Studies On Organic Reactions In Aqueous Solutions Catalyzed By Organocatalysis

Organocatalysis and organic reactions in aqueous solution are bothvery attractive research fields of organic chemistry. Compared with themetal catalyst, organocatalysts have unique advantages e.g. highstereoselectivity, mild reaction conditions, nontoxic, cheap, separate fromproduct conveniently and environment friendly. Organic reactions inaqueous solution avoid the use of organic solvents so as to reduce cost ofproduction and pollution. In recent years, amino acids organocatalystshave attracted increasing attention and become a hot topic for catalyticasymmetric synthesis, because its unique advantages of high selectivitysimilar to enzyme.Cinnamon oil is one of the special products of Guangxi. Therefore,research and development on cinnamon oil is very important forGuangxi’s economy. This dissertation selected cinnamaldehyde as theresearch substrate to explore the possible new product. The main studiesinclude:1) Eight amino acids e.g. L-glycine (Gly), L-proline (Pro),4-hydroxy-L-hydroxyproline (Hyp), L-leucine (Leu), L-lysine (Lys),D-phenylalanine (Phe), L-serine (Ser), L-glutamate (Glu) have beenemployed as the small molecular organocatalyst for hydration ofcinnamaldehyde. The effects of amino acid structure, reaction time andtemperature on the conversion of cinnamaldehyde and reaction selectivityhave been investigated. It was found that all of these amino acids caneffectively promote the hydration reaction of cinnamaldehyde at room temperature in aqueous solution, the reaction of cinnamaldehydeconversion rates are high and have reached more than86%. In sharpcontrast to the blank test whithout any catalyst in which almost noreaction. Thus, it can see that the amino acid catalyst with high catalyticactivity for the hydration reaction of cinnamaldehyde.2) Kinetic study of the hydration reaction catalyzed by eight aminoacids respectively indicates the reaction is a First-order reaction. Throughmeasuring the hydration reaction at different temperatures, the activationenergy of the hydration reaction catalyzed by various amino acids hasbeen calculated, and they are in the order of:4-hydroxy-L-hydroxyproline<L-proline <L-leucine <L-lysine <D-phenylalanine <L-serine <glycine <L-glutamate.3) The hydration product has been characterized with differentspectroscopic method. The possible structure is3-hydroxy phenylpropylaldehyde. The reaction mechanism and structure-activity relationship ofdifferent catalysts on the hydration reaction of cinnamaldehyde have beeninvestigated. It was found that the reaction can be carried out only in thepresence of both amine and carboxyl groups exist together. A reactionmechanism has been proposed, and verified with quantum chemicalcalculation on electron distribution of the transition state. Because thehydration reaction catalyzed by organocatalysts has never been reported,therefore, this work is helpful for study of small organocatalysts anddevelop new organic reactions in aqueous solution.