Firedel-cratfs Reaction Catalyzed By Fluorinated Alcohols And Organo Bifunctional Catalysts

This thesis contains two parts:Part I: The regio-and stereo-selective Friedel Crafts alkylation ofarenes with epoxides is important in organic synthesis. These reactionsare generally catalyzed by Lewis acids which activate epoxides towardselectrophilic substitution. However, degradation and polymerization ofepoxides sometimes occur before electrophilic substitution in thepresence of strong Lewis acids. Therefore, to make this reaction anefficient transformation, it is necessary to suppress degradation andpolymerization side reactions.Firstly, we tried the intramolecular Friedel Crafts reacton of(phenoxymethyl)o-xiranes in pure water. It was found that the cyclicalkylation product wasonly obtained in moderate yield due to the hydrolysis of epoxide to diol side product. Based on this finding, we reasoned that a more acidic andpolar, but less nucleophilic solvent than water can make as a catalyst topromote this transformation.1,1,1,3,3,3-Hexafluoroisopropanol waschosen as the best solvent to promote the intra-and intermolecularFriedel Crafts reacton between arenes and epoxides with high regio-andstereo-selectivity.It was found that fluorinated alcohols could also promote thereactions which were traditionaly catalyzed by Lewis acids, and eventransformations that only could be catalyzed by metal.Part Ⅱ: Asymmetric Friedel–Crafts reaction between an aromaticcompound and an aldimine is an important approach for the preparationof optically active benzylic amines. Up to date, most asymmetricFriedel–Crafts reactions of aldimines are completed with heteroaromatics.We developed The first enantioselective Friedel–Crafts reaction catalyzedby natural amino acid derived bifunctional catalyst between electron-rich phenols and N-tosylaldiminesA series of bifunctional (amine/thiourea) catalysts weresynthesized and used in the model asymmetric Friedel–Crafts reactionbetween3,5-dimethoxylphenol andN-benzylidene-4-methylbenzenesulfonamide. We found the catalystderived from Leucine gave the highest enantioselectivity. AsymmetricFriedel–Crafts reactions catalyzed by this catalyst between electron-richphenols and aldimines were carried out with high regioselectivity, and upto96%yield and95%ee.