Study On Synthesis Of Flavonoid Biomimetic Chromophore And Pyrazolone Azo Chromophore And Their Crosslinking Dyes

Flavonoid natural dyes are an important class of natural colorants, but they have some drawbacks such as lower substantivity to fiber and relatively small molar extinction coefficient; pyrazolone azo dyes have been widely applied for a long time, however, their fixation on fiber is still not perfect. In this paper, the basic chromophores of flavonoid and pyrazolone dyes were chosen and subjected to be modified, then polyamino crosslinking groups were introduced into the prepared intermediates to afford crosslinking dyes. A nearly 100 percent of fixation is expected via crosslinking dyeing to achieve the goal of perfecting their application performance in every aspects.Four chlorosulfonyl-containing pyrazolone azo compounds were synthesized by the reactions of the corresponding sodium sulfonate of acid dye and thionyl chloride in the presence of a catalytic quantity of DMF. Their structures were confirmed by IR, 1H NMR and MS spectroscopy, and the results revealed that the obtained sulfonyl chlorides exist in stable hydrazone form.Reaction of 2',4'-dihydroxy-5'-nitroacetophenone and 2.0 equivalents of (substituted)benzoyl chlorides in acetone in the presence of anhydrous potassium carbonate directly afforded the corresponding 3-aroyl-7-hydroxy-6-nitroflavone.3-Benzoyl-7-hydroxy-6-nitroflavone was cleaved in 5% ethanolic potassium hydroxide to give l-(2,4-dihydroxy-5-nitrophenyl)-3-phenyl-l,3-propanedione. The formed 1,3-diketone derivative was then transformed by acid catalyzed cyclization into 7-hydroxy-6-nitroflavone, which was followed by reduction to afford 6-amino-7-hydroxyflavone. Thus a novel approach was provided for the synthesis of 6-amino-7-hydroxyflavone.Treatment of 1,3-diketones containing benzoyloxy group in 1% aqueous sodium hydroxide can afford directly the corresponding ring-A hydroxylated flavone. The results showed that the hydrolysis of ester group and the cyclization of 1,3-diketone were carried out in one step.Four pyrazolone series crosslinking dyes (D1~D4) containing tetraethylenepentaamine moiety and two crosslinking polymeric dyes (D5 and D6) were synthesized from the prepared chlorosulfonyl-containing pyrazolone azo compounds. Dyeing performance of D1, D3, D5 and D6 on silk and cotton were investigated. The results demonstrate that the fixation of D1 and D3 on silk and cotton are all greater than 97.5%, and the fixation of D5 and D6 on silk are all greater than 99%, their fixation on cotton is 96.6% and 98.6% respectively.Crosslinking polymeric dye D11 containing flavone moiety was synthesized and its dyeing performance on silk and cotton was studied. Its fixation on silk and cotton is 99.4% and 98.8% respectively.