Palladium Catalyzed Hydroarylation/Hydroesterification Of Allenes

The allenes are a class of unsaturated hydrocarbons with 1,2-propadiene functional group,which have high reactivity in organic reactions.The allenes and their derivatives play an important role in organic synthesis and natural products.In recent years,transition metal-catalyzed functionalization reactions of allenes are one of the hot areas of modern organic synthesis research.Therefore,the development of simple,efficient and green synthetic methods to realize the functionalization reactions of allenes is a development direction of current research.In this thesis,two functionalization reactions,hydroarylation and hydroesterification,of allenes with aryl formates were investigated:Part I:Hydroarylation of allenes with aryl formatesAllyl and its derivatives are crucial compounds in organic synthetic chemistry and natural product chemistry,so exploring an available method to react simple and readily available raw materials to generate allyl derivatives is an important direction in modern organic synthesis.The exploration of the efficient conversion and reaction of allenes as raw materials to generate allyl compounds and cyclization products is one of the hot research topics in modern organic synthesis.In this work,the transition metal palladium was used to catalyze the hydroarylation reaction of allenes with aryl formates to produce allylphenols.The reaction was performed by adding 5 mol%palladium acetate catalyst,10 mol%1,1’-binaphthyl-2,2’-bis（diphenylphosphine）（BINAP）,1.5 equivalents of cesium carbonate and1 equivalent of water,which could get the only E-form hydroarylation products in high yield.The reaction is characterized by mild conditions and simple operation.The template reaction could be scaled up to the gram scale with good yields,and a benzoheptadecyclic lactone was synthesized by derivatization of the template product.Part II:Hydroesterification of allenes with aryl formatsCarboxylic acids and their derivatives are a class of compounds with pharmaceutical activity and have important development prospects in chemical production and biomedicine.Transition metal-catalyzed carbonylation reactions are currently one of the most important methods to generate carboxylic acids and their derivatives.Therefore,we investigated the palladium-catalyzed hydroesterification reaction of bifene with formic acid esters and achieved the selective generation of both branched and straight chain hydroesterification products in moderate yields by modulation of the ligands:the addition of 5 mol%Pd（OAc）₂catalyst,10 mol%dppm as ligand and 40 mol%HCOOH as additive resulted in the generation of a single branched hydroesterification product;the addition of 5 mol%Pd（OAc）₂ catalyst,10 mol%Xantphos ligand can generate straight chain hydroesterification products with higher selectivity We also propose a possible mechanism for the hydroesterification reaction of the allenes.However,this topic requires further optimization of experimental conditions to improve the yield and expand the substrate.