Laboratório Associado para a Química Verde-REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto, Portugal.
Molecules. 2022 Oct 29;27(21):7351. doi: 10.3390/molecules27217351.
This work reports the functionalization of pyranoflavyliums pigment using 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride coupling chemistry. Four cinnamic acids were used to establish an ester bond with the hydroxyl group of the pyranoflavylium, namely 4-dimethylamino-, 4-amino-, 4-bromo-, and trans-cinnamic acids. The experimental condition, namely the molar ratios, solvent, and reaction time, were adjusted to obtain higher reaction yields in a reduced period. Excellent reaction yields of 68%, 85%, 94%, and 99% were achieved for 4-amino, trans-, 4-bromo, and 4-dimethylamino pyranoflavylium cinnamates, respectively. The structure of the functionalized pigments was fully clarified using one-dimensional (1H) and two-dimensional (COSY, HSQC, and HMBC) NMR experiments and HRSM analysis. Regardless of the type of functionalization, the UV-Visible spectrum showed a bathochromic shift (red region) on the maximum absorption wavelength and the absence of acid-base reactions throughout a broad pH range in comparison to the pyranoflavylium precursor. This work offers a valuable environmentally friendly, quick, and straightforward alternative to flavylium compounds' challenging and labor-intensive functionalization, resulting in novel dyes with higher stability and dissimilar chromatic features.
这项工作报道了使用 1-(3-二甲基氨基丙基)-3-乙基碳二亚胺盐酸盐偶联化学对吡喃并黄酮醇颜料进行功能化。使用了四种肉桂酸与吡喃并黄酮醇的羟基建立酯键，即 4-二甲氨基、4-氨基、4-溴和反式肉桂酸。调整了实验条件，即摩尔比、溶剂和反应时间，以在更短的时间内获得更高的反应产率。4-氨基、反式、4-溴和 4-二甲氨基肉桂酸吡喃并黄酮醇酯的反应产率分别达到了 68%、85%、94%和 99%。使用一维（1H）和二维（COSY、HSQC 和 HMBC）NMR 实验和高分辨率质谱分析（HRSM）充分阐明了功能化颜料的结构。无论功能化类型如何，与吡喃并黄酮醇前体相比，紫外可见光谱在最大吸收波长处表现出明显的红移（红色区域），并且在很宽的 pH 范围内没有酸碱反应。这项工作为黄酮醇化合物具有挑战性和劳动密集型的功能化提供了一种有价值的环保、快速和直接的替代方法，得到了具有更高稳定性和不同颜色特征的新型染料。
