Study On The Tandem Reactions Of Alkenes For The Synthesis Of Cyclic Compounds

In recent decades, tandem reaction under the transition-metal catalysis or metal-free conditions has emerged as an effective method to analyze synthesis of benzene ring and heterocyclic compounds through the formation of the C-C and C-Heteroatom bonds in orgnic synthesis. As a result, the tandem reaction has been become an important modern synthetic organic chemistry synthesis tools to access a large number of pesticides, pharmaceuticals, natural products and new materials. This dissertation, includes ruthenium-catalyzed tandem cyclization of 1,6-enynes with arylsulfonyl chlorides using visible light photoredox catalysis, palladium-catalyzed synthesis of 3-alkyl oxindoles, metal-free nitrative cyclization/isomerization of N-aryl imines with tert-butyl nitrite to access 3-nitroindoles, and tandem reaction of N-（o-alkenylaryl）-imines with aryl diazonium tetrafluoroborates.This dissertation is divided into five chapters, the main contents are as follows:（1） In chapter 1, recent progress in the cyclization of 1,n-enynes and tandem cyclizaiton of alkenes to synthesize cyclic compounds is described. We discuss these transformations in detail based on catalysts, reaction type and possible reaction mechanism.（2） In chapter 2, a new tandem cyclization of 1,6-enynes with arylsulfonyl chlorides triggered by visible light photoredox catalysis is described, in which 1,6-enynes are employed as the radical acceptors to allows the formation of a diverse range of 10 a,11-dihydro-10H-benzo[b]fluorene architectures in one step. Extensively Screening on catalysts, bases, solvents and reaction temperatures revealed that a combination of Ru（bpy）3Cl2?6H2O（10 mol%）, Na2CO3（1 equiv） and blue 5W LED light at 40 oC for 12 h was optimal for tandem cyclization of 1,6-enynes with arylsulfonyl chlorides, providing diverse functionalized 10 a,11-dihydro-10H-benzo[b]fluorene in good yields. Most importantly, a thematic extension is established that arylsulfonyl chlorides provide an ortho-C（aryl）-H bond to participate in the tandem cyclization besides the formation of aryl radicals by removing the SO2 Cl group. This present protocol extends the scope of enyne cyclizations and represents a new synthetic utilization of arylsulfonyl chlorides.（3） In chapter 3, a novel palladium catalyzed selective synthesis of 3-alkyl oxindoles was developed. In the present of Pd（dba）2（10 mol%）, Xantphos（10 mol%）, Ag（OAc）（2 equiv）, Na HCO3（2 equiv） and argon, a variety of 3-chloro-2-iodo-N-aryl acrylamides underwent the tandem reaction with allyl alcohols to afford 3-alkyl oxindoles in moderate to good yields. Notably, the kinetic isotope experiments imply that 3-chloro-2-iodo-N-arylacrylamides lost a carbon atom during the tandemprocess.（4） In chapter 4, a metal-free nitration, cyclization and isomerization cascade of N-aryl imines with tert-butyl nitrite（TBN） is established for the synthesis of 3-nitroindoles through oxidative cleavage of multiple C-H bonds. In the present of TBN（2 equiv） and dioxane solvent, the reaction of N-aryl imines at 70 oC under air atmosphere for 24 h afforded 3-nitroindoles in moderate to high yields. The H₂¹⁸O-labeled experiment showed that all the oxygen atoms in the NO2 group of the products are from water.（5） In chapter 5, a new method of N-Ethylidene-2-styrylanilines and aryl diazonium tetrafluoroborate compounds tandem reaction in 5? molecular sieve synthesis of 2H-pyrazolo[3,4-c]quinolines was developed. In the present of N-ethylene styrene aniline（0.3 mmol, 1.0 equiv）, aryl diazonium tetrafluoroborate（0.6 mmol, 2.0 equiv）, 5? molecular sieve（400 mg）, under the protection of argon and stirring at 100 oC for 24 h, a variety of N-Ethylidene-2-styrylanilines and aryl diazonium tetrafluoroborate underwent the tandem reaction with allyl alcohols to afford the corresponding products. A variety of functional groups of 2H-Pyrazolo[3,4-c]quinolines derivatives were synthesized under the optimal conditions. In this reaction aryl diazonium tetrafluoroborate retain nitrogen and participate in tandem cyclization reaction.