Acidic Molecular Sieves Catalyzed Rearrangement Reactions

Rearrangement reaction is the intramolecular migration process of group or atom.The traditional catalysts of rearrangement reactions are mainly strong protonic acids and precious metals.Acidic molecular sieve has both Br?nsted acid and Lewis acid.Molecular sieves are expected to become a new generation of environmentally friendly catalysts.This is mainly due to the fact that molecular sieves have uniform channel size,high external surface area,and unique molecular shape selectivity,as well as strong acidity,adjustable acid center and good thermal/ hydrothermal stability.Besides,metal with catalytic activity can also be exchanged into crystals.These structural character make it an effective acid catalyst and catalyst carrier.This thesis is to research on Meyer-Schuster rearrangement and Pinacol rearrangement reactions which are widely used in fine organic synthesis.Acidic molecular sieves are used to catalyze the Meyer-Schuster rearrangement reactions in solvent-free system.And also,we expanded the application of the system for one-pot reactions.The specific research work shows as follows:(1)Preparation,characterization of acidic molecular sieves that possesses different acidic and textural propertiesAcidic Al-containing molecular sieves with different acidic or textural properties were synthesized with hydrothermal method and we used as catalyst for Meyer-Schuster rearrangement.From structure characterization perspective,There are mesoporous molecular sieve like MCM-41,SBA-15 and microporous molecular sieve like USY,MCM-22,ZSM-35.Nitrogen adsorption/desorption analyses indicated that MCM-41 has the maximum external surface area.From acid characterization perspective,molecular sieves like USY,MCM-22 and ZSM-35 are mainly of Br?nsted acid,molecular sieves like MCM-41 and SBA-15 are mainly of Lewis acid.Molecular sieve MCM-41 possessed the largest amounts of external acid sites.(2)The research and application of Meyer-Schuster rearrangement catalyzed by molecular sievesAn efficient and environmentally benign heterogeneous catalytic system hasbeen developed for the Meyer-Schuster rearrangement of propargylic alcohols for the preparation of widely used ?,?-unsaturated carbonyl compounds efficiently.Different types of acidic Al-containing molecular sieves were used as the catalysts in organic solvent-free system.The reaction results were explained through the comparing of different molecular sieve catalysts in structure and acidity,and the reaction mechanism were explored through Variable-controlling approach,finding intermediates with chemical method and Gaussian calculation.Notable advantages offered by this strategy are absence of organic solvent,broad substrate scope,potential value in industry for gram-scale preparation and use of non-hazardous catalysts which could be recycled for four times and maintain its reactivity unchangeable.In addition,two tandem protocols that Meyer-Schuster rearrangement-nucleophilic addition for unsaturated oxime and Meyer-Schuster rearrangement-[3+2] cycloaddition for substituted dihydrofuran were successfully developed with one-pot reaction,which is based on the organic solvent-free system of Meyer-Schuster rearrangement catalyzed by molecular sieve catalysts.(3)Pinacol rearrangement catalyzed by USYThe cheap and commercially available molecular sieve catalyst USY were used to catalyze pinacol rearrangement reaction in toluene.Different types of substituted carbonyl compounds were obtained with excellent selectivity(mainly benzene migration products)and high yields,also catalyst can be used five times without significant change in activity and gram-scale preparation was achieved,which indicate potential industrial application.On this basis,the solid-solid pinacol rearrangement reaction is achieved with middle yields.This system is easily prepared without any solvent,which is of some significance for green catalyzed pinacol rearrangement using molecular sieves.