Study On Knoevenagel Condensation In Aqueous Medium

In recent years, With the rapid emerging and development of green chemistry， moreand more scientists focus on the organic synthesis inenvironment friendly medium insteadof harmful organic solvent, there are many potential advantages of replacing the unnaturalorganic solvents with water, such as cheap, safe, and environmental.The Knoevenagel condensation is one of the most useful carbon-carbon bond formingreactions in ogranic synthesis.The Knoevenagel condensation of aldehydes with activemethylene com.p.ounds had been commonly em.p.loyed in the synthesis of numerouschemicals and chemical intermediates. The main work in this dissertation is about theinvestigation on the Knoevenagel condensation in water. The contents are listed as thefollowings:1. Basic ionic liquid [Bmim] OH had been synthesised and catalyzed Knoevenagelcondensation of aldehydes and ketones with active methylene groups in aqueous media.Experiments show that Aromatic aldehydes with active methylene com.p.ounds such aspropanedinitrile, ethyl cyanoacetate can carry out condensation reaction smoothly at roomtem.p.erature. Low activity of ketones with propanedinitrile in this reaction system can alsobe carried out smoothly, the method has some advantages such as milder reactionconditions, sim.p.le operation, short reaction time, high yield, the catalyst can be reused.this method is a green synthetic method.2. In aqueous medium, L-Phenylalanine as catalyst, a series of aromatic aldehydesreacted with barbituric acid or thiobarbituric acid had obtained pharmacological andphysiological activity of5-arylidene barbituric acid and thiobarbituric acid. The methodprovided several advantages such as excellent yieds sim.p.le operation, mild reactionconditions, short reaction time. It had provide a green and convenient method for thesynthesis of5-arylidene barbituric acid and thiobarbituric acid.3. In aqueous medium, L-histidine can effective catalytic the reaction between aromaticaldehydes with rhodanine in water, the reaction system without addition of surfactant,avariety of5-arylidene rhodanine which have pharmacological and physiological activityfrom the corresponding aromatic aldehydes and rhodanine in83%-94%yields. The present protocol offered several advantages including mild conditions, high yields, short reactiontime, and sim.p.le work-up procedure,avoid the use of volatile and toxic organic solvents.In summary, the basic ionic liquid [Bmim]OH and natural amino acid can efficientlycatalyzed Knoevenagel condensation in aqueous medium. The present procedure isendowed with some merits, such as mild reaction conditions, sim.p.le operation, high yield,environmentally friendly. the protocol is in line with demand of green chemistry.