Utente:Grasso Luigi/sanbox1/Steglich
The Steglich esterification is a variation of an esterfication with dicyclohexylcarbodiimide as a coupling reagent and 4-dimethylaminopyridine as a catalyst. The reaction was first described by Wolfgang Steglich in 1978.[1] It is an adaptation of an older method for the formation of amides by means of DCC (dicyclohexylcarbodiimide) and 1-hydroxybenzotriazole (HOBT).[2][3]
Steglich overview
This reaction generally takes place at room temperature. A suitable solvent is dichloromethane. Because the reaction is mild, esters can be obtained that are inaccessible through other methods for instance esters of the sensitive 2,4-dihydroxybenzoic acid. A characteristic is the formal uptake of water generated in the reaction by DCC, forming the urea compound dicyclohexylurea (DCU).
Meccanismo di reazione[modifica | modifica wikitesto]
The reaction mechanism is described as follows:
With amines, the reaction proceeds without problems to the corresponding amides because amines are more nucleophilic. If the esterification is slow, a side-reaction occurs, diminishing the final yield or complicating purification of the product. This side-reaction is a 1,3-rearrangement of the O-acyl intermediate to an N-acylurea which is unable to further react with the alcohol. DMAP suppresses this side reaction, acting as an acyl transfer-reagent in the following manner:
Note[modifica | modifica wikitesto]
- ^ B. Neises, W. Steglich, Simple Method for the Esterification of Carboxylic Acids, in Angew. Chem. Int. Ed., vol. 17, n. 7, 1978, pp. 522–524, DOI:10.1002/anie.197805221.
- ^ J. C. Sheehan, G. P. Hess, A New Method of Forming Peptide Bonds, in J. Am. Chem. Soc., vol. 77, n. 4, 1955, pp. 1067–1068, DOI:10.1021/ja01609a099.
- ^ W. König, R. Geiger, Eine neue Methode zur Synthese von Peptiden: Aktivierung der Carboxylgruppe mit Dicyclohexylcarbodiimid unter Zusatz von 1-Hydroxy-benzotriazolen, in Chem. Ber., vol. 103, n. 3, 1970, pp. 788–798, DOI:10.1002/cber.19701030319.
Bibliografia[modifica | modifica wikitesto]
- J. Otera: Esterification. 1. Auflage, Wiley-VCH, Weinheim, 2003, ISBN 3-527-30490-8
