Named reactions Dieckmann condensations

B.ii. The Dieckmann Condensation. Just as there is an intramolecular version of the aldol condensation, there is an intramolecular version of the Claisen condensation but it has been given a different name, the Dieckmann condensation. 109,110 reaction involves intramolecular cyclization of an a, co-diester such as... 

Notice once again that the product is just a P-keto ester. This reaction has its own name (the Dieckmann condensation). But it is really just an intramolecular Claisen condensation. Therefore, the steps of this mechanism are identical to the steps of a regular Claisen condensation. Propose a mechanism for the Dieckmann condensation. Try to do it without looking back at your previous work. You will need a separate piece of paper to record your answer. 

Condensation reactions of the aldol type play an important part in heterocyclic chemistry. There are a large number of condensation reactions that are closely related to the aldol condensation. Each of these reactions has its own name Claisen, Dieckmann, Doebner, Knoevenagel, Perkin, to mention a few, but the chemistry is essentially the same as that of the aldol condensation. 

The Dieckmann condensation is an intramolecular reaction by which cyclic P-keto esters are formed using tethered di-esters under basic conditions. The name derives from its originator, Walter Dieckmann, who first reported the reaction in 1894 and demonstrated the formation of ethyl p-ketocyclopentanecarboxylate from ethyl adipate using sodium base and, in a similar fashion, the formation of p-ketocyclohexanecarboxylate from ethyl pimelate. ... 

When the Claisen ester condensation is intramolecular, it goes by the name of the Dieckmann condensation. As with the intramolecular aldol reactions, only processes that give rise to five- or six-membered rings are favorable (Figure 17.33). This process has been used in the total synthesis of prostaglandin A2 (Figure 17.34). 

An example is the synthesis of ethyl a-ethoxalylpropionate (R = CH,) in 70% yield. Ethyl oxalate and ethyl succinate form ethyl a-ethoxalyl-succinate (83%). In a mixed ester condensation, the use of a more reactive ester, such as the phenyl or biphenyl ester, helps to prevent side reactions. Simple heterocyclic esters, namely, ethyl nicotinate and ethyl 8-quinolinecarboxylate, undergo the mixed ester condensation in good yields. The internal condensation of ethyl adipate to give 2-carbethoxycyclopentanone (Dieckmann reaction) is an example of cyclization (81%). ... 

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