Abstract

Amphoteric aminophenol compounds have diverse synthetic and industrial use due to their multi-functional chemical reactivity. In this study, the synthesis of amphoteric flavonoid compounds via chemical modification with sub- and supercritical ammonia was explored. Both product formation and degree of amination of both catechin and condensed tannins were dependent on the processing conditions employed. Applying subcritical ammonia conditions produced ammonium ion formation and polymerization of these flavonoids. Under these conditions, ammonium group hydrogen-bonding was determined at the flavonoid B-ring catechol group and characterized by the δNH₄ ⁺ bending at 1400 cm⁻¹ in FTIR spectra. In contrast, using supercritical ammonia conditions (150 °C, 115 bar) led to formation of the desired amine-substituted products. Characterization of the aminated catechin and tannin products confirmed hydroxyls of the flavanyl A-ring were substituted to –NH₂. FTIR established C-NH₂ bond formation (1550, 1250 cm⁻¹) with %N and NMR indicating stoichiometric substitutions of hydroxyl groups at the C5 and C7 flavonoid A-ring positions. Moreover, under supercritical ammonia conditions, there was a reduced tendency for the undesired base-catalysed autocondensation observed at lower temperatures and pressures.

摘要

两性氨基酚化合物由于其多功能的化学反应性而具有多种合成和工业用途。在这项研究中，探索了通过亚临界和超临界氨的化学修饰合成两性类黄酮化合物的方法。儿茶素和缩合单宁的产物形成和氨基化程度均取决于所采用的加工条件。在亚临界氨条件下产生铵离子形成和这些类黄酮的聚合。在这些条件下，铵基团的氢键在所述类黄酮B-环儿茶酚组确定，并且特征在于δNH ₄ ⁺弯曲在1400厘米^-1在FTIR光谱中。相反，使用超临界氨条件（150°C，115 bar）导致形成所需的胺取代产物。胺化儿茶素和单宁产物的表征证实了黄烷酰基A环的羟基被–NH ₂取代。FTIR建立了具有％N和NMR的C-NH ₂键形成（1550、1250 cm ^-1），表明在C5和C7类黄酮A环位置处羟基的化学计量取代。此外，在超临界氨条件下，在较低的温度和压力下观察到的不希望的碱催化的自缩合趋势降低了。