Study On The Synthesis Of Benzodihydropyran Derivatives

Recently,the cascade reaction of propargy alcohols has attracted considerable attentions of organic chemists because of its merits such as high efficiency and atomic economy.Initially,propargylic alcohol is converted to the allenyl cation intermediate in the presence of acid.Then the allenyl cation intermediate was attacked by inter-/intramolecular nucleophiles,followed by intramolecular cyclization to afford various functionalized carbocyclic or heterocyclic compounds.On the basis of previous reports,this thesis focuses on the construction of 2H-chromene skeletons using propargylic alcohol synthons,which includes the following three parts.1.We have developed HX or TMSCl mediated cascade cyclization of propargylic alcohols for the synthesis of 4-halo-2H-chromene derivatives under mild conditions.This reaction proceeds smoothly in excellent yields with a wide range of substrate compatibility.Moreover,the 4-halo-2H-chromene products can be further applied by array of palladium-catalyzed cross-coupling reactions to various functionalized 2H-chromenes.2.We disclosed a Cu(I)-catalyzed cascade cyclization of 2-propynolphenols and diarylphosphine oxides as the nucleophiles for the synthesis of 4-phosphorylated 2H-chromenes.On the basis of control experiments,these results clearly indicate that allenylphosphoryl compound is involved in this novel transformation.3.Using the method established in this article,the total synthesis of natural product 2,2-dimethylchroman-6-acrylic acid was firstly finished.We started with 2-(2-methylbutynol)phenol as a starting material,after cyclization,reduction,formylation and condensation of a total of 4 steps,generating the target product in a 54% overall yield.2H-chromene derivatives have excellent biological activities and play an important role in the fields of pharmaceutical chemistry and materials science.This paper will provide synthetic strategies for the synthesis of biologically active molecules containing such scaffolds.