Crespi Ayelén F, Barrionuevo Emiliano, Jasinski Gabriel, Moglioni Albertina G, Vega Daniel, Lázaro-Martínez Juan M
Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Department of Chemistry, Ciudad Autónoma de Buenos Aires, 1113, Argentina.
CONICET - Universidad de Buenos Aires, Instituto de Química y Metabolismo del Fármaco (IQUIMEFA-UBA-CONICET), Ciudad Autónoma de Buenos Aires, 1113, Argentina.
ChemistryOpen. 2025 Aug;14(8):e202400411. doi: 10.1002/open.202400411. Epub 2025 Jan 5.
Gem-diols are defined as organic molecules carrying two hydroxyl groups at the same carbon atom, which is the result of the nucleophilic addition of water to a carbonyl group. In this work, the generation of the hydrated or hemiacetal forms using pyridine- and imidazole-carboxaldehyde isomers in different chemical environments was studied by Nuclear Magnetic Resonance (NMR) recorded in different media and combined with theoretical calculations. The change in the position of aldehyde group in either the pyridine or the imidazole ring had a clear effect in the course of the hydration/hemiacetal generation reaction, which was favored in protic solvents mainly in the presence of methanol. For pyridinecarboxaldehydes, the acidity/basicity degree of the reaction medium influenced not only the generation of the gem-diol or hemiacetal forms but also the oxidation to the corresponding carboxylic acid. However, imidazolecarboxaldehyde was found to be less reactive to the nucleophilic addition of water and methanol than the other compounds in all the environments evaluated. Furthermore, both the gem-diol/hemiacetal generation and the Cannizzaro reaction products were studied in alkaline medium.
偕二醇被定义为在同一碳原子上带有两个羟基的有机分子，这是水对羰基进行亲核加成的结果。在这项工作中，通过在不同介质中记录的核磁共振（NMR）并结合理论计算，研究了在不同化学环境中使用吡啶和咪唑甲醛异构体生成水合形式或半缩醛形式的情况。吡啶环或咪唑环中醛基位置的变化在水合/半缩醛生成反应过程中具有明显影响，该反应在质子溶剂中，主要是在甲醇存在的情况下更易发生。对于吡啶甲醛，反应介质的酸碱度不仅影响偕二醇或半缩醛形式的生成，还影响其氧化为相应的羧酸。然而，在所有评估的环境中，发现咪唑甲醛对水和甲醇的亲核加成反应性低于其他化合物。此外，还研究了在碱性介质中偕二醇/半缩醛的生成以及坎尼扎罗反应产物。
