Pigment Yellow 151 synthesis

Yield:31837-42-0 89%

Reaction Conditions:

Stage #1: anthranilic acidwith hydrogenchloride in water;
Stage #2: with sodium nitrite in water at 0; for 0.5 h;
Stage #3: 5-Acetoacetyl-amino-benzimidazol-2-onewith acetic acid;sodium hydroxide in water at 20; for 6 h;Product distribution / selectivity;

Steps:

3

This Comparative Example follows the conventional method described in German Patent No. 3140141. 2.0 g (0.0146 mol) of Anthranilic acid, 35 mL of deionized water, and 8.5 mL of 5 M hydrochloric acid are mixed with magnetic stirring while stirring in a 3-neck round bottom flask equipped with a thermometer. The clear solution is cooled to below 0°C before adding dropwise a solution of 1.058 g NaNO₂ (0.0153 mol) dissolved in 6 mL deionized water (about 2.5M NaNO₂) at a rate that maintains an internal temperature below 0°C. The diazo solution is kept stirring cold for at least 30 min. A second solution is prepared by mixing 3.47 g (0.0149 mol) of 5-acetoacetylamino-benzimidazolone (TCI America), with a basic solution containing 1.715 g (0.0429 mol) of NaOH dissolved in 10 mL deionized water. This second solution is then added to a third mixture containing 195 mL deionized water, 6 mL of glacial acetic acid (0.105 mol), and sodium hydroxide (2.29 g, 0.0573 mol), resulting in a finely suspended colloidal solution of white coupling component. The cold diazo solution is then added dropwise at room temperature to a vigorously stirred suspension of the coupling component, producing a yellow pigment slurry. The yellow mixture is stirred for at least 6 hours to complete the color development, after which time the slurry is filtered under vacuum through Versapor 0.8 μm filter membrane (PALL Corp.). The pigment wetcake is reslurried into 200 mL deionized water and then is vacuum filtered twice more, after which time the pigment wetcake is freeze-dried for 48 hours. The final product is a dark yellow powder (4.96 g, 89% yield), and after analysis by TEM imaging, consists of large aggregates and agglomerates of elongated rod-shaped particles having average lengths ranging from about 200 to about 500 nm.

References:

EP2290012,2011,A2 Location in patent:Page/Page column 122