Study On The Application Of Benzannulation In The Synthesis Of Unsymmetrical Sulfones And Dihydrobenzo[f]Phthalazines

Polysubstituted benzenes are highly important structural units in natural products.Therefore,their syntheses have been attracted more attention.Benzannulation reactions have been proven to be one of the most powerful and reliable approaches to synthesize polysubstituted benzene derivatives,which have been widely applied to build complex aromatic compounds.In this dissertation,radical-enabled or iodine-mediated intramolecular benzannulation reactions for the synthesis of three kinds of complex aromatic compounds have been described.During reaction processes,the polysubstituted benzenes are synthesized in one-pot manner,avoiding the isolation of intermediates.The starting materials have been maximized to convert into the desired compounds by using different metal or metal-free catalysts.This dissertation consists of the following four parts:In the first section,the background and characteristics of benzannulation reactions were introduced,and the types of the reaction also have been described.Furthermore,on the basis of these report surveys,the topic selection,significance and novelty of this dissertation were also presented.In the second section,a bimetallic Cu/Fe-co-catalyzed radical cyclization of unactivated 1,5-enynes has been developed.Cu(OTf)2/FeCl2-co-catalyzed benzannulation reactions of unactivated 1,5-enynes with commercially available aryl sulfonyl hydrazides in the presence of di-t-butyl peroxide(DTBP)have been carried out,which underwent the in situ generated sulfonyl radical-triggered 6-endo-trig cyclization to directly form naphthyl sulfones with simultaneous realization of the control of reaction selectivity.The benzannulation reaction led to the formation of C-S and C-C bonds under oxidative conditions,providing a facile and efficient method for the direct construction of unsymmetrical diaryl sulfone skeleton.In the third section,a new Cu-catalyzed radical cyclization of 2-arylalkynyl-1,1'-biphenyls has been reported.Using unactivated 2-arylalkynyl-1,1'-biphenyls and aryl sulfonyl hydrazides as starting materials and Cu(OTf)2 as a catalyst,the reaction in the presence of DTBP readily proceeded,enabling the in situ generated sulfonyl radical-triggered 6-endo-trig cyclization and homolytic aromatic substitution(HAS)to access structurally diverse phenanthryl sulfones.This benzannulation reaction worked well under air conditions and featured simple operation,offering a valuable addendum to methodology for constructing unsymmetrical diaryl sulfone framework.In the fourth part,a new iodine-mediated bicyclization of 1-(2-(arylethynyl)phenyl)buta-2,3-dien-1-ones has been developed.The one-pot two-step bicyclization of 1-(2-(arylethynyl)phenyl)buta-2,3-dien-1-ones and aryl sulfonyl hydrazides mediated by TBHP and I2,gave dihydrobenzo[f]phthalazines.This metal-free transformation proceeded smoothly,resulting in the formation of two new rings including phenyl and pyridazine and several C-C and C-N bonds.The reaction features mild reaction conditions(under air conditions),simple operation and good functional group tolerance as well as wide substrate scope.