Picolinic acid → 2-(Pyridin-2-yl)-1,3-benzothiazol-5-amine

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Reaction Conditions

Reaction Steps

PPA (500 g) is added to picolinic acid (24.6 g, 0.2 mol) and sodium 2-amino-4-nitrothiophenoxide (47 g, 0.2 mol). The mixture is heated at 120-130° C. for 6 hours. The resulting mixture is cooled and NaOH is added dropwise (pH=10). The product is filtered off and washed with water. The 2-(2-pyridyl)-5-nitrobenzothiazole is recrystallized from 9/1 isopropyl ether/methanol and is added to a solution of tin dichloride (61.6 g, 0.273 mol) in conc. HCl (50 ml) at 0° C. This mixture is heated at 95° C. for 120 minutes. It is cooled and NaOH is added dropwise (pH=10). The resulting mixture is extracted with chloroform and the combined organic phases are extracted with 0.5M HCl. The acidic aqueous phases are combined, basified with NaOH (pH=10) and extracted with ethyl acetate. The extracts are washed with water and evaporated. The solid obtained is recrystallized from isopropyl ether. Yield: 3.6 g; Rf (9/1 chloroform/methanol): 0.45; IR (KBr): 3400, 3325, 3215, 1590, 1430, 1320, 780 cm−1.

Provenance & Evidence