Stobbe condensation

The Stobbe condensation , also known as the succinic ester condensation , is a name reaction in organic chemistry . Hans Stobbe discovered this synthesis in 1893. It is a special case of the condensation of esters with aldehydes or ketones in the presence of a strong base .

Overview reaction

In the Stobbe condensation disuccinate or her are derivatives in a primary aldol condensation about the α - carbon - atom as nucleophilic center to the carbonyl group bound the aldehyde or ketone.

The radicals R ¹ and R ² can be aliphatic or aromatic . In addition, the reaction takes place with α, β- unsaturated aldehydes or ketones, diketones and cyanoketones . The radicals R ³ and R ⁴ can be aryl , allyl or alkylidene groups .

A special feature of this reaction is that sterically hindered ketones can also react.

mechanism

The reaction mechanism of the Stobbe condensation could be as follows. In the following example, the simplest aldehyde, formaldehyde , is selected as the reactant and an aliphatically substituted succinic acid ester:

First the succinic acid diethyl ester (1) is deprotonated by the base, a carbanion 2 is formed . This adds nucleophilically to the carbonyl component 3 . The resulting oxygen - anion then nucleophile to attack the adjacent carbon atom. A cyclic molecule 4 is formed . Ethanolation is then split off and the lactone ring is opened 5 . The ring opening is based on base catalysis. The intermediate product is then protonated and the α, β-unsaturated ester 6 is formed .

application

Condensation is used to replace the carbonyl group of aromatic ketones with a propionic acid residue . In addition, this condensation in combination with the Friedel-Crafts reaction can be used to produce naphthols , indones and tetralones . It can also be synthesized γ-keto acids. In addition, the almost irreversible ring opening achieves high yields. In addition, the carbon chain can be lengthened by three carbon atoms at the same time, compared to the Knoevenagel reaction in which only two carbon atoms are added.

literature

• Hans Stobbe: A new synthesis of unsaturated dibasic acids from ketones and succinic acid esters . Habilitation thesis. Printed by Oswald Schmidt, Leipzig 1894, OCLC 41600033 .

Individual evidence

1. ↑ HA Stobbe: A new synthesis of teraconic acid . In: Reports of the German Chemical Society . tape 26 . Weinheim 1883, p. 2312-2319 .
2. ^ ^{A b c d} W. Uhl, A. Kyritsoulis: Name and catchword reactions in organic chemistry . Friedr. Vieweg & Sohn Verlag, Braunschweig 1984, ISBN 3-528-03581-1 , p. 143-144 .
3. ↑ Louis F. Fieser, Mary Fieser: Textbook of organic chemistry . Chemie, Weinheim 1957, p. 805 .