Indoline Catalyzed Acylhydrazone/Oxime Condensation under Neutral Aqueous Conditions was written by Zhou, Yuntao;Piergentili, Irene;Hong, Jennifer;van der Helm, Michelle P.;Macchione, Mariano;Li, Yao;Eelkema, Rienk;Luo, Sanzhong. And the article was included in Organic Letters in 2020.Reference of 111-77-3 This article mentions the following:
Acylhydrazone formation has been widely applied in materials science and biolabeling. However, their sluggish condensation rate under neutral conditions limits its application. Herein, indolines with electron-donating groups are reported as a new catalyst scaffold, which can catalyze acylhydrazone, hydrazone, and oxime formation via an iminium ion intermediate. This new type of catalyst showed up to 15-fold rate enhancement over the traditional aniline-catalyzed reaction at neutral conditions. The identified indoline catalyst was successfully applied in hydrogel formation. In the experiment, the researchers used many compounds, for example, 2-(2-Methoxyethoxy)ethanol (cas: 111-77-3Reference of 111-77-3).
2-(2-Methoxyethoxy)ethanol (cas: 111-77-3) belongs to ethers. Of all the functional groups, ethers are the least reactive ones. Ether bonds are quite stable towards bases, oxidizing agents and reducing agents. But on the other hand, ethers undergo cleavage by reaction with acids. The unique properties of ethers (i.e., that they are strongly polar, with nonbonding electron pairs but no hydroxyl group) enhance the formation and use of many reagents. For example, Grignard reagents cannot form unless an ether is present to share its lone pair of electrons with the magnesium atom. Complexation of the magnesium atom stabilizes the Grignard reagent and helps to keep it in solution.Reference of 111-77-3
Referemce:
Ether – Wikipedia,
Ether | (C2H5)2O – PubChem