Heterogeneous Gold(?)-Catalyzed Synthesis Of Vicinal Tricarbonyls,N-Acylhydrazones And Benzo[b]Oxepines

This thesis investigated the applications of mesoporous MCM-41-immobilized phosphine-gold(?)complexes in gold(?)-catalyzed oxidation of internal acylalkynes toward vicinal tricarbonyls,hydrohydrazidation of terminal alkynes leading to N-acyl-hydrazones and cyclization of(o-alkynyl)phenoxyacrylates with alcohols for the assembly of benzo[b]oxepines.The research work mainly includes the following three parts:1.First,we prepared a mesoporous MCM-41-supported diphenylphosphine-gold(?)complex(MCM-41-PPh₂-AuNTf₂)via a simple procedure according to the reported method.Then the application of this supported gold(?)catalyst in the catalytic oxidation of internal acylalkynes towards vicinal tricarbonyl compounds was studied.The results showed that in the presence of 5 mol%MCM-41-PPh₂-AuNTf₂ and 2,6-dichloropyridine N-oxide as the oxidant,the oxidation reaction of a wide range of internal acylalkynes proceeded smoothly under mild reaction conditions,providing a wide variety of vicinal tricarbonyls such as?,?-diketoesters,1,2,3-triketones,and?,?-diketoamides in good to excellent yields.This heterogeneous gold(?)catalyst could be separated from the product by simple filtration and reused at least seven times without significant loss of catalytic activity.2.We have designed and synthesized a novel supported diphenylphosphine-gold(?)complex(MCM-41-2PPh₂-AuNTf₂)from readily available starting materials,and the structure of the gold complex was characterized by using different physico-chemical techniques.Then the catalytic behavior of the novel supported phosphine-gold(?)catalyst(MCM-41-2PPh₂-AuNTf₂)in the addition reaction of terminal alkynes with various hydrazides towards N-acylhydrazones was studied.The experimental results showed that the new supported gold(?)catalyst can catalyze the hydrohydrazidation reaction of terminal alkynes with hydrazides efficiently within a shorter time under mild conditions,delivering a variety of N-acylhydrazones in good to excellent yields.This reaction is insensitive to the electronic and steric effects of the substituents in the reactants and displays high functional group tolerance.The new heterogeneous gold catalyst can be recycled up to eight times with almost consistent catalytic activity.3.We investigated the application of MCM-41-supported diphenylphosphine-gold(?)complex(MCM-41-PPh₂-AuNTf₂)in the cyclization reaction of(o-alkynyl)phenoxy-acrylates with various alcohols towards functionalized benzo[b]oxepines.The results showed that in the presence of 5 mol%MCM-41-PPh₂-AuNTf₂,the cyclization reaction of a range of(o-alkynyl)phenoxyacrylates with different alcohols proceeded smoothly at room temperature,affording a variety of functionalized benzo[b]oxepines in good to excellent yields.Notably,the use of vinyl ether instead of alcohol as the nucleophile could produce the same product with better yield.The heterogeneous gold(?)catalyst could be separated from the product by simple filtration and reused at least seven times without apparent loss of catalytic efficiency.