What drives Dieckmann condensation?
The mechanism of the Dieckmann condensation is the same as a Claisen condensation. An alkoxide base removes an alpha-hydrogen from one of the esters to form an ester enolate. The enolate then adds to the carbonyl carbon of the other ester to form a tetrahedral alkoxide intermediate.
What is the Dieckmann condensation reaction for the preparation of Cycloalkanes?
The Dieckmann condensation is the intramolecular chemical reaction of diesters with base to give β-keto esters. It is named after the German chemist Walter Dieckmann (1869–1925). The equivalent intermolecular reaction is the Claisen condensation.
What is Dieckmann condensation give the equation taking an example?
The Dieckmann condensation is an organic reaction which is used to form a carbon-carbon bond between two tethered ester groups using an alkoxide base in alcohol. The resulting product is a cyclic β-ketoester. This reaction is an intermolecular form of Claisen condensation [1-3].
What base is used in Claisen condensation?
The base of choice in Claisen condensation is the alkoxide ion corresponding to the alkoxy group in the ester.
What is the driving force for product formation in the Dieckmann condensation?
The product is a cyclic β-keto ester which has a very acidic alpha hydrogen. And it is this proton that makes any Claisen reaction possible since it is removed in an irreversible acid-base reaction which is the driving force that shifts the equilibrium in favor of the condensation.
What is Dieckmann ring closure?
The Dieckmann condensation is a base-promoted intramolecular condensation of α,ω-diesters to form cyclic β-ketoesters that can be further transformed into cyclic ketone upon hydrolysis and decarboxylation. Occasionally, this reaction is also known as Dieckmann ring closure.
What is Stobbe condensation?
Stobbe condensation involves reaction of aldehyde or ketone with succinic ester in the presence of basic catalyst like sodium hydroxide or potassium tertiary butoxide to form alkylidene succinic acid. • This reaction limited to α – ω diester ester group at 1st carbon and last carbon.
What is crossed Claisen condensation?
A “crossed” Claisen condensation involves the enolate of one ester reacting as a nucleophile with a different (ideally non-enolizable) ester to give a beta-keto ester. When the enolate and ester are on the same molecule, a Claisen condensation will form a ring.
How many equivalents of ethoxide base are used in the Claisen condensation?
one full equivalent
22.52c. Thus, ethoxide is a reactant rather than a catalyst in the overall reaction, and for this reason one full equivalent of ethoxide must be used in the Claisen condensation.