Synthesis Of Ferrocenyl L-proline Derivatives Chiral Organocatalysts And The Catalytic Effects On The Asymmetric Direct Aldol Reaction

Intrducing ferrocenyl into different molecules, design and synthesis offerrocene as the skeleton or containing ferrocenyl or special performancecompouds is a hot topic of ferrocene chemical research in recent years, the designand synthesis of planar chiral ferrocene derivatives and their applications inasymmetric catalysis is opened up a new area of research in ferrocene chemistry.In this paper, two ferrocenely chiral derivatives were synthesized usingL-proline and ferocene as raw materials. In organic phase and water phase, weresearched direct asymmetric aldol reaction of aldehyde catalyzed by them in neatacetone. The main work includes the following three aspects:1、L-Prinoylferrocene which is a small molecule are synthesized in four stepsfrom L-proline and ferrocene through the reaction sequence of protection, acylchlorination, Friedel-Crafts acylation, remove protecting group. AsL-(N-ethyl)Prinoylferrocene are synthesized in three steps from L-proline andferrocene through the reaction sequence of ethylation, acyl chlorination,Friedel-Crafts acylation. The structures are characterized by means of IR and1H-NMR. Third step is Friedel-Crafts acylation reaction, dichloromethane assolvent, zinc oxide is select as lewis acid catalyst, compare with aluminiumtrichloride which is environmental Friendl,yand the yield reached43%and36%.This article preliminarily discusses the synthesis of Ferrocenyl L-prolinederivatives.2、We studied the two compounds application in the direct asymmetric aldolreaction. The catalytic activity and enantioselectivety of L-Prinoylferrocene andL-(N-ethyl)Prinoylferrocene in the Aldol reaction have been studied in organicphase in the influence of different solvent，temperature and the amount of catalystetc. The results indicated that whenonly5mol%of L-Prinoylferrocene wasused，both the activities and selectivities were similar to30mol％of L-Prinoylferrocenein acetone. The mean is using only5mol%this organocatalyst，the reaction cangive high enantioselectivity of up to90%enantiomeric excess for the direct aldolreaction of various aldehydes with acetone. But, Direct asymmetric aldol reactionof benzaldehyde catalyzed by L-(N-ethyl)Prinoylferrocene in neat acetone onlyget low enantiomeric excess.3、Enviroment friendly is one of the important aspects in chemistry field. In organic reactions, a large number of literatures reported the use of water as anadditive or water is used as the reaction medium to replace traditional organicsolvent. So we also examined the asymmetric aldol reaction with aldehyde whichcatalyzed by5mol%organocatalyst in aqueous media and obtained high yield andenantioselectivities in this reaction system.