Study On The Reaction Of α,β-unsaturated Nitrones With Cumulative Diene Compounds

Cycloaddition reaction is one of the most important strategies to construct cyclic compounds.α,β-Unsaturated nitrone is a very important synthon in the field of organic synthesis.It can take part in many kinds of cycloaddition reactions and be converted to many heterocyclic compounds.Therefore,in recent years,it has attracted much attention by organic chemists.In this paper,we mainly studied the reaction of α,β-unsaturated nitrones with ketenes and allenoates under different conditions to afford polysubstituted γ-lactone compounds and N-vinylindole carboxylic ester compounds.This thesis is divided into two parts:In the first part,a new oxygen transfer has been designed,which can be used to synthesize γ-(pyridyl-2-yl)lactones and γ-ketolactones with three chiral centers in one pot through copper catalyzed [5+2] cycloaddition reaction of N-vinyl-α,β-unsaturated nitrones and ketenes in air over three steps conversion,containing N-O bond rearrangement,6π electron cyclization and aromatization.The strategy has the advantages of gram scale preparation,high atomic economy,easily available raw materials,broad substrate scope,and invoving novel O-transfer reactions.At the same time,the obtained γ-(pyridyl-2-yl)lactones through this new strategy had good yields and high diastereoselectivity.In the second part,the strategy for the synthesis of N-vinylindole carboxylic esters by the reaction of N-aryl-a,β-unsaturated nitrones with allenoate catalyzed by nickel catalyst was developed.The effect of temperature,solvent and metal catalyst on the formation of N-vinylindoles was investigated.The aromatic rings of nitrones whether containing electron-donating or electron-withdrawing groups can deliver the target products in good to excellent yields.The reaction underwent [3+2] cycloaddition,[3,3]-rearrangement,retro-Mannich reaction,and 1,4-addition to afford various N-vinylindole carboxylic esters.Further experimental studies showed that the addition of nickel catalyst in the reaction can effectively improve the reaction efficiency.