Bottin Marco, Di Carmine Graziano, Bortolini Olga, De Risi Carmela, Bertoldo Monica, Cataldi Tommaso R I, Calvano Cosima D, Massi Alessandro, Ragno Daniele
Department of Chemical, Pharmaceutical and Agricultural Sciences, University of Ferrara, Via L. Borsari, 46, 44121, Ferrara, Italy.
Department of Environmental and Prevention Sciences, University of Ferrara, Via L. Borsari, 46, 44121, Ferrara, Italy.
Chemistry. 2023 Aug 4;29(44):e202301416. doi: 10.1002/chem.202301416. Epub 2023 Jul 6.
The application of N-heterocyclic carbene (NHC) catalysis under highly diluted oxidative condition to the polycondensation of dialdehydes and diols is herein presented as an alternative, atom-economical synthetic route to macrocyclic oligoesters (MCOs). The disclosed protocol paves the way to the straightforward access to MCOs, starting from commercial dialdehydes, avoiding the use of toxic diacyl chlorides, commonly employed in traditional MCOs synthetic processes. The method is totally metal-free, takes place in the green Me-THF solvent and requires the use of a fully recyclable quinone oxidant. The protocol versatility is confirmed by the employment of fossil-based and bio-based monomers such as 2,5-diformylfuran (DFF), 2,5-bis(hydroxymethyl)furan (BHMF), and isomannide, synthesizing a series of novel and known synthetically relevant macrocyclic oligoesters, fully characterized by NMR and MALDI-TOF MS analysis, with product yields (51-86 %) comparable to those obtained by traditional synthetic routes. Finally, to emphasize the synthetic relevance of the target macrocycles, an entropically-driven ring opening polymerization (ED-ROP) key study has been performed, optimizing the organocatalyzed synthesis of poly(2,5-furan-dimethylene 2,5 furandicarboxylate) (PBHMF) with number-average molecular weight up to 8200 g mol and 66 % isolated yield.
本文介绍了在高稀释氧化条件下将N-杂环卡宾（NHC）催化应用于二醛和二醇的缩聚反应，作为一种合成大环低聚酯（MCOs）的替代且原子经济的合成路线。所公开的方案为直接获得MCOs铺平了道路，从市售二醛开始，避免了传统MCOs合成过程中常用的有毒二酰氯的使用。该方法完全无金属，在绿色的甲基四氢呋喃溶剂中进行，并且需要使用完全可回收的醌类氧化剂。通过使用基于化石和生物基的单体，如2,5-二糠醛（DFF）、2,5-双（羟甲基）呋喃（BHMF）和异甘露糖醇，证实了该方案的通用性，合成了一系列新型且已知的具有合成相关性的大环低聚酯，通过NMR和MALDI-TOF MS分析对其进行了全面表征，产物收率（51-86%）与传统合成路线获得的收率相当。最后，为了强调目标大环化合物的合成相关性，进行了一项熵驱动的开环聚合（ED-ROP）关键研究，优化了有机催化合成数均分子量高达8200 g/mol且分离收率为66%的聚（2,5-呋喃二甲撑2,5-呋喃二甲酸酯）（PBHMF）的过程。
