Preparation Of Ion-pair Supported Organic Small Molecular Catalysts And Their Catalytic Properties For Asymmetric Reactions

Asymmetric organic small molecule catalysis is a developing field of modern organic chemistry.Because of its rich sources,cheap and easy to obtain,high efficiency and stability,wide applicability and environmental friendliness,the organocatalysts have attracted great interest and have become a hot research topic in the field of asymmetric catalysis in recent years.Although the organic small molecule catalyst has many advantages,it has the unavoidable drawbacks of homogeneous catalytic process such as low thermal stability and the difficulties in catalyst separation and recycling etc.In order to overcome the shortcomings of small molecular catalysts in homogeneous catalysis,the immobilization of organic small molecules has become a new challenge for chemists.At present,covalent bond is the most common immobilization for organic small molecules.Different from the covalent bond immobilization,this paper uses the noncovalent bondto support proline and Sinkonin,and also discuss the its catalytic properties and reusability for asymmetric Aldol,Mannich and Michael reactions.1.Preparation of Merrifield resin supported polyvinyl polyamine/L-proline catalyst and their catalytic performance for asymmetric Aldol reaction.Aminated Merrifield resin was synthesized by halogenation reaction.The synthetic amination resin and proline were used in asymmetric aldol reaction of aldehydes and ketones.Their catalytic properties were systematically investigated.The results showed that the triethylenetetramine supported on Merrifield resin/L-proline catalyst system had good catalytic performance,and the corresponding products obtained good enantioselectivity(ee:86%)and diastereoselectivity(dr: 35: 65),and without lowering the value of the product ee,the catalyst can be reused at least twice.2.Preparation of Merrifield resin supported pyridine / L-proline catalyst and its catalytic performance for asymmetric Aldolo,Mannich reaction.The pyridine organic salt supported on merrifield resin was prepared by quaternary ammonium reaction.The organic salt supported by this polymer was used in aldol reaction together with proline.The results showed that the heterogeneous catalyst as a high efficiency and a recoverable catalyst was used in asymmetric hydroxyaldehydes condensation reaction,and the corresponding Aldol product obtained diastereoselectivity(dr: 54:46-18:82)and enantioselectivity(ee: up to 92%).3.Preparation of Merrifield resin supported tertiary amines/ L-proline catalysts and their catalytic performance for asymmetric Aldol reaction.The polymer quaternary ammonium salts synthesized by the reaction of Merrifield resin with tertiary amines,which catalyzed Asymmetric aldol reaction with L-proline.In addition,quaternary ammonium cations of polymers can be bound with L-proline in the form of ion pairs to realize the loading of organic small molecules.The results showed that the catalyst could catalyze asymmetric aldol reaction with high selectivity in trace water.The corresponding product obtained 6:94 dr value and up to 98% ee value,and the catalyst system had good reusing performance.4.Preparation of polymer anionic supported cinchonine catalyst and their catalytic performance for asymmetric Michael reaction.Using polystyrene sulfonic acid and polyacrylic acid as carriers,cinchonine was supported on the polyanionic carrier through ion exchange.The prepared catalyst was used for asymmetric Michael reaction of ethyl cyclopentanone-2-acetate with N-benzyl maleimide.The results showed that the product obtained good enantioselectivity but low enantioselectivity.