Synthesis of an electron-rich aniline-containing dye and its dyeing behaviors on silk through a three-component Mannich-type reaction

Under the guidance of the finding that the tyrosine residues in proteins could undergo three-component Mannich-type reactions with formaldehyde and electron-rich aniline-containing compounds, which forms covalent bonding connections between the protein of interest and the aniline with high levels of selectivity under relatively mild conditions, an orange aromatic primary amine-containing acid dye AMODB was designed and readily synthesized. The molecular structure was characterized by FTIR, 1H NMR, mass spectrometry and elemental analysis. The synthesized dye and a similar control dye (C.I. Acid Yellow 11) without primary amine groups were applied to dye silk fabric by three dyeing processes: Mannich-type dyeing (with and without the addition of formaldehyde) and acidic dyeing. Their washing and rubbing fastness properties with different dyeing methods were examined and compared. It was found that the dyed silk fabric with AMODB by the Mannich-type dyeing showed higher color depth, better anti-stripping ability to DMF and better washing fastness than those of the dyed silk fabric with C.I. Acid Yellow 11 by acidic dyeing due to the covalent bond formation between the dye chromophore of AMODB and silk fiber. In addition, mild Mannich dyeing conditions suitable for silk (AMODB at 3% owf, 75:1 liquor-to-goods ratio, dyebath pH 5.5, 30 °C, 10 h) were provided.

Graphical abstractIt is proven that the tyrosine residues in silk fiber undergoes three-component Mannich-type reactions with formaldehyde and an orange electron-rich aniline-containing dye AMODB, which forms covalent bonding connections between the silk fiber and the dye under relatively mild conditions (pH 5.5, 30 °C, 10 h). The Mannich dyeing method can be developed into a new energy-efficient, environmentally friendly and reactive dyeing method suitable for silk, which might have much wider application prospects over the traditional reactive dyes.Figure optionsDownload full-size imageDownload as PowerPoint slide