Aniline → Picolinic acid

Participants

Reaction Steps

1 mole of the benzoyl-pyridine-carboxylic acid (II) or the (heterocyclic-carbonyl)-pyridine-carboxylic acid (IV) and about 0.9 to 1.5 moles, preferably 1.0 to 1.2 moles of the heterocyclic compound (III) or the aniline compound (V) are added to about 3 to 30 moles of concentrated sulfuric acid, acetic anhydride or polyphosphoric acid, and the resulting mixture is allowed to react at a temperature of about 30° to 130° C for a period of from about 2 to 10 hours. The reaction product is then poured into 1 to 5 liters of ice-water to hydrolyze or dilute the condensing agent, and the resulting aqueous solution was made weakly acidic or neutral with dilute aqueous sodium hydroxide. Benzene or toluene is added thereto followed by stirring to transfer any unreacted heterocyclic compound or aniline compound to the benzene or toluene layer, which is then removed by separation. The residual aqueous layer is adjusted to a pH of about 11 to 12 with dilute aqueous sodium hydroxide and the precipitated solid is filtered, washed successively with water and a small amount of ethanol and dried to obtain in good yield a lactone color former of the pyridine-carboxylic acid represented by the formula (I) as substantially colorless of slightly colored crystals. Alternatively, the residual aqueous layer as obtained above, after removal of the benzene or toluene layer, is adjusted to a pH of 11 to 12 with dilute aqueous sodium hydroxide, and benzene or toluene is added to the resulting aqueous solution followed by stirring to transfer the lactone color former of pyridine-carboxylic acid to the benzene or toluene layer, which was then recovered by separation. Benzene or toluene was distilled off from the benzene or toluene layer. The residue was washed successively with water, a small amount of ethanol, benzene, lizroin or petroleum ether and dried. Further alternatively, the above reaction product is poured into 1 to 5 liters of ice-water to hydrohyze or dilute the condensing agent, and the resulting aqueous solution was adjusted to a pH of 11 to 12 with dilute aqueous sodium hydroxide. Benzene or toluene is added thereto followed by stirring to transfer the lactone color former of pyridine-carboxylic acid into the benzene or toluene layer which is then recovered by separation. The benzene or toluene layer is worked up in the same manner as described above. Thus, a substantially colorless or slightly colored lactone color former of pyridine-carboxylic acid represented by the formula [I] can be obtained in high yield. If necessary, the lactone color former of pyridine-carboxylic acid thus obtained can be recrystallized. The present invention, will now be illustrated by reference to the following Examples, but they are not to be construed as limiting the present invention.

Provenance & Evidence