Sulfuric Acid → 8-nitro-4-oxo-4H-chromene-2-carboxylic acid

Participants

Reaction Steps

After a reaction container equipped with a stirrer, a cooling tube and a thermometer was charged with 20 parts by weight of fuming sulfuric acid, 2 parts by weight of a mixture (content: 65.7% by weight) containing 2-(2-nitrophenoxy)fumaric acid and 2-(2-nitrophenoxy)maleic acid was added. After that, the mixture was stirred and kept at an inner temperature of 25° C. for 2 hours and then at an inner temperature of 50° C. for 2 hours to obtain a reaction solution containing 8-nitro-2-carboxy-4-oxo-4H-1-benzopyran (reaction yield: 35%). After cooled to room temperature, the reaction solution was gradually added into 40 parts by weight of water and the mixture was gradually cooled to an inner temperature of 0° C. Precipitated crystals were filtered and dried to obtain 0.28 parts by weight of 8-nitro-2-carboxy-4-oxo-4H-1-benzopyran as crystals (content: 95.2% by weight, yield: 20%).

Provenance & Evidence