Iodine → 1,3-Dihydro-7,8-dimethyl-2H-imidazo(4,5-b)quinolin-2-one

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Reaction Steps

5-[(2,3-Dimethyl-6-nitrophenyl)methylene]-2,4-imidazolidinedione (19.95 g, 76 mmol) in dimethylformamide (350 mL) was hydrogenated over 10% palladium on charcoal (3 g) at 60 p.s.i. in a Parr hydrogenation apparatus. After hydrogen uptake ceased, the mixture was filtered through kieselgehr and the solvent evaporated to leave a solid which was suspended in a refluxing methanol (1 L). Iodine (19.4 g, 76 mmol) was added portionwise over 5 minutes and the mixture refluxed for 15 minutes before being concentrated in vacuo to about 100 mL. A solution of sodium thiosulfate (21 g) and sodium carbonate (11 g) in water (300 mL) was added with vigorous stirring to afford a beige precipitate which was collected, washed with water and dried in air to give 15.7 g. This was combined with crude material from experiments performed on 40 g and 4.16 g of starting material, suspended in hot (80° C.) water, filtered, suspended in refluxing methanol and filtered. Crystallization from dimethylacetamide afforded 1,3-dihydro-7,8-dimethyl-2H-imidazo[4,5-b]quinolin-2-one (53.4 g, 65%), m.p. >300° C.

Provenance & Evidence