materials.On the other hand,aryldiazonium salts are a class of organic intermediates with diversified reactivities.One important synthetic use of aryldiazonium salts is electrophilic arylation with a large variety of organic nucleophiles.This thesis investigates the Catellani type reaction of aryl diazonium salts with iodoarenes under Pd/NBE cooperative catalysis,with a aim to find new synthetic protocols towards polyfunctionalized biphenyls.This thesis consists of three chapters,the main contents are listed as below:Chapter 1: Nucleophiles in the Catellani reactions.This chapter briefly introduces the commonly used nucleophiles in the Catellani reaction.Nucleophiles are organized with different hybridization types of termination reagents.Chapter 2: Study on the Catellani type arylation reactions of aryl diazonium salts with iodoarenes under bimetallic catalysis.This chapter presents an interesting Catellani-type employ aryl diazonium salts as electrophilic reagents,ortho-substituted iodoarenes as the substrates and alkenes as terminating reagents.In the presence of Cu I,aryl groups of diazonium salts were converted into aryl radicals and were regioselectively installed at the ortho-position of iodoarenes.Simultaneously,Heck coupling reaction occurred and alkene moieties were installed at the ipso position of iodoarenes.Experimental studies showed that the addition of cuprous iodide can in situ transform aryl diazonium salts into aryl radicals,realizing the Catellani radical coupling reaction for the first time.Notably,these reactions showed excellent regioselectivity as only ortho-arylation products were obtained.Chapter 3: Catellani-type decarboxylative cyclization reaction of aryl diazonium salts.In this chapter,Catellani-type reactions that employ aryl diazonium salts as substrates,2-bromobenzoic acids as the ortho-functionalizing reagents and2,5-norbornadiene as the co-catalyst a well as acetylene precursor,was developed to synthesize phenanthrenes.This new synthetic protocol further broaden the utility of aryl diazonium salts in the Catellani reactions. |
