Dieckmann condensation

The Dieckmann condensation is a name reaction in organic chemistry and named after the German chemist Walter Dieckmann ( 1869-1925 ). Under this reaction is understood in chemistry an intramolecular Claisen condensation of dicarboxylic acid esters to cyclic β -keto esters.

Reaction mechanism

The mechanism is of the Claisen condensation are identical, however, a complete sequence of the reaction is carried out with a stoichiometric amount of base present in the form of alcoholates, sodium amide, or alkali metal hydrides. This causes a deprotonation of the dicarboxylic acid ester 1 The next step is a nucleophilic attack on the carbonyl carbon takes place. It it comes to the elimination of an alkoxide 4 and the β -keto ester 5 The resulting β -keto ester is then deprotonated by another alkoxide in α - position to two carbonyl groups. The deprotonation has a high driving force and is virtually irreversible. The equilibrium to the side of the desired product can be moved. The reaction is completed, it sets the recognition acid in order to neutralize the anion, alcoholate, all also be protonated, and a reverse reaction is excluded. The products of a Dieckmann condensation are five -to eight- membered cyclic β -keto esters. Under certain conditions even zwölfatomige and larger rings can be synthesized.