Studies On Transition Metal Catalyzed 1,4 Migration Reactions For The Construction Of Polysubstituted Olefins/Aromatics

Polysubstituted olefins and aromatics are widely found in natural products,pharmaceuticals and organic materials.Therefore,the synthesis of polysubstituted olefins and aromatics is of great significance and value.Transition metal-catalyzed 1,4migration reactions can activate carbon-hydrogen bonds at specific sites on olefins and aromatics,resulting in the formation of new carbon-metal species that can then be functionalised.Therefore,the construction of multisubstituted olefins and aromatics by this method has great prospects for development.Although many cases of 1,4migration reactions catalyzed by palladium and rhodium have been reported.However,very few 1,4 migration reactions have been reported for the inexpensive metal nickel.Furthermore,the exploration of coupling reagents in transition metal-catalyzed 1,4migration reactions,such as the Catellani reaction,is important for the synthesis complex multi-substituted compounds.This dissertation explored and discovered the first aryl to alkenyl 1,4 nickel migration process,while the resulting alkenyl nickel intermediates were successfully trapped using haloalkanes and the corresponding highly E/Z stereoselective polysubstituted olefins were obtained.In addition,this dissertation explored the first application of cyclobutanol as a novel nucleophilic reagent for the synthesis of a series of polysubstituted aromatic hydrocarbons in the Catellani reaction.This dissertation consists of three main chapters as follows:Chapter ⅠThis chapter is organized around transition metal-catalyzed 1,4 migration reactions.In this chapter we will focus on the recent progress in the study of 1,4migration reactions catalyzed by transition metals.In addition,the progress of nickel-catalyzed reductive cross-coupling of haloalkenes and haloalkanes is also presented.Chapter ⅡIn this chapter,the author has developed an unprecedented aryl to alkenyl 1,4nickel migration strategy combined with reductive coupling reactions with brominated alkanes to synthesise a series of highly stereoselective trisubstituted olefins.The reaction conditions were mild and various functional group-substituted aryl olefin substrates and primary,secondary brominated alkanes were well suited for the reactions.Mechanistic verification experiments and theoretical calculations demonstrated that: the 1,4-nickel migration process occurs at the nickel(II)center and the migration reaction is reversible;while the migration process is accompanied by the reverse migration of hydrogen at the alkenyl terminus;the structure of the ligand backbone and substrate is critical to the migration process;and the migrated alkenyl Ni species are highly Z/E stereoselective.In addition,we have synthesized and reported for the first time some new substituted bipyridine ligands.Chapter ⅢIn this chapter,the author focused on the reference of the palladium-catalyzed ring-opening reaction of cyclobutanol to the Catellani reaction for ortho-site functionalization and ipso-site alkylation.The author described the reasons and advantages of using cyclobutanol as a coupling termination reagent for the Catellani reaction.All four types of electrophiles(N-benzoyloxyamines,alkyl iodides,aryl bromides,and benzyl chlorides)are quite compatible with this termination reaction for the construction of various types of polysubstituted aromatic hydrocarbons.