synthesis of 1-phenyl-l,3,5-hexanetrione; a crossed claisen condensation using a
ID: 996123 • Letter: S
Question
synthesis of 1-phenyl-l,3,5-hexanetrione; a crossed claisen condensation using a trianion introduction: using you class text (bruice), write a general description of the preparation and use of a carbonyl compound's alpha carbanion in a claisen condensation. Then describe this reaction, including how it differs from a classical claisen condensation and is a "crossed" claisen condensation. Describe very briefly the procedure for setting up and running the reaction and working up your reaction mixture to obtain the pure product.Explanation / Answer
Claisen condensation is a condenation reaction between two esters to form a beta-keto ester product. The reaction can be performed using only one type of ester in which case the ester has an carbon to which hydrogen is present known as self condensation clasien reaction or it can be performed by using an ester with alpha hydrogen and another with no alpha hydrogen, such types of reactions are known as mixed claisen condensation reaction.
The synthesis of 1-phenyl-1,3,5-hexanetrione starts with ethylacetate as the substrate. This is treated with a base as ethoxide in ethanol which forms a enolate of ester. The enolate is then reacted with another mole of ethylacetate to form a beta-keto ester product. In another flask, acetophenone is reacted with a base NaOEt to generate an enolate and is then reacted with the first formed beta-ketoester product to give the desired product. The reaction is quenched by aq.NH4Cl solution and is extracted with ethylacetate. The organic layer is washed with 10% aqNaHCO3 solution and then with water. Drying over MgSO4, filtration and evaporation of organic solvent gives the pure trione product.
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