Sulfuric Acid → 1,3-Dihydro-1-oxoisobenzofuran-5-carboxylic acid

反応式

S(=O)(=O)(O)O.[C:6]([OH:17])(=[O:16])[C:7]1[CH:15]=[CH:14][C:10]([C:11]([OH:13])=[O:12])=[CH:9][CH:8]=1.O1COCO[CH2:19]1>CC(OCC1C2C(=CC=CC=2)C(COC(C)=O)=C2C=1C=CC=C2)=O>[C:11]([C:10]1[CH:14]=[C:15]2[C:7](=[CH:8][CH:9]=1)[C:6](=[O:17])[O:16][CH2:19]2)([OH:13])=[O:12]

参加物

実験手順

To 153 ml of fuming sulfuric acid, containing about 27% of SO3, 50 g (0.3 m) of terephthalic acid are added, under stirring, at room temperature, then 23 g (0.25 m) of 1,3,5-trioxane are added thereinto in two portions, by cooling to a temperature of 15-18° C. after any addition. At the end of the addition, the mixture is left 30 minutes under stirring at room temperature, then it is heated at 135-145° C. and let under stirring for 2-2.5 hours at this temperature until the end of the reaction. The reaction mixture is cooled to a temperature lower than 3° C., then 100 ml of glacial acetic are added thereto by keeping the temperature at about 25° C. At the end of the addition, the mixture is let to stand 60 minutes under stirring at 20-25° C. and filtered. The wet product is suspended in 1900 ml of water. The suspension is heated up to 25-30° C. under stirring, its pH is adjusted to about 8 by gradual addition of 175 g of sodium bicarbonate. The solid is filtered off on Celite® by washing with hot water (40-45° C.). The pH of the mother liquors is brought to 1.5 by addition of about 125 ml of 37% hydrochloric acid and the obtained precipitate is filtered at 20-25° C. by washing with water until the filtrate reaches a neutral pH. Thus, 32 g of 5-carboxyphthalide with a titer (HPLC)>93% are obtained.