Isatin → Acridine

Temperature

50 °C

Isatin (1) (1.88 g) was slowly added to a solution of potassium hydroxide (5.07 g, 0.09 mole) dissolved in water (3.5 ml). The reaction flask was heated to about 50° C. in an oil bath. About 10 ml more water was added dropwise. Resorcinal (2) (10 g, 0.089 mole) was added and the temperature was raised to 100° C. as stirring was continued, resulting in the formation of a molten mixture. More isatin (1) (1.88 g) was added. The reaction flask (3-necked round bottom) was attached to a nitrogen inlet and the water vapors were flushed out by the stream of nitrogen. The mixture was stirred for 4 hours at 125° C. Water (70 ml) was added and the contents were dissolved by continued stirring. After transferring the mixture to an erlenmeyer flask the volume was brought up to 200 ml with water. The pH was adjusted to 2.0 with concentrated hydrochloric acid. Filtration and washing of the solids with water gave the crude acridine acid. It was then dissolved in 2N NaOH (100 ml) and the solution was filtered through celite. The celite bed was washed with 200 ml of 1N NaOH. The filtrate was acidified with concentrated HCl to pH 2.0. The precipitate of 2-hydroxy-acridine-9-carboxylic acid (3) was filtered, washed with water and was dried in vacuum over P2O5 (yield=42%).

1. temperaturethe temperature was raised to 100° C.
2. customresulting in the formation of a molten mixture
3. customThe reaction flask (3-necked round bottom) was attached to a nitrogen inlet
4. customthe water vapors were flushed out by the stream of nitrogen
5. stirringThe mixture was stirred for 4 hours at 125° C
6. additionWater (70 ml) was added
7. dissolutionthe contents were dissolved by continued stirring
8. filtrationFiltration
9. washwashing of the solids with water

ORD record

ord-c7130a89d5a74842b541b7e749b5713b

Source dataset

uspto-grants-1994_02

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US05284951