Cycloaddition Reactions With Pd-Butadienyl Intermediates

Cycloaddition reaction as one of the most efficient methods for organic synthesis have been widely applied in the preparation of natural products,active drug molecules,functional organic materials,catalysts(organocatalysts and ligands),dyes,spices and other field of scientific research.Since cycloaddition reaction has been proved to be environmentally friendly and atom efficient,chemists have devoted themselves to developing novel cycloaddition reactions.Therefore,the development of various cycloaddition reactions has attracted worldwide attention and been a new challenge in organic synthesis.Due to the importance of cycloaddition reactions,we developed new synthons to extend the scope of cycloaddition reactions,to solve the challenging issue in the related research area.This article focus on asymmetric cycloaddition reactions with allenyl acetate and conjugated enyne,and mainly consist of the following three chapters.In chapter 1,research progress on the functionalization of allenes has been summarized,including addition reaction of allenes with C-containing nucleophiles,N-containing nucleophiles,O-containing nucleophiles,S-containing nucleophiles,Si-containing nucleophiles and B-containing nucleophiles.Allenyl acetate are novel synthons,which have unknown and challenging reactivity,regioselectivity and stereoselectivity in cycloaddition reactions.In chapter 2,a Pd-catalyzed [4+1] or [4+3] cycloaddition reaction of allenyl acetate with pyrazolone resulting from a switch in catalyst(palladium and ligand)is described,providing a series of biologically active spiral-ring and fused-ring compounds in excellent yield and with high regioselectivity and stereoselectivity.In recent years,catalytic asymmetric regiodivergent and stereodivergent synthesis have become a frontier and an important synthetic strategy in the field of organic synthesis.In chapter 3,a new Pd-catalyzed [4+1] cycloaddition reaction of conjugated enynes with active methylene compounds is presented,affording a series of potential biologically active spiral-ring mptifs in excellent yield and with broad substrate scope,high regioselectivity and stereoselectivity.In particular,it is available to achieve enantioselective divergence through changing substrate l group on conjugated enynes.