Reaction contest: hydrolysis versus intramolecular cyclisation reaction in alkyl squaramate esters†

IF 3.9 3区化学 Q2 CHEMISTRY, MULTIDISCIPLINARY

RSC Advances Pub Date : 2024-10-11 DOI:10.1039/D4RA04362F

Marta Ximenis, Santiago Cañellas, Rosa M. Gomila, Bartomeu Galmés, Antonio Frontera, Antonio Costa and Carmen Rotger

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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.

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反应竞赛：角戊酸烷基酯中的水解反应与分子内环化反应†。

我们研究了角柑酸酯在水溶液中的稳定性和水解行为。角柑酸酯的结构和邻接基团的性质对其水溶性稳定性和对亲核物的反应性有很大影响。缺乏或含有弱碱性邻位基团参与（NGP）取代的夸美特酯在 pH 值为 9 时仍保持稳定，其水解速率（kOH ≈ 10-1 M-1 s-1）比角酰胺酯快 1000 倍，并遵循二阶速率定律。被碱性 NGP 基团（如胺）官能化的角鯊烷酸酯的水解速率与 pH 值有关，这是因为末端氨基具有锚定辅助作用，从而降低了其在 pH 值为 5 时的稳定性。

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来源期刊

RSC Advances chemical sciences-

CiteScore

7.50

自引率

2.60%

发文量

3116

审稿时长

1.6 months

期刊介绍： An international, peer-reviewed journal covering all of the chemical sciences, including multidisciplinary and emerging areas. RSC Advances is a gold open access journal allowing researchers free access to research articles, and offering an affordable open access publishing option for authors around the world.