Related Experiment Video
Updated: Jun 10, 2025

Facile Preparation of 2Z,4E-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate
Published on: June 21, 2017
Reaction contest: hydrolysis versus intramolecular cyclisation reaction in alkyl squaramate esters
Marta Ximenis1, Santiago Cañellas1, Rosa M Gomila1
1Universitat de les Illes Balears Cra. Valldemossa Km 7.5 Palma de Mallorca 07122 Spain carmen.rotger@uib.es.
Abstract:
The stability and hydrolytic behavior of squaramate esters in aqueous solutions have been investigated. The structure of squaramates and the nature of adjacent groups significantly influence their aqueous stability and reactivity towards nucleophiles. Squaramate esters, lacking or containing weakly basic neighboring group participation (NGP) substitutions, remain stable up to pH 9. Their hydrolysis rate (k OH ≈ 10-1 M-1 s-1) is 1000 times faster than that of squaramides, following a second-order rate law. Squaramate esters functionalized with basic NGP groups, such as amines, display a pH-dependent hydrolysis rate due to anchimeric assistance of the terminal amino group, reducing stability to pH 5. However, when the squaramate ester has a terminal nucleophilic group in the γ position of the alkyl chain, it undergoes rapid intramolecular cyclization, forming cyclic squaramides.
Related Concept Videos
Esters to Carboxylic Acids: Acid-Catalyzed Hydrolysis
During hydrolysis, the ester is first activated towards nucleophilic attack through the protonation of the carboxyl oxygen atom by the acid catalyst. The protonation makes the ester carbonyl carbon more electrophilic. In the next step, water acts as a nucleophile and adds to the...
Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration
Radical Reactivity: Intramolecular vs Intermolecular
Esters to Carboxylic Acids: Saponification
The reaction requires a base in stoichiometric amounts, which participates in the reaction and is not regenerated later. So, the base acts as a...
Alkylation of β-Diester Enolates: Malonic Ester Synthesis
Intramolecular Claisen Condensation of Dicarboxylic Esters: Dieckmann Cyclization

